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   95282篇
  免费   470篇
  国内免费   862篇
  96614篇
  2022年   20篇
  2021年   37篇
  2020年   19篇
  2019年   24篇
  2018年   11864篇
  2017年   10689篇
  2016年   7496篇
  2015年   694篇
  2014年   393篇
  2013年   419篇
  2012年   4396篇
  2011年   12941篇
  2010年   12070篇
  2009年   8291篇
  2008年   9881篇
  2007年   11456篇
  2006年   372篇
  2005年   589篇
  2004年   1049篇
  2003年   1096篇
  2002年   835篇
  2001年   326篇
  2000年   217篇
  1999年   96篇
  1998年   35篇
  1997年   43篇
  1996年   21篇
  1994年   25篇
  1993年   44篇
  1992年   54篇
  1991年   75篇
  1990年   38篇
  1989年   27篇
  1988年   38篇
  1987年   33篇
  1986年   26篇
  1985年   26篇
  1984年   20篇
  1983年   36篇
  1982年   21篇
  1980年   17篇
  1979年   20篇
  1978年   18篇
  1976年   17篇
  1975年   20篇
  1973年   15篇
  1972年   259篇
  1971年   278篇
  1965年   14篇
  1962年   24篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
182.
183.
The influence of moulded hay (Alternaria alternata, Epicoccum nigrum, Mucor racemosus, Ulocladium chartarum) and the efficiency of Vitamin B1 substitution to cope these effects on rumen protozoa was investigated using the longterm rumen simulation technique (RUSITEC) for about 25 days. Moulded hay affected medium-sized protozoa to a different extent (Alternaria alternata: ?16 %, Epicoccum nigrum: ?27 %, Mucor racemosus: ?9 %, Ulocladium chartarum: +2 %). The vitamin B1 substitution had positive effects during the feeding of Mucor racemosus and Ulocladium chartarum.  相似文献   
184.
An isolated rat liver was perfused with deoxynivalenol (DON) at a dose of 3 mg in a recirculating perfusion system. To identify glucuronide conjugates equal amounts of bile samples, perfusate and liver homogenates were incubated with and without (control) a β-glucuronidase preparation and analyzed by thin layer chromatography and capillary gas liquid chromatography — chemical ionization mass spectrometry. A total of 40.4% of the administered dose of DON was found to be conjugated with glucuronic acid (perfusate 20.4%, bile 19.2%, liver 0.8%), while only 1.3% of the parent DON (perfusate 1.1%, bile 0.2%) was detected. The cleavage of DON-glucuronide was demonstrated by incubating DON-glucuronide containing bile samples with intestine contents under anaerobic conditions.  相似文献   
185.
Three-dimensional structure of the HSV1 nucleocapsid   总被引:26,自引:0,他引:26  
J D Schrag  B V Prasad  F J Rixon  W Chiu 《Cell》1989,56(4):651-660
The three-dimensional structures of full and empty capsids of HSV1 were determined by computer analysis of low dose cryo-electron images of ice embedded capsids. The full capsid structure is organized into outer, intermediate, and inner structural layers. The empty capsid structure has only one layer which is indistinguishable from the outer layer of the full capsids. This layer is arranged according to T = 16 icosahedral symmetry. The intermediate layer of full capsids appears to lie on a T = 4 icosahedral lattice. The genomic DNA is located inside the T = 4 shell and is the component of the innermost layer of the full capsids. The outer and intermediate layers interact in such a way that the channels along their icosahedral two-fold axis coincide and form a direct pathway between the DNA and the environment outside the capsid.  相似文献   
186.
Human metallothionein genes: structure of the functional locus at 16q13   总被引:21,自引:0,他引:21  
The functional human metallothionein (MT) genes are located on chromosome 16q13. We have physically mapped the functional human MT locus by isolation and restriction digest mapping of cloned DNA. The mapped region contains all sequences on chromosome 16 that hybridize to metallothionein gene probes and comprises 14 tightly linked MT genes, 6 of which have not been previously described. This analysis defines the genetic limits of metallothionein functional diversity in the human genome.  相似文献   
187.
188.
Three-dimensional structure of rotavirus   总被引:40,自引:0,他引:40  
  相似文献   
189.
Data on the individual variation and changes with growth in proportions and morphology are presented for the poorly known Apristurus longicephalus, and compared with those of other species. A. longicephalus is concluded to be a distinct species without synonyms, characterized by its long snout, widely separate nostrils, long caudal fin, short abdomen, very sparse teeth, and low number of monospondylous vertebrae. It is a species of small size, maturing at about 42 cm in total length.  相似文献   
190.
Scale morphology, growth and the squarnation chronology are described for the hermaphroditic fish Rivulus marmoratus reared in the laboratory. The scales are round or oval shaped cycloid type, and their sizes are about 0.3–1.0 mm in diameter. The number of ridges increases more rapidly relative to the body growth of the fish in early stages, but this increase is proportionate to growth subsequently. Three loci of scale development have been identified. The scales first appeared on the center of the parietal region at 8 days after hatching. The second locus of scale formation was on the lateral line of the posterior end of the caudal peduncle. A third locus was later observed on the lower right corner of the operculum: The final squamation was completed at 6 weeks after hatching.  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