全文获取类型
收费全文 | 44744篇 |
免费 | 6444篇 |
国内免费 | 4776篇 |
专业分类
电工技术 | 6458篇 |
技术理论 | 2篇 |
综合类 | 5384篇 |
化学工业 | 3593篇 |
金属工艺 | 1114篇 |
机械仪表 | 2546篇 |
建筑科学 | 3681篇 |
矿业工程 | 1314篇 |
能源动力 | 1329篇 |
轻工业 | 2034篇 |
水利工程 | 1340篇 |
石油天然气 | 2697篇 |
武器工业 | 623篇 |
无线电 | 6167篇 |
一般工业技术 | 4044篇 |
冶金工业 | 1469篇 |
原子能技术 | 703篇 |
自动化技术 | 11466篇 |
出版年
2024年 | 235篇 |
2023年 | 768篇 |
2022年 | 1378篇 |
2021年 | 1756篇 |
2020年 | 1746篇 |
2019年 | 1485篇 |
2018年 | 1414篇 |
2017年 | 1681篇 |
2016年 | 1900篇 |
2015年 | 2111篇 |
2014年 | 2891篇 |
2013年 | 3225篇 |
2012年 | 3413篇 |
2011年 | 3771篇 |
2010年 | 2833篇 |
2009年 | 2874篇 |
2008年 | 2797篇 |
2007年 | 3100篇 |
2006年 | 2727篇 |
2005年 | 2324篇 |
2004年 | 1901篇 |
2003年 | 1601篇 |
2002年 | 1338篇 |
2001年 | 1165篇 |
2000年 | 951篇 |
1999年 | 797篇 |
1998年 | 658篇 |
1997年 | 557篇 |
1996年 | 498篇 |
1995年 | 401篇 |
1994年 | 313篇 |
1993年 | 245篇 |
1992年 | 216篇 |
1991年 | 153篇 |
1990年 | 162篇 |
1989年 | 128篇 |
1988年 | 111篇 |
1987年 | 50篇 |
1986年 | 30篇 |
1985年 | 25篇 |
1984年 | 46篇 |
1983年 | 19篇 |
1982年 | 20篇 |
1981年 | 18篇 |
1980年 | 16篇 |
1964年 | 11篇 |
1961年 | 8篇 |
1960年 | 12篇 |
1959年 | 10篇 |
1955年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
压密注浆及其在地基加固中的应用 总被引:1,自引:0,他引:1
在简单介绍了压密注浆工法的加固机理、影响被加固土体强度的因素的基础上,结合工程实例介绍了压缩注浆工法的工程应用情况。 相似文献
92.
A. A. Kherani B. J. Prabhu K. E. Avrachenkov E. Altman 《Telecommunication Systems》2005,30(4):321-350
We study an Adaptive Window Protocol (AWP) with general increase and decrease profiles in the presence of window dependent
random losses. We derive a steady-state Kolmogorov equation, and then obtain its solution in analytic form for particular
TCP versions proposed for high speed networks, such as Scalable TCP and HighSpeed TCP. We also relate window evolution under
an AWP to workload process in queueing systems; this observation gives us a way to compare various AWP protocols. 相似文献
93.
Bedich ika Helena Bendov Ivan Macha
《Chemical Engineering and Processing: Process Intensification》2005,44(12):1312-1319
A procedure has been proposed for the estimation of the terminal falling velocity of non-spherical particles moving in a Carreau model fluid in the transition flow region. The procedure is based on a modification of the relationship formerly developed for the fall of spherical particles including the particle dynamic shape factor. The suitability of the proposed procedure has been confirmed by good agreement between experimental and calculated terminal falling velocity data. In the experiments, the terminal falling velocity of short cylinders and rectangular prisms in polymer solutions of different measure of shear thinning and elasticity has been measured. 相似文献
94.
