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   702444篇
  免费   77552篇
  国内免费   650篇
  2016年   7919篇
  2015年   11365篇
  2014年   13204篇
  2013年   18630篇
  2012年   21091篇
  2011年   21064篇
  2010年   14067篇
  2009年   12819篇
  2008年   18496篇
  2007年   19394篇
  2006年   18307篇
  2005年   17639篇
  2004年   17217篇
  2003年   16426篇
  2002年   16502篇
  2001年   31968篇
  2000年   32670篇
  1999年   25748篇
  1998年   8707篇
  1997年   9041篇
  1996年   8506篇
  1995年   8091篇
  1994年   7981篇
  1993年   7850篇
  1992年   21153篇
  1991年   20613篇
  1990年   19843篇
  1989年   19179篇
  1988年   18030篇
  1987年   17125篇
  1986年   16052篇
  1985年   16057篇
  1984年   13239篇
  1983年   11398篇
  1982年   8955篇
  1981年   8167篇
  1980年   7459篇
  1979年   12847篇
  1978年   10058篇
  1977年   9187篇
  1976年   8594篇
  1975年   9756篇
  1974年   10510篇
  1973年   10373篇
  1972年   9647篇
  1971年   8526篇
  1970年   7544篇
  1969年   7302篇
  1968年   6659篇
  1967年   5724篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Experiments were made on rabbit fed an atherogenic diet (0.5 g/kg cholesterol) singly for 15 and 24 h and repeatedly for 3, 9 and 30 days. At early stages of lipid metabolism distress the interrelationship was established between blood rheological disorders and microcirculatory abnormalities. The dependence of the initial reaction of some rheological characteristics on their initial level was marked.  相似文献   
92.
93.
94.
95.
The absence of centromeric bands in the karyotype of Felis catus is confirmed. It is also confirmed that no satellite band is visible in CsCl density gradients. However, a satellite is observed both by recentrifuging the fraction of the DNA that bands at high density in CsCl and by using netropsin to enhance the resolution of a CsCl gradient containing total F. catus DNA. The satellite, about 0.5% of total DNA, was isolated by repeated centrifugation in CsCl alone and in CsCl with netropsin. Netropsin was removed and a pure satellite DNA obtained. The reassociation kinetics (C0t1/2 less than 10(-3) M . s) show that the satellite is of the simple sequence type and hence a candidate for centromeric heterochromatin. Its cytological localisation awaits in situ hybridisation experiments.  相似文献   
96.
97.
The precipitation of tobacco mosaic virus by sodium chondroitin sulfate in an aqueous solution was investigated kinetically by means of turbidimetry. The virus solution became turbid after the addition of chondroitin sulfate. A threshold concentration of chondroitin, 1.33 mg/ml, was required for virus precipitation, irrespective of the virus concentration. The precipitation resulted from a mutual spatial exclusion phenomenon, leading to the separation of the virus as a crystalline phase. The dimension of chondroitin sulfate calculated at the threshold concentration agreed well with that obtained by other methods. The initial slopes and the aggregation half-times of the virus aggregates depended on both chondroitin and virus concentrations and the former increased with the increase in concentration of each. Above the threshold concentration of chondroitin sulfate, tobacco mosaic virus aggregation was a rapid-aggregation process and ended within 100 sec.  相似文献   
98.
99.
100.
The linkage of the Phi, Pgd, Po2, S, H and halothane sensitivity loci was followed in a Belgian Landrace family, heterozygous for these systems over 6 generations. Recombination next to the S locus occurred mainly in pigs belonging to this particular family. From this investigation the position of the S locus is proved to be outwith the Phi-Pgd region, next to Phi . Therefore the gene sequence S - Phi - Hal -H- Po2 -Pgd is proposed. Higher recombination rates were observed in the female parental line of the multiheterozygous family when compared to the male parental line. Additional data from animals, unrelated to this strain, confirm the evidence of close linkage of the S system to the nearest marker loci.  相似文献   
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