全文获取类型
收费全文 | 223963篇 |
免费 | 14975篇 |
国内免费 | 45篇 |
专业分类
238983篇 |
出版年
2021年 | 1773篇 |
2018年 | 3126篇 |
2017年 | 3023篇 |
2016年 | 3666篇 |
2015年 | 3201篇 |
2014年 | 4437篇 |
2013年 | 6321篇 |
2012年 | 7542篇 |
2011年 | 8060篇 |
2010年 | 5721篇 |
2009年 | 4876篇 |
2008年 | 7197篇 |
2007年 | 7477篇 |
2006年 | 7178篇 |
2005年 | 6704篇 |
2004年 | 6848篇 |
2003年 | 6567篇 |
2002年 | 6525篇 |
2001年 | 9274篇 |
2000年 | 8953篇 |
1999年 | 6987篇 |
1998年 | 2122篇 |
1997年 | 1953篇 |
1996年 | 1819篇 |
1992年 | 5467篇 |
1991年 | 5677篇 |
1990年 | 5650篇 |
1989年 | 5620篇 |
1988年 | 5212篇 |
1987年 | 4862篇 |
1986年 | 4442篇 |
1985年 | 4677篇 |
1984年 | 3696篇 |
1983年 | 3025篇 |
1982年 | 2013篇 |
1981年 | 1722篇 |
1980年 | 1725篇 |
1979年 | 3338篇 |
1978年 | 2576篇 |
1977年 | 2375篇 |
1976年 | 2330篇 |
1975年 | 2826篇 |
1974年 | 3117篇 |
1973年 | 3084篇 |
1972年 | 2746篇 |
1971年 | 2604篇 |
1970年 | 2212篇 |
1969年 | 2158篇 |
1968年 | 2031篇 |
1967年 | 1797篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
With the help of a suction manometric device, the relation between the deformation of Xenonus laevis embryo at the gastrula and neurula stages and the value of the applied force has been studied. Stiffness modules of embryonic
tissues were in the order of several dozens of Pascal and they were inversely proportional during deformation from 40 to 20%.
At the gastrula stage, a uniform or an increasing rate of expansion of the embryo body in the suction capillary with the diameter
of approximately half that of the embryo was observed for 30 min after the action of the suction forces. The length of the
stretched portion of the embryo correlates with the value of its deformation at the first minute. As a result of the expansion,
the total body surface area of the deformed embryo increases more than twice compared to intact embryos. After expelling the
embryo from the capillary, its surface reduced and the deformation became smoothened within 5 min, which indicates the existence
of tensional force in the expanded embryo. These data confirm that, at the embryo gastrula stage, external mechanical forces
do not only passively deform the embryo but also initiate the active expansion of the embryo which takes place at zero external
force and overcomes the tensional resistance of tissues. The mechanism of active expansion and its link with the processes
of normal morphogenesis are discussed. 相似文献
152.
153.
154.
N. G. Morozova M. A. Maslov V. V. Myagchenkov G. A. Serebrennikova 《Russian Journal of Bioorganic Chemistry》2010,36(5):657-662
An approach to the synthesis of cationic carbohydrate surfactants with potential antimicrobial and transfecting activities
is proposed. 相似文献
155.
156.
157.
158.
The [3H]ketanserin binding characteristics in the apomorphine-induced aggressive and nonaggressive adult male Wistar rats were studied. Repeated apomorphine (0.5 mg/kg, once daily) treatment gradually induced aggressive behaviour in sixteen animals from twenty. Thereafter the animals were retrospectively divided into apomorphine-induced aggressive and nonaggressive group. The maximal number of the [3H]ketanserin binding sites was increased in the apomorphine-treated animals in the frontal (233.9+/-26.5, 364.6+/-31.7, and 367.0+/-34.8 fmol/mg protein for the vehicle, apomorphine-nonaggressive, and apomorphine-aggressive group, respectively) and cerebral cortex (164.2+/-6.7, 289.7+/-29.3, and 249.0+/-15.4 fmol/mg protein for the vehicle, apomorphine-nonaggressive, and apomorphine-aggressive group, respectively). In conclusion, our experiments demonstrate that repeated apomorphine treatment upregulates the maximal number of the 5-HT2A receptors in rat frontal and cerebral cortex as measured by [3H]ketanserin binding and this phenomenon is independent from the development of aggressive behaviour. 相似文献
159.
160.