The stress intensity factors for a short crack partially penetrating an inclusion of arbitrary shape
Some approximate solutions for predicting the stress intensity factor of a short crack penetrating an inclusion of arbitrary
shape have been developed under mode I and mode II loading conditions. The derivation of the fundamental formula is based
on the transformation toughening theory. The transformation strains in the inclusion are induced by the crack-tip field and
remotely applied stresses, and approximately evaluated by the Eshelby equivalent inclusion theory. As validated by detailed
finite element (FE) analyses, the developed solutions have good accuracy for different inclusion shape and for a wide range
of modulus ratio between inclusion and matrix material. 相似文献
95.
ZHU Liye FANG Yuan ZHANG Weidong 《机械工程学报(英文版)》2008,21(1):91-93
According to a type of normal nonlinear system, an indirect adaptive fuzzy (IAF) controller has been applied to those systems where no accurate mathematical models of the systems under control are available. To satisfy with system performance, an indirect accelerated adaptive fuzzy (IAAF) controller is proposed, and its general form is presented. The general form IAAF controller ensures necessary control criteria and system's global stability using Lyapunov Theorem. It has been proved that the close-loop system error converges to a small neighborhood of equilibrium point. The optimal IAAF controller is derived to guarantee the process's shortest settling time. Simulation results indicate the IAAF controller make the system more stable, accurate, and fast. 相似文献
96.
97.
多测井曲线的综合处理合成 总被引:9,自引:0,他引:9
测井曲线是地质分层的基础,但在利用单一测井曲线解决复杂地质问题时也存在多解性和局限性。为克服多解性,人们采用多种测井曲线进行地质分层,提高了分层的精度。本文在此基础上提出把多条曲线分别赋予不同的加权因子,然后进行归一化处理,形成一条标准综合参数测井曲线。此综合参数曲线突出了所选的多条测井曲线的公共信息,减少或削弱了单一测井曲线中的偶然误差,提高了综合后测井资料的可信度。该方法可应用于地质分层、岩性分析、含油气预测等诸多领域。应用时要注意,并非所选择的测井曲线种类越多越好,而是要选择那些最能反映地层单元特征信息的测井曲线。 相似文献
98.
S135钻杆钢在钻井液中的氧腐蚀行为 总被引:4,自引:0,他引:4
基于系统的理论分析和现场腐蚀产物的XRD分析,揭示了S135钻杆钢在3%NaCl溶液中的氧腐蚀机理。为研究腐蚀因素与腐蚀速率的关系,通过室内高压釜动态模拟实验,分别研究了钻井液中含氧量、钻井液温度、钻井液流速和钻井液盐浓度对S135钻杆钢的氧腐蚀速率影响规律。实验研究结果表明(1)3%NaCl盐水钻井液对S135钻杆钢的腐蚀主要是氧去极化作用所致;(2)钻井液含氧量和钻井液流速的增加会加快钻杆钢的氧腐蚀速率,而钻井液温度和含盐量对钻杆钢的氧腐蚀速率具有双重作用。 相似文献
99.
影响混凝土强度的因素及控制措施 总被引:3,自引:3,他引:0
分析了水泥强度等级、水灰比和骨料质量等内因,及施工条件、养护温度、湿度、龄期等外因对混凝土强度的影响,并提出了控制混凝土强度的相应措施,以确保混凝土强度符合设计及施工要求,从而保证建筑物结构安全。 相似文献
100.
Ahmadreza Momeni Amir G. Aghdam 《International Journal of Adaptive Control and Signal Processing》2007,21(10):885-910
Most of the existing switching control techniques are developed specifically for finite-dimensional linear time-invariant (LTI) systems. In many practical applications, however, it is essential to take time delay into consideration in the modelling as the control system can be highly sensitive to delay. In this paper, a multi-model switching control algorithm is proposed for retarded time-delay systems. It is assumed that the plant is represented by a family of known multi-input multi-output, observable, LTI models with multiple delays in the states, and that corresponding to each model in the known family, there exists a high-performance finite-dimensional LTI controller. In addition, it is supposed that a bound on the magnitude of the external inputs and disturbances is available. It is then shown that the proposed switching controller can stabilize the uncertain system, and that under some mild conditions, output tracking can be achieved in the given problem setting. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献