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   1300篇
  免费   60篇
  2021年   12篇
  2020年   7篇
  2019年   5篇
  2018年   12篇
  2017年   12篇
  2016年   17篇
  2015年   35篇
  2014年   36篇
  2013年   139篇
  2012年   44篇
  2011年   58篇
  2010年   36篇
  2009年   42篇
  2008年   64篇
  2007年   80篇
  2006年   68篇
  2005年   75篇
  2004年   74篇
  2003年   57篇
  2002年   79篇
  2001年   18篇
  2000年   12篇
  1999年   14篇
  1998年   13篇
  1997年   7篇
  1996年   12篇
  1995年   11篇
  1994年   12篇
  1993年   20篇
  1992年   17篇
  1991年   13篇
  1990年   20篇
  1989年   24篇
  1988年   18篇
  1987年   17篇
  1986年   13篇
  1985年   14篇
  1984年   27篇
  1983年   18篇
  1982年   10篇
  1981年   13篇
  1980年   8篇
  1979年   8篇
  1978年   11篇
  1976年   8篇
  1975年   6篇
  1974年   6篇
  1973年   6篇
  1967年   5篇
  1961年   4篇
排序方式: 共有1360条查询结果,搜索用时 15 毫秒
991.
992.
Summary The presence of three water-soluble gibberellins was confirmed in immature seeds of morning-glory (Pharbitis nil). The structure of the main component has been elucidated as 2-O--glucosyl-gibberellin A3. It shows marked growth-promoting activity on rice seedlings but is far less active on dwarf maize mutants d 1, d 2 and d 5.  相似文献   
993.
An immunocytochemical study was performed to examine the expression of cellular c-myc protein in the heart of 30-, 120- and 180-day-old cardiomyopathic Syrian UM-X7.1 hamsters. The heart of age- and sex-matched BIO-RB hamster was used as normal control. In paraffin sections, an immunostaining for c-myc was markedly increased in cytoplasm of cells from the UM-X7.1 heart as compared with that of the BIO-RB heart which showed a weak staining. However, c-myc was localized in nuclei of cells in frozen sections of the heart. Specific cell types of the heart were differentiated with anti-vimentin, and we found that the increased expression of c-myc was present in nuclei of muscle cells of the UM-X7.1 myocardium. A quantitative study of c-myc-positive nuclei of muscle and nonmuscle cells was carried out by a video micrometer. The mean number of c-myc-positive nuclei of muscle cells was significantly higher in the cardiomyopathic heart than in the control heart from hamsters of all ages studied. These results suggest that the increase of c-myc protein may relate to the pathological state or pathogenesis of the hereditary cardiomyopathy.  相似文献   
994.
995.
Possible immunological differences between monkey and human prostate gland proteins and also between seminal vesicle proteins of these species were investigated by agarose gel electrophoresis, agarose gel immunoelectrophoresis and by the agar gel immunodiffusion method, using anti-sera against human plasma, human seminal plasma and human prostatic acid phosphomonoesterase (PMEase). At the same time, the electrophoretic mobility of these prostatic acid PMEases was compared by means of starch gel electrophoresis.Each of these two tissues, monkey and human, was found to contain antigenic proteins with immunological identity. Though antigenic similarity of monkey and human prostatic acid PMEase was demonstrated by immunological methods, a clear difference was observed in the electrophoretic mobility of these enzymes when examined by starch gel electrophoresis.  相似文献   
996.
997.
In the present study, Methylobacterium sp. FD1 utilizing formaldehyde was isolated from soil. The resting cells of FD1 degraded high concentrations of formaldehyde (~2.7 M) and produced formic acid and methanol that were molar equivalents of one-half of the degraded formaldehyde. This result suggests that formaldehyde degradation by FD1 is caused by formaldehyde dismutase. The optimal temperature and pH for formaldehyde degradation by the resting cells of FD1 were 40 °C and 5–7, respectively. The lyophilized cells of FD1 also degraded high concentrations of formaldehyde. The formaldehyde degradation activity of the lyophilized cells was maintained as the initial activity at 25 °C for 287 days. These results suggest that the lyophilized cells of FD1 are useful as formaldehyde degradation materials.  相似文献   
998.
Chromogranin A (CgA), a secretory protein, is co-released with catecholamines from storage vesicles. It is known to be elevated in the circulation of patients with neuroendocrine and endocrine tumors. For further investigation of the protein, especially in humans, it is essential to facilitate quantitative analysis of the protein in human biological materials. In order to introduce novel immunological methodology for this purpose, we purposely selected human CgA(344-374) for the synthetic immunogen to produce region-specific CgA antibodies. The anti-synthetic peptide antibody thus obtained made it possible to develop an immunological method for measurement and characterization of CgA in human plasma. The plasma CgA-immunoreactivity (LI) level measured by the method was 0.31+/-0.01 pmol/ml (mean+/-SEM) in normal subjects and 1.55+/-0.29 pmol/ml in pheochromocytoma. On gel chromatography and HPLC analysis of the plasma of patients with pheochromocytoma, the region-specific assay system enabled us to show the presence of N-terminal truncated CgA, besides CgA itself. By following up changes of plasma CgA-LI in a pheochromocytoma patient using samples that were collected consecutively over a two-year period, the present assay system using the region-specific antibody, anti-human CgA (344-374) serum, was confirmed to be extremely valuable for the measurement of CgA-LI in human plasma. The characteristic features and high sensitivity of the present assay system will give us a substantial clue to the detection and measurement of CgA to develop further investigation of the protein in humans.  相似文献   
999.
The early ontogeny of the pinnately, palmately, and ternately compound leaves in the Lardizabalaceae was studied by SEM. The leaf primordium of each of the three leaf types emerges as an identical short protrusion on the shoot apex; the leaf primordium produces the first leaflet initials laterally on its margin. Successive acropetal growth of the leaf axis and the following inception of the leaflet primordia are responsible for the pinnately compound leaf, whereas short basipetal growth accompanied with initiation of two or more pairs of leaflet initials results in a palmately compound leaf. If no elongation of the leaf axis nor additional inception of leaflet primordia occur during early ontogeny, a ternate leaf ensues.  相似文献   
1000.
Cell culture flasks applicable for altered gravity conditions, such as centrifugation, clino-rotation or microgravity in space, were manufactured for trial. The flask has flat polystyrene surface for monolayer culture and gas-permeable film window on the opposite face. The space in-between consists the culture chamber to be filled with liquid medium. To reduce the water loss and bubble formation in the culture fluid, another gas permeable window was placed on top to form a space where distilled water may be filled. The double-decker culture flask can be used for both space and ground-based experiments in common.  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