全文获取类型
收费全文 | 233148篇 |
免费 | 74804篇 |
国内免费 | 50512篇 |
专业分类
电工技术 | 33314篇 |
技术理论 | 1篇 |
综合类 | 26643篇 |
化学工业 | 28937篇 |
金属工艺 | 28019篇 |
机械仪表 | 10416篇 |
建筑科学 | 16014篇 |
矿业工程 | 15201篇 |
能源动力 | 9612篇 |
轻工业 | 25314篇 |
水利工程 | 9065篇 |
石油天然气 | 13987篇 |
武器工业 | 4418篇 |
无线电 | 35122篇 |
一般工业技术 | 33289篇 |
冶金工业 | 8177篇 |
原子能技术 | 2204篇 |
自动化技术 | 58731篇 |
出版年
2024年 | 3070篇 |
2023年 | 5300篇 |
2022年 | 7217篇 |
2021年 | 8805篇 |
2020年 | 10757篇 |
2019年 | 19158篇 |
2018年 | 20696篇 |
2017年 | 22197篇 |
2016年 | 21803篇 |
2015年 | 21730篇 |
2014年 | 21009篇 |
2013年 | 20717篇 |
2012年 | 20813篇 |
2011年 | 17207篇 |
2010年 | 15706篇 |
2009年 | 12723篇 |
2008年 | 10682篇 |
2007年 | 10221篇 |
2006年 | 8478篇 |
2005年 | 7410篇 |
2004年 | 9629篇 |
2003年 | 7443篇 |
2002年 | 7108篇 |
2001年 | 6198篇 |
2000年 | 5519篇 |
1999年 | 4694篇 |
1998年 | 4059篇 |
1997年 | 3627篇 |
1996年 | 3449篇 |
1995年 | 3496篇 |
1994年 | 2860篇 |
1993年 | 2659篇 |
1992年 | 2599篇 |
1991年 | 1876篇 |
1990年 | 1474篇 |
1989年 | 1395篇 |
1988年 | 1048篇 |
1987年 | 319篇 |
1986年 | 284篇 |
1985年 | 220篇 |
1984年 | 143篇 |
1983年 | 106篇 |
1982年 | 151篇 |
1981年 | 156篇 |
1980年 | 114篇 |
1976年 | 227篇 |
1975年 | 204篇 |
1972年 | 235篇 |
1971年 | 128篇 |
1960年 | 206篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
农村通信如何"突围" 总被引:2,自引:0,他引:2
农村通信作为农村地区信息化的基础,对于全面建设小康具有特殊的重要地位。介绍了我国农村通信的发展现状,分析了农村通信发展的困难压其原因,最后对农村压边远、欠发达地区通信的均衡震展提出了一些建议。 相似文献
12.
Marcia Cristina Kaezer Fran a Rosane Aguiar da Silva San Gil Jean-Guillaume Eon 《Catalysis Today》2003,78(1-4):105-115
γ-Al2O3 supported vanadium oxides were modified by tungsten and molybdenum oxides in order to improve dispersion and selectivity towards olefins in propane oxidative dehydrogenation (ODH). Both vanadium–tungsten and vanadium–molybdenum catalysts were obtained by adsorption of mixed isopolyanions (VW5O195−, V2W4O194−, VMo5O195− and V2Mo4O194−) from aqueous solutions. The isopolyanion solutions were characterized by UV-Vis and 51V NMR spectroscopy. Vanadium, vanadium–tungsten and vanadium–molybdenum precursors and catalysts were also characterized by UV-Vis (diffuse reflectance) and solid state 51V NMR spectroscopy. An improved selectivity to propene in the presence of tungsten and molybdenum in VOx/γ-Al2O3 was observed and attributed to dilution of vanadium by tungsten or molybdenum oxides on the γ-Al2O3 surface. 相似文献
13.
The size effects on the mean values of the mechanical properties of condensed matter and on the related variances are analysed by means of a unified approach based on the multiscale character of energy dissipation. In particular, the scaling law for fragmentation energy density is obtained taking into account the self-similarity of fragments. It is based on a generalization of the three classical comminution laws that has been performed to evaluate the energy dissipation, computing volume and surface area of the particles for one- two- and three-dimensional fragmented objects. The result is general and can be applied to different fractal energy dissipation mechanisms, e.g., plasticity. Based on this approach, the scaling laws for mean and standard deviation values of the main mechanical properties of materials can be derived, like Young's and shear elastic moduli, ultimate normal and shear stresses and strains, fracture energy and toughness. 相似文献
14.
15.
16.
Stewart C. Kai Shen Dwarkadas S. Scott M.L. Jian Yin 《Distributed Systems Online, IEEE》2004,5(10):1-1
The growth of the Internet and of various intranets has spawned a wealth of online services, most of which are implemented on local-area clusters using remote invocation (for example, remote procedure call/remote method invocation) among manually placed application components. Component placement can be a significant challenge for large-scale services, particularly when application resource needs are workload dependent. Automatic component placement has the potential to maximize overall system throughput. The key idea is to construct (offline) a mapping between input workload and individual-component resource consumption. Such mappings, called component profiles, then support high-performance placement. Preliminary results on an online auction benchmark based on J2EE (Java 2 Platform, Enterprise Edition) suggest that profile-driven tools can identify placements that achieve near-optimal overall throughput. 相似文献
17.
托盘能否有效运用对物流的畅通与否关系重大,这已经引起了国内外专家和学者们的重视,并就此制定了托盘电子信息化管理系统,旨在更合理地使用托盘,推进托盘一体化和共用系统的建立。而RFID技术在托盘的电子信息化管理的应用更将大大提高物流的效率与准确性,托盘电子信息化管理将成为今后托盘管理的趋势。 相似文献
18.
19.
20.
We present calculations of the magnetoconductivity in a two-dimensional electron system including the Rashba spin-orbit interaction. Essential for these calculations is an extension of the self-consistent Born approximation which takes into account the electron spin degree of freedom. The calculated magnetoconductivity exhibits, besides the beating in the Shubnikov-de Haas oscillations, a modulation related to the spin-orbit induced crossings of Landau levels, as a consequence of spin-conserving scattering between spin-orbit coupled states. 相似文献