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   450854篇
  免费   49949篇
  国内免费   282篇
  2018年   4378篇
  2016年   5907篇
  2015年   7854篇
  2014年   9169篇
  2013年   12688篇
  2012年   14329篇
  2011年   14693篇
  2010年   10132篇
  2009年   9264篇
  2008年   13349篇
  2007年   13768篇
  2006年   12948篇
  2005年   12289篇
  2004年   12340篇
  2003年   11569篇
  2002年   11444篇
  2001年   18157篇
  2000年   18068篇
  1999年   14544篇
  1998年   5349篇
  1997年   5598篇
  1996年   5153篇
  1995年   4867篇
  1994年   4672篇
  1993年   4772篇
  1992年   12023篇
  1991年   11918篇
  1990年   11644篇
  1989年   11246篇
  1988年   10759篇
  1987年   10333篇
  1986年   9624篇
  1985年   9543篇
  1984年   8036篇
  1983年   6960篇
  1982年   5332篇
  1981年   4816篇
  1980年   4639篇
  1979年   7647篇
  1978年   6068篇
  1977年   5616篇
  1976年   5405篇
  1975年   5805篇
  1974年   6492篇
  1973年   6349篇
  1972年   5915篇
  1971年   5374篇
  1970年   4768篇
  1969年   4700篇
  1968年   4578篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Monoclonal antibodies against regulatory subunit of cAMP-dependent protein kinase, type II, were obtained from pig brain (R II). The immune-affinity sorbent has been synthesized on the basis of monoclonal antibodies against R II. The method was proposed for the purification of homogeneous R II with high cAMP-binding activity using immune-affinity sorbent.  相似文献   
952.
In order to verify the applicability of biochemical methods for species identification of Trypanosomatidae, 13 species of monoxenic trypanosomatids plus the heteroxenous Trypanosoma cruzi were comparatively analyzed by three different biochemical methods. Insect trypanosomatids examined were: Crithidia acanthocephali, C. fasciculata (three varieties), C. luciliae luciliae, C. luciliae thermophila, C. deanei, C. oncopelti, Herpetomonas muscarum muscarum, H. megaseliae, H. samuelpessoai, H. mariadeanei, Leptomonas seymouri, L. collosoma, L. samueli, and Blastocrithidia culicis. Also included in the survey were aposymbiotic strains of C. deanei and C. oncopelti. Methods used were: electrophoretic profiling of endonuclease-generated fragments of k-DNA, esterase isoenzymes profiling, and polyacrylamide-gel electrophoresis (SDS-PAGE) of radioiodinated cell surface proteins. Interspecific but not intraspecific differences were detected by all three methods among the 13 monoxenic species examined. Thus, it is concluded that these methods can be successfully used, in addition to classical criteria, for species identification of insect trypanosomatids.  相似文献   
953.
954.
955.
The case of a 53 years old woman was described in whom a congenital factor XIII deficiency was suspected because of deforming scars and hemorrhagic diathesis. A thromboelastographic declination of elasticity as well as decreased factor XIII level up to 5% of normal range were only found in all hemostatic examinations. In 2 children factor XIII decreased to half of its normal level, whereas in the youngest daughter that level was 25%. Sporadically the girl had mild diathesis. No changes in thromboelastograms were observed in members of the patient's family. The platelet function was unchanged in all examined cases.  相似文献   
956.
The isoelectric point of the camel and the human β-endorphin, of the α-endorphin and the enkephalins were determined by analytical isoelectric focusing on 1 mm thin polyacrylamide gel slab. The difficulty of staining peptides as short as β-endorphin or smaller was overcomed using a modification of Bibring and Baxandall's or Faupel and Von Arx's staining method. The camel β-endorphin gives two bands having isoelectric point of 10.3 and 10.4, the human β-endorphin focus at pH 9.9, while α-endorphin, leu and met-enkephalin at pH 5.9, 5.5 and 5.45 respectively. The staining method described coupled with the isoelectric focusing seems to be fit for discriminating β-endorphin in a crude rat pituitary extract.  相似文献   
957.
958.
The influence of surfactant depletion on clearance from the lungs of inhaled technetium-99m-labeled diethylenetriamine pentaacetate (99mTc-DTPA) was studied in rabbits. Surfactant was removed by repeated lung lavage with isotone saline. To minimize structural damage to the lungs, pressure generated insufflation with short expiration was utilized. Aerosolized 99mTc-DTPA was administered via a bag-in-bottle system. Radioactivity was measured with a gamma camera and time-activity curves were obtained over the base of the right lung. Six nonlavaged rabbits served as controls. In six lavaged rabbits clearance of 99mTc-DTPA was significantly faster than in controls. In three rabbits given natural surfactant into the trachea after lung lavage, 99mTc-DTPA was eliminated faster than in controls but slower than in surfactant-depleted animals. The results indicate a role of surfactant on clearance rate of 99mTc-DTPA from rabbit lungs. Measurements of 99mTc-DTPA clearance may be useful in studying the function of the surfactant system in different lung disorders.  相似文献   
959.
960.
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