全文获取类型
收费全文 | 645721篇 |
免费 | 9292篇 |
国内免费 | 1931篇 |
专业分类
电工技术 | 12147篇 |
综合类 | 886篇 |
化学工业 | 98119篇 |
金属工艺 | 22233篇 |
机械仪表 | 18550篇 |
建筑科学 | 17501篇 |
矿业工程 | 1587篇 |
能源动力 | 17658篇 |
轻工业 | 64577篇 |
水利工程 | 5174篇 |
石油天然气 | 5178篇 |
武器工业 | 21篇 |
无线电 | 82730篇 |
一般工业技术 | 119771篇 |
冶金工业 | 121499篇 |
原子能技术 | 9541篇 |
自动化技术 | 59772篇 |
出版年
2021年 | 4700篇 |
2019年 | 4346篇 |
2018年 | 6970篇 |
2017年 | 6920篇 |
2016年 | 7302篇 |
2015年 | 5727篇 |
2014年 | 9449篇 |
2013年 | 30547篇 |
2012年 | 16086篇 |
2011年 | 22742篇 |
2010年 | 17599篇 |
2009年 | 19941篇 |
2008年 | 21198篇 |
2007年 | 21218篇 |
2006年 | 18968篇 |
2005年 | 17540篇 |
2004年 | 17089篇 |
2003年 | 16650篇 |
2002年 | 16104篇 |
2001年 | 16215篇 |
2000年 | 15252篇 |
1999年 | 16182篇 |
1998年 | 37641篇 |
1997年 | 27314篇 |
1996年 | 21480篇 |
1995年 | 16690篇 |
1994年 | 15045篇 |
1993年 | 14425篇 |
1992年 | 10765篇 |
1991年 | 10337篇 |
1990年 | 9874篇 |
1989年 | 9529篇 |
1988年 | 9166篇 |
1987年 | 7696篇 |
1986年 | 7782篇 |
1985年 | 9316篇 |
1984年 | 8589篇 |
1983年 | 7740篇 |
1982年 | 7153篇 |
1981年 | 7215篇 |
1980年 | 6780篇 |
1979年 | 6537篇 |
1978年 | 6109篇 |
1977年 | 7444篇 |
1976年 | 9949篇 |
1975年 | 5240篇 |
1974年 | 5015篇 |
1973年 | 4936篇 |
1972年 | 3981篇 |
1971年 | 3493篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The strengths of two graphite/epoxy notched laminate systems with a softening strip were investigated. The softening strip was created by replacing the 0°-graphite/epoxy plies by a glass/epoxy composite. Experimental results indicated that the use of softening strips could significantly increase the laminate strength. Analysis was performed with finite elements developed using the classical laminated plate theory and was shown to be adequate. A simple point-stress failure criterion was used to predict the strength of notched laminates with softening strips and the result was found to be satisfactory. 相似文献
992.
993.
The IBM RISC System/6000, a superscalar microprocessor, is presented. The architecture of this processor has its instruction set specifically designed for a superscalar machine containing three independent units-branch, fixed-point, and floating-point. The design also emphasizes high-performance floating-point operations. The design principles are to offer maximum overlap of the three functional units, avoid dead cycles, and define instructions that can (for the most part) be completed at a rate of one per cycle. The branch cycle, fixed- and floating-point units, cache management, and performance are described. Benchmark results are given 相似文献
994.
For pt.I. see ibid., vol.8, no.3, p.36-43 (1991). Contactless tools for testing inside dynamic RAMs, including hot-spot detection, emission microscopy, scanning laser microscopy, and submicron electron beam testing, are described. Basic principles and experimental setups are described. The utility of the techniques is assessed 相似文献
995.
Shape representation by multiscale contour approximation 总被引:3,自引:0,他引:3
996.
997.
Pull-out experiments have been carried out on single production fibres under carefully controlled conditions. Four parameters were determined. The interfacial yield stresses, of about 9–14 MPa, were very much smaller than the shear strengths of the bulk polymers in the case of an epoxy, whether post-cured or not, and a non-post-cured polyester. Values for the work of fracture of the interface varied from 140 to 300 Jm?2, and again were less than those of the polymer. Interface failure sometimes took place in the epoxy rather than at the fibre surface, whereas with the polyester it always took place at the fibre surface. After interface failure, pull-out was governed by friction, with maximum shear stresses of 7–10 MPa for polyester, and 21–34 MPa for epoxy, the higher values being obtained for the post-cured resins. Average frictional shear stresses were sometimes less than a half of the maximum shear stress, indicating that the fibre Poisson's shrinkage was playing an important role in the pull-out process. A silicone release agent reduced the frictional shear stresses to 2·5 MPa, with both resins. 相似文献
998.
A. J. Hermans 《Journal of Engineering Mathematics》1991,25(1):63-75
The purpose of this paper is to provide a mathematical tool to improve the optimal design of ship forms. It is common practice that hull forms are designed such that they have minimum wave resistance in calm water. In this paper a theory is described by which the effect of short waves may be incorporated.The basic tool we use is the ray theory. First, the appropriate free-surface condition is shown. Then, the standard ray method, well-known in geometric optics, is formulated in the fluid region and at the free surface. After an elimination process the eiconal equation and the transport equation are obtained. The characteristic equation for the nonlinear eiconal equation is derived, keeping in mind that the characteristics are not perpendicular to the wave fronts, due to the effect of the double-body potential due to the forward speed of the ship, which is assumed to be a good approximation for the steady potential.Numerical computations are carried out by means of the RK4 method to obtain the ray pattern. After some manipulations the amplitude may be computed just as well. Finally, the nonlinear added-resistance force is calculated. Pictures of ray patterns for several angles of incidence are shown. Also the forces are shown. 相似文献
999.
Canham R.O. Smith S.L. Tyrrell A.M. 《Vision, Image and Signal Processing, IEE Proceedings -》2005,152(6):741-749
Complex and highly distorted line drawings are produced by subjects attempting the Rey Complex Figure test, a clinical test of neuropsychological assessment. However, the marking scheme conventionally employed can be subjective and unreliable. In this paper, the first stages in automating this scoring system are investigated using a robust technique to locate a reduced set of scoring sections and a knowledge-based system that employs spatial metrics and fuzzy approximation techniques. Testing the technique using clinical data produced encouraging results that support the argument that this is a feasible approach for implementing a fully automated system, and that in its current state, can be immediately applied in a semi-automated system. 相似文献
1000.
Fernando J Beltrn F Javier Rivas Olga Gimeno 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(9):973-984
Photocatalytic ozonation (1O3 + VUV + TiO2), ozonation (O3), catalytic ozonation (O3 + TiO2), ozone photolysis (O3 + VUV), photocatalysis (TiO2 + VUV) and photolysis (VUV) have been compared in terms of formation of intermediates, extent of, mineralization (TOC, COD, chloride, nitrate) and kinetics in the aqueous treatment of three phenols (phenol, p‐chlorophenol and p‐nitrophenol). In all cases, photocatalytic ozonation led to lower degradation times for chemical oxygen demand and total organic carbon removal. Intermediates formed were similar in the different oxidation systems with some exceptions. They can be classified into three different types: polyphenols (resorcinol, catechol, hydroquinone), unsaturated carboxylic acids (maleic and fumaric acids) and saturated carboxylic acids (glyoxylic, formic and oxalic acids). First order kinetic equations have been checked for the oxidation processes studied in the case of the parent compound. Rate constants of these systems have also been calculated. Copyright © 2005 Society of Chemical Industry 相似文献