全文获取类型
收费全文 | 190435篇 |
免费 | 18526篇 |
国内免费 | 10887篇 |
专业分类
电工技术 | 14479篇 |
技术理论 | 13篇 |
综合类 | 20017篇 |
化学工业 | 18177篇 |
金属工艺 | 7629篇 |
机械仪表 | 16490篇 |
建筑科学 | 21836篇 |
矿业工程 | 7176篇 |
能源动力 | 8176篇 |
轻工业 | 14351篇 |
水利工程 | 8636篇 |
石油天然气 | 9614篇 |
武器工业 | 2111篇 |
无线电 | 11844篇 |
一般工业技术 | 18033篇 |
冶金工业 | 7388篇 |
原子能技术 | 2666篇 |
自动化技术 | 31212篇 |
出版年
2024年 | 798篇 |
2023年 | 2350篇 |
2022年 | 4752篇 |
2021年 | 5541篇 |
2020年 | 5878篇 |
2019年 | 4915篇 |
2018年 | 4854篇 |
2017年 | 5912篇 |
2016年 | 7104篇 |
2015年 | 7537篇 |
2014年 | 12088篇 |
2013年 | 12174篇 |
2012年 | 14029篇 |
2011年 | 15590篇 |
2010年 | 11260篇 |
2009年 | 11521篇 |
2008年 | 10917篇 |
2007年 | 13088篇 |
2006年 | 11357篇 |
2005年 | 9531篇 |
2004年 | 8077篇 |
2003年 | 6845篇 |
2002年 | 5543篇 |
2001年 | 4515篇 |
2000年 | 3860篇 |
1999年 | 3234篇 |
1998年 | 2768篇 |
1997年 | 2304篇 |
1996年 | 1918篇 |
1995年 | 1608篇 |
1994年 | 1452篇 |
1993年 | 1067篇 |
1992年 | 985篇 |
1991年 | 711篇 |
1990年 | 602篇 |
1989年 | 519篇 |
1988年 | 416篇 |
1987年 | 289篇 |
1986年 | 249篇 |
1985年 | 242篇 |
1984年 | 273篇 |
1983年 | 253篇 |
1982年 | 209篇 |
1981年 | 105篇 |
1980年 | 103篇 |
1979年 | 75篇 |
1978年 | 60篇 |
1977年 | 55篇 |
1976年 | 45篇 |
1959年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
段群章 《有色金属材料与工程》1993,(1)
本文评述了近年来苯基荧光酮类试剂在金属及合金光度分析中应用的发展状况,显色反应的条件,以及相应光度分析方法的检测限和测定范围等。参考文献87篇。 相似文献
162.
李胜强 《中国图象图形学报》1997,2(9):646-651
探讨GIS技术在空间工程辅助设计(例如电力、电信管线工程)方面的应用.在系统分析空间工程设计的
逻辑过程和工程辅助设计系统的发展与需求的基础上,对GIS技术在空间工程辅助设计中应用的优势及工程辅助
设计GIS系统的结构、功能和特点以及系统基本设计思路进行了探讨,指出GIS技术的引入一方面提高了空间工
程辅助设计的效率和水平,同时使空间工程辅助设计成为同时具有规划和设计功能的系统。 相似文献
163.
本文提出了用一个标样进行系列试样 X 射线定量相分析的方法.它克服了一般 X 射线定量方法需要混合研磨和手续烦复的缺点以及无标样 X 射线定量方法存在病态方程不易解决的问题.该方法对常规 X 射线定量分析具有普遍的实用性. 相似文献
164.
In order to cumpare the peformance of different supply diffuers of ventilation air, the airflow passern, temperature stratifiation and contaminant dispersion in a furnitured office ventilated by three kinds of air diffuer were numerically investigated. The air diffuers studied in this paper are a quarter-cylinder displacement diffuer on the floor and mixing diffuers (linear and vortex diffuers) on the ceiling. The heat sources in the of-fice are considered to be 50% convective and 50% radiative. The k-? two-equatwn model of turbulence is employed to predict the turbulent diffusion. The results show that the displacement diffuser provides a rather uniform flow field with low velocify in most areas, and the vertical temperature difference from floor to ceiling is as high as 6 K. With the linear diffuser, the air velociry is high, and the temperature is uniform both horizontally and vertically. The air velocity generated by the vortex diffuser is moderate. The distributions of the temperature and the contaminant are rather uniform. 相似文献
165.
