全文获取类型
收费全文 | 765篇 |
免费 | 22篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 41篇 |
化学工业 | 100篇 |
金属工艺 | 8篇 |
机械仪表 | 18篇 |
建筑科学 | 7篇 |
能源动力 | 29篇 |
轻工业 | 34篇 |
水利工程 | 2篇 |
无线电 | 134篇 |
一般工业技术 | 114篇 |
冶金工业 | 98篇 |
原子能技术 | 15篇 |
自动化技术 | 189篇 |
出版年
2023年 | 4篇 |
2022年 | 18篇 |
2021年 | 13篇 |
2020年 | 13篇 |
2019年 | 14篇 |
2018年 | 21篇 |
2017年 | 14篇 |
2016年 | 17篇 |
2015年 | 10篇 |
2014年 | 12篇 |
2013年 | 37篇 |
2012年 | 31篇 |
2011年 | 30篇 |
2010年 | 24篇 |
2009年 | 20篇 |
2008年 | 26篇 |
2007年 | 23篇 |
2006年 | 15篇 |
2005年 | 13篇 |
2004年 | 18篇 |
2003年 | 12篇 |
2002年 | 15篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 20篇 |
1998年 | 37篇 |
1997年 | 40篇 |
1996年 | 14篇 |
1995年 | 11篇 |
1994年 | 14篇 |
1993年 | 13篇 |
1992年 | 8篇 |
1991年 | 15篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 18篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 23篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 19篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1973年 | 5篇 |
1971年 | 4篇 |
排序方式: 共有789条查询结果,搜索用时 156 毫秒
61.
S. K. Aggarwal 《International Journal of Pressure Vessels and Piping》1980,8(6):419-449
Finite element stress analyses are presented which allow for elastic and elasto-plastic material behaviour for axisymmetric problems of pressure vessels using isoparametric quadrilateral elements with linear, parabolic and cubic displacements. The traditional method of analysis and design of cylindrical pressure vessels with reversed dished ends is based on the well known British Standard BS 5500 Code.1 The stresses and displacements, especially at and near the junctions, are of great interest to designers. In view of the immense usefulness of such containers, a detailed post yield study has been made based on the stress-strain idealisation for isotropic strain hardening materials—H′= 0·0047E and Von Mises and Tresca yield criteria. The basis for the prediction of load increment sizes for the elasto-plastic analysis and the upper bound for collapse pressure are presented, as well as the excessive deformation and shakedown criteria suitable for the design of reversed dished end containers. 相似文献
62.
The problem of early failure modelling has been discussed comprehensively. Present models have been discussed and new models are suggested. A drawback of failure rate not being finite at t = 0 for some of the present models is eliminated in the suggested models. 相似文献
63.
The method evaluates the reliability of large computer communication systems by systematic decomposition of the probabilistic graph of the system into two parts using an appropriate cutset. A technique is evolved for determining the conditional success events using both the node removal and connection multiplication methods for path enumeration. An example is solved to show the versatility of the method. The results of the example are verified by using an existing algorithm. The suggested method is general and computationally economical. 相似文献
64.
A general and simple technique for the evaluation of symbolic reliability expression in the case of practical systems such as a communication system having fixed channel capacities of its various communicating links, a computer communication network allowing a fixed amount of data exchange amongst different terminals of various computer centres and a power distribution system having limited power ratings of its various power lines, is presented. A system is considered reliable only if it successfully transmits at least the required system capacity from the transmitter to the receiver station. In this method, the various branch sets are obtained which completely disrupt the communication path, i.e. ensure system failure. It is observed that these branch sets are not necessarily the cutsets in the usual graph theoretic sense. The unreliability expression is then determined by adopting an existing method for making various terms disjoint. Two typical examples are solved by this method. It is observed that the method is computationally fast and efficient. 相似文献
65.
66.
A method for recovering the three-dimensional structure of moving rigid and jointed objects from several single camera views is presented. The method is based on the fixed axis assumption: all movement consists of translations and rotations about an axis that is fixed in direction for short periods of time. This assumption makes it possible to recover the structure of any group of two or more rigidly connected points. The structure of jointed objects is recovered by analyzing them as collections of rigid parts, and then unifying the structures proposed for the parts. The method presented here has been tested on several sets of data, including movies used to demonstrate human perception of structure from motion. 相似文献
67.
Highly Sensitive Pulsed Digital Holography for Built-in Defect Analysis with a Laser Excitation 总被引:7,自引:0,他引:7
A highly sensitive method is presented for noninvasive defect analysis on thin structures with a Q-switched double-pulsed ruby laser with frequency doubling (347 nm). In our research we feature an all-optical arrangement, where a focused laser pulse derived from the same ruby laser (694 nm) acts as a built-in synchronous excitation source for digital holographic interferometry. The recordings are made with a CCD camera for capturing two holograms (two states of the specimen) corresponding to the two UV laser pulses with a short time separation (10-50 mus). Subtraction of the phase distribution in two digital holograms gives a fringe phase map that shows the change in deformation of the specimen between the recordings. The advantage of the proposed method is two fold. First, the use of a shorter wavelength results in a higher sensitivity. Second, owing to the induced synchronous built-in optical excitation, the specimen is not subjected to any external physical excitation devices. Experimental results are presented on identification and evaluation of defects in thin metal sheets. 相似文献
68.
Mesocarbon microbeads are now-a-days used as a prominent self-sintering precursor for the production of high density monolithic graphite. The quality of this graphite is highly dependent on the characteristics of these microbeads, such as the quinoline and toluene insoluble contents, -resins content and volatile matter content, which in turn, can be controlled to desired values by suitable treatments of their extraction and calcination. In the present paper, the authors give an account of the study conducted to see the effect of calcination conditions of mesocarbon microbeads on the characteristics of the resulting graphite. A calcination at a temperature in the range of 280–320 °C for 30 min. under an ambient pressure of nitrogen, or at a temperature of 245–310 °C for 10 min. under a reduced pressure (5 cm Hg) of nitrogen, results in mesocarbon microbeads having a quinoline insoluble content of 83.6–89.8%, toluene insoluble content of 94.4–99.7%, -resins content of 6.8–11.9% and a volatile matter content of 10.2–13.5%. Such microbeads have been found to lead to a monolithic graphite possessing a bulk density 1.91–2.02 g cm–3, bending strength of 62–70 MPa, Shore hardness of 58–69, electrical resistivity of 2.1–2.6 m cm and a degree of anisotropy of 1.02–1.05. 相似文献
69.
70.
James R. Currie Ashok K. Batra Mohammad A. Alim Manmohan D. Aggarwal Ravindra B. Lal 《Journal of Materials Science: Materials in Electronics》2007,18(4):433-439
Polycrystalline SnO2 samples prepared in the laboratory were irradiated with 2 MeV He ions having doses of 3.62 × 1015 ion/cm2. The ac small-signal electrical data acquired for the polycrystalline SnO2 in the frequency (f) range 100 Hz ≤ f ≤ 1 MHz and temperature (T) range 26°C ≤ T ≤ 100°C revealed one semicircular relaxation in the impedance plane for the He implanted sample. However, two semicircular
relaxations were obtained in the same plane for the samples without He implantation. The He implantation indicated enhancement
in the donor density in the polycrystalline SnO2 as depicted via terminal conductance (or resistance).
An erratum to this article can be found at 相似文献