全文获取类型
收费全文 | 275161篇 |
免费 | 27045篇 |
国内免费 | 15669篇 |
专业分类
电工技术 | 22792篇 |
技术理论 | 9篇 |
综合类 | 26481篇 |
化学工业 | 31260篇 |
金属工艺 | 16712篇 |
机械仪表 | 21888篇 |
建筑科学 | 28098篇 |
矿业工程 | 9832篇 |
能源动力 | 13221篇 |
轻工业 | 18948篇 |
水利工程 | 9932篇 |
石油天然气 | 16491篇 |
武器工业 | 3089篇 |
无线电 | 20427篇 |
一般工业技术 | 28662篇 |
冶金工业 | 12930篇 |
原子能技术 | 4411篇 |
自动化技术 | 32692篇 |
出版年
2024年 | 1163篇 |
2023年 | 3615篇 |
2022年 | 7071篇 |
2021年 | 8324篇 |
2020年 | 8776篇 |
2019年 | 7300篇 |
2018年 | 7036篇 |
2017年 | 8959篇 |
2016年 | 10273篇 |
2015年 | 10768篇 |
2014年 | 17051篇 |
2013年 | 17308篇 |
2012年 | 20323篇 |
2011年 | 22214篇 |
2010年 | 15887篇 |
2009年 | 16315篇 |
2008年 | 14992篇 |
2007年 | 18397篇 |
2006年 | 16433篇 |
2005年 | 13655篇 |
2004年 | 11709篇 |
2003年 | 10070篇 |
2002年 | 8218篇 |
2001年 | 6898篇 |
2000年 | 5954篇 |
1999年 | 4948篇 |
1998年 | 4103篇 |
1997年 | 3533篇 |
1996年 | 3004篇 |
1995年 | 2416篇 |
1994年 | 2153篇 |
1993年 | 1551篇 |
1992年 | 1409篇 |
1991年 | 1101篇 |
1990年 | 915篇 |
1989年 | 754篇 |
1988年 | 597篇 |
1987年 | 379篇 |
1986年 | 336篇 |
1985年 | 296篇 |
1984年 | 334篇 |
1983年 | 290篇 |
1982年 | 236篇 |
1981年 | 121篇 |
1980年 | 129篇 |
1979年 | 86篇 |
1978年 | 57篇 |
1977年 | 54篇 |
1976年 | 47篇 |
1959年 | 51篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
821.
本文介绍了宽低温STN-LCD加热装置的设计和制备方法,并对低温加热的实验结果进行了讨论和分析,相应的研究结果表明此法有利于拓宽STN液晶显示器的负温工作范围。 相似文献
822.
M. J. Vissenberg P. W. de Bont E. M. van Oers R. A. de Haan E. Boellaard A. M. van der Kraan V. H. J. de Beer R. A. van Santen 《Catalysis Letters》1996,40(1-2):25-29
Ion exchanged CoNaY was sulfided at 473 and 673 K and subsequently heated in He at 673 and 773 K. The resulting samples were characterized by means of overall sulfur analysis, temperature programmed Ar treatment and Fourier transform infrared spectroscopy. It was shown that during He flushing at sufficiently high temperature a protolysis reaction occurs resulting in the decomposition of Co sulfide into Co2+ ions and H2S. 相似文献
823.
Jaroslav Mackerle 《International Journal of Pressure Vessels and Piping》1996,69(3):279-339
The paper gives a bibliographical review of the finite element methods (FEMs) applied for the analysis of pressure vessel structures/components and piping from the theoretical as well as practical points of view. The range of applications of FEMs in this area is wide and cannot be presented in a single paper; therefore the aim of this review is to give the reader an encyclopaedic view of the differnt possibilities that exist today for the finite element analysis in the fields of pressure vessels and piping. The bibliography at the end of the paper contains approximately 1900 references to papers, conference proceedings and theses/dissertations on the subject that were published in 1976–1996. These are classified in the following categories: linear and non-linear, static and dynamic, stress and deflection analysis; stability problems; thermal problems; fracture mechanics problems; contact problems; fluid-structure interaction problems; manufacturing of pipes and tubes; welded pipes and pressure vessel components; development of special finite elements for pressure vessels and pipes; finite element software; and other topics. Also finite element software, general purpose and special purpose codes, used for the analysis of pressure vessels and pipes are briefly discussed and presented. 相似文献
824.
