全文获取类型
收费全文 | 81622篇 |
免费 | 6733篇 |
国内免费 | 31篇 |
专业分类
88386篇 |
出版年
2022年 | 464篇 |
2021年 | 1024篇 |
2020年 | 645篇 |
2019年 | 783篇 |
2018年 | 1228篇 |
2017年 | 1186篇 |
2016年 | 1820篇 |
2015年 | 2844篇 |
2014年 | 3080篇 |
2013年 | 4211篇 |
2012年 | 5715篇 |
2011年 | 5792篇 |
2010年 | 3558篇 |
2009年 | 2992篇 |
2008年 | 4816篇 |
2007年 | 4867篇 |
2006年 | 4613篇 |
2005年 | 4482篇 |
2004年 | 4365篇 |
2003年 | 4147篇 |
2002年 | 4019篇 |
2001年 | 1555篇 |
2000年 | 1492篇 |
1999年 | 1223篇 |
1998年 | 1073篇 |
1997年 | 754篇 |
1996年 | 784篇 |
1995年 | 768篇 |
1994年 | 724篇 |
1993年 | 744篇 |
1992年 | 717篇 |
1991年 | 621篇 |
1990年 | 559篇 |
1989年 | 561篇 |
1988年 | 550篇 |
1987年 | 496篇 |
1986年 | 481篇 |
1985年 | 588篇 |
1984年 | 633篇 |
1983年 | 523篇 |
1982年 | 645篇 |
1981年 | 583篇 |
1980年 | 488篇 |
1979年 | 394篇 |
1978年 | 425篇 |
1977年 | 407篇 |
1976年 | 340篇 |
1975年 | 324篇 |
1974年 | 339篇 |
1973年 | 316篇 |
排序方式: 共有10000条查询结果,搜索用时 6 毫秒
111.
112.
113.
114.
Peter D. Taylor 《Evolution; international journal of organic evolution》1995,49(6):1119-1124
In a patch of hermaphroditic plants, with a low level of pollen migration between patches, a prevailing wind creates a gradient, within the patch, in the strength of local competition among pollen for reproductive success. This leads to a sex ratio gradient, with a male (pollen) bias in downwind individuals, which can be quite strong even for large patches. The effect can be understood as follows: downwind individuals have relatively low reproductive value and respond by putting more resources into the gamete (pollen) with the best long-range (extra-patch) reproductive success. 相似文献
115.
Ferdinand Täuber 《Folia Geobotanica》1985,20(1):1-16
The importance of endemic species for plant communities in the Roumanian Carpathians Mts. has been studied and discussed. Associations of the classAsplenietea trichomanis endemic in the South Carpathians were surveyed; they were classified into some endemic alliances (Gypsophilion petraeae, Micromerion pulegii, andSilenion lerchenfeldianae). Their locus classicus, nomenclatoric type and present distribution were also given. 相似文献
116.
117.
The presence or absence of light during flotation restricted environmental stimulation: Effects on plasma cortisol,blood pressure,and mood 总被引:1,自引:0,他引:1
John W. Turner Jr. Thomas Fine Gina Ewy Peter Sershon Thomas Freundlich 《Applied psychophysiology and biofeedback》1989,14(4):291-300
This study examined the effect of light on relaxation associated with flotation restricted environmental stimulation therapy (REST), as measured by plasma cortisol, mean arterial pressure, and psychometric parameters. Twenty-one subjects were paired by baseline cortisol levels into two groups: one experiencing flotation REST in the presence of light (REST-L) and one experiencing flotation REST in the absence of light (REST-D). Subjects were 15 male and 6 female students aged 22–28 in normal health who had not experienced REST. Repeated flotation REST (8 sessions) either with light or without light was associated with a decrease in plasma cortisol and a decrease in mean arterial pressure, with no differences in effectiveness between groups. The psychometric assessment of mood, using the POMS scale, before and after sessions 1 and 8 revealed mood state improvement in both REST-L and REST-D groups. These data suggest that the presence of light did not compromise the flotation REST experience, as evidenced by the lack of difference between REST-L and REST-D groups. 相似文献
118.
119.
120.
An extract containing solubilised receptor was passed through four columns containing Sepharose to which had been covalently coupled anti-cobalophilin IgG, vitamin B-12-intrinsic factor, vitamin B-12, and free intrinsic factor, respectively. Following a wash the receptor was eluted with EDTA, then residual Triton X-100 micelles and vitamin B-12-intrinsic factor were removed by Sephadex G-200 filtration. The receptor was purified 84 000-fold, sodium dodecyl sulphate electrophoresis indicated two subunits and gel filtration of its vitamin B-12-inttrinsic factor complex resolved it into two molecular species. 相似文献