全文获取类型
收费全文 | 61174篇 |
免费 | 17956篇 |
国内免费 | 3851篇 |
出版年
2024年 | 75篇 |
2023年 | 487篇 |
2022年 | 875篇 |
2021年 | 2182篇 |
2020年 | 3384篇 |
2019年 | 5118篇 |
2018年 | 5141篇 |
2017年 | 5054篇 |
2016年 | 5465篇 |
2015年 | 6084篇 |
2014年 | 6268篇 |
2013年 | 6765篇 |
2012年 | 5146篇 |
2011年 | 4544篇 |
2010年 | 4891篇 |
2009年 | 3494篇 |
2008年 | 2634篇 |
2007年 | 2028篇 |
2006年 | 1800篇 |
2005年 | 1668篇 |
2004年 | 1483篇 |
2003年 | 1491篇 |
2002年 | 1322篇 |
2001年 | 1003篇 |
2000年 | 820篇 |
1999年 | 675篇 |
1998年 | 402篇 |
1997年 | 293篇 |
1996年 | 303篇 |
1995年 | 265篇 |
1994年 | 237篇 |
1993年 | 175篇 |
1992年 | 205篇 |
1991年 | 176篇 |
1990年 | 161篇 |
1989年 | 123篇 |
1988年 | 104篇 |
1987年 | 90篇 |
1986年 | 84篇 |
1985年 | 85篇 |
1984年 | 49篇 |
1983年 | 38篇 |
1982年 | 39篇 |
1981年 | 27篇 |
1980年 | 19篇 |
1979年 | 22篇 |
1977年 | 17篇 |
1974年 | 16篇 |
1972年 | 17篇 |
1971年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
61.
Protection of iron-catalysed the radical damage to DNA and lipids by copper (II) bleomycin 总被引:3,自引:0,他引:3
J M Gutteridge F Xiao Change 《Biochemical and biophysical research communications》1981,99(4):1354-1360
The ability of Copper(II)-bleomycin to inhibit oxygen-free-radical damage to biomolecules has been assessed. This copper complex showed inhibitory properties towards iron-catalysed damage to phospholipid membranes and cell-free DNA. It was also able to prevent superoxide-dependent reduction of nitroblue tetrazolium (NBT). Unlike iron, copper-bleomycin does not damage DNA . This may result from a site-specific dismutation of superoxide radicals on the DNA molecule. 相似文献
62.
63.
P. Cruz C. H. Mejia‐Ruiz R. Perez‐Enriquez A. M. Ibarra 《Molecular ecology resources》2002,2(3):239-241
Five polymorphic microsatellite loci were characterized for Penaeus (Litopenaeus) vannamei. Loci were isolated using a partial Sau3A1 genomic library by the sequencing of randomly selected clones and by a biotinylated (CT)10 and (GT)10 probes screening procedure. The last strategy resulted in the most useful data. About 40% of the clones showed a previously reported satellite/microsatellite (PVS1), reducing the chance of finding new microsatellite regions. Whereas two of the microsatellite loci with more than 10 alleles will be useful for mating analysis in a breeding program, the others might prove useful for population genetic studies. 相似文献
64.
65.
Jian Xiao Dan Chen Xiu-Xian Lin Shi-Fang Peng Mei-Fang Xiao Wei-Hua Huang Yi-Cheng Wang Jing-Bo Peng Wei Zhang Dong-Sheng Ouyang Yao Chen 《PloS one》2016,11(2)
Ginsenoside compound K (CK), a rare ginsenoside originating from Panax Ginseng, has been found to possess unique pharmacological activities specifically as anti-cancers. However, the role of cytochrome P450s (CYPs) in the metabolism of CK is unclear. In this study, we screened the CYPs for the metabolism of CK in vitro using human liver microsomes (HLMs) or human recombinant CYPs. The results showed that CK inhibited the enzyme activities of CYP2C9 and CYP3A4 in the HLMs. The Km and Vmax values of CK were 84.20±21.92 μM and 0.28±0.04 nmol/mg protein/min, respectively, for the HLMs; 34.63±10.48 μM and 0.45±0.05 nmol/nmol P450/min, respectively, for CYP2C9; and 27.03±5.04 μM and 0.68±0.04 nmol/nmol P450/min, respectively, for CYP3A4. The IC50 values were 16.00 μM and 9.83 μM, and Ki values were 14.92 μM and 11.42μM for CYP2C9 and CYP3A4, respectively. Other human CYP isoforms, including CYP1A2, CYP2A6, CYP2D6, CYP2E1, and CYP2C19, showed minimal or no effect on CK metabolism. The results suggested that CK was a substrate and also inhibitors for both CYP2C9 and CYP3A4. Patients using CK in combination with therapeutic drugs that are substrates of CYP2C9 and CYP3A4 for different reasons should be careful, although the inhibiting potency of CK is much poorer than that of enzyme-specific inhibitors. 相似文献
66.
67.
68.
69.
70.
T. Phanitchat C. Apiwathnasorn S. Sungvornyothin Y. Samung S. Dujardin J.‐P. Dujardin S. Sumruayphol 《Medical and veterinary entomology》2019,33(4):476-484
Wing geometry helps to identify mosquito species, even cryptic ones. On the other hand, temperature has a well‐known effect on insect metric properties. Can such effects blur the taxonomic signal embedded in the wing? Two strains of Aedes albopictus (laboratory and field strain) were examined under three different rearing temperatures (26, 30 and 33 °C) using landmark‐ and outline‐based morphometric approaches. The wings of each experimental line were compared with Aedes aegypti. Both approaches indicated similar associations between wing size and temperature. For the laboratory strain, the wing size significantly decreased as the temperature increased. For the field strain, the largest wings were observed at the intermediate temperature. The two morphometric approaches describing shape showed different sensibilities to temperature. For both strains and sexes, the landmark‐based approach disclosed significant wing shape changes with temperature changes. The outline‐based approach showed lesser effects, detecting significant changes only in laboratory females and in field males. Despite the size and shape changes induced by temperature, the two strains of Ae. albopictus were always distinguished from Ae. aegypti. The present study confirms the lability of size. However, it also suggests that, despite environmentally‐induced variation, the architecture of the wing still provides a strong taxonomic signal. 相似文献