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   10759篇
  免费   930篇
  国内免费   438篇
电工技术   747篇
综合类   999篇
化学工业   1381篇
金属工艺   243篇
机械仪表   458篇
建筑科学   1054篇
矿业工程   473篇
能源动力   646篇
轻工业   1558篇
水利工程   358篇
石油天然气   584篇
武器工业   242篇
无线电   751篇
一般工业技术   892篇
冶金工业   478篇
原子能技术   121篇
自动化技术   1142篇
  2024年   58篇
  2023年   152篇
  2022年   260篇
  2021年   327篇
  2020年   386篇
  2019年   319篇
  2018年   284篇
  2017年   359篇
  2016年   431篇
  2015年   429篇
  2014年   663篇
  2013年   765篇
  2012年   783篇
  2011年   886篇
  2010年   613篇
  2009年   576篇
  2008年   569篇
  2007年   651篇
  2006年   556篇
  2005年   519篇
  2004年   395篇
  2003年   360篇
  2002年   315篇
  2001年   229篇
  2000年   213篇
  1999年   166篇
  1998年   148篇
  1997年   106篇
  1996年   100篇
  1995年   72篇
  1994年   81篇
  1993年   52篇
  1992年   42篇
  1991年   31篇
  1990年   40篇
  1989年   24篇
  1988年   27篇
  1987年   18篇
  1986年   16篇
  1985年   15篇
  1984年   10篇
  1983年   7篇
  1982年   7篇
  1981年   6篇
  1980年   6篇
  1979年   4篇
  1964年   9篇
  1962年   8篇
  1958年   4篇
  1957年   6篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Artificial bee colony (ABC) algorithm has several characteristics that make it more attractive than other bio-inspired methods. Particularly, it is simple, it uses fewer control parameters and its convergence is independent of the initial conditions. In this paper, a novel artificial bee colony based maximum power point tracking algorithm (MPPT) is proposed. The developed algorithm, does not allow only overcoming the common drawback of the conventional MPPT methods, but it gives a simple and a robust MPPT scheme. A co-simulation methodology, combining Matlab/Simulink™ and Cadence/Pspice™, is used to verify the effectiveness of the proposed method and compare its performance, under dynamic weather conditions, with that of the Particle Swarm Optimization (PSO) based MPPT algorithm. Moreover, a laboratory setup has been realized and used to experimentally validate the proposed ABC-based MPPT algorithm. Simulation and experimental results have shown the satisfactory performance of the proposed approach.  相似文献   
2.
Thermal bending analysis of doubly curved laminated shell panels with general boundary conditions and laminations is presented. The equations of equilibrium are derived in the form of two coupled sets of ordinary differential equations based on a general shell theory and solved through the state-space approach in a repeated manner. It is depicted that the results of the present method are in great agreement with analytical solutions. Cylindrical shell panels with general boundary conditions and laminations, where no analytical solution is available, are solved. It is found that the present method exhibits a high convergence rate as well as presenting accurate results in all cases.  相似文献   
3.
Aggressive behavior induces an adrenocortical stress response, and sudden stressors often precipitate violent behavior. Experiments in rats revealed a fast, mutual, positive feedback between the adrenocortical stress response and a brain mechanism controlling aggression. Stimulation of the aggressive area in the hypothalamus rapidly activated the adrenocortical response, even in the absence of an opponent and fighting. Hypothalamic aggression, in turn, was rapidly facilitated by a corticosterone injection in rats in which the natural adrenocortical stress response was prevented by adrenalectomy. The rapidity of both effects points to a fast, mutual, positive feedback of the controlling mechanisms within the time frame of a single conflict. Such a mutual facilitation may contribute to the precipitation and escalation of violent behavior under stressful conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
4.
0.89dtex细旦涤纶短纤维工艺优化探讨   总被引:2,自引:1,他引:1  
介绍了纺制 0 89dtex× 3 8mm细旦涤纶短纤维的工艺技术特点 ,着重讨论了熔体温度、纺丝速度、冷却条件等工艺对原丝性能及产品质量的影响  相似文献   
5.
对韶钢炼铁厂4号高炉炉况和操作上存在的问题进行了分析,主要原因是原材料质量较差,精料水平低,同时,高炉操作不能完全适应原材料条件.按照上稳下活工艺的原则,采取合理鼓风动能、活跃炉缸工作状态、稳定热制度、合理中部冷却强度、炉顶小高压操作以及使用上部调节手段等一系列措施,使高炉的炉况顺行得到了较大的改善,各项主要技术经济指标取得相应的进步.2001年利用系数达3.024 t/m3·d,焦比达441 kg/t.  相似文献   
6.
设计了一种适合在低电源电压下工作的前馈型输入级放大结构,在全摆幅的动态工作范围内,输入级跨导保持不变,采用负载电流补偿以保证增益近似恒定,输出采用前馈型AB类输结构,实现全摆幅输出。  相似文献   
7.
In this paper we present some preliminary results about the coupling of shallow water equations for free surface flows and Darcy equation for groundwater flows. A suitable set of interface conditions is discussed: the Beavers and Joseph formula for the bottom stress is used. An iterative algorithm to solve the coupled problem is proposed and some numerical results are presented.  相似文献   
8.
A modified variational-gradient method is proposed and substantiated for quasilinear operator equations in a Hilbert space.  相似文献   
9.
When dealing with a Soviet client, tendering, scheduling, consideration of available resources, management responsibilities, start-up and hand-over must be approached from a slightly different angle than when dealing with Western clients. Aspects of project management from feasibility analysis to hand-over are described, based on the experience of a Finnish general contractor, Finn Stroi.  相似文献   
10.
During the day, there are considerable variations in the climatic factors prevailing in these regions. This is especially so during the 24-hour daily cycle of the long, hot and dry summer (mid-May to midOctober). Such climatic conditions have had a considerable impact on the daily living pattern of family life in the same season, particularly in the urban areas. During the same 24-hour cycle, they have compelled the inhabitants to shift their living activities both vertically in section and horizontally in plan; they do this in pursuit of more acceptable, if not, desirable internal thermal environmental ambience.  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