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   104134篇
  免费   2583篇
  国内免费   1286篇
电工技术   1862篇
综合类   3670篇
化学工业   14959篇
金属工艺   6172篇
机械仪表   4172篇
建筑科学   3695篇
矿业工程   1344篇
能源动力   1578篇
轻工业   4936篇
水利工程   1624篇
石油天然气   1865篇
武器工业   200篇
无线电   11343篇
一般工业技术   18919篇
冶金工业   3756篇
原子能技术   439篇
自动化技术   27469篇
  2024年   111篇
  2023年   368篇
  2022年   680篇
  2021年   923篇
  2020年   732篇
  2019年   596篇
  2018年   14964篇
  2017年   14012篇
  2016年   10505篇
  2015年   1467篇
  2014年   1311篇
  2013年   1376篇
  2012年   4382篇
  2011年   10820篇
  2010年   9473篇
  2009年   6712篇
  2008年   7826篇
  2007年   8937篇
  2006年   1242篇
  2005年   2177篇
  2004年   1730篇
  2003年   1703篇
  2002年   1074篇
  2001年   554篇
  2000年   644篇
  1999年   593篇
  1998年   455篇
  1997年   394篇
  1996年   363篇
  1995年   302篇
  1994年   264篇
  1993年   181篇
  1992年   144篇
  1991年   105篇
  1990年   65篇
  1989年   49篇
  1988年   64篇
  1987年   32篇
  1968年   43篇
  1967年   33篇
  1966年   42篇
  1965年   44篇
  1963年   28篇
  1960年   30篇
  1959年   37篇
  1958年   37篇
  1957年   36篇
  1956年   34篇
  1955年   63篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
We constructed a probabilistic simulator that allows all the events in population dynamics such as death, birth, mutation, and suppression/stimulation to be described by probabilistic rules. The simulator also facilitates a lattice used for expressing distribution and diversity (number of distinct strains) of quasispecies. The simulator is used to investigate the diversity threshold in HIV and T-cell interaction. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008  相似文献   
82.
83.
Six triorganotin(IV) complexes of the type {(R3Sn)2[C3S3(COO)2]}n (R = C6H5 1; n-Bu 2; PhCH2 4; p-F-PhCH2 5; o-F-PhCH2 6) and {(R3Sn)2[C3S3(COO)2]}n·[EtOH] (R = Me 3) have been synthesized by the reaction of bis(carboxymethyl)trithiocarbonate with triorganotin(IV) chloride in the presence of sodium ethoxide. All complexes were characterized by elemental analysis IR, 1H, 13C and 119Sn NMR spectroscopy. Except for 4–6, all complexes were also characterized by X-ray crystallography. The X-ray date revealed that complexes 1–3 show two-dimensional network polymeric structure in which the geometries of tin atoms are trigonal bipyramid with the axial positions occupied by carboxylic oxygen atoms.  相似文献   
84.
The reaction of [Cu(sac)2(H2O)4] · 2H2O with 2-methylpyrazine (mpyz) leads two complexes, concomitant crystallization of a mononuclear complex [Cu(sac)2(mpyz)(H2O)2] (1) and a polymeric complex [Cu(sac)2(μ-mpyz)]n (2). Both complexes have been characterized by elemental analyses, magnetic measurements, FT-IR and ESR, TG-DTA and single-crystal X-ray diffraction analyses. Single-crystal X-ray analyses show that complex 1 consists of discrete molecules in which the copper(II) ions exhibits a square-pyramidal coordination geometry. The individual molecules of 1 are connected into a hydrogen-bonded chain structure, which is further assembled to form a three-dimensional network by ππ stacking interactions. Complex 2 is an 1D coordination polymer in which copper(II) centers are bridged by the mpyz ligand. The chains are further assembled to form two-dimensional frameworks by ππ and C–H···π stacking interactions.  相似文献   
85.
86.
87.
88.
Real world applications of a decision model of relationships between goals based on fuzzy relations are presented. In contrast to other approaches the relationships between decision goals or criteria for each decision situation are represented and calculated explicitly. The application fields are decision making for financial services and optimization of production sequences in car manufacturing.  相似文献   
89.
90.
Composition Group Vector Space (CGVS) method for estimating melting and boiling point T m , T b of organic compound has been proposed, and the principle of this method has been elucidated. The models for estimating T m , T b have been established and the numerical values of relative parameters have been presented. The average percentage deviations of T m , T b estimation are 7.53 and 1.58, respectively, which show that the present method demonstrates significant improvement in applicability to predict the above properties, compared to conventional group methods.  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