全文获取类型
收费全文 | 20360篇 |
免费 | 2294篇 |
国内免费 | 1310篇 |
专业分类
电工技术 | 1721篇 |
综合类 | 2211篇 |
化学工业 | 1832篇 |
金属工艺 | 1794篇 |
机械仪表 | 2568篇 |
建筑科学 | 1552篇 |
矿业工程 | 1437篇 |
能源动力 | 834篇 |
轻工业 | 1154篇 |
水利工程 | 667篇 |
石油天然气 | 766篇 |
武器工业 | 301篇 |
无线电 | 1363篇 |
一般工业技术 | 2777篇 |
冶金工业 | 544篇 |
原子能技术 | 203篇 |
自动化技术 | 2240篇 |
出版年
2024年 | 85篇 |
2023年 | 291篇 |
2022年 | 600篇 |
2021年 | 640篇 |
2020年 | 740篇 |
2019年 | 581篇 |
2018年 | 593篇 |
2017年 | 746篇 |
2016年 | 876篇 |
2015年 | 917篇 |
2014年 | 1403篇 |
2013年 | 1402篇 |
2012年 | 1616篇 |
2011年 | 1679篇 |
2010年 | 1296篇 |
2009年 | 1218篇 |
2008年 | 1028篇 |
2007年 | 1398篇 |
2006年 | 1165篇 |
2005年 | 944篇 |
2004年 | 787篇 |
2003年 | 627篇 |
2002年 | 547篇 |
2001年 | 456篇 |
2000年 | 410篇 |
1999年 | 362篇 |
1998年 | 227篇 |
1997年 | 253篇 |
1996年 | 217篇 |
1995年 | 155篇 |
1994年 | 149篇 |
1993年 | 94篇 |
1992年 | 93篇 |
1991年 | 64篇 |
1990年 | 65篇 |
1989年 | 59篇 |
1988年 | 44篇 |
1987年 | 20篇 |
1986年 | 22篇 |
1985年 | 15篇 |
1984年 | 15篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1975年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 701 毫秒
81.
组织光学中的Monte Carlo方法 总被引:12,自引:5,他引:7
介绍了Monte Carlo方法产生的背景、基本思想及其在组织光学应用中的重要意义,评述了其在组织光学应用中的研究进展,对其发展趋势作了展望。 相似文献
82.
“Symmetric materials” devices, where both electrodes are made of the same electrochromic materials, allow the in situ study of side reactions. Each transferred charge that is not used for the expected electrochromic reaction will cause a colour change in the whole symmetric device. Two electrochromic materials, WO3 and IrO2, are successively used to show how to obtain information about side reactions such as faradaic efficiency, reversibility and potential limits from the symmetric experiment. This in situ approach with a polymer electrolyte shows significant differences compared to results obtained with studies in aqueous electrolytes. 相似文献
83.
T. Jeevananda Siddaramaiah Taek Su Lee Joong Hee Lee O. M. Samir R. Somashekar 《应用聚合物科学杂志》2008,109(1):200-210
Polyaniline/carboxylated multi-walled carbon nanotube (PAni/c-MWNT) nanocomposites have been synthesized by micellar aided emulsion polymerization with various c-MWNTs compositions, viz., 0.5, 1, 5, and 10 wt %. The microcrystalline parameters such as the nanocrystal size (〈N〉), lattice strain (g), interplanar distance (dhkl), width of the crystallite size distribution, surface weighted crystal size (Ds), and volume of the ordered regions were calculated from the X-ray data by using two mathematical models, namely the Exponential distribution and Reinhold distribution methods. The effects of heat ageing on the microcrystalline parameters of the PAni/c-MWNT nanocomposites were also studied and the results are correlated. The thermal stability and electrical resistivity of the PAni/c-MWNT nanocomposites were examined with thermogravimetric analysis (TGA) and a conventional two-probe method. The TGA data indicate that the thermal stability of the nanocomposites improved after the incorporation of c-MWNTs. The influence of temperature on the resistivity of the nanocomposites was also measured. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献
84.
