全文获取类型
收费全文 | 972篇 |
免费 | 46篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 15篇 |
综合类 | 3篇 |
化学工业 | 143篇 |
金属工艺 | 20篇 |
机械仪表 | 36篇 |
建筑科学 | 16篇 |
矿业工程 | 1篇 |
能源动力 | 81篇 |
轻工业 | 69篇 |
水利工程 | 8篇 |
石油天然气 | 22篇 |
无线电 | 131篇 |
一般工业技术 | 215篇 |
冶金工业 | 83篇 |
原子能技术 | 6篇 |
自动化技术 | 173篇 |
出版年
2024年 | 2篇 |
2023年 | 9篇 |
2022年 | 17篇 |
2021年 | 43篇 |
2020年 | 35篇 |
2019年 | 48篇 |
2018年 | 39篇 |
2017年 | 52篇 |
2016年 | 40篇 |
2015年 | 28篇 |
2014年 | 52篇 |
2013年 | 77篇 |
2012年 | 44篇 |
2011年 | 57篇 |
2010年 | 50篇 |
2009年 | 42篇 |
2008年 | 26篇 |
2007年 | 28篇 |
2006年 | 29篇 |
2005年 | 25篇 |
2004年 | 15篇 |
2003年 | 17篇 |
2002年 | 11篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 12篇 |
1998年 | 29篇 |
1997年 | 20篇 |
1996年 | 17篇 |
1995年 | 24篇 |
1994年 | 11篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 17篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有1022条查询结果,搜索用时 156 毫秒
1.
2.
Charbel Farhat Ulrich Hetmaniuk 《International journal for numerical methods in engineering》2002,54(9):1309-1332
We present a fictitious domain decomposition method for the fast solution of high‐frequency acoustic scattering problems characterized by a partially axisymmetric sound‐soft scatterer. We apply this method to the solution of various mockup submarine problems, and highlight its computational advantages and intrinsic parallelism. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
3.
We present a fictitious domain decomposition method for the fast solution of acoustic scattering problems characterized by a partially axisymmetric sound‐hard scatterer. We apply this method to the solution of a mock‐up submarine problem, and highlight its computational advantages and intrinsic parallelism. A key component of our method is an original idea for addressing a Neumann boundary condition in the general framework of a fictitious domain method. This idea is applicable to many other linear partial differential equations besides the Helmholtz equation. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
4.
Laparoscopic surgery has gained much interest since its advent the late eighties. A 36-year-old patient underwent laparoscopic appendicectomy via the transumbilical route. She was rehospitalized three times thereafter for subumblical pain. At day +48, an abscess was evacuated at the point of the umbilical trocar insertion. This hour-glass shaped abscess had a preperitoneal and subcutaneous localization, blocked by the epiploic reaction. The infection this patient developed is an unusual clinical finding as pain was localized at a distance. The umbilical site and the preperitoneal subcutaneous nature of the abscess are also unusual. This case emphasizes the gravity of post-operative abscess of the abdominal wall and the necessity for adequate prophylaxy. 相似文献
5.
SF Ding JD Delhanty JS Dooley L Bowles CB Wood NA Habib 《Canadian Metallurgical Quarterly》1993,17(3):405-409
We have previously shown that the tumor suppressor gene for hepatocellular carcinoma (HCC) without cirrhosis may be located on chromosome 5q35-qter. In this study, we analyzed nine cases of primary HCC without cirrhosis using probes from the MCC and APC genes, which are in the region 5q21-22. None of the informative cases had allele loss detected by these probes, whereas the probe lambda MS8 for the region 5q35-qter showed allele loss in six out of six informative cases. The results confirm that the putative tumor suppressor gene for HCC without cirrhosis on chromosome 5q is distinct from the MCC and APC genes. 相似文献
6.
Charbel Farhat Michel Lesoinne 《International journal for numerical methods in engineering》1993,36(5):745-764
Most of the recently proposed computational methods for solving partial differential equations on multiprocessor architectures stem from the 'divide and conquer' paradigm and involve some form of domain decomposition. For those methods which also require grids of points or patches of elements, it is often necessary to explicitly partition the underlying mesh, especially when working with local memory parallel processors. In this paper, a family of cost-effective algorithms for the automatic partitioning of arbitrary two- and three-dimensional finite element and finite difference meshes is presented and discussed in view of a domain decomposed solution procedure and parallel processing. The influence of the algorithmic aspects of a solution method (implicit/explicit computations), and the architectural specifics of a multiprocessor (SIMD/MIMD, startup/transmission time), on the design of a mesh partitioning algorithm are discussed. The impact of the partitioning strategy on load balancing, operation count, operator conditioning, rate of convergence and processor mapping is also addressed. Finally, the proposed mesh decomposition algorithms are demonstrated with realistic examples of finite element, finite volume, and finite difference meshes associated with the parallel solution of solid and fluid mechanics problems on the iPSC/2 and iPSC/860 multiprocessors. 相似文献
7.
