全文获取类型
收费全文 | 69270篇 |
免费 | 8552篇 |
国内免费 | 5701篇 |
专业分类
电工技术 | 8024篇 |
技术理论 | 3篇 |
综合类 | 10270篇 |
化学工业 | 2848篇 |
金属工艺 | 1558篇 |
机械仪表 | 5452篇 |
建筑科学 | 6058篇 |
矿业工程 | 2894篇 |
能源动力 | 2180篇 |
轻工业 | 4396篇 |
水利工程 | 2884篇 |
石油天然气 | 4860篇 |
武器工业 | 1432篇 |
无线电 | 5068篇 |
一般工业技术 | 4681篇 |
冶金工业 | 1633篇 |
原子能技术 | 362篇 |
自动化技术 | 18920篇 |
出版年
2024年 | 319篇 |
2023年 | 907篇 |
2022年 | 1723篇 |
2021年 | 2041篇 |
2020年 | 2282篇 |
2019年 | 1937篇 |
2018年 | 1898篇 |
2017年 | 2160篇 |
2016年 | 2678篇 |
2015年 | 2856篇 |
2014年 | 4452篇 |
2013年 | 4404篇 |
2012年 | 5410篇 |
2011年 | 5833篇 |
2010年 | 4273篇 |
2009年 | 4434篇 |
2008年 | 4344篇 |
2007年 | 5258篇 |
2006年 | 4581篇 |
2005年 | 3962篇 |
2004年 | 3165篇 |
2003年 | 2744篇 |
2002年 | 2125篇 |
2001年 | 1877篇 |
2000年 | 1579篇 |
1999年 | 1281篇 |
1998年 | 1001篇 |
1997年 | 810篇 |
1996年 | 650篇 |
1995年 | 560篇 |
1994年 | 436篇 |
1993年 | 316篇 |
1992年 | 247篇 |
1991年 | 202篇 |
1990年 | 136篇 |
1989年 | 155篇 |
1988年 | 87篇 |
1987年 | 55篇 |
1986年 | 36篇 |
1985年 | 31篇 |
1984年 | 34篇 |
1983年 | 42篇 |
1982年 | 26篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1979年 | 17篇 |
1978年 | 10篇 |
1977年 | 15篇 |
1975年 | 10篇 |
1963年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
煤层物性测井评价方法初探 总被引:6,自引:1,他引:5
依据煤岩的赋存方式和结构特点,利用电阻率和井径测井资料在不同煤质结构的煤层所表现的差异性,建立了2个指标(即深侧向电阻率与微球电阻率之间的比值,井径与钻头之间的比值)对煤质结构进行了准确的识别。用多元回归的概率模型建立了煤岩镜质反射率的测井计算模式,其结果与已有的煤心分析数据对比,两者具有较好的一致性。在综合分析的基础上,对煤层的重要物性参数煤阶、煤质结构进行了测井评价。 相似文献
102.
化工软测量技术研究进展 总被引:2,自引:0,他引:2
详细说明了软测量技术的含义以及软测量系统的组成。在此基础上,介绍了软测量技术中基于机理分析建模、应用状态观测器建模、应用统计分析建模、神经元网络、模糊技术、以及支持向量机的智能建模等软测量建模理论方法和最新研究成果,之后介绍了小波分析、推断控制算法在软测量数据处理中的应用,最后介绍了基于虚拟仪器开发平台的软测量系统实现技术。 相似文献
103.
The convexity and continuity of fuzzy mappings are defined through a linear ordering and a metric on the set of fuzzy numbers. The local-global minimum property of real-valued convex functions is extended to convex fuzzy mappings. It is proved that a strict local minimizer of a quasiconvex fuzzy mapping is also a strict global minimizer. Characterizations for convex fuzzy mappings and quasiconvex fuzzy mappings are given. In addition, the Weirstrass theorem is extended from real-valued functions to fuzzy mappings. 相似文献
104.
105.
Visual evaluation experiments of color discrimination threshold and suprathreshold color‐difference comparison were carried out using CRT colors based on the psychophysical methods of interleaved staircase and constant stimuli, respectively. A large set of experimental data was generated ranged from threshold to large suprathreshold color difference at the five CIE color centers. The visual data were analyzed in detail for every observer at each visual scale to show the effect of color‐difference magnitude on the observer precision. The chromaticity ellipses from this study were compared with four previous published data, of CRT colors by Cui and Luo, and of surface colors by RIT‐DuPont, Cheung and Rigg, and Guan and Luo, to report the reproducibility of this kind of experiment using CRT colors and the variations between CRT and surface data, respectively. The present threshold data were also compared against the different suprathreshold data to show the effect of color‐difference scales. The visual results were further used to test the three advance color‐difference formulae, CMC, CIE94, and CIEDE2000, together with the basic CIELAB equation. In their original forms or with optimized KL values, the CIEDE2000 outperformed others, followed by CMC, and with the CIELAB and CIE94 the poorest for predicting the combined dataset of all color centers in the present study. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 198–208, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20106 相似文献
106.
107.
本文主要介绍了在动态汽车衡的试验过程中不确定度来源,并以动态试验为例重点介绍了计算各分量的标准不确定度、合成标准不确定度以及扩展不确定度的方法. 相似文献
108.
Stereotype threat research has demonstrated that stereotypes can harm student performance in the face of public evaluation by peers or an experimenter. The current study examined whether stereotypes can also threaten in private settings. Female students completed a math test in 3-person groups, which consisted of either 2 other women (same gender) or 2 men (minority). In addition, students either believed their performance would be broadcasted to their peers (public) or not (private). Results revealed that minority students performed worse than same-gender students in both public and private environments. This finding supports the concept of threatening intellectual environments and shows how far reaching the effects of stereotypes can be. The authors discuss these findings in relation to research on tokenism and to stereotype threat and its educational implications. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
109.
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
110.
In this paper, we present a control methodology for a class of discrete time nonlinear systems that depend on a possibly exogenous scheduling variable. This class of systems consists of an interpolation of nonlinear dynamic equations in strict feedback form, and it may represent systems with a time-varying nonlinear structure. Moreover, this class of systems is able to represent some cases of gain scheduling control, Takagi-Sugeno fuzzy systems, as well as input-output realizations of nonlinear systems which are approximated via localized linearizations. We present two control theorems, one using what we call a “global” approach (akin to traditional backstepping), and a “local” approach, our main result, where backstepping is again used but the control law is an interpolation of local control terms. An aircraft wing rock regulation problem with varying angle of attack is used to illustrate and compare the two approaches. 相似文献