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71.
Dalia Berenice Borbón-Palomares Flora Laborin-Sivirian Clara Tinoco-Ojanguren M. Cristina Peñalba Ivonne Reyes-Ortega Francisco Molina-Freaner 《Plant Ecology》2018,219(8):927-939
Agave colorata is a paniculate agave distributed along the migratory route of the nectar-feeding bat Leptonycteris yerbabuenae. In this paper, we evaluate the importance of nectar-feeding bats in the reproduction of A. colorata in a population in Sonora, Mexico, and describe the germination consequences of self-pollination. We estimated abundance using five plots and set pollination treatments to evaluate the importance of bats. We recorded 14.8?±?6.8 plants/400 m2, with a bimodal size distribution. Flowers are protandrous and visited mainly (>?20 visits/plant/30 min) by L. yerbabuenae. Pollination exclusion experiments showed that flowers excluded from diurnal visitors had maximum fruit set values (0.49?±?0.42), while the autonomous self-pollination treatment had the lowest value (0.03?±?0.06). Similarly, the greatest number of viable seeds per fruit was recorded in the diurnal exclusion treatment, while the greatest number of empty seeds was observed in the self-pollination treatment. Fruit set values among untreated plants varied from 32 to 54%, with a mean value of 41.8%. Seeds derived from self-pollination had a narrower window of opportunity for germination compared to seeds derived from nocturnal pollination. Self-pollinated seeds had lower germination, rate of germination or lag time in response to light, osmotic potential and heat shock treatments, compared to other pollination treatments, revealing an inbreeding cost. Overall, our results show that L. yerbabuenae is the likely major pollinator of the studied A. colorata population. However, under pollinator limitation A. colorata may produce seeds by autonomous self-pollination, at a cost expressed as lower germination. 相似文献
72.
Sarah Kircher Maylin Merino-Wong Barbara A. Niemeyer Dalia Alansary 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》2018,1865(6):932-943
Differentiation of naïve CD4+ T cells into effector subtypes with distinct cytokine profiles and physiological roles is a tightly regulated process, the imbalance of which can lead to an inadequate immune response or autoimmune disease. The crucial role of Ca2+ signals, mainly mediated by the store operated Ca2+ entry (SOCE) in shaping the immune response is well described. However, it is unclear if human effector CD4+ T cell subsets show differential Ca2+ signatures in response to different stimulation methods. Herein, we provide optimized in vitro culture conditions for polarization of human CD4+ effector T cells and characterize their SOCE following both pharmacological store depletion and direct T-cell receptor (TCR) activation. Moreover, we measured whole cell Ca2+ release activated Ca2+ currents (ICRAC) and investigated whether the observed differences correlate to the expression of CRAC genes. Our results show that Ca2+ profiles of helper CD4+ Th1, Th2 and Th17 are distinct and in part shaped by the intensity of stimulation. Regulatory T cells (Treg) are unique being the subtype with the most prominent SOCE response. Analysis of in vivo differentiated Treg unraveled the role of differential expression of ORAI2 in fine-tuning signals in Treg vs. conventional CD4+ T cells. 相似文献
73.
Alain Hamon Nicolas Gilles Pierre Sautière Arlette Martinage Charles Kopeyan Chris Ulens Jan Tytgat Jean-Marc Lancelin Dalia Gordon 《European journal of biochemistry》2002,269(16):3920-3933
Two novel toxins, Lqh6 and Lqh7, isolated from the venom of the scorpion Leiurus quinquestriatus hebraeus, have in their sequence a molecular signature (8Q/KPE10) associated with a recently defined group of alpha-toxins that target Na channels, namely the alpha-like toxins [reviewed in Gordon, D., Savarin, P., Gurevitz, M. & Zinn-Justin, S. (1998) J. Toxicol. Toxin Rev. 17, 131-159]. Lqh6 and Lqh7 are highly toxic to insects and mice, and inhibit the binding of alpha-toxins to cockroach neuronal membranes. Although they kill rodents by intracerebroventricular injection, they do not inhibit the binding of antimammal alpha-toxins (e.g. Lqh2) to rat brain synaptosomes, not even at high concentrations. Furthermore, in voltage-clamp experiments, rat brain Na channels IIA (rNav1.2A) expressed in Xenopus oocytes are not affected by Lqh6 nor by Lqh7 below 3 micro m. In contrast, muscular Na channels (rNav1.4 and hNav1.5) expressed in the same cells respond to nanomolar concentrations of Lqh6 and Lqh7 by slowing of Na current inactivation and a leftward shift of the peak conductance-voltage curve. The structural and pharmacological properties of the new toxins are compared to those of other scorpion alpha-toxins in order to re-examine the hallmarks previously set for the alpha-like toxin group. 相似文献
74.
75.
