全文获取类型
收费全文 | 29196篇 |
免费 | 2939篇 |
国内免费 | 1550篇 |
专业分类
电工技术 | 1712篇 |
综合类 | 1735篇 |
化学工业 | 5170篇 |
金属工艺 | 1656篇 |
机械仪表 | 1592篇 |
建筑科学 | 1526篇 |
矿业工程 | 702篇 |
能源动力 | 1307篇 |
轻工业 | 2904篇 |
水利工程 | 991篇 |
石油天然气 | 860篇 |
武器工业 | 312篇 |
无线电 | 3326篇 |
一般工业技术 | 3755篇 |
冶金工业 | 1020篇 |
原子能技术 | 343篇 |
自动化技术 | 4774篇 |
出版年
2024年 | 119篇 |
2023年 | 539篇 |
2022年 | 1210篇 |
2021年 | 1733篇 |
2020年 | 1379篇 |
2019年 | 1233篇 |
2018年 | 1332篇 |
2017年 | 1332篇 |
2016年 | 1261篇 |
2015年 | 1244篇 |
2014年 | 1684篇 |
2013年 | 2436篇 |
2012年 | 2343篇 |
2011年 | 2385篇 |
2010年 | 1933篇 |
2009年 | 1829篇 |
2008年 | 1714篇 |
2007年 | 1727篇 |
2006年 | 1397篇 |
2005年 | 997篇 |
2004年 | 755篇 |
2003年 | 518篇 |
2002年 | 476篇 |
2001年 | 427篇 |
2000年 | 367篇 |
1999年 | 177篇 |
1998年 | 167篇 |
1997年 | 129篇 |
1996年 | 107篇 |
1995年 | 77篇 |
1994年 | 61篇 |
1993年 | 67篇 |
1992年 | 51篇 |
1991年 | 45篇 |
1990年 | 49篇 |
1989年 | 40篇 |
1988年 | 26篇 |
1987年 | 29篇 |
1986年 | 33篇 |
1985年 | 28篇 |
1984年 | 29篇 |
1983年 | 25篇 |
1982年 | 21篇 |
1981年 | 21篇 |
1980年 | 22篇 |
1979年 | 15篇 |
1978年 | 18篇 |
1977年 | 18篇 |
1976年 | 19篇 |
1975年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
Abdelbaki Benamor Brahim Si Ali Mohamed Kheireddine Aroua 《Korean Journal of Chemical Engineering》2008,25(3):451-460
The absorption rates of CO2 into aqueous solutions of Diethanolamine (DEA) with varying concentrations from 0.2 to 4M and temperature range from 293
to 323 K were measured by using a laboratory stirred reactor. The CO2 partial pressure was varied in a range that the reaction would occur in pseudo first order regime. Experimental data were
analyzed and the kinetic parameters associated with the reaction were determined. The activation energy for the deprotonation
of the intermediate zwitterion was estimated at about 11.4 kcal/mol. The contribution of carbamate formation to the overall
absorbed CO2 was experimentally evaluated and found to be of the order of 100%. 相似文献
64.
65.
Ali J. Koshkouei 《International Journal of Adaptive Control and Signal Processing》2008,22(9):859-874
Passivity with sliding mode control for a class of nonlinear systems with and without unknown parameters is considered in this paper. In fact, a method for deriving a nonlinear system with external disturbances to a passive system is considered. Then a passive sliding mode control is designed corresponding to a given storage function. The passivity property guarantees the system stability while sliding mode control techniques assures the robustness of the proposed controller. When the system includes unknown parameters, an appropriate updated law is obtained so that the new transformed system is passive. The passivation property of linear systems with sliding mode is also analysed. The linear and nonlinear theories are applied to a simple pendulum model and the gravity‐flow/pipeline system, respectively. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
66.
真空相变锅炉低排烟温度设计与低温腐蚀 总被引:2,自引:1,他引:1
真空相变锅炉是否会明显发生烟气低温腐蚀,一直众说不一。文章从锅炉发生低温腐蚀的机理人手,通过理论分析计算并通过实践检验,提出了真空相变锅炉虽然不能完全避免低温腐蚀问题,但不论排烟温度是否高于烟气露点,低温腐蚀的程度都很弱的观点;给出了真空相变锅炉沿烟气流程金属壁面的腐蚀速度与壁面温度的关系曲线,和烟气温度低于酸露点时金属壁面的腐蚀速度与壁面温度的关系曲线;同时,文章推荐真空相变锅炉的设计排烟温度取130℃左右的低排烟温度。根据上述观点设计的数百台产品已经过多年实际运行,未发现明显 相似文献
67.
This study describes a laboratory method for the estimation of emission from preservative-treated wood in the different situations where emissions could enter the environment for use classes 3 (not in contact with ground) and 4 and 5 (in contact with the ground, fresh water or sea water) according to OECD Guidelines. Samples of scotch pine sapwood (Pinus sylvestris L.) were treated with CCA (1% and 2%), ACQ-1900 (3% and 7%), ACQ-2200 (2%), Tanalith E 3491 (2% and 2.8%), and Wolmanit CX-8 (2%). 相似文献
68.
Software plays an increasingly important role in modern safety-critical systems. Although, research has been done to integrate software into the classical probabilistic risk assessment (PRA) framework, current PRA practice overwhelmingly neglects the contribution of software to system risk. Dynamic probabilistic risk assessment (DPRA) is considered to be the next generation of PRA techniques. DPRA is a set of methods and techniques in which simulation models that represent the behavior of the elements of a system are exercised in order to identify risks and vulnerabilities of the system. The fact remains, however, that modeling software for use in the DPRA framework is also quite complex and very little has been done to address the question directly and comprehensively. This paper develops a methodology to integrate software contributions in the DPRA environment. The framework includes a software representation, and an approach to incorporate the software representation into the DPRA environment SimPRA. The software representation is based on multi-level objects and the paper also proposes a framework to simulate the multi-level objects in the simulation-based DPRA environment. This is a new methodology to address the state explosion problem in the DPRA environment. This study is the first systematic effort to integrate software risk contributions into DPRA environments. 相似文献
69.
70.
In this paper, flexural behavior of horizontally curved prestressed (posttensioned) box bridges is studied by using three-dimensional and refined finite-element modeling and analysis. Bridge length, section geometry, and material properties are the same in all the models, while angle of curvature varies from 0 to 90°. The results of analysis show that in curved bridges, stress distribution is significantly different in comparison to straight bridges. Also, the level of stresses at some locations of section width is considerably high. It is proposed to vary the distribution of the prestressing tendons across section width in order to optimize the bridge capacity. Results show that by proper redistribution of prestressing in section width, significant reduction in resultant stress is possible. 相似文献