全文获取类型
收费全文 | 369000篇 |
免费 | 10901篇 |
国内免费 | 4885篇 |
专业分类
电工技术 | 10660篇 |
技术理论 | 6篇 |
综合类 | 6469篇 |
化学工业 | 54382篇 |
金属工艺 | 20509篇 |
机械仪表 | 18363篇 |
建筑科学 | 14179篇 |
矿业工程 | 5411篇 |
能源动力 | 8600篇 |
轻工业 | 24440篇 |
水利工程 | 4977篇 |
石油天然气 | 12681篇 |
武器工业 | 813篇 |
无线电 | 40341篇 |
一般工业技术 | 69810篇 |
冶金工业 | 47482篇 |
原子能技术 | 7062篇 |
自动化技术 | 38601篇 |
出版年
2023年 | 2162篇 |
2022年 | 4044篇 |
2021年 | 5821篇 |
2020年 | 4462篇 |
2019年 | 4245篇 |
2018年 | 13720篇 |
2017年 | 14681篇 |
2016年 | 10390篇 |
2015年 | 6407篇 |
2014年 | 8033篇 |
2013年 | 14785篇 |
2012年 | 13855篇 |
2011年 | 21720篇 |
2010年 | 19026篇 |
2009年 | 18406篇 |
2008年 | 18098篇 |
2007年 | 19849篇 |
2006年 | 11016篇 |
2005年 | 13368篇 |
2004年 | 9874篇 |
2003年 | 9300篇 |
2002年 | 7796篇 |
2001年 | 7117篇 |
2000年 | 7016篇 |
1999年 | 7352篇 |
1998年 | 13426篇 |
1997年 | 9829篇 |
1996年 | 8090篇 |
1995年 | 6085篇 |
1994年 | 5438篇 |
1993年 | 4829篇 |
1992年 | 3878篇 |
1991年 | 3528篇 |
1990年 | 3215篇 |
1989年 | 3245篇 |
1988年 | 3056篇 |
1987年 | 2544篇 |
1986年 | 2430篇 |
1985年 | 2783篇 |
1984年 | 2556篇 |
1983年 | 2388篇 |
1982年 | 2130篇 |
1981年 | 2231篇 |
1980年 | 2054篇 |
1979年 | 2140篇 |
1978年 | 2121篇 |
1977年 | 2366篇 |
1976年 | 3188篇 |
1975年 | 1833篇 |
1973年 | 1772篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
941.
The authors have exploited the ideas used in vector quantisation for error recovery of scalar quantised LSFs. The good performance of this method has provided high resistance of the LSFs to channel errors, outperforming other schemes by, possibly, a considerable margin. Better objective and subjective performances were obtained with this new method which obviates the need for more powerful FEC schemes for transmission over noisy channels.<> 相似文献
942.
Enzyme-linked immunosorbent assay and flow cytometric methods to screen hybridoma culture supernatants for antibodies to bovine neutrophils (surface antigen-specific) were optimized. Sensitivity of the 2 methods was compared. A panel of 14 murine monoclonal antibodies (MAB) to surface antigens of bovine polymorphonuclear neutrophilic leukocytes (neutrophils) was produced by hybridoma technology, and their isotypes were determined by whole-cell ELISA. Monoclonal antibody reactivity with neutrophils, eosinophils, and lymphocytes isolated on phosphate-buffered saline solution and on Ficoll-sodium diatrizoate were compared. Biochemical characterization of antigens recognized by MAB was performed by immunoblot analysis. Neutrophil plasma membranes were isolated on sucrose gradients (20, 32, and 50%) and purified for polypeptide characterization. Neutrophil surface proteins were characterized by external labeling with 125I. The flow cytometric method was proven to be more sensitive and rapid than ELISA to screen hybridoma supernatants. This method allowed light-scatter gating of live neutrophil populations for analysis, which eliminated nonspecific binding of antibodies to contaminating cells and dead neutrophils. The optimal conditions for flow cytometric analyses were 5 x 10(5) neutrophils and 1 micrograms of fluorescein-labeled F(ab')2/assay as the second antibody. The optimal conditions for hybridoma screening by ELISA were neutrophil concentration of 2.5 x 10(5)/well, using a 96-well polystyrene microtitration plate as solid support, and 2,2'-azino-di[3-ethyl-benzthiazoline sulfonate (6)] with H2O2 as the chromatogenic substrate. Tissue culture plates as solid support and 3,3', 5,5'-tetramethyl benzidine, with H2O2 as the chromogenic substrate, were equally as sensitive. Panel MAB reacted differently with neutrophils, eosinophils, and lymphocytes. Isolation of these cells from blood on Ficoll-sodium diatrizoate generally did not alter MAB reactivity. Coomassie blue-stained gels of neutrophil plasma membrane proteins contained about 25 polypeptide bands, 13 of which were major bands. Autoradiography revealed about 11 surface proteins, 5 of which were heavily labeled with 125I. Monoclonal antibody S7G8 identified a 65-kd protein and MAB S8G10 identified 65- and 70-kd proteins. On the basis of molecular weight, MAB S7G8 and S8G10 are comparable to human CD15, CD16, and CD64 molecules. The MAB generated in this study are potential candidates to discern bovine neutrophil function and heterogeneity. 相似文献
943.
The urinary catheter is one of the most frequently used medical devices and has a long and intriguing history of development. This paper describes the catheter from its simple beginnings through the subtle but important changes it has undergone paralleling the advances in plastics technology witnessed this century. The changes have not been without controversy and the recent association of catheters with tissue toxicity, which has forced the implementation of strict guidelines for their manufacture and use, is described. 相似文献
944.
945.
A menu-driven interactive graphics software package has been developed for use as an instructional aid for the electric machines course in the electrical engineering curriculum. The main purpose of this tool is to give the students a clearer understanding of the basics of the operation of rotating electric machines. The animation program was developed for displaying live and rotating diagrams depicting different modes of operation of synchronous generators. Different parts are identified with different colors. The interaction of the magnetic poles on the stator and on the rotor, and the relative spatial positions and time variations of the magnetic and electric quantities are demonstrated through moving images. The software features are described 相似文献
946.
947.
The mortality rate after traumatic brain injury in children ranges between 2.5% and 21%. Standardized diagnostic procedures and therapeutic strategies for the management of traumatic brain damage are presented in this article. Children with traumatic cerebral lesions have a better clinical outcome than head-injured adults. Optimized medical management and intensive rehabilitation may help to reduce the frequency of mental retardation and physical disability following such injuries in children. 相似文献
948.
949.
The paper deals with methods facilitating the preparation of oncospheres of the cestode, Hymenolepis diminuta, for experimental studies. Described in detail are procedures for the infection of the definitive hosts with the oncospheres; collection and artificial hatching of oncospheres; purification of hexacanths; preparation of extracts from the hexacanths; and preparation of hexacanths for electronmicroscopic studies. 相似文献
950.