全文获取类型
收费全文 | 1441篇 |
免费 | 29篇 |
专业分类
电工技术 | 118篇 |
化学工业 | 329篇 |
金属工艺 | 27篇 |
机械仪表 | 31篇 |
建筑科学 | 18篇 |
矿业工程 | 2篇 |
能源动力 | 62篇 |
轻工业 | 120篇 |
石油天然气 | 3篇 |
无线电 | 107篇 |
一般工业技术 | 252篇 |
冶金工业 | 270篇 |
原子能技术 | 42篇 |
自动化技术 | 89篇 |
出版年
2023年 | 6篇 |
2022年 | 13篇 |
2021年 | 30篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 20篇 |
2017年 | 6篇 |
2016年 | 20篇 |
2015年 | 23篇 |
2014年 | 22篇 |
2013年 | 74篇 |
2012年 | 64篇 |
2011年 | 102篇 |
2010年 | 64篇 |
2009年 | 51篇 |
2008年 | 73篇 |
2007年 | 69篇 |
2006年 | 55篇 |
2005年 | 40篇 |
2004年 | 45篇 |
2003年 | 43篇 |
2002年 | 37篇 |
2001年 | 14篇 |
2000年 | 19篇 |
1999年 | 30篇 |
1998年 | 123篇 |
1997年 | 76篇 |
1996年 | 48篇 |
1995年 | 32篇 |
1994年 | 29篇 |
1993年 | 28篇 |
1992年 | 17篇 |
1991年 | 10篇 |
1990年 | 18篇 |
1989年 | 16篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 15篇 |
1982年 | 4篇 |
1981年 | 12篇 |
1980年 | 5篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1976年 | 13篇 |
1975年 | 4篇 |
1972年 | 3篇 |
1971年 | 4篇 |
排序方式: 共有1470条查询结果,搜索用时 31 毫秒
61.
This paper describes the effect of a passive EMI filter on preventing bearing current from flowing inside an inverter‐driven motor. Motor‐bearing damage is often caused by bearing currents resulting from the breakdown of grease films in the motor bearing. The high‐frequency common‐mode voltage generated by the PWM inverter induces a shaft voltage between the rotor and the frame. When the shaft voltage exceeds the breakdown voltage of the grease films, a destructive instantaneous discharge current with a peak value of about 1 A flows through the motor bearing. The passive EMI filter, which is unique in access to the motor neutral line, can reduce the shaft voltage as a result of eliminating the high‐frequency common‐mode voltage from the motor terminals. Hence, no breakdown occurs in the grease film, so that no bearing current flows. The viability and effectiveness of the passive EMI filter is verified by experimental results obtained from a 400‐V, 3.7‐kW laboratory system. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(2): 78– 87, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20489 相似文献
62.
Kikuo Matsui Hideki Shimada Takashi Sasaoka Hirofumi Furukawa Takeshi Ueda Atsuko Yabuki 《国际露天开采、回填与环境杂志》2013,27(3):185-204
Conventional highwall mining extracts coal with an auger machine or a continuous miner from exposed seams at the base of opencut or strip operations. However, under poor strata and high stress conditions, highwall mining cannot be conducted due to pillar and roof failures. In such cases, punch highwall mining is more effective than the conventional highwall mining. This paper describes conventional highwall mining and punch highwall mining systems and discusses the stability of the highwall due to punch highwall mining at opencut coal mines. 相似文献
63.
