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41.
Microtopography is one of several strategies used by marine organisms to inhibit colonization by fouling organisms. While replicates of natural microtextures discourage settlement, details of larval interactions with the structured surfaces remain scarce. Close-range microscopy was used to quantify the exploration of cyprids of Amphibalanus amphitrite on cylindrical micropillars with heights of 5 and 30 μm and diameters ranging from 5 to 100 μm. While 5 μm-high structures had little impact, 30 μm-high pillars significantly influenced cyprid exploration. An observed step length decrease and step duration increase on 5 μm diameter pillars is attributed to the small dimensions of the voids excluding the cyprid's attachment disc and consequently reducing the area of adhesive contact. When exploring larger diameter pillars, cyprids preferred using the voids to form temporary attachment points. This may enhance their resistance to flow. No-choice assay settlement patterns mirrored this exploration behaviour, albeit in a pattern counter to what was predicted. 相似文献
42.
González AL Fariña JM Pinto R Pérez C Weathers KC Armesto JJ Marquet PA 《Oecologia》2011,167(3):835-845
Carbon, nitrogen, and phosphorus (C, N, P) stoichiometry influences the growth of plants and nutrient cycling within ecosystems.
Indeed, elemental ratios are used as an index for functional differences between plants and their responses to natural or
anthropogenic variations in nutrient supply. We investigated the variation in growth and elemental content of the rootless
terrestrial bromeliad Tillandsia landbeckii, which obtains its moisture, and likely its nutrients, from coastal fogs in the Atacama Desert. We assessed (1) how fog nutrient
supply influences plant growth and stoichiometry and (2) the response of plant growth and stoichiometry to variations in nutrient
supply by using reciprocal transplants. We hypothesized that T. landbeckii should exhibit physiological and biochemical plastic responses commensurate with nutrient supply from atmospheric deposition.
In the case of the Atacama Desert, nutrient supply from fog is variable over space and time, which suggests a relatively high
variation in the growth and elemental content of atmospheric bromeliads. We found that the nutrient content of T. landbeckii showed high spatio-temporal variability, driven partially by fog nutrient deposition but also by plant growth rates. Reciprocal
transplant experiments showed that transplanted individuals converged to similar nutrient content, growth rates, and leaf
production of resident plants at each site, reflecting local nutrient availability. Although plant nutrient content did not
exactly match the relative supply of N and P, our results suggest that atmospheric nutrient supply is a dominant driver of
plant growth and stoichiometry. In fact, our results indicate that N uptake by T. landbeckii plants depends more on N supplied by fog, whereas P uptake is mainly regulated by within-plant nutrient demand for growth.
Overall, these findings indicate that variation in fog nutrient supply exerts a strong control over growth and nutrient dynamics
of atmospheric plants, which are ubiquitous across fog-dominated ecosystems. 相似文献
43.
Reduced dopamine and glutamate neurotransmission in the nucleus accumbens of quinpirole‐sensitized rats hints at inhibitory D2 autoreceptor function 下载免费PDF全文
44.
Compensatory roles of Foxa1 and Foxa2 during lung morphogenesis 总被引:16,自引:0,他引:16
Wan H Dingle S Xu Y Besnard V Kaestner KH Ang SL Wert S Stahlman MT Whitsett JA 《The Journal of biological chemistry》2005,280(14):13809-13816
45.
Qizhi Fang Pamela Y. Mok Anila E. Thomas Daniel J. Haddad Shereen A. Saini Brian T. Clifford Neel K. Kapasi Olivia M. Danforth Minako Usui Weisheng Ye Emmy Luu Rikki Sharma Maya J. Bartel Jeremy A. Pathmanabhan Andrew A. S. Ang Richard E. Sievers Randall J. Lee Matthew L. Springer 《PloS one》2013,8(4)
Pleiotrophin (PTN) is a growth factor with both pro-angiogenic and limited pro-tumorigenic activity. We evaluated the potential for PTN to be used for safe angiogenic gene therapy using the full length gene and a truncated gene variant lacking the domain implicated in tumorigenesis. Mouse myoblasts were transduced to express full length or truncated PTN (PTN or T-PTN), along with a LacZ reporter gene, and injected into mouse limb muscle and myocardium. In cultured myoblasts, PTN was expressed and secreted via the Golgi apparatus, but T-PTN was not properly secreted. Nonetheless, no evidence of uncontrolled growth was observed in cells expressing either form of PTN. PTN gene delivery to myocardium, and non-ischemic skeletal muscle, did not result in a detectable change in vascularity or function. In ischemic hindlimb at 14 days post-implantation, intramuscular injection with PTN-expressing myoblasts led to a significant increase in skin perfusion and muscle arteriole density. We conclude that (1) delivery of the full length PTN gene to muscle can be accomplished without tumorigenesis, (2) the truncated PTN gene may be difficult to use in a gene therapy context due to inefficient secretion, (3) PTN gene delivery leads to functional benefit in the mouse acute ischemic hindlimb model. 相似文献
46.
