全文获取类型
收费全文 | 26526篇 |
免费 | 2164篇 |
国内免费 | 1508篇 |
专业分类
电工技术 | 1496篇 |
技术理论 | 1篇 |
综合类 | 2705篇 |
化学工业 | 3598篇 |
金属工艺 | 1178篇 |
机械仪表 | 1382篇 |
建筑科学 | 2080篇 |
矿业工程 | 1311篇 |
能源动力 | 1158篇 |
轻工业 | 2026篇 |
水利工程 | 902篇 |
石油天然气 | 5651篇 |
武器工业 | 325篇 |
无线电 | 1009篇 |
一般工业技术 | 1875篇 |
冶金工业 | 1097篇 |
原子能技术 | 299篇 |
自动化技术 | 2105篇 |
出版年
2024年 | 95篇 |
2023年 | 329篇 |
2022年 | 611篇 |
2021年 | 724篇 |
2020年 | 777篇 |
2019年 | 637篇 |
2018年 | 611篇 |
2017年 | 764篇 |
2016年 | 867篇 |
2015年 | 832篇 |
2014年 | 1324篇 |
2013年 | 1615篇 |
2012年 | 1716篇 |
2011年 | 1833篇 |
2010年 | 1363篇 |
2009年 | 1433篇 |
2008年 | 1324篇 |
2007年 | 1726篇 |
2006年 | 1659篇 |
2005年 | 1519篇 |
2004年 | 1236篇 |
2003年 | 1160篇 |
2002年 | 1005篇 |
2001年 | 885篇 |
2000年 | 746篇 |
1999年 | 651篇 |
1998年 | 516篇 |
1997年 | 448篇 |
1996年 | 372篇 |
1995年 | 315篇 |
1994年 | 219篇 |
1993年 | 166篇 |
1992年 | 131篇 |
1991年 | 129篇 |
1990年 | 116篇 |
1989年 | 87篇 |
1988年 | 57篇 |
1987年 | 37篇 |
1986年 | 30篇 |
1985年 | 19篇 |
1984年 | 19篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 6篇 |
1980年 | 11篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1964年 | 5篇 |
1956年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
1.
Xuejun Xie Siying Zhang 《International Journal of Adaptive Control and Signal Processing》2002,16(1):39-59
This paper considers the adaptive pole‐placement control problem for system (1) with unmodelled dynamics ηn dominated by a small constant ε multiplied by a quantity independent of ε but tending to infinity as the past input, output, and noise grow. Using bounded external excitation and randomly varying truncation techniques, we give a design method of adaptive pole‐placement controller. It is shown that the closed‐loop system is globally stable, the estimation error for the parameter contained in the modelled part is of order ε, and the closed‐loop system under the adaptive pole‐placement control law is suboptimal in the sense of $$\mathop{\lim\sup}\limits_{{n\to\infty }}{1\over n}\mathop{\sum}\limits_{i=0}^n{\left({A^{*}(z)y_{n}‐L(z)C(z)w_{n}‐B(z)R(z)y_{n}^{*}}\right)^{2}{\leq}O({\varepsilon}^{2})+\gamma^{2}\mathop{\sum}\limits_{j=1}^q{b_{j}^{2}}}$$\nopagenumbers\end while the SPR condition used usually in other papers is replaced by a stability condition. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
2.
3.
Wilhelm Heinrichs 《Journal of scientific computing》1991,6(1):1-19
We introduce a stabilized treatment of spectral methods. The condition number of the spectral systems is highly improved. Elliptic and biharmonic problems are considered. Suitable interpolants in the case of inhomogeneous Dirichlet boundary conditions are presented. For a direct solver the improvements with respect to rounding error propagation are numerically demonstrated. 相似文献
4.
Fernando J Beltrn F Javier Rivas Olga Gimeno 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(9):973-984
Photocatalytic ozonation (1O3 + VUV + TiO2), ozonation (O3), catalytic ozonation (O3 + TiO2), ozone photolysis (O3 + VUV), photocatalysis (TiO2 + VUV) and photolysis (VUV) have been compared in terms of formation of intermediates, extent of, mineralization (TOC, COD, chloride, nitrate) and kinetics in the aqueous treatment of three phenols (phenol, p‐chlorophenol and p‐nitrophenol). In all cases, photocatalytic ozonation led to lower degradation times for chemical oxygen demand and total organic carbon removal. Intermediates formed were similar in the different oxidation systems with some exceptions. They can be classified into three different types: polyphenols (resorcinol, catechol, hydroquinone), unsaturated carboxylic acids (maleic and fumaric acids) and saturated carboxylic acids (glyoxylic, formic and oxalic acids). First order kinetic equations have been checked for the oxidation processes studied in the case of the parent compound. Rate constants of these systems have also been calculated. Copyright © 2005 Society of Chemical Industry 相似文献
5.
6.
Thermal history and solute precipitation behavior of suspended solution droplets of sodium chloride (NaCl), magnesium sulphate (MgSO4), and zirconium hydroxychloride (ZrO(OH)Cl) evaporating at atmospheric and reduced pressures are studied. Experimental measurements on the variation of droplet diameter, solution concentration, and temperature during the evaporation period are presented and discussed. The results of solute precipitation behavior in solution droplets observed under an optical microscope are displayed and discussed. Results indicate that reducing the pressure (∼ 33 kPa) results in a change in the solution droplet evaporation rate, but the thermal histories of a particular solution droplet are similar at the atmospheric and reduced pressures. At atmospheric and reduced pressures used in this study, the d2 law for solution droplets is valid at early stages of the evaporation and before the solute precipitation initiates. Drying of MgSO4 and ZrO(OH)Cl solution droplets results in the formation of spherical particles, whereas drying of spherical NaCl solution droplets results in the formation of cubic particles. 相似文献
7.
A. Simon Z. Kntor 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2002,190(1-4):351-356
The formation and deposition of particulates by pulsed laser deposition of Si1−xGex semiconductor alloy thin films are discussed. Using Rutherford backscattering spectrometry with micrometer lateral resolution (micro-RBS) the film composition was measured with high accuracy, even in the presence of particulates with a high areal density of 20,000–30,000 particulates per mm2. We show that on impact of a particulate, the part of the thin film which is already deposited probably melts and its Ge content segregates to the surface. 相似文献
8.
An optimal control problem with nonsmooth performance criterion described by a system of ordinary differential equations is considered. Necessary first-order optimality conditions are obtained. 相似文献
9.
10.
Standard Gibbs free energy of formation (ΔGf0), an important property needed in design calculations has been estimated using molar refraction, RM. The linear relationships derived between ΔGf0 and RM tested with the data on 8 series of hydrocarbons at 228 compounds yielded average deviations comparable to the methods cited in recent literature. The method can be used as an alternative to the existing ones, because of its simplicity combined with reasonable accuracy. 相似文献