The swelling kinetics curves of structurally defined poly(acrylic acid) hydrogel in bidistilled water at temperatures: 25, 30, 35, 40, and 45°C were determined. The possibility of kinetically explaining the isothermal swelling process by applying the following models: reaction controlled by diffusion, first order chemical reaction kinetics, and second order chemical reaction kinetics, was investigated. It was found that kinetically explaining the swelling process using these methods was limited to only certain parts of the process. The swelling process in bidistilled water was described in full range assuming that the hydrogel's swelling rate was a kinetically controlled reaction by the rate of the movement of reactive interface of hydrogel. Based on that model, the kinetic parameters, activation energy (Ea) and preexponential factor (A), of the swelling process were determined to be Ea = 35 kJ/mol and lnA = 8.6. A possible mechanism of the investigated swelling process was discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
85.
文章较系统地论述了车铣复合机床设计方案的形成过程,同时分析了该设计方案的持点,并简要介绍了该产品的主要技术参数和用途,简评了该产品的技术水平。 相似文献
86.
厅堂音质评价参量的相关性分析 总被引:2,自引:1,他引:1
当代室内声学专家经常选用的评价厅堂音质的物理参量,其间有几个量是相关的。作为室内音质设计的依据.必须寻找基本相互独立的参量,才有更大的实用意义。 相似文献
87.
多面体含能材料的爆速和爆压预估 总被引:2,自引:2,他引:0
当采用R-P经验方法预估多硝基笼状化合物最大理论密度下爆速和爆压时,需要修正F因子中与分子结构有关的A/3项,使F因子包含有来自笼状分子高晶体密度和分子内部高张力能的贡献。与K-J方法相比,改进R-P方法既保持了原式的优点,又使预估结果获得明显改善。把K-J方法预估结果作为基础数据,利用改进R-P方法估算25种多硝基笼状化合物的爆速和爆压,结果表明该方法的相对误差分别为±1.9%和±5.2%。而用R-P方法时,预估爆速和爆压的相对误差分别为±14.0%和±21.4%。 相似文献
88.
A test chamber has been developed in order to provide a small and simple emission testing facility capable of testing construction products in a climate where the important climatic parameters such as temperature, ventilation rate and air velocity can be varied independently around typical indoor values. The test chamber CLIMPAQ is made of panes of window glass. Other main surface materials are stainless steel and eloxated aluminium. The chamber has a volume of 50.9 litres and is designed to meet the requirements for quantifying air pollution. In this investigation human subjects acted as air pollution judges, and chemical characterization of the air pollution was carried out. Carpet, linoleum, wall paint and seal- ant were tested simultaneously in the CLIMPAQ and in four other chambers ranging from a full-scale chamber of 28 m3 to a field and laboratory emission cell of 3.5· 10?5m3. Product ranking is the same in all chambers for the sensory measurements. Emission rates based on sensory measurements differ for all products less than 100 % except for tests in a 3-litre chamber where emission rates were higher. Chemical measurements differ up to approximately 10 times for the same product in different chambers. Deviations appear to be the result of different environmental parameters in the various chambers. Low air concentrations or high specific ventilation rates seem to increase emissions, while differences in air velocities and sink properties may also be the cause of differences in emission rates. 相似文献
89.
水工自密实混凝土的设计及应用 总被引:2,自引:0,他引:2
自密实混凝土具有高流态、免振等特性,适用于体形复杂、钢筋密集等难以浇筑的特殊部位。介绍了水工自密实混凝土的设计要求、思路及配合比参数选定方法。以三峡二期工程左岸厂房坝段压力钢管外包混凝土为例,给出了水工自密实混凝土的具体设计及应用。该项技术具有较好的推广应用前景。 相似文献
90.
气门用4Cr9Si2钢调质工艺研究 总被引:1,自引:0,他引:1
采用正交试验 ,研究了 4Cr9Si2钢的淬火温度、回火温度与组织、硬度间的关系 ,得出了最佳的工艺参数 (10 10℃淬火 ,6 0 0℃回火 )。实际生产表明 ,采用此工艺后 ,断裂现象基本消除 ,气门的热处理质量有了明显提高。 相似文献