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971.
Galina Yahubyan Mariyana Gozmanova Iliya Denev Valentina Toneva Ivan Minkov 《Plant Growth Regulation》2009,57(1):49-56
The relic endemic nature of Haberlea rhodopensis, which grows in Balkan Peninsula, in combination with its high vegetative desiccation-tolerance, makes this species a good
model to study mechanisms behind plant adaptation to severe drought stress. The aim of this study was to evaluate the antioxidant
protection provided by Superoxide dismutase (SOD) and Peroxidase (PO) in H. rhodopensis after exposure to and recovery from dehydration at different developmental stages. During dehydration the electrolyte leakage
from leaf tissue increased more significantly in post-flowering plants than in flowering plants, while upon subsequent rehydration
this parameter showed a very fast decrease to the basic value of fresh leaves and did not depend on developmental stage. Like
other higher plant species, SOD and PO demonstrated in H. rhodopensis an ability to adjust their activity very promptly to changing water supply. In addition, the leaves of this resurrection
species retained significant activities of SOD and PO even in air-dried state, considered as the most severe form of water
stress. The enhanced activity of antioxidant enzymes may either enable the scavenging of the active oxygen species produced
at very severe water deficit, and/or carry a potential for resurrection on subsequent rehydration. Upon stress treatment total
activities of both enzymes were higher in flowering than post-flowering plants which reveals that developmental stage might
be a factor affecting plant stress tolerance. This work identified for the first time SOD isoforms of H. rhodopensis. Native PAGE showed at least six multiple isoforms in the protein extract from leaf tissue of flowering plants, and the differential
visualization revealed that four of them were Cu, Zn-SOD isoforms, one was Mn-SOD and one Fe-SOD. These findings provide a
good starting point for future study of the SOD gene family of this rare resurrection plant at the molecular level. 相似文献
972.
David Bryan Dail David Y. Hollinger Eric A. Davidson Ivan Fernandez Herman C. Sievering Neal A. Scott Elizabeth Gaige 《Oecologia》2009,160(3):589-599
In N-limited ecosystems, fertilization by N deposition may enhance plant growth and thus impact C sequestration. In many N
deposition–C sequestration experiments, N is added directly to the soil, bypassing canopy processes and potentially favoring
N immobilization by the soil. To understand the impact of enhanced N deposition on a low fertility unmanaged forest and better
emulate natural N deposition processes, we added 18 kg N ha−1 year−1 as dissolved NH4NO3 directly to the canopy of 21 ha of spruce-hemlock forest. In two 0.3-ha subplots, the added N was isotopically labeled as
15NH4
+ or 15NO3
− (1% final enrichment). Among ecosystem pools, we recovered 38 and 67% of the 15N added as 15NH4
+ and 15NO3
−, respectively. Of 15N recoverable in plant biomass, only 3–6% was recovered in live foliage and bole wood. Tree twigs, branches, and bark constituted
the most important plant sinks for both NO3
− and NH4
+, together accounting for 25–50% of 15N recovery for these ions, respectively. Forest floor and soil 15N retention was small compared to previous studies; the litter layer and well-humified O horizon were important sinks for
NH4
+ (9%) and NO3
− (7%). Retention by canopy elements (surfaces of branches and boles) provided a substantial sink for N that may have been
through physico-chemical processes rather than by N assimilation as indicated by poor recoveries in wood tissues. Canopy retention
of precipitation-borne N added in this particular manner may thus not become plant-available N for several years. Despite
a large canopy N retention potential in this forest, C sequestration into new wood growth as a result of the N addition was
only ~16 g C m−2 year−1 or about 10% above the current net annual C sequestration for this site. 相似文献
973.
