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   554467篇
  免费   65899篇
  国内免费   331篇
  2016年   5636篇
  2015年   7897篇
  2014年   9408篇
  2013年   13140篇
  2012年   14855篇
  2011年   15037篇
  2010年   10143篇
  2009年   9700篇
  2008年   13626篇
  2007年   13988篇
  2006年   13491篇
  2005年   13232篇
  2004年   12892篇
  2003年   12842篇
  2002年   12406篇
  2001年   26217篇
  2000年   26506篇
  1999年   21005篇
  1998年   7071篇
  1997年   7408篇
  1996年   7094篇
  1995年   6540篇
  1994年   6494篇
  1993年   6573篇
  1992年   17398篇
  1991年   17104篇
  1990年   16402篇
  1989年   16186篇
  1988年   15257篇
  1987年   14554篇
  1986年   13346篇
  1985年   13399篇
  1984年   10927篇
  1983年   9676篇
  1982年   7320篇
  1981年   6694篇
  1980年   6268篇
  1979年   10672篇
  1978年   8335篇
  1977年   7800篇
  1976年   7186篇
  1975年   7970篇
  1974年   8545篇
  1973年   8421篇
  1972年   7628篇
  1971年   7028篇
  1970年   6206篇
  1969年   6146篇
  1968年   5461篇
  1967年   4720篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
891.
892.
893.
Brief admission of the new diabetic child and of a parent to an enlightened hospital for stabilisation, preliminary education, and familiarisation with hospital and community staff is well worth while. The greater the demand for constant control of the highest quality, the greater the need for a close understanding of the psychosocial factors concerned and for clinical skill. The nature of the home and the family relationships should in theory be available from the child''s general practitioner at the time of the first referral since he has so much information about the whole family. With the virtual disappearance, however, of mutual consultation in the patient''s home in many places, the opportunity for oral communication has declined, and availability on the telephone is not always easy. The busy general practitioner (far less an unknown physician from a deputising service without access to the records) has little time to write a comprehensive letter. In practice a relatively small hospital-based mobile team of specially experienced sisters who are keen to communicate in the home, the GP''s surgery, and the school makes a major contribution to the diabetic care of a young population vulnerable to major handicap in what should be the prime of life. Their cost effectiveness may be difficult to prove but it is not at all in doubt--especially when the sisters as in this area deal in the community with a wider range of chronic illnesses and handicaps in children.  相似文献   
894.
895.
896.
The TREX enzymes process DNA as the major 3′→5′ exonuclease activity in mammalian cells. TREX2 and TREX1 are members of the DnaQ family of exonucleases and utilize a two metal ion catalytic mechanism of hydrolysis. The structure of the dimeric TREX2 enzyme in complex with single-stranded DNA has revealed binding properties that are distinct from the TREX1 protein. The TREX2 protein undergoes a conformational change in the active site upon DNA binding including ordering of active site residues and a shift of an active site helix. Surprisingly, even when a single monomer binds DNA, both monomers in the dimer undergo the structural rearrangement. From this we have proposed a model for DNA binding and 3′ hydrolysis for the TREX2 dimer. The structure also shows how TREX proteins potentially interact with double-stranded DNA and suggest features that might be involved in strand denaturation to provide a single-stranded substrate for the active site.  相似文献   
897.
898.
899.
The distribution of anti-RNA antibody-binding sites on the surfaces of Ehrlich ascites tumor cells was studied by membrane immunofluorescence after binding anti-RNA antibody on the cell surfaces. Results showed that the cells formed caps after incubation with anti-RNA antibody at 4 degrees C and the elevation of their temperature to 37 degrees C. Pronase treatment of the cell surfaces completely inhibited reactivity with anti-RNA antibody. These results suggest that the RNAs on the surfaces of Ehrlich ascites tumor cells are linked to membrane protein membrane-bound cytoskeleton complexes.  相似文献   
900.
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