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   18104篇
  免费   1190篇
  国内免费   528篇
电工技术   484篇
技术理论   5篇
综合类   1622篇
化学工业   3334篇
金属工艺   919篇
机械仪表   651篇
建筑科学   1620篇
矿业工程   219篇
能源动力   384篇
轻工业   1355篇
水利工程   166篇
石油天然气   576篇
武器工业   141篇
无线电   1038篇
一般工业技术   3195篇
冶金工业   1747篇
原子能技术   168篇
自动化技术   2198篇
  2024年   83篇
  2023年   319篇
  2022年   757篇
  2021年   765篇
  2020年   546篇
  2019年   474篇
  2018年   413篇
  2017年   600篇
  2016年   602篇
  2015年   592篇
  2014年   1124篇
  2013年   1394篇
  2012年   1418篇
  2011年   1147篇
  2010年   948篇
  2009年   1054篇
  2008年   833篇
  2007年   783篇
  2006年   718篇
  2005年   612篇
  2004年   494篇
  2003年   412篇
  2002年   364篇
  2001年   309篇
  2000年   231篇
  1999年   195篇
  1998年   138篇
  1997年   97篇
  1996年   1106篇
  1995年   513篇
  1994年   370篇
  1993年   43篇
  1992年   45篇
  1991年   37篇
  1990年   36篇
  1989年   22篇
  1988年   30篇
  1987年   20篇
  1986年   18篇
  1985年   32篇
  1984年   40篇
  1983年   19篇
  1982年   16篇
  1981年   15篇
  1980年   11篇
  1979年   2篇
  1978年   9篇
  1977年   6篇
  1976年   5篇
  1973年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
This paper presents an innovative neural network-based quality prediction system for a plastic injection molding process. A self-organizing map plus a back-propagation neural network (SOM-BPNN) model is proposed for creating a dynamic quality predictor. Three SOM-based dynamic extraction parameters with six manufacturing process parameters and one level of product quality were dedicated to training and testing the proposed system. In addition, Taguchi’s parameter design method was also applied to enhance the neural network performance. For comparison, an additional back-propagation neural network (BPNN) model was constructed for which six process parameters were used for training and testing. The training and testing data for the two models respectively consisted of 120 and 40 samples. Experimental results showed that such a SOM-BPNN-based model can accurately predict the product quality (weight) and can likely be used for various practical applications.  相似文献   
122.
Intelligent adaptive control for MIMO uncertain nonlinear systems   总被引:3,自引:1,他引:2  
This paper investigates an intelligent adaptive control system for multiple-input–multiple-output (MIMO) uncertain nonlinear systems. This control system is comprised of a recurrent-cerebellar-model-articulation-controller (RCMAC) and an auxiliary compensation controller. RCMAC is utilized to approximate a perfect controller, and the parameters of RCMAC are on-line tuned by the derived adaptive laws based on a Lyapunov function. The auxiliary compensation controller is designed to suppress the influence of residual approximation error between the perfect controller and RCMAC. Finally, two MIMO uncertain nonlinear systems, a mass–spring–damper mechanical system and a Chua’s chaotic circuit, are performed to verify the effectiveness of the proposed control scheme. The simulation results confirm that the proposed intelligent adaptive control system can achieve favorable tracking performance with desired robustness.  相似文献   
123.
该文针对传统的项目申报流程中专家审批环节的缺点,结合枣庄学院当前专家审批的实际情况.基于Lotus Domino/Notes平台设计并开发了专家会签系统,实现了专家审批过程的异地性、自动化和网络化,保证了专家审批的公平性和透明性。  相似文献   
124.
Accurate evaluation of Green’s functions in a layered medium by SDP-FLAM   总被引:1,自引:0,他引:1  
Based on local Taylor expansions on the complex plane, a method for fast locating all modes (FLAM) of spectral-domain Green’s Functions in a planar layered medium is developed in this paper. SDP-FLAM, a combination of FLAM with the steepest descent path algorithm (SDP), is employed to accurately evaluate the spatial-domain Green’s functions in a layered medium. According to the theory of complex analysis, the relationship among the poles, branch points and Riemann sheets is also analyzed rigorously. To inverse the Green’s functions from spectral to spatial domain, SDP-FLAM method and discrete complex image method (DCIM) are applied to the non-near field region and the near filed region, respectively. The significant advantage of SDP-FLAM lies in its capability of calculating Green’s functions in a layered medium of moderate thickness with loss or without loss. Some numerical examples are presented to validate SDP-FLAM method. Supported by the National Natural Science Foundation of China (Grant No. 60621002), and the State Key Development Program for Basic Research of China (Grant No. 2009CB320200)  相似文献   
125.
