全文获取类型
收费全文 | 457544篇 |
免费 | 5226篇 |
国内免费 | 1601篇 |
专业分类
化学 | 252559篇 |
晶体学 | 6841篇 |
力学 | 18982篇 |
综合类 | 11篇 |
数学 | 51625篇 |
物理学 | 134353篇 |
出版年
2018年 | 2975篇 |
2016年 | 5686篇 |
2015年 | 4539篇 |
2014年 | 6260篇 |
2013年 | 19947篇 |
2012年 | 14405篇 |
2011年 | 18018篇 |
2010年 | 11478篇 |
2009年 | 11345篇 |
2008年 | 16555篇 |
2007年 | 16908篇 |
2006年 | 16234篇 |
2005年 | 14842篇 |
2004年 | 13415篇 |
2003年 | 11902篇 |
2002年 | 11721篇 |
2001年 | 13842篇 |
2000年 | 10632篇 |
1999年 | 8508篇 |
1998年 | 6797篇 |
1997年 | 6670篇 |
1996年 | 6704篇 |
1995年 | 6129篇 |
1994年 | 5872篇 |
1993年 | 5566篇 |
1992年 | 6420篇 |
1991年 | 6165篇 |
1990年 | 5858篇 |
1989年 | 5757篇 |
1988年 | 5946篇 |
1987年 | 5692篇 |
1986年 | 5441篇 |
1985年 | 7676篇 |
1984年 | 7773篇 |
1983年 | 6383篇 |
1982年 | 6822篇 |
1981年 | 6828篇 |
1980年 | 6483篇 |
1979年 | 6755篇 |
1978年 | 6933篇 |
1977年 | 6821篇 |
1976年 | 6713篇 |
1975年 | 6491篇 |
1974年 | 6294篇 |
1973年 | 6473篇 |
1972年 | 3924篇 |
1971年 | 3035篇 |
1968年 | 3377篇 |
1967年 | 3279篇 |
1966年 | 2990篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
111.
112.
In recent years there has emerged significant interest in low pressure radio frequency (rf) glow discharges which are used widely particulary in IC fabrication. Various parameters of the rf glow discharge have been found to be useful for its electrical characterization; however, there is no uniformity and agreement. Extensive experimental investigations on various discharge systems have shown, that the self-bias on the rf driven electrode, the complex conductivity and the breakdown characteristic are preferable parameters of rf discharges. Advantageously the self-bias and the complex conductivity should be presented in dependence on the pressure and the applied rf voltage. The discharge current cannot be measured quite accurately due to currents via leaky capacitors and the deviations from a sinusoidal form of the current due to nonlinearities. 相似文献
113.
In this paper, we study the consistency of a variant of fractionalstep Runge–Kutta methods. These methods are designed tointegrate efficiently semi-linear multidimensional parabolicproblems by means of linearly implicit time integration processes.Such time discretization procedures are also related to a splittingof the space differential operator (or the spatial discretizationof it) as a sum of simpler linear differentialoperators and a nonlinear term. 相似文献
114.
Rare earths exhibit complex magnetic phase diagrams resulting from the competition between various contributions to the magnetic
energy: exchange, anisotropy and magnetostriction. The epitaxy of a rare-earth film on a substrate induces (i) a clamping
to the substrate and (ii) pseudomorphic strains. Both these effects are shown to lead to modifications of the magnetic properties
in (0 0 1)Dy, (0 0 1)Tb and (1 1 0)Eu films. In Dy and Tb films, spectacular variations of the Curie temperature have been
evidenced. Additionally, Tb films exhibit a new large wavelength magnetic modulation. In Eu films, one of the helical magnetic
domains disappears at low temperature whereas the propagation vectors of the other helices are tilted. The link between structural
and magnetic properties is underlined via magnetoelastic models. Moreover, molecular beam epitaxy permits the growth of Sm
in a metastable dhcp phase. The magnetic structure of dhcp Sm has been elucidated for the first time. In this review, neutron
scattering is shown to be a powerful technique to reveal the magnetic structures of rare-earth films. 相似文献
115.
The electro-optic response of ferroelectric smectic C* liquid crystals has been studied. Anomalous switching behaviour of such materials which possess a negative dielectric anisotropy has been reported. These materials show a minimum in response time at a sufficiently high field. We present results showing the dependency of this minimum upon spontaneous polarisation and the effect of AC bias. Calculations based upon the equation of motion of the director around the cone are presented which describe this effect and its dependence on the relative magnitudes of the spontaneous polarization and dielectric anisotropy of the material. Good agreement with the experimental results is found. 相似文献
116.
For fairly high concentrations, the effective arsenic diffusioncoefficient is known to grow linearly with the concentration.In this paper, we consider the strongly enhanced diffusion ofarsenic by asymptotic methods, and extend the results of a previouspaper (King & Please, 1987) in three ways: we characterizean additional (low-concentration) region; we consider the influenceof the initial data; and we consider the case of constant surfaceconcentration. 相似文献
117.
118.
H. Katsurada 《Journal of Number Theory》2004,104(1):100-117
We introduce a formula for the p-adic Siegel-Eisenstein series which demonstrates a connection with the genus theta series and the twisted Eisenstein series with level p. We then prove a generalization of Serre's formula in the elliptic modular case. 相似文献
119.
H. Okumura T. Takahagi N. Nagai S. Shingubara 《Journal of Polymer Science.Polymer Physics》2003,41(17):2071-2078
The structural change in the depth direction of a polyimide (UPILEX‐S) film treated in alkaline solution, which was a representative surface treatment used to form a seed layer for plating and to improve the adhesive strength, was analyzed by means of micro Fourier transform infrared attenuated total reflection (FTIR‐ATR) line analysis with gradient shaving preparation. The polyimide film was treated with KOH. The imide ring opened through the alkaline treatment, and the amide structure and carboxylic acid salt were formed. The attainment depth of this structural change was almost proportional to the treatment time, and it reached about 8 μm after a 30‐min treatment. The degree of structural change through the alkaline treatment was almost constant after it reached a considerably degraded stage, and the chemically changed region penetrated into the inner part of the film from the surface. An intermediate layer before the final degraded stage appeared in the treated layer, and its thickness increased with the treatment time. The region that was changed chemically by the alkaline treatment progressed to the inner part simultaneously and continuously as the treatment time increased. The combined use of gradient shaving preparation and micro FTIR‐ATR line analysis was found to be extremely effective for the depth profiling of organic materials. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2071–2078, 2003 相似文献
120.
S.H Chen 《Journal of luminescence》2004,109(2):93-102
The ZnS:Cu,Al,Au (P22G) phosphor powder was bombarded by an electron beam in an O2 ambient, Ar ambient and other mixture of gases. These gases consisted of mixtures of O2 and COx, and O2, COx and Ar gas. Auger electron spectroscopy (AES) was used to monitor changes in the surface composition of the P22G phosphor during electron bombardment. When the P22G phosphor powder was exposed to the electron beam in a water-rich O2 ambient, a chemically limited ZnO layer was formed on the surface. The electron beam degradation of the P22G phosphor powder was also performed in a dry O2 ambient and a layer of ZnSO4 was formed on the surface. The ZnSO4 formation decayed exponentially with time and it is postulated that this was due to the diffusion of the charge reactants through the ZnSO4 film to the reaction interfaces. The P22G phosphor exposed to the electron beam in an Ar ambient and to the other gas mixtures degraded at a lower rate than in the case of the O2 ambient. This suggests that Ar and COx may suppress the degradation of the P22G phosphor powder. 相似文献