全文获取类型
收费全文 | 1115篇 |
免费 | 65篇 |
专业分类
电工技术 | 47篇 |
综合类 | 4篇 |
化学工业 | 332篇 |
金属工艺 | 20篇 |
机械仪表 | 12篇 |
建筑科学 | 51篇 |
能源动力 | 50篇 |
轻工业 | 112篇 |
水利工程 | 12篇 |
无线电 | 65篇 |
一般工业技术 | 245篇 |
冶金工业 | 66篇 |
原子能技术 | 18篇 |
自动化技术 | 146篇 |
出版年
2023年 | 17篇 |
2022年 | 22篇 |
2021年 | 46篇 |
2020年 | 25篇 |
2019年 | 43篇 |
2018年 | 35篇 |
2017年 | 23篇 |
2016年 | 33篇 |
2015年 | 51篇 |
2014年 | 39篇 |
2013年 | 75篇 |
2012年 | 61篇 |
2011年 | 91篇 |
2010年 | 35篇 |
2009年 | 42篇 |
2008年 | 40篇 |
2007年 | 57篇 |
2006年 | 36篇 |
2005年 | 35篇 |
2004年 | 27篇 |
2003年 | 30篇 |
2002年 | 24篇 |
2001年 | 14篇 |
2000年 | 20篇 |
1999年 | 17篇 |
1998年 | 36篇 |
1997年 | 27篇 |
1996年 | 9篇 |
1995年 | 15篇 |
1994年 | 19篇 |
1993年 | 15篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1989年 | 11篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1936年 | 2篇 |
1933年 | 6篇 |
1932年 | 5篇 |
1931年 | 11篇 |
1930年 | 3篇 |
1919年 | 2篇 |
1910年 | 2篇 |
排序方式: 共有1180条查询结果,搜索用时 46 毫秒
131.
We describe the NMR signal formation properties of a single vessel. Instead of assuming the frequency distribution to be a
simple Lorentzian or Gaussian one, we take into account that the frequency distribution around the vessel is a complex function.
Considering the static dephasing regime we find a relationship between signal formation and frequency distribution. Analytical
expressions for the frequency distribution in a voxel and the magnetization decay are obtained. In the case of small volume
fractions of blood and week magnetic fields the results can be used for describing signal formation processes in a vascular
network. A relationship between the frequency distribution and the properties of the vascular network is derived. The magnetization
decay in different time regimes is discussed. The result is relevant for describing signal formation processes around a vessel
for arbitrary pulse sequences. 相似文献
132.
133.
Eckhard Nußmüller 《国际钢铁研究》1982,53(12):489-494
Die routinemäßige Ultraschallprüfung von Schmiedestücken und ihre Grenzen. Festlegungen in Regelwerken, Forderungen hinsichtlich Registrier- und Zulässigkeitsgrenzen. Prüfung austenitischer Bauteile, Einsatz spezieller Prüfköpfe und Geräte. Möglichkeiten der Automatisierung, Ausblick auf zukünftige Entwicklungen. 相似文献
134.
A meta-analytic review of 53 studies (N = 9,145) finds that in messages aimed at encouraging disease detection behaviors, loss-framed appeals (which emphasize the disadvantages of noncompliance with the communicator's recommendation) are only slightly, but statistically significantly, more persuasive than gain-framed appeals (which emphasize the advantages of compliance); the difference corresponds to a correlation of −.04. Loss-framed appeals enjoy a small statistically significant advantage for messages advocating breast cancer detection behaviors, but not for any other kind of detection behavior (detection of skin cancer, other cancers, dental problems, or miscellaneous other diseases) nor for all other kinds of detection behaviors combined. Thus, in advocacy of disease detection behaviors, using loss-framed rather than gain-framed appeals is unlikely to substantially improve persuasiveness. 相似文献
135.
136.
