全文获取类型
收费全文 | 74326篇 |
免费 | 6955篇 |
国内免费 | 4273篇 |
专业分类
电工技术 | 5122篇 |
技术理论 | 1篇 |
综合类 | 4364篇 |
化学工业 | 19509篇 |
金属工艺 | 10885篇 |
机械仪表 | 3314篇 |
建筑科学 | 5564篇 |
矿业工程 | 1285篇 |
能源动力 | 4813篇 |
轻工业 | 4132篇 |
水利工程 | 690篇 |
石油天然气 | 2554篇 |
武器工业 | 971篇 |
无线电 | 4992篇 |
一般工业技术 | 11685篇 |
冶金工业 | 3099篇 |
原子能技术 | 937篇 |
自动化技术 | 1637篇 |
出版年
2024年 | 421篇 |
2023年 | 1466篇 |
2022年 | 2242篇 |
2021年 | 2696篇 |
2020年 | 2724篇 |
2019年 | 2433篇 |
2018年 | 2338篇 |
2017年 | 2813篇 |
2016年 | 2677篇 |
2015年 | 2801篇 |
2014年 | 4053篇 |
2013年 | 4528篇 |
2012年 | 4928篇 |
2011年 | 5429篇 |
2010年 | 4064篇 |
2009年 | 4236篇 |
2008年 | 3683篇 |
2007年 | 4622篇 |
2006年 | 4419篇 |
2005年 | 3578篇 |
2004年 | 3100篇 |
2003年 | 2561篇 |
2002年 | 2251篇 |
2001年 | 1949篇 |
2000年 | 1812篇 |
1999年 | 1323篇 |
1998年 | 1151篇 |
1997年 | 949篇 |
1996年 | 789篇 |
1995年 | 638篇 |
1994年 | 488篇 |
1993年 | 436篇 |
1992年 | 413篇 |
1991年 | 319篇 |
1990年 | 257篇 |
1989年 | 225篇 |
1988年 | 154篇 |
1987年 | 98篇 |
1986年 | 106篇 |
1985年 | 82篇 |
1984年 | 71篇 |
1983年 | 57篇 |
1982年 | 52篇 |
1981年 | 32篇 |
1980年 | 27篇 |
1979年 | 8篇 |
1977年 | 9篇 |
1975年 | 7篇 |
1959年 | 8篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
U. Amato G. Amodeo V. Brandi V. Cuomo D. Ruggi C. Serio V. Silvestrini G. C. Tosato 《国际能源研究杂志》1985,9(1):33-51
In Italy solar thermal energy and energy from biogas are two possible means of reducing dependence on energy imports. Using a multiperiod LP model (MARKAL) the authors assessed the likely potential of both technologies under various circumstances. The study covered the period 1980–2005, in five segments of five years. It focused only on the subsystem of the energy end-uses which can be substituted for by solar thermal and biogas technologies. The overall non-renewable sources which can be saved in 20 years by these technologies total 450 PJ (1 PJ = 101 5 J) if the fuel prices rise at 0 per cent average annual, 1450 PJ if the fuel prices rise at 4.2 per cent average annual, 1860 PJ if the fuel prices rise at 7.2 per cent average annual and 3780 PJ if the fuel prices rise at 15 per cent average annual. However the most competitive technologies appear to be solar water heaters used mainly in the private and commercial sectors and biogas systems used mainly in the agricultural sector. The study was carried out by APRE under ENEA (formerly CNEN) contract and was intended to serve as an analytical basis for establishing an overall development and demonstration strategy for end-use renewable technologies in Italy. 相似文献
72.
将Mo与Al2O3粉体按摩尔比为0.3、0.4、0.5配料,混合均匀后通过粉末冶金法制成3种Mo-Al2O3金属陶瓷试样。在1800℃,2h氢气气氛中烧结后,试样的气孔率随Mo含量的增加呈降低趋势,而强度呈增加趋势。同时,随Mo含量增加,金属陶瓷中Al2O3的晶粒尺寸减小,Mo的形态从以弥散状为主转变为以连续状为主。研制的高温型Mo-Al2O3金属陶瓷测温套管(金属与陶瓷摩尔比为0.4)在真空或N2保护条件下测量高温合金熔液温度时,平均使用寿命达到100次。 相似文献
73.