J. Mucksová J.P. Brillard J. Hejnar M. Poplštein J. Kalina M. Bakst H. Yan P. Trefil 《Animal reproduction science》2009
Precise identification of the male germinal stem cell population is important for their practical use in programs dedicated to the integration of exogenous genetic material in testicular tissues. In the present study, our aim was to identify germinal cell populations in the testes of pubertal and adult cockerels based on the detection of the nuclear DNA content by fluorescence-activated cell sorting (FACS) and on the expression of the Dazl and Stra8 genes in single-cell suspensions of testicular tissues. Cells with a tetraploid DNA content (4c) represent a small and equal fraction of the total germinal cell population in both pubertal and adult males. In contrast, the diploid (2c) and haploid (c) subpopulations differ significantly between ages as a consequence of different degrees of sexual maturation. A specific subpopulation of testicular cells, the side-scatter subpopulation of cells, or side population (SP), was identified at the junction between the haploid and diploid cell populations. The percentage of this cell subpopulation differs significantly in pubertal and adult cockerels, accounting for 4.1% and 1.3% of the total cell population, respectively. These four testicular cell populations were also tested for the expression of Dazl and Stra8 genes known to be expressed in premeiotic cells including stem spermatogonia. Both genes were expressed in SP, whereas the expression of either Dazl or Stra8 genes was detected only in the 4c and in the 2c testicular cell subpopulations, respectively. The correlation between the cell ploidy and Dazl/Stra8 expression was the same at both male ages. We conclude that SP cells might represent a subpopulation of germinal cells enriched in stem spermatogonia, which can be of great importance for transgenesis in chicken. 相似文献
974.
Ines Batinić-Haberle Salvatore Cuzzocrea Júlio S. Rebouças Gerardo Ferrer-Sueta Emanuela Mazzon Rosanna Di Paola Rafael Radi Ivan Spasojević Ludmil Benov Daniela Salvemini 《Free radical biology & medicine》2009,46(2):192-201
MnTBAP is often referred to as an SOD mimic in numerous models of oxidative stress. We have recently reported that pure MnTBAP does not dismute superoxide, but commercial or poorly purified samples are able to perform O2·?dismutation with low-to-moderate efficacy via non-innocent Mn-containing impurities. Herein, we show that neither commercial nor pure MnTBAP could substitute for SOD enzyme in a SOD-deficient Escherichia coli model, whereas MnTE-2-PyP-treated SOD-deficient E. coli grew as well as a wild-type strain. This SOD-specific system indicates that MnTBAP does not act as an SOD mimic in vivo. In another model, carrageenan-induced pleurisy in mice, inflammation was evidenced by increased pleural fluid exudate and neutrophil infiltration and activation: these events were blocked by 0.3 mg/kg MnTE-2-PyP and, to a slightly lesser extent, by 10 mg/kg of either MnTBAP. Also, 3-nitrotyrosine formation, an indication of peroxynitrite existence in vivo, was blocked by both compounds; again MnTE-2-PyP was 33-fold more effective. Pleurisy model data indicate that MnTBAP exerts some protective actions in common with MnTE-2-PyP, which are not O2·? related and can be fully rationalized if one considers that the common biological role shared by MnTBAP and MnTE-2-PyP is related to their reduction of peroxynitrite and carbonate radical, the latter arising from ONOOCO2 adduct. The log kcat (O2·?) value for MnTBAP is estimated to be about 3.16, which is ~ 5 and ~ 6 orders of magnitude smaller than the SOD activities of the potent SOD mimic MnTE-2-PyP and Cu,Zn-SOD, respectively. This very low value indicates that MnTBAP is too inefficient at dismuting superoxide to be of any biological impact, which was confirmed in the SOD-deficient E. coli model. The peroxynitrite scavenging ability of MnTBAP, however, is only ~ 2.5 orders of magnitude smaller than that of MnTE-2-PyP and is not significantly affected by the presence of the SOD-active impurities in the commercial MnTBAP sample (log kred (ONOO?) = 5.06 for pure and 4.97 for commercial sample). The reduction of carbonate radical is equally fast with MnTBAP and MnTE-2-PyP. The dose of MnTBAP required to yield oxidative stress protection and block nitrotyrosine formation in the pleurisy model is > 1.5 orders of magnitude higher than that of MnTE-2-PyP, which could be related to the lower ability of MnTBAP to scavenge peroxynitrite. The slightly better protection observed with the commercial MnTBAP sample (relative to the pure MnTBAP) could arise from its impurities, which, by scavenging O2·?, reduce consequently the overall peroxynitrite and secondary ROS/RNS levels. These observations have profound biological repercussions as they may suggest that the effect of MnTBAP observed in numerous studies may conceivably relate to peroxynitrite scavenging. Moreover, provided that pure MnTBAP is unable to dismute superoxide at any significant extent, but is able to partially scavenge peroxynitrite and carbonate radical, this compound may prove valuable in distinguishing ONOO?/CO3·? from O2·? pathways. 相似文献
975.
