全文获取类型
收费全文 | 460022篇 |
免费 | 56353篇 |
国内免费 | 291篇 |
专业分类
516666篇 |
出版年
2018年 | 4109篇 |
2017年 | 3739篇 |
2016年 | 5871篇 |
2015年 | 8765篇 |
2014年 | 9873篇 |
2013年 | 13632篇 |
2012年 | 15856篇 |
2011年 | 15939篇 |
2010年 | 10491篇 |
2009年 | 9599篇 |
2008年 | 13788篇 |
2007年 | 14162篇 |
2006年 | 12790篇 |
2005年 | 12556篇 |
2004年 | 12323篇 |
2003年 | 11651篇 |
2002年 | 11082篇 |
2001年 | 21877篇 |
2000年 | 21975篇 |
1999年 | 17552篇 |
1998年 | 6293篇 |
1997年 | 6532篇 |
1996年 | 6331篇 |
1995年 | 5738篇 |
1994年 | 5781篇 |
1993年 | 5590篇 |
1992年 | 13710篇 |
1991年 | 13003篇 |
1990年 | 12672篇 |
1989年 | 12530篇 |
1988年 | 11174篇 |
1987年 | 10803篇 |
1986年 | 9885篇 |
1985年 | 9664篇 |
1984年 | 8189篇 |
1983年 | 7079篇 |
1982年 | 5528篇 |
1981年 | 5010篇 |
1980年 | 4656篇 |
1979年 | 7687篇 |
1978年 | 5925篇 |
1977年 | 5428篇 |
1976年 | 5063篇 |
1975年 | 5371篇 |
1974年 | 5812篇 |
1973年 | 5656篇 |
1972年 | 5101篇 |
1971年 | 4728篇 |
1970年 | 3921篇 |
1969年 | 3852篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
871.
Growth and cell proliferation kinetics of hepatoma H-4-II-E and its tissue culture derivative have been studied to establish the characteristics of an in vivo--in vitro solid tumor model. The H-4-II-E line, originating from the Reuber H-35 hepatoma, can be maintained and studied either in cell culture or as a transplantable solid tumor in ACI male rats. In addition it allows for the in vitro assay of cell survival following treatment of animal tumors in situ. In vivo, hepatoma H-4-II-E is rapidly growing tumor with a mean doubling time of 49-2 hr. The cell cyle time is 39-1 hr with a cell loss factor of 0-32. Retrospective examination of tumor specimens obtained during the establishment of the H-4-II-E tumor system demonstrates that both structural as well as cell population changes have occurred. The biological characteristics of the primary tumor (H-35) and an early intermediate stage (H-35tc2) are compared with H-4-II-E and the histopathological, growth and cell kinetic changes are discussed. 相似文献
872.
C Fabre 《Hormones and behavior》1977,9(2):150-155
The complete behavioral repertoire of male sexual activity can be observed during daily androgen treatment (testosterone propionate, 15 mg/day) of normal ewes ovariectomized as adults. This includes the ejaculatory pattern (deep thrust accompanied by a rapid backwards movement of the head) which is followed by a dramatic decrease in the frequency of sexual interactions, similar to the male's postejaculatory reduction of activity. However, the sexual performances of the genetic females remain lower than those of normal males in ejaculation latency, postejaculation latency, and mount/ejaculation ratio. 相似文献
873.
874.
875.
876.
877.
Utilizing horseradish peroxidase as a tracer protein, it is shown that trichogen and tormogen cells have a secretory function. Protein tracer from the haemolymph enters these cells by endocytosis and is transported to the sensillum liquor cavity by transport vacuoles and multivesicular bodies. It is also suggested that closely associated pigment cells may be involved in macromolecular transport. 相似文献
878.
879.
880.
D Matthias E Engler L Will-Shahab H J Herrmann C H Becker 《Acta biologica et medica Germanica》1977,36(9):1279-1284
A 14-days' training of rats designed to adapt the animals to the procedure of blood-pressure measurement caused in the myocardium a decrease, in serum an increase in noradrenaline ( NA) content. The latter remained unchanged following 3 days of treatment with 2.5 mg depot angiotensin II (AII) but decreased by more than one-half in the myocardium of untreated animals, and increased in serum. Despite the considerable difference in myocardial NA content and blood-pressure behaviour, both trained and untrained rats showed the same morphological reactions following administration of A II. These myocardial alterations which largely correspond to the so-called epinephrine myocarditis should not therefore be due solely to NA action; rather, the involvement of A II should be considered also. 相似文献