全文获取类型
收费全文 | 5230篇 |
免费 | 193篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 86篇 |
综合类 | 30篇 |
化学工业 | 1510篇 |
金属工艺 | 96篇 |
机械仪表 | 96篇 |
建筑科学 | 324篇 |
矿业工程 | 23篇 |
能源动力 | 99篇 |
轻工业 | 414篇 |
水利工程 | 34篇 |
石油天然气 | 2篇 |
无线电 | 323篇 |
一般工业技术 | 1096篇 |
冶金工业 | 512篇 |
原子能技术 | 40篇 |
自动化技术 | 751篇 |
出版年
2023年 | 38篇 |
2022年 | 49篇 |
2021年 | 85篇 |
2020年 | 74篇 |
2019年 | 68篇 |
2018年 | 83篇 |
2017年 | 98篇 |
2016年 | 142篇 |
2015年 | 102篇 |
2014年 | 163篇 |
2013年 | 248篇 |
2012年 | 221篇 |
2011年 | 325篇 |
2010年 | 248篇 |
2009年 | 257篇 |
2008年 | 252篇 |
2007年 | 237篇 |
2006年 | 238篇 |
2005年 | 205篇 |
2004年 | 177篇 |
2003年 | 140篇 |
2002年 | 112篇 |
2001年 | 88篇 |
2000年 | 90篇 |
1999年 | 105篇 |
1998年 | 119篇 |
1997年 | 88篇 |
1996年 | 94篇 |
1995年 | 75篇 |
1994年 | 71篇 |
1993年 | 77篇 |
1992年 | 74篇 |
1991年 | 56篇 |
1990年 | 60篇 |
1989年 | 57篇 |
1988年 | 60篇 |
1987年 | 55篇 |
1986年 | 47篇 |
1985年 | 46篇 |
1984年 | 55篇 |
1983年 | 40篇 |
1982年 | 47篇 |
1981年 | 47篇 |
1980年 | 31篇 |
1979年 | 29篇 |
1978年 | 35篇 |
1977年 | 31篇 |
1976年 | 33篇 |
1975年 | 37篇 |
1973年 | 32篇 |
排序方式: 共有5436条查询结果,搜索用时 15 毫秒
101.
102.
Simulating deformable objects based on physical laws has become the most popular technique for modeling textiles, skin, or volumetric soft objects like human tissue. The physical model leads to an ordinary differential equation. Recently, several approaches to fast algorithms have been proposed.In this work, more profound numerical background about numerical stiffness is provided. Stiff equations impose stability restrictions on a numerical integrator. Some one-step and multistep methods with adequate stability properties are presented. For an efficient implementation, the inexact Newton method is discussed. Applications to 2D and 3D elasticity problems show that the discussed methods are faster and give higher-quality solutions than the commonly used linearized Euler method. 相似文献
103.
Tim Weitzel Daniel Beimborn Wolfgang König 《Information Systems and E-Business Management》2003,1(2):189-211
Networks utilizing modern communication technologies can offer competitive advantages to those using them wisely. But due
to the existence of network effects, planning and operating cooperation networks is difficult. In this paper, the strategic
situation of individual agents deciding on network participation is analysed. A systematic equilibrium analysis using computer-based
simulations reveals principal solution scenarios for network agents and shows that network cooperation problems might frequently
be not as difficult to resolve as often feared. In particular, strategic situations are identified showing that a majority
of individuals might be better off getting the optimal solution from a central principal and that in many cases simple information
intermediation can solve the start-up problem notorious in network economics. 相似文献
104.
Carl L. Gardner Wolfgang Nonner Robert S. Eisenberg 《Journal of Computational Electronics》2004,3(1):25-31
The drift-diffusion (Poisson-Nernst-Planck) model is applied to ionic channels in biological membranes plus surrounding solution baths. Simulations of the K channel in KCl solutions using the TRBDF2 method are presented which show significant boundary layers at the ends of the channel. The computed current-voltage curve for the K channel shows excellent agreement with experimental measurements. 相似文献
105.
Chaney John M.; Mullins Larry L.; Wagner Janelle L.; Hommel Kevin A.; Page Melanie C.; Doppler Matthew J. 《Canadian Metallurgical Quarterly》2004,49(2):126
Objective: Examine longitudinal relationships between causal attributions and depression symptoms in adults with rheumatoid arthritis (RA). Study Design: Cross-lagged panel correlations tested the temporal precedence of attributions relative to depression symptoms over 1 year. Participants: Forty-two participants completed self-report instruments on 2 occasions. Main Outcome Measures: The Inventory to Diagnose Depression and the Attributional Style Questionnaire. Results: Time 1 attributions predicted increased levels of depression symptoms at Time 2 after perceived pain and disability were controlled: Time 1 depression symptoms were unrelated to Time 2 attributions. Cross-lagged correlation comparisons revealed statistical dominance for attribution-depression relationships relative to depression-attribution relationships. Conclusions: Results support cognitive diathesis conceptualizations of depression and support cognitive-behavioral treatments for depression in RA. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
106.
