全文获取类型
收费全文 | 7595篇 |
免费 | 177篇 |
国内免费 | 31篇 |
专业分类
电工技术 | 484篇 |
综合类 | 19篇 |
化学工业 | 1848篇 |
金属工艺 | 198篇 |
机械仪表 | 178篇 |
建筑科学 | 224篇 |
矿业工程 | 1篇 |
能源动力 | 307篇 |
轻工业 | 662篇 |
水利工程 | 25篇 |
石油天然气 | 10篇 |
无线电 | 616篇 |
一般工业技术 | 1242篇 |
冶金工业 | 993篇 |
原子能技术 | 277篇 |
自动化技术 | 719篇 |
出版年
2023年 | 31篇 |
2022年 | 20篇 |
2021年 | 119篇 |
2020年 | 69篇 |
2019年 | 78篇 |
2018年 | 100篇 |
2017年 | 76篇 |
2016年 | 133篇 |
2015年 | 101篇 |
2014年 | 181篇 |
2013年 | 415篇 |
2012年 | 238篇 |
2011年 | 379篇 |
2010年 | 325篇 |
2009年 | 329篇 |
2008年 | 398篇 |
2007年 | 321篇 |
2006年 | 268篇 |
2005年 | 285篇 |
2004年 | 255篇 |
2003年 | 217篇 |
2002年 | 223篇 |
2001年 | 158篇 |
2000年 | 149篇 |
1999年 | 159篇 |
1998年 | 394篇 |
1997年 | 280篇 |
1996年 | 202篇 |
1995年 | 137篇 |
1994年 | 159篇 |
1993年 | 147篇 |
1992年 | 99篇 |
1991年 | 110篇 |
1990年 | 90篇 |
1989年 | 101篇 |
1988年 | 88篇 |
1987年 | 71篇 |
1986年 | 90篇 |
1985年 | 85篇 |
1984年 | 88篇 |
1983年 | 79篇 |
1982年 | 88篇 |
1981年 | 77篇 |
1980年 | 66篇 |
1979年 | 60篇 |
1978年 | 56篇 |
1977年 | 41篇 |
1976年 | 56篇 |
1975年 | 26篇 |
1973年 | 19篇 |
排序方式: 共有7803条查询结果,搜索用时 343 毫秒
991.
Polyacrylic chloride was reacted with aminonaphthol sulfonic acid to give a polymeric intermediate, from which the corresponding dyestuff was prepared by coupling with an aromatic diazonium salt. The water-solubility of the polymeric azo dye was found to depend mainly on the number of sulfonic groups in the molecular chain, and the colouring of dye was comparatively rich in variety. A copolymer of acrylic chloride with methyl methacrylate was directly reacted with a dyestuff containing amino groups to give a polymeric dye. In the molecular chain of those polymeric dyes, the functional structure of the dyestuff was kept by its incorporation to the acrylic polymer chain. 相似文献
992.
Hiroshi Wada 《International Journal of Engineering Science》1981,19(7):967-977
Using the Pochhammer-Chree equation and applying Laplace transformations with respect to time and numerical inverse Laplace transformations, reflection characteristics of torsional waves in a semi-infinite rod connected to an elastic half-space are analyzed under a condition where the incident stress pulse varies proportionally with the distance from the rod axis. Time histories of surface torsional stress and circumferential displacement, and cross-sectional torsional stress and circumferential displacement distributions of the semi-infinite rod at an arbitrary point are shown. When the shear modulus ratio and the velocity ratio are small, i.e. The half-space is hard and the rod is soft, time histories of surface stress and displacement obtained from the Pochhammer-Chree equation coincide with those obtained from the elementary equation which is derived from the assumption that each cross-section of the rod undergoes a pure rotation about the rod axis. However, when and are not small, the curves obtained from the Pochhamer-Chree equation differ from those obtained from the elementary equation, and the difference in stress increases as the observed point approaches the interface between the rod and the half-space. 相似文献
993.
Nuclear magnetic resonance absorption spectra of linter cellulose containing various amounts of water were studied to clarify the relation between the amount of absorbed water in cellulose fiber and the molecular motion in such a cellulose–water system. An amorphous cellulose sample was used for the sake of comparison. The changes in line width and second moment of the spectra were measured at various temperatures. From the variation with temperature of the first-derivative curves and the second moments, it has been inferred that the proton movement of absorbed water changes markedly over the approximate range 180°–200°K and that the absorbed water lowers the glass transition temperature of cellulose to room temperature. 相似文献
994.
Tetsuro?KitaharaEmail author Masataka?Goto Hiroshi?G.?Okuno 《Applied Intelligence》2005,23(3):267-275
This paper describes a musical instrument identification method that takes into consideration the pitch dependency of timbres of musical instruments. The difficulty in musical instrument identification resides in the pitch dependency of
musical instrument sounds, that is, acoustic features of most musical instruments vary according to the pitch (fundamental
frequency, F0). To cope with this difficulty, we propose an F0-dependent multivariate normal distribution, where each element of the mean vector is represented by a function of F0. Our method first extracts 129 features (e.g.,
the spectral centroid, the gradient of the straight line approximating the power envelope) from a musical instrument sound
and then reduces the dimensionality of the feature space into 18 dimension. In the 18-dimensional feature space, it calculates
an F0-dependent mean function and an F0-normalized covariance, and finally applies the Bayes decision rule. Experimental results of identifying 6,247 solo tones of 19 musical instruments
shows that the proposed method improved the recognition rate from 75.73% to 79.73%.
