全文获取类型
收费全文 | 11459篇 |
免费 | 892篇 |
国内免费 | 521篇 |
专业分类
电工技术 | 669篇 |
技术理论 | 1篇 |
综合类 | 722篇 |
化学工业 | 1910篇 |
金属工艺 | 548篇 |
机械仪表 | 753篇 |
建筑科学 | 761篇 |
矿业工程 | 405篇 |
能源动力 | 301篇 |
轻工业 | 685篇 |
水利工程 | 192篇 |
石油天然气 | 864篇 |
武器工业 | 92篇 |
无线电 | 1253篇 |
一般工业技术 | 1394篇 |
冶金工业 | 630篇 |
原子能技术 | 125篇 |
自动化技术 | 1567篇 |
出版年
2024年 | 61篇 |
2023年 | 210篇 |
2022年 | 345篇 |
2021年 | 491篇 |
2020年 | 392篇 |
2019年 | 359篇 |
2018年 | 358篇 |
2017年 | 365篇 |
2016年 | 336篇 |
2015年 | 443篇 |
2014年 | 553篇 |
2013年 | 628篇 |
2012年 | 767篇 |
2011年 | 747篇 |
2010年 | 677篇 |
2009年 | 674篇 |
2008年 | 605篇 |
2007年 | 608篇 |
2006年 | 654篇 |
2005年 | 507篇 |
2004年 | 362篇 |
2003年 | 302篇 |
2002年 | 299篇 |
2001年 | 256篇 |
2000年 | 264篇 |
1999年 | 291篇 |
1998年 | 237篇 |
1997年 | 216篇 |
1996年 | 188篇 |
1995年 | 158篇 |
1994年 | 130篇 |
1993年 | 82篇 |
1992年 | 75篇 |
1991年 | 58篇 |
1990年 | 54篇 |
1989年 | 36篇 |
1988年 | 21篇 |
1987年 | 19篇 |
1986年 | 20篇 |
1985年 | 1篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
991.
The fabrication of hierarchically structured Ni(OH)2 monolayer hollow‐sphere arrays with the shell composed of building blocks of nanoflakelets is reported on p. 644 by Weiping Cai and co‐workers. The morphology can be easily controlled by the synthesis parameters, and the arrays show a tunable optical transmission stop band. Tuning can be achieved by changing the size or morphology of the hollow spheres. Such arrays may have potential applications in optical devices, photonic crystals, and as sensors for gas detection. The fabrication of a hierarchically structured Ni(OH)2 monolayer hollow‐sphere array with the shell composed of building blocks of nanoflakelets is demonstrated based on a colloidal monolayer and electrochemical deposition. The morphology can be easily controlled by the colloidal monolayer and deposition parameters. Importantly, such monolayer hollow‐sphere array shows a morphology‐ and size‐dependent tunable optical transmission stop band. This stop band can be easily tuned from 455–1855 nm by changing the size of the hollow spheres between 1000 and 4500 nm, and also fine‐adjusted by changing the deposition time. The array exhibits a nearly incident‐angle‐independent position of the stop band that 3D photonic crystals do not possess. This structure may have potential applications in optical devices, photonic crystals, and sensors for gas detection. 相似文献
992.
In this paper, explicit parametric solutions to the generalized Sylvester matrix equation AX ‐ XF = BY and the regulator matrix equation AX ‐ XF = BY + R are proposed without any transformation and factorization. The proposed solutions are presented in terms of the Krylov matrix of matrix pair (A, B), a symmetric operator and the generalized observability matrix of matrix pair (Z, F) where Z is an arbitrary matrix and is used to denote the degree of freedom in the solution. Due to its elegant form and convenient computation, these proposed solutions will play an important role in solving and analyzing these types of equations in control systems theory. 相似文献
993.
Electric Potential in a Dielectric Sphere Head Produced by a Time-Harmonic Equivalent Current Dipole
Xiao-Yong Duan Shi-Zheng Peng Long-Wu Li Xiao-Chun Liu Rong Xin 《中国电子科技》2007,5(3):268-271
A time-harmonic equivalent current dipole model is proposed to simulate EEG source which deals with the problem concerning the capacitance effect. The expressions of potentials in both homogeneous infinite dielectric medium and dielectric sphere on the electroquasistatic condition are presented. The potential in a 3-layer inhomogeneous spherical head is computed by using this model. The influences on potential produced by time-harmonic character and permittivity are discussed. The results show that potentials in dielectric sphere are affected by frequency and permittivity. 相似文献
994.
995.
Metal‐Organic Frameworks: Bimetallic Metal‐Organic Frameworks: Probing the Lewis Acid Site for CO2 Conversion (Small 17/2016) 下载免费PDF全文
996.
This article addresses an iterative learning control (ILC) design for a class of linear discrete-time systems with multiple time delays. In order to improve the tracking performance, we introduce a P-type high-order iterative learning algorithm that makes use of information from several previous iterations. An initial state learning scheme is proposed to eliminate the effect of the initialization error on the final tracking error. Furthermore, we establish a sufficient condition to ensure asymptotic convergence. A simulation example is also provided to illustrate the effectiveness of the proposed result. 相似文献
997.
998.
999.
直线在中心反射折射摄像机下的像是一条二次曲线.由于存在遮挡,准确地拟合直线像是非常困难的,从而影响了摄像机的标定精度.目前,这一问题仍然没有得到有效的解决.此外,根据中心反射折射摄像机成像模型发现,如果可见弧上图像点的对极点已知,可以大大提高直线像的拟合精度.为此,提出了一种新的拟合直线像的方法,该方法适用于包括抛物反射折射摄像机在内的所有中心反射折射摄像机.首先,推导出一种新的关于对极图像点与摄像机主点之间的关系;然后,通过这种关系建立目标函数,用来优化得到直线像的方程;最后,利用拟合的直线像估计摄像机的内参数,以此评价拟合算法的性能.大量模拟实验和真实实验均验证了拟合算法的有效性,即提出的拟合算法不仅鲁棒,且提高了直线像的拟合精度,进而提高了摄像机的标定精度. 相似文献
1000.
本文分析了"数据库"类课程实验教学存在的问题,提出了实验改革的目标和模块组织的原则,提出了一种模块组织的方案,包含实验名称、实验学时、实验类型、实验要求和实验内容。 相似文献