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   46822篇
  免费   4659篇
  国内免费   3331篇
电工技术   3006篇
技术理论   8篇
综合类   5956篇
化学工业   5431篇
金属工艺   1658篇
机械仪表   2646篇
建筑科学   3725篇
矿业工程   1417篇
能源动力   1595篇
轻工业   1458篇
水利工程   1093篇
石油天然气   1411篇
武器工业   670篇
无线电   5023篇
一般工业技术   5138篇
冶金工业   2715篇
原子能技术   568篇
自动化技术   11294篇
  2024年   183篇
  2023年   740篇
  2022年   992篇
  2021年   1244篇
  2020年   1400篇
  2019年   1258篇
  2018年   1300篇
  2017年   1542篇
  2016年   1753篇
  2015年   1753篇
  2014年   2626篇
  2013年   3234篇
  2012年   3012篇
  2011年   3519篇
  2010年   2832篇
  2009年   3001篇
  2008年   2938篇
  2007年   3146篇
  2006年   2944篇
  2005年   2426篇
  2004年   1982篇
  2003年   1732篇
  2002年   1452篇
  2001年   1164篇
  2000年   1005篇
  1999年   871篇
  1998年   646篇
  1997年   595篇
  1996年   482篇
  1995年   448篇
  1994年   363篇
  1993年   324篇
  1992年   284篇
  1991年   229篇
  1990年   169篇
  1989年   190篇
  1988年   147篇
  1987年   81篇
  1986年   109篇
  1985年   82篇
  1984年   75篇
  1983年   54篇
  1982年   58篇
  1981年   49篇
  1980年   38篇
  1979年   32篇
  1978年   30篇
  1977年   26篇
  1964年   26篇
  1955年   35篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
The deposition morphology of Brownian/non-Brownian particles within a constricted tube is investigated by applying the Brownian dynamics simulation method in the present paper. Two different geometric structures, the parabolic constricted tube (PCT) and the sinusoidal constricted tube (SCT), are adopted. The effect of various types of the total interaction energy curves of the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, and of the shadow area cast by those deposited particles, on the particles’ collection efficiencies are also examined. For the PCT structure, under the same interaction energy curve, it is found that the non-Brownian particles always own a higher collection efficiency than that of the Brownian particles. Since the deposition location moves closer to the constriction part of the tube, the collection efficiencies of the Brownian/non-Brownian particles increase with the decrease of flow velocity. The SCT behaves differently, it is found that the collection efficiencies of non-Brownian particles are only slightly higher than those of Brownian particles when SCT is adopted. The steep slope of the tube wall near the constriction part of SCT dominates the whole deposition process of Brownian/non-Brownian particles. In comparison with the available experimental data, it is found that the present method can give a good simulation result.  相似文献   
112.
The appraisal process consists of the subjective evaluation that occurs during an individual's encounter with significant events in the environment, determining the nature of the emotional reaction and experience. Placed in the context of appraisal theories of emotion-elicitation and differentiation, the aim of the present research was to test empirically the hypothesis that the intrinsic pleasantness evaluation occurs before the goal conduciveness evaluation. In two studies, intrinsically pleasant and unpleasant images were used to manipulate pleasantness, and a specific event in a Pacman-type videogame was used to manipulate goal conduciveness. Facial EMG was used to measure facial reactions to each evaluation. As predicted, facial reactions to the intrinsic pleasantness manipulation were faster than facial reactions to the goal conduciveness manipulation. These results provide good empirical support for the sequential nature of the appraisal process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
113.
The theory of planned behavior suggests attitudes are a product of salient beliefs. This study examined whether aggregating salient beliefs was plausible within a more biologically centered information-processing environment. A neural network was used to examine associations among beliefs relating to exercise intention. Data on intentions and behavioral, normative, and control beliefs from 114 respondents were used to train (by error backpropagation) a neural network to associate beliefs with intention. The R2 between the network's estimated and self-reported intention was .66. The network's representation comprised 6 belief profiles associated with high, moderate, or low behavioral intention. The neural network accommodated complex relationships among beliefs and belief-intention associations and indicated how high-level constructs such as attitudes may be viewed as the best fit (compromise state) between aroused beliefs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
114.
对职业教育的大众性问题进行了论述、实证分析和理论、政策、改革等思考。  相似文献   
115.
In arc welding processes, because of the complexity and nonlinearity of heat transfer phenomena, it is often difficult to design an effective control system based upon an exact mathematical model. In this paper, a self-organizing fuzzy control method is proposed to obtain a uniform weld quality by regulation of the surface temperature at a desired level. The proposed control system is designed to comprise a combined structure of the fuzzy SOC with conventional PD control for improving the system's stability. The control experiments show that the proposed controller guarantees a uniform weld quality for various welding conditions.  相似文献   
116.
An improved set of parameters for vanadium in the semiempirical quantum chemical SCF MO method SINDO1 is presented. It is shown that both the geometries and heats of formation of a number of vanadium-containing compounds calculated by this method are in good agreement with available experimental data. Model clusters of increasing size are used for the study of geometric and energetic properties of vanadium pentoxide. Both hydrogen atom and proton adsorption on the (010) surface of vanadium pentoxide and a subsequent formation of different oxygen vacancies have been investigated. Based on these computational results the reactivities of V2O5-surface oxygen atoms for adsorption are discussed.  相似文献   
117.
Summary Recent progress in the modelling of exchanged Cu sites and their interactions with small molecules, based on DFT cluster calculations, is briefly reviewed.  相似文献   
118.
We consider an extension of the functional programming language Standard ML with a modular structure based upon concepts in category theory such as categories, functors, natural transformations and adjunctions. In essence, we are following the categorical imperative of considering arrows as well as objects. This is intended to enforce a certain mathematical rigour on the programmer, so that the only programs that can be expressed are those with a categorical significance. The essentially algebraic nature of category theory means that we may generate equational correctness conditions for the modular structure of programs, thus separating the correctness of individual functions from that of modules. We describe this programming language, give examples of its use, and explain how it is implemented in a type system.  相似文献   
119.
压力传感器的应力计算   总被引:2,自引:0,他引:2  
从弹性力学的板壳理论出发,对不同参数的凸型板结构形变膜受压后的应力分布作了近似计算,为高线性度SOI压力传感器的芯片设计提供了理论指导。用BESOI技术研制的凸型板结构集成压力传感器的非线性度达0 09%,样品灵敏度的实测值与应力计算理论值的差别约17%。  相似文献   
120.
被Kerr介质包围的J—C模型中光场位相特性   总被引:2,自引:0,他引:2  
李高翔  彭金生 《光电子.激光》1992,3(4):201-205,212
本文应用Pegg-Barnett位相理论讨论了被Kerr介质包围的J-C模型中光场的位相性质。  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