全文获取类型
收费全文 | 399293篇 |
免费 | 4743篇 |
国内免费 | 1454篇 |
专业分类
化学 | 218434篇 |
晶体学 | 5823篇 |
力学 | 16556篇 |
综合类 | 12篇 |
数学 | 46201篇 |
物理学 | 118464篇 |
出版年
2020年 | 2462篇 |
2019年 | 2405篇 |
2018年 | 2421篇 |
2016年 | 4758篇 |
2015年 | 3954篇 |
2014年 | 5375篇 |
2013年 | 17285篇 |
2012年 | 12931篇 |
2011年 | 16219篇 |
2010年 | 10060篇 |
2009年 | 9907篇 |
2008年 | 14897篇 |
2007年 | 15153篇 |
2006年 | 14837篇 |
2005年 | 13736篇 |
2004年 | 12316篇 |
2003年 | 10928篇 |
2002年 | 10689篇 |
2001年 | 12167篇 |
2000年 | 9378篇 |
1999年 | 7504篇 |
1998年 | 6153篇 |
1997年 | 5975篇 |
1996年 | 5986篇 |
1995年 | 5553篇 |
1994年 | 5168篇 |
1993年 | 4981篇 |
1992年 | 5595篇 |
1991年 | 5438篇 |
1990年 | 5088篇 |
1989年 | 4932篇 |
1988年 | 5191篇 |
1987年 | 4918篇 |
1986年 | 4726篇 |
1985年 | 6801篇 |
1984年 | 6927篇 |
1983年 | 5671篇 |
1982年 | 6306篇 |
1981年 | 6206篇 |
1980年 | 5981篇 |
1979年 | 6056篇 |
1978年 | 6201篇 |
1977年 | 6115篇 |
1976年 | 6084篇 |
1975年 | 5913篇 |
1974年 | 5647篇 |
1973年 | 5918篇 |
1972年 | 3496篇 |
1971年 | 2627篇 |
1968年 | 2577篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Lerner E.J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1989,17(2):259-263
A cosmological model is presented that produces He, C, O, D, Li, Be, and B in their observed abundances without a Big Bang. The elements are produced during the 1.5-Gy formation period of a galaxy, with C, O, and other heavy elements produced by stars of M >12 M3 , He by stars of 6 Ms<M <12 Ms, and D, Li, Be, and B by cosmic-ray reactions in a nearly pure H plasma halo. Thus, the model shows that the major elements used in astrophysical studies can be produced during galactic formation by exactly the same processes known to function today at much lower rates 相似文献
93.
N. Monnanteuil J.M. Colmont 《Journal of Quantitative Spectroscopy & Radiative Transfer》1983,29(2):131-136
Self broadened widths of seven lines of ozone between 75 and 120 GHz have been measured at room temperature. The variation with temperature of the self-broadening parameter for three of these lines has been studied in the range 245–292°K. 相似文献
94.
We discuss some variant superfield representations which can arise by the replacement of some of the usual fields in a multiplet with p-form gauge fields. 相似文献
95.
96.
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
97.
Daniel W. Stroock 《Journal of Functional Analysis》2007,242(1):295-303
The purpose of this note is to describe a procedure for transferring familiar estimates for transition probabilities on RN to transition probabilities on compact manifolds. 相似文献
98.
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
99.
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
100.
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