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   48908篇
  免费   4111篇
  国内免费   4143篇
电工技术   3971篇
技术理论   5篇
综合类   3527篇
化学工业   3222篇
金属工艺   554篇
机械仪表   2491篇
建筑科学   2015篇
矿业工程   359篇
能源动力   1601篇
轻工业   574篇
水利工程   436篇
石油天然气   395篇
武器工业   284篇
无线电   4022篇
一般工业技术   4315篇
冶金工业   1224篇
原子能技术   264篇
自动化技术   27903篇
  2024年   196篇
  2023年   750篇
  2022年   669篇
  2021年   980篇
  2020年   1319篇
  2019年   1428篇
  2018年   1315篇
  2017年   1749篇
  2016年   1912篇
  2015年   1743篇
  2014年   2875篇
  2013年   4217篇
  2012年   2471篇
  2011年   3192篇
  2010年   2272篇
  2009年   2797篇
  2008年   2876篇
  2007年   2887篇
  2006年   2538篇
  2005年   2274篇
  2004年   1958篇
  2003年   1775篇
  2002年   1583篇
  2001年   1288篇
  2000年   1239篇
  1999年   1125篇
  1998年   1020篇
  1997年   850篇
  1996年   776篇
  1995年   691篇
  1994年   599篇
  1993年   568篇
  1992年   447篇
  1991年   434篇
  1990年   330篇
  1989年   265篇
  1988年   223篇
  1987年   181篇
  1986年   152篇
  1985年   188篇
  1984年   196篇
  1983年   175篇
  1982年   152篇
  1981年   102篇
  1980年   74篇
  1979年   89篇
  1978年   62篇
  1977年   67篇
  1976年   20篇
  1975年   13篇
排序方式: 共有10000条查询结果,搜索用时 28 毫秒
71.
A wavelet based identification method for linear time-varying systems is presented,and the ridge and skeleton of the continuous wavelet transform of free response is used to extract time-varying parameters. The stiffness and damping coefficients of single-degree-of—freedom systems,frequencies and damping ratios of multi-degree-of-freedom systems are estimated without any prior information of systems. The proposed method is applied to linear time-varying systems with both abrupt and smooth variation parameters. Gaussian white noise is added to the response to test the anti-noise performance of the algorithm. The simulation results show that the proposed method is capable of accurately tracking the variation of the systems.  相似文献   
72.
73.
This paper discusses the problem of anticipation from an evolutionary and systems-theoretical perspective, developed in the context of Russian/Soviet evolutionary biological and neurophysiological schools in the early and mid-twentieth century. On this background, an outline is given of the epigenetic interpretation of anticipatory capacities formulated and substantiated by the eminent Russian neurophysiologist academician Peter K. Anokhin in the framework of functional systems theory. It is considered that several key positions of this theory are well confirmed by recent evidence on anticipation as an evolutionarily basic adaptive capacity, possibly inherent to the organization of life. In the field of neuroscience, the theory of functional systems may potentially facilitate future studies at the intersection of learning, development and evolution by representing an integrative approach to the problem of anticipation.  相似文献   
74.
75.
环境问题与经济问题紧密相连,由于环境问题的综合性和复杂性,需要运用系统工程的方法和经济学原理,将环境问题置于整个经济系统中统筹考虑,建立相对完整的环境经济系统工程方法体系,将环境保护工作纳入经济社会发展中,使其成为决策中主要考虑的因素之一,并引起应有的重视。本研究从环境与经济承载力、环境投资的经济分析、环境与投资效率比较、环境资源的经济价值以及生态补偿与污染赔偿等方面构建环境经济系统工程的基本框架体系,并结合实际进行案例分析。研究表明,单纯的政府行政干预不如创造条件,如补偿、税收减免、投资、贴息等,使其具备在市场规则下.自动引导资源向环境保护与污染治理的投入,如排污指标的交易等。此外,自然资源是不可或缺的稀有资本,应该将保护生态系统及生物多样性纳入各级政府决策的主要方面。  相似文献   
76.
This paper studies the leader-following consensus problem for a class of second-order nonlinear multi-agent systems subject to linearly parameterized uncertainty and disturbance. The problem is solved by integrating the adaptive control technique and the adaptive distributed observer method. The design procedure is illustrated by an example with a group of Van der Pol oscillators as the followers and a harmonic system as the leader.  相似文献   
77.
武器装备的电磁环境适应性已成为制约武器装备能打仗、打胜仗的一个重大问题;西方军事强国非常重视面向复杂电磁环境的武器装备试验与评价技术研究和能力建设,通过相关投资计划的长期持续投入,支持突破其中的关键技术、方法,以及构建相应的试验与评价设施能力;文章从标准规范和研制程序、技术方法、试验设施、科研和能力建设投资计划等几方面综述了国外武器装备复杂电磁环境适应性试验与评价技术和能力发展情况,并在此基础上,提出了对我国武器装备电磁环境适应性试验与评价能力的发展建议.  相似文献   
78.
Abstract

This article reports findings of a study of how leaders of virtual information systems development teams improve team trust and cooperation by managing adaptation of information and communications tools. Results indicate how Theory X (command and control) and Theory Y (facilitate and support) styles of leadership enable and hinder effective outcomes.  相似文献   
79.
This paper addresses the design of low‐level controllers for leader–follower formations of nonholonomic vehicles in the presence of bounded measurement delays. The concept of input‐to‐state stability is extended to encompass the effect of bounded delays and restrictions on the input. A method is proposed to integrate a Smith predictor in a backstepping design on the basis of nested saturations and nonlinear small‐gain assignment, which allows for time delays in the feedback loop. Robustness analysis under uncertain bounded time delays is provided, and design tradeoffs resulting from the use of bounded controls are discussed. Illustrative simulations are shown to validate the design and robustness analysis in the context of a simple leader–follower trailing control problem. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
80.
Yelp, a social media site, undeniably has an influence on consumers' food choice in spite of its ability to reflect consumers' real voice being criticized. Since unhealthy food choices contribute to health problems, such as obesity and malnourishment, we attempted to examine these problems by better understanding consumers through health-related cues to action—a construct from the Health Belief Model (HBM)— on Yelp Honolulu's restaurant reviews. Our research revealed 13 main categories: Ingredient, Type of food, Taste, Lifestyle, Cooking, Option, Price, Portion, Well-being, Nutrition, Hygiene, Emotional attachment and indulgence, and Feeling. We argue that these categories may ultimately lead consumers to make healthier food choices. In search of the most appealing way to communicate with the target group, underlying concepts that derived from these categories can be tested. Marketers in food industry (or public health policy-makers) can craft their strategies for healthy food brands/products (or healthy eating scheme) based on the concept test research. Moreover, Yelp can apply these insights in the development of their algorithm and filter system in order to help consumers find healthy food if they wish to do so. Restaurants can also improve their strategy, menu, and communication execution to meet the growing demands of health conscious consumers.  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