全文获取类型
收费全文 | 167762篇 |
免费 | 17608篇 |
国内免费 | 11114篇 |
专业分类
电工技术 | 13092篇 |
技术理论 | 2篇 |
综合类 | 14011篇 |
化学工业 | 22678篇 |
金属工艺 | 10566篇 |
机械仪表 | 10837篇 |
建筑科学 | 12642篇 |
矿业工程 | 4883篇 |
能源动力 | 4539篇 |
轻工业 | 15635篇 |
水利工程 | 4862篇 |
石油天然气 | 6828篇 |
武器工业 | 1810篇 |
无线电 | 20515篇 |
一般工业技术 | 18139篇 |
冶金工业 | 8682篇 |
原子能技术 | 2611篇 |
自动化技术 | 24152篇 |
出版年
2024年 | 890篇 |
2023年 | 2651篇 |
2022年 | 5735篇 |
2021年 | 7595篇 |
2020年 | 5346篇 |
2019年 | 4111篇 |
2018年 | 4469篇 |
2017年 | 5299篇 |
2016年 | 4613篇 |
2015年 | 6877篇 |
2014年 | 8753篇 |
2013年 | 10806篇 |
2012年 | 12494篇 |
2011年 | 13532篇 |
2010年 | 12543篇 |
2009年 | 11779篇 |
2008年 | 12043篇 |
2007年 | 11545篇 |
2006年 | 10446篇 |
2005年 | 8467篇 |
2004年 | 5865篇 |
2003年 | 4389篇 |
2002年 | 4321篇 |
2001年 | 3782篇 |
2000年 | 3287篇 |
1999年 | 2453篇 |
1998年 | 2200篇 |
1997年 | 1787篇 |
1996年 | 1569篇 |
1995年 | 1300篇 |
1994年 | 1012篇 |
1993年 | 860篇 |
1992年 | 661篇 |
1991年 | 508篇 |
1990年 | 436篇 |
1989年 | 365篇 |
1988年 | 279篇 |
1987年 | 206篇 |
1986年 | 176篇 |
1985年 | 156篇 |
1984年 | 105篇 |
1983年 | 83篇 |
1982年 | 79篇 |
1981年 | 78篇 |
1980年 | 79篇 |
1979年 | 52篇 |
1978年 | 34篇 |
1977年 | 75篇 |
1976年 | 135篇 |
1951年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
根据我国煤炭样品制备技术现状和国内外发展趋势,研究开发了自动化控制无人值守煤炭联合制样系统,并从系统制样程序设计、系统整体结构设计、各单元模块设计、系统性能试验等方面对该系统的主要功能及软硬件结构进行介绍,并从称重单元、输送单元、破碎单元、缩分单元、干燥单元、粉碎单元、样品接收包装单元、除尘清洗单元等重点阐述了各单元模块设计,可实现煤样制备全过程无人化、信息化及样品的安全可追溯,其性能试验符合国标GB 474—2008中的相应要求。 相似文献
63.
Mingchang Lin Yufei Zhang Guosong Chen Ming Jiang 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(45):6065-6070
Glyco‐mimicking nanoparticles (glyco‐NPs) with Förster resonance energy transfer (FRET) donor and acceptor groups formed via dynamic covalent bond of benzoboroxole and sugar from two complementary polymers are prepared. The glyco‐NPs are proved to be quite stable under physiological conditions but sensitive to pH. So the glyco‐NPs can be internalized by dendritic cells with integrity and nontoxicity and then dissociate within the acidic organelles. This particle dissociation is directly observed and visualized in vitro, for the first time via the FRET measurements and fluorescent microscopy. This feature makes controlled release of drug or protein by glyco‐NPs possible, i.e., when model antigen Ovalbumin is loaded in the glyco‐NPs, the released Ovalbumin in dendritic cells stimulates T cells more efficiently than the free Ovalbumin itself as a result of the enhanced antigen processing and presentation. Thus, the results enlighten a bright future of the glyco‐NPs in immunotherapy. 相似文献
64.
The identification rate of UHF RFID system was restricted by multipath propagation effects.The system identification performance was studied considering the correlation coefficient between forward and reverse channels.Based on the generalized Rician fading channel model,the analytical expression of identification rate was derived under independent,full correlation and correlation cases.Compared with the existing analysis,the proposed uniform calculation formula of identification rate was for any correlation coefficient and kinds of channel conditions.The numerical computation and Monte-carlo simulations show that the influences of different correlation coefficients,channel conditions,sensitivity and distance on the identification rate. 相似文献
65.
Qun Ren Haijun Su Jun Zhang Haifang Liu Weidan Ma Guangrao Fan Di Zhao Min Guo Lin Liu Hengzhi Fu 《Ceramics International》2019,45(6):6632-6638
Directionally solidified microstructures of Al2O3-Er3Al5O12 eutectic and off-eutectic in situ composite ceramics were explored under abrupt-change pulling rate conditions. Corresponding temperature distributions and interface locations were studied. In eutectic composition, fluctuation of eutectic spacing occurred when the pulling rate increased abruptly. A gradually increase or abrupt increase in eutectic spacing was observed when the pulling rate decreased abruptly. In hypoeutectic and hypereutectic compositions, formation of the primary phases were suppressed when the pulling rate increased abruptly from 10?µm/s to 100?µm/s, while primary phases precipitated when the pulling rate decreased abruptly from 100?µm/s to 10?µm/s. The interface altitude decreased after the pulling rate increased abruptly, but increased after the pulling rate decreased abruptly. The liquid composition restriction (around the eutectic composition) at the eutectic interface plays an important role in the suppression of the primary dendrite and coupled eutectic oxides can be obtained in off-eutectic compositions even under higher solidification rate conditions. 相似文献
66.
Catalytic Hydrocracking of a Bitumen‐Derived Asphaltene over NiMo/γ‐Al2O3 at Various Temperatures 下载免费PDF全文
Hydrocracking of a bitumen‐derived asphaltene over NiMo/γ‐Al2O3 was investigated in a microbatch reactor at varying temperatures. The molar kinetics of asphaltene cracking reaction was examined by fitting the experimental data. Below a defined temperature, the molar reaction showed the first‐order kinetic feature while at higher temperatures secondary reactions such as coke formation became significant, causing deviation of the reaction behavior from the proposed first‐order kinetic model. Selectivity analysis proved that dominant products varied from gases to liquids to gases with increasing temperature, shifting the dominant reaction from C–S bonds cleavage to C–C bonds cleavage. 相似文献
67.
68.
69.
70.