全文获取类型
收费全文 | 3828篇 |
免费 | 417篇 |
国内免费 | 236篇 |
专业分类
化学 | 193篇 |
晶体学 | 9篇 |
力学 | 515篇 |
综合类 | 64篇 |
数学 | 2379篇 |
物理学 | 1321篇 |
出版年
2023年 | 31篇 |
2022年 | 57篇 |
2021年 | 97篇 |
2020年 | 74篇 |
2019年 | 76篇 |
2018年 | 76篇 |
2017年 | 115篇 |
2016年 | 126篇 |
2015年 | 94篇 |
2014年 | 214篇 |
2013年 | 255篇 |
2012年 | 149篇 |
2011年 | 225篇 |
2010年 | 215篇 |
2009年 | 198篇 |
2008年 | 235篇 |
2007年 | 284篇 |
2006年 | 237篇 |
2005年 | 189篇 |
2004年 | 197篇 |
2003年 | 177篇 |
2002年 | 137篇 |
2001年 | 111篇 |
2000年 | 117篇 |
1999年 | 115篇 |
1998年 | 85篇 |
1997年 | 92篇 |
1996年 | 63篇 |
1995年 | 72篇 |
1994年 | 46篇 |
1993年 | 34篇 |
1992年 | 36篇 |
1991年 | 34篇 |
1990年 | 20篇 |
1989年 | 20篇 |
1988年 | 24篇 |
1987年 | 20篇 |
1986年 | 10篇 |
1985年 | 23篇 |
1984年 | 15篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1973年 | 4篇 |
排序方式: 共有4481条查询结果,搜索用时 260 毫秒
951.
952.
Ar辅助确定Al等离子体电子温度 总被引:4,自引:1,他引:3
用Ar气作保护气时 ,Nd :YAG脉冲激光烧蚀Al靶 ,将诱发Ar气电离 ,并产生丰富的Ar离子谱线辐射。文章根据Ar离子谱线辐射信息 ,分析了ArⅡ 385 0 5 7,ArⅡ 386 85 3,ArⅡ 4 0 4 2 91 ,ArⅡ 4 0 7 2 0 1nm等 4条谱线的时间分辨行为 ,计算了Al等离子体的电子温度。结果发现 :Al等离子体的电子温度约 1 5 0 0 0~2 2 0 0 0K ,随延迟时间的增加 ,电子温度单调衰减 相似文献
953.
本考虑了一类索赔发生分别是Poisson过程和Erlang(n)过程的延迟双险种模型,给出了初始女本为u的破产概率ψ(u)表达式. 相似文献
954.
The interacting boson approximation IBA-1 model space, in which neutron and proton degrees of freedom are not distinguished,
can be considered as a subspace of the IBA-2 model space. Using the microscopic background of the IBA-2 model, a correspondence
can be established between IBA-1 and IBA-2 model space. Since the space of the IBA-1 model can be regarded as a subspace of
the IBA-2 model there is a unique way to ‘Project’ the operators of the IBA-2 model onto those of IBA-1. This projection can
be carried out using theF-spin formalism. In the IBA-2 model, the lowest states are indeed fully symmetric, and using the calculations with the help
of this projection, we explore the energy levels and the electric quadrupole transition probabilitiesB(E2; {ie393-01}) and γ-ray E2/M1 mixing ratios for selected transitions of162, 164, 166, 168, 170Er. Owing to admixtures of non-fully-symmetric states in IBA-2, we renormalized the parameters (ε) and (κ). This is the first time we show that this projection can be applied to some heavier isotopes and the results obtained for162, 164, 166, 168, 170Er isotopes are reasonably in good agreement with the previous experimental values. 相似文献
955.
The usual random walk on a group (homogeneous both in time and in space) is determined by a probability measure on the group. In a random walk with random transition probabilities this single measure is replaced with a stationary sequence of measures, so that the resulting (random) Markov chains are still space homogeneous, but no longer time homogeneous. We study various notions of measure theoretical boundaries associated with this model and establish an analogue of the Poisson formula for (random) bounded harmonic functions. Under natural conditions on transition probabilities we identify these boundaries for several classes of groups with hyperbolic properties and prove the boundary triviality (i.e., the absence of non-constant random bounded harmonic functions) for groups of subexponential growth, in particular, for nilpotent groups. 相似文献
956.
In this paper we formulate and prove a general principle which enables us to deduce limit theorems for a sequence of random variables on a finitely additive probability space. 相似文献
957.
Two-dimensional thermoelasticity analysis of functionally graded thick beams is presented using the state space method coupled
with the technique of differential quadrature. Material properties vary continuously and smoothly through the beam thickness,
leading to variable coefficients in the state equation derived from the elasticity equations. Approximate laminate model is
employed to translate the state equation into the one with constant coefficients in each layer. To avoid numerical instability,
joint coupling matrices are introduced according to the continuity conditions at interfaces in the approximate model. The
differential quadrature procedure is applied to discretizing the beam in the axial direction to make easy the treatment of
arbitrary end conditions. A simply-supported beam with exponentially varying material properties is considered to validate
the present method. Numerical examples are performed to investigate the influences of relative parameters. 相似文献
958.
In this paper we examine a model for the landing procedure of aircrafts at an airport. The characteristic feature here is that due to air turbulence the safety distance between two landing aircrafts depends on the types of these two machines. Hence, an efficient routing of the aircraft to two runways may reduce their waiting time. 相似文献
959.
We obtain the formula for the transition probability of an arbitrary number of annihilating particles wandering along a ring-shaped
one-dimensional lattice from the initial coordinates to the final coordinates during an arbitrary number of discrete time
steps.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 146, No. 3, pp. 488–498, March, 2006. 相似文献
960.
In this paper, we first extend the stochastic dominance (SD) theory by introducing the first three orders of both ascending SD (ASD) and descending SD (DSD) to decisions in business planning and investment to risk-averse and risk-loving decision makers so that they can compare both return and loss. We provide investors with more tools for empirical analysis, with which they can identify the first-order ASD and DSD prospects and discern arbitrage opportunities that could increase his/her utility as well as wealth and set up a zero dollar portfolio to make huge profit. Our tools also enable investors and business planners to identify the third order ASD and DSD prospects and make better choices. 相似文献