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   7766篇
  免费   19篇
  国内免费   2篇
电工技术   9篇
综合类   3篇
化学工业   169篇
金属工艺   10篇
机械仪表   10篇
建筑科学   34篇
矿业工程   2篇
能源动力   38篇
轻工业   134篇
水利工程   5篇
石油天然气   5篇
无线电   69篇
一般工业技术   115篇
冶金工业   7082篇
原子能技术   8篇
自动化技术   94篇
  2024年   10篇
  2023年   6篇
  2022年   13篇
  2021年   19篇
  2020年   14篇
  2019年   18篇
  2018年   22篇
  2017年   18篇
  2016年   12篇
  2015年   8篇
  2014年   20篇
  2013年   43篇
  2012年   36篇
  2011年   20篇
  2010年   22篇
  2009年   16篇
  2008年   23篇
  2007年   27篇
  2006年   35篇
  2005年   29篇
  2004年   26篇
  2003年   32篇
  2002年   26篇
  2001年   16篇
  2000年   24篇
  1999年   235篇
  1998年   2378篇
  1997年   1329篇
  1996年   841篇
  1995年   438篇
  1994年   356篇
  1993年   436篇
  1992年   49篇
  1991年   54篇
  1990年   65篇
  1989年   52篇
  1988年   71篇
  1987年   67篇
  1986年   62篇
  1985年   53篇
  1984年   14篇
  1983年   25篇
  1982年   39篇
  1981年   41篇
  1980年   75篇
  1979年   20篇
  1978年   22篇
  1977年   154篇
  1976年   303篇
  1975年   21篇
排序方式: 共有7787条查询结果,搜索用时 15 毫秒
991.
The major penetrating membrane glycoprotein (band 3) was isolated from En(a-) and normal human erythrocytes. The two proteins differed only in carbohydrate composition. Band 3 from En(a-) erythrocytes contained greater amounts of galactose and N-acetyl-glucosamine. The loss of the sialoglycoprotein sialotetrasaccharides in the En(a-) cell is not compensated by the appearance of these units in band 3 of En(a-) erythrocytes.  相似文献   
992.
The decline (half-life) of maternally acquired antibodies of two different specificities (diphtheria and tetanus) was studied in rats. Essentially similar half-lives for antibody of each specificity were found in young rats from the same litter. In contrast, half-lives varied from 2 to 10 days in individuals of different litters. Significant differences in half-lives were demonstrated in young rats possessing markedly different initial titres of antibodies of the two specificities. It was established that there was a relationship between the half-life and the initial titre of antibody of each specificity which could be described by a rectangular hyperbola. These findings are in close aggreement with previous studies in human infants.  相似文献   
993.
994.
Using a sensitive radioimmunoassay we have studied the regional distribution of substance P. The level of substance P is higher in the mesencephalon, hypothalamus and preoptic area than in other regions of the brain. Substance P is found in especially high concentrations in the reticular part of the substantia nigra and the interpeduncular nucleus. It is present in large amounts in several septal, preoptic and hypothalamic nuclei as well.  相似文献   
995.
The patterns of expression of eight multilocous isozyme systems were investigated in the differentiated adult tissues and the early embryonic stages (0-210 hours after fertilization) of the green sunfish, Lepomis cyanellus. Enzymes encoded by approximately 23 gene loci were resolved by starch-gel electrophoresis and detected by specific histochemical staining. The developmental patterns of these isozyme systems appear to be the result of the diffential expression of the multiple gene loci. Isozymic forms of glucoseophosphate isomerase (GPI-A2), malate dehydrogenase (MDH-A2), and creatine kinase (CK-C2) were present in most differentiated tissues, in the unfertilized eggs, and in all stages of embryonic development. Closely homologous forms of these isozymes (GPI-B2, MDH-B2, and CK-A2) were expressed predominantly in skeletal muscle and were first detected at around the time of hatching (38-42 hours). The similar temporal and spatial patterns of gene expressions for the GPI, LDH, MDH, and CK loci suggest that the duplicates loci encoding enzymes, diverged in their regulation to patterns of differential gene expression which are similar for each enzyme system.  相似文献   
996.
Geometric superresolution by code division multiplexing   总被引:2,自引:0,他引:2  
In many highly resolved optical systems the resolution is limited not by the optics but by the CCD's nonzero pixel size. As a result, overall resolution is decreased. Here we propose a novel approach to enhancing resolution beyond the limit set by the CCD's pixels. This method does not involve additional mechanical elements, such as those used for microscans. In this scheme neither the CCD nor additional elements are moved. The geometric superresolving procedure is based on code-division multiplexing, with all its inherent benefits, such as relative noise immunity to single-tone interference. A setup is proposed for coherent and incoherent illumination, with slight modifications for the latter. A theoretical analysis of the setup is presented and compared with empirical results. This scheme is shown to enhance one-dimensional image resolution with the use of only a simple mask that doubles image resolution. This method can easily be expanded to two-dimensional images and to resolution-enhancement factors greater than 2.  相似文献   
997.
998.
999.
1000.
A three-point flexure test was used to evaluate the effects of chemical surface treatments on the performance of adhesively-bonded structures of Ti6A14V. A single adherend/adhesive structure rather than a double adherend sandwich configuration is shown to be sensitive to pre-bonding adherend surface treatments. Data is presented which relates mechanical properties with chemically treated adherend surfaces. Photoelastic isochromatic fringes were recorded simultaneously with the flexure test as a means to monitor stress distribution, failure initiation, and crack propagation.  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