全文获取类型
收费全文 | 1399篇 |
免费 | 18篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 11篇 |
化学工业 | 277篇 |
金属工艺 | 55篇 |
机械仪表 | 36篇 |
建筑科学 | 109篇 |
矿业工程 | 2篇 |
能源动力 | 67篇 |
轻工业 | 197篇 |
水利工程 | 5篇 |
石油天然气 | 5篇 |
无线电 | 67篇 |
一般工业技术 | 282篇 |
冶金工业 | 72篇 |
原子能技术 | 20篇 |
自动化技术 | 214篇 |
出版年
2024年 | 5篇 |
2023年 | 7篇 |
2022年 | 16篇 |
2021年 | 28篇 |
2020年 | 24篇 |
2019年 | 21篇 |
2018年 | 17篇 |
2017年 | 33篇 |
2016年 | 30篇 |
2015年 | 30篇 |
2014年 | 39篇 |
2013年 | 81篇 |
2012年 | 59篇 |
2011年 | 98篇 |
2010年 | 60篇 |
2009年 | 78篇 |
2008年 | 88篇 |
2007年 | 83篇 |
2006年 | 56篇 |
2005年 | 54篇 |
2004年 | 51篇 |
2003年 | 43篇 |
2002年 | 45篇 |
2001年 | 28篇 |
2000年 | 20篇 |
1999年 | 15篇 |
1998年 | 32篇 |
1997年 | 26篇 |
1996年 | 21篇 |
1995年 | 15篇 |
1994年 | 13篇 |
1993年 | 13篇 |
1992年 | 9篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 12篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 14篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1976年 | 8篇 |
1974年 | 7篇 |
1972年 | 4篇 |
排序方式: 共有1419条查询结果,搜索用时 15 毫秒
21.
Using a GIS system in mapping risks of nitrate leaching and erosion on the basis of SOIL/SOIL-N and USLE simulations 总被引:1,自引:0,他引:1
An assessment system that combines digital information on soil types, climates, slopes and crops with simulated values of nitrate leaching and erosion within a geographical information system was developed. The system was used for assessing risks of nitrate leaching and erosion on the regional as well as national scale, having municipalities as the level of aggregation. In Denmark the system has been used for assessing risks of erosion at a catchment scale. 相似文献
22.
23.
24.
Herland A Björk P Hania PR Scheblykin IG Inganäs O 《Small (Weinheim an der Bergstrasse, Germany)》2007,3(2):318-325
The amyloid-like fibril is a biomolecular nanowire template of very high stability. Here we describe the coordination of a conjugated polyelectrolyte, poly(thiophene acetic acid) (PTAA), to bovine insulin fibrils with widths of <10 nm and lengths of up to more than 10 microm. Fibrils complexed with PTAA are aligned on surfaces through molecular combing and transfer printing. Single-molecule spectroscopy techniques are applied to chart spectral variation in the emission of these wires. When these results are combined with analysis of the polarization of the emitted light, we can conclude that the polymer chains are preferentially aligned along the fibrillar axis. 相似文献
25.
26.
Gjerde H Normann PT Christophersen AS Samuelsen SO Mørland J 《Accident; analysis and prevention》2011,(3):1197-1203
A case–control study was conducted on 204 drivers fatally injured in road traffic accidents in south-eastern Norway during the period 2003–2008. Cases from single vehicle accidents (N = 68) were assessed separately. As controls, 10 540 drivers selected in a roadside survey in the same geographical area during 2005–2006 were used. Blood samples were collected from the cases and oral fluid (saliva) samples from the controls. Samples were analysed for alcohol, amphetamines, cannabis, cocaine, opioid analgesics, hypnotics, sedatives and a muscle relaxant; altogether 22 psychoactive substances. Equivalent cutoff concentrations for blood and oral fluid were used. The risk for fatal injury in a road traffic accident was estimated using logistic regression adjusting for gender, age, season of the year, and time of the week. The odds for involvement in fatal road traffic accidents for different substances or combination of substances were in increasing order: single drug < multiple drugs < alcohol only < alcohol + drugs. For single substance use: medicinal drug or THC < amphetamine/methamphetamine < alcohol. For most substances, higher ORs were found when studying drivers involved in single vehicle accidents than for those involved in multiple vehicle accidents, but confidence intervals were wider. 相似文献
27.
Light absorbing objects embedded in silicone have been imaged using photoacoustic digital holography. The photoacoustic waves were generated using a pulsed Nd:YAG laser, λ=1064 nm, and pulse length=12 ns. When the waves reached the silicone surface, they were measured optically along a line using a scanning laser vibrometer. The acoustic waves were then digitally reconstructed using a holographic algorithm. The laser vibrometer is proven to be sensitive enough to measure the surface velocity due to photoacoustic waves generated from laser pulses with a fluence allowed for human tissue. It is also shown that combining digital holographic reconstructions for different acoustic wavelengths provides images with suppressed noise and improved depth resolution. The objects are imaged at a depth of 16.5 mm with a depth resolution of 0.5 mm. 相似文献
28.
Serge Della Negra Yvon Le Beyec Per Håkansson 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1985,9(1):103-106
A very simple time of flight mass spectrometer has been used to measure mass spectra for the negative ions of organic compounds in the mass range up to 3000 u. Desorbed ions were obtained by applying a constant negative voltage to a flat metallic surface, coated with a few micrograms of organic material. We show that electrons and negative ions are emitted simultaneously from the same point on the surface. Mass spectra obtained by this technique are compared to mass spectra for the same compounds, obtained with 252Cf fission fragment ionization. 相似文献
29.
Achieving economic competitiveness as compared to LWRs and other Generation IV (Gen-IV) reactors is one of the major requirements to attract large-scale investment in commercial sodium cooled fast reactor (SFR) power plants. Advances in R&D for advanced SFR fuel and structural materials provide key long-term opportunities to improve SFR economics. In addition, other new opportunities are emerging to further improve SFR economics. This paper provides an overview on potential ideas from the perspective of thermal hydraulics to improve SFR economics. These include: (1) a new hybrid loop-pool reactor design to further optimize economics, safety, and reliability of SFRs with more flexibility, (2) a multiple-reheat and intercooling helium Brayton cycle to improve plant thermal efficiency and to reduce safety related overnight and operation costs, and (3) modern multi-physics thermal analysis methods to reduce analysis uncertainties and associated requirements for over-conservatism in reactor design. This paper reviews advances in all three areas and their potential beneficial impacts on SFR economics. 相似文献
30.
Martin Friis Christer Persson Per Nylén Jan Wigren 《Journal of Thermal Spray Technology》2001,10(2):301-310
A detailed investigation of the relationship between the parameters of the spray process and the in-flight properties of the
particles was carried out using a multivariate statistical approach. A full factorial designed experiment concerning the spray
process was performed, the spray gun parameters’ current, argon flow rate, hydrogen flow rate, and powder feed rate being
selected to control the process. The particle properties, viz. velocity, temperature, and diameter, were determined using an optical measurement system, DPV 2000. In addition, the standard
deviations of, and the correlations between, the measured particle properties were analyzed. The results showed current to
have the strongest impact on particle velocity and particle temperature and argon flow rate to be the only parameter with
an inverse effect on velocity and temperature. 相似文献