全文获取类型
收费全文 | 4078篇 |
免费 | 351篇 |
专业分类
4429篇 |
出版年
2023年 | 21篇 |
2022年 | 45篇 |
2021年 | 83篇 |
2020年 | 44篇 |
2019年 | 89篇 |
2018年 | 81篇 |
2017年 | 82篇 |
2016年 | 157篇 |
2015年 | 190篇 |
2014年 | 211篇 |
2013年 | 263篇 |
2012年 | 265篇 |
2011年 | 227篇 |
2010年 | 161篇 |
2009年 | 168篇 |
2008年 | 182篇 |
2007年 | 189篇 |
2006年 | 179篇 |
2005年 | 175篇 |
2004年 | 172篇 |
2003年 | 149篇 |
2002年 | 132篇 |
2001年 | 114篇 |
2000年 | 114篇 |
1999年 | 79篇 |
1998年 | 56篇 |
1997年 | 53篇 |
1996年 | 43篇 |
1995年 | 36篇 |
1994年 | 29篇 |
1993年 | 39篇 |
1992年 | 62篇 |
1991年 | 51篇 |
1990年 | 53篇 |
1989年 | 49篇 |
1988年 | 45篇 |
1987年 | 42篇 |
1986年 | 27篇 |
1985年 | 36篇 |
1984年 | 31篇 |
1983年 | 16篇 |
1982年 | 19篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 16篇 |
1978年 | 15篇 |
1977年 | 12篇 |
1975年 | 16篇 |
1974年 | 11篇 |
1970年 | 9篇 |
排序方式: 共有4429条查询结果,搜索用时 15 毫秒
1.
2.
M del Mar Medina-Puerta A Garrido-Pertierra 《Comparative biochemistry and physiology. B, Comparative biochemistry》1986,83(1):215-220
The enzyme 6-phosphogluconate dehydrogenase (6-phospho-D-gluconate: NADP+ oxidoreductase, decarboxylating EC 1.1.1.44) from bass liver has been purified to over 95% of homogeneity by gel filtration, affinity and ion exchange chromatographies. The apparent molecular weight was estimated by gel filtration chromatography to about 100,000. Analysis of the enzyme on sodium dodecyl sulphate polyacrylamide gel electrophoresis showed to be a dimeric protein. The effect of pH and kinetic properties were studied. 相似文献
3.
4.
H. Elenga O. Peyron R. Bonnefille D. Jolly R. Cheddadi J. Guiot V. Andrieu S. Bottema G. Buchet J.-L. De Beaulieu A. C. Hamilton J. Maley R. Marchant R. Perez-Obiol M. Reille G. Riollet L. Scott H. Straka D. Taylor E. Van Campo A. Vincens F. Laarif H. Jonson 《Journal of Biogeography》2000,27(3):621-634
Pollen data from 18,000 14C yr bp were compiled in order to reconstruct biome distributions at the last glacial maximum in southern Europe and Africa. Biome reconstructions were made using the objective biomization method applied to pollen counts using a complete list of dryland taxa wherever possible. Consistent and major differences from present‐day biomes are shown. Forest and xerophytic woods/scrub were replaced by steppe, both in the Mediterranean region and in southern Africa, except in south‐western Cape Province where fynbos (xerophytic scrub) persisted. Sites in the tropical highlands, characterized today by evergreen forest, were dominated by steppe and/or xerophytic vegetation (cf. today’s Ericaceous belt and Afroalpine grassland) at the last glacial maximum. Available data from the tropical lowlands are sparse but suggest that the modern tropical rain forest was largely replaced by tropical seasonal forest while the modern seasonal or dry forests were encroached on by savanna or steppe. Montane forest elements descended to lower elevations than today. 相似文献
5.
A Soler C García del Río L García-Torres F Vargas A Martín-Andrés C Osorio 《Revista Espanola de Fisiología》1985,41(1):107-116
The effects of changes in arterial pressure and in circulating volume on Plasma Renin Activity (PRA) in the intact rat were compared by two experimental procedures. Gradual volume depletion was induced by intraperitoneal injection of a hyperoncotic polyethyleneglycol solution (PEG) in absence of acute changes in Systolic Arterial Pressure (SAP). SAP was measured in the conscious state by the tail cuff technique. Plasma Protein Concentration (PPC) and Hematocrit (Hct) increases after PEG injection were compared as the index for measuring the Plasma Volume Reduction (PVR). PRA showed a significant (p less than 0.001) linear relationship with PPC, suggesting a direct dependence of renin secretion on volume depletion. Acute changes in the circulating volume were induced by controlled hemorrhages of 5.0, 10.0, 15.0 and 20.0 ml of blood/kg body weight. The increase in PRA showed a significant relationship with the changes in circulating volume, but it did not show any dependence on the changes in Mean Arterial Pressure (MAP). Our results suggest that, in the intact and conscious rat, renin secretion responds to the information from the cardiopulmonary volume receptors rather than to that from the high pressure receptors. 相似文献
6.
7.
Andrea Schrödel 《当今生物学》2007,37(5):289-289
8.
A rapid extraction method for screening aflatoxin producing potential ofAspergillus flavus group isolates is described. The method is performed using a moist wheat medium with ca. five infected grains extracted with 2 mL of chloroform, and using thin layer chromatography. This method was proved with 95A. flavus isolates from animal feeds. 相似文献
9.
10.