全文获取类型
收费全文 | 23293篇 |
免费 | 795篇 |
国内免费 | 85篇 |
专业分类
电工技术 | 299篇 |
综合类 | 45篇 |
化学工业 | 5169篇 |
金属工艺 | 506篇 |
机械仪表 | 468篇 |
建筑科学 | 1747篇 |
矿业工程 | 161篇 |
能源动力 | 692篇 |
轻工业 | 2159篇 |
水利工程 | 183篇 |
石油天然气 | 57篇 |
武器工业 | 1篇 |
无线电 | 1503篇 |
一般工业技术 | 4252篇 |
冶金工业 | 2906篇 |
原子能技术 | 147篇 |
自动化技术 | 3878篇 |
出版年
2023年 | 152篇 |
2022年 | 310篇 |
2021年 | 536篇 |
2020年 | 313篇 |
2019年 | 328篇 |
2018年 | 497篇 |
2017年 | 429篇 |
2016年 | 533篇 |
2015年 | 483篇 |
2014年 | 696篇 |
2013年 | 1538篇 |
2012年 | 1088篇 |
2011年 | 1532篇 |
2010年 | 1106篇 |
2009年 | 1062篇 |
2008年 | 1277篇 |
2007年 | 1117篇 |
2006年 | 951篇 |
2005年 | 874篇 |
2004年 | 786篇 |
2003年 | 699篇 |
2002年 | 675篇 |
2001年 | 400篇 |
2000年 | 387篇 |
1999年 | 424篇 |
1998年 | 451篇 |
1997年 | 389篇 |
1996年 | 356篇 |
1995年 | 309篇 |
1994年 | 306篇 |
1993年 | 308篇 |
1992年 | 255篇 |
1991年 | 222篇 |
1990年 | 207篇 |
1989年 | 232篇 |
1988年 | 190篇 |
1987年 | 180篇 |
1986年 | 175篇 |
1985年 | 244篇 |
1984年 | 216篇 |
1983年 | 186篇 |
1982年 | 172篇 |
1981年 | 201篇 |
1980年 | 130篇 |
1979年 | 147篇 |
1978年 | 146篇 |
1977年 | 132篇 |
1976年 | 147篇 |
1975年 | 122篇 |
1974年 | 111篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Jens‐Peter Heinß Dr. 《真空研究与实践》2007,19(5):20-23
Hydrogen free amorphous carbon coatings ‐ deposited with plasma‐activated high‐rate evaporation By using the technology of the plasmaactivated electron beam evaporation we deposited hydrogen free amorphous carbon coatings with deposition rates of up to 100 μm/h. The results of the mechanical and tribological investigations show the potential of these layers for the use in case of wear resistance. Hardnesses of up to 16GPa were proved. The actual state of the characterisation of the coatings is described and the outlook onto possibilities of further optimisation is given. 相似文献
33.
随着移动电视在美国的开始应用,新应用逐渐站稳了脚跟,并被美国消费者的要求所推动,而消费者的这些更丰富体验的要求在以前受到过抑制。为了在卫星电信领域更好契合这一趋势,注意亚洲发展并从其经验中总结教训这一做法是有意义的。 相似文献
34.
Rogier Schonenborg Adalberto Costessi Peter Schiller 《Microgravity science and technology》2007,19(5-6):219-224
This paper gives a quick overview of how various scientific, operational and safety related requirements drove the development of hardware for the Bone Proteomics (BOP) experiment that was conducted on the International Space Station during the Italian Soyuz Mission in 2005. The experiment objectives will be highlighted briefly and design solutions will be presented. Comments will be given regarding the choice of a particular design solution and the impact on the complexity, cost and development time. Conclusions in this paper are based on the experience gained when developing the BOP experiment hardware and other relatively small experiment hardware packages, typical of European Soyuz Missions. The observations should not be extrapolated to large payloads. The objective of this paper is not to produce a recipe for developing experiment hardware; dedicated documents for that purpose are available elsewhere. Rather, the objective is to help others profit from experience gained in the development of relatively small experiment hardware packages, and to highlight where time and cost saving decisions can be made. 相似文献
35.
The thermal stress on building‐integrated photovoltaic modules (BIPV) in Espoo, Finland, was studied with field‐testing of amorphous silicon modules. Based on these results, the thermal stress at two other European locations (Paris and Lisbon) was estimated. The estimation procedure entailed thermal modelling of heat transfer in the façade with meteorological data as input. The results indicate that the thermal stress on BIPV modules in Lisbon is, in this case, approximately 50% higher that in Espoo and between 80 and 200% higher than in Paris, depending on the activation energy of the degradation process. The difference in stress between a BIPV module and a free‐standing module in Espoo was 50–200%. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
36.
A test chamber has been developed in order to provide a small and simple emission testing facility capable of testing construction products in a climate where the important climatic parameters such as temperature, ventilation rate and air velocity can be varied independently around typical indoor values. The test chamber CLIMPAQ is made of panes of window glass. Other main surface materials are stainless steel and eloxated aluminium. The chamber has a volume of 50.9 litres and is designed to meet the requirements for quantifying air pollution. In this investigation human subjects acted as air pollution judges, and chemical characterization of the air pollution was carried out. Carpet, linoleum, wall paint and seal- ant were tested simultaneously in the CLIMPAQ and in four other chambers ranging from a full-scale chamber of 28 m3 to a field and laboratory emission cell of 3.5· 10?5m3. Product ranking is the same in all chambers for the sensory measurements. Emission rates based on sensory measurements differ for all products less than 100 % except for tests in a 3-litre chamber where emission rates were higher. Chemical measurements differ up to approximately 10 times for the same product in different chambers. Deviations appear to be the result of different environmental parameters in the various chambers. Low air concentrations or high specific ventilation rates seem to increase emissions, while differences in air velocities and sink properties may also be the cause of differences in emission rates. 相似文献
37.
38.
39.
Personal exposure in a displacement ventilated room is examined. The stratified flow and the considerable concentration gradients necessitate an improvement of the widely used fully mixing compartmental approach. The exposure of a seated and a standing person in proportion to the stratification height is examined by means of full-scale measurements. A breathing thermal manikin is used to simulate a person. It is found that the flow in the boundary layer around a person is able to a great extent to entrain and transport air from below the breathing zone. In the case of non-passive, heated contaminant sources, this entrainment improves the indoor air quality. Measurements of exposure due to a passive contaminant source show a significant dependence on the flow field as well as on the contaminant source location. Poor system performance is found in the case of a passive contaminant released in the lower part of the room close to the occupant. A personal exposure model for displacement ventilated rooms is proposed. The model takes the influence of gradients and the human thermal boundary layer into account. Two new quantities describing the interaction between a person and the ventilation are defined. 相似文献
40.
Peter Gregory 《Advanced materials (Deerfield Beach, Fla.)》1996,8(6):463-466
An influential and refreshingly frank report on the state of health of non-university materials research in Germany has recently been published. National Research Centers, Max Planck Institutes, and Fraunhofer Institutes are among the organizations covered. Recommendations are made on the basis of materials type, and on the performances of the individual institutes. The conclusions of this self-portrait, painted by representatives of the organizations themselves along with participants from the universities, industry, and state, will provide food for thought for both German materials scientists and those in other European countries concerned with the future development of this crucial economic sector. 相似文献