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   557871篇
  免费   62725篇
  国内免费   380篇
  620976篇
  2016年   6366篇
  2015年   8785篇
  2014年   10145篇
  2013年   15030篇
  2012年   16369篇
  2011年   16773篇
  2010年   11323篇
  2009年   10263篇
  2008年   14983篇
  2007年   15491篇
  2006年   14595篇
  2005年   14100篇
  2004年   14055篇
  2003年   13638篇
  2002年   13382篇
  2001年   23955篇
  2000年   23930篇
  1999年   19143篇
  1998年   6946篇
  1997年   7266篇
  1996年   6951篇
  1995年   6481篇
  1994年   6451篇
  1993年   6393篇
  1992年   16441篇
  1991年   16019篇
  1990年   15570篇
  1989年   15261篇
  1988年   14140篇
  1987年   13592篇
  1986年   12328篇
  1985年   12694篇
  1984年   10521篇
  1983年   9027篇
  1982年   7099篇
  1981年   6427篇
  1980年   6093篇
  1979年   10390篇
  1978年   7934篇
  1977年   7525篇
  1976年   7010篇
  1975年   7677篇
  1974年   8367篇
  1973年   8368篇
  1972年   7601篇
  1971年   7075篇
  1970年   6181篇
  1969年   6010篇
  1968年   5450篇
  1967年   4739篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Reconstruction of normal shoulder contour is possible utilizing a latissimus dorsi musculocutaneous flap at the end of a long neurovascular pedicle. The thoracodorsal vessels and their lateral divisions form the basis of the pedicle. The nerve in the pedicle is left intact if maintenance of muscle bulk is desired and sectioned if atrophy is preferred. The amount of muscle taken in conjunction with the skin island is determined by the nature of the defect to be corrected. The twin goals of a single-stage reconstruction and a satisfactory aesthetic result are achieved with this method.  相似文献   
992.
Using a slide culture technique, it was determined unequivocally that the chlamydospore of Candida albicans does germinate. The germination was by way of a multiple-budding process which was associated mostly with young spores following their transfer to a fresh environment. It is concluded the chlamydospore of C. albicans is a reproductive cell with a transient viability.  相似文献   
993.
Urease was immobilized on O-alkylated nylon tubes coated with polyaminated derivatives of starch or dextran. The specific activity of the enzyme coil and the relative stability of the immobilized enzyme, compared with immobilized urease derived from other nylon tube modifications, were enhanced. Also, the nonspecific binding of urease to O-alkylated nylon tubes was virtually eliminated by the coating process.  相似文献   
994.
Mutants with impaired biosynthesis of unsaturated fatty acids or altered metabolism of the phospholipids were isolated at a rather high frequency from a set of temperature-sensitive lysis mutants. It is suggested that preselection for the lysis phenotype makes it possible to isolate several kinds of mutants affected in the integrity of the cytoplasmic membrane.  相似文献   
995.
996.
997.
Sporadic (less than regular weekly) coital activity is associated with a particular type of infertility—the short hyperthermic (luteal) phase. This preliminary report is the first suggestion that a reduced frequency of human sexual activity might, itself, be associated with subfertile reproductive function.  相似文献   
998.
999.
1000.
F Osman  C Cotton  B Tomsett  P Strike 《Biochimie》1991,73(2-3):321-327
A mutant of Aspergillus nidulans, designated nuv11, has been isolated as hypersensitive to the monofunctional alkylating agent MNNG and the quasi-UV-mimetic mutagen 4-NQO. The mutation was recessive, resulting from mutation of a single gene which mapped to chromosome IV, and was non-allelic to the previously characterised repair-deficient mutations uvsB and uvsH which are also located on this linkage group. The nuv11 mutation results in slow growth, deficient intragenic and intergenic meiotic recombination, increased spontaneous chromosome instability, and increased intragenic and intergenic mitotic recombination in homozygous diploids. By screening a wild-type gene bank of A nidulans, a clone (pNUV11A40) has been isolated which complements the nuv11 mutation, restoring wild-type responses to both MNNG and 4-NQO.  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