全文获取类型
收费全文 | 11857篇 |
免费 | 1250篇 |
国内免费 | 362篇 |
专业分类
电工技术 | 196篇 |
技术理论 | 1篇 |
综合类 | 902篇 |
化学工业 | 1198篇 |
金属工艺 | 353篇 |
机械仪表 | 325篇 |
建筑科学 | 2486篇 |
矿业工程 | 147篇 |
能源动力 | 298篇 |
轻工业 | 115篇 |
水利工程 | 1678篇 |
石油天然气 | 181篇 |
武器工业 | 27篇 |
无线电 | 985篇 |
一般工业技术 | 2631篇 |
冶金工业 | 666篇 |
原子能技术 | 33篇 |
自动化技术 | 1247篇 |
出版年
2024年 | 47篇 |
2023年 | 378篇 |
2022年 | 204篇 |
2021年 | 321篇 |
2020年 | 364篇 |
2019年 | 359篇 |
2018年 | 350篇 |
2017年 | 341篇 |
2016年 | 483篇 |
2015年 | 521篇 |
2014年 | 704篇 |
2013年 | 751篇 |
2012年 | 781篇 |
2011年 | 919篇 |
2010年 | 625篇 |
2009年 | 678篇 |
2008年 | 600篇 |
2007年 | 630篇 |
2006年 | 624篇 |
2005年 | 563篇 |
2004年 | 504篇 |
2003年 | 400篇 |
2002年 | 374篇 |
2001年 | 255篇 |
2000年 | 217篇 |
1999年 | 203篇 |
1998年 | 196篇 |
1997年 | 149篇 |
1996年 | 138篇 |
1995年 | 115篇 |
1994年 | 109篇 |
1993年 | 77篇 |
1992年 | 84篇 |
1991年 | 48篇 |
1990年 | 61篇 |
1989年 | 40篇 |
1988年 | 29篇 |
1987年 | 25篇 |
1986年 | 15篇 |
1985年 | 31篇 |
1984年 | 24篇 |
1983年 | 29篇 |
1982年 | 20篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1975年 | 6篇 |
1974年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
反转构造的反转程度及其与油气聚集的关系 总被引:10,自引:2,他引:8
结合典型反转构造地震剖面,分析了断层型和褶皱型两类反转构造的反转程度,上下皆正断层型和向形褶皱型反转构造的反转程度轻微;上逆下正断层型和透镜形褶皱型反转构造的反转程度中等;上下皆逆断层型和背形褶皱型反转构造的反转程度强烈。分析了反转构造的反转程度与油气聚集的关系,处于轻微反转程度的上下皆正断层型反转和向形褶皱型反转,以及处于强烈反转程度的上下皆逆断层型反转和背形褶皱型反转不利于油气聚集;处于中等反转程度的上逆下正断层型反转和透镜形褶皱型反转类型有利于油气聚集成藏。 相似文献
12.
In this paper, the moving least-squares differential quadrature (MLSDQ) method is employed for free vibration of thick antisymmetric laminates based on the first-order shear deformation theory. The generalized displacements of the laminates are independently approximated with the centered moving least-squares (MLS) technique within each domain of influence. The MLS nodal shape functions and their partial derivatives are computed quickly through back-substitutions after only one LU decomposition. Subsequently, the weighting coefficients in the MLSDQ discretization are determined with the nodal partial derivatives of the MLS shape functions. The MLSDQ method combines the merits of both the differential quadrature and meshless methods which can be conveniently applied to complex domains and irregular discretizations without loss of implementation efficiency and numerical accuracy. The natural frequencies of the laminates with various edge conditions, ply angles, and shapes are calculated and compared with the existing solutions to study the numerical accuracy and stability of the MLSDQ method. Effects of support size, order of completeness of basis functions, and node irregularity on the numerical accuracy are investigated in detail. 相似文献
13.
