全文获取类型
收费全文 | 21280篇 |
免费 | 1353篇 |
国内免费 | 1055篇 |
出版年
2023年 | 266篇 |
2022年 | 370篇 |
2021年 | 459篇 |
2020年 | 511篇 |
2019年 | 733篇 |
2018年 | 727篇 |
2017年 | 575篇 |
2016年 | 554篇 |
2015年 | 566篇 |
2014年 | 1158篇 |
2013年 | 1545篇 |
2012年 | 800篇 |
2011年 | 1143篇 |
2010年 | 882篇 |
2009年 | 1051篇 |
2008年 | 1022篇 |
2007年 | 979篇 |
2006年 | 947篇 |
2005年 | 860篇 |
2004年 | 764篇 |
2003年 | 693篇 |
2002年 | 626篇 |
2001年 | 346篇 |
2000年 | 323篇 |
1999年 | 354篇 |
1998年 | 369篇 |
1997年 | 320篇 |
1996年 | 270篇 |
1995年 | 295篇 |
1994年 | 247篇 |
1993年 | 220篇 |
1992年 | 226篇 |
1991年 | 175篇 |
1990年 | 171篇 |
1989年 | 153篇 |
1988年 | 127篇 |
1987年 | 131篇 |
1986年 | 118篇 |
1985年 | 206篇 |
1984年 | 318篇 |
1983年 | 299篇 |
1982年 | 277篇 |
1981年 | 260篇 |
1980年 | 248篇 |
1979年 | 209篇 |
1978年 | 167篇 |
1977年 | 150篇 |
1976年 | 123篇 |
1975年 | 116篇 |
1974年 | 101篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
《Molecular cell》2021,81(17):3650-3658.e5
- Download : Download high-res image (183KB)
- Download : Download full-size image
44.
《Bioorganic & medicinal chemistry letters》2014,24(6):1523-1527
The non-receptor tyrosine kinase Syk (spleen tyrosine kinase) is a pharmaceutical relevant target because its over-activation is observed in several autoimmune diseases, allergy, and asthma. Here we report the identification of two novel inhibitors of Syk by high-throughput docking into a rare C-helix-out conformation published recently. Interestingly, both compounds are slightly more active on ZAP70 (Zeta-chain-associated protein kinase 70), which is the kinase closest to Syk in the phylogenetic tree of human kinases. Taken together, the docking pose and experimental results suggest that the higher affinity of the inhibitors for ZAP70 than Syk originates from a more populated C-helix-out conformation in ZAP70. The latter observation is congruent with the 100-fold lower intrinsic activity of ZAP70 than Syk, as the C-helix-out conformation is inactive. The pharmacophore features of DFG-in, C-helix-out compounds are analyzed in relation to DFG-out inhibitors. 相似文献
45.
46.
Caixia Hou Abhisek Mandal Jürgen Rohr Oleg V. Tsodikov 《Structure (London, England : 1993)》2021,29(5):404-412.e4
- Download : Download high-res image (237KB)
- Download : Download full-size image
47.
《Bioorganic & medicinal chemistry letters》2014,24(16):3683-3689
Bacterial resistance is inevitable and is a growing concern. It can be addressed only by discovery and development of new agents. However the discovery and development of new antibacterial agents are at an all time low. This article broadly examines the historical as well as current status of antibacterial discovery and provides some perspective as how to address some of the challenges. 相似文献
48.
《Saudi Journal of Biological Sciences》2022,29(5):3918-3928
Rice is the most important crop for the majority of population across the world with sensitive behavior toward heavy metals such as chromium (Cr) in polluted regions. Although, there is no information on the Cr resistance phenotyping in rice. Herein, two different groups of rice cultivars (normal, and hybrid) were used, each group with 14 different rice cultivars. Firstly, seed germination analysis was conducted by evaluating various seed germination indices to identify the rice cultivars with greatest seed germination vigor. Furthermore, exposure of chromium (Cr) toxicity to 28 different rice varieties (NV1-NV14, HV1-HV14) caused noticeable plant biomass reduction. Subsequently, NV2, NV6, NV10, NV12, NV13 (normal type), HV1, HV4, HV8, and HV9 (hybrid types) were pragmatic as moderately sensitive varieties, while NV3, NV4, NV9, and NV14 (normal type), HV3, HV6, HV7, and HV13 were observed as moderately tolerant. Although, NV7, and HV10 were ranked most sensitive cultivars, and NV11, and HV14 were considered as most tolerant varieties as compared to the other rice (both groups) genotypes. Afterward, Cr induced reduction in chlorophyll pigments were significantly lesser in HV14 relative to NV11, NV7, and especially HV10, and as a result HV14 modulated the total soluble sugar level as well as reduced ROS accumulation, and MDA contents production by stimulating the antioxidant defense mechanism conspicuously which further reduced the electrolyte leakage as well. Our outcomes provide support to explore the Cr tolerance mechanism in cereal crops as well as knowledge about rice breeding with increased tolerance against Cr stress. 相似文献
49.
A field experiment encompassing both neighbour- and nutrient-manipulations was conducted in a nutrient-impoverished old-field habitat to investigate how the intensity of plant competition was affected by soil nutrient level. Three perennial grasses were used as target species: Agropyron repens, Poa pratensis and Phleum pratense. Neighbour manipulations involved the removal (through herbicide application) of all neighbouring vegetation within a 20 cm or 40 cm radius around target plants. Target performance was measured under five levels of added nutrients (N-P-K) in both the neighbour-removal plots and in non-removal (control) plots. Both neighbour and nutrient manipulations had a highly significant effect on both biomass and tiller production but the interaction between these treatments was generally insignificant. Below-ground/above-ground biomass quotient was affected only by neighbour manipulations and was greatest in the control plots (with no neighbours removed) for all three species. The suppressive effect of neighbours was not markedly affected by nutrient level. However, yield suppression showed a significant decreasing trend with increasing nutrient level for biomass production in Agropyron and an increasing trend for tiller production in Phleum. For Poa, there was no trend in the intensity of competition across nutrient level. The results suggest that the general intensity of competition within this community neither increases nor decreases with increasing nutrient level. Rather, coexisting species appear to respond individually in terms of the intensity of competition that they experience. These results conflict with predictions from the triangular C-S-R model of plant strategies. However, they are consistent with a recently modified ‘habitat templet’ model for vegetation. 相似文献
50.