全文获取类型
收费全文 | 8896篇 |
免费 | 1170篇 |
国内免费 | 627篇 |
专业分类
电工技术 | 744篇 |
综合类 | 1435篇 |
化学工业 | 557篇 |
金属工艺 | 212篇 |
机械仪表 | 612篇 |
建筑科学 | 583篇 |
矿业工程 | 178篇 |
能源动力 | 191篇 |
轻工业 | 218篇 |
水利工程 | 207篇 |
石油天然气 | 153篇 |
武器工业 | 79篇 |
无线电 | 1084篇 |
一般工业技术 | 1405篇 |
冶金工业 | 283篇 |
原子能技术 | 62篇 |
自动化技术 | 2690篇 |
出版年
2024年 | 27篇 |
2023年 | 104篇 |
2022年 | 137篇 |
2021年 | 207篇 |
2020年 | 310篇 |
2019年 | 291篇 |
2018年 | 329篇 |
2017年 | 341篇 |
2016年 | 407篇 |
2015年 | 370篇 |
2014年 | 480篇 |
2013年 | 589篇 |
2012年 | 607篇 |
2011年 | 604篇 |
2010年 | 479篇 |
2009年 | 495篇 |
2008年 | 508篇 |
2007年 | 609篇 |
2006年 | 506篇 |
2005年 | 415篇 |
2004年 | 376篇 |
2003年 | 384篇 |
2002年 | 308篇 |
2001年 | 279篇 |
2000年 | 264篇 |
1999年 | 182篇 |
1998年 | 161篇 |
1997年 | 169篇 |
1996年 | 120篇 |
1995年 | 88篇 |
1994年 | 91篇 |
1993年 | 69篇 |
1992年 | 73篇 |
1991年 | 44篇 |
1990年 | 48篇 |
1989年 | 32篇 |
1988年 | 32篇 |
1987年 | 18篇 |
1986年 | 15篇 |
1985年 | 10篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 13篇 |
1981年 | 16篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1966年 | 5篇 |
1964年 | 13篇 |
1963年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Moshe Eisenberger 《International journal for numerical methods in engineering》2003,57(11):1603-1614
This work presents the derivation of the exact dynamic stiffness matrix for a high‐order beam element. The terms are found directly from the solutions of the differential equations that describe the deformations of the cross‐section according to the high‐order theory, which include cubic variation of the axial displacements over the cross‐section of the beam. The model has six degrees of freedom at the two ends, one transverse displacement and two rotations, and the end forces are a shear force and two end moments. Using the dynamic stiffness matrix exact vibration frequencies for beams with various combinations of boundary conditions are tabulated and compared with results from the Bernoulli–Euler and Timoshenko beam models. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
33.
双原子系统中原子非经典特性与光场非经典特性的关联 总被引:2,自引:0,他引:2
本文研究了双原子与双模光场相互作用系统中,双原子分崩离析有压缩与双模光场二阶压缩间的对称关系。揭示了原子间关系和光场模间关联的转换特性,并探讨了失谐量,耦和常数对原子非经典特性与光场非经典特性间关联的影响。 相似文献
34.
By incorporating digraph models, fault trees and fuzzy inference mechanisms in a unified framework, a novel approach for fault diagnosis is developed in this work. To relieve the on-line computation load, the fault origins considered in diagnosis are limited to the basic events in the cut sets of a given fault tree. The symptom occurrence order associated with each root cause is derived from system digraph with the qualitative simulation techniques. The implied candidate patterns are enumerated according to two proposed theorems and then encoded in the inference system with IF-THEN rules. The simulation results show that the proposed approach is not only feasible but also capable of identifying the most likely cause(s) of a hazardous event at the earliest possible time. 相似文献
35.
高水固结尾砂充填采矿充填体合理配比的研究 总被引:7,自引:4,他引:3
高水固结尾砂充填采矿是一种新型充填采矿法。试验测定了高水固结尾矿充填体的强度和变形特征;研究分析了影响充填体强度的主要因素、高水充填工艺的特殊要求,以及上向,下向进路开采对充填体强度和稳定性的要求,提出了满足支护强度,工艺及经济需求的充填材料的合理配比范围。 相似文献
36.
37.
Learning a sequence of target locations when the sequence is uncorrelated with a sequence of responses and target location is not the response dimension (pure perceptual-based sequence learning) was examined. Using probabilistic sequences of target locations, the author shows that such learning can be implicit, is unaffected by distance between target locations, and is mostly limited to first-order transition probabilities. Moreover, the mechanism underlying learning affords processing of information at anticipated target locations and appears to be attention based. Implications for hypotheses of implicit sequence learning are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
38.
用波前相因子判断法,将球面波照明物体的自由空间菲涅耳衍射光场分布与分数傅里叶逆变换的标准频谱分布进行位相比较,提供了广义条件下光学分数傅里叶逆变换的无透镜模式,给出其光学实现基本单元参量选择的判定法则,计算机模拟实验证明了结论的可靠与可行。 相似文献
39.
The aim of the present paper is to study the effect of gravity on visco-elastic surface waves in solids. The wave velocity
equations are deduced from Biot’s theory of initial stress on the assumption that gravity creates a type of initial stress
— hydrostatic in nature. Resulting equations are used to investigate surface waves of the Rayleigh, Love and Stoneley types.
Results are in good agreement with corresponding classical results when gravity and viscosity are neglected. 相似文献
40.
Jun‐Sik Kim Maenghyo Cho 《International journal for numerical methods in engineering》2002,55(11):1323-1343
A finite element based on the efficient higher‐order zig‐zag theory with multiple delaminations is developed. The bending part of the formulation is constructed from the concept of DKQ element. Unlike conventional elements, a developed element has its reference in the bottom surface which simplifies zig‐zag terms on formulation. Exact patch solutions are developed on elements which have the bottom reference system. The present element passes proper bending patch tests in the arbitrary mesh configurations in isotropic materials. Zig‐zag formulation is adopted to model laminated plates with multiple delaminations. To assess the accuracy and efficiency of the present element based on higher‐order zig‐zag theory with multiple delaminations, the linear buckling problem of laminated plates with multiple delaminations has been analysed. The results have been compared with three‐dimensional elasticity solutions. The present element works as an efficient tool for analysing the behaviour of the laminated composites with multiple delaminations. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献