Finite element piezothermoelasticity analysis and the active control of FGM plates with integrated piezoelectric sensors and actuators 总被引:3,自引:0,他引:3
An efficient finite element model is presented for the static and dynamic piezothermoelastic analysis and control of FGM
plates under temperature gradient environments using integrated piezoelectric sensor/actuator layers. The properties of an FGM plate are functionally graded in the thickness
direction according to a volume fraction power law distribution. A constant displacement-cum-velocity feedback control algorithm that couples the direct and inverse piezoelectric effects is applied to provide active feedback
control of the integrated FGM plate in a closed loop system. Numerical results for the static and dynamic control are presented
for the FGM plate, which consists of zirconia and aluminum. The effects of the constituent volume fractions and the influence
of feedback control gain on the static and dynamic responses of the FGM plates are examined.
Received: 13 March 2002 / Accepted: 5 March 2003
The work described in this paper was supported by a grant awarded by the Research Grants Council of the Hong Kong Special
Administrative Region, China (Project No. CityU 1024/01E). 相似文献
14.
黄河流域委属大河控制站站网布局分析检验与调整 总被引:4,自引:0,他引:4
简要论述了黄河流域委属大河控制站的基本情况,通过资料分析,按“直线原则”计算了黄河大河控制站布站数目的上、下限,并调查分析落实了各河段近期和中长期治理开发对水资料的需求,确定各河段测站数目的采用值;对照现有站数,结合测站位置,功能,测验,生活条件等,逐段逐站进行审查,综合评估,决定测站的撤,迁,留,并对密度不足的河段提出了设站意见。 相似文献
15.
南水北调西线工程水环境影响分析 总被引:8,自引:0,他引:8
南水北调西线工程调水后,引水坝址下游局部河段水量明显减少,但影响范围和程度十分有限。随着两岸环保力度的加大,排污量的减少,径流量减少对局部江段水质的不利影响,可得到控制。预估调水后下游水质不会发生类别变化。 相似文献
16.
17.
Dongchang Sun Liyong Tong 《International journal for numerical methods in engineering》2004,60(11):1911-1932
A novel finite element model is presented for static and dynamic analysis of composite plates integrated with a laminated piezoelectric layer, a host laminated composite plate and an adhesive layer between them. A new adhesive element is developed which includes both peel and shear effects in the adhesive layer based on first‐order shear deformation plate theory. The thin adhesive layer between the piezoelectric layer and the host plate is modelled by assuming that it carries constant shear and peel strains throughout its thickness. In addition, a weighted static shape control scheme for finding the optimal voltage distribution for static shape control is given. By selecting different weighting matrices, a variety of items such as displacements, slopes, curvatures, strains and even generalized forces, can be included in finding the optimal actuating voltage for static shape control. The present model is validated by comparing with those results available in the literature. The numerical results show that the weighted linear least method can give a satisfactory voltage distribution to best match the desired shape. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
18.
Friendship affects individual and organizational well-being through direct relations, social positions, and complex network structures. In this study, the authors use longitudinal data from 2 groups of master's of business administration students to increase understanding of how friendship networks develop. The authors propose and test a dynamic model in which attribute similarity facilitates dyadic friendship ties, as well as similar network centrality and social position; early friendship increases later similarity in structural position and centrality; and early structural similarity enhances the likelihood of future friendship. Findings largely supported the model, demonstrating how homophily and early social contacts can jointly shape maturing friendship networks. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
19.
20.
Stretching dominated Kagome lattices reinforced by carbon fibers were designed and manufactured. The sandwich panels were assembled with bonded laminate skins. The mechanical behaviors of the sandwich panels were tested by out-of-plane compression, in-plane compression and three-point bending. Different failure modes of the sandwich structures were revealed. The experimental results showed that the carbon fiber reinforced lattice grids are much stiffer and stronger than foams and honeycombs. It was found that buckling and debonding dominate the mechanical behavior of the sandwich structures, and that more complaint skin sheets might further improve the overall mechanical performance of the sandwich panels. 相似文献