We present several results on the complexity of various forms of Sperner’s Lemma in the black-box model of computing. We give a deterministic algorithm for Sperner problems over pseudo-manifolds of arbitrary dimension. The query complexity of our algorithm is linear in the separation number of the skeleton graph of the manifold and the size of its boundary. As a corollary we get an deterministic query algorithm for the black-box version of the problem 2D-SPERNER, a well studied member of Papadimitriou’s complexity class PPAD. This upper bound matches the deterministic lower bound of Crescenzi and Silvestri. The tightness of this bound was not known before. In another result we prove for the same problem an lower bound for its probabilistic, and an lower bound for its quantum query complexity, showing that all these measures are polynomially related. Research supported by the European Commission IST Integrated Project Qubit Application (QAP) 015848, the OTKA grants T42559 and T46234, and by the ANR Blanc AlgoQP grant of the French Research Ministry.  相似文献   
126.
It is commonly believed that the longitudinal axes of churches extend exactly in an east-west direction. However, thorough investigations have shown that this is not always correct; rather, both southern and northern deviations of up to about 25° can occur. The angular deviation between the church axis and true east is called the Holy Alignment. This present study presents the possibility that the nave is oriented towards the direction of the sun-rising point on the name day of the patron saint of the church. If several saints share the patronage, the Holy Alignment equals the algebraic sum of the angular distances for each saint. The orientation of a nave can be analyzed by means of common mathematical relations used in geodesy, astronomy and gnomonics. In order to perform such an analysis, it is necessary to know the history of the patronage of the church; the Gauss-Krüger coordinates of the ground plan; and characteristic astronomical quantities at the time the church was built. A calculated example with the saints Andrew, James and Philip for the year 980 illustrates the analysis. An appendix deals with the influence of atmospheric refraction on the apparent altitude of the sun near the horizon.  相似文献   
127.
现在的产品设计与开发,不再以成人世界为主流,市场趋势逐朝向更年青的消费者为主。在儿童成长的过程中,除了家人、亲友陪伴,伴随成长的产品扮演了不可或缺的角色。我国对少年儿童产品设计仍存在些主要问题:设计创新能力不足、造型美感能力薄弱、对使用者的人性角度关怀不够、使用材质与安全性欠缺考虑和考虑角度不够人性化。设计者应在儿童产品设计上,添加更多人性化角度,在产品中应强调细节开发、色彩等,从中建立儿童个人独特个性和发展。  相似文献   
128.
近年来,国产动画产业成长迅速,日益朝着产业规模化的方向发展,然而在动画艺术的创作上却始终找不到准确的定位,无法突破瓶颈。本文试从动画电影的内容与形式两方面进行分析,探索一条适合中国动画发展的道路,提出了结合贴近现代社会生活的题材与符合中国传统审美意识的艺术形式的创作理念。  相似文献   
129.
城市街区空间引导系统与人们的日常生活息息相关,为人们的出行提供了便捷的标识引导,同时它也是城市形象的重要组成部分之一。本文分析总结了该系统的设计原则,并从视觉传达学科入手分析其视觉元素的设计。为了设计无语言障碍和有个性、地域化的城市街区空间引导系统,从符号、文字、色彩三方面对其进行设计思考。  相似文献   
130.
Wilson's disease (WD) is characterized by excessive accumulation of intracellular copper in liver and extrahepatic tissues, leading to significant oxidative stress and tissue damage. To date, several diagnostic biomarkers for WD such as serum ceruloplasmin, serum or urine copper levels and copper content in liver have been identified. However, these biomarkers may not be convincing for the diagnosis in some WD patients. To identify additional novel diagnostic biomarkers, we compared the serum protein profiles of asymptomatic childhood WD patients (n=20), without neurologic manifestation or liver cirrhosis, with normal controls (n=13). Fourteen spots, five up‐regulated and nine down‐regulated (>2‐fold), were differentially expressed in WD patients in comparison to normal control on 2‐DE. Among them, three spots were down‐regulated in both male and female WD. MS/MS analysis revealed that the three spots were complement component C3, complement factor B and alpha‐2 macroglobulin. By comparative proteome analysis, complement component C3, complement factor B and alpha‐2 macroglobulin, which are related to oxidative stress and inflammation, turned out to be good candidates for novel diagnostic biomarkers for early stages of WD.  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