全文获取类型
收费全文 | 83883篇 |
免费 | 410篇 |
国内免费 | 67篇 |
专业分类
电工技术 | 1901篇 |
综合类 | 97篇 |
化学工业 | 10952篇 |
金属工艺 | 7266篇 |
机械仪表 | 6181篇 |
建筑科学 | 1555篇 |
矿业工程 | 817篇 |
能源动力 | 946篇 |
轻工业 | 1562篇 |
水利工程 | 1211篇 |
石油天然气 | 1553篇 |
无线电 | 8138篇 |
一般工业技术 | 21957篇 |
冶金工业 | 6525篇 |
原子能技术 | 1158篇 |
自动化技术 | 12541篇 |
出版年
2023年 | 85篇 |
2022年 | 154篇 |
2021年 | 259篇 |
2020年 | 169篇 |
2019年 | 148篇 |
2018年 | 9472篇 |
2017年 | 10134篇 |
2016年 | 5343篇 |
2015年 | 710篇 |
2014年 | 270篇 |
2013年 | 299篇 |
2012年 | 3072篇 |
2011年 | 9371篇 |
2010年 | 8932篇 |
2009年 | 7601篇 |
2008年 | 7279篇 |
2007年 | 9542篇 |
2006年 | 157篇 |
2005年 | 4090篇 |
2004年 | 2294篇 |
2003年 | 1886篇 |
2002年 | 762篇 |
2001年 | 87篇 |
2000年 | 171篇 |
1999年 | 41篇 |
1998年 | 33篇 |
1997年 | 33篇 |
1996年 | 29篇 |
1995年 | 30篇 |
1994年 | 42篇 |
1993年 | 41篇 |
1992年 | 23篇 |
1991年 | 36篇 |
1969年 | 56篇 |
1968年 | 129篇 |
1967年 | 117篇 |
1966年 | 144篇 |
1965年 | 123篇 |
1964年 | 80篇 |
1963年 | 64篇 |
1962年 | 66篇 |
1961年 | 71篇 |
1960年 | 89篇 |
1959年 | 62篇 |
1958年 | 76篇 |
1957年 | 128篇 |
1956年 | 119篇 |
1955年 | 139篇 |
1954年 | 153篇 |
1951年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
The stability of the reactive interface during the solid-state displacement reaction, Cu2O+Co1−X
Fe
X
=2Cu+(Co1−X
Fe
X
)O, is studied as a function of Co-Fe alloy composition at 1223 K. For X≤0.03, the reaction zone has a layered structure, and the cation diffusion in (Co, Fe)O is the rate-limiting step. The interface
is unstable in the early stages of the reaction; the instability decreases with time as the oxide thickness increases, and
the interface becomes planar at long times. The time required for the attainment of interface planarity increases with the
value of X. The reaction kinetics are consistent with the available cation-diffusion data in (Co, Fe)O. For X≥0.045, the product zone is a composite of Cu+(Co, Fe)O, and the rate is limited by the oxygen transport in copper. The transition
to interface instability occurs when the oxide can support a cation flux that exceeds the maximum possible oxygen flux in
copper. During the reaction, composition gradients develop in (Co, Fe)O because of higher diffusion rates for iron than for
cobalt. 相似文献
83.
Validity on the well-known Onsager reciprocal relations L 12=L 21 is verified in the kinetic theory of gases taking into account mass and heat transfer near the surface. Using an analytical solution to the ellipsoidal statistical equation (providing for the true Prandtl number), it is demonstrated that the Onsager relations are obeyed, at least to within exponential corrections of the type exp(−1/Kn) in the Knudsen number. 相似文献
84.
85.
The physical gestures that operate music instruments are responsible for the qualities of the sound being produced in a performance.
Gestural information is thereby crucial for a model of music performance, paired with a model of sound synthesis where this
information is applied. The highly constrained nature of performers gestures makes this task suitable to be modeled via a
constraint-based approach, coupled with a strategy aimed at maximizing the gestural comfort of performers. We illustrate the
problem representation, the search strategy and a validation of the model against human performance. 相似文献
86.
Structural engineers use design codes formulated to consider uncertainty for both reinforced concrete and structural steel
design. For a simple one-bay structural steel frame, we survey typical uncertainties and compute an interval solution for
displacements and forces. The naive solutions have large over-estimations, so we explore the Mullen-Muhanna assembly strategy,
scaling, and constraint propagation to achieve tight enclosures of the true ranges for displacements and forces in a fraction
of the CPU time typically used for simulations. That we compute tight enclosures, even for large parameter uncertainties used
in practice, suggests the promise of interval methods for much larger structures. 相似文献
87.
N. Roussel S. Staquet L. D’Aloia Schwarzentruber R. Le Roy F. Toutlemonde 《Materials and Structures》2007,40(9):877-887
Casting simulations of self-compacting concrete are carried out in order to obtain a value of the minimum fluidity needed to cast a VHPC precambered composite beam. The mix proportioning of the concrete takes into account this minimum value. The numerical predictions are finally compared with the experimental observations during two casting tests and the real casting of the two 13 m beams. Although the simplifying assumptions needed to carry out the simulations are numerous, there is an agreement between the predictions and the real casting. 相似文献
88.
H. Furuse N. Mori H. Kubo H. Momose M. Kondow 《Journal of Materials Science: Materials in Electronics》2007,18(1):81-85
We have measured optical transmittance through germanium in the mid-infrared region at room temperature using the Osaka free-electron laser (FEL). In spite of the fact that germanium is transparent in the mid-infrared region, we observed strong suppression of optical transmission under high-intensity FEL excitation. We found that the observed suppression is due to optical absorption in germanium. To analyze the experimental results, we have calculated optical transmittance of germanium within Keldysh theory 相似文献
89.
It is established that the capillary rise of a liquid has an oscillatory character, in contrast to the commonly accepted opinion that a vertical capillary is filled at a monotonically varying velocity. The value of the tangential shear stress arising in an ascending liquid is evaluated for ethyl alcohol and distilled water. 相似文献
90.
A. M. Kut’in V. S. Polyakov M. F. Churbanov G. E. Snopatin 《Inorganic Materials》2007,43(9):1018-1023
Using a flow method, we have measured the vapor pressure of tellurium tetraiodide, an attractive reagent for chemical vapor deposition technology. The results, combined with earlier tensimetric data, have been used to evaluate the basic thermodynamic functions of TeI4 and its thermolysis products. 相似文献