全文获取类型
收费全文 | 1830篇 |
免费 | 108篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 22篇 |
综合类 | 4篇 |
化学工业 | 441篇 |
金属工艺 | 21篇 |
机械仪表 | 20篇 |
建筑科学 | 105篇 |
矿业工程 | 3篇 |
能源动力 | 78篇 |
轻工业 | 180篇 |
水利工程 | 11篇 |
石油天然气 | 3篇 |
无线电 | 186篇 |
一般工业技术 | 353篇 |
冶金工业 | 113篇 |
原子能技术 | 13篇 |
自动化技术 | 389篇 |
出版年
2024年 | 4篇 |
2023年 | 23篇 |
2022年 | 42篇 |
2021年 | 54篇 |
2020年 | 32篇 |
2019年 | 47篇 |
2018年 | 46篇 |
2017年 | 44篇 |
2016年 | 43篇 |
2015年 | 59篇 |
2014年 | 83篇 |
2013年 | 113篇 |
2012年 | 94篇 |
2011年 | 145篇 |
2010年 | 133篇 |
2009年 | 104篇 |
2008年 | 115篇 |
2007年 | 99篇 |
2006年 | 86篇 |
2005年 | 78篇 |
2004年 | 54篇 |
2003年 | 66篇 |
2002年 | 63篇 |
2001年 | 27篇 |
2000年 | 29篇 |
1999年 | 35篇 |
1998年 | 29篇 |
1997年 | 10篇 |
1996年 | 24篇 |
1995年 | 16篇 |
1994年 | 24篇 |
1993年 | 22篇 |
1992年 | 11篇 |
1991年 | 11篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1982年 | 5篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有1942条查询结果,搜索用时 0 毫秒
1.
C. B. Arends 《Polymer Engineering and Science》1992,32(13):841-844
Elastic moduli of injection molded blends of polycarbonate with poly(styrene-co-acrylonitrile) (SAN) have been obtained at temperatures between the glass transition temperatures of the two components. When compared with compression molded blends as a function of composition, the moduli were found to differ by as much as a factor of three at intermediate compositions. The variations are ascribed to differences in connectivity between minor component particles. The morphologies of these materials have been modeled using percolation concepts to quantify continuity of the individual phases. The effects of phase continuity resulting from composition as well as dispersed phase shape differences were evaluated. It was found that shape per se has only a minor effect on percolation. However, shape as reflected in the size of dispersed particles relative to the extent of the domain in which they reside is primary for developing a model for continuity of the phases. An empirical relation for percolation in finite domains was devised from Monte Carlo simulations. Modulus values calculated from these continuity considerations agree well with the observed data. 相似文献
2.
Johan M. Thevelein 《Yeast (Chichester, England)》1994,10(13):1753-1790
3.
Johan F. Hoorn 《Cognition, Technology & Work》2008,10(4):249-249
4.
Mathematically, skewed symmetry is a nonaccidental property because it can be interpreted as bilateral symmetry in depth viewed from a nonorthogonal angle. To find out whether this is a useful property in the perception of visual forms, 4 experiments were designed in which the Ss had to determine whether 2 symmetric or random patterns were the same regardless of possible affine transformations between them. The results provided mixed evidence: Although there was always a large symmetry advantage, skewed symmetry was only perceived as bilateral symmetry in depth for dot patterns with higher order types of symmetry (Exp 1), when the dots were connected to form closed polygons (Exp 2 and 4), or when they were surrounded by a frame to enhance their planarity (Exp 3). In other cases, Ss relied on local groupings on the basis of proximity or curvilinearity, which are qualitatively affine invariant. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
6.
We present algorithms, methods, and software for a Grid resource manager, that performs resource brokering and job scheduling in production Grids. This decentralized broker selects computational resources based on actual job requirements, job characteristics, and information provided by the resources, with the aim to minimize the total time to delivery for the individual application. The total time to delivery includes the time for program execution, batch queue waiting, and transfer of executable and input/output data to and from the resource. The main features of the resource broker include two alternative approaches to advance reservations, resource selection algorithms based on computer benchmark results and network performance predictions, and a basic adaptation facility. The broker is implemented as a built-in component of a job submission client for the NorduGrid/ARC middleware. 相似文献
7.
Logic and the Dynamics of Information 总被引:3,自引:0,他引:3
We discuss how issues of information and computation interact with logic today, and what might be a natural extended agenda of investigation. 相似文献
8.
Johan F. Prins 《Materials Research Innovations》1998,1(4):243-253
Two identical, high purity, natural type IIa diamonds, which displayed the ubiquitous blue cathodoluminescence (CL) band
at ≈ 2.9 eV, as well as an indication of the corresponding green band at ≈ 2.4 eV, have been equivalently doped by using extremely
low dose B+- and C+-ion CIRA-implantations respectively. Comparative CL measurements showed changes in the intensities of the 2.9 and 2.4 eV
bands and the generation of bands at ≈ 4 eV, as well as at ≈ 3.5 and ≈ 4.6 eV (the latter two in the B+-CIRA diamond). The results are commensurate with the model (proposed previously) in which the 2.9 and 4 eV bands are generated
respectively by electron-hole recombinations at negatively charged acceptor- and positively charged donor-like, intrinsic
defects. The present results indicate that Coulomb interactions between the latter defects and (at least partially) compensated,
negatively charged, boron acceptors, generate the 3.5 and 4.6 eV bands, which may be considered as higher energy (≈ 0.6 eV)
replicas of the 2.9 and 4 eV bands. In both cases, two electrons and a hole interact just before the hole combines with an
electron. Such a configuration of charges seems related to, and could possibly be described as, a type of ”ionised exciton
molecule”, where the ”bonding” of two negative ”nuclei” is facilitated by the presence of the hole. The CL measurements further
indicate that the 2.4 eV band forms when a high enough density of, in this case, neutral acceptors are present. These neutral
acceptors compete with the valence band to supply holes for recombination at the negatively charged, acceptor-type, intrinsic
defects which are, in the absence of the boron, responsible for the generation of the blue, 2.9 eV band.
Received: 5 December 1997 / Accepted: 13 December 1997 相似文献
9.
W-based versus latent variables spatial autoregressive models: evidence from Monte Carlo simulations
In this paper, we compare by means of Monte Carlo simulations two approaches to take spatial autocorrelation into account: the classical spatial autoregressive model and the structural equations model with latent variables. The former accounts for spatial dependence and spillover effects in georeferenced data by means of a spatial weights matrix W. The latter represents spatial dependence and spillover effects by means of a latent variable in the structural (regression) model while the observed spatially lagged variables are related to the latent spatial dependence variable in the measurement model. The simulation results based on Anselin’s Columbus, Ohio, crime data set show that the misspecified latent variables approach slightly trails the correctly specified classical approach in terms of bias and root mean squared error of the coefficient estimators. 相似文献