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   16279篇
  免费   2039篇
  国内免费   1635篇
电工技术   1135篇
技术理论   5篇
综合类   1709篇
化学工业   719篇
金属工艺   237篇
机械仪表   827篇
建筑科学   853篇
矿业工程   212篇
能源动力   366篇
轻工业   253篇
水利工程   338篇
石油天然气   207篇
武器工业   166篇
无线电   1631篇
一般工业技术   1693篇
冶金工业   695篇
原子能技术   69篇
自动化技术   8838篇
  2024年   85篇
  2023年   255篇
  2022年   384篇
  2021年   435篇
  2020年   511篇
  2019年   523篇
  2018年   479篇
  2017年   655篇
  2016年   700篇
  2015年   830篇
  2014年   1034篇
  2013年   1304篇
  2012年   1174篇
  2011年   1354篇
  2010年   1024篇
  2009年   1116篇
  2008年   1170篇
  2007年   1177篇
  2006年   989篇
  2005年   817篇
  2004年   683篇
  2003年   561篇
  2002年   486篇
  2001年   389篇
  2000年   327篇
  1999年   227篇
  1998年   197篇
  1997年   165篇
  1996年   142篇
  1995年   120篇
  1994年   95篇
  1993年   76篇
  1992年   77篇
  1991年   55篇
  1990年   48篇
  1989年   44篇
  1988年   30篇
  1987年   17篇
  1986年   20篇
  1985年   16篇
  1984年   13篇
  1983年   14篇
  1982年   21篇
  1981年   14篇
  1980年   14篇
  1979年   8篇
  1978年   10篇
  1976年   6篇
  1975年   7篇
  1957年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
感应电机压频比调节的模糊节能控制   总被引:1,自引:0,他引:1  
王爱元  凌志浩 《电气自动化》2008,30(6):23-24,44
根据三相感应电机的等效电路,推导出电机的损耗和输出功率与压频比之间的关系,提出了压频比调节的节能控制方法。考虑电机不同负载时损耗曲线的变化持点,引入基于电机转速和输入功率的比例算子,对电机输入功率的变化进行量化;电机稳态运行时进行模糊自寻优控制,动态调速时进行较高的恒压频比控制,提高了电机的效率并保持了一定的动态响应特性。仿真结果验证了运行控制方案的可行性和有效性。  相似文献   
92.
空气钻井条件下录井工艺方法与技术配套探讨   总被引:4,自引:0,他引:4  
针对玉门青西油田深部高陡易斜地层存在可钻性差、自然造斜能力强,致使钻井周期长、成本高等特点,中油集团公司在吐哈油田设立钻探“工程探索井(L14井)”重大科研项目,试验研究空气钻井技术。根据L14井录井的实际情况,首先分析了空气钻井条件对录井带来的影响和常规的录井工艺方法和技术设备存在的不足;从5个方面介绍了录井工艺、技术方法的改进,探讨了空气钻井下的岩屑上返理论;介绍了配置装备的改进,分析了该井录井配套技术的应用效果。从该试验井的录井效果看,经改进的录井工艺、方法及装备基本上能满足空气钻井的需要,取全取准了地质及工程资料,为地质解释和评价提供了可靠依据;在工程监测、保障施工安全方面,工程录井也发挥了作用。但综合录井仪软件及后台评价程序还不适应空气钻井的需要,相关的理论研究及工艺完善还有许多课题尚需深入。  相似文献   
93.
手写体汉字识别问题综论   总被引:6,自引:0,他引:6  
本文在讨论了人对汉字的认知心理试验研究结果之后,认为人类的汉字识别是经由整字属性及分层结构的多种途径复合而成的。这些途径中的大多数都可以在手写体汉字的机器识别中模仿运用。由此可把汉字的机器识别方法归纳为整模式法和子模式法两个大类,对它们的有利方面和困难方面进行了讨论;对影响其性能的因素进行了分析;对识别率以及它与识别字集大小和后处理等的关系提出了评估的问题。  相似文献   
94.
