全文获取类型
收费全文 | 58400篇 |
免费 | 4198篇 |
国内免费 | 264篇 |
专业分类
62862篇 |
出版年
2022年 | 2255篇 |
2021年 | 2821篇 |
2020年 | 2250篇 |
2019年 | 2548篇 |
2018年 | 1005篇 |
2017年 | 743篇 |
2016年 | 703篇 |
2015年 | 823篇 |
2014年 | 739篇 |
2013年 | 920篇 |
2012年 | 896篇 |
2011年 | 891篇 |
2010年 | 781篇 |
2009年 | 976篇 |
2008年 | 739篇 |
2007年 | 747篇 |
2006年 | 695篇 |
2005年 | 649篇 |
2004年 | 2107篇 |
2003年 | 2555篇 |
2002年 | 2773篇 |
2001年 | 3719篇 |
2000年 | 2484篇 |
1999年 | 2094篇 |
1998年 | 1739篇 |
1997年 | 2046篇 |
1996年 | 945篇 |
1995年 | 997篇 |
1994年 | 1306篇 |
1993年 | 1245篇 |
1992年 | 941篇 |
1991年 | 800篇 |
1990年 | 936篇 |
1989年 | 637篇 |
1988年 | 713篇 |
1987年 | 637篇 |
1986年 | 556篇 |
1985年 | 648篇 |
1984年 | 577篇 |
1983年 | 495篇 |
1982年 | 351篇 |
1981年 | 357篇 |
1979年 | 410篇 |
1978年 | 510篇 |
1977年 | 455篇 |
1976年 | 397篇 |
1975年 | 361篇 |
1972年 | 448篇 |
1971年 | 513篇 |
1970年 | 621篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
HIF-1 expression in healing wounds: HIF-1alpha induction in primary inflammatory cells by TNF-alpha 总被引:12,自引:0,他引:12
2.
Patterns of Sleeping Site and Sleeping Tree Selection by Black-and-Gold Howler Monkeys (Alouatta caraya) in Northern Argentina 总被引:1,自引:0,他引:1
Brividoro Melina V. Kowalewski Martin M. Scarry Clara J. Oklander Luciana I. 《International journal of primatology》2019,40(3):374-392
International Journal of Primatology - The selection of sleeping sites and sleeping trees in nonhuman primates is related to social and ecological factors. We investigate the role of body... 相似文献
3.
ABSTRACT The phrase persistent vulnerability reflects the enduring relationship of the rural population in Ceará with a highly variable climate. Persistence underscores the historical and unyielding nature of this vulnerability. Yet contrary to once-catastrophic rates of mortality etched in a public consciousness, no one dies from severe droughts and few people flee them as in the past. Government relief and social transfers have become the institutionalized form of adaptation, giving way to the counterintuitive reality that drought stabilizes the food and income supply for poor people. We analyze how maladaptive risk reduction, which is embedded in clientilistic social relations, undermines resilience, and we examine pathways toward a more sustainable adaptive relationship. 相似文献
4.
5.
The reaction of oxygen with hemoglobin and the kinetic basis of the effect of salt on binding of oxygen 总被引:7,自引:0,他引:7
Q H Gibson 《The Journal of biological chemistry》1970,245(13):3285-3288
6.
7.
8.
Bugreev D. V. Sinitsyna O. I. Buneva V. N. Nevinsky G. A. 《Russian Journal of Bioorganic Chemistry》2003,29(3):249-261
Data on the interaction of DNA type I topoisomerases from the murine and human placenta cells with specific and nonspecific oligonucleotides of various structures and lengths are summarized. The relative contributions of various contacts between the enzymes and DNA that have previously been detected by X-ray analysis to the total affinity of the topoisomerases for DNA substrates are estimated. Factors that determine the differences in the enzyme interactions with specific and nonspecific single- and double-stranded DNAs are revealed. The results of the X-ray analysis of human DNA topoisomerase I are interpreted taking into account data on the comprehensive thermodynamic and kinetic analysis of the enzyme interaction with the specific and nonspecific DNAs. 相似文献
9.
10.
We released seeds of two sympatric tree species, Corylus mandshurica (seed with thinner seed hull, higher nutrition) and C. heterophylla (seeds with thicker seed hull, lower nutrition) in the masting year of C. mandshurica in 2008, and C. heterophylla in 2009, respectively, to investigate how seed masting of the two sympatric Corylus species affects seed removal and dispersal fitness of the two species differently at both intra- and inter-specific levels.
At intra-specific level, the authors found mast seeding of both C. mandshurica and C. heterophylla significantly reduced seed removal, seed consumption, but increased seed dispersal distance and seed dispersal fitness of
the released seeds. Mast seeding of C. mandshurica increased seed caching of C. mandshurica. At inter-specific level, the authors found mast seeding of C. mandshurica reduced seed removal of C. heterophylla, but mast seeding of C. heterophylla did not significantly reduce seed removal of C. mandshurica. Mast seeding of C. mandshurica reduced seed consumption of C. heterophylla, while mast seeding of C. heterophylla reduced seed consumption of C. mandshurica. We found mast seeding of C. mandshurica significantly reduced seed dispersal distance of C. heterophylla, while mast seeding of C. heterophylla significantly increased seed dispersal distance of C. mandshurica. We found that mast seeding of C. mandshurica significantly increased seed dispersal fitness of C. heterophylla, while mast seeding of C. heterophylla did not significantly increase seed dispersal fitness of C. mandshurica. More studies are needed to reveal the ecological consequences of mast seeding at inter-specific or community-level. Seed
traits may attribute the differences of mast seeding at inter-specific level. Because seeds with thinner seed hull and higher
nutrition were more harvested and eaten by rodents, mast seeding of C. mandshurica might have reduced seed removal and seed consumption, but increased dispersal fitness of C. heterophylla (seeds with thicker seed hull, lower nutrition). Therefore, synchrony among species is, or is not, selectively beneficial
to the focus species depends on seed traits which determine gains from mast seeding at inter-specific level. 相似文献