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   1918篇
  免费   183篇
  2101篇
  2021年   14篇
  2020年   11篇
  2019年   18篇
  2018年   34篇
  2017年   24篇
  2016年   25篇
  2015年   36篇
  2014年   55篇
  2013年   115篇
  2012年   82篇
  2011年   86篇
  2010年   45篇
  2009年   53篇
  2008年   74篇
  2007年   105篇
  2006年   105篇
  2005年   97篇
  2004年   105篇
  2003年   94篇
  2002年   72篇
  2001年   67篇
  2000年   75篇
  1999年   75篇
  1998年   32篇
  1997年   26篇
  1996年   27篇
  1995年   26篇
  1994年   19篇
  1993年   21篇
  1992年   38篇
  1991年   35篇
  1990年   43篇
  1989年   33篇
  1988年   27篇
  1987年   31篇
  1986年   27篇
  1985年   27篇
  1984年   18篇
  1983年   24篇
  1982年   14篇
  1981年   14篇
  1980年   17篇
  1979年   21篇
  1978年   11篇
  1977年   13篇
  1976年   8篇
  1974年   7篇
  1973年   14篇
  1972年   11篇
  1968年   9篇
排序方式: 共有2101条查询结果,搜索用时 0 毫秒
101.
102.
Cerebroside fraction was obtained from fresh fruiting bodies of Lentinus edodes and separated into ten molecular species by reverse-phase high-performance liquid chromatography. The species were identified by GLC, GC-MS and NMR. Their component glycosides and sphingoids were uniformly glucose and (4E,8E)-9-methyl-4,8-sphingadienine, respectively. The component fatty acids were 2-hydroxy acids with the carbon chain length of 16, 15, 14, 18, 24, 17, 25, 26, 22 and 23 (from major to minor). The cerebrosides with the C14-18 fatty acids showed strong fruiting-inducing activity in Schizophyllum commune. Those with the C22 and C23 ones had one-eighth and one-sixteenth of the activity, respectively, and those with C24-26 had no detectable activity. 22 and 23 must be the carbon chain lengths of the component fatty acid of the sphingolipids critical for expression of biological activity.  相似文献   
103.
Several attempts were made to investigate the mechanism of the asymmetrical radical formation in yttrium-90-beta-irradiated D- and L-alanines which was reported in the preceding paper (1). The experiments demonstrated that the magnitude of the asymmetry was dependent on beta-ray dose, namely the lower the dose the larger the observed difference was, and that no difference could be detected when the alanines were irradiated in aqueous state. The results in the present study seem to that different interaction between the crystal structure of the two enantiomers and polarized beta-rays may be responsible for the observed phenomenon.  相似文献   
104.
There has been considerable interest in the relationship between hormone- secreting endocrine cells and their microvessels in human pituitary gland. However, microcirculatory networks have rarely been studied in three dimensions (3D). This study was designed to visualize and to reveal the relationship between hormone-secreting endocrine cells and their microvessel environment in 3D, using rat pituitary glands under various (hyper/hypo) experimental conditions by confocal laser scanning microscopy (CLSM). Female adult Wistar rats were used after bilateral adrenalectomy or ACTH administration for 2 weeks. Clear 3D reconstructed images of ACTH cells, the microvessel network and counterstained nuclei were obtained at a maximal focus depth of 1 mm by CLSM without any background noise. In the hyperfunctional state, slender cytoplasmic processes of hypertrophic stellate ACTH cells frequently extended to the microvessels. In the hypofunctional state, ACTH cells appeared atrophic and round with scanty cytoplasm, and cytoplasmic adhesions to microvessel network patterns were inconspicuous. Therefore, 3D reconstructed imaging by CLSM is a useful technique with which to investigate the microvessel environment of hormone-secreting cells and has the potential to reveal dynamic hormone-secreting pathways.  相似文献   
105.
106.
Undifferentiated pleomorphic sarcoma (UPS) is an aggressive mesenchymal malignancy requiring novel therapeutic approaches to improve clinical outcome. Patient-derived cancer cell lines are an essential tool for investigating molecular mechanisms underlying cancer initiation and development; however, there is a lack of patient-derived cell lines of UPS available for research. The objective of this study was to develop a patient-derived cell model of UPS. A cell line designated NCC-UPS2-C1 was established from the primary tumor tissue of an 84-yr-old female patient with UPS. The short tandem repeat pattern of NCC-UPS2-C1 cells was identical to that of the original tumor and distinct from that of any other cell lines deposited in public cell banks. NCC-UPS2-C1 cells were maintained as a monolayer culture for over 80 passages during 30 mo and exhibited spindle-like morphology, continuous growth, and ability for spheroid formation and invasion. Proteomic profiling using mass spectrometry and functional treemap analysis revealed that the original tumor and the derived NCC-UPS2-C1 cells had similar but distinct protein expression patterns. Our results indicate that a novel UPS cell line was successfully established and could be used to study UPS development and effects of anti-cancer drugs. However, the revealed difference between proteomes of the original tumor and NCC-UPS2-C1 cells should be further investigated to determine the appropriate applications of this cell line in UPS research.  相似文献   
107.
Summary  Rubroskyrin, a modified bisanthraquinone pigment from an yellow rice moldPenicillium islandicum Sopp, was examined for its redox-interaction with the mitochondrial respiratory chain by using rat liver submitochondrial particles (SMP) and was compared with luteoskyrin and rugulosin. Rubroskyrin showed a redox interaction with the NAD-linked respiratory chain of SMP, promoting NADH oxidase in the presence of rotenone, a specific inhibitor to coupling site I of the respiratory chain. Rubroskyrin-mediated NADH oxidase was not inhibited by antimycin A and cyanide, inhibitors to coupling sites II and III, respectively, indicating a generation of an electron transport shunt from a rotenone-insensitive site of NADH dehydrogenase (complex I) to dissolved oxygen. An electrontransport shunt to cytochromec oxidase from complex I was also observed in the experiment with cytochromec and antimycin A. Rubroskyrin did not interact with succinate-linked respiratory chain. Such enzymatic redox response which generates electron transport shunt was not detected for luteoskyrin and rugulosin in the present study.  相似文献   
108.
The gene encoding Clara cell-derived inflammatory molecule CC16 has been cited as a candidate gene for atopic asthma on chromosome 11q13. A genetic association study was performed with variants of the CC16 gene on chromosome 11q13 in relation to asthma in British (n=275) and Japanese (n=300) populations. No significant association was found between asthma and CC16 genotypes, irrespective of atopic status in these two populations. These data suggest that CC16 might not be the major locus for asthma on 11q13. Received: 22 December 1997 / Accepted: 9 February 1998  相似文献   
109.
110.
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