全文获取类型
收费全文 | 15178篇 |
免费 | 1892篇 |
国内免费 | 1074篇 |
专业分类
电工技术 | 294篇 |
技术理论 | 1篇 |
综合类 | 1340篇 |
化学工业 | 1086篇 |
金属工艺 | 684篇 |
机械仪表 | 854篇 |
建筑科学 | 1177篇 |
矿业工程 | 2964篇 |
能源动力 | 311篇 |
轻工业 | 949篇 |
水利工程 | 622篇 |
石油天然气 | 237篇 |
武器工业 | 56篇 |
无线电 | 980篇 |
一般工业技术 | 2130篇 |
冶金工业 | 974篇 |
原子能技术 | 237篇 |
自动化技术 | 3248篇 |
出版年
2024年 | 33篇 |
2023年 | 158篇 |
2022年 | 413篇 |
2021年 | 560篇 |
2020年 | 642篇 |
2019年 | 425篇 |
2018年 | 388篇 |
2017年 | 440篇 |
2016年 | 492篇 |
2015年 | 555篇 |
2014年 | 959篇 |
2013年 | 982篇 |
2012年 | 1242篇 |
2011年 | 1221篇 |
2010年 | 982篇 |
2009年 | 969篇 |
2008年 | 1007篇 |
2007年 | 1001篇 |
2006年 | 864篇 |
2005年 | 731篇 |
2004年 | 684篇 |
2003年 | 547篇 |
2002年 | 480篇 |
2001年 | 384篇 |
2000年 | 352篇 |
1999年 | 313篇 |
1998年 | 238篇 |
1997年 | 204篇 |
1996年 | 205篇 |
1995年 | 154篇 |
1994年 | 106篇 |
1993年 | 96篇 |
1992年 | 56篇 |
1991年 | 65篇 |
1990年 | 40篇 |
1989年 | 27篇 |
1988年 | 24篇 |
1987年 | 24篇 |
1986年 | 14篇 |
1985年 | 20篇 |
1984年 | 17篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1960年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
建筑构件积木式CAD软件研究 总被引:4,自引:0,他引:4
西方以混凝土坝内廓道施工样图设计阶段为例,论述水工建筑件积木式CAD软件的必要性和积木模块CAD软件的具体实现方法。 相似文献
62.
63.
Elias G. Abu‐Saba William M. McGinley Raymond C. Montgomery 《Canadian Metallurgical Quarterly》1991,4(4):347-354
As the manned exploration of space continues, many complex structural components are being developed to construct the orbital platforms that will be used to house communication hardware, personnel, and manufacturing complexes. These components are extremely flexible and complex in their behavior. There is a need for a simple method for determining the dynamic characteristics of these space structures with a minimum of effort. A mathematical model of one of these structural elements, an articulating truss beam, has been developed to predict its dynamic response. Assumptions of the force interaction between the beam elements and the joints have been made for using this model. Algorithms are provided to determine the flexibility matrix of the truss beam for use in the equation of motion. The natural frequencies obtained from using this method are compared with those obtained by the finite element method. An experimental procedure is planned to validate the results from the theoretical method. 相似文献
64.
Thomas J. R. Hughes Arif Masud Isaac Harari 《International journal for numerical methods in engineering》1995,38(19):3193-3210
Finite element methods for dynamic analysis employing elements with drilling degrees of freedom are presented. The formulation is based on a variational principle in which displacements and rotations are interpolated independently. The issue of zero masses corresponding to rotational degrees of freedom is addressed and techniques for defining consistent and lumped rotational mass matrices are presented. 相似文献
65.
Hoon C. Park Chahngmin Cho Sung W. Lee 《International journal for numerical methods in engineering》1995,38(24):4101-4122
The present paper describes an assumed strain finite element model with six degrees of freedom per node designed for geometrically non-linear shell analysis. An important feature of the present paper is the discussion on the spurious kinematic modes and the assumed strain field in the geometrically non-linear setting. The kinematics of deformation is described by using vector components in contrast to the conventional formulation which requires the use of trigonometric functions of rotational angles. Accordingly, converged solutions can be obtained for load or displacement increments that are much larger than possible with the conventional formulation with rotational angles. In addition, a detailed study of the spurious kinematic modes and the choice of assumed strain field reveals that the same assumed strain field can be used for both geometrically linear and non-linear cases to alleviate element locking while maintaining kinematic stability. It is strongly recommended that the element models, described in the present paper, be used instead of the conventional shell element models that employ rotational angles. 相似文献
66.
Becker D. Vaughn; Kenrick Douglas T.; Neuberg Steven L.; Blackwell K. C.; Smith Dylan M. 《Canadian Metallurgical Quarterly》2007,92(2):179
Findings of 7 studies suggested that decisions about the sex of a face and the emotional expressions of anger or happiness are not independent: Participants were faster and more accurate at detecting angry expressions on male faces and at detecting happy expressions on female faces. These findings were robust across different stimulus sets and judgment tasks and indicated bottom-up perceptual processes rather than just top-down conceptually driven ones. Results from additional studies in which neutrally expressive faces were used suggested that the connections between masculine features and angry expressions and between feminine features and happy expressions might be a property of the sexual dimorphism of the face itself and not merely a result of gender stereotypes biasing the perception. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
67.
用共沉淀法制备了TiO2-ZrO2复合氧化物载体,BET,DTA,XRD表征结果表明,该复合载体具有较大的比表面和较好的热稳定性,对于环己酮肟气相Beckmann重排反应制己内酰胺,用复合载体制备的B2O3/TiO2-ZrO2催化剂,比分别以TiO2,ZrO2为载体所制备的B2O3/TiO2和B2O3/ZrO2催化剂具有更高的活性和选择性,实验表明,催化剂表面中等强度的酸位是环己酮肟气相Beckmann重排反应的有效活性中心。 相似文献
68.
69.
70.
Simulation of water and nitrogen dynamics in soils during wastewater applications by using a finite-element model 总被引:4,自引:0,他引:4
Vassilis Z. Antonopoulos 《Water Resources Management》1993,7(3):237-251
A mathematical model was developed to simulate water movement, mass transport, and nitrogen transformations in soils during wastewater applications. The model is one-dimensional and based on the Galerkin finite-element method. The submodel of mass transport of nitrogen incorporates the convection-dispersion processes of ammonium and nitrate nitrogen, nitrification, denitrification, ammonium exchange and uptake of ammonium and nitrate ions. The accuracy and validity of the proposed model was examined by comparison with an explicit-implicit finite-difference model results. The model was used for simulation of water and nitrogen dynamics during wastewater application in homogeneous and multi-layered soils under different N concentration, rate, duration and scheduling of application. 相似文献