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   856337篇
  免费   92304篇
  国内免费   472篇
  2018年   7732篇
  2016年   10232篇
  2015年   13379篇
  2014年   15915篇
  2013年   23495篇
  2012年   25754篇
  2011年   26445篇
  2010年   17867篇
  2009年   16526篇
  2008年   23297篇
  2007年   24355篇
  2006年   22907篇
  2005年   21895篇
  2004年   21812篇
  2003年   20994篇
  2002年   20432篇
  2001年   39701篇
  2000年   39731篇
  1999年   31227篇
  1998年   10239篇
  1997年   10980篇
  1996年   10168篇
  1995年   9771篇
  1994年   9520篇
  1993年   9604篇
  1992年   25960篇
  1991年   25126篇
  1990年   24619篇
  1989年   24047篇
  1988年   22345篇
  1987年   21022篇
  1986年   19508篇
  1985年   19762篇
  1984年   16282篇
  1983年   13949篇
  1982年   10552篇
  1981年   9486篇
  1980年   8938篇
  1979年   15505篇
  1978年   12001篇
  1977年   11196篇
  1976年   10395篇
  1975年   11402篇
  1974年   12328篇
  1973年   12074篇
  1972年   11151篇
  1971年   10175篇
  1970年   8753篇
  1969年   8561篇
  1968年   7970篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Characteristics of morphology and number of melanomacrophage centers (MMCs) in the liver and spleen of the roach Rutilus rutilus and the amount of pigments in MMCs during the Haff disease outbreak and the death of fish in Lake Kotokel in relation to these parameters in the roach from Lake Baikal are described. Pathological changes in the microvasculature and parenchyma in the liver of the roach from Lake Kotokel were found. The area of melanomacrophage centers in the liver of the roach from this lake was significantly smaller, whereas the number and size of these centers in the spleen was significantly larger than in the roaches from Lake Baikal. Among the pigments studied, the strongest response to the content of this toxin in the water body was shown by hemosiderin. An increase in its amount in the spleen MMCs testifies to an enhanced degradation of erythrocytes and iron release, which may be caused by the damage of cells of the erythrocyte lineage by the toxin.  相似文献   
2.
3.
Developmental axon branching dramatically increases synaptic capacity and neuronal surface area. Netrin-1 promotes branching and synaptogenesis, but the mechanism by which Netrin-1 stimulates plasma membrane expansion is unknown. We demonstrate that SNARE-mediated exocytosis is a prerequisite for axon branching and identify the E3 ubiquitin ligase TRIM9 as a critical catalytic link between Netrin-1 and exocytic SNARE machinery in murine cortical neurons. TRIM9 ligase activity promotes SNARE-mediated vesicle fusion and axon branching in a Netrin-dependent manner. We identified a direct interaction between TRIM9 and the Netrin-1 receptor DCC as well as a Netrin-1–sensitive interaction between TRIM9 and the SNARE component SNAP25. The interaction with SNAP25 negatively regulates SNARE-mediated exocytosis and axon branching in the absence of Netrin-1. Deletion of TRIM9 elevated exocytosis in vitro and increased axon branching in vitro and in vivo. Our data provide a novel model for the spatial regulation of axon branching by Netrin-1, in which localized plasma membrane expansion occurs via TRIM9-dependent regulation of SNARE-mediated vesicle fusion.  相似文献   
4.
5.
6.
More than 50 hereditary lysosomal storage disorders (LSDs) are currently described. Most of these disorders are due to a deficiency of certain hydrolases/glycosidases and subsequent accumulation of nonhydrolyzable carbohydrate-containing compounds in lysosomes. Such accumulation causing hypertrophy of the lysosomal compartment is a characteristic feature of affected cells in LSDs. The investigation of biochemical and cellular parameters is of particular interest for understanding “life” of lysosomes in the normal state and in LSDs. This review highlights the wide spectrum of biochemical and morphological changes during developing LSDs that are extremely critical for many metabolic processes inside the various cells and tissues of affected persons. The data presented will help establish new complex strategies for metabolic correction of LSDs.  相似文献   
7.
The present work aimed to study the effect of palm pollen extract (PPE) as an anticoccidial and anti-apoptotic modulator during the course of murine intestinal Eimeria papillata infection. The fact that PPE has an anticoccidial efficacy against intestinal E. papillata infection in mice has been clarified by the reduction of faecal output of oocysts on day five post infection from 49.5 × 103 to 34 × 103 oocyst/g. Moreover, the number of intracellular eimerian stages of zygots and developing oocysts decreased by about 89% and that of schizonts and gamonts to 42% and 72%, respectively. E. papillata infection also induced an increase in the number of apoptotic cells from 17.5 to 122.8 apoptotic nuclei/10 villous crypt units (VCU). In addition, it caused a state of systemic inflammatory response as revealed by an elevation in levels of the pro-inflammatory biomarkers, inducible nitric oxide synthase (iNOs) and tumor necrosis factor alpha (TNF-α) from 5.3 and 78.3 to 33 pmol ml?1 and 96.3 pg ml?1 in blood, respectively, with concurrent duplication in the total leucocytic number. Upon treatment of infected mice with the aqueous PPE, the activity of iNOs was reduced by 55% and the level of TNF-α was decreased by 30%. Moreover, the total leucocytic count was significantly reduced from 9.05 × 103 to 7.8 × 103 cells/mm3. Based on our results, PPE showed both anti-coccidial, anti-inflammatory and anti-apoptotic activities. So it can be used in developing new herbal medicine against animal coccidiosis and may be suitable agent for treating eimeriosis associated inflammatory response.  相似文献   
8.
9.
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