Hideki Tanaka Daisuke Noguchi Akiko Yuzawa Tetsuya Kodaira Hirofumi Kanoh Katsumi Kaneko 《Journal of Low Temperature Physics》2009,157(3-4):352-373
We have investigated the applicability of simulations and theoretical techniques for exploring the selectivities of hydrogen isotopes. We have simulated the adsorption isotherms of H2 in an idealized carbon slit pore at 77 K by using the grand canonical Monte Carlo simulations with the Feynman-Hibbs effective potential (FH-GCMC) and the rigorous path integral method (PI-GCMC), and we obtained good agreement between the isotherms from both simulations. This suggests that FH-GCMC, which uses the approximative Feynman-Hibbs treatment, is as useful as PI-GCMC for exploring H2 adsorption at 77 K. Moreover, we show that the ideal adsorption solution theory (IAST) can predict the selectivity of D2 over H2 in the interstices of single-wall carbon nanotube (SWNT) bundles at 77 K (below 0.1 MPa) very well by comparing the obtained results with the mixture adsorption FH-GCMC simulations. This indicates that IAST is also applicable to the estimation of the selectivity of D2 over H2 at moderate pressures and at 77 K from experimental single-component adsorption isotherms. We also demonstrate that the FH-GCMC simulation can reproduce the experimental adsorption isotherms of H2 and D2 in aluminophosphate AlPO4-5 at 77 K. Finally, we analyze the selectivity of D2 over H2 by IAST with the experimental single-component adsorption isotherms of H2 and D2 at 77 K for a variety of adsorbents: AlPO4-5, activated carbon fibers (ACFs), HiPco SWNT, and SWNHs. The selectivities predicted by the experimental adsorption data based on the results from the FH-GCMC simulations are presented and discussed. 相似文献
64.
65.
Shindo T Ushiyama H Kan K Uehara S Yasuda K Takano I Saito K 《Shokuhin eiseigaku zasshi. Journal of the Food Hygienic Society of Japan》2002,43(3):122-126
The contents of barbaloin (BA), isoBA, aloin-dimers A, B, C, D and aloe-emodin (AE) in aloe drinks were investigated. BA and isoBA were detected in 30 of the 31 samples at the levels of 120-570 micrograms/mL and 120-580 micrograms/mL, respectively. Aloin-dimers A, B, C and D were detected in 8 of the 31 samples at the levels of 12-38 micrograms/mL, 13-39 micrograms/mL, 11-36 micrograms/mL and 16-69 micrograms/mL, respectively. AE was detected in all of the 31 samples at the levels of 0.03-1.3 micrograms/mL. When aloe drinks were stored for 4 weeks at 5 degrees C after opening the bottle, decrease of BA and isoBA, and increase of AE and aloin-dimers A, B, C and D were observed in most cases. However, in a few aloe drinks, all of BA, isoBA, aloin-dimers A, B, C, D and AE decreased. In these drinks, the existence of aloin-trimer was elucidated by LC/MS analyses. These data suggested that BA in aloe drinks is converted to the dimer and then to the trimer during storage. 相似文献
66.
Hirofumi Hirayama Toshihiro Itoh Yoshihiko Nakaki Takahiko Yoshida 《Artificial Life and Robotics》2005,9(3):144-160
A mathematical method is introduced to characterize the electrokinetic behavior (electrophoresis) of a biomolecular particle which passes through a specific channel pore on an excitable biological membrane. The basic approach was first proposed by Booth (1950). The system was described by an equation of continuity and an equation of motion in which the driving force involves the diffusion effect, the hydrostatic pressure, and the electrostatic potential. By assuming linear relations between the velocity and the applied electrical field, solutions for the potential, pressure, and velocity were given by a series expansion of the charges on the particle. To examine the influence of ions surrounding the particle and forming an ionic cloud, the Debye–Huckel parameter was introduced. As the thickness of the double layer around the particle increased, the potential, velocity, pressure, and viscosity were changed significantly. The maximum influence was obtained when the radius of the particle became equal to the thickness of the double layer. Although this theory is valid for a charged, spherical, nonconducting particle only, the method is available for evaluating the kinetic behavior of a biomolecule that passes through a channel pore on a cellular membrane.This work was presented, in part, at the 8th International Symposium on Artificial Life and Robotics, Oita, Japan, January 24–26, 2003 相似文献
67.
