全文获取类型
收费全文 | 10914篇 |
免费 | 614篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 135篇 |
综合类 | 49篇 |
化学工业 | 2728篇 |
金属工艺 | 287篇 |
机械仪表 | 250篇 |
建筑科学 | 738篇 |
矿业工程 | 44篇 |
能源动力 | 348篇 |
轻工业 | 970篇 |
水利工程 | 97篇 |
石油天然气 | 43篇 |
武器工业 | 1篇 |
无线电 | 827篇 |
一般工业技术 | 1902篇 |
冶金工业 | 699篇 |
原子能技术 | 79篇 |
自动化技术 | 2348篇 |
出版年
2023年 | 103篇 |
2022年 | 191篇 |
2021年 | 398篇 |
2020年 | 242篇 |
2019年 | 250篇 |
2018年 | 337篇 |
2017年 | 286篇 |
2016年 | 390篇 |
2015年 | 311篇 |
2014年 | 420篇 |
2013年 | 817篇 |
2012年 | 634篇 |
2011年 | 787篇 |
2010年 | 571篇 |
2009年 | 636篇 |
2008年 | 599篇 |
2007年 | 539篇 |
2006年 | 453篇 |
2005年 | 375篇 |
2004年 | 329篇 |
2003年 | 324篇 |
2002年 | 237篇 |
2001年 | 169篇 |
2000年 | 162篇 |
1999年 | 149篇 |
1998年 | 161篇 |
1997年 | 152篇 |
1996年 | 120篇 |
1995年 | 96篇 |
1994年 | 98篇 |
1993年 | 101篇 |
1992年 | 76篇 |
1991年 | 70篇 |
1990年 | 71篇 |
1989年 | 78篇 |
1988年 | 56篇 |
1987年 | 54篇 |
1986年 | 53篇 |
1985年 | 56篇 |
1984年 | 72篇 |
1983年 | 52篇 |
1982年 | 40篇 |
1981年 | 42篇 |
1980年 | 42篇 |
1979年 | 34篇 |
1978年 | 35篇 |
1977年 | 35篇 |
1976年 | 40篇 |
1975年 | 40篇 |
1973年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Fabrice Martin Marc-Etienne Jan Samuel Rey-Mermet Brahim Belgacem Dong Su Marco Cantoni Paul Muralt 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(7):1339-1343
Polycrystalline A1N thin films were deposited by RF reactive magnetron sputtering on Pt(111)/Ti electrode films. The substrates were tilted by an angle ranging from 40 degrees to 70 degrees with respect to the target normal. A low deposition temperature and a high sputter gas pressure were found ideal for tilted growth. The resulting grain tilt angle amounts to about half the substrate tilt angle. For coupling evaluation, 5 GHz solidly mounted resonator structures have been realized. The tilted grain A1N films exhibited a permittivity in the 9.5-10.5 range and loss tangent of 0.3%. Two shear modes as well as the longitudinal mode could be clearly identified. The coupling coefficient k2(eff) of the fundamental thickness shear mode (TS0) was found to be about 0.5%, which is compatible with a c-axis tilt of about 6 degrees. 相似文献
92.
93.
Careful combination of a metal compound,a ligand and an inorganic support material leads to supramolecular catalysts that mimic the structural, organizational and functional aspects of enzyme activity.After discussing essential features of metalloenzyme-catalyzed reactions and coordination chemistry in inorganic hosts, we present examples of supramolecular materials selected from our own work that eventually resulted in useful catalysts for organic transformations in the liquid phase. 相似文献
94.
Joseph Dunn Michael Neufeld Anmol Sheth Dirk Grunwald John Bennett 《Mobile Networks and Applications》2006,11(1):37-45
Many companies, organizations and communities are providing wireless hotspots that provide networking access using 802.11b wireless networks. Since wireless networks are more sensitive to variations
in bandwidth and environmental interference than wired networks, most networks support a number of transmission rates that
have different error and bandwidth properties. Access points can communicate with multiple clients running at different rates,
but this leads to unfair bandwidth allocation. If an access point communicates with a mix of clients using both 1 Mb/s and
11 Mb/s transmission rates, the faster clients are effectively throttled to 1 Mb/s as well. This happens because the 802.11
MAC protocol approximate “station fairness”, with each station given an equal chance to access the media. We provide a solution
to provide “rate proportional fairness”, where the 11 Mb/s stations receive more bandwidth than the 1 Mb/s stations. Unlike
previous solutions to this problem, our mechanism is easy to implement, works with common operating systems and requires no
change to the MAC protocol or the stations.
Joseph Dunn received an M.S. in computer science from the University of Colorado at Boulder in 2003, and B. S. in coputer science and
mathematics from the University of Arizona in 2001. His research interests are in the general area of computer systems, primarily
focusing on security and scalability in distributed systems. He is currently working on his Ph.D. in computer science from
the University of Colorado at Boulder.
Michael Neufeld received a Ph.D. in Computer Science from the University of Colorado at Boulder in December of 2004, having previously received
an M.S. in Computer Science from the University of Colorado at Boulder in 2000 and an A.B. in Computer Science from Princeton
University in 1993. His research interests are in the general area of computer system, specifically concentrating on wireless
networking, software defind/cognitive radio, and streerable antennas. He is currently a postdoc in the Computer Science department
at the University of Calorado at Boulder pursuing research related to software defined radio and new MAC protocols for steerable
phase array antennas.
