全文获取类型
收费全文 | 49140篇 |
免费 | 4571篇 |
国内免费 | 2217篇 |
专业分类
电工技术 | 2884篇 |
技术理论 | 1篇 |
综合类 | 3624篇 |
化学工业 | 8270篇 |
金属工艺 | 2715篇 |
机械仪表 | 3145篇 |
建筑科学 | 3576篇 |
矿业工程 | 1326篇 |
能源动力 | 1281篇 |
轻工业 | 3969篇 |
水利工程 | 1086篇 |
石油天然气 | 2870篇 |
武器工业 | 425篇 |
无线电 | 5486篇 |
一般工业技术 | 5696篇 |
冶金工业 | 2243篇 |
原子能技术 | 683篇 |
自动化技术 | 6648篇 |
出版年
2024年 | 174篇 |
2023年 | 789篇 |
2022年 | 1460篇 |
2021年 | 2043篇 |
2020年 | 1615篇 |
2019年 | 1352篇 |
2018年 | 1431篇 |
2017年 | 1676篇 |
2016年 | 1476篇 |
2015年 | 2184篇 |
2014年 | 2766篇 |
2013年 | 3252篇 |
2012年 | 3580篇 |
2011年 | 3628篇 |
2010年 | 3323篇 |
2009年 | 3094篇 |
2008年 | 3005篇 |
2007年 | 2880篇 |
2006年 | 2792篇 |
2005年 | 2333篇 |
2004年 | 1610篇 |
2003年 | 1276篇 |
2002年 | 1212篇 |
2001年 | 996篇 |
2000年 | 943篇 |
1999年 | 896篇 |
1998年 | 706篇 |
1997年 | 597篇 |
1996年 | 582篇 |
1995年 | 457篇 |
1994年 | 368篇 |
1993年 | 274篇 |
1992年 | 238篇 |
1991年 | 170篇 |
1990年 | 110篇 |
1989年 | 103篇 |
1988年 | 101篇 |
1987年 | 47篇 |
1986年 | 58篇 |
1985年 | 36篇 |
1984年 | 26篇 |
1983年 | 20篇 |
1982年 | 21篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1979年 | 12篇 |
1977年 | 10篇 |
1976年 | 23篇 |
1975年 | 10篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Yong Xia Rongming Lin 《International journal for numerical methods in engineering》2004,59(1):153-172
Order reduction is a computationally efficient method to estimate some lowest eigenvalues and the corresponding eigenvectors of large structural systems by reducing the order of the original model to a smaller one. But its accuracy is limited to a small range of frequencies that depends on the selection of the retained degrees of freedom. This paper proposes a new iterative order reduction (IOR) technique to obtain accurately the eigensolutions of large structural systems. The technique retains all the inertia terms associated with the removed degrees of freedom. This hence leads to the reduced mass matrix being in an iterated form and the reduced stiffness matrix constant. From these mass and stiffness matrices, the eigensolutions of the reduced system can be obtained iteratively. On convergence the reduced system reproduces the eigensolutions of the original structure. A proof of the convergence property is also presented. Applications of the method to a practical GARTEUR structure as well as a plate have demonstrated that the proposed method is comparable to the commonly used Subspace Iteration method in terms of numerical accuracy. Moreover, it has been found that the proposed method is computationally more efficient than the Subspace Iteration method. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
102.
随着电容测量技术的迅速发展,电容传感器在非电量测量和自动检测中得到广泛应用,但它在使用过程中也存在一些问题,针对在使用电容传感器过程中存在的几个问题,从电容传感器的原理和工作过程两个方面进行了讨论,并提出行之有效的处理方法。 相似文献
103.
J. Chen J. B. Xu K. Xue J. An N. Ke W. Cao H. B. Xia J. Shi D. C. Tian 《Microelectronics Reliability》2005,45(1):137-142
Transition-metal compound TiC60 thin films were grown by co-deposition from two separated sources of fullerene C60 powder and titanium. Study of structural properties of the films, by Raman spectroscopy, atomic force microscopy, and scanning tunneling spectroscopy reveals that the films have a deformed C60 structure with certain amount of sp3 bonds and a rough surface with a large number of nanoclusters. z–V tunnelling spectroscopic measurements suggest that several charge transport mechanisms are involved in as the tip penetrates into the thin film. Conventional field electron emission (FEE) measurements show a high emission current density of 10 mA/cm2 and a low turn-on field less than 8 V/μm, with the field enhancement factors being 659 and 1947 for low-field region and high-field region, respectively. By exploiting STM tunneling spectroscopy, local FEE on nanometer scale has also been characterized in comparison with the conventional FEE. The respective field enhancement factors are estimated to be 99–355 for a gap varying from 36 to 6 nm. The enhanced FEE of TiC60 thin films can be ascribed to structural variation of C60 in the films and the electrical conducting paths formed by titanium nanocrystallites embedded in C60 matrix. 相似文献
104.
Du Young Choi Long Mei Jin Dexian Wang Kyung Ho Row 《Korean Journal of Chemical Engineering》2005,22(3):465-469
High-performance frontal analysis (HPFA) was used for a protein binding study of isoflavones (daidzein, genistin, and genistein),
enantiomers of perillyl alcohol and S-ibuprofen to human serum albumin (HSA). The analyses were performed on a Develosil and
Inertsil 100-Diol-5 column (10 cm×4.6mm). Sodium phosphate solution (pH 7.4, ionic strength 0.17) was used as the mobile phase
at a flow rate of 1 ml/min. To ensure the drug to be eluted as a trapezoidal peak with a plateau, injection volumes were each
fixed up the zonal profile with an evident plateau appears. The unbound drug concentration was determined from a plateau height
of the plateau region after that experimental data were fitted by Scatchard equation. The binding constants (K) and total
binding affinities (nK) of drugs to HSA were calculated, respectively. 相似文献
106.
107.
108.
109.
本文分析了"十五"期间农村水电发展情况,对"十一五"农村水电发展政策环境及增长情况进行了预测。 相似文献
110.
大坝洪水漫顶风险评估 总被引:2,自引:1,他引:1
洪水漫顶是导致大坝溃坝的主要原因之一,大坝洪水漫顶风险评估是大坝风险评估的重要组成部分。为此,简要介绍了大坝洪水漫顶的风险模型,并通过实例详细地讨论了模型中各有关参数的不确定性处理方法,探讨了入库洪水的不确定性对洪水漫顶风险率的影响以及按规范设计的大坝的防洪能力问题。 相似文献