全文获取类型
收费全文 | 326174篇 |
免费 | 4463篇 |
国内免费 | 1091篇 |
专业分类
电工技术 | 6127篇 |
综合类 | 280篇 |
化学工业 | 46429篇 |
金属工艺 | 14659篇 |
机械仪表 | 13184篇 |
建筑科学 | 8137篇 |
矿业工程 | 1323篇 |
能源动力 | 7915篇 |
轻工业 | 29662篇 |
水利工程 | 3231篇 |
石油天然气 | 3384篇 |
武器工业 | 5篇 |
无线电 | 40390篇 |
一般工业技术 | 65759篇 |
冶金工业 | 52303篇 |
原子能技术 | 4480篇 |
自动化技术 | 34460篇 |
出版年
2021年 | 1798篇 |
2020年 | 1347篇 |
2019年 | 1667篇 |
2018年 | 11282篇 |
2017年 | 11953篇 |
2016年 | 7596篇 |
2015年 | 2710篇 |
2014年 | 3740篇 |
2013年 | 12007篇 |
2012年 | 9416篇 |
2011年 | 18165篇 |
2010年 | 15639篇 |
2009年 | 15387篇 |
2008年 | 15557篇 |
2007年 | 17596篇 |
2006年 | 8351篇 |
2005年 | 11218篇 |
2004年 | 9216篇 |
2003年 | 8690篇 |
2002年 | 7231篇 |
2001年 | 7084篇 |
2000年 | 6450篇 |
1999年 | 6837篇 |
1998年 | 16381篇 |
1997年 | 11369篇 |
1996年 | 8595篇 |
1995年 | 6552篇 |
1994年 | 5735篇 |
1993年 | 5590篇 |
1992年 | 4011篇 |
1991年 | 3796篇 |
1990年 | 3548篇 |
1989年 | 3369篇 |
1988年 | 3280篇 |
1987年 | 2589篇 |
1986年 | 2487篇 |
1985年 | 3156篇 |
1984年 | 2797篇 |
1983年 | 2559篇 |
1982年 | 2344篇 |
1981年 | 2390篇 |
1980年 | 2201篇 |
1979年 | 2048篇 |
1978年 | 1879篇 |
1977年 | 2176篇 |
1976年 | 2724篇 |
1975年 | 1584篇 |
1974年 | 1489篇 |
1973年 | 1558篇 |
1972年 | 1144篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
A. V. Kozlov I. A. Portnykh V. I. Pastukhov 《The Physics of Metals and Metallography》2018,119(4):396-401
The influence of the temperature gradient over the thickness of the cladding of a fuel element of a fast-neutron reactor on the migration of point defects formed in the cladding material due to neutron irradiation has been studied. It has been shown that, under the action of the temperature gradient, the flux of vacancies onto the inner surface of the cladding is higher than the flux of interstitial atoms, which leads to the formation of a specific concentration profile in the cladding with a vacancy-depleted zone near the inner surface. The experimental results on the spatial distribution of pores over the cladding thickness have been presented with which the data on the concentration profiles and vacancy fluxes have been compared. 相似文献
102.
The Raman spectrum of water adsorbed on a metallic silver surface reveals an anomalously large shift of the vibrational frequency as compared to that in the bulk. The results are compared to data reported by other researchers, and possible interpretations of the observed phenomenon are discussed. 相似文献
103.
S. A. Pul’nev A. I. Pryadko A. V. Chikiryaka V. I. Nikolaev 《Technical Physics Letters》2018,44(11):992-994
The behavior of a superelastic Cu?14.2% Al?4%Ni single crystal in the case of high reversible strains under a longitudinal bending force was investigated. The effect of strain confinement along the crystal length was revealed and studied. The highest reversible strains (up to 10%) were shown to be confined within the central part of the bent crystal. 相似文献
104.
X-ray diffraction analysis has been used to study the structure of the α-Zr matrix phase and the precipitation of β-Nb particles upon the annealing of a Zr–2.5% Nb deformed alloy. It has been found that the process of the precipitation of the strengthening β-Nb particles in the alloy is accompanied by the appearance of fields of elastic interphase deformations in the matrix α phase of the alloy due to the difference in the specific atomic volumes of the crystal structures of the matrix and precipitated phases. It has been shown experimentally that, as a result of the presence of interphase deformations in the alloy, the bcc crystal structure of the precipitating β-Nb particles undergoes monoclinic distortions. 相似文献
105.
T. Galvin N.C. Hyatt W.M. Rainforth I.M. Reaney D. Shepherd 《Journal of the European Ceramic Society》2018,38(14):4585-4589
The molten salt method was used to synthesise the MAX phase compounds Ti2AlC and Ti3AlC2 from elemental powders. Between 900–1000?°C, Ti2AlC was formed alongside ancillary phases TiC and TiAl, which decreased in abundance with increasing synthesis temperature. Changing the stoichiometry and increasing the synthesis temperature to 1300?°C resulted in formation of Ti3AlC2 alongside Ti2AlC and TiC. The type of salt flux used had little effect on the product formation. The reaction pathway for Ti2AlC was determined to be the initial formation of TiC1-x templating on the graphite and titanium aluminides. 相似文献
106.
107.
The cracks in the workpiece specimens can reduce the fatigue life of any machine components. Since the residual stress has a considerable amount of influence on determining crack formation over the machined surface, it is very essential to analyze the residual stress developed in any machining process. However, it is a very tedious process to compute the residual stress over the machined surface. In the present study, an endeavor has been made to measure and analyze the residual stress of machined silicon steel as a workpiece using the EDM process with different energy distribution. The nano-indentation method was used to compute the residual stress produced over the machined surface. From the experimental results, it was found that the uniform energy distribution has produced higher compressive residual stress owing to the tiny and uniform spark energy distribution. It has also been observed that the tool electrode has a considerable amount of influence on determining development of residual stress in the EDM process. 相似文献
108.
S.K. Vimala Bharathi M. Maria Leena J.A. Moses C. Anandharamakrishnan 《International Journal of Food Science & Technology》2020,55(3):1238-1245
The usage of cling wraps is emerging as an easy and cost-effective approach to protect fresh-cut fruits and vegetables from dust, whilst improving visual appeal on retail counters. This study focused on developing an alternate, protein-based packaging material as a food grade cling wrap for food packaging applications. Zein-based cling wraps were produced, and their physical and mechanical characteristics were evaluated and compared with conventionally used chitosan biopolymer films and commercial synthetic polymer films. Antioxidant potential of the prepared films was studied, and the effectiveness of the developed films as anti-browning cling wraps was evaluated using studies conducted on fresh-cut apple slices at ambient conditions. Anti-browning effects were in par with polymeric counterparts; however, zein cling wraps could better prevent weight loss in apple slices. Zein-based films can be adopted as biodegradable food grade cling wraps as an alternative to chitosan and synthetic polymeric materials. 相似文献
109.
110.