全文获取类型
收费全文 | 48184篇 |
免费 | 5885篇 |
国内免费 | 4089篇 |
专业分类
电工技术 | 3313篇 |
综合类 | 3728篇 |
化学工业 | 7883篇 |
金属工艺 | 2007篇 |
机械仪表 | 3183篇 |
建筑科学 | 929篇 |
矿业工程 | 645篇 |
能源动力 | 1365篇 |
轻工业 | 3377篇 |
水利工程 | 251篇 |
石油天然气 | 1255篇 |
武器工业 | 663篇 |
无线电 | 12459篇 |
一般工业技术 | 6591篇 |
冶金工业 | 843篇 |
原子能技术 | 648篇 |
自动化技术 | 9018篇 |
出版年
2024年 | 192篇 |
2023年 | 693篇 |
2022年 | 1062篇 |
2021年 | 1384篇 |
2020年 | 1482篇 |
2019年 | 1398篇 |
2018年 | 1366篇 |
2017年 | 1705篇 |
2016年 | 1929篇 |
2015年 | 2054篇 |
2014年 | 2858篇 |
2013年 | 3122篇 |
2012年 | 3525篇 |
2011年 | 4149篇 |
2010年 | 2993篇 |
2009年 | 3179篇 |
2008年 | 3320篇 |
2007年 | 3593篇 |
2006年 | 2974篇 |
2005年 | 2513篇 |
2004年 | 2150篇 |
2003年 | 1907篇 |
2002年 | 1509篇 |
2001年 | 1232篇 |
2000年 | 1028篇 |
1999年 | 833篇 |
1998年 | 735篇 |
1997年 | 560篇 |
1996年 | 488篇 |
1995年 | 379篇 |
1994年 | 376篇 |
1993年 | 267篇 |
1992年 | 259篇 |
1991年 | 200篇 |
1990年 | 152篇 |
1989年 | 123篇 |
1988年 | 69篇 |
1987年 | 56篇 |
1986年 | 38篇 |
1985年 | 65篇 |
1984年 | 59篇 |
1983年 | 40篇 |
1982年 | 38篇 |
1981年 | 26篇 |
1980年 | 17篇 |
1979年 | 9篇 |
1978年 | 11篇 |
1976年 | 14篇 |
1975年 | 10篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Didier SBILLEAU 《核技术(英文版)》2003,14(1)
We present here a general overview of electron spectroscopies from a practical point of view. The most frequently used ones are described and the type of structural information they can provide on materials is explained in relation to the physical processes on which they are based. Furthermore, we explore critically and in detail various tools that have been developed to allow a systematic solving of structures by these spectroscopies. 相似文献
82.
The reversible persistent changes of the fill factor (FF) induced by the illumination and voltage bias along with changes in the electronic properties of the ZnO/CdS/Cu(In,Ga)Se2 photovoltaic devices have been studied. Admittance spectroscopy and capacitance–voltage characterization reveal a correlation between the FF and the space charge distribution within the absorber. Our experiments provide evidence that a major source of FF loss in efficient devices is caused by excess negative charge close to the interface. We explain the persistent changes in the net acceptor concentration in the interface region by the relaxation effects due to compensating donors—the same mechanism, which leads to metastable changes of the doping level in the bulk of the absorber. 相似文献
83.
84.
Evaggelia D. Tzika Vassiliki Papadimitriou Theodore G. Sotiroudis Aristotelis Xenakis 《European Journal of Lipid Science and Technology》2008,110(2):149-157
The autoxidation at alkaline pH and enzymatic oxidation by mushroom tyrosinase of oleuropein, the dominant biophenol present in the fruits and leaves of Olea europea, was followed by both electron paramagnetic resonance (EPR) and absorption spectroscopy. For comparison, the same oxidation processes were applied to 4‐methylcatechol, a simple polyphenol present in olive mill wastewaters. EPR spectra of stable o‐semiquinone radicals produced during autoxidation at pH 12 and short‐lived o‐semiquinone free radicals produced during autoxidation at pH 9.0 or tyrosinase action and stabilized by chelation with a diamagnetic metal ion (Mg2+) were recorded for both polyphenols, and the corresponding hyperfine splitting constants were determined. The UV‐Vis spectral characteristics of the oxidation of polyphenols were highly dependent on the type of polyphenol, oxidant type and the pH of the reaction. The kinetic behavior of tyrosinase in the presence of oleuropein and 4‐methylcatechol was followed by recording spectral changes at 400 nm (absorption maximum) over time. The tysosinase activity with oleuropein showed a pronounced pH optimum at pH 6.5 and a minor one around pH 8. From the data analysis of the initial rate at pH 6.5, the kinetic parameters Km = 0.34 ± 0.03 mM and Vmax = 0.029 ± 0.002 ΔA400 min–1 were determined for oleuropein. 相似文献
85.
在不同反应温度条件下采用原位聚合法在石英基片上制备了聚苯胺薄膜.对薄膜样品进行了紫外光谱、SEM、电性能表征。实验结果表明,过高的合成温度会加速聚合反应过程,抑制膜厚的增长,引起薄膜的热降解,进而对样品的导电性产生不良影响。根据生长速率与合成温度的依赖关系,估算了聚合反应的活化能Ea=34.4kJ/mol。 相似文献
86.
炉顶红外摄像装置在新钢6号高炉上的安装及应用 总被引:2,自引:0,他引:2
阐述了高炉炉顶红外摄像装置的安装及应用。该装置对及时了解和掌握高炉炉喉的料面情况、煤气流的分布状况,对指导高炉操作、维护炉况顺行和稳定,改善各项技经指标,发挥了重要作用。 相似文献
87.
本文将用数学和实验两种方法证实MC~2电缆不仅能保证特性阻抗变化不超出电缆技术规范。而且能保证在设计频率范围内电缆结构反射损耗最小。 相似文献
88.
89.
The condition of the surfaces is of crucial importance for the deuterium permeation through materials. In this work a study of the surface constants for the adsorption (σk1) and release (σk2) of deuterium under different surface conditions on the martensitic steel DIN 1.4914 (MANET) has been carried out. The growth of an oxide surface layer (Cr2O3) of about 25–30 nm in a MANET sample, heat treated in an oxidizing environment, compared to the bare MANET that have a ‘natural' oxide of about 5 nm has provoked a reduction of both the permeation rate and the recombination coefficient (about 3 orders of magnitude). In addition, the permeation governing process has changed from diffusion-limited to surface-limited. The measurements of the permeation rate of deuterium were performed by a gas-phase permeation technique over the temperature range 574–746 K and for deuterium driving pressures in the range from 3 to 105 Pa. 相似文献
90.
我国炼油技术开发的若干思考与建议 总被引:12,自引:4,他引:8
分析了我国炼油工业面临的挑战,世界炼油工业的发展趋势,提出了我国炼油技术开发要围绕符合国情的清洁燃料生产技术,炼油与化工结合的炼油技术,适合现有炼油装置技术改造、提高技术水平,降低加工成本的技术,渣油转化技术,煤制油,天然气制油技术,炼油厂智能化的技术,减少炼油厂烟尘排放的技术等7个方面开展工作的具体建议。 相似文献