Dalia Rokhsana Tao A. G. Large Morgan C. Dienst Marius Retegan Frank Neese 《Journal of biological inorganic chemistry》2016,21(4):491-499
CO dehydrogenase (CODH) is an environmentally crucial bacterial enzyme that oxidizes CO to CO2 at a Mo–Cu active site. Despite the close to atomic resolution structure (1.1 Å), significant uncertainties have remained with regard to the protonation state of the water-derived equatorial ligand coordinated at the Mo-center, as well as the nature of intermediates formed during the catalytic cycle. To address the protonation state of the equatorial ligand, we have developed a realistic in silico QM model (~179 atoms) containing structurally essential residues surrounding the active site. Using our QM model, we examined each plausible combination of redox states (MoVI–CuI, MoV–CuII, MoV–CuI, and MoIV–CuI) and Mo-coordinated equatorial ligands (O2?, OH?, H2O), as well as the effects of second-sphere residues surrounding the active site. Herein, we present a refined computational model for the Mo(VI) state in which Glu763 acts as an active site base, leading to a MoO2-like core and a protonated Glu763. Calculated structural and spectroscopic data (hyperfine couplings) are in support of a MoO2-like core in agreement with XRD data. The calculated two-electron reduction potential (E = ?467 mV vs. SHE) is in reasonable agreement with the experimental value (E = ?558 mV vs. SHE) for the redox couple comprising an equatorial oxo ligand and protonated Glu763 in the MoVI–CuI state and an equatorial water in the MoIV–CuI state. We also suggest a potential role of second-sphere residues (e.g., Glu763, Phe390) based on geometric changes observed upon exclusion of these residues in the most plausible oxidized states. 相似文献
76.
We investigated the early effects of the anti-idiotypic antibody (clone 1D5), which recognized the estrogen receptor (ER), on cytosolic free calcium concentration ([Ca2+]i) and its long term effects on creatine kinase (CK) specific activity in female human and rat osteoblasts. These actions were compared to the known membrane and genomic effects of 17β estradiol (E2). Like E2, clone 1D5 increased within 5 s [Ca2+]i in both cell types by two mechanisms: 1) Ca2+ influx through voltage-gated Ca2+ channels as shown by using EGTA, a chelator of extracellular Ca2+, and nifedipine, a Ca2+ channel blocker; 2) Ca2+; mobilization from the endoplasmic reticulum as shown by using phospholipase C inhibitors, such as neomycin and U-73122, which involved a Pertussis toxin-sensitive G-protein. Clone 1D5 and E2 stimulated CK specific activity in human and rat osteoblasts with ten fold higher concentrations than those needed for the membrane effects (0.1 μg/ml and 10 pM, respectively). Both effects were gender-specific since testosterone and 5α-dihydotesterone were uneffective. Tamoxifen and Raloxifene, two estrogen nuclear antagonists, inhibited CK response to 1D5 and E2 and Ca2+ response to 1D5, but not CA2+ response to E2. By contrast, (Fab′)2 dimer, a proteolytic fragment of 1D5 with antagonist properties, inhibited both membrane and genomic effects of 1D5 and E2. In conclusion, these results imply that clone 1D5 has an estrogen like activity both at the membrane and nuclear levels in female human and rat osteoblasts. 1D5 must therefore interact with membrane binding sites, penetrate the cells, and reach the nuclear receptors by an as yet uncharacterized mechanism. J. Cell. Biochem. 65:53–66. © 1997 Wiley-Liss, Inc. 相似文献
77.
Eslam M. Hassanain Dalia M. M. Yacout M. A. Metwally M. S. Hassouna 《The International Journal of Life Cycle Assessment》2017,22(8):1232-1240
Purpose
The study aimed to evaluate the environmental impacts of used lubricating oil (ULO) recovery in the largest oil consumer country in Africa, Egypt. The main questions were: What are the impacts of the different waste management strategies for the recovery of used lubricating oil and which waste management strategy is more eco-friendly?Methods
Life cycle assessment (LCA) was employed to model the environmental impacts of the two waste management approaches for used lubricating oil recovery in Egypt: recycling by re-firing and recovery by co-firing. The model was applied to assess the impacts of one of the largest ULO recovery units in the Middle East and North Africa (MENA) region and the only operating unit in Egypt. The following impact categories were included: global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), carcinogens potential (CP), ecotoxicity potential (ETP), respiratory inorganic formation potential (RIFP), respiratory organic formation potential (ROFP), radiation potential (RP), ozone layer depletion (OLD), mineral depletion (MD), land use (LU) and fossil fuel depletion (FFD).Results and discussion
Results indicated that recycling by re-refining strategy is more environment-friendly. De-asphalting, de-aromatization and de-waxing processes are the main processes that affect the environmental impacts of lubricating oil production in both strategies, due to the use of hazard materials and toxic solvents in these processes. Fuel gas and fuel oil used as a fuel in the refinery and power units are the main contributors affecting the environmental impacts in case of recycling by re-refining strategy. The highest impacts were detected on FFD, followed by RIFP, GWP, AP, EP, ETP and CP in both strategies; no impacts were detected on RP, OLD and MD.Conclusions
It can be concluded that recycling by re-refining of ULO is the more eco-friendly approach. This strategy is more energy conservative, saves a diminishing fossil fuel resource and reduces burdens on the environment. ULO containing high percentages of additive remnants such as viscosity index improvers and pour point depressants which represents a valuable resource and its proper management should be given the most attention.78.
