全文获取类型
收费全文 | 5650篇 |
免费 | 98篇 |
国内免费 | 11篇 |
专业分类
化学 | 3999篇 |
晶体学 | 18篇 |
力学 | 51篇 |
数学 | 897篇 |
物理学 | 794篇 |
出版年
2021年 | 34篇 |
2020年 | 47篇 |
2019年 | 40篇 |
2016年 | 101篇 |
2015年 | 85篇 |
2014年 | 104篇 |
2013年 | 216篇 |
2012年 | 191篇 |
2011年 | 206篇 |
2010年 | 130篇 |
2009年 | 128篇 |
2008年 | 164篇 |
2007年 | 184篇 |
2006年 | 187篇 |
2005年 | 193篇 |
2004年 | 178篇 |
2003年 | 131篇 |
2002年 | 138篇 |
2001年 | 92篇 |
2000年 | 66篇 |
1999年 | 77篇 |
1998年 | 91篇 |
1997年 | 101篇 |
1996年 | 109篇 |
1995年 | 87篇 |
1994年 | 105篇 |
1993年 | 96篇 |
1992年 | 102篇 |
1991年 | 76篇 |
1990年 | 93篇 |
1989年 | 90篇 |
1988年 | 90篇 |
1987年 | 95篇 |
1986年 | 125篇 |
1985年 | 134篇 |
1984年 | 98篇 |
1983年 | 89篇 |
1982年 | 82篇 |
1981年 | 78篇 |
1980年 | 103篇 |
1979年 | 62篇 |
1978年 | 97篇 |
1977年 | 88篇 |
1976年 | 77篇 |
1975年 | 50篇 |
1974年 | 70篇 |
1973年 | 67篇 |
1972年 | 57篇 |
1971年 | 42篇 |
1970年 | 53篇 |
排序方式: 共有5759条查询结果,搜索用时 15 毫秒
11.
M. Köhl A. Öttl S. Ritter T. Donner T. Bourdel T. Esslinger 《Applied physics. B, Lasers and optics》2007,86(3):391-393
We report an experimental investigation of two-particle correlations between neutral atoms in a Hanbury Brown and Twiss experiment.
Both an atom laser beam and a pseudo-thermal atomic beam are extracted from a Bose–Einstein condensate and the atom flux is
measured with a single atom counter. We determine the conditional and the unconditional detection probabilities for the atoms
in the beam and find good agreement with the theoretical predictions.
PACS 03.75.Pp; 05.30.Jp; 07.77.Gx; 42.50.Pq 相似文献
12.
13.
Gerhard Lischke 《Mathematical Logic Quarterly》2006,52(1):20-28
Punctured languages are languages whose words are partial words in the sense that the letters at some positions are unknown. We investigate to which extent restoration of punctured languages is possible if the number of unknown positions or the proportion of unknown positions per word, respectively, is bounded, and we study their relationships for different boundings. The considered restoration classes coincide with similarity classes according to some kind of similarity for languages. Thus all results we can also formulate in the language of similarity. We show some hierarchies of similarity classes for each class from the Chomsky hierarchy and prove the existence of linear languages which are not δ ‐similar to any regular language for any δ < ½. For δ ≥ ½ this is unknown but it could only be possible in the case of non‐slender linear languages. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
14.
We present a Bayesian theory of object identification. Here, identifying an object means selecting a particular observation from a group of observations (variants), this observation (the regular variant) being characterized by a distributional model. In this sense, object identification means assigning a given model to one of several observations. Often, it is the statistical model of the regular variant, only, that is known. We study an estimator which relies essentially on this model and not on the characteristics of the “irregular” variants. In particular, we investigate under what conditions this variant selector is optimal. It turns out that there is a close relationship with exchangeability and Markovian reversibility. We finally apply our theory to the case of irregular variants generated from the regular variant by a Gaussian linear model. 相似文献
15.
16.
Spectral changes induced by moderate electric fields provide detailed insight into the electronic states of organic and inorganic solids. Although the basic effects, Stark effect and Franz–Keldysh effect, are the same in both types of material, the electroabsorption spectra vary strongly in size and spectral lineshape due to competing interactions. The large variance of the effects is demonstrated by representative examples of high mobility semiconductors, quantum wells, π-conjugated polymers, and charge transfer transitions in single crystals, disordered films and a double-quantum well. It is shown that only high-quality samples reveal the quantum mechanics of field-induced effects which are very sensitive to disorder. 相似文献
17.
It is wellknown that the technique of character sums together with the tools of algebraic number theory is the adequate method for the study of difference sets in abelian groups, compare for instance Ott [5] or Turyn [6]. In this paper we use this method to prove a new non-existence theorem for certain difference sets in abelian groups of order rpa rp^a , where r 1 2 r \neq 2 and p are distinct primes. 相似文献
18.
Gerhard Eisenbeis 《Micron (Oxford, England : 1993)》2003,34(8):453
19.
20.
We consider a class of non-linear mixed integer programs with n integer variables and k continuous variables. Solving instances from this class to optimality is an NP-hard problem. We show that for the cases with
k=1 and k=2, every optimal solution is integral. In contrast to this, for every k≥3 there exist instances where every optimal solution takes non-integral values.
Received: August 2001 / Accepted: January 2002?Published online March 27, 2002 相似文献