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   31494篇
  免费   1954篇
  国内免费   710篇
电工技术   1299篇
技术理论   1篇
综合类   3702篇
化学工业   972篇
金属工艺   326篇
机械仪表   620篇
建筑科学   18753篇
矿业工程   571篇
能源动力   760篇
轻工业   202篇
水利工程   392篇
石油天然气   303篇
武器工业   123篇
无线电   1098篇
一般工业技术   2285篇
冶金工业   353篇
原子能技术   197篇
自动化技术   2201篇
  2024年   52篇
  2023年   156篇
  2022年   463篇
  2021年   483篇
  2020年   604篇
  2019年   484篇
  2018年   413篇
  2017年   643篇
  2016年   727篇
  2015年   908篇
  2014年   3440篇
  2013年   1951篇
  2012年   2370篇
  2011年   2386篇
  2010年   2093篇
  2009年   2219篇
  2008年   1978篇
  2007年   2320篇
  2006年   1717篇
  2005年   1553篇
  2004年   1264篇
  2003年   1054篇
  2002年   892篇
  2001年   802篇
  2000年   651篇
  1999年   587篇
  1998年   406篇
  1997年   324篇
  1996年   279篇
  1995年   204篇
  1994年   154篇
  1993年   140篇
  1992年   101篇
  1991年   77篇
  1990年   64篇
  1989年   42篇
  1988年   33篇
  1987年   26篇
  1986年   12篇
  1985年   18篇
  1984年   8篇
  1983年   9篇
  1982年   8篇
  1981年   6篇
  1980年   21篇
  1979年   3篇
  1978年   3篇
  1977年   2篇
  1976年   3篇
  1975年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
In this paper, the material constant sensitivity boundary integral equation is presented, and its numerical solution proposed, based on boundary element techniques. The formulation deals with plane problems with general rectilinear anisotropy. Expressions for the computation of sensitivities for displacements, tractions, strains and stresses are derived, both for boundary and interior points. The sensitivities can be computed with respect to the bulk material properties or to the properties of part of the domain (inclusions, coatings, etc.). To assess the accuracy of the proposed approach, the computed results are compared to analytical ones derived from exact solutions obtained by complex potential theory, when possible, or finite difference derivatives otherwise. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
102.
建筑围护结构与节能   总被引:4,自引:0,他引:4  
针对我国夏热冬冷地区的建筑气候特点,对建筑围护结构节能在设计中的要点和意义进行了讨论。  相似文献   
103.
建筑结构爆破震动效应及安全分析研究   总被引:19,自引:8,他引:11  
霍永基 《爆破》2003,20(1):1-6
从现代爆破作用原理出发。对岩体爆破的振动特性,影响因素及最新研究进展作了综合评述。并通过大量科研观测资料分析。结合我国某些工程实践经验。着重介绍了岩土爆破对闸坝工程,水工隧洞的作用特性。破坏机制和安全准则。  相似文献   
104.
使用自粘性防水卷材对带钢副框的铝合金门窗窗边进行粘接,以防止雨水通过副框与墙体之间的缝隙渗漏到室内,重点介绍了详细的施工措施。  相似文献   
105.
A time‐dependent coefficient of heat transfer is proposed for the computation of thermal power required, so that a room temperature reaches a desired value within a given time. A mathematical formulation of the room heating transient phenomenon is constructed in a dimensionless form. Using an integral approximate solution an analytical expression for this coefficient is provided and it is verified by diagrams adopted by DIN 4701. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
106.
论智能化建筑   总被引:4,自引:4,他引:0  
李青 《山西建筑》2007,33(32):57-58
详细地阐述了智能化建筑的概念及其产生和发展、智能住宅的产生和发展,针对我国智能建筑发展存在的问题提出了建议,同时对未来的智能化建筑进行了展望,从而促进我国智能化建筑的发展。  相似文献   
107.
This paper investigates the feasibility of using genetic programming (GP) to create an empirical model for the complicated non-linear relationship between various input parameters associated with reinforced concrete (RC) deep beams and their ultimate shear strength. GP is a relatively new form of artificial intelligence, and is based on the ideas of Darwinian theory of evolution and genetics. The size and structural complexity of the empirical model are not specified in advance, but these characteristics evolve as part of the prediction. The engineering knowledge on RC deep beams is also included in the search process through the use of appropriate mathematical functions.The model produced by GP is constructed directly from a set of experimental results available in the literature. The validity of the obtained model is examined by comparing its response with the shear strength of the training and other additional datasets. The developed model is then used to study the relationships between the shear strength and different influencing parameters. The predictions obtained from GP agree well with experimental observations.  相似文献   
108.
Thermal insulation is one of the most effective energy-conservation measures in buildings. Despite the widespread use of insulation materials in recent years, little is known regarding their optimum thickness under dynamic thermal conditions. Insulated concrete blocks are among the units most commonly used in the construction of building walls in Saudi Arabia. Typically, the insulation layer thickness is fixed at a value in the range 2.5–7.5 cm, regardless of the climatic conditions, type and cost of insulation material, and other economic parameters. In the present study, a numerical model based on a finite-volume, time-dependent implicit procedure, which has been previously validated, is used to compute the yearly cooling and heating transmission loads under steady periodic conditions through a typical building wall, for different insulation thicknesses. The transmission loads, calculated by using the climatic conditions of Riyadh for a west-facing wall, are fed into an economic model in order to determine the optimum thickness of insulation (Lopt). The latter corresponds to the minimum total cost, which includes the cost of insulation material and its installation plus the present value of energy consumption cost over the lifetime of the building. The optimum insulation thickness depends on the electricity tariff as well as the cost of insulation material, lifetime of the building, inflation and discount rates, and coefficient of performance of the air-conditioning equipment. In the present study, the effect of electricity tariff on the computed optimum insulation thickness is investigated. Different average electricity tariffs are considered; namely, 0.05, 0.1, 0.2, 0.3 and 0.4 SR/kWh (designated as Cases 1–5, respectively; 1 US$ = 3.75 Saudi Riyals). Results using moulded polystyrene as an insulating material show that the values of Lopt are: 4.8, 7.2, 10.9, 13.7 and 16.0 cm for Cases 1–5. Under the conditions of optimal insulation thickness for each electricity tariff, Case 1 gives the lowest total cost of 17.4 SR/m2, while Case 5 gives the highest total cost of 53.1 SR/m2. Corresponding thermal performance characteristics in terms of yearly total and peak transmission loads, R-value, time lag and decrement factor are presented.  相似文献   
109.
胡洁 《安徽建筑》2007,14(3):15-16
文章从居住社区的规划设计和建筑设计两方面以低能耗的角度分析了城市居住功能的分布、社区住宅建筑布局的合理性、社区景观设置的合理性以及停车、中水处理与被动式太阳能住宅建筑的相关先进生态理念,希望通过居住社区的生态可持续性设计改善社区的舒适性和能源的可持续性.  相似文献   
110.
对高层建筑设计而言,设计前期的初步结构方案需通过结构软件的计算分析,判断该方案是否正确与合理,从而对其进行有针对性的修改和优化。文章结合具体实例,介绍了分析判断计算结果的主要几项内容及可采取的相应优化措施,从而可以提高设计的准确性和工作效率。  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