全文获取类型
收费全文 | 4961篇 |
免费 | 91篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 174篇 |
综合类 | 2篇 |
化学工业 | 849篇 |
金属工艺 | 114篇 |
机械仪表 | 109篇 |
建筑科学 | 99篇 |
矿业工程 | 1篇 |
能源动力 | 102篇 |
轻工业 | 395篇 |
水利工程 | 26篇 |
石油天然气 | 7篇 |
无线电 | 522篇 |
一般工业技术 | 854篇 |
冶金工业 | 1349篇 |
原子能技术 | 116篇 |
自动化技术 | 340篇 |
出版年
2023年 | 19篇 |
2022年 | 42篇 |
2021年 | 71篇 |
2020年 | 43篇 |
2019年 | 47篇 |
2018年 | 57篇 |
2017年 | 41篇 |
2016年 | 67篇 |
2015年 | 42篇 |
2014年 | 83篇 |
2013年 | 225篇 |
2012年 | 126篇 |
2011年 | 203篇 |
2010年 | 136篇 |
2009年 | 168篇 |
2008年 | 173篇 |
2007年 | 148篇 |
2006年 | 164篇 |
2005年 | 139篇 |
2004年 | 135篇 |
2003年 | 149篇 |
2002年 | 131篇 |
2001年 | 99篇 |
2000年 | 90篇 |
1999年 | 138篇 |
1998年 | 493篇 |
1997年 | 341篇 |
1996年 | 254篇 |
1995年 | 135篇 |
1994年 | 131篇 |
1993年 | 144篇 |
1992年 | 61篇 |
1991年 | 58篇 |
1990年 | 60篇 |
1989年 | 54篇 |
1988年 | 49篇 |
1987年 | 32篇 |
1986年 | 53篇 |
1985年 | 58篇 |
1984年 | 39篇 |
1983年 | 41篇 |
1982年 | 39篇 |
1981年 | 44篇 |
1980年 | 40篇 |
1979年 | 27篇 |
1978年 | 17篇 |
1977年 | 28篇 |
1976年 | 48篇 |
1975年 | 13篇 |
1973年 | 13篇 |
排序方式: 共有5059条查询结果,搜索用时 15 毫秒
991.
992.
Shimizu T. Hirakata M. Kamezawa T. Watanabe H. 《Power Electronics, IEEE Transactions on》2001,16(3):293-300
Photovoltaic modules must generally be connected in series in order to produce the voltage required to efficiently drive an inverter. However, if even a very small part of photovoltaic module (PV module) is prevented from receiving light, the generation power of the PV module is decreased disproportionately. This greater than expected decrease occurs because PV modules which do not receive adequate light cannot operate on the normal operating point, but rather operate as loads. As a result, the total power from the PV modules is decreased if even only a small part of the PV modules are shaded. In the present paper, a novel circuit, referred to as the generation control circuit (GCC), which enables maximum power to be obtained from all of the PV modules even if some of the modules are prevented from receiving light. The proposed circuit enables the individual PV modules to operate effectively at the maximum power point tracking, irrespective of the series connected PV module system. In addition, the total generated power is shown experimentally to increase for the experimental set-up used in the present study 相似文献
993.
Hiroyuki Watanabe Toshiji Mukai Kenji Higashi 《Metallurgical and Materials Transactions A》2001,32(4):923-929
Effect of microstructural factors on superplastic behavior in magnesium-based composites was reviewed in order to obtain insights
on ways to enhance the superplastic properties, such as highstrain-rate superplasticity, low-temperature superplasticity,
and high ductility. The review shows that the reduction in grain size of the matrix directly increases the strain rate and/or
decreases the temperature for optimum superplastic flow. The effect of reinforcement addition is shown to reduce the superplastic
elongation, but enhance the superplastic strain rate, presumably owing to grain size stability of composites at high temperatures.
Ductility enhancement is not necessarily attained by refining initial grain size. It is suggested that it is necessary to
disperse the reinforcement uniformly in order to obtain higher ductility. 相似文献
994.
Naoufal Bahlawane Tadahiko Watanabe Yoshiharu Waku Atsuyuki Mitani Narihito Nakagawa 《Journal of the American Ceramic Society》2000,83(12):3077-3081
The corrosion resistance of a unidirectionally solidified alumina/yttrium aluminum garnet (Al2 O3 /YAG) eutectic mixture was investigated at high temperature. Samples were exposed to high temperature (1200°–1800°C) in different atmospheres, which included argon, argon/water vapor, air, and air/water vapor. The most important microstructural changes occurred at the interface between the YAG and the Al2 O3 . Those changes consisted of localized thermal grooving, especially when the corrosive atmosphere contained water vapor. The samples exhibited significant weight loss at high temperature (1800°C) after 20 h of exposure. The calculated volume gain that was induced by the increased surface relief was low and limited, except when the corrosive atmosphere contained air, which indicated that the presence of air (particularly oxygen) induced a more-active corrosion process. On the other hand, no change in the flexural strength was observed, even after 100 h at 1800°C in a humid atmosphere, because of the cross-linked structure of the composite, which limited propagation of the groove. 相似文献
995.
