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   1181篇
  免费   58篇
  国内免费   2篇
电工技术   7篇
综合类   2篇
化学工业   333篇
金属工艺   29篇
机械仪表   24篇
建筑科学   42篇
矿业工程   6篇
能源动力   30篇
轻工业   179篇
水利工程   7篇
石油天然气   5篇
无线电   91篇
一般工业技术   225篇
冶金工业   140篇
原子能技术   4篇
自动化技术   117篇
  2024年   5篇
  2023年   26篇
  2022年   70篇
  2021年   68篇
  2020年   27篇
  2019年   40篇
  2018年   50篇
  2017年   49篇
  2016年   46篇
  2015年   28篇
  2014年   42篇
  2013年   88篇
  2012年   66篇
  2011年   79篇
  2010年   55篇
  2009年   52篇
  2008年   43篇
  2007年   43篇
  2006年   49篇
  2005年   24篇
  2004年   19篇
  2003年   27篇
  2002年   23篇
  2001年   10篇
  2000年   9篇
  1999年   13篇
  1998年   16篇
  1997年   9篇
  1996年   15篇
  1995年   14篇
  1994年   12篇
  1993年   12篇
  1992年   8篇
  1991年   3篇
  1990年   8篇
  1989年   6篇
  1988年   6篇
  1987年   5篇
  1986年   11篇
  1985年   9篇
  1984年   5篇
  1983年   9篇
  1982年   10篇
  1981年   4篇
  1980年   4篇
  1979年   4篇
  1977年   3篇
  1976年   4篇
  1975年   3篇
  1971年   2篇
排序方式: 共有1241条查询结果,搜索用时 0 毫秒
1.
The increasing complecity of many expert system application areas calls for the integration of the knowledge of multiple experts. The use of multiple experts introduces some interesting new problems during the process of knowledge acquisition. The problems are further complicated when the experts are geographically dispersed or unavailable for face-to-face interactions.

This article discusses the motivations for acquiring the knowledge of multiple experts, the problems related to knowledge acquisition, new issues that arise whens multiple experts interact, solutions that can be brought to bear in building multiple expert systems (particularly when experts are geographically dispersed), and new tools for knowledge engineers to use when dealing with multiple experts.  相似文献   

2.
Seven hundred three members of the Society for Industrial and Organizational Psychology indicated agreement or disagreement with 49 propositions regarding cognitive ability tests in organizations. There was consensus that cognitive ability tests are valid and fair, that they provide good but incomplete measures, that different abilities are necessary for different jobs, and that diversity is valuable. Items dealing with the unique status of cognitive ability were most likely to generate polarized opinions. A 2-factor model, classifying items as those reflecting societal concerns over the consequences of ability testing and those reflecting an emphasis on the unique status of "g," fit the data well, and these factors proved especially important for predicting responses to the more controversial items. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
3.
The measured plastic deformation of Mg-PSZ under stress contains contributions from both transformation and microcracking. A method is described to separate the contributions from transformation and microcracking for samples deformed in uniaxial tension. Such a separation enables the ratio of the longitudinal to transverse strains arising from the transformation to be estimated. The results are compared to the predictions of the shear–dilatation model of Chen and Reyes-Morel. Serious discrepancies are found between the experimental results and the predictions of the model and the possible reason for this is discussed.  相似文献   
4.
A rapid and easy analysis method for polymers is presented. The method involves sample preparation by SFE, separation of the extracted compounds by SFC and simultaneous quantitative detection by FID, as well as identification of unknowns by MS. The applications illustrate how structural research work and routine polymer analysis can be done with this time saving method.  相似文献   
5.
Genotoxic effect and hepatic microsomal monooxygenase activities were assessed in mice treated with Acid Green 16 (single i.p. injection at dose 75 mg/kg) superimposed on prolonged ethanol consumption (10% solution in drinking water for 2-4 months). Treatment of mice with Acid Green 16 led to an increased frequency of micronucleated erythrocytes in bone marrow. In animals pretreated with ethanol the frequency of micronucleated erythrocytes, produced by Acid Green 16, was significantly higher. The changes in frequency of micronucleated erythrocytes were accompanied by the enhanced activity of microsomal monooxygenases manifested by higher activity of 7-ethoxycoumarin o-deethylase (the level of cytochrome P-450 was not altered). The obtained results showed that ethanol tended to increase the genotoxic effect of Acid Green 16. However, the slight inductive effect of ethanol on microsomal monooxygenases did not provide clear evidence that the genotoxic effect of Acid Green 16 was associated with ethanol stimulation of the metabolic activation of the dye in the liver.  相似文献   
6.
J. Zawadzki  M. Wi?niewski 《Carbon》2002,40(1):119-124
The interactions of NO with carbon and carbon-supported catalysts have been investigated by means Fourier transform infrared spectroscopy. Nitric oxide direct decomposition over carbon-supported catalysts (Cu, Pt) was studied in a temperature ranging from 473 to 623 K. NO conversion increased with increasing reaction temperature in the whole temperature range. The carbon-supported Pt catalyst has a very high activity for the decomposition of NO in the absence of oxygen. As a result of NO chemisorption isocyanate (-NCO) species on the surface of carbon containing Cu were observed. When the reaction temperature was increased, the -NCO band at 2229 cm−1 became more intense.  相似文献   
7.
The present study aimed to synthesize novel polycationic polymers composed of N-substituted L-2,3-diaminopropionic acid residues (DAPEGs) and investigate their cell permeability, cytotoxicity, and DNA-binding ability. The most efficient cell membrane-penetrating compounds (O2Oc-Dap(GO2)n-O2Oc-NH2, where n = 4, 6, and 8) showed dsDNA binding with a binding constant in the micromolar range (0.3, 3.4, and 0.19 µM, respectively) and were not cytotoxic to HB2 and MDA-MB-231 cells. Selected compounds used in the transfection of a GFP plasmid showed high transfection efficacy and minimal cytotoxicity. Their interaction with plasmid DNA and the increasing length of the main chain of tested compounds strongly influenced the organization and shape of the flower-like nanostructures formed, which were unique for 5/6-FAM-O2Oc-[Dap(GO2)]8-O2Oc-NH2 and typical for large proteins.  相似文献   
8.
Pattern Analysis and Applications - Digital holography is an imaging process able to recreate three-dimensional representations of objects from recording pattern interference among distinct waves....  相似文献   
9.
Half-metallic ferromagnetism in the Ga1 ? xCr x N compound at different concentrations, x = 25, 12.5 and 6.25 %, have been investigated using density functional theory as implemented in code Spanish Initiative for Electronic Simulations with Thousands of Atoms (SIESTA) using LDA + U as exchange-correlation (XC) potential, to find out the possibility of new diluted DMSs. The outcomes reveal that transition metal atom (Cr) doping in GaN induces ferromagnetism. The 3d levels of the TM ion originate a half-metallic gap at the Fermi level in the majority spin channel for all concentrations. Moreover, diluted magnetic semiconductor compounds retain the half-metallic nature at all concentrations, i.e., x = 0.25, 0.125 and 0.0625, with 100 % spin polarization at the Fermi level (E F). The total magnetic moment of these compounds is due to Cr-3d states, and the existence of a small magnetic moment on Ga and N, non-magnetic atoms, for all doping concentrations is a consequence of p-d hybridization of Cr-d and N-p states. The calculated values of s-d exchange constant N α and p-d exchange constant N βconfirm the ferromagnetic character of the Cr-doped GaN compound.  相似文献   
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