全文获取类型
收费全文 | 10391篇 |
免费 | 1640篇 |
国内免费 | 1132篇 |
专业分类
电工技术 | 669篇 |
技术理论 | 2篇 |
综合类 | 1365篇 |
化学工业 | 514篇 |
金属工艺 | 296篇 |
机械仪表 | 505篇 |
建筑科学 | 1407篇 |
矿业工程 | 235篇 |
能源动力 | 196篇 |
轻工业 | 199篇 |
水利工程 | 313篇 |
石油天然气 | 160篇 |
武器工业 | 56篇 |
无线电 | 1235篇 |
一般工业技术 | 1081篇 |
冶金工业 | 244篇 |
原子能技术 | 85篇 |
自动化技术 | 4601篇 |
出版年
2024年 | 56篇 |
2023年 | 199篇 |
2022年 | 254篇 |
2021年 | 364篇 |
2020年 | 372篇 |
2019年 | 362篇 |
2018年 | 362篇 |
2017年 | 448篇 |
2016年 | 457篇 |
2015年 | 602篇 |
2014年 | 758篇 |
2013年 | 799篇 |
2012年 | 887篇 |
2011年 | 903篇 |
2010年 | 741篇 |
2009年 | 716篇 |
2008年 | 649篇 |
2007年 | 730篇 |
2006年 | 536篇 |
2005年 | 500篇 |
2004年 | 409篇 |
2003年 | 329篇 |
2002年 | 316篇 |
2001年 | 242篇 |
2000年 | 198篇 |
1999年 | 175篇 |
1998年 | 125篇 |
1997年 | 116篇 |
1996年 | 96篇 |
1995年 | 72篇 |
1994年 | 54篇 |
1993年 | 57篇 |
1992年 | 53篇 |
1991年 | 30篇 |
1990年 | 37篇 |
1989年 | 24篇 |
1988年 | 22篇 |
1987年 | 17篇 |
1986年 | 12篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 17篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1956年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
The theoretical-and-experimental investigation has been performed on the stability of smooth cylindrical shells of steel with a single local dent. All the shells manufactured using the same process were tested with the fulfillment of identical conditions for observations and measurements. Theoretical calculations were carried out by the mesh method with the use of the nonlinear theory of shells. A comparison of the experimental and theoretical values of the critical loads has been made. The theoretical-and-experimental approach proposed enables one to evaluate the quality of shells by studying local dents and other specific imperfections. 相似文献
32.
An advanced learning system for interactive simulation of patient cases (ISP) is described. The system was designed to meet specific pedagogical needs where student activation and problem orientation were two of the key issues. The system includes features such as video based illness history-taking function using free text input, highly interactive physiological examination procedures, extensive laboratory tests and detailed user feedback. The system was constructed mainly in Authorware Professional, starting more than 10 years ago, and it is now available in refined versions in different languages. Twelve pedagogical and three technical features were initially defined for the project. All of these aims were fulfilled. The ISP system has been successfully used in education, and in international collaboration, including three applicability field tests. The system is also a powerful research tool for studying for instance medical decision-making. 相似文献
33.
We are concerned with the detection of edges—the location and amplitudes of jump discontinuities of piecewise smooth data realized in terms of its discrete grid values. We discuss the interplay between two approaches. One approach, realized in the physical space, is based on local differences and is typically limited to low-order of accuracy. An alternative approach developed in our previous work [Gelb and Tadmor, Appl. Comp. Harmonic Anal., 7, 101–135 (1999)] and realized in the dual Fourier space, is based on concentration factors; with a proper choice of concentration factors one can achieve higher-orders—in fact in [Gelb and Tadmor, SIAM J. Numer. Anal., 38, 1389–1408 (2001)] we constructed exponentially accurate edge detectors. Since the stencil of these highly-accurate detectors is global, an outside threshold parameter is required to avoid oscillations in the immediate neighborhood of discontinuities. In this paper we introduce an adaptive edge detection procedure based on a cross-breading between the local and global detectors. This is achieved by using the minmod limiter to suppress spurious oscillations near discontinuities while retaining high-order accuracy away from the jumps. The resulting method provides a family of robust, parameter-free edge-detectors for piecewise smooth data. We conclude with a series of one- and two-dimensional simulations.To David Gottlieb, on his 60th birthday, with friendship and appreciation. 相似文献
34.
讨论了指数自回归模型的辨识问题,证明了该模型最小二乘估计的目标函数的非凸性,并给出了使该函数为凸的条件,最后给出了辨识该模型的算法及该算法的收敛性,并以数值例子加以说明。 相似文献
35.
用DTA结合XRD了Fe73.5Cu1Nb3Si13.5B9晶合金的晶化动力学。表明,该事金在500℃时析出α-Fe(Si)相。晶化初期激活能最小为242kJ/mol,它随晶化量的增加,在XC为0.4-0.8时,呈极大值为520kJ/mol。在624℃时析出Fe2B相。 相似文献
36.
37.
历史中心区复兴中的地域性问题与对策 总被引:2,自引:0,他引:2
本文以上海思南路47~48街坊改造为例,探讨城市形态更新与居民外迁问题,并期待相关地域性社会对策的出现。 相似文献
38.
无线局域网技术及应用 总被引:9,自引:0,他引:9
无线局域网技术是目前发展迅速的技术,相对于有线局域网有许多优点。随着无线网络产品性能的提高和价格的不断下降,无线局域网技术有着广泛的应用前景。据此对无线局域网的基本概念、特点及其技术作了简单的介绍,提出了无线局域网面向应用的几种解决方案,并对发展前景作了预测。 相似文献
39.
It is shown that the well known two-pass sequential local transformation algorithm for computing a distance transformation in rectangular domains may fail in some convex integer domains, but that a four-pass algorithm is sufficient in all two-dimensional convex domains. For non-convex domains the number of passes necessary is shown to be generally greater. Two propagation algorithms for computing the distance transformation are described and shown theoretically and experimentally to be computationally more efficient than the sequential local transformation algorithm in non-convex domains of complex shape. The relationship of the distance transformation in non-convex domains to some more general transformations is explored. 相似文献
40.
Collaborative work is an important part of tertiary education but it is very difficult to arrange and supervise for extremely large classes of students in their first year. The possibility that computer-mediated communication can be used to facilitate this type of learning is appealing from a pragmatic organisational point of view. This paper explains in detail what a ‘virtual team’ is in the educational context. It reports on an interpretive field study where students taking an introductory course were allowed to choose where and when they did the required collaborative work. The paper discusses the factors that should be taken into account when offering students the option of working as a virtual team. These include factors that influence the students’ choice. The project cannot be considered to have been successful but indicates reasons for the lack of success and suggests contexts in which it would be valuable to repeat the project. The importance of extensive preparation in terms of teaching the students necessary social and technological skills cannot be over emphasised. 相似文献