全文获取类型
收费全文 | 40293篇 |
免费 | 6302篇 |
国内免费 | 3082篇 |
专业分类
电工技术 | 10334篇 |
技术理论 | 3篇 |
综合类 | 3813篇 |
化学工业 | 3886篇 |
金属工艺 | 1564篇 |
机械仪表 | 3556篇 |
建筑科学 | 1592篇 |
矿业工程 | 735篇 |
能源动力 | 1476篇 |
轻工业 | 1656篇 |
水利工程 | 636篇 |
石油天然气 | 773篇 |
武器工业 | 498篇 |
无线电 | 6384篇 |
一般工业技术 | 4124篇 |
冶金工业 | 696篇 |
原子能技术 | 277篇 |
自动化技术 | 7674篇 |
出版年
2024年 | 291篇 |
2023年 | 937篇 |
2022年 | 1290篇 |
2021年 | 1603篇 |
2020年 | 1775篇 |
2019年 | 1468篇 |
2018年 | 1443篇 |
2017年 | 1766篇 |
2016年 | 1789篇 |
2015年 | 2029篇 |
2014年 | 2612篇 |
2013年 | 2528篇 |
2012年 | 3013篇 |
2011年 | 3328篇 |
2010年 | 2496篇 |
2009年 | 2475篇 |
2008年 | 2461篇 |
2007年 | 2999篇 |
2006年 | 2534篇 |
2005年 | 2040篇 |
2004年 | 1617篇 |
2003年 | 1405篇 |
2002年 | 1109篇 |
2001年 | 943篇 |
2000年 | 806篇 |
1999年 | 650篇 |
1998年 | 451篇 |
1997年 | 387篇 |
1996年 | 329篇 |
1995年 | 230篇 |
1994年 | 210篇 |
1993年 | 164篇 |
1992年 | 125篇 |
1991年 | 88篇 |
1990年 | 70篇 |
1989年 | 58篇 |
1988年 | 30篇 |
1987年 | 23篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 4篇 |
1980年 | 13篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1974年 | 2篇 |
1964年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
A. F. Kurbatskii 《High Temperature》2004,42(1):79-87
The difference in the turbulent diffusion between the active (heat) and passive (mass) scalars in a thermally stably stratified medium is investigated. The axisymmetric problem is treated on the formation of a turbulent circulation flow above a heated disk and on the turbulent diffusion of a passive scalar (impurity) from a continuous surface source in a stably stratified medium. The results indicate that the thermal stratification causes appreciable differences in the coefficients of turbulent transfer between the active (heat) and passive (mass) scalars. This means that the assumption of the identity of the coefficient of turbulent diffusion of heat and mass, employed in conventional models of turbulence, produces significant errors in estimating the heat and mass transfer in a thermally stably stratified medium. 相似文献
12.
NUMERICALSIMULATIONSOFWHOLEFIELDBEHAVIORFORROUNDBUOYANTJETLiWei,HuaiWen-xin(WuhanUniversityofHydraulicandElectricEngineering,... 相似文献
13.
14.
K. Y. Sze W. K. Chan T. H. H. Pian 《International journal for numerical methods in engineering》2002,55(7):853-878
This paper presents eight‐node solid‐shell elements for geometric non‐linear analysis of elastic shells. To subdue shear, trapezoidal and thickness locking, the assumed natural strain method and an ad hoc modified generalized laminate stiffness matrix are employed. A selectively reduced integrated element is formulated with its membrane and bending shear strain components taken to be constant and equal to the ones evaluated at the element centroid. With the generalized stresses arising from the modified generalized laminate stiffness matrix assumed to be independent from the ones obtained from the displacement, an extended Hellinger–Reissner functional can be derived. By choosing the assumed generalized stresses similar to the assumed stresses of a previous solid element, a hybrid‐stress solid‐shell element is formulated. Commonly employed geometric non‐linear homogeneous and laminated shell problems are attempted and our results are close to those of other state‐of‐the‐art elements. Moreover, the hybrid‐stress element converges more readily than the selectively reduced integrated element in all benchmark problems. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
15.
A serious problem in motion control is the occurrence of torque ripple. Since a direct drive (DD) motor with a magnet rotor uses a rare-earth magnet, the torque ripple is more serious than that of conventional servomotors. This paper presents an auto-compensation of torque ripple using a software-implemented torque observer. The frequency and amplitude of torque ripple can be obtained in the controller by using the estimated torque from an observer, and the autonomous generation of a compensating current component for a torque ripple is possible. The proposed algorithm has been verified by experiments. 相似文献
16.
Amanda LaCoste Karen M. Schaich David Zumbrunnen Kit L. Yam 《Packaging Technology and Science》2005,18(2):77-87
Researchers from Rutgers University and Clemson University have collaborated to develop a concept of using smart blending to generate functional packaging films for the controlled release of active compounds such as antimicrobials, antioxidants and flavour compounds to extend the shelf‐life of food. In this paper, literature results are reviewed to justify the significance of controlled release packaging (CRP) and the research gaps for further development are identified. A major research gap is the lack of packaging materials that can provide the release of active compounds at rates suitable for a wide range of food packaging applications. Smart blending is a promising technology for bridging this research gap. To fully realize the potentials of smart blending, a systematic approach for developing CRP using smart blending is also presented. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
17.
论述了海洋钻井平台的功率因数及改善功率因数的重要意义和必要性,对实时无功功率动态补偿装置作了介绍,并对实施功率补偿后取得的效果和经济测算作了分析,提出了提高功率因数,进行功率补偿的推广应用建议。 相似文献
18.
针对当前国内长途传输光缆系统在扩容过程中,因光信号色散而影响传输质量的现象,结合实际工程建设,分析了光信号色散的危害及其成因,并提出了相应的解决办法及建议。 相似文献
19.
20.
聚丙烯催化剂的研发进展 总被引:5,自引:4,他引:1
综述了用于丙烯聚合的Ziegler-Natta催化剂在给电子体技术及催化剂制备工艺等方面,茂金属催化剂在制备丙烯均聚物、丙烯共聚物及特殊聚丙烯等方面,非茂单活性中心催化剂在丙烯活性聚合、丙烯与极性单体共聚及水介质聚合等方面的研发进展;讨论了聚丙烯催化剂的前景。 相似文献