Nitrogen (N) is the key factor limiting photosynthetic processes and crop yield. Little is known about the response of leaf gas exchange of spring triticale (Triticosecale Wittm.) to N supply. The effect of N fertilizers on different gas exchange variables, i.e., photosynthetic rate (A), transpiration rate (E), stomatal conductance (g s), instantaneous water use efficiency (WUE) and maximum quantum yield of photosystem II (PSII) (F v/F m), chlorophyll index (SPAD, soil–plant analysis development), and the relationship of these variables with yield were studied in spring triticale grown under field conditions. Six treatments of N—0, 90, 180, 90 + 30, 90 + 30 + 30 kg ha?1 (applied as ammonium nitrate, AN) and one treatment of N 90 + 30 + 30 kg ha?1 (applied as urea ammonium nitrate solution, UAN) were compared. The analysis of variance showed that throughout the triticale growing season, N fertilization had significant effects on A, WUE, g s and SPAD. On average, N fertilizer application increased A values by 14–70%. E and F v/F m values were not influenced by N fertilization levels. The effect of growth stage and year on gas exchange variables and F v/F m and SPAD was found to be significant. At different growth stages, A values varied and maximum ones were reached at BBCH 31–33 (decimal code system of growth stages) and BBCH 59. With aging, values of A decreased independently of N fertilization level. The gas exchange variables were equally affected by both fertilizer forms. The interplay among grain yield, leaf gas exchange variables, F v/F m and SPAD of spring triticale was estimated. The statistical analysis showed that grain yield positively and significantly correlated with A and SPAD values throughout the growing season. 相似文献
79.
Kharat AS Denapaite D Gehre F Brückner R Vollmer W Hakenbeck R Tomasz A 《Journal of bacteriology》2008,190(17):5907-5914
The two recently characterized Streptococcus pneumoniae strains—R6Chi and R6Cho−—that have lost the unique auxotrophic requirement of this bacterial species for choline differ in their mechanisms of choline independence. In strain R6Chi the mechanism is caused by a point mutation in tacF, a gene that is part of the pneumococcal lic2 operon, which is essential for growth and survival of the bacteria. Cultures of lic2 mutants of the encapsulated strain D39Chi growing in choline-containing medium formed long chains, did not autolyze, had no choline in their cell wall, and were completely avirulent in the mouse intraperitoneal model. In contrast, while the Cho− strain carried a complete pneumococcal lic2 operon and had no mutations in the tacF gene, deletion of the entire lic2 operon had no effect on the growth or phenotype of strain Cho−. These observations suggest that the biochemical functions normally dependent on determinants of the pneumococcal lic2 operon may also be carried out in strain Cho− by a second set of genetic elements imported from Streptococcus oralis, the choline-independent streptococcal strain that served as the DNA donor in the heterologous transformation event that produced strain R6Cho−. The identification in R6Cho− of a large (20-kb) S. oralis DNA insert carrying both tacF and licD genes confirms this prediction and suggests that these heterologous elements may represent a “backup” system capable of catalyzing P-choline incorporation and export of teichoic acid chains under conditions in which the native lic2 operon is not functional. 相似文献
80.
Role of nitric oxide in D-galactosamine-induced cell death and its protection by PGE1 in cultured hepatocytes. 总被引:1,自引:0,他引:1
Emilio Siendones Dalia Fouad Amira Mohamed Kamal ElSaid Abou-Elella Ana Quintero Pilar Barrera Jordi Muntané 《Nitric oxide》2003,8(2):133-143
Prostaglandin E(1) (PGE(1)) reduces cell death in experimental and clinical manifestations of liver dysfunction. Nitric oxide (NO) has been shown to exert a protective or noxious effect in different experimental models of liver injury. The aim of the present study was to investigate the role of NO during PGE(1) protection against D-galactosamine (D-GalN) citotoxicity in cultured hepatocytes. PGE(1) was preadministered to D-GalN-treated hepatocytes. The role of NO in our system was assessed by iNOS inhibition and a NO donor. Different parameters related to apoptosis and necrosis, NO production such as nitrite+nitrate (NO(x)) release, iNOS expression, and NF-kappaB activation in hepatocytes were evaluated. The inhibition of iNOS reduced apoptosis induced by D-GalN in hepatocytes. PGE(1) protection against D-GalN injury was associated with its capacity to reduce iNOS expression and NO production induced by D-GalN. Nevertheless, iNOS inhibition showed that protection by PGE(1) was also mediated by NO. Low concentrations of a NO donor reduced D-GalN injury with a decrease in the extracellular NO(x) concentration. High concentrations of the NO donor enhanced NO(x) concentration and increased cell death by D-GalN. The present study suggests that low NO production induced by PGE(1) preadministration reduces D-GalN-induced cell death through its capacity to reduce iNOS expression and NO production caused by the hepatotoxin. 相似文献