全文获取类型
收费全文 | 228214篇 |
免费 | 73882篇 |
国内免费 | 50391篇 |
专业分类
电工技术 | 32110篇 |
综合类 | 27181篇 |
化学工业 | 28611篇 |
金属工艺 | 28340篇 |
机械仪表 | 9840篇 |
建筑科学 | 15211篇 |
矿业工程 | 15442篇 |
能源动力 | 9435篇 |
轻工业 | 25789篇 |
水利工程 | 8870篇 |
石油天然气 | 13989篇 |
武器工业 | 4510篇 |
无线电 | 33740篇 |
一般工业技术 | 32194篇 |
冶金工业 | 8358篇 |
原子能技术 | 2241篇 |
自动化技术 | 56626篇 |
出版年
2024年 | 2997篇 |
2023年 | 5131篇 |
2022年 | 6966篇 |
2021年 | 8034篇 |
2020年 | 10364篇 |
2019年 | 18787篇 |
2018年 | 20336篇 |
2017年 | 21927篇 |
2016年 | 21406篇 |
2015年 | 21239篇 |
2014年 | 20669篇 |
2013年 | 20330篇 |
2012年 | 20569篇 |
2011年 | 16904篇 |
2010年 | 15812篇 |
2009年 | 12567篇 |
2008年 | 10774篇 |
2007年 | 10112篇 |
2006年 | 8371篇 |
2005年 | 7432篇 |
2004年 | 9600篇 |
2003年 | 7465篇 |
2002年 | 6964篇 |
2001年 | 6183篇 |
2000年 | 5489篇 |
1999年 | 4589篇 |
1998年 | 3904篇 |
1997年 | 3502篇 |
1996年 | 3358篇 |
1995年 | 3432篇 |
1994年 | 2830篇 |
1993年 | 2628篇 |
1992年 | 2558篇 |
1991年 | 1864篇 |
1990年 | 1459篇 |
1989年 | 1371篇 |
1988年 | 1036篇 |
1987年 | 313篇 |
1986年 | 273篇 |
1985年 | 201篇 |
1984年 | 132篇 |
1983年 | 98篇 |
1982年 | 145篇 |
1981年 | 153篇 |
1980年 | 106篇 |
1976年 | 225篇 |
1975年 | 203篇 |
1972年 | 235篇 |
1971年 | 127篇 |
1960年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
A feasibility analysis methodology adopted from reactive distillation is applied to membrane reactors. A model is formulated to depict the reactive liquid phase composition on the retentate side of a continuous type membrane reactor. The effects of both the chemical reaction kinetics and the membrane mass transfer kinetics on the feasible products are elucidated by means of retentate phase diagrams and bifurcation analysis. The proposed method can be applied to various membrane processes, independent of the specific structure of the membrane. Two quaternary reaction systems are considered to illustrate the methodology. In the first hypothetical system, it is shown how selective membranes can influence the sequence of effective volatilities which in turn affects the feasible products of the system. In the second example of practical importance, i.e. the heterogeneously catalysed synthesis of propyl acetate coupled with permeation through a porous polycarbonate membrane, the dusty gas model is applied to describe the component fluxes through the membrane. For the latter reaction system, the existence of reactive arheotrope is demonstrated. Arheotropes represent mass transfer controlled feasible products of membrane separation process. 相似文献
52.
在第一部分综合讨论的基础上对甘三酯立体专一分析方法作了初步探讨。以液体油(菜油)及固体脂(猪脂)为基质,系统地研究了这一分析方法,取得了经验并补充了一些具体验证方法。分析液体油的结果与文献数据相一致,分析猪脂的结果欠佳,还存在一些问题需待进一步研究。 相似文献
53.
54.
A model of the electronic structure of graphite-like carbon films, describing the semiconductor properties of this material, is presented. Spectra of optical constants of microcrystalline carbon films in the region λ = 0.4–8.0 μm were studied by the spectral ellipsometry and IR reflection methods. A number of distinctive features of the spectra, associated with both the appearance of C---C- and C---Hn-type bonds and direct energy gaps, were found. Analysis of the optical data using the proposed model makes possible a common interpretation of our results and literature data. Values of a parameter Θ, which is an averaged qualitative parameter of structural distortions within carbon microcrystallites as compared with crystalline graphite, are determined from comparison of theoretical results and experimental data. 相似文献
55.
56.
Ying Ding Chunqing Wang Yanhong Tian Binbin Zhang 《Metallurgical and Materials Transactions A》2006,37(12):1017-1025
in-situ transmission electron microscopy (TEM) tensile tests on as-cast and aged 63Sn37Pb solder alloys were conducted, and the fracture
behavior in nanometer scale ahead of the crack tip was inspected and discussed. Results show that the fracture was completed
by connecting the discontinuous cracks or voids. Dislocation behavior was concentrated along the grain boundaries for as-cast
samples, and displayed mainly as dislocation climb. The crack was intergranular dominated under the lower strain rate. While
remarkable mutual dislocation emission was detected in the aged solder. Transgranular cracks were dominant in the fractured
area, and they propagated by linking up with the nanometer scale cracks ahead of the crack tips under the effective promotion
of the inverse dislocation emission. At the same time, the partial interphase or intergranular cracks in the thinned area
were also found. Under this condition, a new critical stress intensity factor K
c
′ to define the mutual dislocation emission was proposed. 相似文献
57.
58.
通过对镍氢电池性能的研究,给出了一个应用ISA总线技术构建的、基于DELPHI编程平台的镍氢电池管理系统的设计方案,重点介绍了该系统的软件技术和实现方法。 相似文献
59.
On sorting triangles in a delaunay tessellation 总被引:1,自引:0,他引:1
In a two-dimensional Delaunay-triangulated domain, there exists a partial ordering of the triangles (with respect to a vertex) that is consistent with the two-dimensional visibility of the triangles from that vertex. An equivalent statement is that a polygon that is star-shaped with respect to a given vertex can be extended, one triangle at a time, until it includes the entire domain. Arbitrary planar triangulations do not possess this useful property which allows incremental processing of the triangles.This work was partially supported by the National Science Foundation's US-Italy Collaborative Research Program under Grant INT-8714578 and Information, Robotics, and Intelligent Research Grant IRI-8704781. 相似文献
60.
The increasing complecity of many expert system application areas calls for the integration of the knowledge of multiple experts. The use of multiple experts introduces some interesting new problems during the process of knowledge acquisition. The problems are further complicated when the experts are geographically dispersed or unavailable for face-to-face interactions.
This article discusses the motivations for acquiring the knowledge of multiple experts, the problems related to knowledge acquisition, new issues that arise whens multiple experts interact, solutions that can be brought to bear in building multiple expert systems (particularly when experts are geographically dispersed), and new tools for knowledge engineers to use when dealing with multiple experts. 相似文献