全文获取类型
收费全文 | 2096篇 |
免费 | 68篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 37篇 |
综合类 | 3篇 |
化学工业 | 399篇 |
金属工艺 | 49篇 |
机械仪表 | 54篇 |
建筑科学 | 36篇 |
矿业工程 | 3篇 |
能源动力 | 102篇 |
轻工业 | 90篇 |
水利工程 | 5篇 |
石油天然气 | 16篇 |
无线电 | 346篇 |
一般工业技术 | 473篇 |
冶金工业 | 296篇 |
原子能技术 | 20篇 |
自动化技术 | 245篇 |
出版年
2023年 | 22篇 |
2022年 | 39篇 |
2021年 | 55篇 |
2020年 | 49篇 |
2019年 | 42篇 |
2018年 | 71篇 |
2017年 | 64篇 |
2016年 | 53篇 |
2015年 | 32篇 |
2014年 | 72篇 |
2013年 | 150篇 |
2012年 | 101篇 |
2011年 | 99篇 |
2010年 | 75篇 |
2009年 | 86篇 |
2008年 | 74篇 |
2007年 | 89篇 |
2006年 | 65篇 |
2005年 | 42篇 |
2004年 | 46篇 |
2003年 | 45篇 |
2002年 | 52篇 |
2001年 | 32篇 |
2000年 | 31篇 |
1999年 | 39篇 |
1998年 | 97篇 |
1997年 | 60篇 |
1996年 | 54篇 |
1995年 | 52篇 |
1994年 | 39篇 |
1993年 | 30篇 |
1992年 | 32篇 |
1991年 | 27篇 |
1990年 | 28篇 |
1989年 | 17篇 |
1988年 | 25篇 |
1987年 | 10篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 15篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 5篇 |
1979年 | 16篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1976年 | 20篇 |
1975年 | 6篇 |
1973年 | 11篇 |
排序方式: 共有2174条查询结果,搜索用时 46 毫秒
11.
12.
TiN---Au films with multiple intermediate layers deposited by r.f. sputtering are suggested as a solution to the problem of adhesion of gold films to TiN coatings. Their optical and mechanical properties are investigated and compared with those of conventional electroplated gold films. Various analysis techniques have been used: Auger electron spectroscopy to determine the composition profiles, the direct tensile test for adhesion characteristics, optical rub test for scratch characteristics, salt spray test for corrosion characteristics and the selected ordinate method to identify the color of resultant films. It is shown that poor adhesion of gold films of TiN coatings can be overcome. Resultant multilayered TiN---Au films show the same color as that of commercially available electroplated gold films and their reflectivity reaches 98% of that of gold films over the wavelength range studied. For further applications, electrical properties of multilayered TiN---Au have also been studied. The sheet resistance of these TiN---Au films on n-Si and p-Si is in the range 0.54ω/□–6.12ω/□. Thus these multilayered structures may be used as durable contacts for microelectronic applications. 相似文献
13.
J. R. Banerjee S. A. Fisher 《International journal for numerical methods in engineering》1992,33(4):739-751
Analytical expressions for the coupled bending–torsional dynamic stiffness matrix elements of an axially loaded uniform beam element are derived in an exact sense by solving the governing differential equations of motion of the beam. The influence of axial force on the coupled bending–torsional frequencies of a cantilever and hinged–hinged beam of thin-walled section is demonstrated by numerical results. Application of the developed theory includes coupled bending–torsional frequency and mode calculations of helicopter, turbine and propeller blades, plane and space frames, and grillages consisting of axially loaded beam elements with non-coincident mass centre and shear centre. 相似文献
14.
Shubneesh Batra Nanseng Jeng Akif Sultan Kyle Picone Surya Bhattacharya Keun-Hyung Park Sanjay Banerjee David Kao Monte Manning Chuck Dennison 《Journal of Electronic Materials》1993,22(5):551-554
When dopants are indiffused from a heavily implanted polycrystalline silicon film deposited on a silicon substrate, high thermal
budget annealing can cause the interfacial “native” oxide at the polycrystalline silicon-single crystal silicon interface
to break up into oxide clusters, causing epitaxial realignment of the polycrystalline silicon layer with respect to the silicon
substrate. Anomalous transient enhanced diffusion occurs during epitaxial realignment and this has adverse effects on the
leakage characteristics of the shallow junctions formed in the silicon substrate using this technique. The degradation in
the leakage current is mainly due to increased generation-recombination in the depletion region because of defect injection
from the interface. 相似文献
15.
D. P. Henry P. K. Banerjee 《International journal for numerical methods in engineering》1991,31(2):369-384
An advanced level development of the boundary element method is presented for the elastic stress analysis of a three-dimensional solid containing a large number of small diameter, tubular shaped holes. The formulation has been developed such that these holes can be modelled by a system of curvilinear line elements, resulting in substantial savings in both data preparation and computing costs. This is accomplished by assuming a variation in the displacement field along the circumference defined in terms of trigonometric functions together with a linear or quadratic variation of displacements along the longitudinal direction. 相似文献
16.
