全文获取类型
收费全文 | 7592篇 |
免费 | 379篇 |
国内免费 | 318篇 |
专业分类
电工技术 | 267篇 |
综合类 | 304篇 |
化学工业 | 787篇 |
金属工艺 | 509篇 |
机械仪表 | 1030篇 |
建筑科学 | 131篇 |
矿业工程 | 192篇 |
能源动力 | 198篇 |
轻工业 | 744篇 |
水利工程 | 46篇 |
石油天然气 | 231篇 |
武器工业 | 58篇 |
无线电 | 763篇 |
一般工业技术 | 480篇 |
冶金工业 | 126篇 |
原子能技术 | 57篇 |
自动化技术 | 2366篇 |
出版年
2024年 | 6篇 |
2023年 | 61篇 |
2022年 | 94篇 |
2021年 | 144篇 |
2020年 | 126篇 |
2019年 | 124篇 |
2018年 | 140篇 |
2017年 | 161篇 |
2016年 | 182篇 |
2015年 | 232篇 |
2014年 | 347篇 |
2013年 | 360篇 |
2012年 | 437篇 |
2011年 | 613篇 |
2010年 | 373篇 |
2009年 | 352篇 |
2008年 | 390篇 |
2007年 | 530篇 |
2006年 | 482篇 |
2005年 | 378篇 |
2004年 | 340篇 |
2003年 | 336篇 |
2002年 | 269篇 |
2001年 | 222篇 |
2000年 | 215篇 |
1999年 | 217篇 |
1998年 | 190篇 |
1997年 | 164篇 |
1996年 | 166篇 |
1995年 | 122篇 |
1994年 | 100篇 |
1993年 | 82篇 |
1992年 | 79篇 |
1991年 | 38篇 |
1990年 | 45篇 |
1989年 | 48篇 |
1988年 | 23篇 |
1987年 | 21篇 |
1986年 | 14篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有8289条查询结果,搜索用时 31 毫秒
31.
32.
33.
集成光学干涉仪光纤陀螺 总被引:2,自引:0,他引:2
简述了集成光学干涉仪光纤陀螺(FOG)的技术优势、发展概况和采用的技术途径,介绍了适用于不同技术条件要求的三种多功能集成光学芯片结构和相应的信息处理方法。简要地概括了目前国外FOG的发展水平。 相似文献
34.
The primary purpose of this work is to review the literature about what is and is not known about using ethylene vinyl acetate (EVA0 copolymer as the encapsulant (or pottant) material in photovoltaic (PV) modules. Secondary purposes include elucidating the complexity of the encapsulation problem, providing an overview about encapsulation of PV cells and modules, providing a historical overview of the relevant research and development on EVA, summarizing performance losses reported for PV systems deployed since ca. 1981, and summarizing the general problems of polymer stability in a solar environment. We also provide a critical review of aspects of reported work for cases that we believe are important.Failure modes resolved in the early work to establish reliability of deployed modules and the purposes and properties of pottants, are summarized. Typical performance losses in large field-deployed, large-scale systems ranging from 1% to 10% per year are given quantitatively, and qualitative reports of EVA discoloration are summarized with respect to ultraviolet (UV), world-wide location and site dependence.The general stability of polymers and their desirable bulk properties for solar utilization are given. The stabilization formulation for EVA, its effectiveness, and changes in it during degradation are discussed. The degradation mechanisms for the base resin, e.g., unstabilized Elvax 150TM, and stabilized EVA are indicated for literature dating to the early 1950s, and the role played by unsaturated chromophores is indicated. The limited number of studies relating discoloration and PV cell efficiency are summarized.Observed degradation of EVA or the unstabilized base resin in the laboratory and examples used to measure the degradation are summarized in sections entitled: (1) thermally-induced degradation; (2) photodegradation and photothermal degradation of EVA in different temperature regimes; (3) photobleaching and photodegradation of the UV absorber and cross-linking agent; (4) acetic acid and metal and metal-oxide catalyzed oxidative degradation; and (5) discolaration and PV cell efficiency losses.Processing effects/influences on EVA stability are discussed in sections entitled: (1) EVA raw materials and extruded, uncured films; (2) thermal encapsulation processes; (3) effects of lamination, curing, and curing peroxide on gel content and chromophores formed; and (4) incomplete shielding of curing-generated chromophores. A summary is given for the limited number of accelerated lifetime testing efforts and examples of erroneous service lifetime predictions for EVA are discussed. The known factors that effect the discoloration rate of several EVA formulations are discussed in which the reduction in rate by using UV-absorbing superstrates is a prime example. A summary is given of what is and is not known about EVA degradation mechanisms, degradation from exposures in field-deployed modeules and/or laboratory testing, and factors that contribute to EVA stability or degradation. Finally, conclusions about using Elvax 150 in EVA formulations are summarized, and future prospects for developing the next-generation pottant for encapsulating PV modules are discussed. 相似文献
35.
Pierluigi Guerrini De LucaClaudio Scali 《Chemical engineering science》2002,57(11):2077-2087
Applicability of different temperature oscillation calorimetry algorithms, previously proposed in the literature, for the evaluation of the heat transfer coefficient during the course of the reaction, is analysed by referring to the experimental data from a methyl methacrylate polymerisation reactor.Results are coincident in the nominal case (no errors on data), while differences appear in the elaboration of real data. The effect of uncertainty in the experimental data has been simulated in terms of error on the amplitude and on the phase of reactor and jacket temperature profiles.This approach allows to indicate algorithms having the best robustness properties and to give an explanation of phase errors in terms of a lumped parameter which accounts for different phenomena, not included in the basic hypotheses of the method. Based on this observation, a procedure to eliminate this source of errors from experimental data is proposed for the more general algorithm presented to handle oscillating temperature profiles generated by different techniques. 相似文献
36.
37.
Decision support systems depend on a variety of knowledge management techniques. These range from data base management, programming, and spreadsheet analysis to rule set management and automated inference. One valuable knowledge management technique that has yet to find its way into the repertoire of decision support system developers is general-purpose demon management. This article identifies and explores the major issues pertaining to the integration of demon representation and processing into a knowledge management environment. These serve as a basis for design and implementation of more flexible and powerful environments for decision support. 相似文献
38.
39.
云南锰矿资源丰富,具有品位高、低磷低铁、易选等特点。文章概述了斗南、鹤庆、建水等锰矿的选矿科研进展情况,三个锰矿均可采用强磁选或磁-重选流程选别,可提高品位8—12%;精矿含锰可达33—35%,锰回收率在80%以上的好结果。 相似文献
40.