全文获取类型
收费全文 | 1314篇 |
免费 | 25篇 |
国内免费 | 6篇 |
专业分类
化学 | 764篇 |
晶体学 | 17篇 |
力学 | 75篇 |
数学 | 122篇 |
物理学 | 367篇 |
出版年
2023年 | 11篇 |
2022年 | 14篇 |
2021年 | 21篇 |
2020年 | 22篇 |
2019年 | 23篇 |
2018年 | 18篇 |
2017年 | 30篇 |
2016年 | 32篇 |
2015年 | 22篇 |
2014年 | 36篇 |
2013年 | 82篇 |
2012年 | 82篇 |
2011年 | 66篇 |
2010年 | 55篇 |
2009年 | 51篇 |
2008年 | 69篇 |
2007年 | 52篇 |
2006年 | 43篇 |
2005年 | 48篇 |
2004年 | 36篇 |
2003年 | 36篇 |
2002年 | 23篇 |
2001年 | 9篇 |
2000年 | 17篇 |
1999年 | 14篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 15篇 |
1995年 | 16篇 |
1994年 | 20篇 |
1993年 | 13篇 |
1992年 | 12篇 |
1991年 | 13篇 |
1990年 | 14篇 |
1989年 | 19篇 |
1988年 | 11篇 |
1986年 | 9篇 |
1985年 | 12篇 |
1984年 | 18篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1976年 | 14篇 |
1975年 | 14篇 |
1974年 | 10篇 |
1936年 | 13篇 |
排序方式: 共有1345条查询结果,搜索用时 15 毫秒
1.
In the present paper, a new two-parameter inverted equation of state (EOS) is developed which is found to be working very
well in the high-pressure region. To check its success and validity, this EOS has been applied in a number of solids. The
computed volume compression is found to be in very good agreement with the experimental data in the whole range of pressure
in all the solids. The minimum and the maximum pressure range used in the present study is 0–320 kbar and 0–3000 kbar, respectively. 相似文献
2.
C.P. Paul P. Ganesh S.K. Mishra P. Bhargava J. Negi A.K. Nath 《Optics & Laser Technology》2007,39(4):800-805
This paper presents an investigation of laser rapid manufacturing (LRM) for Inconel-625 components. LRM is an upcoming rapid manufacturing technology, it is similar to laser cladding at process level with different end applications. In general, laser-cladding technique is used to deposit materials on the substrate either to improve the surface properties or to refurbish the worn out parts, while LRM is capable of near-net shaping the components by layer-by-layer deposition of the material directly from CAD model. In the present study, a high-power continuous wave (CW) CO2 laser system, integrated with a co-axial powder-feeding system and a three-axis workstation were used. The effect of processing parameters during LRM of Inconel-625 was studied and the optimum set of parameters for the maximum deposition rate was established employing Orthogonal L9 array of Taguchi technique. Results indicated that the powder feed rate and the scan speed contributed about 56% and 26%, respectively to the deposition rate, while the influence of laser power was limited to 10% only. Fabricated components were subjected to non-destructive testing (like—ultrasonic testing, dye-penetrant testing), tensile testing, impact testing, metallographic examinations and micro-hardness measurement. The test results revealed defect-free material deposition with improved mechanical strength without sacrificing the ductility. 相似文献
3.
4.
In this paper, we study cyclic codes detecting a subclass of close-closed loop bursts viz. low-density close-closed loop bursts. A sub-class of CT close-closed loop bursts called CT low-density close-closed loop bursts is also studied. 相似文献
5.
We have determined the various parameters of the electric field gradient (EFG) for different Fe-oxygen configurations. This was achieved by analyses of a variety of spectra using a procedure which allows fitting of all spectra of oriented 1-2-3 compounds obtained at different tilt angles β simultaneously, taking into account the degree of texture. The use of a point charge model is invalidated because of the high degree of estimated covalence. The Mössbauer parameters are rationalized. The absence of any observed anisotropy of the mean square displacement of the dopant at the Cu(1) site is rather intriguing. 相似文献
6.
7.
A textured pellet of YBa2Cu3O7?δ was prepared and doped with57Co. After subsequent heat treatments the cobalt was found at the two copper sites. The degree of alignment of individual crystallites (about 40%) was determined from the Mössbauer spectrum by using a method developed by the authors [1]. The same method showed that the most characteristic doublet component of such spectra (δ=0.08 mm/s; |ΔE Q|=1.96 mm/s) is associated with a site, most probably a Cu(1) site, where the EFG is parallel to thec direction of the unit cell. The sign ofV zz turned out to be negative, giving a negative quadrupole splitting (ΔE Q=?1.96 mm/s) for that component. 相似文献
8.
Transverse flow transversely excited (TFTE) CO2 lasers are easily scalable to multikilowatt level. The laser power can be scaled up by increasing the volumetric gas flow
and discharge volume. It was observed in a TFTE CW CO2 laser having single row of pins as an anode and tubular cathode that the laser power was not increasing when the discharge
volume and the gas volumetric flow were increased by increasing the electrode separation keeping the gas flow velocity constant.
The discharge voltage too remained almost constant with the change of electrode separation at the same gas flow velocity.
This necessitated revision of the scaling laws for designing this type of high power CO2 laser. Experimental results of laser performance for different electrode separations are discussed and the modifications
in the scaling laws are presented. 相似文献
9.
An explicit expression has been derived for the volume dependence of electron-phonon coupling strength () by using a recently proposed quadratic form of the screened pseudopotential and by considering the variation of Fermi momentum with volume. Variation of Coulomb pseudopotential (
*) has also been explicitly considered by varying the Fermi momentum. Dependence of transition temperatureT
c
and the logarithm of the effective interaction strength (N
0
V) on the volume has been studied for eight nontransition metallic superconductors. A linear drop inT
c
for small values of (–/
0) as well as the calculated values of= InN
0
V/ In, exhibits better matching with the experimental data, as compared to the earlier theoretical results. 相似文献
10.