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   16595篇
  免费   1762篇
  国内免费   1127篇
电工技术   1363篇
综合类   1607篇
化学工业   1801篇
金属工艺   1702篇
机械仪表   1484篇
建筑科学   1154篇
矿业工程   1293篇
能源动力   682篇
轻工业   1106篇
水利工程   605篇
石油天然气   734篇
武器工业   200篇
无线电   1217篇
一般工业技术   2016篇
冶金工业   574篇
原子能技术   190篇
自动化技术   1756篇
  2024年   84篇
  2023年   260篇
  2022年   493篇
  2021年   526篇
  2020年   603篇
  2019年   505篇
  2018年   513篇
  2017年   635篇
  2016年   721篇
  2015年   734篇
  2014年   1081篇
  2013年   1137篇
  2012年   1235篇
  2011年   1311篇
  2010年   1024篇
  2009年   992篇
  2008年   816篇
  2007年   1119篇
  2006年   954篇
  2005年   783篇
  2004年   662篇
  2003年   536篇
  2002年   457篇
  2001年   381篇
  2000年   350篇
  1999年   305篇
  1998年   192篇
  1997年   215篇
  1996年   169篇
  1995年   129篇
  1994年   127篇
  1993年   75篇
  1992年   70篇
  1991年   52篇
  1990年   52篇
  1989年   38篇
  1988年   32篇
  1987年   13篇
  1986年   21篇
  1985年   13篇
  1984年   14篇
  1983年   16篇
  1982年   14篇
  1981年   3篇
  1980年   7篇
  1979年   2篇
  1978年   3篇
  1977年   3篇
  1975年   2篇
  1960年   1篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
11.
首先用问卷调查的方式得到人们对合体裤提臀的要求,主要表现在臀突感、臀下以及臀后与人体的贴合度上;其后对6款样裤进行了拓版,得到影响提臀效果的结构设计参数.在此基础上用实验法得出结果:在合体裤制版参数常用取值范围内,总裆宽越小,后上裆倾斜角越大,前后裆宽比越小,裤子的提臀效果越好;通过美观性与舒适性的评价,得出兼顾两者的参数配置.  相似文献   
12.
Corrosion products on two typical materials, SA213-T12 steel and alloy 625 exposed to the actual combustion gas, were analyzed in addition to laboratory tests for penetration of corrosive matter. It has been clarified that corrosion products of oxides containing a little chlorides and sulphides show lamellar structures and that at the alloy-scale interface, chlorination, sulphidation, and oxidation occur under a low PO2-high PCl2 condition. The formation of scale structures and the effect of corrosion-resistant alloying elements can be explained according to the stability tendencies of metals, chlorides, and oxides in the M-Cl-O equilibrium diagrams. The severity of corrosion environments at the interface is influenced by the penetration extent of corrosive matters through deposits and scales, and the protective effects of oxide films derived from alloying elements play an important role in preventing the corrosion. On the other hand, it has been shown that thermal fluctuation characterized in this kind of environment makes the lamellar scale structures and sometimes breaks and peels off the scale, and thus accelerates the corrosion. On the basis of the above mentioned knowledge, a new corrosion model is presented.  相似文献   
13.
Precision investment casting process planning has been tackled in the past according to experience. Recently, casting simulation software is being increasingly used to predict product quality by implementing ‘what-if’ scenarios. Input parameters include relatively simple factors such as mould temperature, melting temperature, casting material. They also include factors whose influence is more complex to quantify, such number and location of feeding points, diameter and length of inflow channels, angle of channel with respect to the main sprue axis. Simulation results cannot help the engineer for workpieces other than the one simulated. In this paper a series of feedforward artificial neural network (ANN) models is presented aiming at such generalisation. To achieve this, a large number of software simulation runs were conducted for a number of different small parts, with varying runner geometry and casting conditions. The parameters characterising part geometry have been chosen to be surface area and volume-to-area ratio. The different ANN models predictive capabilities are reflected to the respective training and generalisation errors. A user-friendly interface has been conducted for model execution in a complete application, whose main virtue is expandability.  相似文献   
14.
南京河西地区软土场地地震动参数研究   总被引:3,自引:0,他引:3  
根据南京河西地区所处的地震地质环境、地震活动环境及基岩地震动衰减规律 ,对所选取的某个典型工程软土场地 ,进行了地震危险性分析 ,给出了基岩地震动参数 ;对场地的地震动效应进行了研究 ,给出了 5 0a及10 0a超越概率水平为 6 3%、10 %和 3%的场地地震动参数。该成果对河西地区的工程抗震设计有一定的参考价值  相似文献   
15.
16.
A new method of generating pulsar time based on a coherent representation of a sequence of observed events is considered. The properties of pulsar time compared with the traditional approach are analyzed. __________ Translated from Izmeritel’naya Tekhnika, No. 6, pp. 39–44, June, 2006.  相似文献   
17.
We review, unify and extend work pertaining to evaluating mode mixity of interfacial fracture utilizing the virtual crack closure technique (VCCT). From the VCCT, components of the strain energy release rate (SERR) are obtained using the forces and displacements near the crack tip corresponding to the opening and sliding contributions. Unfortunately, these components depend on the crack extension size, Δ, used in the VCCT. It follows that a mode mixity based upon these components also will depend on the crack extension size. However, the components of the strain energy release rate can be used for determining the complex stress intensity factors (SIFs) and the associated mode mixity. In this study, we show that several—seemingly different—suggested methods presented in the literature used to obtain mode mixity based on the stress intensity factors are indeed identical. We also present an alternative, simpler quadratic equation to this end. Moreover, a Δ-independent strain energy release based mode mixity can be defined by introducing a “normalizing length parameter.” We show that when the reference length (used for the SIF-based mode mixity) and the normalizing length (used for Δ-independent SERR-based mode mixity) are equal, the two mode mixities are only shifted by a phase angle, depending on the bimaterial parameter ε.  相似文献   
18.
在产品设计规则和计算式中,常存在一些只能在某一范围内取值的待定系数(设为a,且a∈[aL,aH]).a的取值通常受到多种因素的影响和约束,而这种约束往往带有模糊性.为此,首先根据设计规则中各种影响因素对a的模糊约束关系,分别构造两者的备择集以及备择集元素在其论域上的模糊集合,然后基于模糊综合决策方法来确定a.本方法剔除了以往在解决这一问题时,由人来决定a取值的主观性,适用于产品的智能化设计.  相似文献   
19.
A new analytical method is proposed for the analysis of boundary effect in a pipe bend portion loaded by bending moment combined with internal pressure. The proposed method is based on the simplifying hypotheses, which make possible to represent all deformation- and force-related parameters in terms of the tangential displacement assumed in the form of the Fourier series expansion by the circumferential coordinate. A set of quadric differential equations by axial coordinate containing unknown displacement expansion coefficients is derived. We obtained an analytical approximate solution for a pipe bend portion and precise solution for a straight pipe, which are expressed via Krylov functions. We formulate the application procedure for the method of initial parameter, where the values of tangential and longitudinal displacements, axial and tangential forces are used as boundary conditions. We present the equations relating the above-mentioned parameters in the initial and end sections of the pipe bend portion. The results obtained are compared with the available published data. __________ Translated from Problemy Prochnosti, No. 4, pp. 64 – 94, July – August, 2005.  相似文献   
20.
以传递和扭矩和工作转速为设计条件,推导并建立了空气离心式离合器的承载能力方程式及其求解方法,并在此基础上提出了确定该种离合器主要结构参数的具体设计方法和步骤。使其更便于在实际中推广和应用。  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