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   1783篇
  免费   49篇
  国内免费   5篇
电工技术   13篇
综合类   1篇
化学工业   443篇
金属工艺   45篇
机械仪表   24篇
建筑科学   38篇
能源动力   94篇
轻工业   135篇
水利工程   8篇
石油天然气   14篇
无线电   158篇
一般工业技术   241篇
冶金工业   356篇
原子能技术   14篇
自动化技术   253篇
  2022年   25篇
  2021年   40篇
  2020年   34篇
  2019年   24篇
  2018年   44篇
  2017年   34篇
  2016年   34篇
  2015年   26篇
  2014年   31篇
  2013年   93篇
  2012年   64篇
  2011年   99篇
  2010年   74篇
  2009年   65篇
  2008年   79篇
  2007年   68篇
  2006年   47篇
  2005年   32篇
  2004年   41篇
  2003年   30篇
  2002年   46篇
  2001年   36篇
  2000年   36篇
  1999年   27篇
  1998年   76篇
  1997年   46篇
  1996年   45篇
  1995年   38篇
  1994年   37篇
  1993年   36篇
  1992年   28篇
  1991年   18篇
  1990年   23篇
  1989年   24篇
  1988年   32篇
  1987年   21篇
  1986年   17篇
  1985年   27篇
  1984年   21篇
  1983年   21篇
  1982年   19篇
  1981年   14篇
  1980年   13篇
  1979年   11篇
  1978年   17篇
  1977年   15篇
  1976年   24篇
  1975年   11篇
  1974年   12篇
  1973年   13篇
排序方式: 共有1837条查询结果,搜索用时 15 毫秒
111.
112.
This article deals with the design optimization of a squirrel-cage three-phase induction motor, selected as the driving power of spinning machines in the textile industry, using three newly developed versions of differential evolution (DE) algorithms called modified DE versions (CMDE, GMDE, and LMDE). Efficiency, which decides the operating or running cost of the motor (industry), is considered as the objective function. First, the algorithms are applied to design a general purpose motor with seven variables and nine performance-related parameters with their nominal values as constraints. To make the machine feasible, practically acceptable to serve in textile industries, and less costly to operate, certain constraints are modified in accordance with the demands of the spinning application. Comparison of the optimum designs with the industrial (existing) motor reveals that the motor designed by the proposed algorithms consumes less power input.  相似文献   
113.
PURPOSE: This study aimed to identify a dangerous new weapon capable of causing damage to the ocular and periocular regions. METHODS: The authors report two patients who had penetrating ocular injury in the past year because of homemade recreational potato guns. RESULTS: In one 14-year-old boy, projectiles from the firing of a potato gun resulted in orbital and cranial injuries that were life threatening with widespread fractures, marked disruption of facial structures, a cerebrospinal fluid fistula requiring bifrontal surgical repair, and loss of one eye. In a separate accident with a different potato gun, a 14-year-old boy who was wearing glasses at the time of injury had a sight-threatening perforating corneal laceration. CONCLUSION: Practitioners must be aware of the existence of these new, homemade unregulated devices. Information about the use and construction of these guns is widespread on the Internet, but no injuries resulting from these guns currently are documented in the medical literature.  相似文献   
114.
Cross-entropy has been recently proposed as a heuristic method for solving combinatorial optimization problems. We briefly review this methodology and then suggest a hybrid version with the goal of improving its performance. In the context of the well-known max-cut problem, we compare an implementation of the original cross-entropy method with our proposed version. The suggested changes are not particular to the max-cut problem and could be considered for future applications to other combinatorial optimization problems.  相似文献   
115.
Methane-air diffusion filtration combustion in a radiative round-jet burner was numerically investigated in this work.The purpose of this study was focused on t...  相似文献   
116.
The minimum common supergraph of two graphs, g1 and g2, is defined as the smallest graph that includes, as subgraphs, both g1 and g2. It is shown that minimum common supergraph computation can be solved by means of maximum common subgraph computation. For the latter problem, algorithms are known from the literature. It will also be shown that for a certain class of cost functions, the concept of graph edit distance is closely related with the minimum common supergraph.  相似文献   
117.
In addition to 2-methyl-4-heptanone, 6-methyl-5-hepten-2-one, and iridodials, the anal gland exudate of the dolichoderine ant,Tapinoma simrothi, contains 4-heptanone and 4-hydroxy-4-methyl-2-pentanone. The secretion functions as an alarm pheromone.  相似文献   
118.
This paper quantifies the detectability limits of infrared thermography (IRT) and ultraviolet fluorescence (UVF) techniques in the thickness measurements of the naval protective coatings applied on ship ballast tanks. The change in signal per unit thickness (25 μm) is used to describe each technique resolution, when using a pulsed-thermographic procedure and a UVF spectroscopic analysis. Furthermore, Tanimoto criterion in addition to a local signal-to-noise ratio (SNR) computation measure the revealability of pinholes, the IRT technique provides an 83% revealability while the UVF imaging has a 66% value. The goal of this work is to benchmark the novel UVF approach against that of the IRT procedures.  相似文献   
119.
Queens and workers are not morphologically differentiated in the primitively eusocial wasp, Ropalidia marginata. Upon removal of the queen, one of the workers becomes extremely aggressive, but immediately drops her aggression if the queen is returned. If the queen is not returned, this hyper-aggressive individual, the potential queen (PQ), will develop her ovaries, lose her hyper-aggression, and become the next colony queen. Because of the non-aggressive nature of the queen, and because the PQ loses her aggression by the time she starts laying eggs, we hypothesized that regulation of worker reproduction in R. marginata is mediated by pheromones rather than by physical aggression. Based on the immediate loss of aggression by the PQ upon return of the queen, we developed a bioassay to test whether the queen’s Dufour’s gland is, at least, one of the sources of the queen pheromone. Macerates of the queen’s Dufour’s gland, but not that of the worker’s Dufour’s gland, mimic the queen in making the PQ decrease her aggression. We also correctly distinguished queens and workers of R. marginata nests by a discriminant function analysis based on the chemical composition of their respective Dufour’s glands.  相似文献   
120.
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