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   62739篇
  免费   5702篇
  国内免费   42篇
  68483篇
  2022年   392篇
  2021年   746篇
  2020年   471篇
  2019年   574篇
  2018年   771篇
  2017年   709篇
  2016年   1232篇
  2015年   2052篇
  2014年   2366篇
  2013年   3094篇
  2012年   4020篇
  2011年   3997篇
  2010年   2642篇
  2009年   2427篇
  2008年   3477篇
  2007年   3687篇
  2006年   3538篇
  2005年   3300篇
  2004年   3318篇
  2003年   3230篇
  2002年   3000篇
  2001年   648篇
  2000年   444篇
  1999年   721篇
  1998年   884篇
  1997年   638篇
  1996年   587篇
  1995年   573篇
  1994年   549篇
  1993年   594篇
  1992年   546篇
  1991年   462篇
  1990年   454篇
  1989年   444篇
  1988年   442篇
  1987年   440篇
  1986年   439篇
  1985年   500篇
  1984年   612篇
  1983年   559篇
  1982年   673篇
  1981年   725篇
  1980年   679篇
  1979年   415篇
  1978年   460篇
  1977年   449篇
  1976年   392篇
  1975年   348篇
  1974年   407篇
  1973年   354篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Protamine treatment of type 1 dengue-infected mouse brain suspension resulted in precipitation of several viral specific activities. Complement-fixation activity was almost completely precipitated by protamine. The complement-fixation components recovered in the precipitate were comparable to a non-precipitated reference dengue 1 antigen in their homologous and heterologous reactions. Dengue hemagglutinin was also precipitated by the same treatment. The precipitated hemagglutinin was resolved into three components by buoyant density centrifugation, whose densities were 1.236, 1.215, and 1.178 g/ml, respectively. Three similar HA components were detected in non-protamine treated virus preparations. In both instances the highest-titered HA fraction possessed a buoyant density of 1.21–1.22 g/ml. These HA components were tested in the hemagglutination-inhibition reaction and were proved to be virus-specific. Cesium chloride density gradient centrifugation was shown to be useful for removing possible inhibitor(s) of viral specific hemagglutinin.  相似文献   
82.
The present study reports the isolation and characterization of a cadmium-containing glycoprotein from the water-soluble fraction of an aquatic insect. The isolated glycoprotein contained 0·67% cadmium, 62·1% carbohydrate, and 37·2% protein. The glycoprotein appears to be involved in the detoxification of cadmium, because species insensitive to cadmium contain five times the amount of the glycoprotein as do species sensitive to cadmium.  相似文献   
83.
84.
A new protein crosslinking agent, 2,3-dibromopropionyl-N-hydroxysuccinimide ester, has been synthesized and characterized. The potential use of this compound as a temperature-controllable heterobifunctional crosslinking agent has been investigated using model systems and its reactivity compared with that of chlorambucil-N-hydroxysuccinimide ester. The coupling of14C-labeled phenylethylamine to lysozyme has been used to illustrate the feasibility of the use of this crosslinking agent for the synthesis of immunotoxins.  相似文献   
85.
86.
The ontogeny of large, globular, epidermal cytoplasmic inclusions (ECI) in P. virgatum roots was studied at the ultrastructural level. These ECI were seen to originate in meristematic cells as small electron translucent vesicles. Subsequently, the ECI, which appeared to be temporary storage sites, were seen to enlarge and increase in density by accumulating masses of a granular matrix as well as some small vesicular inclusions. In the zone of elongation, as the epidermal cells matured, the ECI within each cell gradually fused and the contents were lost. The pattern of the ontogeny of the ECI in the growing epidermal cells was consistent with the presence of cells of different physiologies in the zone of cell elongation of these roots.  相似文献   
87.
88.
89.
The functional anatomy of the head of Flabelliderma commensalis is described and compared to other flabelligerid polychaetes. Prostomial parts include the dorsal lip, the palps, two pairs of nuchal organs, four eyes and the prostomial lobe and ridge. The eyes are inverse pigment cup types with the medial portions of the sensory cells expanded to form a clear lens-like body. Peristomial parts include the median and ventral lips, the branchial membrane and the branchiae. The derivation of the nephridiopore is unknown. The spiraled branchiae of Coppingeria and the gill books of Diplocirrus are newly described variations in branchial structure. The head is retractable in some species and the anterior setigers are modified to form a protective setal cage. Two methods are employed for feeding: one for host fecal pellets and the other for detrital materials. Chemoreception, respiration, feeding and cleaning rely on a complex pattern of ciliary currents.  相似文献   
90.
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