全文获取类型
收费全文 | 5858篇 |
免费 | 251篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 53篇 |
综合类 | 23篇 |
化学工业 | 1143篇 |
金属工艺 | 90篇 |
机械仪表 | 127篇 |
建筑科学 | 301篇 |
矿业工程 | 10篇 |
能源动力 | 230篇 |
轻工业 | 375篇 |
水利工程 | 57篇 |
石油天然气 | 31篇 |
无线电 | 528篇 |
一般工业技术 | 1176篇 |
冶金工业 | 849篇 |
原子能技术 | 46篇 |
自动化技术 | 1091篇 |
出版年
2023年 | 56篇 |
2022年 | 115篇 |
2021年 | 184篇 |
2020年 | 130篇 |
2019年 | 175篇 |
2018年 | 211篇 |
2017年 | 137篇 |
2016年 | 163篇 |
2015年 | 133篇 |
2014年 | 195篇 |
2013年 | 353篇 |
2012年 | 312篇 |
2011年 | 348篇 |
2010年 | 255篇 |
2009年 | 262篇 |
2008年 | 272篇 |
2007年 | 275篇 |
2006年 | 204篇 |
2005年 | 197篇 |
2004年 | 168篇 |
2003年 | 173篇 |
2002年 | 144篇 |
2001年 | 85篇 |
2000年 | 99篇 |
1999年 | 73篇 |
1998年 | 239篇 |
1997年 | 162篇 |
1996年 | 104篇 |
1995年 | 108篇 |
1994年 | 83篇 |
1993年 | 73篇 |
1992年 | 63篇 |
1991年 | 46篇 |
1990年 | 37篇 |
1989年 | 35篇 |
1988年 | 41篇 |
1987年 | 34篇 |
1986年 | 23篇 |
1985年 | 30篇 |
1984年 | 20篇 |
1983年 | 18篇 |
1982年 | 25篇 |
1981年 | 30篇 |
1980年 | 22篇 |
1979年 | 22篇 |
1978年 | 17篇 |
1977年 | 26篇 |
1976年 | 45篇 |
1975年 | 14篇 |
1972年 | 13篇 |
排序方式: 共有6130条查询结果,搜索用时 15 毫秒
121.
Hugo Durou David Pech David Colin Patrice Simon Pierre-Louis Taberna Magali Brunet 《Microsystem Technologies》2012,18(4):467-473
In this paper a wafer-level process is proposed to fully integrate carbon-based micro-supercapacitor onto silicon substrate.
This process relies on the deposition of a paste containing carbon, PVDF and acetone into cavities etched in silicon. After
electrolyte deposition in a controlled atmosphere, a wafer-level encapsulation is realized. Cyclic voltammetry performed on
non-encapsulated micro-components showed specific energy of 257 mJ cm−2 for 336 μm deep cavities. The specific encapsulation process developed was tested separately and proved to be efficient in
terms of resistance to organic electrolytes and mechanical strength. 相似文献
122.
Stochastic distribution of the required coefficient of friction for level walking--an in-depth study
This study investigated the stochastic distribution of the required coefficient of friction (RCOF) which is a critical element for estimating slip probability. Fifty participants walked under four walking conditions. The results of the Kolmogorov-Smirnov two-sample test indicate that 76% of the RCOF data showed a difference in distribution between both feet for the same participant under each walking condition; the data from both feet were kept separate. The results of the Kolmogorov-Smirnov goodness-of-fit test indicate that most of the distribution of the RCOF appears to have a good match with the normal (85.5%), log-normal (84.5%) and Weibull distributions (81.5%). However, approximately 7.75% of the cases did not have a match with any of these distributions. It is reasonable to use the normal distribution for representation of the RCOF distribution due to its simplicity and familiarity, but each foot had a different distribution from the other foot in 76% of cases. PRACTITIONER SUMMARY: The stochastic distribution of the required coefficient of friction (RCOF) was investigated for use in a statistical model to improve the estimate of slip probability in risk assessment. The results indicate that 85.5% of the distribution of the RCOF appears to have a good match with the normal distribution. 相似文献
123.
Angelika Ziegler Sybil M. Macintosh Lesley Torrance William Simon Antony R. Slabas 《Lipids》1997,32(8):805-809
Purified Brassica napus enoyl acyl carrier protein reductase (ENR) was used to select specific antibodies from a library of antibody fragments, single-chain
Fv (scFv), displayed on filamentous phage. Analysis of the selected clones by BstNl fingerprinting and nucleotide sequencing showed that the scFv were derived from three different human VH germline genes. The binding specificities were confirmed by Western blots and ELISA. The scFv preparations reacted with B. napus ENR, but not with β-keto reductase, nor enoyl reductase from Escherichia coli. Analysis of fragments generated by CNBr treatment indicates that the scFv 3.13 recognizes an epitope located within the n-terminal 80 amino acids of the enzyme molecule. The scFv were used to detect ENR directly in extracts of B. napus seeds. 相似文献
124.
125.
Simon Shawe Fraser Buchanan Eileen Harkin-Jones David Farrar 《Journal of Materials Science》2006,41(15):4832-4838
As part of a study to characterise bioabsorbable scaffolds for tissue engineering an investigation has been conducted into the rate of degradation of polyglycolic acid (PGA). This is one of the most commonly used bioabsorbable materials and has been used in sutures since the 60s and more recently in cell scaffolds, drug delivery devices and bone fixation pins. This study looks at the influence that surface-to-volume ratio i.e. thickness of material, has on degradation. By degrading various thicknesses of PGA in a buffer saline solution over 24 days and testing their properties at regular intervals, a knowledge of how surface-to-volume ratio affects degradation was developed. Properties such as weight loss, crystallinity, molecular weight and structural integrity were measured. Results showed that rate of mass loss was dependent on sample thickness but crystallinity, melting point and molecular weight were independent of thickness. 相似文献
126.
