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   321478篇
  免费   4602篇
  国内免费   1487篇
电工技术   5408篇
综合类   1152篇
化学工业   46106篇
金属工艺   11759篇
机械仪表   9446篇
建筑科学   7464篇
矿业工程   1970篇
能源动力   7645篇
轻工业   25455篇
水利工程   3641篇
石油天然气   5861篇
武器工业   49篇
无线电   35500篇
一般工业技术   60334篇
冶金工业   68915篇
原子能技术   7701篇
自动化技术   29161篇
  2021年   2562篇
  2020年   1844篇
  2019年   2319篇
  2018年   4255篇
  2017年   4573篇
  2016年   5177篇
  2015年   3422篇
  2014年   4984篇
  2013年   12866篇
  2012年   9394篇
  2011年   12403篇
  2010年   8452篇
  2009年   9799篇
  2008年   9939篇
  2007年   9953篇
  2006年   8542篇
  2005年   10512篇
  2004年   9748篇
  2003年   9042篇
  2002年   7619篇
  2001年   7635篇
  2000年   6814篇
  1999年   7328篇
  1998年   21438篇
  1997年   14746篇
  1996年   11008篇
  1995年   8052篇
  1994年   6903篇
  1993年   7004篇
  1992年   4606篇
  1991年   4446篇
  1990年   4331篇
  1989年   4290篇
  1988年   3988篇
  1987年   3580篇
  1986年   3566篇
  1985年   3890篇
  1984年   3532篇
  1983年   3309篇
  1982年   3144篇
  1981年   3211篇
  1980年   3209篇
  1979年   2888篇
  1978年   2964篇
  1977年   3704篇
  1976年   5309篇
  1975年   2509篇
  1974年   2417篇
  1973年   2442篇
  1972年   2058篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation.  相似文献   
2.
3.

Stability constants and formation enthalpies of supramolecular complexes of crown ethers and their cyclic and acyclic analogues are determined on the basis of experimental data obtained by different physicochemical methods in the terms of a general approach developed and implemented in the ChemEqui software package. The established regularities of variation of stability of complexes are discussed as dependent on the ligand structure, nature of the cation, solvent, and anion. The applicability of the suggested method of determining complexation selectivity is shown for multicomponent equilibria in solutions.

  相似文献   
4.
Lobster krill (Munida genus) represents an under‐valued crustacean frequently caught on European fishing banks. In this work, its sensory, microbiological and biochemical qualities were evaluated during chilled storage. Additionally, the effects of a prestorage antimelanosic treatment consisting of soaking in sodium metabisulphite (SMB) solutions at two different concentrations (0.25% and 0.75%) were also studied. SMB prestorage treatment provided lobster specimens that still exhibited acceptable sensory quality after 10 days of storage, while control specimens were unacceptable at that time. SMB treatment also resulted in a significant (P < 0.05) inhibition of microbial growth, mainly of Enterobacteriaceae, psychrotrophes and proteolytic bacteria. Low lipid oxidation levels were observed for all batches; however, a significantly higher (P < 0.05) retention of polyunsaturated fatty acids was found in SMB‐treated lobster, especially in the 0.75% SMB batch. The results presented here open the way to the potential commercialisation of currently under‐utilised lobster krill as a chilled product.  相似文献   
5.
6.
7.
We explore the possibility of characterizing sperm cells without the need to stain them using spectral and fluorescence lifetime analyses after multi-photon excitation in an insect model. The autofluorescence emission spectrum of sperm of the common bedbug, Cimex lectularius, was consistent with the presence of flavins and NAD(P)H. The mean fluorescence lifetimes showed smaller variation in sperm extracted from the male (tau m, τm = 1.54–1.84 ns) than in that extracted from the female sperm storage organ (tau m, τm = 1.26–2.00 ns). The fluorescence lifetime histograms revealed four peaks. These peaks (0.18, 0.92, 2.50 and 3.80 ns) suggest the presence of NAD(P)H and flavins and show that sperm metabolism can be characterized using fluorescence lifetime imaging. The difference in fluorescence lifetime variation between the sexes is consistent with the notion that female animals alter the metabolism of sperm cells during storage. It is not consistent, however, with the idea that sperm metabolism represents a sexually selected character that provides females with information about the male genotype.  相似文献   
8.
9.
10.
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