全文获取类型
收费全文 | 17647篇 |
免费 | 1837篇 |
国内免费 | 1652篇 |
专业分类
电工技术 | 1393篇 |
技术理论 | 2篇 |
综合类 | 2092篇 |
化学工业 | 1606篇 |
金属工艺 | 2244篇 |
机械仪表 | 1031篇 |
建筑科学 | 1186篇 |
矿业工程 | 860篇 |
能源动力 | 408篇 |
轻工业 | 454篇 |
水利工程 | 300篇 |
石油天然气 | 388篇 |
武器工业 | 176篇 |
无线电 | 1770篇 |
一般工业技术 | 2177篇 |
冶金工业 | 1264篇 |
原子能技术 | 91篇 |
自动化技术 | 3694篇 |
出版年
2024年 | 53篇 |
2023年 | 251篇 |
2022年 | 447篇 |
2021年 | 582篇 |
2020年 | 586篇 |
2019年 | 473篇 |
2018年 | 426篇 |
2017年 | 507篇 |
2016年 | 553篇 |
2015年 | 703篇 |
2014年 | 1214篇 |
2013年 | 1118篇 |
2012年 | 1333篇 |
2011年 | 1439篇 |
2010年 | 1051篇 |
2009年 | 1068篇 |
2008年 | 937篇 |
2007年 | 1204篇 |
2006年 | 1099篇 |
2005年 | 897篇 |
2004年 | 727篇 |
2003年 | 654篇 |
2002年 | 556篇 |
2001年 | 457篇 |
2000年 | 449篇 |
1999年 | 344篇 |
1998年 | 300篇 |
1997年 | 302篇 |
1996年 | 237篇 |
1995年 | 217篇 |
1994年 | 216篇 |
1993年 | 126篇 |
1992年 | 123篇 |
1991年 | 114篇 |
1990年 | 101篇 |
1989年 | 94篇 |
1988年 | 60篇 |
1987年 | 25篇 |
1986年 | 14篇 |
1985年 | 17篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1959年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
将环隙式离心萃取器(ACCs)与电喷雾飞行时间质谱(ESI-TOF-MS)相结合,在线监测了回收过程中的钨萃取行为(宏观)和钨形态的转化路径(微观),发现宏观萃取反应和微观离子形态转化同时发生并相互补充。伯胺N1923萃取钨在144 s内即可达到萃取平衡,萃取率高达98%以上,同时,酸钨比n(H)/n(W)是一个关键变量,当酸钨比n(H)/n(W)=2.4时,全流程钨回收率超过93%。最后,得到了基于钨形态监测的萃取机理,同时,减少原料液中W1含量,增加W10含量,可有效提高钨回收效率。 相似文献
12.
13.
Titania-based ceramics with adjustable anatase-rutile fractions were obtained by milling of anatase, quartz and corundum precursors, uniaxial pressing and firing at 1100?°C. The influence of silica and alumina, combined with milling time and compaction pressure, was studied by design of experiments. The L9 orthogonal array with a three-level noise factor was employed. Firing of pure titania at 1100?°C yielded complete anatase to rutile transformation (ART), whereas stabilized samples show that an optimum amount of 9% silica and 33% alumina reduces phase transformation to only about 5?wt% rutile. An extended correlation matrix combined with analysis of variance (ANOVA) was applied to assess the combined effects of quartz, alumina, milling time and uniaxial compressing pressure on relative density, and anatase to rutile transformation. Results show absence of ART after milling, and controlled partial conversion of anatase to rutile after firing. Very good fitting was obtained by multivariate analysis on considering first and second order terms for dependence on silica contents and interactions between silica and each of the remaining factors, including milling time. This empirical dependence could be interpreted on a sound physicochemical basis, allowing the prediction of suitable compositions and processing conditions to obtain rutile-free samples by conventional ceramic processing, and to design ceramic samples with controlled fractions of anatase and rutile. 相似文献
14.
《Intermetallics》2015
Fine-grained fully-lamellar (FL) microstructure is desired for TiAl components to serve as compressor/turbine blades and turbocharger turbine wheels. This study deals with the process and phase transformation to produce FL microstructure for Mo stabilized beta-gamma TiAl alloys without single α-phase field. Unlike the α + γ two-phased TiAl or beta-gamma TiAl with single α-phase field, the wrought multi-phase TiAl–4/6Nb–2Mo–B/Y alloys exhibit special annealing process to obtain FL microstructure. Short-term annealing at temperatures slightly above β-transus is recommended to produce the desired FL microstructure. The related mechanism is to guarantee the sufficient diffusion homogenization of β stabilizers during single β-phase annealing, and further avoid α decomposition by α → γ + β when cooling through α + β + γ phase field. The colony boundary β phase contributes to fine-grained nearly FL microstructure, by retarding the coarsening of the α phase grains. 相似文献
15.
介绍了一种基于高性能浮点DSP芯片TMS320C32、CPLD芯片XC95288和A/D采样芯片AD976组成的多路采集系统的工作原理以及设计方法。通过对第一路施加特殊的电压量,在CCS开发环境下读取采样缓冲区的值,并利用Matlab对采样数据进行了全波傅氏变换。此外,该系统已在继电保护中得到广泛应用,实践表明,该系统能较好地解决多路模拟量的采集,并确保了采样数据的安全可靠性。 相似文献
16.
The investigation of phase transformations in metastable ceramic systems such as zirconia often requires local phase analysis within the areas of interest. Electron backscatter diffraction is a suitable method in combination with focused ion beam sample preparation. The interaction between ion beam and sample has to be carefully considered. In case of metastable Y-PSZ and Mg-PSZ, phase transformations were observed after FIB preparation with 30?kV, 30?nA and 5° incidence angle. Damage was the dominating effect for angles of 72°. The expected local temperature increase due to the ion bombardment with 30?kV and 30?nA is 700?K for ZrO2. Thus, the observed phase transformations can be explained on the basis of the temperature increase in the corresponding Y-PSZ phase diagram. In case of Mg-PSZ, the transition temperature is 1083?°C. The local temperature increase was obviously lower. The excitation energy for the observed phase transformation was smaller than expected from the phase diagrams of the thermodynamic equilibrium. Using 5?kV, 4.8?nA and 5° incidence angle, no phase transformations and no damage were observed. Thus, these conditions are well suited for the FIB preparation of metastable zirconia. 相似文献
17.
在社会转型期,面对日益激烈的市场竞争环境,如何制定民办高效发战战略,引导民办高效的可持续发展,是关系到民办高校兴衰的关键。本文主要从民办高校品牌战略入手,对社会转型及高等教育转型进行论述,并对如何加强民办高校品牌建设进行探讨。 相似文献
18.
19.
20.