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   902篇
  免费   1篇
  国内免费   3篇
电工技术   2篇
综合类   1篇
化学工业   85篇
金属工艺   2篇
机械仪表   39篇
建筑科学   62篇
矿业工程   4篇
能源动力   2篇
轻工业   270篇
水利工程   10篇
石油天然气   39篇
无线电   32篇
一般工业技术   314篇
冶金工业   5篇
原子能技术   1篇
自动化技术   38篇
  2019年   1篇
  2012年   79篇
  2011年   131篇
  2010年   21篇
  2009年   13篇
  2008年   100篇
  2007年   74篇
  2006年   71篇
  2005年   65篇
  2004年   56篇
  2003年   50篇
  2002年   37篇
  2001年   35篇
  2000年   24篇
  1999年   20篇
  1998年   10篇
  1997年   19篇
  1996年   18篇
  1995年   11篇
  1994年   6篇
  1993年   8篇
  1992年   8篇
  1991年   8篇
  1990年   3篇
  1989年   6篇
  1988年   1篇
  1987年   1篇
  1986年   3篇
  1985年   5篇
  1984年   2篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1979年   3篇
  1978年   3篇
  1977年   1篇
  1976年   3篇
  1973年   1篇
  1972年   2篇
  1948年   2篇
排序方式: 共有906条查询结果,搜索用时 31 毫秒
1.
大量的高产油田已步入开发晚期,含水量骤增,采油量锐减。为保持地层压力高于原始压力而不分开阶段大量注水或注水不当的均会产生许多不良现象。应该在试采期内先研究产层地质情况,油藏与边外水系统的关系,然后分别计算某些区块,油藏段和地层物性不同的地带的注水量,合理利用地层水能量。  相似文献   
2.
3.
利用干气处理近井地带提高凝析气井的产能   总被引:1,自引:0,他引:1  
  相似文献   
4.
5.
6.
7.
Analysis of the Insect OS-D-Like Gene Family   总被引:9,自引:0,他引:9  
Insect OS-D-like proteins, also known as chemosensory (CSP) or sensory appendage proteins (SAP), are broadly expressed in various insect tissues, where they are thought to bind short to medium chain length fatty acids and their derivatives. Although their specific function remains uncertain, OS-D-like members have been isolated from sensory organs (including the sensillum lymph in some cases), and a role in olfaction similar to that of the insect odorant binding proteins (OBP) has been suggested for some. We have identified 15 new OS-D-like sequences: four from cDNA clones described herein and 11 from sequence databases. The os-d-like genes from the Anopheles gambiae, Apis mellifera, Drosophila melanogaster, and Drosophila pseudoobscura genomes typically have single, small introns with a conserved splice site. Together with all family members entered on GenBank, a total of 70 OS-D-like proteins, representing the insect orders Diptera, Dictyoptera, Hymenoptera, Lepidoptera, Orthoptera, and Phasmatodea, were analyzed. A neighbor joining distance phenogram identified several protein similarity classes that were characterized by highly conserved sequence motifs, including (A) N-terminal YTTKYDN(V/I)(N/D)(L/V)DEIL, (B) central DGKELKXX(I/L)PDAL, and (C) C-terminal KYDP. In contrast, three similarity classes were characterized by their diversion from these conserved motifs. The functional importance of conserved amino acid residues is discussed in relation to the crystal and NMR structures of MbraCSPA6.  相似文献   
8.
The ability to manipulate the intracellular environment within living cells and to monitor the cytosolic chemical changes which occur during cell stimulation has lead to major advances in our understanding of how cells read and respond to their environment. Perhaps the most powerful suite of techniques for achieving these dual objectives is based on the use of light (photons). Because cells are 'transparent', light has been used to both interrogate and manipulate the chemistry inside living cells, exploiting technical advances in both the physical and biochemical sciences. However, cells are neither transparent nor homogeneous with respect to their optical properties. The interface between light and the living cell cytoplasm thus represent an important, yet largely ignored, interface. There has been no review of the optical properties of cytoplasm and little discussion about how the optical properties of living cytoplasm influence the outcome of such measurements and manipulations. In this short review, we discuss the importance of understanding the optical properties of cytoplasm for such techniques and how imperfections in experimental interpretation can arise.  相似文献   
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