Anmol Sheth is a Ph.D. student in Computer Science at the University of Colorado at Boulder. He received his B.S. in Computer Science
from the University of Pune, India in 2001. He has been co-leading the development of the MANTIS operating system. He has
co-authored three papers include MAC layer protocol design, energy-efficient wireless communication, and adapting communications
to mobility.
Dirk Grunwald received his Ph.D. from the University of Illinois in 1989 and joined the University of Colorado the same year. His work
addresses research and teaching in the broad area of “computer systems”, which includes computer architecture, operating systems,
networks, and storage systems. His interests also include issues in pervasive computing, novel computing models, and enjoying
the mountains. He is currently an Associate Professor in the Department of Computer Science and in Electrical and Computer
Engineering and is also the Director of the Colorado Center for Information Storage.
John Bennett is a Professor of Computer Science with a joint appointment in Electrical and Computer Engineering at the University of Colorado
at Boulder. He also serves as Associate Dean for Education in the College of Engineering and Applied Science. He joined the
CU-Boulder faculty in 2000, after serving on the faculty of Rice University for 11 years. While at Rice, Bennett pioneered
a course in engineering design for both engineering and non-engineering students that has been emulated at several universities
and high schools. In addition to other teaching awards, Bennett received the Keck Foundation National Award for Engineering
Teaching Excellence for his work on this course. Bennett received his Ph.D. in 1988 from the University of Washington. Prior
to completing his doctoral studies, he was a U.S. Naval Officer for several years and founded and served as President of Pacific
Mountain Research, Inc., where he supervised the design and development of a number of commercial computing systems. Bennett's
primary research interests are broadly focused in the area of distributed systems, and more narrowly in distributed information
management and distributed robotic macrosensors. 相似文献
95.
We present a technique for approximating isotropic BRDFs and precomputed self-occlusion that enables accurate and efficient prefiltered environment map rendering. Our approach uses a nonlinear approximation of the BRDF as a weighted sum of isotropic Gaussian functions. Our representation requires a minimal amount of storage, can accurately represent BRDFs of arbitrary sharpness, and is above all, efficient to render. We precompute visibility due to self-occlusion and store a low-frequency approximation suitable for glossy reflections. We demonstrate our method by fitting our representation to measured BRDF data, yielding high visual quality at real-time frame rates. 相似文献
96.
97.
Weijing He Haiyan Li Siu-Lun Fok J. Derek Jackson Jan R. Wright 《Nuclear Engineering and Design》2007,237(12-13):1437-1444
A series of quench tests on hollow cylindrical specimens made of the machinable ceramic, Pyrophyllite, has been performed. The specimens consistently fractured with two diametrically opposite longitudinal cracks. Finite element analysis indicates that the primary crack occurred at the stage when the strain energy of the cylinder reached its maximum during the thermal transient process, while the secondary crack was caused by stress waves generated following the primary crack. This is supported by experimental observation of the time of fracture and the crack morphology. The work reported here helps to shed light on the fracture criterion for brittle cylindrical components under transient thermal and dynamic loadings. 相似文献
98.
99.
Maciej Winiewski Artur Jakubiak Jan Szymanowski 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):209-214
Decyl isonicotiniate and decyl nicotiniate permit a rapid extraction of palladium(II) from its hydrochloride solutions. Decyl picoliniate is not a suitable extractant. 4-Octylphenylamine can act as a phase transfer catalyst when its concentration in the organic phase is at least 2·5 × 10?4 M . It seems that the interfacial adsorption of pyridine carboxylates and of 4-octylphenylamine is not the decisive phenomenon in palladium(II) extraction. The negligible protonation of the pyridine-type extractants and the phase transfer catalysis explains well the quick extraction of palladium(II) with the commercial and highly hydrophobic extractant ACORGA CLX-50. 相似文献
100.
Jerzy Stangierski Jan Zabielski Jacek Kijowski 《European Food Research and Technology》2007,226(1-2):233-237
The effect of addition of 3 g/L of commercially available transglutaminase preparation to protein extracts obtained from mechanically
recovered poultry meat was studied. The content of free thiol groups (–SH), thermal drip and gel texture were determined.
After pre-incubation at 7–8 °C for 1, 3, 5 and 24 h, the samples were subjected to one-step heating at 50, 60, 70 and 80 °C
and two-step heating at 50/80, 55/80 and 60/80 °C. The addition of preparation and the extension of pre-incubation time led
to decrease of free -SH groups content. After heating, the number of thiol groups decreased, the texture was improved, but
thermal drip from gels increased. The amount of –SH groups in gel extracts subjected to one-step heating decreased with simultaneous
increase of mechanical strength of gels. Protein gels subjected to two-step heating exhibited higher firmness than gels subjected
to one-step heating. Thus, the 3 g/L addition of transglutaminase preparation in combination with one-step thermal processing
at 70 °C and pre-incubation for 3 h contributed to improvement of texture properties of model gels and low thermal drip. 相似文献