S. Scalat D. Banu D. Hawes J. Parish F. Haghighata D. Feldman 《Solar Energy Materials & Solar Cells》1996,44(1):49
Full scale thermal storage tests were conducted in a room lined with PCM wallboard having latent heat storage capacity. The results were compared with those obtained from tests conducted in a similar room lined with ordinary wallboard. The research showed that PCM wallboard can function efficiently as a thermal storage medium which can be applied to peak load shifting, improved use of waste and solar heat as well as more efficient operation of heating and cooling equipment. 相似文献
825.
纤维素酶分子的计算机辅助序列分析 总被引:3,自引:0,他引:3
利用生物大分子数据库(EMBL、SWALL和PDB)及软件技术(DNASIS和AntheProt)对嗜热子囊菌(Thermoascus aurantiacus)的产生的一种纤维素酶分子进行了序列分析及结构预测;通过多种来源的纤维素酶的比较研究,分析了其催化区、活性位点及局部保守序列。 相似文献
826.
结合当前我国建材市场的形势 ,就建材市场“涨价风潮”的起因 ,从经济增长的结果、市场运行的规律等方面进行了论述 ,提出了涨价风潮对近期全国建材市场的影响 相似文献
827.
The engineering and management of human safety is an important societal objective that includes extensive efforts by governments, both legislative and administrative, to enhance the health and safety of the public. Although the achievement of safety goals depend primarily on individuals and organizations responsible for safety, much support is drawn from expertise in diverse scientific and engineering disciplines. The activities range from structural safety (dams, tunnels, bridges to tall buildings) to safe operation of hazardous industrial installations (energy generation facilities, LNG terminals, petrochemical plants) to transportation systems (airline, rail, car safety) to technologies designed to minimize adverse impacts on the environment. All these activities are crucially concerned with risk: with the likelihood and the probable effects of various measures on life and health. We have developed a unified rationale and a clear basis for effective strategic management of risk across diverse sectors. Safety is an important objective in society but it is not the only one. The allocation of society's resources devoted to safety must be continually appraised in light of competing needs, because there is a limit on the resources that can be expended to extend life. The paper presents the Life Quality Index (LQI) as a tool for the assessment of risk reduction initiatives that would support the public interest and enhance safety and quality of life. The paper provides an intuitive reformulation of the LQI as equivalent to a valid utility function that is consistent with the principles of rational decision analysis. The LQI is further refined to consider the issues of discounting of life years, competing background risks, and population age and mortality distribution. The LQI is applied to quantify the societal willingness-to-pay, which is an acceptable level of public expenditure in exchange for a reduction in the risk of death that results in improved life-quality. 相似文献
828.
塔里木盆地地热场特征与油气 总被引:2,自引:0,他引:2
作者在收集了34口井的地温,部分井岩心和能谱测井资料的基础上,对塔里木盆地的地热场进行了研究,编制出盆地地温梯度图和深度分别为1000m、3000m、5000m的地温图。计算出盆地平均地温梯度为19.75℃/km,平均大地热流值为39.19mW/m~2,指出塔里木盆地地热场低于我国中、东部盆地,具“冷盆”性质。叶城凹陷地温梯度小于16℃/km,大地热流值为34.42mW/m~2,是盆内地热场最低之处,与前陆坳陷低地热场之特点一致。作者对塔里木盆地地热场特征进行分析后,得出了塔里木盆地最利于油气两种相态并存的结论。 相似文献
829.
为了研究带电粒子光学系统的光学特性,需要知道系统中磁场的空间分布。实际磁场往往不具有严格的平面对称性质,一些作者曾就这类磁场的空间展开做过不少工作。但他们的工作是在柱坐标系统中进行的,适用于诸如回旋加速器、双向聚焦磁分析器、环形磁β谱仪等一类装置的磁场分析。对于大型同位素电磁分离器(calutron)那样一类装置,其磁场分布需要 相似文献
830.
^17O系统的R矩阵分析 总被引:2,自引:1,他引:1
采用多道多能级R矩阵理论,全面系统地分析~(17)O系统中10.5 MeV激发能以下有关~(16)O(n,n)~(16)O·~(16)O(n,a)~(13)C和~(13)C(a,a)~(13)C的全部实验数据。有关~(16)O的中子反应截面计算值被收入中国评价数据库CENDL-2和美国的评价数据库ENDF/B-6。对在R矩阵分析中如何确定本底、道半径和边界条件等问题予以讨论。 相似文献