全文获取类型
收费全文 | 189239篇 |
免费 | 25680篇 |
国内免费 | 19157篇 |
专业分类
电工技术 | 17738篇 |
技术理论 | 9篇 |
综合类 | 24812篇 |
化学工业 | 14641篇 |
金属工艺 | 6640篇 |
机械仪表 | 16579篇 |
建筑科学 | 18077篇 |
矿业工程 | 6455篇 |
能源动力 | 7455篇 |
轻工业 | 5379篇 |
水利工程 | 10192篇 |
石油天然气 | 8673篇 |
武器工业 | 3346篇 |
无线电 | 18238篇 |
一般工业技术 | 18148篇 |
冶金工业 | 5940篇 |
原子能技术 | 1648篇 |
自动化技术 | 50106篇 |
出版年
2024年 | 1081篇 |
2023年 | 3014篇 |
2022年 | 5668篇 |
2021年 | 6350篇 |
2020年 | 6954篇 |
2019年 | 5922篇 |
2018年 | 5843篇 |
2017年 | 7237篇 |
2016年 | 8375篇 |
2015年 | 8734篇 |
2014年 | 11721篇 |
2013年 | 12137篇 |
2012年 | 14212篇 |
2011年 | 14928篇 |
2010年 | 11753篇 |
2009年 | 12049篇 |
2008年 | 12055篇 |
2007年 | 13857篇 |
2006年 | 12060篇 |
2005年 | 10389篇 |
2004年 | 8371篇 |
2003年 | 7261篇 |
2002年 | 5817篇 |
2001年 | 4926篇 |
2000年 | 4340篇 |
1999年 | 3324篇 |
1998年 | 2747篇 |
1997年 | 2334篇 |
1996年 | 2113篇 |
1995年 | 1807篇 |
1994年 | 1512篇 |
1993年 | 1086篇 |
1992年 | 879篇 |
1991年 | 687篇 |
1990年 | 561篇 |
1989年 | 503篇 |
1988年 | 320篇 |
1987年 | 197篇 |
1986年 | 132篇 |
1985年 | 137篇 |
1984年 | 147篇 |
1983年 | 76篇 |
1982年 | 95篇 |
1981年 | 57篇 |
1980年 | 78篇 |
1979年 | 66篇 |
1978年 | 24篇 |
1977年 | 20篇 |
1959年 | 22篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 3 毫秒
61.
关于海面无线传播模型的探讨 总被引:3,自引:0,他引:3
现有文献中一般都认为海面环境的无线传播模型近似于自由空间传播模型,但在实际测试中发现,自由空间模型预测值与实测值差别较大,不能很好地解释此类环境的信号传播。笔者根据多次海面覆盖测试的数据,分析并拟合出了新的海面传播模型。 相似文献
62.
63.
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
64.
It is well recognized that performance changes over time. However, the effect of these changes on overall assessments of performance is largely unknown. In a laboratory experiment, we examined the influence of salient Gestalt characteristics of a dynamic performance profile on supervisory ratings. We manipulated performance trend (flat, linear-improving, linear-deteriorating, U-shaped, and ∩-shaped), performance variation (small, large), and performance mean (negative, zero, positive) within subjects and display format (graphic, tabular) between subjects. Participants received and evaluated information about the weekly performance of different employees over a simulated 26-week period. Results showed strong main effects on performance ratings of both performance mean and performance trend, as well as interactions with display format. Theoretical and practical implications of the results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
65.
66.
A. Yu. Luchka 《Cybernetics and Systems Analysis》2003,39(6):880-888
A modified variational-gradient method is proposed and substantiated for quasilinear operator equations in a Hilbert space. 相似文献
67.
68.
R. LUNDÉN 《Fatigue & Fracture of Engineering Materials & Structures》2007,30(10):905-914
Propagation of small subsurface cracks subjected to shear under repeated rolling contact load is studied. An analytical crack model (Dugdale) with plastic strips at the two crack tips is employed. Compressive stresses promoting crack closure and friction between crack faces are considered. The triaxial stress state is used in the yield criterion. A damage criterion is suggested based on experimental LCF data. In a numerical study, critical crack lengths are found below which propagation of an existing crack should be effectively suppressed. 相似文献
69.
腐败是与政府行政权力相伴生的痼疾,既是一个历史现象又是一个国际现象。贪污腐败和寻租腐败是委托一代理模型中最典型的腐败方式,文章在此基础上对贪污腐败和寻租腐败进行成本一收益分析和市场均衡分析,并探讨治理行政权力腐败的有效途径。 相似文献
70.
Comments on the original article "A New Big Five: Fundamental Principles for an Integrative Science of Personality," by Dan P. McAdams and Jennifer L. Pals (see record 2006-03947-002). McAdams and Pals (April 2006) presented a new model to integrate the field of personality psychology. Cultural and evolutionary factors interact with an individual's basic traits, characteristic adaptations, and life narratives, which in turn are linked to roles, demands, and behaviors. The current authors welcome McAdams and Pals's (2006) model for providing a way to integrate much of the previously disparate empirical findings in personality psychology. However, the current authors also think that McAdams and Pals (2006) overstated the inclusiveness of the model, and more generally, the current authors dispute their assertion that the grand theories of personality can be integrated within a single model. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献