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   1521篇
  免费   12篇
电工技术   20篇
化学工业   92篇
金属工艺   3篇
机械仪表   2篇
建筑科学   25篇
能源动力   3篇
轻工业   22篇
无线电   7篇
一般工业技术   64篇
冶金工业   1252篇
自动化技术   43篇
  2022年   2篇
  2021年   4篇
  2020年   2篇
  2019年   4篇
  2018年   3篇
  2017年   6篇
  2016年   5篇
  2015年   8篇
  2014年   8篇
  2013年   12篇
  2012年   16篇
  2011年   8篇
  2010年   15篇
  2009年   15篇
  2008年   20篇
  2007年   17篇
  2006年   13篇
  2005年   13篇
  2004年   11篇
  2003年   13篇
  2002年   10篇
  2001年   9篇
  2000年   3篇
  1999年   43篇
  1998年   392篇
  1997年   221篇
  1996年   163篇
  1995年   78篇
  1994年   71篇
  1993年   75篇
  1992年   13篇
  1991年   15篇
  1990年   20篇
  1989年   21篇
  1988年   24篇
  1987年   22篇
  1986年   12篇
  1985年   17篇
  1984年   4篇
  1983年   4篇
  1982年   6篇
  1981年   7篇
  1980年   10篇
  1978年   6篇
  1977年   21篇
  1976年   61篇
  1975年   4篇
  1955年   1篇
  1930年   1篇
  1929年   1篇
排序方式: 共有1533条查询结果,搜索用时 15 毫秒
71.
72.
Managing object-oriented projects is subtly different than managing non-object-oriented ones. Object-oriented projects employ a different unit of decomposition, they encourage an incremental and iterative process, and quantitatively, they demand different kinds of measures. This paper examines the nature of managing object-oriented projects, and offers a variety of lessons learned from a number of real projects.Portions of this article are adapted from [Booch 1995].  相似文献   
73.
74.
75.
Capacitative Ca2+ entry and the regulation of smooth muscle tone   总被引:1,自引:0,他引:1  
In many non-excitable cells, activation of phospholipase C-linked receptors results in a biphasic increase in the cytosolic Ca2+ concentration; an initial transient increase, owing to the release of Ca2+ from the endoplasmic/sarcoplasmic reticulum (ER/SR), is followed by a much smaller but sustained elevation, which often involves capacitative Ca2+ entry, where depletion of Ca2+ within the ER signals the opening of store-operated Ca2+ channels in the plasma membrane. However, in excitable cells such as smooth muscle, the role of capacitative Ca2+ entry is less clear and the main Ca2+ entry mechanisms responsible for sustained cellular activation have been considered to be either voltage-operated or receptor-operated Ca2+ channels. Although store-regulated Ca2+ entry was known to occur following agonist activation of smooth muscle, it was believed to be important only for the re-filling of the depleted SR and not as a source of activator Ca2+ for the contractile mechanisms. Here, Alan Gibson, Ian McFadzean, Pat Wallace and Christopher Wayman review recent evidence that capacitative Ca2+ entry might indeed be important for the regulation of smooth muscle tone, and that it might provide an important for pharmacological intervention.  相似文献   
76.
77.
78.
The aim of this work was to establish appropriate conditions for immobilising Candida rugosa lipase on a low‐cost inorganic matrix, hydrous niobium oxide, using a multivariate statistical approach. A 23 full factorial design was employed to determine the effects of support activation with glutaraldehyde (concentration 2.5–4.5%, pH 7–10) and lipase loading (200‐700 U g?1 matrix) on the hydrolytic and synthetic activities of the immobilised derivatives. From the results the following conditions were established: lipase loading of 450 U g?1 matrix and niobium oxide activation with glutaraldehyde at a concentration of 2.5% and pH 8. Under these conditions, high activity recovery (47.21%) and esterification yield (86.90%) were attained. The results also show that hydrous niobium oxide can be a valid alternative to replace high‐cost, commercially available inorganic matrices such as controlled pore silica. Copyright © 2006 Society of Chemical Industry  相似文献   
79.
Recently, mutations in the Met tyrosine kinase receptor have been identified in both hereditary and sporadic forms of papillary renal carcinoma. We have introduced the corresponding mutations into the met cDNA and examined the effect of each mutation in biochemical and biological assays. We find that the Met mutants exhibit increased levels of tyrosine phosphorylation and enhanced kinase activity toward an exogenous substrate when compared with wild-type Met. Moreover, NIH 3T3 cells expressing mutant Met molecules form foci in vitro and are tumorigenic in nude mice. Enzymatic and biological differences were evident among the various mutants examined, and the somatic mutations were generally more active than those of germ-line origin. A strong correlation between the enzymatic and biological activity of the mutants was observed, indicating that tumorigenesis by Met is quantitatively related to its level of activation. These results demonstrate that the Met mutants originally identified in human papillary renal carcinoma are oncogenic and thus are likely to play a determinant role in this disease, and these results raise the possibility that activating Met mutations also may contribute to other human malignancies.  相似文献   
80.
Alterations of chromosome 8, including deletions of 8p, occur frequently in many tumors. In this study, fluorescence in situ hybridization was used to study the relationship between 8p deletions, 8q gains, and phenotype in bladder cancer. Cells from 87 tumors were examined by dual-labeling fluorescence in situ hybridization with a centromere 8 probe (pJM12) and P1 probes for 8p22, 8p12, 8q12, and 8q24. Both 8p22 deletions and 8q24 gains were strongly associated with tumor phenotype. There was a marked difference in 8p22 deletions between noninvasive (pTa) tumors (3/33) and minimally invasive (pT1) tumors (8/19; P = 0.005) whereas there was no significant difference between pT1 and muscle-invasive (pT2-4) tumors (19/35; P = 0.3926). Six tumors with 8p22 deletion were examined at 8p12. Three of these tumors showed no 8p12 deletion, narrowing down the site of a putative tumor suppressor gene distal to 8p12. In one other case, there was a marked increase in 8p12 copy number (> 40 per cell; amplification), suggesting the presence of an oncogene involved in bladder cancer at 8p12. The marked difference in 8p22 deletions between noninvasive (pTa) and minimally invasive (pT1) tumors is consistent with a role of a putative tumor suppressor gene on 8p for development of invasive tumor phenotype.  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