全文获取类型
收费全文 | 69779篇 |
免费 | 7813篇 |
国内免费 | 2896篇 |
专业分类
电工技术 | 3780篇 |
综合类 | 5236篇 |
化学工业 | 15509篇 |
金属工艺 | 6669篇 |
机械仪表 | 3353篇 |
建筑科学 | 6313篇 |
矿业工程 | 1363篇 |
能源动力 | 9577篇 |
轻工业 | 4686篇 |
水利工程 | 555篇 |
石油天然气 | 3293篇 |
武器工业 | 975篇 |
无线电 | 3755篇 |
一般工业技术 | 8216篇 |
冶金工业 | 4053篇 |
原子能技术 | 1269篇 |
自动化技术 | 1886篇 |
出版年
2024年 | 250篇 |
2023年 | 1074篇 |
2022年 | 1886篇 |
2021年 | 2327篇 |
2020年 | 2351篇 |
2019年 | 1975篇 |
2018年 | 1790篇 |
2017年 | 2132篇 |
2016年 | 2488篇 |
2015年 | 2412篇 |
2014年 | 4156篇 |
2013年 | 4251篇 |
2012年 | 4853篇 |
2011年 | 5080篇 |
2010年 | 3866篇 |
2009年 | 3911篇 |
2008年 | 3183篇 |
2007年 | 4391篇 |
2006年 | 4115篇 |
2005年 | 3596篇 |
2004年 | 3199篇 |
2003年 | 2821篇 |
2002年 | 2643篇 |
2001年 | 2120篇 |
2000年 | 1800篇 |
1999年 | 1408篇 |
1998年 | 1122篇 |
1997年 | 1008篇 |
1996年 | 793篇 |
1995年 | 671篇 |
1994年 | 579篇 |
1993年 | 454篇 |
1992年 | 400篇 |
1991年 | 257篇 |
1990年 | 217篇 |
1989年 | 199篇 |
1988年 | 130篇 |
1987年 | 101篇 |
1986年 | 71篇 |
1985年 | 63篇 |
1984年 | 84篇 |
1983年 | 64篇 |
1982年 | 69篇 |
1981年 | 18篇 |
1980年 | 20篇 |
1979年 | 13篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1959年 | 28篇 |
1951年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
建立垂直管吸收器管内泡式吸收过程中传热传质的数学物理模型,对其泡式吸收过程进行数值研究,获得泡式吸收方式的一些传热传质特性,为吸收器的优化设计提供一定理论指导。 相似文献
112.
113.
114.
Titanium Dioxide, TiO2, is a photocatalyst with a unique characteristic. A surface coated with TiO2 exhibits an extremely high affinity for water when exposed to UV light and the contact angle decreases nearly to zero. Inversely, the contact angle increases when the surface is shielded from UV. This superhydrophilic nature gives a self-cleaning effect to the coated surface and has already been applied to some construction materials, car coatings and so on. We applied this property to the enhancement of boiling heat transfer. An experiment involving the pool boiling of pure water has been performed to make clear the effect of high wettability on heat transfer characteristics. The heat transfer surface is a vertical copper cylinder of 17 mm in diameter and the measurement has been done at saturated temperature and in a steady state. Both TiO2-coated and non-coated surfaces were used for comparison. In the case of the TiO2-coated surface, it is exposed to UV light for a few hours before experiment and it is found that the maximum heat flux (CHF) is about two times larger than that of the uncoated surface. The temperature at minimum heat flux (MHF) for the superhydrophilic surface is higher by 100 K than that for the normal one. The superhydrophilic surface can be an ideal heat transfer surface. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
115.
116.
新型保温材料—炭化稻壳在连铸生产中的应用效果 总被引:3,自引:0,他引:3
对新型保温材料──炭化稻壳的理化指标及其保温性能进行了阐述。在连铸生产中采用炭化稻壳做保温剂可取得显著的经济效益,是理想的保温材料。 相似文献
117.
118.
本文对八种新型功能晶体Li2B4O7、Bi12TiO20、Bi12GeO20、Bi12GeO20、Bi4Ge3O12、Sr1-xBaxNb2O6(x=0.33,0.48)、LiTaO3等在130~973K范围内的比热行为及其与相变、组分之间的关系进行了实验研究,给出了比热的多项式拟合方程,并与用纽曼-卡普定律及用Wikelmann经验方程的比热计算值作了对比,为晶体比热的估算提供了依据和方法。 相似文献
119.
Huai Wen-xin Wuhan University of Hydraulic & Electric Engineering Wuhan Hubei P.R.China Prof.Li Wei 《水动力学研究与进展(B辑)》1993,(3)
Turbulence represents an essential aspect in atmospheric and oceanic circulations.In particu-lar,it is a preponderant factor in the dispersion of pollutants of artificial or natural origin.Thevertical turbulent jets,plumes and buoyant jets discharging into static environment is one of themost important and basic flow patterns related with the environment pollution.These flows havenumerous important applications,for example,thrust augmentors,waste disposal plumes fromstacks and combustion systems,and significant problems of turbulent diffusion. 相似文献
120.
This paper presents a new computerized procedure for dealing with the design of horizontal ground heat exchangers (HGHE). The computer program is based on the transient model of coupled nonlinear partial differential equations governing heat and mass flow in soils. The model is two-dimensional and delineates the operation of ground heat storage with the HGHE and such phenomena as freezing/thawing and drying/rewetting of soil moisture. Comprehensive climatological data, such as ambient temperature, solar radiation, wind velocity, rainfall, snowfall, snow characterstics, and water vapour pressure is used to simulate conditions at the ground surface over any required length of time. The package can be applied to any geographical location by changing climatic and soil data input. The designer has the possibility of selecting any of 12 types of soils from sand to clay, 12 commercial heat pumps, nine different configurations of the HGHE, 16 plastic pipes for ground coils, and 13 ground coil fluids. The program, however, does not calculate the length of the HGHE but it evaluates the thermodynamic performance of a ground heat pump system and provides comprehensive data on thermal and hydraulic conditions in ground heat storage. The length of the ground heat exchanger is obtained from a line source theory model or from site dimensions and pipe spacing. Computed results for ground heat exchanger operation correlate fairly well with experimental data. Simulation of temperature and moisture content in the ground for natural conditions (no heat extraction/deposition) showed a fair agreement with field data. The entire computer program is user-friendly, interactive, menu-driven, and written in FORTRAN 77. 相似文献