Milo Luk
Martin Mrva Eva Fischer-Fodor Ivan Lacko Marin Bukovský Natalia Miklov Frantiek Ondriska Ferdinand Devínsky 《Bioorganic & medicinal chemistry letters》2009,19(22):6346-6349
A series of dialkylphosphocholines were prepared and evaluated for their biological activity. The antiprotozoal activity was determined against Acanthamoeba lugdunensis. Compound 15 exhibited excellent trophocidal activity. None of the tested dialkylphosphocholines exhibited better fungicidal activity against Candida albicans than miltefosine. The antineoplastic activity was determined against HeLa. The most cytotoxic was compound 10, which was more active against tumor cells as against normal cells. 相似文献
976.
Paramagnetic relaxation enhancements in unfolded proteins: Theory and application to drkN SH3 domain
Yi Xue Ivan S. Podkorytov D. Krishna Rao Nathan Benjamin Honglei Sun Nikolai R. Skrynnikov 《Protein science : a publication of the Protein Society》2009,18(7):1401-1424
Site‐directed spin labeling in combination with paramagnetic relaxation enhancement (PRE) measurements is one of the most promising techniques for studying unfolded proteins. Since the pioneering work of Gillespie and Shortle (J Mol Biol 1997;268:158), PRE data from unfolded proteins have been interpreted using the theory that was originally developed for rotational spin relaxation. At the same time, it can be readily recognized that the relative motion of the paramagnetic tag attached to the peptide chain and the reporter spin such as 1HN is best described as a translation. With this notion in mind, we developed a number of models for the PRE effect in unfolded proteins: (i) mutual diffusion of the two tethered spheres, (ii) mutual diffusion of the two tethered spheres subject to a harmonic potential, (iii) mutual diffusion of the two tethered spheres subject to a simulated mean‐force potential (Smoluchowski equation); (iv) explicit‐atom molecular dynamics simulation. The new models were used to predict the dependences of the PRE rates on the 1HN residue number and static magnetic field strength; the results are appreciably different from the Gillespie–Shortle model. At the same time, the Gillespie–Shortle approach is expected to be generally adequate if the goal is to reconstruct the distance distributions between 1HN spins and the paramagnetic center (provided that the characteristic correlation time is known with a reasonable accuracy). The theory has been tested by measuring the PRE rates in three spin‐labeled mutants of the drkN SH3 domain in 2M guanidinium chloride. Two modifications introduced into the measurement scheme—using a reference compound to calibrate the signals from the two samples (oxidized and reduced) and using peak volumes instead of intensities to determine the PRE rates—lead to a substantial improvement in the quality of data. The PRE data from the denatured drkN SH3 are mostly consistent with the model of moderately expanded random‐coil protein, although part of the data point toward a more compact structure (local hydrophobic cluster). At the same time, the radius of gyration reported by Choy et al. (J Mol Biol 2002;316:101) suggests that the protein is highly expanded. This seemingly contradictory evidence can be reconciled if one assumes that denatured drkN SH3 forms a conformational ensemble that is dominated by extended conformations, yet also contains compact (collapsed) species. Such behavior is apparently more complex than predicted by the model of a random‐coil protein in good solvent/poor solvent. 相似文献
977.
Bjoern Sill Ivan V. Alpatov Christina A. Pacak Douglas B. Cowan 《Journal of visualized experiments : JoVE》2009,(28)
Rodent surgery is often an important component in assessing the utility of engineered tissues. A wide variety of surgical procedures can be performed in common laboratory rats or mice and these quite frequently serve as an intermediate step between bench-top experiments and large animal testing or human trials. Given that rodents provide an established, cost-effective, and physiologically-relevant model system in which to test novel combinations of scaffolding materials and cells, they are particularly well-suited for cardiovascular tissue engineering studies. Presently, we describe an open-heart surgical procedure to implant engineered tissue containing myogenic progenitor cells in the atrioventricular (AV) groove of a rat heart. These implants are intended to create an electrical conduit between the right atrium and right ventricle with the ultimate goal of providing an alternative treatment to conventional pacemaker implantation in pediatric patients with complete heart block[1]. The engineered tissue is implanted in the AV-groove by means of a thoracotomy. For our purposes, Lewis rats are anesthetized and invasively ventilated to maintain positive airway pressure during the sterile surgical procedure. The approach to the heart is performed by a right thoracotomy through an antero-lateral incision at the 5th intercostal space. The tissue construct is fixed in the AV groove using a single 7-0 Prolene suture and positioned between the right ventricle and atrium at the ventral portion of the heart. The epicardium is partially removed to allow direct contact between the recipient myocardial cells and those contained in the engineered tissue. Following implantation, the chest wall is closed in layers, any pneumothorax is evacuated, and the animal is extubated and treated with analgesic.Download video file.(95M, mp4) 相似文献
978.