For environmental considerations, the substitution of the conventionally used oil-based grinding fluids has nowadays become strongly recommended. Although several alternatives have been proposed, cryogenic cooling by liquid nitrogen is the non-polluting coolant that has been given relatively more attention because of its very low temperature. In this investigation, in order to contribute to developing this promising cooling mode, its beneficial effects on the ground surface integrity of the AISI 304 stainless steel and their consequences on the fatigue lifetime are explored. Results of this investigation show that grinding under cryogenic cooling mode generates surfaces with lower roughness, less defects, higher work hardening and less tensile residual stresses than those obtained on surfaces ground under oil-based grinding fluid. These surface enhancements result into substantial improvements in the fatigue behaviour of components ground under this cooling mode. An increasing rate of almost 15% of the endurance limit at 2 × 106 cycles could be realized. SEM analyses of the fatigue fracture surfaces have shown that the fatigue cracks observed on the specimens ground under cryogenic cooling are shorter (i.e., 30-50 μm) than those generated under oil-based cooling mode (i.e., 150-200 μm). The realized improvements in the surface integrity and in the fatigue behaviour are thought to be related to the reduction of the grinding zone temperature observed under cryogenic cooling, as no significant differences between the grinding force components for both cooling modes have been observed. 相似文献
8.
Erosion is one of the most serious problems in various gas and liquid flow passages such as flow in pipes, pumps, turbines, compressors and many other devices. Sand presence causes loss of pipe wall thickness that can lead to pipe erosion, frequent failures and loss of expensive production time. The importance of this problem is mainly due to many related engineering applications, viz. heat exchangers. In order to reduce the frequency of such pipe erosions, caps in the form of replaceable pipes are protruded in the sudden contraction regions which are exposed to most of the serious erosion rates. In the present work, numerical investigation of the erosion of a pipe protruded in a sudden contraction is presented. The turbulent, steady, 2-D axi-symmetric flow inside an axi-symmetric abrupt contraction pipe with a pipe protrusion embedded in it was solved by steady-state time averaged conservation equations of mass and momentum along with two equation model for turbulence. Particles are tracked using Lagrangian particle tracking. An erosion model was employed to investigate the erosion phenomena for the given geometry. The influence of the different parameters such as the inlet flow velocity (3–10 m/s), the particle diameter (10–400 μm), the protruded pipe geometry (thickness T=1–5 mm and depth H=2–5 mm) and the pipe contraction ratio (Cr=0.25–0.5) on the erosion of pipe protrusion was investigated. Correlations for the influence of inlet flow velocity, depth and thickness of the protruded pipe on the erosion rate are presented. 相似文献
9.
The wood carbonization in Tunisia consists essentially of traditional activity using charcoaling stacks and pits characterized by high atmospheric pollution and poor energy conversion. Indeed, 70% of the initial mass of anhydrous wood are found in the vapor as aerosols, polluting and toxic gases and complex condensable organic compounds that can cause a substantial pollution of air, ground and water. Several processes of treatment and energy valorization of such effluents were proposed, but the incineration remains at present the most promising technique of depollution. The results show that the incineration, at about 1000°C, of wood carbonization smokes allows the destruction of 99% of the mass of pollutants except CO2 and the reduction of polluting gas emission. The possible valorization of the smoke’s energy in the exit of the incinerator enhances the thermal efficiency of the process. 相似文献
10.
Farhat N.H. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1989,77(5):670-681
Radar targets can be identified by either forming images with sufficient resolution to be recognized by the human observer or by forming signatures or representations of the target for automated machine recognition. Tomographic microwave diversity imaging techniques that combine angular (aspect), spectral, and polarization degrees of freedom have been shown, as summarized in the first part of this paper, to be capable of producing images of the scattering centers of a target with near optical resolution. In the second part of the paper the author shows that collective nonlinear signal processing based on models of neural networks combined with the use of suitable target signatures (here sinogram representations) offer the promise of robust super-resolved target identification from partial information. Results presented are of numerical simulations for a neuromorphic processor where the neural net performs simultaneously the functions of data storage, processing, and recognition by automatically generating an identifying object label, and fast optoelectronic architectures and hardware implementations are briefly mentioned. Practical considerations and extensions to real systems are briefly discussed 相似文献