El-Hag A.H. Simon L.C. Jayaram S.H. Cherney E.A. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2006,13(1):122-128
The paper presents the experimental results obtained on the erosion resistance of silicone rubber (SIR) filled with 12 nm size fumed silica (nano filler) to those filled with 5 /spl mu/m size silica filler (micro filler). The ASTM 2303 inclined plane tracking and erosion test was used in the comparison as well as an infrared laser as the source of heat to erode the SIR samples. The erosion resistance of the SIR materials increased with increasing percentage of the fillers, and it was observed that 10% by weight of nano-filled SIR gives a performance that is similar to that obtained with 50% by weight of micro-filled SIR. The low frequency components of leakage current and the eroded mass are used to evaluate the relative erosion resistance of the composites and the third harmonic component of the leakage current shows good correlation to the measured eroded mass. The paper discusses the possible reasons for the improvement in the erosion resistance of nano-filled silicone composites. 相似文献
127.
K. Lee P. Henry Simon Fleming J.L. Blows 《Photonics Technology Letters, IEEE》2006,18(8):914-916
One hundred twenty meters of fiber with an internal codrawn wire and electrically conductive coating was successfully fabricated for the first time. The integration of the conductive coating and wire was all performed during the fiber draw stage, in a process that enabled arbitrarily long lengths of fiber to be made. The wire combined with the conductive coating enables a strong electric field to be formed across the optical core. Such a fiber is ideal for thermally poling long lengths and for nonlinear device applications such as optical switches and modulators. 相似文献
128.
Comparisons of computed mobile phone induced SAR in the SAM phantom to that in anatomically correct models of the human head 总被引:1,自引:0,他引:1
Beard B.B. Kainz W. Onishi T. Iyama T. Watanabe S. Fujiwara O. Jianqing Wang Bit-Babik G. Faraone A. Wiart J. Christ A. Kuster N. Ae-Kyoung Lee Kroeze H. Siegbahn M. Keshvari J. Abrishamkar H. Simon W. Manteuffel D. Nikoloski N. 《Electromagnetic Compatibility, IEEE Transactions on》2006,48(2):397-407
The specific absorption rates (SAR) determined computationally in the specific anthropomorphic mannequin (SAM) and anatomically correct models of the human head when exposed to a mobile phone model are compared as part of a study organized by IEEE Standards Coordinating Committee 34, Sub-Committee 2, and Working Group 2, and carried out by an international task force comprising 14 government, academic, and industrial research institutions. The detailed study protocol defined the computational head and mobile phone models. The participants used different finite-difference time-domain software and independently positioned the mobile phone and head models in accordance with the protocol. The results show that when the pinna SAR is calculated separately from the head SAR, SAM produced a higher SAR in the head than the anatomically correct head models. Also the larger (adult) head produced a statistically significant higher peak SAR for both the 1- and 10-g averages than did the smaller (child) head for all conditions of frequency and position. 相似文献
129.
Moustakas A.L. Simon S.H. Marzetta T.L. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2006,52(8):3622-3634
Differential unitary space-time modulation (DUSTM) and its earlier nondifferential counterpart, USTM, permit high-throughput multiple-input multiple-output (MIMO) communication entirely without the possession of channel state information by either the transmitter or the receiver. For an isotropically random unitary input we obtain the exact closed-form expression for the probability density of the DUSTM received signal, permitting the straightforward Monte Carlo evaluation of its mutual information. We compare the performance of DUSTM and USTM through both numerical computations of mutual information and through the analysis of low- and high-signal-to-noise ratio (SNR) asymptotic expressions. In our comparisons the symbol durations of the equivalent unitary space-time signals are equal to T. For DUSTM the number of transmit antennas is constrained by the scheme to be M=T/2, while USTM has no such constraint. If DUSTM and USTM utilize the same number of transmit antennas at high SNRs the normalized mutual information of the two schemes expressed in bits/s/Hz are asymptotically equal, with the differential scheme performing somewhat better. At low SNRs the normalized mutual information of DUSTM is asymptotically twice the normalized mutual information of USTM. If, instead, USTM utilizes the optimum number of transmit antennas then USTM can outperform DUSTM at sufficiently low SNRs 相似文献
130.
The lead free Sn–Ag–y%Cu (y = 0.0, 0.5, 1.0 and 2.0) interconnect interfacial microstructures and the microstructure evolution under thermal treatment (isothermal aging, 150 °C/1000 h) were studied in detail by using surface microetching microscopy and cross section microscopy. The corresponding mechanical and reliability behaviors were evaluated by performing shear test and fracture mode analysis before and after the thermal treatment. The results indicate: (i) The interconnects could have different microstructures and intermetallic compound (IMC), depending on the Cu content. The Cu–Sn IMC could have microstructures that were clusters or protrusion-like, Augustine grass leaf-like, scissor-like, tweezers-like, etc. (ii) Ag3Sn IMCs were not observed at time zero for any interconnect groups, but they occurred after the aging for all groups. The Ag3Sn IMC could have different microstructures, again depending on Cu content. For low Cu content, the Ag3Sn IMCs were granules or nodules; for higher Cu content, Ag3Sn IMCs were plate-like. (iii) The growth of Ag3Sn plates was promoted by the growth of Cu–Sn IMCs, but indirectly linked to the Cu content. (iv) High Cu content (1.0 wt% and higher) could degrade the mechanical and reliability performances of the LF interconnect by providing a brittle joint, which was mainly achieved through the substantial growth of Cu–Sn IMCs and Ag3Sn plates. 相似文献