全文获取类型
收费全文 | 509437篇 |
免费 | 90493篇 |
国内免费 | 54957篇 |
专业分类
电工技术 | 44525篇 |
技术理论 | 58篇 |
综合类 | 39210篇 |
化学工业 | 79236篇 |
金属工艺 | 40792篇 |
机械仪表 | 27653篇 |
建筑科学 | 37970篇 |
矿业工程 | 23424篇 |
能源动力 | 17833篇 |
轻工业 | 38966篇 |
水利工程 | 12642篇 |
石油天然气 | 33733篇 |
武器工业 | 6212篇 |
无线电 | 64598篇 |
一般工业技术 | 68494篇 |
冶金工业 | 24951篇 |
原子能技术 | 4528篇 |
自动化技术 | 90062篇 |
出版年
2024年 | 3746篇 |
2023年 | 9213篇 |
2022年 | 13382篇 |
2021年 | 17603篇 |
2020年 | 17945篇 |
2019年 | 25144篇 |
2018年 | 27897篇 |
2017年 | 29907篇 |
2016年 | 28832篇 |
2015年 | 30723篇 |
2014年 | 33106篇 |
2013年 | 35659篇 |
2012年 | 35869篇 |
2011年 | 34749篇 |
2010年 | 30385篇 |
2009年 | 26544篇 |
2008年 | 24567篇 |
2007年 | 23301篇 |
2006年 | 23476篇 |
2005年 | 20981篇 |
2004年 | 17597篇 |
2003年 | 15165篇 |
2002年 | 13869篇 |
2001年 | 12521篇 |
2000年 | 12701篇 |
1999年 | 13981篇 |
1998年 | 12070篇 |
1997年 | 10290篇 |
1996年 | 9720篇 |
1995年 | 8661篇 |
1994年 | 7155篇 |
1993年 | 5667篇 |
1992年 | 4941篇 |
1991年 | 3749篇 |
1990年 | 2927篇 |
1989年 | 2583篇 |
1988年 | 2074篇 |
1987年 | 1004篇 |
1986年 | 801篇 |
1985年 | 535篇 |
1984年 | 381篇 |
1983年 | 293篇 |
1982年 | 336篇 |
1981年 | 264篇 |
1980年 | 215篇 |
1976年 | 280篇 |
1975年 | 223篇 |
1972年 | 248篇 |
1971年 | 137篇 |
1960年 | 206篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
In connection with the specific features of high velocity aerated flow generated by hydraulic engineering structures, the mathematical model is developed for high turbulence air-water two-phase flow with the use of twin flow theoretical model in this paper. Furthermore the numerical method is proposed to treat bubbled flows. In addition, on the basis of air-water stratified twin flow model, the new calculation methods and free surface tracking technique are proposed to describe complicated movements of the free surface. Finally, the proposed model is used to calculate artificial aerated flows. The computed results coincide quite well with experimental results. This means that the proposed method can provide solid basis for practical engineering design. 相似文献
992.
Vincenzo Augelli Teresa Ligonzo Roberto Murri Luigi Schiavulli 《Thin solid films》1989,170(2):163-170
Hydrogenated and chlorinated silicon films were used to deposit Schottky barrier solar cells. Photovoltaic characterization, together with the results of electronic transport measurements, led to the conclusion that the presence of chlorine is detrimental to the properties of this kind of device. 相似文献
993.
Sidhartha R. Das Basheer M. Khumawala 《International Journal of Flexible Manufacturing Systems》1991,3(2):121-147
Flexible manufacturing systems (FMSs) are a class of automated systems that can be used to improve productivity in batch manufacturing. Four stages of decision making have been defined for an FMS—the design, planning, scheduling, and control stages. This research focuses on the planning stage, and specifically in the area of scheduling batches of parts through the system.The literature to date on the FMS planning stage has mostly focused on the machine grouping, tool loading, and parttype selection problems. Our research carries the literature a step further by addressing the problem of scheduling batches of parts. Due to the use of serial-access material-handling systems in many FMSs, the batch-scheduling problem is modeled for a flexible flow system (FFS). This model explicitly accounts for setup times between batches that are dependent on their processing sequence.A heuristic procedure is developed for this batch-scheduling problem—the Maximum Savings (MS) heuristic. The MS heuristic is based upon the savings in time associated with a particular sequence and selecting the one with the maximum savings. It uses a two-phase method, with the savings being calculated in phase I, while a branch-and-bound procedure is employed to seek the best heuristic solution in phase II. Extensive computational results are provided for a wide variety of problems. The results show that the MS heuristic provides good-quality solutions. 相似文献
994.
Zinc-containing nanoparticles stable in the liquid phase are synthesized by the radiation chemical reduction of zinc ions
in solutions of inverse micelles. The effects of the absorbed radiation dose and the size of the micelle water pool on the
spectral characteristics of samples are studied. The HPLC and electron microscopy results indicate that the composition of
nanoparticles synthesized depends on the salt nature.
Original Russian Text ? A.A. Revina, E.V. Oksentyuk, A.A. Fenin, 2007, published in Zashchita Metallov, 2007, Vol. 43, No.
6, pp. 613–618. 相似文献
995.
Ma Weidong Liu Wen Wenmin Wang Luo Yong Bu Qinlian Xiouli Zhao Jiang Shan Li Wei 《Photonics Technology Letters, IEEE》2007,19(15):1115-1117
An athermal 40-channel dense wavelength-division-multiplexing multi/demultiplexer using a novel combination technology is proposed. It consists of one 1times4 100- to 400-GHz spacing interleaver filter and four sub-arrayed-waveguide gratings (AWGs). The temperature-dependent wavelength shift of the combined device is successfully suppressed to 0.058 nm in the -20degC to 70degC temperature range. Moreover, the combined device's adjacent crosstalk (typically -35 dB) is much better than conventional AWGs (typically -25 dB). 相似文献
996.
Li Yonghua Wang Chunbo Chen Hongwei 《Frontiers of Energy and Power Engineering in China》2007,1(1):96-100
Power plants in China have to burn blended coal instead of one specific coal for a variety of reasons. So it is of great necessity
to investigate the combustion of blended coals. Using a test rig with a capacity of 640 MJ/h with an absolute milling system
and flue gas online analysis system, characteristics such as burnout, slag, and pollution of some blended coals were investigated.
The ratio of coke and slag as a method of distinguishing coal slagging characteristic was introduced. The results show that
the blending of coal has some effect on NO
x
but there is no obvious rule. SO
x
emission can be reduced by blending low sulfur coal.
Translated from Proceedings of the CSEE, 2005, 25(18): 97–103 [译自: 中国电机工程学报] 相似文献
997.
998.
Haiying Wang 《Materials Research Bulletin》2005,40(6):911-919
Eu3+-doped Y2O3, YOF, La2O3, LaOF hollow spheres have been synthesized by a facile template route. Eu3+ were doped into the various host materials to make the hollow sphere red-luminescent. Difference in fluorescence spectra recorded on the hollow spheres were compared in detail and attributed to the different crystal symmetry of host materials. These phosphors might find applications in the fields such as light phosphor powders, advanced flat panel display, or biological labeling. 相似文献
999.
1000.