Nitrogen immobilization in fresh litter represents a significant N flux in forest ecosystems, and changes in this process resulting from atmospheric N deposition could have important implications for ecosystem responses. We conducted two leaf decay experiments, using 15N-labeled sugar maple leaf litter, to quantify N transport from old litter and soil to fresh litter during early stages of decomposition, and we examined the influence of litter N concentration and soil N availability on upward N transfer in a northern hardwood forest. After one year of decay, the average N transfer from soil to fresh litter (2.63 mg N g?1 litter) was much higher than the N transfer from older litter (1- to 2-years-old) to fresh litter (0.37 mg N g?1 litter). We calculated the ratio of annual N transfer per unit of excess 15N pool for these two N sources. The ratio was not significantly different between old litter and soil, suggesting that fungi utilize N in the old litter and mineral soil pools for transport to decaying fresh litter with similar efficiency. Initial litter N concentration had a significant effect on upward N flux into decaying leaf litter, whereas no effect of soil N fertilization was observed. Reduction in the flux from soil to fresh litter owing to anthropogenic N inputs probably contributes significantly to changing soil N dynamics. Future work is needed on fungal N acquisition and transport as well as the fungal taxa involved in this process and their responses to changing environments. 相似文献
47.
48.
The RBEs of high-energy neutrons given in 9 or 12 fractions for cervical spinal cord injury in rhesus monkeys was determined using photons at 2.2 Gy per fraction as the reference radiation. Because the dose-response functions were not parallel, the RBE was not constant but rather increased with dose or, equivalently, with the probability of myelopathy. This required the development of a novel method of determining the RBE versus level of response. The RBE is presented as a function of probability of myelopathy from 0.1 to 99%. At a 50% incidence of myelopathy, the RBE (+/- 1 SE) was 5.22 +/- 0.15. A difference in the histopathology of lesions induced by photon and neutron treatments was observed. 相似文献
49.
Protective effects of a new metalloporphyrin on paraquat-induced oxidative stress and apoptosis in N27 cells 总被引:1,自引:0,他引:1
Chen P Li A Zhang M He M Chen Z Wu X Zhao C Wang S Liang L 《Acta biochimica et biophysica Sinica》2008,40(2):125-132
Paraquat (PQ, 1,1′-dimethyl-4,4′-bipyridinium),awidely-used herbicide, has been suggested as a potential etiologic factor for the development of Parkinson's disease. In recent years, many studies have focused on the mechanism(s) of PQ neurotoxicity. In this study, we examined the neuroprotective effect of manganese (Ⅲ) meso-tetrakis (N,N′-diethylimi- dazolium) porphyrin (MnTDM), a superoxide dismutase/ catalase mimetic, on PQ-induced oxidative stress and apoptosis in 1 RB3AN27 (N27) cells, a dopaminergic neuronal cell line. The results indicated that MnTDM significantly attenuated PQ-induced loss of cell viability, glutathione depletion, and reactive oxygen species production. MnTDM also ameliorated PQ-induced morphological nuclear changes of apoptosis and increased rates of apoptosis. In addition, our data provide direct evidence that MnTDM suppressed PQ- induced caspase-3 cleavage, possibly a key event of PQ neurotoxicity. These observations suggested that oxidative stress and apoptosis are implicated in PQ-induced neurotoxicity and this toxicity could be prevented by MnTDM. These findings also proposed a novel therapeutic approach for Parkinson's disease and other disorders associated with oxidative stress. 相似文献
50.
Fernández-Torres Javier Martínez-Nava Gabriela Angélica Zamudio-Cuevas Yessica Martínez-Flores Karina Espinosa-Morales Rolando 《Molecular biology reports》2019,46(2):2049-2058
Molecular Biology Reports - Overweight produces oxidative stress (OS) on the articular cartilage, with the subsequent risk of developing knee osteoarthritis (OA). Associations between genetic... 相似文献