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   597篇
  免费   56篇
  2021年   2篇
  2019年   4篇
  2018年   7篇
  2017年   7篇
  2016年   14篇
  2015年   18篇
  2014年   30篇
  2013年   29篇
  2012年   46篇
  2011年   40篇
  2010年   24篇
  2009年   20篇
  2008年   30篇
  2007年   38篇
  2006年   34篇
  2005年   29篇
  2004年   35篇
  2003年   40篇
  2002年   39篇
  2001年   6篇
  2000年   11篇
  1999年   6篇
  1998年   8篇
  1997年   10篇
  1996年   9篇
  1995年   12篇
  1994年   6篇
  1993年   10篇
  1992年   8篇
  1991年   11篇
  1989年   7篇
  1988年   5篇
  1987年   6篇
  1986年   3篇
  1985年   4篇
  1984年   4篇
  1983年   2篇
  1982年   2篇
  1981年   4篇
  1980年   5篇
  1979年   2篇
  1978年   2篇
  1977年   4篇
  1975年   2篇
  1974年   3篇
  1973年   2篇
  1971年   3篇
  1969年   1篇
  1967年   1篇
  1966年   1篇
排序方式: 共有653条查询结果,搜索用时 312 毫秒
101.
BackgroundAppendiceal goblet cell carcinoids (GCCs) exhibit neuroendocrine and adenocarcinoma features.ResultsMedian age for f/m was 59/58 years, respectively, and similar for localized and disseminated disease. At diagnosis 54 patients had localized appendiceal disease (f/m: 29/25). According to TNM 24% had Stage I, 70% had Stage II and 6% had Stage III. Twenty-nine patients had disseminated disease (f/m: 27/2). Chromogranin A, synaptophysin and p53 were positive in >90%. Serotonin was positive in 70%. Median Ki67 index was 32% (6-75%) and higher in Tang group C (50%) compared to group A (30%; p<0.0001), and group B (30%; p<0.004). All patients had surgery. Sixty-three (76%) had radical resections including all patients with localized disease. Median OS was 83 months. The 1-, 5- and 10-year survival rates were 90%, 58%, and 38%, respectively. For localized disease OS was 164 months and 1-, 5- and 10-year survival rates were 100%, 80%, and 55%, respectively. For disseminated disease OS was 19 months and 1-, 5- and 10-year survival rates were 73%, 18% and 6%, respectively. The 1-, 5- and 10 year-survival rates for f/m were 87%/96%, 49%/76% and 31%/57%, respectively (p = 0.02). According to the Tang classification group A, B, and C OS was 118, 83 and 20 months, respectively (p = 0.0002).ConclusionThe Tang classification was found to be a significant prognostic factor, while the Ki67 index was not. Localized GCCs occurred equally in males and females, while disseminated GCCs were mostly seen in females. Median age of patients with localized disease and disseminated disease was identical. Cox regression analysis found Stage IV, focally positive synaptophysin and non-radical surgery as strongest negative prognostic factors.  相似文献   
102.
Structural and functional analysis of the reducing side of photosystem I   总被引:2,自引:0,他引:2  
Structural analysis of the reducing side of photosystem I (PSI) has been carried out using chemical cross-linking and monospecific antibodies. Incubation of PSI isolated from barley (Hordeum vulgare L.) with the hydrophilic cross-linking agent N-ethyl-3-[3-(dimethylamino) propyl]-carbodiimide leads to cross-linking of the PSI-D subunit with the PSI-E and PSI-H subunits. In the presence of ferredoxin, cross-linking results in the formation of cross-linked products composed of PSI-D, PSI-E and ferredoxin and in a block in steady state NADP+ photoreduction. No cross-linking of ferredoxin occurs at elevated ionic strength or using heat-denatured ferredoxin. Cross-linking of ferredoxin does not inhibit electron transfer from plastocyanin to methyl viologen. Steady state NADP+ photoreduction was analyzed in PSI or thyla-koids incubated with antibodies against individual PSI subunits. Incubation with antibodies against PSI-C, -H, -I, or -L had no effect on PSI activity, whereas antibodies against PSI-D or PSI-E had similar effects and caused a large decrease in activity. The results provide evidence that the PSI-D and PSI-E subunits are localized on the reducing side of PSI, forming a barrier between PSI-C and the stroma as well as a docking site for ferredoxin. The PSI-H subunit has an exposed, stromal domain but this does not appear to contribute to the ferredoxin docking.  相似文献   
103.
104.
The new species Penicillium discolor, frequently isolated from nuts, vegetables and cheese is described. It is characterised by rough, dark green conidia, synnemateous growth on malt agar and the production of the secondary metabolites chaetoglobosins A, B and C, palitantin, cyclopenin, cyclopenol, cyclopeptin, dehydrocyclopeptin, viridicatin and viridicatol. It also produces the mouldy smelling compounds geosmin and 2-methyl-isoborneol, and a series of specific orange to red pigments on yeast extract sucrose agar, hence the epithet discolor. P. discolor resembles P. echinulatum morphologically but on basis of the secondary metabolites is also related to P. expansum, P. solitum and P. crustosum.  相似文献   
105.
106.
107.
108.
109.
110.
Unilateral nuclear migration (UNM) is a striking deviation from the normal reciprocal exchange of nuclei in mating between otherwise compatible monokaryons in Basidiomycetes. UNM has rarely been subject to systematical investigation. Here, we examine the scientific history of UNM in Basidiomycetes and evaluate the explanations brought forward. We suggest that UNM could have an evolutionary role in mating-system reversion from tetrapolarity by assuring a more stable (reciprocal) nuclear migration.  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