A dichoptic masking procedure was used to test whether the mask-dependent cuing effects found in luminance detection by P. L. Smith (2000a) were due to integration masking or interruption masking. Attentional cuing enhanced detection sensitivity (d') when stimuli were backwardly masked with either dichoptic or monoptic masks, whereas no cuing effect was found with unmasked stimuli, implying the mask dependencies were due to interruption of stimulus processing in visual cortex by the mask. The effect is predicted by a gated diffusion process model in which masks interrupt stimulus processing and attention controls the flow of information to a sequential-sampling decision mechanism. The model correctly predicts different patterns of performance for detection and discrimination and cuing effects in simple reaction time. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
107.
The SlipReactionFoamSintering (SRFS)‐ process is a metallurgical method to produce open‐cell metallic foams of iron based materials, steels and nickel based materials. In this process several chemical reactions take place. Through the most influential parameter, the morphology of the metallic powder, different properties of the foam can be adjusted, such as the viscosity of the slip, the cell structure and the mechanical properties. Several examples are presented in this paper. Moreover, the thermal conductivity of three foams is measured with the transient‐heat‐source‐technique. 相似文献
108.
For ultra low carbon (ULC) and low carbon steel (LC), the influence of heating rate, annealing temperature, and holding time on the recrystallisation behaviour and the resulting grain size was investigated. For ULC smallest grain sizes of about 9 μm were obtained at the lowest heating rate whereas for LC significant smaller grain sizes of about 5 μm were determined at the highest heating rate. Furthermore, the evolution of the grain size distribution with varying heating rate, annealing temperature, and holding time was studied in dependence of the rolling and normal direction. The state of the as‐hot rolled microstructure as well as the precipitation state exert a strong influence on the development of the recrystallised microstructure along the different directions for both steel grades. The inherent prolonged microstructure due to the cold rolling process is still obvious just after recrystallisation. With ongoing annealing and grain growth, the aspect ratio approaches the equiaxed state. This change proceeds faster for the ULC steel grade. With increasing annealing temperature, the bimodal character of the grain size distribution disappears and the distribution becomes more homogeneous. 相似文献
109.
To maintain the original distribution pattern of diffusible elements in biological samples, electron probe microanalysis is carried out with frozen hydrated bulk specimens and cryosections, analysed at temperatures below 130 K. Ice has a very low intrinsic conductivity at this working temperature and surface- and space-charging appears, when uncoated specimens are irradiated with non-penetrating electrons. Although coating with a grounded conductor abolishes the surface potential, the build-up of an internal space-charge field is possible, depending on the sample thickness and beam voltage used. Consequently, the geometry of the X-ray source volume and the spectral distribution of the emitted continuous and characteristic X-rays are affected. To simulate the situation for microanalysis of frozen hydrated specimens the charging process in electron irradiated ice is studied by recording simultaneous specimen currents from the top and bottom of ice layer preparations. The external currents yield information on the build-up of internal space-charge fields which result from the balance of charge injection, storage, and transport. Irradiation of uncoated bulk specimens with a finely focused beam results in the build-up of a space-charge field close to the surface, which causes a reduction of the depth of microprobe analysis. In coated bulk specimens the induced conductivity renders possible a current flow to the front electrode, thereby limiting the space-charge field. Sections with an effective rear electrode will not charge appreciably if the electron range is larger than about half the section thickness. 相似文献
110.
Golovko DS Haschke T Wiechert W Bonaccurso E 《The Review of scientific instruments》2007,78(4):043705
We present here an experimental setup and suggest an extension to the long existing added-mass method for the calibration of the spring constant of atomic force microscope cantilevers. Instead of measuring the resonance frequency shift that results from attaching particles of known masses to the end of cantilevers, we load them with water microdrops generated by a commercial inkjet dispenser. Such a device is capable of generating drops, and thus masses, of extremely reproducible size. This makes it an ideal tool for calibration tasks. Moreover, the major advantage of water microdrops is that they allow for a nearly contactless calibration: no mechanical micromanipulation of particles on cantilevers is required, neither for their deposition nor for removal. After some seconds the water drop is completely evaporated, and no residues are left on the cantilever surface or tip. We present two variants: we vary the size of the drops and deposit them at the free end of the cantilever, or we keep the size of the drops constant and vary their position along the cantilever. For the second variant, we implemented also numerical simulations. Spring constants measured by this method are comparable to results obtained by the thermal noise method, as we demonstrate for six different cantilevers. 相似文献