全文获取类型
收费全文 | 258969篇 |
免费 | 29361篇 |
国内免费 | 8566篇 |
专业分类
电工技术 | 12714篇 |
技术理论 | 13篇 |
综合类 | 11708篇 |
化学工业 | 54440篇 |
金属工艺 | 12272篇 |
机械仪表 | 14997篇 |
建筑科学 | 16358篇 |
矿业工程 | 5456篇 |
能源动力 | 8040篇 |
轻工业 | 22378篇 |
水利工程 | 3798篇 |
石油天然气 | 10846篇 |
武器工业 | 1405篇 |
无线电 | 33794篇 |
一般工业技术 | 40518篇 |
冶金工业 | 13112篇 |
原子能技术 | 2545篇 |
自动化技术 | 32502篇 |
出版年
2024年 | 946篇 |
2023年 | 3937篇 |
2022年 | 7179篇 |
2021年 | 10040篇 |
2020年 | 8522篇 |
2019年 | 8622篇 |
2018年 | 9579篇 |
2017年 | 10460篇 |
2016年 | 10503篇 |
2015年 | 12062篇 |
2014年 | 14573篇 |
2013年 | 18454篇 |
2012年 | 17608篇 |
2011年 | 18588篇 |
2010年 | 15909篇 |
2009年 | 15304篇 |
2008年 | 14337篇 |
2007年 | 12854篇 |
2006年 | 12631篇 |
2005年 | 10810篇 |
2004年 | 7980篇 |
2003年 | 7071篇 |
2002年 | 6397篇 |
2001年 | 5671篇 |
2000年 | 5475篇 |
1999年 | 5445篇 |
1998年 | 5035篇 |
1997年 | 3930篇 |
1996年 | 3540篇 |
1995年 | 2776篇 |
1994年 | 2267篇 |
1993年 | 1709篇 |
1992年 | 1339篇 |
1991年 | 1070篇 |
1990年 | 834篇 |
1989年 | 705篇 |
1988年 | 573篇 |
1987年 | 423篇 |
1986年 | 334篇 |
1985年 | 247篇 |
1984年 | 213篇 |
1983年 | 154篇 |
1982年 | 125篇 |
1981年 | 111篇 |
1980年 | 96篇 |
1979年 | 62篇 |
1978年 | 55篇 |
1977年 | 68篇 |
1976年 | 90篇 |
1975年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
991.
本文以中国雕版印刷博物馆及扬州博物馆设计为例,从空间意象、理水设计、造形元素等方面对特定历史条件、自然条件下的建筑创作进行了探讨。 相似文献
992.
993.
讨论了西气东输管线空间数据库的建立过程,并以该空间数据库为后台利用MapInfo公司的GIS组件MapX进行二次开发,实现了全数字化的输气管道信息的存储与查询,使输气管线信息化管理更加现代化。 相似文献
994.
Imperfection in information can be considered a crosscutting concern that manifests itself in diverse kinds of imprecision, uncertainty, or inconsistency in the data models of a software system. The extension of existing programming and querying interfaces for the different aspects of information imperfection requires a proper modularization of the different concerns of numerical imprecision handling, so that the extensions do not interfere with existing programming practices and do not obscure the original design. Aspect‐oriented design (AOD) enables such a form of nonintrusive extensions to be added to existing software libraries, clearly separating fuzziness or other imperfections in data as a differentiated concern that can be considered from the early phases of development. In this article, a general framework for aspect‐based extension of data models and fuzzy databases is described, and some design and implementation issues of such AOD‐based extensions on OJB database libraries are described as a case study. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 1199–1216, 2006. 相似文献
995.
In a mobile ad hoc network, difficulties exist in supporting address autoconfiguration and naming resolution due to the lack of centralized servers. This letter presents a novel approach, called name‐based autoconfiguration (NBA), which uses host names to determine IP addresses and provides address autoconfiguration and name resolution as a single protocol. 相似文献
996.
Ernest Marco‐Urrea Xavier Gabarrell Gloria Caminal Teresa Vicent C Adinarayana Reddy 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(9):1190-1196
BACKGROUND: Trichloroethylene (TCE) and perchloroethylene (PCE) are considered among the most important groundwater pollutants around the world. These compounds are usually found together in polluted environments but little is known about the ability of microorganisms to simultaneously degrade TCE and PCE. RESULTS: Data showed that several species of white‐rot fungi, including Trametes versicolor, Ganoderma lucidum, and Irpex lacteus, degrade substantial levels of TCE in pure culture. T. versicolor was chosen for further study since it degraded higher levels of TCE than the other organisms. Initial glucose concentration and reoxygenation of samples increased the amount of TCE dechlorination, but no significant difference in percentage TCE degradation was observed. T. versicolor was able to degrade 34.1 and 47.7% of PCE and TCE added as mixtures (containing 5 and 10 mg L−1, respectively). CONCLUSIONS: The degradation ability of TCE was extended to other species of white‐rot fungi. Percentage degradation as well as chloride release from mixtures of TCE and PCE showed that T. versicolor degrades mixtures of TCE and PCE almost as well as its ability to degrade individually added TCE or PCE. The results suggest the potential promise of T. versicolor for bioremediation of TCE and PCE in the environment. Copyright © 2008 Society of Chemical Industry 相似文献
997.
The objective of this study is to determine the chemical kinetics of desulphurization of Thai limestone in an atmospheric fluidized bed combustor (AFBC). The experiments, which employed the batch technique using the limestone samples from six major sources in Thailand, were performed in a laboratory‐scale AFBC. The results obtained were analysed and correlated in the form of apparent reaction rate and deactivation rate constants as a function of operating conditions of the furnace and their properties, respectively. The formulae derived from these correlations were kept as general as possible in order that they could be used as input parameters for the selected mathematical model of desulphurization in an AFBC that is suitable for practical use. The predicted results were in good agreement with the experimental data reported in the literature. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
998.
999.
S.K. Lee D.‐H. Hwang B.‐J. Jung N.S. Cho J. Lee J.‐D. Lee H.‐K. Shim 《Advanced functional materials》2005,15(10):1647-1655
By using Ni0‐mediated polymerization, we have systematically synthesized a series of fluorene‐based copolymers composed of blue‐, green‐, and red‐light‐emitting comonomers with a view to producing polymers with white‐light emission. 2,7‐Dibromo‐9,9‐dihexylfluorene, {4‐(2‐[2,5‐dibromo‐4‐{2‐(4‐diphenylamino‐phenyl)‐vinyl}‐phenyl]‐vinyl)‐phenyl}‐diphenylamine (DTPA), and 2‐{2‐(2‐[4‐{bis(4‐bromo‐phenyl)amino}‐phenyl]‐vinyl)‐6‐tert‐butyl‐pyran‐4‐ylidene}‐malononitrile (TPDCM) were used as the blue‐, green‐, and red‐light‐emitting comonomers, respectively. It was found that the emission spectra of the resulting copolymers could easily be tuned by varying their DTPA and TPDCM content. Thus with the appropriate red/green/blue (RGB) unit ratio, we were able to obtain white‐light emission from these copolymers. A white‐light‐emitting diode using the polyfluorene copolymer containing 3 % green‐emitting DTPA and 2 % red‐emitting TPDCM (PG3R2) with a structure of indium tin oxide/poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonic acid)/PG3R2/Ca/Al was found to exhibit a maximum brightness of 820 cd m–2 at 11 V with Commission Internationale de L'Eclairage (CIE) coordinates of (0.33,0.35), which are close to the standard CIE coordinates for white‐light emission (0.33,0.33). 相似文献
1000.