全文获取类型
收费全文 | 319087篇 |
免费 | 32546篇 |
国内免费 | 376篇 |
出版年
2021年 | 4090篇 |
2019年 | 3745篇 |
2016年 | 3542篇 |
2015年 | 4842篇 |
2014年 | 5310篇 |
2013年 | 7978篇 |
2012年 | 8479篇 |
2011年 | 8709篇 |
2010年 | 5948篇 |
2009年 | 5667篇 |
2008年 | 7850篇 |
2007年 | 7967篇 |
2006年 | 7627篇 |
2005年 | 7338篇 |
2004年 | 8609篇 |
2003年 | 8789篇 |
2002年 | 8758篇 |
2001年 | 14058篇 |
2000年 | 13133篇 |
1999年 | 10515篇 |
1998年 | 4694篇 |
1997年 | 5126篇 |
1996年 | 4093篇 |
1995年 | 3910篇 |
1994年 | 4148篇 |
1993年 | 4125篇 |
1992年 | 8367篇 |
1991年 | 8291篇 |
1990年 | 8096篇 |
1989年 | 7854篇 |
1988年 | 7325篇 |
1987年 | 7056篇 |
1986年 | 6381篇 |
1985年 | 6685篇 |
1984年 | 5594篇 |
1983年 | 4699篇 |
1982年 | 3649篇 |
1981年 | 3438篇 |
1980年 | 3171篇 |
1979年 | 5285篇 |
1978年 | 4247篇 |
1977年 | 4107篇 |
1976年 | 3763篇 |
1975年 | 4066篇 |
1974年 | 4423篇 |
1973年 | 4327篇 |
1972年 | 4016篇 |
1971年 | 3836篇 |
1970年 | 3601篇 |
1969年 | 3224篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
21.
I report previously undocumented encounters between avian scavengers and desert bighorn sheep ( Ovis canadensis nelsoni ). These encounters are of interest because they occurred only during the nursery season when lamb mortality was high. Desert bighorn sheep responded to the presence of avian scavengers with typical anti-predator behaviours, which may indicate that avian scavengers are potential predators or that desert bighorn sheep are unable to distinguish between avian scavengers and avian predators. 相似文献
22.
23.
24.
25.
26.
Cellular and molecular physiology of volume-sensitive anion channels 总被引:39,自引:0,他引:39
Strange K.; Emma F.; Jackson P. S. 《American journal of physiology. Cell physiology》1996,270(3):C711
27.
F N Bamford 《BMJ (Clinical research ed.)》1996,313(7058):672-673
28.
Analysis of 'homes' occupied by juvenile Octopus vulgaris shows flexible behaviour which may indicate specialized intelligence and tool use. Octopuses occupied sheltered areas for a short time, average 10 days, but stayed longer in larger homes and in areas where preferred prey was available. They did not simply respond to perceptual characteristics of a site, but instead chose locations potentially suitable and modified them by removing rocks and sand and bringing in items partially to block the aperture. 相似文献
29.
M. Pons M. García A. Borell F. Garcia J. Egozcue M. A. Gorostiaga A. Delprat M. Mudry 《American journal of primatology》1995,37(4):325-331
Cytogenetic studies have been carried out in 39 specimens of C. apella of different origins. Three different morphologies, one affecting the long arm of chromosome 4 and two affecting pair 17, have been detected. In each case, they can be related by paracentric inversions. Heterochromatin polymorphisms affecting terminal or interstitial C+ regions have also been observed. The length of the terminal heterochromatic region in the long arms of chromosome 11 is variable in C. apella sp., in C. a. paraguayanus and absent in the C. a. nigritus specimens studied. Interstitial C + bands can be observed in the long arms of the biarmed chromosomes 4 and 6, and in the long arms of the acrocentric pairs 12, 13, 17, 18, 19, 20, and 21. Interstitial C + bands in the long arms of chromosomes 4, 12, 17, and 19 are present in all animals studied, although their size is variable, especially in the case of chromosomes 17 and 19. © 1995 Wiley-Liss, Inc. 相似文献