文章首先概述了当前大多数的搜索引擎的主要的弊端;然后着重介绍了智能检索系统的运行基本思路和售用算法,以及该算法在检索领域中运用的优点;最后指出,神经网络运用在检索领域,可解决网络管理中的诸多难题。  相似文献   
95.
96.
The paper considers the set-theoretical approach to the joint decomposition of systems of Boolean functions of variables specified in different representation forms. The approach is based on the method of q-partitions of conjuncterms and concept of decomposition clones. Theorems on joint decomposition of a system of full and partial functions are formulated. The approach is illustrated by examples. Parts I and II of this article are published in No. 5 (2001) and No. 1 (2002). __________ Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 39–58, March–April 2007.  相似文献   
97.
In this article we study thetabu search (TS) method in an application for solving an important class of scheduling problems. Tabu search is characterized by integrating artificial intelligence and optimization principles, with particular emphasis on exploiting flexible memory structures, to yield a highly effective solution procedure. We first discuss the problem of minimizing the sum of the setup costs and linear delay penalties when N jobs, arriving at time zero, are to be scheduled for sequential processing on a continuously available machine. A prototype TS method is developed for this problem using the common approach of exchanging the position of two jobs to transform one schedule into another. A more powerful method is then developed that employs insert moves in combination with swap moves to search the solution space. This method and the best parameters found for it during the preliminary experimentation with the prototype procedure are used to obtain solutions to a more complex problem that considers setup times in addition to setup costs. In this case, our procedure succeeded in finding optimal solutions to all problems for which these solutions are known and a better solution to a larger problem for which optimizing procedures exceeded a specified time limit (branch and bound) or reached a memory overflow (branch and bound/dynamic programming) before normal termination. These experiments confirm not only the effectiveness but also the robustness of the TS method, in terms of the solution quality obtained with a common set of parameter choices for two related but different problems.  相似文献   
98.
Markovian and semi-Markovian random processes are used to analyze the problem of optimal search for signals in a multichannel communication system with arbitrarily distributed random outputs. The search efficiency factor is found in explicit form based on state space merging, and a mathematical programming problem is set up to find a numerical suboptimal solution. __________ Translated from Kibernetika i Sistemnyi Analiz, No. 3, pp. 144–150, May–June 2007.  相似文献   
99.
In recent years, both functionalist and dynamic systems approaches have assumed increasing prominence in the study of emotion and its development, but the similarities and differences between these perspectives remain largely unexplored and open to more systematic examination. In this article, the authors argue that both approaches share a systems view of emotion and regard emotion in relational, process terms. However, each approach adopts a distinct level of analysis and distinct types of explanation for emotion and its development. Whereas the functionalist approach appeals to formal and final causes to explain patterning in emotion at the level of organism-environment relations, the dynamic systems approach appeals to efficient and material causes to explain emotion at the specific content level of behavior in context. Whether these approaches complement or conflict with one another depends on the extent to which the dynamic systems approach admits abstraction into its explanatory framework. A. Fogel's social process theory and M. D. Lewis' approach to emotion self-organization are discussed in this regard. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
100.
In this paper we present an efficient technique for piecewise cubic Bézier approximation of digitized curve. An adaptive breakpoint detection method divides a digital curve into a number of segments and each segment is approximated by a cubic Bézier curve so that the approximation error is minimized. Initial approximated Bézier control points for each of the segments are obtained by interpolation technique i.e. by the reverse recursion of De Castaljau's algorithm. Two methods, two-dimensional logarithmic search algorithm (TDLSA) and an evolutionary search algorithm (ESA), are introduced to find the best-fit Bézier control points from the approximate interpolated control points. ESA based refinement is proved to be better experimentally. Experimental results show that Bézier approximation of a digitized curve is much more accurate and uses less number of points compared to other approximation techniques.  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