We review winner-loser models, the currently popular explanation for the occurrence of linear dominance hierarchies, via a
three-part approach. (1) We isolate the two most significant components of the mathematical formulation of three of the most
widely-cited models and rigorously evaluate the components’ predictions against data collected on hierarchy formation in groups
of hens. (2) We evaluate the experimental support in the literature for the basic assumptions contained in winner-loser models.
(3) We apply new techniques to the hen data to uncover several behavioral dynamics of hierarchy formation not previously described.
The mathematical formulations of these models do not show satisfactory agreement with the hen data, and key model assumptions
have either little or no conclusive support from experimental findings in the literature. In agreement with the latest experimental
results concerning social cognition, the new behavioral dynamics of hierarchy formation discovered in the hen data suggest
that members of groups are intensely aware both of their own interactions as well as interactions occurring among other members of their group. We suggest that
more adequate models of hierarchy formation should be based upon behavioral dynamics that reflect more sophisticated levels
of social cognition. 相似文献
979.
980.
David Grandy Jufang Shan Xinxin Zhang Sujata Rao Shailaja Akunuru Hongyan Li Yanhui Zhang Ivan Alpatov Xin A. Zhang Richard A. Lang De-Li Shi Jie J. Zheng 《The Journal of biological chemistry》2009,284(24):16256-16263
Dishevelled (Dvl) is an essential protein in the Wnt signaling pathways; it uses its PDZ domain to transduce the Wnt signals from the membrane receptor Frizzled to downstream components. Here, we report identifying a drug-like small molecule compound through structure-based ligand screening and NMR spectroscopy and show the compound to interact at low micromolar affinity with the PDZ domain of Dvl. In a Xenopus testing system, the compound could permeate the cell membrane and block the Wnt signaling pathways. In addition, the compound inhibited Wnt signaling and reduced the levels of apoptosis in the hyaloid vessels of eye. Moreover, this compound also suppressed the growth of prostate cancer PC-3 cells. These biological effects suggest that by blocking the PDZ domain of Dvl, the compound identified in our studies effectively inhibits the Wnt signaling and thus provides a useful tool for studies dissecting the Wnt signaling pathways.The Wnt signaling pathways are regulated by a family of secreted Wnt glycoproteins. The canonical Wnt pathway, which is highly conserved, is best understood. In this pathway, Wnt molecules interact with the seven-transmembrane Frizzled (Fz)2 proteins (1) by binding to an N-terminal cysteine-rich-domain (2). The signal is then transduced into the cell through an internal sequence of Fz, C-terminal to the seventh transmembrane domain, which binds directly to the PDZ (postsynaptic density-95/discs large/zonula occludens-1) domain of the cytoplasmic protein Dishevelled (Dvl) (3). Dvl then transduces the Wnt signals to downstream components (4). Three Dvl homologs (Dvl-1, -2, and -3) have been identified in humans; all are expressed in both embryonic and adult tissues, including brain, heart, lung, kidney, skeletal muscle, and others (4). Up-regulation and overexpression of Dvl proteins have been reported in many cancers, including those of breast, colon, prostate, mesothelium, and lung (non-small cell) (5–8).The Dvl protein is made up of three conserved domains: an N-terminal DIX domain, a central PDZ domain, and a C-terminal DEP domain (9). The central PDZ domain is of particular interest because of its interaction with Fz and other Wnt pathway proteins (3, 10). The direct interaction between the PDZ domain and Fz peptides is relatively weak, and other factors may play a role to ensure the communication between the two molecules (3). For example, several studies suggest that the DEP domain of Dvl has a membrane-targeting function that may facilitate PDZ-Fz interaction (11–14). However, the weak PDZ-Fz interaction provides an opportunity to block Wnt signaling at the Dvl level by using a small molecule inhibitor. An earlier study in our laboratories used an NMR-assisted virtual ligand screening approach to identify a peptide mimic that can bind to the Dvl PDZ domain (15). We have now used an improved algorithm to conduct an additional structure-based virtual screen of the PDZ domain of Dvl and have discovered a group of drug-like compounds that bind to the PDZ domain with moderate to low micromolar affinity. One of these compounds effectively blocked Wnt signaling in vivo and reduced the growth rate of a prostate cancer cell line. 相似文献