Yasushi Sakurai Masatoshi Yoshikawa Shunsuke Uemura Haruhiko Kojima 《The VLDB Journal The International Journal on Very Large Data Bases》2002,11(2):93-108
We propose a novel index structure, the A-tree (approximation tree), for similarity searches in high-dimensional data. The
basic idea of the A-tree is the introduction of virtual bounding rectangles (VBRs) which contain and approximate MBRs or data
objects. VBRs can be represented quite compactly and thus affect the tree configuration both quantitatively and qualitatively.
First, since tree nodes can contain a large number of VBR entries, fanout becomes large, which increases search speed. More
importantly, we have a free hand in arranging MBRs and VBRs in the tree nodes. Each A-tree node contains an MBR and its children
VBRs. Therefore, by fetching an A-tree node, we can obtain information on the exact position of a parent MBR and the approximate
position of its children. We have performed experiments using both synthetic and real data sets. For the real data sets, the
A-tree outperforms the SR-tree and the VA-file in all dimensionalities up to 64 dimensions, which is the highest dimension
in our experiments. Additionally, we propose a cost model for the A-tree. We verify the validity of the cost model for synthetic
and real data sets.
Edited by T. Sellis. Received: December 8, 2000 / Accepted: March 20, 2002 Published online: September 25, 2002 相似文献
68.
Interferograms obtained with ordinary interferometers, such as the Fizeau interferometer or the Twyman-Green interferometer, show the contour maps of a wave front under test. On the other hand, lateral shearing interferograms show the difference between a wave front under test and a sheared wave front, that is, the inclination of the wave front. Therefore the shape of the wave front under test is reconstructed by means of analyzing the difference. To reconstruct the wave front, many methods have been proposed. An integration method is usually used to reconstruct the wave front under test rapidly. However, this method has two disadvantages: The analysis accuracy of the method is low, and part of the wave front cannot be measured. To overcome these two problems, a new, to our knowledge, integration method, improved by use of polynomials, is proposed. The validity of the proposed method is evaluated by computer simulations. In the simulations the analysis accuracy achieved by the proposed method is compared with the analysis accuracy of the ordinary integration method and that of the method proposed by Rimmer and Wyant. The results of the simulations show that the analysis accuracy of the newly proposed method is better than that of the integration method and that of the Rimmer-Wyant method. 相似文献
69.
Sone T Hanamizu T Ichioka M Yokokura T Yoshikawa S Kondo-Yanai N Hiraki Y Esumi K 《International journal of cosmetic science》1999,21(1):23-31
The moisturizing effect of vesicles formed from monoglycerides on human skin was studied by measurement of conductance on and transepidermal waterloss from the skin surface. Although sonication of the monoglycerides in water with Ca2+ gave multilamellar vesicles, the lamellar structure of the vesicles disappeared during their storage without any other additive. With the addition of poly(vinylpyrrolidone) after the sonication, the stability of the vesicles increased and their lamellar structure was maintained for 3 months at 40 degrees C. These vesicles led to a significantly higher water content of the stratum corneum of human skin compared with non-lamellar monoglyceride, and consequently they improved rough human skin. 相似文献
70.
Masatoshi Tosaka Masaki Tsuji Hirofumi Kitano Shinzo Kohjiya Kuniaki Nagayama 《Polymer》2006,47(4):951-955
Self-assembly of nano-sized arrays by casting a dilute solution of a guest material on the friction-transferred poly(tetrafluoroethylene) (FT-PTFE) substrate was newly discovered. Long axis of the rod-like structures forming the arrays is aligned perpendicular to the chain direction of FT-PTFE, and accordingly, the arrays are highly anisotropic. This phenomenon was observed for aqueous or organic solutions of polymers or organic materials. Each rod-like structure forming the arrays is composed of small grains. The arrays in question are formed regardless to the crystallinity of the guest materials. The formation mechanism of the nano-sized arrays is still unclear. However, we guess that they are formed as a result of microscopic flow pattern at the edge of the solution film. The arrays in question may be a new type of dissipative structure. 相似文献