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   3856篇
  免费   3篇
电工技术   6篇
综合类   2篇
化学工业   37篇
金属工艺   7篇
机械仪表   4篇
建筑科学   5篇
矿业工程   5篇
能源动力   7篇
轻工业   24篇
水利工程   1篇
石油天然气   1篇
无线电   25篇
一般工业技术   34篇
冶金工业   3665篇
原子能技术   2篇
自动化技术   34篇
  2022年   5篇
  2020年   2篇
  2018年   1篇
  2017年   2篇
  2016年   7篇
  2015年   1篇
  2014年   7篇
  2013年   6篇
  2012年   11篇
  2011年   9篇
  2010年   7篇
  2009年   11篇
  2008年   7篇
  2007年   9篇
  2006年   5篇
  2005年   9篇
  2004年   5篇
  2003年   15篇
  2002年   6篇
  2001年   3篇
  2000年   12篇
  1999年   128篇
  1998年   1265篇
  1997年   689篇
  1996年   410篇
  1995年   248篇
  1994年   194篇
  1993年   254篇
  1992年   38篇
  1991年   50篇
  1990年   43篇
  1989年   32篇
  1988年   25篇
  1987年   41篇
  1986年   24篇
  1985年   24篇
  1984年   1篇
  1983年   7篇
  1982年   11篇
  1981年   16篇
  1980年   19篇
  1979年   1篇
  1978年   6篇
  1977年   68篇
  1976年   115篇
  1975年   4篇
  1971年   1篇
  1966年   1篇
  1965年   1篇
  1955年   1篇
排序方式: 共有3859条查询结果,搜索用时 352 毫秒
81.
Late occurrence of cytomegalovirus (CMV) disease after day 100 after bone marrow transplantation has become an increasing problem; whether a quantitative measurement of CMV DNA in plasma by polymerase chain reaction (P-PCR) could be predictive of such disease was investigated. In a prospective study, 117 subjects undergoing allogeneic marrow transplantation were followed for 120 days with weekly CMV blood cultures, with day 35 bronchoalveolar lavage CMV cultures, with weekly CMV P-PCR, and with clinical follow-up for an additional 1-2 years. Despite preemptive ganciclovir, CMV disease occurred in 9% of subjects, with a median time of onset of 176 days. Quantitative CMV P-PCR was associated with the late development of CMV disease (P = .01). Of 43 subjects with positive P-PCR results, 23% developed CMV disease, but no disease occurred in the 74 subjects with negative P-PCR (P < .001), despite the fact that 22% had CMV isolated from lung lavage fluid and 32% had CMV isolated from blood.  相似文献   
82.
83.
84.
The interactive editing and contouring of empirical fields   总被引:2,自引:0,他引:2  
A system for the interactive editing and contouring of surfaces derived from empirical fields is described. The approach taken begins with the representation of a field as a general-order, nonuniform, tensor-product, B-spline surface. It provides an interactive display for editing the surface by control-vertex manipulation and a contouring algorithm that is specifically designed for the fast and robust contouring of B-spline surfaces. Interactive editing of the resulting model is feasible because of the local nature of editing changes when B-splines are used. The use of nonuniform B-splines gives the flexibility required to model highly irregular data efficiently  相似文献   
85.
The macrophage colony-stimulating factor receptor and several other hematopoietic growth factor receptors induce the tyrosine phosphorylation of a 145- to 150-kD protein in murine cells. We have previously cloned a cDNA for the murine 150-kD protein, SHIP, and found that it encodes a unique signaling intermediate that binds the SHC PTB domain through at least one tyrosine phosphorylated (NPXY) site in the carboxyl-terminal region. SHIP also contains several potential SH3 domain-binding sites, an SH2 domain for binding other tyrosine phosphorylated proteins, and an enzymatic activity that removes the phosphate from the 5 position of phosphatidylinositol 3,4,5-phosphate or from inositol 1,3,4,5-phosphate. SHIP has a negative effect on cell growth and therefore loss or modification may have profound effects on hematopoietic cell development. In this study, we have cloned a cDNA for human SHIP and examined mRNA and protein expression of SHIP and related species in bone marrow and blood cells. Flow cytometry indicates that at least 74% of immature CD34+ cells express SHIP cross-reacting protein species, whereas within the more mature population of CD33+ cells, only 10% of cells have similar expression. The majority of T cells react positively with the anti-SHIP antibodies, but significantly fewer B cells are positive. Immunoblotting detects up to seven different cross-reacting SHIP species, with peripheral blood mononuclear cells exhibiting primarily a 100-kD protein and a CD34+ acute myeloblastic leukemia expressing mainly 130-kD and 145-kD forms of SHIP. Overall, these results indicate that there is an enormous diversity in the size of SHIP or SHIP-related mRNA and protein species. Furthermore, the expression of these protein species changes according to both the developmental stage and differentiated lineage of the mature blood cell.  相似文献   
86.
A simple, rapid, accurate and reproducible capillary electrophoretic method was developed for the assay of glycyrrhizin and glycyrrhetinic acid in traditional Chinese medicinal preparations. The buffer solution used in this method was acetonitrile and 0.02 M sodium dihydrogen-phosphate solution adjusted to pH 7.5 with 0.05 M sodium hydroxide. The linear calibration range was 0.04-2.00 mg/ml (r = 0.9988) for glycyrrhizin and 0.007-0.35 mg/ml (r = 0.9985) for glycyrrhetinic acid and recoveries were 98.1-101.3% for glycyrrhizin and 98.5-101.4% for glycyrrhetinic acid. The relative standard deviations were 1.02% (n = 6) for glycyrrhizin and 0.91% (n = 6) for glycyrrhetinic acid. The content of these two acids in Glycyrrhizae Radix and Glycyrrhizae Radix-containing Chinese medicinal preparations was successfully determined within 10 min.  相似文献   
87.
88.
89.
90.
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