全文获取类型
收费全文 | 82509篇 |
免费 | 8822篇 |
国内免费 | 5253篇 |
专业分类
电工技术 | 6450篇 |
技术理论 | 4篇 |
综合类 | 6709篇 |
化学工业 | 12240篇 |
金属工艺 | 5332篇 |
机械仪表 | 5805篇 |
建筑科学 | 6380篇 |
矿业工程 | 2880篇 |
能源动力 | 2585篇 |
轻工业 | 6957篇 |
水利工程 | 2214篇 |
石油天然气 | 3761篇 |
武器工业 | 921篇 |
无线电 | 9150篇 |
一般工业技术 | 8547篇 |
冶金工业 | 3653篇 |
原子能技术 | 1618篇 |
自动化技术 | 11378篇 |
出版年
2024年 | 394篇 |
2023年 | 1361篇 |
2022年 | 2803篇 |
2021年 | 3812篇 |
2020年 | 2767篇 |
2019年 | 2248篇 |
2018年 | 2524篇 |
2017年 | 2644篇 |
2016年 | 2457篇 |
2015年 | 3610篇 |
2014年 | 4556篇 |
2013年 | 5224篇 |
2012年 | 6316篇 |
2011年 | 6653篇 |
2010年 | 5992篇 |
2009年 | 5735篇 |
2008年 | 5497篇 |
2007年 | 5292篇 |
2006年 | 4888篇 |
2005年 | 3944篇 |
2004年 | 2939篇 |
2003年 | 2461篇 |
2002年 | 2548篇 |
2001年 | 2255篇 |
2000年 | 1714篇 |
1999年 | 1372篇 |
1998年 | 865篇 |
1997年 | 666篇 |
1996年 | 621篇 |
1995年 | 548篇 |
1994年 | 387篇 |
1993年 | 334篇 |
1992年 | 258篇 |
1991年 | 189篇 |
1990年 | 154篇 |
1989年 | 101篇 |
1988年 | 112篇 |
1987年 | 54篇 |
1986年 | 69篇 |
1985年 | 30篇 |
1984年 | 33篇 |
1983年 | 16篇 |
1982年 | 16篇 |
1981年 | 23篇 |
1980年 | 14篇 |
1979年 | 19篇 |
1977年 | 8篇 |
1970年 | 7篇 |
1959年 | 18篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Zhuo Shi Ningning Dong Dingfeng Zhang Xiaofang Jiang Guanxin Du Shichao Lv Jiejie Chen Jun Wang Shifeng Zhou 《Journal of the American Ceramic Society》2019,102(7):3965-3971
The construction of nonlinear optical materials featuring asymmetric transmission of light is of great technological importance for various applications, including optical switching and optical power limiting. A significant challenge is the scalable fabrication of material candidates with good photochemical stability, high optical transmittance, and excellent optical limiting performance. Here, we present a nanocrystallization avenue for constructing hybrid optical limiting materials that exhibit ultrafast and robust optical limiting performance. The experimental results show that the controllable relaxation of a niobate glass may lead to the clustering of Nb-O units and contracting of the bandgap. It results in the notable improvement in nonlinear optical properties, including the enhanced saturation irradiance (380 GW/cm2), doubly increased nonlinear coefficient, and decreased limiting threshold (200 GW/cm2). Our results suggest a promising material that exhibits promising applications for protecting eyes and sensitive components from laser-induced damage. 相似文献
42.
棋盘格图像在摄像机标定中有非常广泛的应用,对于复杂环境且测量精度要求非常高的场合,会需要特定的且有一定复杂度的算法,但通常情况下,使用这样的标定系统是没有必要的,且会让初次应用的人觉得困难。这里提供一套应用简单,快速,对棋盘格图像具有旋转不变性,良好的鲁棒性,且对非复杂环境具有高精度的标定系统。所有算法均是在前辈们的算法上稍作改变而来,应用效果非常好。 相似文献
43.
44.
45.
Jianhuai Dong Zhixuan Dong 《International Journal of Adaptive Control and Signal Processing》2020,34(10):1466-1482
This article studies the optimal filtering and control for wireless networked control systems (WNCSs). In WNCSs, packets may be lost in both control and feedback channels and user datagram protocol is usually used to improve the performance of the real-time control. Relevant literature indicates that the conventional optimal filtering for such a system cannot be applied in practice due to the complex calculation with Gaussian mixtures. This paper proposes a novel scheme to realize the optimal filtering and the linear quadratic Gaussian control for WNCSs, in which the controlled node performs a local estimation and the remote-control node performs the final estimation and control, and a synchronization of two estimators is guaranteed by a communication mechanism. An optimal filtering algorithm is developed, the stability condition of the filtering error covariance is obtained, optimal finite-horizon and infinite-horizon control are derived, and the stability of the closed-loop control system is proved. Numerical simulations show the validity and feasibility of the theoretical results. 相似文献
46.
This paper considers a novel distributed iterative learning consensus control algorithm based on neural networks for the control of heterogeneous nonlinear multiagent systems. The system's unknown nonlinear function is approximated by suitable neural networks; the approximation error is countered by a robust term in the control. Two types of control algorithms, both of which utilize distributed learning laws, are provided to achieve consensus. In the provided control algorithms, the desired reference is considered to be an unknown factor and then estimated using the associated learning laws. The consensus convergence is proven by the composite energy function method. A numerical simulation is ultimately presented to demonstrate the efficacy of the proposed control schemes. 相似文献
47.
48.
Tuntun Wang Dr. Sitansu Sekhar Nanda Dr. Georgia C. Papaefthymiou Prof. Dong Kee Yi 《Chembiochem : a European journal of chemical biology》2020,21(9):1254-1264
The extracellular matrix (ECM) is a macromolecular network that can provide biochemical and structural support for cell adhesion and formation. It regulates cell behavior by influencing biochemical and physical cues. It is a dynamic structure whose components are modified, degraded, or deposited during connective tissue development, giving tissues strength and structural integrity. The physical properties of the natural ECM environment control the design of naturally or synthetically derived biomaterials to guide cell function in tissue engineering. Tissue engineering is an important field that explores physical cues of the ECM to produce new viable tissue for medical applications, such as in organ transplant and organ recovery. Understanding how the ECM exerts physical effects on cell behavior, when cells are seeded in synthetic ECM scaffolds, is of utmost importance. Herein we review recent findings in this area that report on cell behaviors in a variety of ECMs with different physical properties, i.e., topology, geometry, dimensionality, stiffness, and tension. 相似文献
50.
Wang Wencheng Yuan Xiaohui Wu Xiaojin Dong Yihua 《Multimedia Tools and Applications》2020,79(37-38):27185-27203
Multimedia Tools and Applications - As the key parameter of dehazing algorithms, airlight value directly affect the calculation accuracy of sky region, and any deviation will lead to the chromatic... 相似文献