全文获取类型
收费全文 | 9540篇 |
免费 | 824篇 |
国内免费 | 661篇 |
专业分类
电工技术 | 387篇 |
技术理论 | 3篇 |
综合类 | 1460篇 |
化学工业 | 706篇 |
金属工艺 | 613篇 |
机械仪表 | 581篇 |
建筑科学 | 1072篇 |
矿业工程 | 952篇 |
能源动力 | 397篇 |
轻工业 | 228篇 |
水利工程 | 470篇 |
石油天然气 | 524篇 |
武器工业 | 278篇 |
无线电 | 360篇 |
一般工业技术 | 1224篇 |
冶金工业 | 569篇 |
原子能技术 | 78篇 |
自动化技术 | 1123篇 |
出版年
2024年 | 31篇 |
2023年 | 107篇 |
2022年 | 255篇 |
2021年 | 308篇 |
2020年 | 337篇 |
2019年 | 274篇 |
2018年 | 240篇 |
2017年 | 283篇 |
2016年 | 322篇 |
2015年 | 345篇 |
2014年 | 547篇 |
2013年 | 626篇 |
2012年 | 657篇 |
2011年 | 678篇 |
2010年 | 532篇 |
2009年 | 618篇 |
2008年 | 535篇 |
2007年 | 592篇 |
2006年 | 560篇 |
2005年 | 494篇 |
2004年 | 430篇 |
2003年 | 364篇 |
2002年 | 299篇 |
2001年 | 223篇 |
2000年 | 230篇 |
1999年 | 197篇 |
1998年 | 158篇 |
1997年 | 136篇 |
1996年 | 118篇 |
1995年 | 114篇 |
1994年 | 86篇 |
1993年 | 55篇 |
1992年 | 47篇 |
1991年 | 39篇 |
1990年 | 38篇 |
1989年 | 29篇 |
1988年 | 31篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 4篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1979年 | 3篇 |
1977年 | 4篇 |
1974年 | 2篇 |
1966年 | 4篇 |
1963年 | 3篇 |
1960年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
中厚板轧制边部不均匀变形机理的探讨 总被引:1,自引:0,他引:1
通过分析宽中厚板轧制过程中的边部不均匀变形,探讨了其影响因素及大宽度板“切边纵裂”的产生原因,提出了解决问题的具体办法。 相似文献
2.
The objective of this paper is to prove that the Clausius inequality must be re-stated to have general applicability for heat transfer involving radiative fluxes. The integrand (đQ/T) of the Clausius expression applies to heat conduction and convection, but does not hold for most radiative transfer scenarios, with the exception of reversible infinitesimal net blackbody radiation transfer. In other cases involving radiative transfer, the equality holds for a cycle even though irreversible heat addition by radiative transfer occurs. This is without the erroneous presumption of entropy destruction anywhere in the cycle. Thus, the Clausius inequality indicates reversibility for a cycle that includes an irreversible process. Further, in some radiative cases the quantity đQ/T, where T is the boundary temperature, is not the entropy transfer at the system boundary, and in fact, primarily represents entropy production within the system. It is also clear that in another case considered, the quantity đQ/T had no physical meaning whatsoever. Consequently, the Clausius expression has been re-stated so that it is applicable to cycles with processes involving any form of heat transfer. A new integrand (đQcc/T + đSNet,Rad) is presented, allowing the Clausius inequality to generally apply to all heat transfer scenarios. The work in this paper emphasizes the need to re-state other fundamental equations allowing applicability to all heat transfer processes, and draws attention to the unique character of radiative entropy calculations. 相似文献
3.
In this paper we present some preliminary results about the coupling of shallow water equations for free surface flows and Darcy equation for groundwater flows. A suitable set of interface conditions is discussed: the Beavers and Joseph formula for the bottom stress is used. An iterative algorithm to solve the coupled problem is proposed and some numerical results are presented. 相似文献
4.
The mechanism of “475°C embrittlement” of a duplex stainless steel was investigated using finite element modelling of the stress distribution at brittle fracture initiation. Brittle fracture initiated at a critical shear stress, which increased with ferrite hardness. The fracture stress was affected by the duplex microstructure. Fracture was nucleated by deformation twins, which were identified using electron back-scatter diffraction. The ductile-to-brittle fracture transition was sensitive to age-hardening and could be described simply by the effect of age-hardening and test temperature on the yield stress. 相似文献
5.
企业办社会虽与市场经济的客观要求相悖,但石油企业大量办社会的事实仍揭示了所具备的理性面。认为国家作为不受所有者监督的代理者对石油企业的要求,石油企业的行业特性以及在传统体制下长期运作所成的定热是石油企业办社会的主要原因。 相似文献
6.
Dr Joseph A. Cannataci 《AI & Society》1989,3(3):169-183
This paper examines some of the possible legal implications of the production, marketing and use of expert systems. The relevance of a legally useful definition of expert systems, comprising systems designed for use both by laymen and professionals, is related to the distinctions inherent in the legal doctrine underlying provision of goods and provision of services. The liability of the sellers and users of, and contributors to, expert systems are examined in terms of professional malpractice as well as product liability. A recurring theme indicates that legislators may be inclined to restrict possibilities of liability suits in order to avoid disincentives to the creation of expert systems. 相似文献
7.
8.
9.
The purpose of this paper is the modelling of the mechanical behaviour of an elastomeric material, through detailed experimental and numerical procedures, specific to large strains. The experimental technique is based on in-plane kinematics measurements using a speckle extensometer, from which the whole two-dimensional field of in-plane displacements is obtained by a digital image processing [Polymer (2002)]. This part of the work concerns the identification of the constitutive equation for a carbon black natural rubber (NR) vulcanizate. We start by quoting some theoretical considerations relative to rubber elasticity and stress-softening effect, which is the counterpart of the filler reinforcement. Then, we describe the experimental procedure and present data for both non-preconditioned and preconditioned samples. Next, the identification of the constitutive law parameters using a minimization algorithm is driven. Finally, we present the validation of the constitutive model, by its implementation into the finite element code SYSTUS and the numerical simulation of the response of a double edge notched tensile (DENT) specimen. 相似文献
10.
Zhang Sheng-ming Yangtze River Scientific Research Institute Wuhan Hubei P. R. China 《水动力学研究与进展(B辑)》1992,(2)
Through a series of model tests of five scales for 2-D free hydraulic jump, the da-ta of fluctuating pressure acting on the floor level within the hydraulic jump were obtained. Dur-ing the experiments, Froude number varied from 2.94 to 8.61, and Reynolds number rangedfrom 2×10~4 to 6×10~5. Experiment results indicate that the amplitude scale of fluctuating pres-sure is the length scale of model, i. e. P'=L, which agrees with gravity similarity law: Thefrequency scale of the fluctuating pressure is a unity i. e., f=1, which does not satisfy thegravity similarity law. 相似文献