全文获取类型
收费全文 | 62289篇 |
免费 | 6066篇 |
国内免费 | 2671篇 |
专业分类
电工技术 | 3614篇 |
技术理论 | 4篇 |
综合类 | 3656篇 |
化学工业 | 10653篇 |
金属工艺 | 3579篇 |
机械仪表 | 4254篇 |
建筑科学 | 4331篇 |
矿业工程 | 1753篇 |
能源动力 | 2028篇 |
轻工业 | 4695篇 |
水利工程 | 1178篇 |
石油天然气 | 2839篇 |
武器工业 | 553篇 |
无线电 | 7647篇 |
一般工业技术 | 8333篇 |
冶金工业 | 2889篇 |
原子能技术 | 909篇 |
自动化技术 | 8111篇 |
出版年
2024年 | 283篇 |
2023年 | 1092篇 |
2022年 | 1910篇 |
2021年 | 2689篇 |
2020年 | 2027篇 |
2019年 | 1807篇 |
2018年 | 2096篇 |
2017年 | 2188篇 |
2016年 | 2133篇 |
2015年 | 2646篇 |
2014年 | 3297篇 |
2013年 | 3966篇 |
2012年 | 4493篇 |
2011年 | 4786篇 |
2010年 | 4101篇 |
2009年 | 3952篇 |
2008年 | 3668篇 |
2007年 | 3332篇 |
2006年 | 3128篇 |
2005年 | 2643篇 |
2004年 | 2031篇 |
2003年 | 1851篇 |
2002年 | 1903篇 |
2001年 | 1623篇 |
2000年 | 1319篇 |
1999年 | 1274篇 |
1998年 | 921篇 |
1997年 | 724篇 |
1996年 | 671篇 |
1995年 | 584篇 |
1994年 | 404篇 |
1993年 | 340篇 |
1992年 | 277篇 |
1991年 | 192篇 |
1990年 | 162篇 |
1989年 | 106篇 |
1988年 | 111篇 |
1987年 | 58篇 |
1986年 | 66篇 |
1985年 | 37篇 |
1984年 | 26篇 |
1983年 | 20篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 14篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1970年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
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
33.
34.
35.
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
36.
37.
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
38.
39.
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
40.
Mani Balamurugan Hui‐Yun Jeong Venkata Surya Kumar Choutipalli Jung Sug Hong Hongmin Seo Natarajan Saravanan Jun Ho Jang Kang‐Gyu Lee Yoon Ho Lee Sang Won Im Venkatesan Subramanian Sun Hee Kim Ki Tae Nam 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(25)
The electrochemical reduction of carbon dioxide (CO2) to hydrocarbons is a challenging task because of the issues in controlling the efficiency and selectivity of the products. Among the various transition metals, copper has attracted attention as it yields more reduced and C2 products even while using mononuclear copper center as catalysts. In addition, it is found that reversible formation of copper nanoparticle acts as the real catalytically active site for the conversion of CO2 to reduced products. Here, it is demonstrated that the dinuclear molecular copper complex immobilized over graphitized mesoporous carbon can act as catalysts for the conversion of CO2 to hydrocarbons (methane and ethylene) up to 60%. Interestingly, high selectivity toward C2 product (40% faradaic efficiency) is achieved by a molecular complex based hybrid material from CO2 in 0.1 m KCl. In addition, the role of local pH, porous structure, and carbon support in limiting the mass transport to achieve the highly reduced products is demonstrated. Although the spectroscopic analysis of the catalysts exhibits molecular nature of the complex after 2 h bulk electrolysis, morphological study reveals that the newly generated copper cluster is the real active site during the catalytic reactions. 相似文献