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   7453篇
  免费   591篇
  国内免费   1篇
  8045篇
  2023年   60篇
  2022年   108篇
  2021年   225篇
  2020年   143篇
  2019年   154篇
  2018年   175篇
  2017年   154篇
  2016年   255篇
  2015年   424篇
  2014年   447篇
  2013年   534篇
  2012年   681篇
  2011年   645篇
  2010年   399篇
  2009年   364篇
  2008年   506篇
  2007年   434篇
  2006年   420篇
  2005年   357篇
  2004年   314篇
  2003年   257篇
  2002年   270篇
  2001年   54篇
  2000年   47篇
  1999年   53篇
  1998年   46篇
  1997年   40篇
  1996年   36篇
  1995年   34篇
  1994年   29篇
  1993年   18篇
  1992年   41篇
  1991年   32篇
  1990年   24篇
  1989年   29篇
  1988年   15篇
  1987年   20篇
  1986年   23篇
  1985年   19篇
  1984年   11篇
  1983年   12篇
  1982年   13篇
  1981年   13篇
  1980年   15篇
  1979年   7篇
  1978年   10篇
  1977年   13篇
  1976年   8篇
  1975年   8篇
  1973年   9篇
排序方式: 共有8045条查询结果,搜索用时 15 毫秒
1.
2.
3.

Introduction  

Sj?gren's syndrome (SS) is a systemic autoimmune disease that mainly targets the exocrine glands. The aim of this study was to investigate the involvement of 87 proteins measured in serum and 75 proteins analyzed in saliva in spontaneous experimental SS. In addition, we intended to compute a model of the immunological situation representing the overt disease stage of SS.  相似文献   
4.
5.
6.
7.
Understanding drivers of biodiversity patterns is of prime importance in this era of severe environmental crisis. More diverse plant communities have been postulated to represent a larger functional trait‐space, more likely to sustain a diverse assembly of herbivore species. Here, we expand this hypothesis to integrate environmental, functional and phylogenetic variation of plant communities as factors explaining the diversity of lepidopteran assemblages along elevation gradients in the Swiss Western Alps. According to expectations, we found that the association between butterflies and their host plants is highly phylogenetically structured. Multiple regression analyses showed the combined effect of climate, functional traits and phylogenetic diversity in structuring butterfly communities. Furthermore, we provide the first evidence that plant phylogenetic beta diversity is the major driver explaining butterfly phylogenetic beta diversity. Along ecological gradients, the bottom up control of herbivore diversity is thus driven by phylogenetically structured turnover of plant traits as well as environmental variables.  相似文献   
8.
9.
Carrier diagnosis and prenatal diagnosis of Duchenne's muscular dystrophy (DMD) and Becker's muscular dystrophy (BMD) has become possible using some twenty RFLPs detected by more than a dozen Xp21 probes that are either intragenic or flanking the disease locus. Results from familial studies on 88 DMD and BM families stress important considerations concerning a priori and final risks, individuals necessary for the identification of the phase, and the different strategies that can be applied, regardless of whether the study concerns an on-going pregnancy or a carrier-status determination, and whether the patient is at high or low risk. Finally, multiple sources of difficulties in interpreting the results depend on a) the occurrence of new mutations that must be traced; b) the existence of meiotic recombination; c) the necessity, in some instances, of relying upon the sole identification of the paternal X. These considerations emphasize the characteristics and the important limitations of this type of methodology.  相似文献   
10.
Summary Single photoreceptor cells in the compound eye of the housefly Musca domestica were selectively illuminated and subsequently compared electron-microscopically with the unilluminated photoreceptors in the immediate surroundings. The rhabdomeres of the illuminated cells remain largely unaffected, but the cells show an increase in the number of coated pits, various types of vesicles, and degradative organelles; some of the latter organelles are described for the first time in fly photoreceptors. Coated pits are found not only at the bases of the microvilli, but also in other parts of the plasma membrane. Degradative organelles, endoplasmic reticulum (ER) and mitochondria aggregate in the perinuclear region. The rough ER and smooth ER are more elaborate, the number of Golgi stacks, free ribosomes and polysomes is increased, and the shape and distribution of heterochromatin within the nuclei are altered. Illuminated photoreceptors also interdigitate extensively with their neighbouring secondary pigment cells. These structural changes in illuminated fly photoreceptor cells indicate an increase in membrane turnover and cellular metabolism. When applied to the eye, Lucifer Yellow spreads into the extracellular space and is taken up only by the illuminated photoreceptor cells. These cells show the same structural modifications as above. Horseradish peroxidase applied in the same way is observed in pinocytotic vesicles and degradative organelles of the illuminated cells. Hence, the light-induced uptake of extracellular compounds takes place in vivo at least partially as a result of an increase in pinocytosis.  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