全文获取类型
收费全文 | 98186篇 |
免费 | 7838篇 |
国内免费 | 34篇 |
专业分类
106058篇 |
出版年
2021年 | 851篇 |
2018年 | 1311篇 |
2017年 | 1229篇 |
2016年 | 1653篇 |
2015年 | 1764篇 |
2014年 | 2126篇 |
2013年 | 3001篇 |
2012年 | 3309篇 |
2011年 | 3405篇 |
2010年 | 2528篇 |
2009年 | 2143篇 |
2008年 | 3105篇 |
2007年 | 3058篇 |
2006年 | 2873篇 |
2005年 | 2699篇 |
2004年 | 2695篇 |
2003年 | 2585篇 |
2002年 | 2404篇 |
2001年 | 4428篇 |
2000年 | 4192篇 |
1999年 | 3247篇 |
1998年 | 1065篇 |
1997年 | 1038篇 |
1996年 | 930篇 |
1995年 | 839篇 |
1993年 | 842篇 |
1992年 | 2465篇 |
1991年 | 2475篇 |
1990年 | 2475篇 |
1989年 | 2221篇 |
1988年 | 2080篇 |
1987年 | 1992篇 |
1986年 | 1838篇 |
1985年 | 1832篇 |
1984年 | 1504篇 |
1983年 | 1310篇 |
1982年 | 932篇 |
1981年 | 879篇 |
1979年 | 1448篇 |
1978年 | 1135篇 |
1977年 | 1027篇 |
1976年 | 978篇 |
1975年 | 1167篇 |
1974年 | 1262篇 |
1973年 | 1346篇 |
1972年 | 1192篇 |
1971年 | 1049篇 |
1970年 | 933篇 |
1969年 | 959篇 |
1968年 | 837篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The perfusion procedure described in this paper produces high quality impregnation of pig visual and somatosensory cortical neurons with a Golgi-Cox solution. Starting within 30 min after death, pig heads were perfused with a fixative solution composed of a mixture (v/v) of liquid phenol, 5%; formalin, 14%; ethylene glycol, 25%; methanol, 28%; and water, 28% for two periods of 4 hr each. After perfusion, the heads were chilled for at least 18 hr. The entire brain was removed from the skull and then placed in 10% buffered formalin, where it remained for at least 10 days before taking the blocks that were to be immersed in the Golgi-Cox solution. Three weeks spent in the Golgi-Cox solution typically produced uniform neuron impregnation. The tissue blocks were then embedded in celloidin and sectioned at 120 micron. This procedure avoids the following difficulties: Golgi-Cox methods that produced excellent results with rodent or primate tissue were unsuccessful with pig tissue, placing fresh tissue in Golgi-Cox solution resulted in incomplete neuron impregnation, and immersion fixation in 10% buffered formalin without perfusion resulted in excessive staining of glia. 相似文献
92.
93.
V T Kondakov A B Okulov M A Filippkin R Z Tandilava I U Artamonov O A Voronenko A N Sazonov 《Vestnik rentgenologii i radiologii》1991,(4):31-35
The paper is concerned with analysis of the results of intraoperative phlebotesticulography, performed in 50 patients with varicocele of degree I-II during Ivanissevich's operation. The effect of surgical intervention was shown to depend upon the quality of ligation of the testicular vein, some parts of which are anastomosed between themselves. The localization of this anastomosis is revealed by means of intraoperative phlebotesticulography, which permits increasing the results of surgical treatment and predicting a course of a postoperative period. 相似文献
94.
95.
96.
97.
A method was developed to optimize simultaneous selection for a quantitative trait with a known QTL within a male and a female line to maximize crossbred performance from a two-way cross. Strategies to maximize cumulative discounted response in crossbred performance over ten generations were derived by optimizing weights in an index of a QTL and phenotype. Strategies were compared to selection on purebred phenotype. Extra responses were limited for QTL with additive and partial dominance effects, but substantial for QTL with over-dominance, for which optimal QTL selection resulted in differential selection in male and female lines to increase the frequency of heterozygotes and polygenic responses. For over-dominant QTL, maximization of crossbred performance one generation at a time resulted in similar responses as optimization across all generations and simultaneous optimal selection in a male and female line resulted in greater response than optimal selection within a single line without crossbreeding. Results show that strategic use of information on over-dominant QTL can enhance crossbred performance without crossbred testing. 相似文献
98.
Summary Responses of lentil in unsterile soils at low, medium and high levels of plant available soil P toGlomus fasciculatum inoculation were evaluated. It was observed that growth, dry matter accumulation, nodulation, and nitrogen fixation were considerably improved in VAM inoculated plants over uninoculated control at low and medium levels of plant available soil P. 相似文献
99.
100.