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   412740篇
  免费   5817篇
  国内免费   1386篇
电工技术   7704篇
综合类   349篇
化学工业   61994篇
金属工艺   14285篇
机械仪表   11871篇
建筑科学   11637篇
矿业工程   869篇
能源动力   11117篇
轻工业   43802篇
水利工程   3312篇
石油天然气   1835篇
武器工业   13篇
无线电   55388篇
一般工业技术   76614篇
冶金工业   74951篇
原子能技术   5568篇
自动化技术   38634篇
  2021年   2669篇
  2019年   2434篇
  2018年   3838篇
  2017年   3904篇
  2016年   4144篇
  2015年   3426篇
  2014年   5714篇
  2013年   19284篇
  2012年   10202篇
  2011年   14680篇
  2010年   11283篇
  2009年   12884篇
  2008年   13914篇
  2007年   14285篇
  2006年   12777篇
  2005年   11961篇
  2004年   11574篇
  2003年   11279篇
  2002年   10913篇
  2001年   11131篇
  2000年   10271篇
  1999年   10769篇
  1998年   24010篇
  1997年   17587篇
  1996年   13903篇
  1995年   10979篇
  1994年   9771篇
  1993年   9354篇
  1992年   7121篇
  1991年   6790篇
  1990年   6397篇
  1989年   6106篇
  1988年   5860篇
  1987年   4884篇
  1986年   4835篇
  1985年   5980篇
  1984年   5599篇
  1983年   4832篇
  1982年   4496篇
  1981年   4447篇
  1980年   4208篇
  1979年   4080篇
  1978年   3771篇
  1977年   4548篇
  1976年   6097篇
  1975年   3115篇
  1974年   3011篇
  1973年   2890篇
  1972年   2318篇
  1971年   2003篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
972.
973.
J. W. Schmidt  W. Heß 《Computing》1987,38(3):261-267
A necessary and sufficient criterion is presented under which the property of positivity carry over from the data set to rational quadratic spline interpolants. The criterion can always be satisfied if the occuring parameters are properly chosen.  相似文献   
974.
In the verified architecture microprocessor (VAMP) project we have designed, functionally verified, and synthesized a processor with full DLX instruction set, delayed branch, Tomasulo scheduler, maskable nested precise interrupts, pipelined fully IEEE compatible dual precision floating point unit with variable latency, and separate instruction and data caches. The verification has been carried out in the theorem proving system PVS. The processor has been implemented on a Xilinx FPGA. A shorter version of this article with the title “Instantiating uninterpreted functional units and memory system: functional verification of the VAMP” appeared in [8]. The work reported here was done while all the authors were with Saarland University.  相似文献   
975.
The evolving tree-analysis and applications   总被引:2,自引:0,他引:2  
In this paper, we enhance and analyze the Evolving Tree (ETree) data analysis algorithm. The suggested improvements aim to make the system perform better while still maintaining the simple nature of the basic algorithm. We also examine the system's behavior with many different kinds of tests, measurements and visualizations. We compare the ETree's performance against classical data analysis methods and very similar modern systems. We find that the ETree is a suitable method for unsupervised analysis of huge data sets.  相似文献   
976.
A thermodynamic analysis of a molten metal sulfide or oxide system begins with the equilibration of melts with a gas mixture containing the active species, for example, H2S/H2 with sulfides and CO2/CO with oxides. The Gibbs-Duhem equation is then integrated to calculate the activities of the components of interest. Because the sulfur pressures tend toward zero near the metal side of the binary and toward one bar at the metal sulfide side, integration in these systems can be difficult. An alternative approach using negative mole fractions is described and applied to the silver-silver sulfide system.  相似文献   
977.
This study investigates the phenotype of turbulent (Re = 5,200) and laminar (Re = 2,000) flow-generated Pseudomonas fluorescens biofilms. Three P. fluorescens strains, the type strain ATCC 13525 and two strains isolated from an industrial processing plant, D3-348 and D3-350, were used throughout this study. The isolated strains were used to form single and binary biofilms. The biofilm physiology (metabolic activity, cellular density, mass, extracellular polymeric substances, structural characteristics and outer membrane proteins [OMP] expression) was compared. The results indicate that, for every situation, turbulent flow-generated biofilms were more active (p < 0.05), had more mass per cm(2) (p < 0.05), a higher cellular density (p < 0.05), distinct morphology, similar matrix proteins (p > 0.1) and identical (isolated strains -single and binary biofilms) and higher (type strain) matrix polysaccharides contents (p < 0.05) than laminar flow-generated biofilms. Flow-generated biofilms formed by the type strain revealed a considerably higher cellular density and amount of matrix polysaccharides than single and binary biofilms formed by the isolated strains (p < 0.05). Similar OMP expression was detected for the several single strains and for the binary situation, not dependent on the hydrodynamic conditions. Binary biofilms revealed an equal coexistence of the isolated strains with apparent neutral interactions. In summary, the biofilms formed by the type strain represent, apparently, the worst situation in a context of control. The results obtained clearly illustrate the importance of considering strain variation and hydrodynamics in biofilm development, and complement previous studies which have focused on physical aspects of structural and density differences.  相似文献   
978.
In this work, we assessed the influence of coagulant residual activity and primary proteolysis on Cremoso Argentino cheese melting properties. For that purpose, we made Cremoso soft cheeses using different amounts of coagulant, and also obtained samples in which milk-clotting enzyme was inactivated. Primary proteolysis correlated with residual activity of coagulant in early stages of cheese ripening; however, it was similar in all cheeses after 30 days. The hydrolysis of caseins did not significantly affect the melting ability of the cheeses, expressed as the area increase after heating samples under standardized conditions. Samples with similar proximate composition showed some changes in meltability; those seemed related to pH evolution during ripening.  相似文献   
979.
Excessive power supply noise during test can cause overkill. This article discusses two models for supply noise in delay testing and their application to test compaction. The proposed noise models avoid complicated power network analysis, making them much faster than existing power noise analysis tools. can cause performance degradation and  相似文献   
980.
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