This research was partially supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Grant-in-Aid
for Scientific Research (A), No.15200015, and Informatics Research Center for Development of Knowledge Society Infrastructure
(COE program of MEXT, Japan).
Tetsuro Kitahara received the B.S. from Tokyo University of Science in 2002 and the M.S. from Kyoto University in 2004. He is currently a
Ph.D. course student at Graduate School of Informatics, Kyoto University. Since 2005, he has been a Research Fellow of the
Japan Society for the Promotion of Science. His research interests include music informatics. He recieved IPSJ 65th National
Convention Student Award in 2003, IPSJ 66th National Convention Student Award and TELECOM System Technology Award for Student
in 2004, and IPSJ 67th National Convention Best Paper Award for Young Researcher in 2005. He is a student member of IPSJ,
IEICE, JSAI, ASJ, and JSMPC.
Masataka Goto received his Doctor of Engineering degree in Electronics, Information and Communication Engineering from Waseda University,
Japan, in 1998. He then joined the Electrotechnical Laboratory (ETL; reorganized as the National Institute of Advanced Industrial
Science and Technology (AIST) in 2001), where he has been engaged as a researcher ever since. He served concurrently as a
researcher in Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Corporation
(JST) from 2000 to 2003, and an associate professor of the Department of Intelligent Interaction Technologies, Graduate School
of Systems and Information Engineering, University of Tsukuba since 2005. His research interests include music information
processing and spoken language processing. Dr. Goto received seventeen awards including the IPSJ Best Paper Award and IPSJ
Yamashita SIG Research Awards (MUS and SLP) from the Information Processing Society of Japan (IPSJ), Awaya Prize for Outstanding
Presentation and Award for Outstanding Poster Presentation from the Acoustical Society of Japan (ASJ), Award for Best Presentation
from the Japanese Society for Music Perception and Cognition (JSMPC), WISS 2000 Best Paper Award and Best Presentation Award,
and Interaction 2003 Best Paper Award. He is a member of the IPSJ, ASJ, JSMPC, Institute of Electronics, Information and Communication
Engineers (IEICE), and International Speech Communication Association (ISCA).
Hiroshi G. Okuno received the B.A. and Ph.D from the University of Tokyo in 1972 and 1996, respectively. He worked for Nippon Telegraph and
Telephone, Kitano Symbiotic Systems Project, and Tokyo University of Science. He is currently a professor at the Department
of Intelligence Technology and Science, Graduate School of Informatics, Kyoto University. He was a visiting scholar at Stanford
University, and a visiting associate professor at the University of Tokyo. He has done research in programming languages,
parallel processing, and reasoning mechanism in AI, and he is currently engaged in computational auditory scene analysis,
music scene analysis and robot audition. He received the best paper awards from the Japanese Society for Artificial Intelligence
and the International Society for Applied Intelligence, in 1991 and 2001, respectively. He edited with David Rosenthal “Computational
Auditory Scene Analysis” from Lawrence Erlbaum Associates in 1998 and with Taiichi Yuasa “Advanced Lisp Technology” from Taylor
and Francis Inc. in 2002. He is a member of IPSJ, JSAI, JSSST, JSCS, ACM, AAAI, ASA, and IEEE. 相似文献
995.
Toshifumi Ohkubo Kenji Tanaka Terunao Hirota Hiroshi Hosaka Kiyoshi Itao Yoko Shinohara Hideo Maeda Kenji Kato Yasuyuki Mitsuoka Kunio Nakajima 《Microsystem Technologies》2005,11(8-10):1094-1101
Advances in the digital network society require both higher density and higher transfer rates in all sorts of storage systems. Especially in optical recording, the trend toward higher density and larger capacity requires novel surface-recording technologies that can drastically diminish head-to-medium spacing, resulting in an improvement in spatial resolution and, finally, a higher recording density. To this end, we have already proposed a novel contact optical head slider that is able to almost cancel the suspension load by generating hydrodynamic pressure, thus realizing a lower net contact force. Evaluating the dynamic contact force is requisite in realizing its stable sliding operation and higher signal readout performance. In this study, a continuous acoustic emission (AE) signal was utilized to detect the dynamic contact force. AE signal modulation was compared with the applied out-of-plane acceleration on a medium generated by a spindle combined piezo-electric actuator. It was clarified that the detected AE modulation amplitude was approximately proportional to the applied acceleration, and that utilizing AE modulation will be a useful method for evaluating dynamic contact force. 相似文献
996.
