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   568722篇
  免费   62647篇
  国内免费   339篇
  2018年   5975篇
  2017年   5872篇
  2016年   7769篇
  2015年   9425篇
  2014年   11264篇
  2013年   16730篇
  2012年   19499篇
  2011年   20250篇
  2010年   13170篇
  2009年   11681篇
  2008年   17579篇
  2007年   18178篇
  2006年   16988篇
  2005年   16102篇
  2004年   15890篇
  2003年   15130篇
  2002年   14653篇
  2001年   29375篇
  2000年   29425篇
  1999年   22630篇
  1998年   7081篇
  1997年   7588篇
  1996年   6871篇
  1995年   6516篇
  1994年   6310篇
  1993年   6256篇
  1992年   17350篇
  1991年   16541篇
  1990年   15924篇
  1989年   15419篇
  1988年   14123篇
  1987年   13148篇
  1986年   12217篇
  1985年   12075篇
  1984年   9975篇
  1983年   8371篇
  1982年   6264篇
  1981年   5642篇
  1980年   5327篇
  1979年   9172篇
  1978年   7045篇
  1977年   6492篇
  1976年   5862篇
  1975年   6500篇
  1974年   6951篇
  1973年   6711篇
  1972年   6097篇
  1971年   5558篇
  1970年   4783篇
  1969年   4500篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
We have identified mouse and human FKBP60, a new member of the FKBP gene family. FKBP60 shares strongest homology with FKBP65 and SMAP. FKBP60 contains a hydrophobic signal peptide at the N-terminus, 4 peptidyl-prolyl cis/trans isomerase (PPIase) domains and an endoplasmic reticulum retention motif (HDEL) at the C-terminus. Immunodetection of HA-tagged FKBP60 in NIH-3T3 cells suggests that FKBP60 is segregated to the endoplasmic reticulum. Northern blot analysis shows that FKBP60 is predominantly expressed in heart, skeletal muscle, lung, liver and kidney. With N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide as a substrate, recombinant GST-FKBP60 is shown to accelerate effectively the isomerization of the peptidyl-prolyl bond. This isomerization activity is inhibited by FK506. mFKBP60 binds Ca2+ in vitro, presumably by its C-terminal EF-hand Ca2+ binding motif, and is phosphorylated in vivo. hFKBP60 has been mapped to 7p12 and/or 7p14 by fluorescence in situ hybridization (FISH).  相似文献   
2.
3.
4.
A patient with chronic anemia is presented who radiologically showed prominent rugae of the stomach. Angiography demonstrated an arteriovenous malformation with a large feeding artery and prominent draining veins.  相似文献   
5.
6.
7.
8.
Essential genes were identified in the 1.5-map unit dpy-5 unc-13 region of chromosome I in the Caenorhabditis elegans genome by rescuing lethal mutations using the duplication sDp2. In this paper, we report the mapping and complementation testing of lethal mutations, 45 of which identify 18 new, essential genes. This analysis brings the number of essential genes defined by the sDp2 rescue of lethal mutants to 97; 64 of these map between dpy-5 and unc-13. 61% of these essential genes are identified by more than one allele. Positioning of the mutations was done using the breakpoints of six duplications. The mutant phenotypes of 14 loci essential for fertility were characterized by Nomarski microscopy and DAPI staining. None of the mutants were rescued by wild-type male sperm. The cytological data showed that four genes produced mutants with defects in gonadogenesis, let-395, let-603, let-605 and let-610. Mutations in seven genes, let-355, let-367, let-384, let-513, let-544, let-545 and let-606, affected germ cell proliferation or gametogenesis. Mutants for the remaining three genes, let-370, let-599 and let-604, produced eggs that failed to develop or hatch, thereby acting as maternal effect lethals. We observed a nonrandom distribution of arrest phenotypes with regard to map position. Received: 8 May 1996 / Accepted : 27 January 1997  相似文献   
9.
An in vitro photoautotrophic step based on the supply of CO2-enriched air (1,600 μmol mol?1) during the light phase and ambient air (350 μmol mol?1 CO2) during the dark phase has been used to promote the ex vitro establishment of coconut (Cocos nucifera L.) seedlings. The introduction of this step into a previously developed in vitro protocol was found to improve the quality of the seedlings (as assessed by fresh weight increase, physical stature, leaf area and thickness, stomatal density, and chlorophyll a content, and primary and secondary root production), the proportion of seedlings successfully transferred to soil (improvement from 40% to 100%) and achieved in a shorter time (reduction from 10 to 6 mo). Best results using this photoautotrophic growth step were obtained when a low medium concentration of sucrose (43.8 mM or lower) was used, when it was applied to seedlings that had already reached 4 or 5 mo of age in the in vitro culture step, and when seedlings were cultured in the photoautotrophic system for 2 mo or more before transfer to soil. Our improved protocol is more efficient and it reduces the cost per plant for the international exchange of coconut germplasm.  相似文献   
10.
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