I. N. Ishchuk 《Measurement Techniques》2007,50(10):1081-1086
A three-dimensional solution of the direct problem of heat conduction when a linear pulsed heat source acts in the plane of
contact of two semibounded bodies is presented. The solution is obtained by the method of finite differences. An example of
the modeling is considered.
__________
Translated from Izmeritel’naya Tekhnika, No. 10, pp. 42–45, October, 2007. 相似文献
74.
Dario Pasini Luigi Garlaschelli Elza Bontempi Laura E. Depero 《Fullerenes, Nanotubes and Carbon Nanostructures》2007,15(5):367-378
The synthesis of a series of polymers and cyclopolymers bearing crown ethers of differing structure and affinities towards primary ammonium ions is discussed. These polymers have been tested in their efficiency to form structurally homogeneous thin films when blended with an amphiphilic C60 compound containing a primary ammonium ion functional group. The X-ray reflectivity characterization of the films revealed that the polymer bearing the crown ether with the least affinity for primary ammonium ions, but having the highest degree of polymerization, is the most effective in forming structurally homogeneous thin films. 相似文献
75.
基于高抗热震性能的陶瓷刀具材料的微观结构设计 总被引:1,自引:0,他引:1
本文以现有的抗热震断裂和抗热震损伤的评价理论为基础,通过对材料中微裂纹的长度进行预测,从而实现了对陶瓷刀具材料的抗热震性能的微观结构设计。根据此理论对现有材料的抗热震性能的进行预测,预测结果与实际的测量结果相符,验证了该理论的正确性。 相似文献
76.
A. J. Slifka B. J. Filla 《Journal of research of the National Institute of Standards and Technology》2003,108(2):147-150
An industrial ceramic thermal-barrier coating designated PWA 266, processed by electron-beam physical-vapor deposition, was measured using a steady-state thermal conductivity technique. The thermal conductivity of the mass fraction 7 % yttria-stabilized zirconia coating was measured from 100 °C to 900 °C. Measurements on three thicknesses of coatings, 170 μm, 350 μm, and 510 μm resulted in thermal conductivity in the range from 1.5 W/(m·K) to 1.7 W/(m·K) with a combined relative standard uncertainty of 20 %. The thermal conductivity is not significantly dependent on temperature. 相似文献
77.
78.
本文针对美孚油回收液与兰炼8#油混合利用进行可行性实验研究,经过重度、粘度、可燃性等方面的实验研究,表明美孚油回收液与兰炼8#油混合可以用在电动轮上并且获得良好的效果。 相似文献
79.
A. J. Slifka T. Hall E. S. Boltz 《Journal of research of the National Institute of Standards and Technology》2003,108(2):151-156
A simple measurement system is described for evaluating damage to graphite-epoxy panels, such as those used in high-performance aircraft. The system uses a heating laser and infrared imaging system to measure thermal performance. Thermal conductivity or diffusivity is a sensitive indicator of damage in materials, allowing this thermal measurement to show various degrees of damage in graphite-epoxy composites. Our measurements track well with heat-flux damage to graphite epoxy panels. This measurement system, including analysis software, could easily be used in the field, such as on the deck of an aircraft carrier or at remote air strips. 相似文献
80.
采用先加入絮凝剂脱灰,再经减压蒸馏切割420~500℃馏分的方法,将辽河催化裂化澄清油预处理,考察了澄清油、加入絮凝剂脱灰后的澄清油以及脱灰后再减压蒸馏所得的中间馏分这3种原料在热转化过程中中间相的转化历程,并采用偏光显微镜观察热转化产物。结果表明,澄清油预处理效果明显,所得中间馏分具有较低的H/C原子比(nH/nC)和适宜的组成分布,是生产针状焦的理想原料。热转化产物的光学组织结构属于各向异性发达的广域-流线型结构。 相似文献