全文获取类型
收费全文 | 36460篇 |
免费 | 3887篇 |
国内免费 | 2066篇 |
专业分类
电工技术 | 5346篇 |
技术理论 | 2篇 |
综合类 | 3463篇 |
化学工业 | 2993篇 |
金属工艺 | 1486篇 |
机械仪表 | 2368篇 |
建筑科学 | 3920篇 |
矿业工程 | 2043篇 |
能源动力 | 984篇 |
轻工业 | 1679篇 |
水利工程 | 1473篇 |
石油天然气 | 1995篇 |
武器工业 | 198篇 |
无线电 | 2849篇 |
一般工业技术 | 2384篇 |
冶金工业 | 1950篇 |
原子能技术 | 582篇 |
自动化技术 | 6698篇 |
出版年
2024年 | 104篇 |
2023年 | 391篇 |
2022年 | 748篇 |
2021年 | 1084篇 |
2020年 | 1089篇 |
2019年 | 878篇 |
2018年 | 846篇 |
2017年 | 1121篇 |
2016年 | 1173篇 |
2015年 | 1385篇 |
2014年 | 2485篇 |
2013年 | 2455篇 |
2012年 | 2842篇 |
2011年 | 2820篇 |
2010年 | 2098篇 |
2009年 | 2095篇 |
2008年 | 1876篇 |
2007年 | 2301篇 |
2006年 | 2103篇 |
2005年 | 1932篇 |
2004年 | 1701篇 |
2003年 | 1492篇 |
2002年 | 1404篇 |
2001年 | 1226篇 |
2000年 | 980篇 |
1999年 | 807篇 |
1998年 | 543篇 |
1997年 | 464篇 |
1996年 | 431篇 |
1995年 | 348篇 |
1994年 | 256篇 |
1993年 | 211篇 |
1992年 | 157篇 |
1991年 | 125篇 |
1990年 | 84篇 |
1989年 | 88篇 |
1988年 | 59篇 |
1987年 | 42篇 |
1986年 | 26篇 |
1985年 | 21篇 |
1984年 | 21篇 |
1983年 | 23篇 |
1982年 | 23篇 |
1981年 | 14篇 |
1980年 | 8篇 |
1979年 | 12篇 |
1975年 | 2篇 |
1969年 | 2篇 |
1959年 | 2篇 |
1956年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 734 毫秒
71.
动态多目标决策问题的灰色分析方法 总被引:2,自引:0,他引:2
将用于固定时间截面下静态多目标决策的灰色关联理论推广到动态情形,引入局部理想最优效果和整体理想最优效果的概念,提出一种新型的动态多目标决策问题的灰色关联模型,并通过算例说明该方法的合理可行性。 相似文献
72.
D. Roy 《International journal for numerical methods in engineering》2004,61(5):764-790
Sample pathwise numerical integration of noise-driven engineering dynamical systems cannot generally be performed beyond a limited level of accuracy, especially when the noise processes are modelled using (filtered) white noises. Recently, a locally transversal linearization (LTL) strategy has been proposed by the author (Proc Roy Soc London A 2001; 457 :539–566) for direct integration of deterministic and stochastic non-linear dynamical systems. The present effort is focussed on a host of extensions along with detailed theoretical error analyses of the linearization approach, especially as applied to problems in non-linear stochastic engineering dynamics. Thus, to begin with, estimates of local and global error orders in the basic LTL scheme are obtained separately for the displacement and velocity vectors when the system is driven either by a set of additive noises or by an arbitrary combination of (independently evolving) additive and multiplicative noises. Following this, a new family of higher-order LTL schemes is proposed in order to improve upon the basic LTL method and the associated error orders are established. A stepwise implementation of the lower- and higher-order versions of the LTL method, along with certain computational aspects, is also outlined. The proposed schemes are numerically illustrated, to a limited extent, for a single degree-of-freedom (SDOF) and a two degree-of-freedom (TDOF) non-linear engineering systems under additive and/or multiplicative white noise excitations. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
73.
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
74.
75.
介绍了国产螺旋槽密封在进口压缩机上的应用,分析了原进口机械-浮环组合密封的失效原因,叙述了改造后国产浮环螺旋槽组合密封的结构和特点。 相似文献
76.
PDC钻头在东海西湖凹陷的实践与认识 总被引:1,自引:1,他引:0
文章针对在东海西湖凹陷六口井 31 1 .2mm及 2 1 5 .9mm井眼所使用的PDC钻头统计分析 ,并结合笔者自己使用PDC钻头的实践 ,提出使用PDC钻头时注意环节 ,建议针对西湖凹陷地层的特点选择适合该地区的PDC钻头类型 相似文献
77.
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
78.
79.
应用比较几何的方法研究了完备非紧且具有特定曲率条件的黎曼流形,证明了在一定Pinching条件限制下,流形具有有限拓扑型或者微分同胚于R^n。 相似文献
80.
Gouvier W. Drew; Sytsma-Jordan Sara; Mayville Stephen 《Canadian Metallurgical Quarterly》2003,48(3):175
Objective: To evaluate the effects of disability type, job complexity, and public contact on hiring decisions. Design and Participants: An Americans With Disabilities Act (ADA; 1990) fact sheet and matched resumes with vocational and medical histories including chronic mental illness, developmental disability, closed head injury, and back injury were provided to 295 undergraduate business-related majors, who rated the applicants' suitability for 2 job positions and work shifts. Results: Findings indicated disparities in ratings of employability as a function of disability type. Paired comparisons yielded complementary findings, with effects of disability type and Disability Type × Job Complexity, but no effects of public contact. Conclusions: Stereotyping and discrimination in employment decisions apparently persist, more than 10 years after the ADA. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献