The dynamics of a domain wall in ferromagnetic nanowires under electric current is theoretically studied. The driving mechanism is shown to depend on wall thickness. Thick walls, as in metallic wires, are propelled by the spin torque arising from spin polarization of current, while thin walls, as in nanocontacts and magnetic semiconductors, are driven by the pressure from charge current. The condition for small-current operation, which is a key issue when integrated into devices, is discussed. 相似文献
997.
Here we show a technique to obtain a tilt series of dark-field (DF) transmission electron microscopy (TEM) images in ordering alloys for tomographic three-dimensional (3D) observations. A tilt series of DF TEM images of D1a-ordered Ni4Mo precipitates in a Ni-Mo alloy was successfully obtained by adjusting a diffraction condition for a superlattice reflection from the Ni4Mo precipitates. Since the superlattice reflection usually has a long extinction distance, dynamic diffraction effects such as thickness fringes can be suppressed to some extent with precise realignment of the diffraction condition. By using the tilt series of the DF TEM images, we attempted a computed TEM tomography to visualize 3D shapes and positions of the precipitates. 相似文献
998.
Several azacrown ether derivatives, which are monoaza-12-crown-4, -15-crown-5, and -18-crown-6 and diaza-12-crown-4 and -18-crown-6, bearing one or two spirobenzopyran(s), which we call crowned spirobenzopyran or crowned bis(spirobenzopyran), were synthesized and were used as carriers for liquid membrane transport of alkali metal ions. The passive alkali metal transports through liquid membranes containing crowned spirobenzopyrans were carried out under dark, and UV- and visible-light irradiation conditions. The metal ion transport was accelerated and retarded by UV- and visible-light irradiation, respectively. On the other hand, the photoresponse of the metal ion selectivity in membrane transport by crowned spirobenzopyrans was different, depending on the kind of crown ether units. Especially, diaza-12-crown-4-bis(spirobenzopyran) exhibited an excellently selective and effective transporting ability for Li(+). The uphill transports of Li(+) through a liquid membrane containing monoaza-12-crown-4-spirobenzopyran or diaza-12-crown-4-bis(spirobenzopyran) were realized under the conditions where the same aqueous solution was used as the source and receiving phases with UV and visible lights being irradiated onto the boundary phases between the source and membrane phases and between the receiving and membrane phases, respectively. The uphill transport of Li(+) from the source to receiving phases through a liquid membrane containing a crowned spirobenzopyran was also attained by the proton-concentration gradient between the source and receiving phases under dark conditions, and the transporting ability was remarkably increased by photoirradiation. 相似文献
999.
Inhalation exposure to particles <10 microm in size that are suspended in the troposphere (PM10) is a factor in respiratory and cardiovascular diseases. The extent of the injury, local to systemic inflammation, is dependent on the number, size, and composition of the particles to which an individual is exposed. The physical properties of and compounds on PM10 that are responsible for these adverse effects on human health are the subject of intense investigation. Here, we report a laboratory method that involved the creation of 1-120 particles per trial that were of known size and composition, followed by deposition of them directly onto individual human lung cells within a cell culture, and after an incubation period, a downstream biological response was measured. To illustrate this methodology, particles that each contained 50 pg of lipopolysaccharide were created and deposited onto individual cells over a region <0.36 mm2 within a genetically modified A549 cell culture. The biological readout was the relative expression of intercellular cell adhesion molecule 1 after 24 h of incubation using an immunocytochemistry assay. The apparatus and methodology introduced here enables studies at the interface between the relevant but diverse areas of atmospheric particle chemistry and lung cell biology to identify the chemical and physical factors of PM10 that cause/exacerbate respiratory and cardiovascular diseases by triggering various biological pathways. 相似文献
1000.
Quantitative detection system for maize sample containing combined-trait genetically modified maize 总被引:4,自引:0,他引:4
Akiyama H Watanabe T Wakabayashi K Nakade S Yasui S Sakata K Chiba R Spiegelhalter F Hino A Maitani T 《Analytical chemistry》2005,77(22):7421-7428
Various countries have established regulations that stipulate the labeling of agricultural commodities, feed, and food products that contain or are made from genetically modified (GM) material or that contain adventitious GM material in amounts that exceed certain threshold levels. While regulations in some countries refer to GM material on a weight per weight (w/w) percentage, the currently applied detection methods do not directly measure the w/w percentage of the GM material. Depending on the particular method and the sample matrix it is applied to, the conversion of analytical results to a w/w percentage is challenging or not possible. The first rapid PCR system for GM maize detection on a single kernel basis has been developed. The equipment for the grinding of individual kernels and a silica membrane-based 96-well DNA extraction kit were both significantly revised and optimized for this particular purpose, respectively. We developed a multiplex real-time PCR method for the rapid quantification of GM DNA sequences in the obtained DNA solutions. In addition, a multiplex qualitative PCR detection method allows for the simultaneous detection of different GM maize traits in each kernel and thereby for identification of individual kernels that contain a combination of two or more GM traits. Especially for grain samples that potentially contain combined-trait GM maize kernels, the proposed methods can deliver informative results in a rapid, precise, and reliable manner. 相似文献