全文获取类型
收费全文 | 78047篇 |
免费 | 6692篇 |
国内免费 | 40篇 |
专业分类
84779篇 |
出版年
2022年 | 503篇 |
2021年 | 953篇 |
2020年 | 579篇 |
2019年 | 733篇 |
2018年 | 938篇 |
2017年 | 881篇 |
2016年 | 1472篇 |
2015年 | 2429篇 |
2014年 | 2765篇 |
2013年 | 3798篇 |
2012年 | 4651篇 |
2011年 | 4798篇 |
2010年 | 3158篇 |
2009年 | 2848篇 |
2008年 | 4235篇 |
2007年 | 4364篇 |
2006年 | 4146篇 |
2005年 | 4137篇 |
2004年 | 4226篇 |
2003年 | 3819篇 |
2002年 | 3817篇 |
2001年 | 903篇 |
2000年 | 649篇 |
1999年 | 921篇 |
1998年 | 1211篇 |
1997年 | 871篇 |
1996年 | 803篇 |
1995年 | 780篇 |
1994年 | 751篇 |
1993年 | 694篇 |
1992年 | 641篇 |
1991年 | 629篇 |
1990年 | 607篇 |
1989年 | 638篇 |
1988年 | 550篇 |
1987年 | 530篇 |
1986年 | 472篇 |
1985年 | 611篇 |
1984年 | 755篇 |
1983年 | 653篇 |
1982年 | 771篇 |
1981年 | 820篇 |
1980年 | 730篇 |
1979年 | 512篇 |
1978年 | 576篇 |
1977年 | 541篇 |
1976年 | 544篇 |
1975年 | 410篇 |
1974年 | 512篇 |
1973年 | 464篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
John Llewelyn Benjamin L. Phillips Ross A. Alford Lin Schwarzkopf Richard Shine 《Oecologia》2010,162(2):343-348
Cane toads (Bufo marinus) are now moving about 5 times faster through tropical Australia than they did a half-century ago, during the early phases of toad invasion. Radio-tracking has revealed higher daily rates of displacement by toads at the invasion front compared to those from long-colonised areas: toads from frontal populations follow straighter paths, move more often, and move further per displacement than do toads from older (long-established) populations. Are these higher movement rates of invasion-front toads associated with modified locomotor performance (e.g. speed, endurance)? In an outdoor raceway, toads collected from the invasion front had similar speeds, but threefold greater endurance, compared to conspecifics collected from a long-established population. Thus, increased daily displacement in invasion-front toads does not appear to be driven by changes in locomotor speed. Instead, increased dispersal is associated with higher endurance, suggesting that invasion-front toads tend to spend more time moving than do their less dispersive conspecifics. Whether this increased endurance is a cause or consequence of behavioural shifts associated with rapid dispersal is unclear. Nonetheless, shifts in endurance between frontal and core populations of this invasive species point to the complex panoply of traits affected by selection for increased dispersal ability on expanding population fronts. 相似文献
62.
63.
Ruth Duncan Pavla Rejmanova Jindrich Kopeček John B. Lloyd 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,678(1):143-150
Synthetic 125I-labelled N-(2-hydroxypropyl)methacrylamide copolymers containing four different, potentially degradable peptidyl side chains were incubated with rat visceral yolk sacs cultured in vitro. All copolymers were captured by fluid-phase pinocytosis and three of the side chains were susceptible to lysosomal hydrolysis, resulting in release of [125I]iodotyrosine back into the culture medium. Uptake and degradation was completely inhibited by 2,4-dinitrophenol. The thiol-proteinase inhibitor leupeptin did not affect the rate of pinocytosis, but caused different degrees of inhibition of hydrolysis depending on side chain composition. 相似文献
64.
John P. Alao Pim J. Huis in 't Veld Frederike Buhse Per Sunnerhagen 《Molecular microbiology》2010,77(1):143-157
The DNA damage and stress response pathways interact to regulate cellular responses to genotoxins and environmental stresses. How these pathways interact in Schizosaccharomyces pombe is not well understood. We demonstrate that osmotic stress suppresses the DNA damage sensitivity of checkpoint mutants, and that this occurs through three distinct cell cycle delays. A delay in G2/M is dependent on Srk1. Progression through mitosis is halted by the Mad2‐dependent spindle checkpoint. Finally, cytokinesis is impaired by modulating Cdc25 expression. These three delays, imposed by osmotic stress, together compensate for the loss of checkpoint signalling. 相似文献
65.
66.
67.
68.
Charles E. Wenner John C. Cheney L. David Tomei 《Journal of cellular biochemistry》1981,15(2):161-168
The introduction of either PGF2α (10?7 M) or TPA (10?7 M) stimulated, ouabain-sensitive 86Rb+ influx at 30 min in postconfluent 3T3-4 mouse fibroblast cultures by 117% and 124%, respectively. Both TPA and PGF2α at these concentrations stimulated the incorporation of 3H-TdR into DNA. TPA had the greatest stimulatory effect, which was similar to that obtained with 10% fetal calf serum. In accord with the idea that modulation of membrane processes such as Na+/K+ pump activity in fibroblasts may reflect important events related to the initiation of DNA synthesis, it was observed that in both 3T3-4 and C3H-1 0T½ cells there were parallel increases in 3H-TdR incorporation and ouabain-sensitive 86Rb+ influxes with 10?7 M TPA, whereas PGF2α stimulated a significant increase in 3H-TdR incorporation in 3T3-4 but not C3H-10T½ cells and only marginal increases in ouabain-sensitive 86Rb+ influx in both. Therefore, although there appears to be a close correlation between Na+/K+ pump activation and subsequent S-phase entry following TPA stimulation, a similar correlation for PGF2α cannot be confirmed. 相似文献
69.
John Warden 《BMJ (Clinical research ed.)》1986,293(6561):1583
70.