基于神经网络的降雨径流预报 总被引:2,自引:0,他引:2
本文将人工神经网络应用于二滩水电站以上支流鱼河的降雨径流预报,通过建模、计算、比较和分析可知,其非线性映射能力、自学习能力和灵活性,均能较好地反映降雨径流之间的非线性的、复杂的转换关系,结合流域水文特性并合理处理建模数据,值得进一步深入研究。 相似文献
166.
Macroscopic analysis of design processes based on a scheme for coding designers' cognitive actions 总被引:1,自引:0,他引:1
We have devised a new scheme for coding designers' cognitive actions from video/audio design protocols. Designers' actions are coded into four cognitive levels; physical, perceptual, functional and conceptual. Relations between actions belonging to different levels, such as dependencies and triggering relations, are also coded. The present scheme has two benefits. First, we found that design actions are definable in a systematic way using the vocabulary of the scheme, and thus a designer's cognitive behaviours in each of local design stages is represented as a structure composed of defined primitive actions. This is expected to lay the foundation for microscopic analyses of how particular types of actions contribute to the formation of key design ideas. Second, this scheme is suitable for macroscopic analyses of how designers cognitively interact with their own sketches. We examined, for a practising architect, the ways in which drawing, inspection of drawings, perception, and functional thoughts correlated with one another in his design process. The findings suggest that design sketches serve not only as external memory or as a provider of visual cues for association of non-visual information, but also as a physical setting in which design thoughts are constructed on the fly. 相似文献
167.
The interaction of different metal oxides such as Co3O4, NiO, Al2O3, Cr2O3, Fe2O3 and SiO2 with Na2SO4 at a temperature of 1100 and 1200 K in flowing oxygen has been studied. The thermogravimetric studies for each system were
carried out as a function of Na2SO4 in the mixture. The presence of different constituents in the reaction products were identified by X-ray diffraction analysis
and the morphologies of the reaction products were characterized using metallography and scanning electron microscopy (SEM).
The formation of products was also investigated by thermodynamic computation of free energies of the reactions and the study
of relevant equilibrium phase diagrams. The soluble species in the aqueous solutions of the reaction products were determined
quantitatively using atomic absorption spectrophotometry.
The high temperature interaction products usually contain a 3-phase structure namely, Na2O·M2O
x
, M2O
x
and metal sulphide and/or metal sulphate. The formation of Na2O·M2O
x
depends upon the solid state solubility of metal oxide in the molten salt at high temperatures. Under limited solubility
conditions Na2O·M2O
x
is invariably formed, but as soon as this condition is relaxed the oxide. M2O
x
, precipitates and forms a separate phase. 相似文献
168.
用标准C语言在IBM-PC兼容微机上开发了基于PROSITE数据库检索蛋白质序列功能位点的PPS程序,PROSITE是Bairoch建立的蛋白质功能位点或结构模式的资料库,为蛋白质序列分析和结构功能研究提供了新工具。 相似文献
169.
Neil Kirkpatrick 《Packaging Technology and Science》1993,6(3):159-172
Solid-waste management, and in particular the disposal of used packaging, is currently the subject of much topical debate. This is driven by both consumer and legislative pressures. Consumers see used packaging as a highly visible element of municipal solid waste, complaining of excessive packaging and low levels of recycling. Legislators, perhaps in pandering to the views expressed by consumer bodies, have been active within the CEC and individual Member States by introducing (or proposing) legislation or similar regulatory tools and targets to facilitate a greater diversion of used packaging from disposal by landfill to alternative solid-waste management practices, in particular recycling, which are widely accepted to have a lower impact on the environment. In this paper the relative environmental profiles of pursuing alternative solid-waste management practices to disposal by landfill are explored, focusing not just on solid waste per se but also on associated considerations of energy consumption and emissions, which are invariably overlooked as factors contributing to the environmental impact of solid-waste management practices. 相似文献
170.
Laminated beams subjected to transverse load 总被引:2,自引:0,他引:2
I.M. Allison 《Strain》1998,34(3):91-94
A simple elastic solution has been developed for predicting the shear stress distribution in a laminated beam subjected to a variety of transverse loading conditions. Photoelastic tests on composite models involving a single bonding layer have been used to validate the theory, and also to comment upon the significance of these results in interpreting the interlaminar shear strength and bending modulus of the simplest form of laminated strip. 相似文献