An anhydrous alumina (Al2 O3 ) sol was prepared from aluminum isopropoxide and an organic solvent, using an acetic acid stabilizer. The complete conversion of the dried sol to α-Al2 O3 was accomplished at a temperature of 950°C by a single transition via γ-Al2 O3 . Al2 O3 that was deposited via dip coating resulted in amorphous films, even after annealing at 1100°C, because of the silicon diffusion from the substrate. This phenomenon was avoided using a rapid thermal treatment in a flame after dip coating, which resulted in uniform thin films that are converted to α-Al2 O3 via heat treatment. 相似文献
996.
Atsumi S. Umezawa A. Tanzawa T. Taura T. Shiga H. Takano Y. Miyaba T. Matsui M. Watanabe H. Isobe K. Kitamura S. Yamada S. Saito M. Mori S. Watanabe T. 《Solid-State Circuits, IEEE Journal of》2000,35(11):1648-1654
A 1.8-V-only 32-Mb NOR flash EEPROM has been developed based on the 0.25-μm triple-well double-metal CMOS process. A channel-erasing scheme has been implemented to realize a cell size of 0.49 μm2 , the smallest yet reported for 0.25-μm CMOS technology. A block decoder circuit with a novel erase-reset sequence has been designed for the channel-erasing operation. A bitline direct sensing scheme and a wordline boosted voltage pooling method have been developed to obtain high-speed reading operation at low voltage. An access time of 90 ns at 1.8 V has been realized 相似文献
997.
In this paper, a mechanical sensorless control system is reported for salient-pole brushless DC motor drives. Here, two new methods are proposed for obtaining the position angle, the accuracy of which affects the operation of the switching devices of the inverter that drives the motor. First, the method for estimating the position angle is proposed. Secondly, the correcting method for reducing the errors involved in the estimation of position angle is given. The experimental results show that the estimated position angles are calibrated automatically, and then the proposed sensorless control system can control the speed and the position angles of the motor precisely 相似文献
998.
Watanabe T. Sakaida N. Yasaka H. Kano F. Koga M. 《Lightwave Technology, Journal of》2000,18(8):1069-1077
We examine the fiber transmission performance of the optical signal whose chirp is controlled by utilizing phase modulation in semiconductor optical amplifier (SOA) with both simulations and experiments. This chirp control technique converts a positive chirp created by electroabsorption (EA) modulator into negative chirp, which reduces the waveform degradation due to the chromatic dispersion in transmission over standard single-mode fiber (SMF). It also provides an optical gain that is sufficient to compensate the insertion loss of the EA modulator. We investigate how the chirp control is affected by the input power to the SOA and the carrier lifetime of the SOA. As the SOA input power increases, the negative chirp becomes large, while the waveform is largely distorted due to gain saturation. However, the waveform distortion at high SOA input powers can be shaped by using a frequency discriminator. The acceleration of the carrier lifetime also reduces the waveform distortion due to gain saturation. We demonstrate that the chirp control technique is effective even for a high bit rate optical signal up to 10 Gb/s, when the carrier lifetime is expedited by optical pumping 相似文献
999.
Two types of polyelectrolyte multilayers were formed on both sides of a quartz crystal microbalance (QCM) substrate by a novel
alternate drop coating process. In this study, poly(diallyldimethylammonium chloride) (PDDA) and poly(sodium 4-styrene sulfonate)
(PSS) were used as strong-strong polyelectrolytes. On the other hand, PDDA and poly(acrylic acid) (PAA) were used as strong-weak
polyelectrolytes. The novel alternate drop coating process can separately fabricate each polyelectrolyte multilayer on both
sides of the substrate. The substrate provides dual biointerfaces, both sides of which comprise different multilayers, by
employing a combination of polymers. The formation of the multilayer by alternate drop coating was evaluated in terms of changes
in the frequency of the QCM and model protein adsorption for proteins such as bovine serum albumin, and their characteristics
were investigated with those of the conventional alternate adsorption process by performing dip coating. There was no significant
difference between the surface properties resulting from the two formation conditions. This result strongly supported the
fact that the multilayers fabricated by alternate drop coating were similar in quality to those fabricated by conventional
dip coating. The resulting dual biointerfaces with polyelectrolyte multilayers provide alternative biofunctions in terms of
individual protein loading. In summary, the novel alternate drop coating process for substrates is a good candidate for the
preparation of dual biointerfaces in the biomedical field. 相似文献
1000.
DCB test simulation of stitched CFRP laminates using interlaminar tension test results 总被引:1,自引:0,他引:1
A simulation model for the delamination extension of stitched CFRP laminates and 3-D orthogonal interlocked fabric composites (3-D OIFC) has been developed using a 2-D finite element method incorporating interlaminar tension test results to simulate the experimental results of their DCB tests. The mechanical properties of through-the-thickness fiber were determined from the results of interlaminar tension tests in which the specimen included only one through-the-thickness yarn. The fracture phenomena around the through-the-thickness thread, such as debonding from the in-plane layer, slack absorption, fiber bridging, and the pull-out of broken threads from the in-plane layers, are also introduced into the FEM model. The present FEM simulation results were compared to DCB test results for certain stitched laminates and a 3-D OIFC, and the simulation results showed good agreement with the experimental results of DCB tests, including the load–displacement curve and Mode I strain energy release rate (GI). While it was difficult to estimate GI accurately when the DCB test specimen included different types of z-fiber fracture modes, the present model of FEM analysis can simulate the experimental results of DCB tests of stitched laminates and 3-D OIFC. It is suggested that the GI of CFRP with arbitrary z-fiber densities can be predicted by using this FEM analysis model together with interlaminar tension test results. 相似文献