首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   376313篇
  免费   41077篇
  国内免费   180篇
  2018年   3495篇
  2017年   3262篇
  2016年   4478篇
  2015年   5562篇
  2014年   6689篇
  2013年   9344篇
  2012年   10491篇
  2011年   10794篇
  2010年   7347篇
  2009年   6832篇
  2008年   9705篇
  2007年   9860篇
  2006年   9582篇
  2005年   9170篇
  2004年   9023篇
  2003年   8786篇
  2002年   8464篇
  2001年   20696篇
  2000年   20753篇
  1999年   15915篇
  1998年   4744篇
  1997年   5006篇
  1996年   4624篇
  1995年   4203篇
  1994年   4176篇
  1993年   4265篇
  1992年   12432篇
  1991年   12329篇
  1990年   11855篇
  1989年   11461篇
  1988年   10692篇
  1987年   10004篇
  1986年   9106篇
  1985年   8950篇
  1984年   7112篇
  1983年   6217篇
  1982年   4423篇
  1981年   3961篇
  1980年   3742篇
  1979年   6603篇
  1978年   5088篇
  1977年   4659篇
  1976年   4173篇
  1975年   4816篇
  1974年   5073篇
  1973年   5090篇
  1972年   4480篇
  1971年   4117篇
  1970年   3656篇
  1969年   3589篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
251.
Morphological and genetic variation at microsatellite loci of Caucasian shrew Sorex satunini Ogn. is examined and compared with that of the common shrew S. araneus L. Genetic distance at microsatellite loci between the common shrew and Caucasian shrew proved to be threefold higher than between chromosome races of the common shrew. The Caucasian shrew manifested low polymorphism in studies of both microsatellites and morphometric mandibular traits. The heterozygote deficit was also typical. These properties may be a consequence of partial isolation of the population and gene drift.  相似文献   
252.
253.
Systematic procedures for calculating inbreeding coefficients   总被引:4,自引:0,他引:4  
  相似文献   
254.
The potential of nisin F as an antimicrobial agent in treating subcutaneous skin infections was tested in vivo by infecting C57BL/6 mice with a bioluminescent strain of Staphylococcus aureus (Xen 36). Strain Xen 36 has the luxABCDE operon located on a native plasmid. Mice were grouped into four groups: Infected with strain Xen 36 and treated with nisin F, infected with strain Xen 36 and treated with saline (placebo), not infected and treated with nisin (control) and not infected and not treated (control). The immune systems of the mice were suppressed with deksamethasone. Mice were treated with either nisin F or sterile physiological saline 24 and 48 h after infection with subcutaneously injected S. aureus Xen 36 (4 × 106 CFU). Histology and bioluminescent flux measurements revealed no significant difference between infected mice treated with nisin and saline, respectively. However, infected mice treated with nisin F had an increased number of polymorphonuclear cells when compared with infected mice treated with saline. Also, not infected mice treated with nisin F had an influx of polymorphonuclear cells. Nisin F is thus ineffective in combating deep dermal staphylococcal infections. The apparent immune modulation of nisin when subcutaneously injected has to be investigated.  相似文献   
255.
256.
The capillaries of the cardiac muscle were investigated in the goat by means of light microscopy, transmission electron microscopy and scanning electron microscopy, and the following results were obtained. The capillaries of the working cardiac muscles were numerous, arranged mainly parallel to the long axis of muscle cells and formed dense elongated networks. On the contrary, those of the terminal Purkinje fibers were relatively few in number, oriented in various directions and formed loose and circularly meshed networks surrounding the fibers. Such findings were discussed in correlation with the physiology and functional morphology of various types of the cardiac muscle cells.  相似文献   
257.
T S Il'ina 《Genetika》1986,22(11):2572-2582
The published data on molecular mechanisms of transposons movement inside and between genomes are reviewed. The replicative mechanism of transposition of the family of Tn3-like elements is discussed, as well as the modes of bacteriophage Mu, Tn9, Tn10, Tn903 transposition. The factors affecting the choice of transposition pathways are analysed.  相似文献   
258.
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   
259.
260.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号