Im vorliegenden Beitrag wird über Querkraftversuche an insgesamt zehn Stahlbetonbalken berichtet, von denen acht mit nachträglich eingemörtelten Bewehrungsstäben verstärkt wurden. Anzahl und Abstand der geneigten Bewehrungsstäbe sowie die verwendeten Verbundmörtel wurden variiert. Während am oberen Ende der Stäbe eine Verankerung im Bauteilinneren durch Verbund erfolgte, wurden für die Verankerung an der Tragwerksunterseite eigene Ankerkörper entwickelt. Die Versuche bestätigen die Wirksamkeit der Maßnahme, die keine Änderungen der Bauteilabmessungen erfordert und von der Tragwerksunterseite her durchgeführt werden kann. Im Zuge der Untersuchungen wurden auch grundlegende phänomenologische Erkenntnisse zur Querkraftabtragung von Stahlbetonbalken gewonnen, insbesondere was die Rissverzahnung entlang des Schubrisses, den Anteil der Dübelwirkung der Längsbewehrung sowie die Mitwirkung der Biegedruckzone betrifft. Bending Shear Tests on R/C‐Beams with Post‐Installed Shear Reinforcement A research project has been started to investigate a new method of strengthening beams with insufficient shear resistance by applying post‐installed reinforcement. 10 reinforced concrete beams have been tested in shear, number and location of the inclined rebars as well as type of injection mortar have been varied. The rebars were installed in mortar‐injected boreholes and anchored with metal plates at the accessible bar end. The test results confirmed that post‐installed rebars can significantly increase the beam shear resistance provided they are situated properly and adequate injection mortars used. Above that the evaluation of the different contributions to shear resistance like truss action, dowel action and shear strength of compression chord provides new findings on the general shear failure mechanism in RC structures. 相似文献
137.
Photoinitiated oxidation of geosmin and 2-methylisoborneol by irradiation with 254 nm and 185 nm UV light 总被引:1,自引:0,他引:1
The degradation of geosmin and 2-methylisoborneol (2-MIB) by UV irradiation at different wavelengths was investigated under varying boundary conditions. The results showed that conventional UV radiation (254 nm) is ineffective in removing these compounds from water. In contrast to the usual UV radiation UV/VUV radiation (254 + 185 nm) was more effective in the removal of the taste and odour compounds. The degradation could be described by a simple pseudo first-order rate law with rate constants of about 1.2 × 10−3 m2 J−1 for geosmin and 2-MIB in ultrapure water. In natural water used for drinking water abstraction the rate constants decreased to 2.7 × 10−4 m2 J−1 for geosmin and 2.5 × 10−4 m2 J−1 for 2-MIB due to the presence of NOM. Additionally, the formation of the by-product nitrite was studied. In the UV/VUV irradiation process up to 0.6 mg L−1 nitrite was formed during the complete photoinitiated oxidation of the odour compounds. However, the addition of low ozone doses could prevent the formation of nitrite in the UV/VUV irradiation experiments. 相似文献
138.
Determination of the construction and the material identity values of outside building components with the help of in‐situ measuring procedures and FEM‐simulation calculations. The aims formulated nationwide and internationally to the climate protection can be achieved by combining of the energy‐efficient construction and rehabilitation of the existing buildings. Knowledge about the construction and the material identity values of the warmth‐transferring outside components is a condition for the energetic balance of buildings. The essential information to this can frequently be no more taken from the construction documents particularly for older buildings since they are no longer traceable or incomplete. At the example by univalve and bivalve out‐wall construction it is shown that the thermophysical qualities can be determined with the help of in‐situ measuring procedures and FE‐simulation calculations without destruction. 相似文献
139.
Quantification and localization of contrast agents using delta relaxation enhanced magnetic resonance at 1.5?T 总被引:1,自引:1,他引:0
Object
Delta relaxation enhanced magnetic resonance (dreMR) is a new imaging technique based on the idea of cycling the magnetic field B 0 during an imaging sequence. The method determines the field dependency of the relaxation rate (relaxation dispersion dR 1/dB). This quantity is of particular interest in contrast agent imaging because the parameter can be used to determine contrast agent concentrations and increases the ability to localize the contrast agent.Materials and methods
In this paper dreMR imaging was implemented on a clinical 1.5?T MR scanner combining conventional MR imaging with fast field-cycling. Two improvements to dreMR theory are presented describing the quantification of contrast agent concentrations from dreMR data and a correction for field-cycling with finite ramp times.Results
Experiments demonstrate the use of the extended theory and show the measurement of contrast agent concentrations with the dreMR method. A second experiment performs localization of a contrast agent with a significant improvement in comparison to conventional imaging.Conclusion
dreMR imaging has been extended by a method to quantify contrast agent concentrations and improved for field-cycling with finite ramp times. Robust localization of contrast agents using dreMR imaging has been performed in a sample where conventional imaging delivers inconclusive results. 相似文献140.
Raundahl J Loog M Pettersen P Tanko LB Nielsen M 《IEEE transactions on medical imaging》2008,27(8):1054-1060