Indranil Roy Manish Chauhan Farghalli A. Mohamed Enrique J. Lavernia 《Metallurgical and Materials Transactions A》2006,37(3):721-730
Thermal stability in bulk ultrafine-grained (UFG) 5083 Al that was processed by gas atomization followed by cryomilling, consolidation,
and extrusion, and that exhibited an average grain size of 305 nm, was investigated in the temperature range of 473 to 673
K (0.55 to 0.79 T
m
, where T
m
is the melting temperature of the material) for different annealing times. Appreciable grain growth was observed at temperatures
> 573 K, whereas there was limited grain growth at temperatures < 573 K even after long annealing times. The values of the
grain growth exponent, n, deduced from the grain growth data were higher than the value of 2 predicted from elementary grain growth theories. The
discrepancy was attributed to the operation of strong pinning forces on boundaries during the annealing treatment. An examination
of the microstructure of the alloy suggests that the origin of the pinning forces is most likely related to the presence of
dispersion particles, which are mostly introduced during cryomilling. Two-grain growth regimes were identified: the low-temperature
region (<573 K) and the high-temperature region (>573 K). For temperatures lower than 573 K, the activation energy of 25 ±
5 kJ/mol was determined. It is suggested that this low activation energy represents the energy for the reordering of grain
boundaries in the UFG material. For temperatures higher than 573 K, an activation energy of 124 ± 5 kJ/mol was measured. This
value of activation energy, 124 ± 5 kJ/mol, lies between that for grain boundary diffusion and lattice diffusion in analogous
aluminum polycrystalline systems. The results show that the strength and ductility of bulk UFG 5083 Al, as obtained from tensile
tests, correlate well with substructural changes introduced in the alloy by the annealing treatment. 相似文献
17.
A. Deb P. K. Banerjee 《International journal for numerical methods in engineering》1989,28(7):1539-1555
A comparison between a family of isoparametric C°-continucus elements in the context of two-dimensional elastostatics using the direct boundary element method is presented. The elements studied use Lagrangian shape functions of orders quadratic, cubic and quartic. The relative efficiencies of these elements from the viewpoint of accuracy of solution as well as cost effectiveness are examined through certain selected problems. It emerges from the present study that the quartic element is more reliable in accuracy than the lower members of the family without being necessarily more expensive. 相似文献
18.
H. S. Tripathi B. Mukherjee S. K. Das A. Ghosh G. Banerjee 《Bulletin of Materials Science》2003,26(2):217-220
Mullite was developed by reaction sintering of sillimanite beach sand and calcined alumina. Two varieties of sillimanite beach
sand viz. S and Z having different compositions were selected. Synthesis and properties of mullite were very much dependent
on the sillimanite beach sand composition. Presence of higher amount of impurities in the Z-variety of sillimanite sand favours
the densification by liquid phase formation. Presence of zircon in Z-variety increases the hardness and fracture toughness.
Alumina addition improves the mechanical/thermomechanical properties of the samples. Mullite retains the usual orthorhombic
habit of sillimanite. Rounded to sub rounded zirconia dispersed within the mullite matrix of the sample ZA is noticed. 相似文献
19.
Flooding phenomenon limits the stability and the flow of a liquid film falling along the walls of a channel in which a gas is flowing upwards.As known, the entrainment effect can completely prevent the liquid to fall from its natural flow. The present work proposes a new mechanistic model for the prediction of the onset of flooding in vertical and inclined pipes in the presence of obstructions, as well as taking into account the viscosity effect. The good performance of the model in the different geometrical conditions and for variable viscosities of the liquid component assesses the validity of the hypothesis that the instability of a wavelike disturbance limits the countercurrent flow in a channel. 相似文献
20.
Improved genetic algorithm for channel allocation with channel borrowing in mobile computing 总被引:2,自引:0,他引:2
Patra S.S.M. Roy K. Banerjee S. Vidyarthi D.P. 《Mobile Computing, IEEE Transactions on》2006,5(7):884-892
This paper exploits the potential of the Genetic Algorithm to solve the cellular resource allocation problem. When a blocked host is to be allocated to a borrowable channel, a crucial decision is which neighboring cell to choose to borrow a channel. It is an optimization problem and the genetic algorithm is efficiently applied to handle this. The Genetic Algorithm, for this particular problem, is improved by introducing a new genetic operator, named pluck, that incorporates a problem-specific knowledge in population generation and leads to a better channel utilization by reducing the average blocked hosts. The pluck operator makes the crucial decision of when and which cell to borrow with the future consideration that the borrowing should not lead the network to chaos. It makes a channel borrowing decision that minimizes the number of blocked hosts and improves the long-term performance of the network. Efficacy of the proposed method has been evaluated by experimentation. 相似文献