全文获取类型
收费全文 | 14784篇 |
免费 | 491篇 |
国内免费 | 95篇 |
专业分类
化学 | 10551篇 |
晶体学 | 119篇 |
力学 | 301篇 |
数学 | 1747篇 |
物理学 | 2652篇 |
出版年
2023年 | 77篇 |
2022年 | 102篇 |
2021年 | 145篇 |
2020年 | 224篇 |
2019年 | 201篇 |
2018年 | 150篇 |
2017年 | 138篇 |
2016年 | 333篇 |
2015年 | 292篇 |
2014年 | 336篇 |
2013年 | 687篇 |
2012年 | 908篇 |
2011年 | 1129篇 |
2010年 | 525篇 |
2009年 | 370篇 |
2008年 | 871篇 |
2007年 | 938篇 |
2006年 | 956篇 |
2005年 | 944篇 |
2004年 | 776篇 |
2003年 | 665篇 |
2002年 | 579篇 |
2001年 | 249篇 |
2000年 | 232篇 |
1999年 | 167篇 |
1998年 | 152篇 |
1997年 | 144篇 |
1996年 | 209篇 |
1995年 | 156篇 |
1994年 | 182篇 |
1993年 | 176篇 |
1992年 | 163篇 |
1991年 | 121篇 |
1990年 | 105篇 |
1989年 | 114篇 |
1988年 | 100篇 |
1987年 | 84篇 |
1986年 | 80篇 |
1985年 | 152篇 |
1984年 | 105篇 |
1982年 | 113篇 |
1981年 | 108篇 |
1980年 | 102篇 |
1979年 | 94篇 |
1978年 | 97篇 |
1977年 | 104篇 |
1976年 | 73篇 |
1975年 | 77篇 |
1974年 | 72篇 |
1973年 | 67篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
82.
In this paper, assuming a certain set-theoretic hypothesis, a positive answer is given to a question of H. Kraljevi, namely it is shown that there exists a Lebesgue measurable subsetA of the real line such that the set {c R: A + cA contains an interval} is nonmeasurable. Here the setA + cA = {a + ca: a, a A}. Two other results about sets of the formA + cA are presented. 相似文献
83.
84.
Andrew Elby 《Foundations of Physics Letters》1990,3(3):239-247
Heywood and Redhead's 1983 algebraic (Kochen-Specker type) impossibility proof, which establishes the inconsistency of a broad class of contextualized local realistic theories, assumes two locality conditions and two auxiliary assumptions. One of those auxiliary conditions, FUNC*, has been called a physically unmotivated,ad hoc formal constraint.In this paper, we derive Heywood and Redhead's auxiliary conditions from physical assumptions. This allows us to analyze which classes of hidden-variables theories escape the Heywood-Redhead contradiction. By doing so, we hope to clarify the physical and philosophical ramifications of the Heywood-Redhead proof. Most current hidden-variables theories, it turns out, violate Heywood and Redhead's auxiliary conditions.1. See Redhead [1], pp. 133–136, for a complete discussion.2. Arthur Fine first pointed out the implicit reliance on FUNC*, and proved FUNC* to be both consistent with and independent of the Value Rule.3. LetA=iai
P
i
andB=jbj
Pj be spectral resolutions ofA andB. Then <A,B> is the observable associated with maximal operatorR=ijfij
P
iPj, where fij=F(ai,bj), and where function F is 1:1.4. Heywood and Redhead's versions of these conditions employ equivalence-class notation to specify the ontological context. {<D,E>}={R} refers to the equivalence class of all possible <D,E> formed by using different F functions (cf. Footnote 3). Clearly, such notation assumes that ifR andR are two distinct commuting maximal operators formed as described in Fn. 3 fromD andE using two different F(di,ej) functions, then [Q]t
(R)(R)=[Q]t
(R)(R), so that [Q]t
{R}(R) is uniquely defined.Heywood and Redhead never rely upon this assumption in their proof, however. It is easily checked that a Heywood-Redhead contradiction follows from my non-equivalence class versions of OLOC, ELOC, VR, and FUNC*. Therefore, I will not use equivalence class notation.5. Here I denote by µR the composite state of all the apparatuses needed to measure R. So µR may represent the state of more than one device.6 This is because in a hidden-variables framework, quantum mechanical probabilities are a weighted average of the underlying hidden-variables probabilities.7. This argument resembles a proof given by Fine [8].8. Recall from theorem 1 that ifQ=f(R), then for all quantum states , P(t)(Qf(r), R=r)=0. 相似文献
85.
Kochocki JA Allison WW Alner GJ Ambats I Ayres DS Balka LJ Barr GD Barrett WL Benjamin D Border P Brooks CB Cobb JH Cockerill DJ Coover K Courant H Dahlin B DasGupta U Dawson JW Edwards VW Fields TH Kirby-Gallagher LM Garcia-Garcia C Giles RH Goodman MC Heller K Heppelman S Hill N Hoftiezer JH Jankowski DJ Johns K Joyce T Kafka T Litchfield PJ Lopez FV Lowe M Mann WA Marshak ML May EN McMaster L Milburn RH Miller W Napier A Oliver WP Pearce GF Perkins DH Peterson EA Price LE Roback D Rosen DB 《Physical review D: Particles and fields》1990,42(9):2967-2973
86.
87.
Ammar R Ball RC Banerjee S Bhat PC Bosetti P Bromberg C Canough GE Coffin T Dershem TO Dixon RL Fenker HC Ganguli SN Gensch U Girtler P Goshaw AT Grard F Gurtu A Hamilton C Henri VP Hernandez JJ Hrubec J Iori M Jones LW Kuhn D Knauss D Leedom ID Legros P Lemonne J Leutz H Liu X Malhotra PK Marraffino JM Mendez GE Miller R Naumann T Nguyen A Nowak H Pilette P Poirier J Poppleton A Raghavan R Rasner K Reucroft S Robertson WJ Roe BP Roth A Senko M Struczinski W Subramanian A Touboul MC Vonck B 《Physical review letters》1988,61(19):2185-2188
88.
89.
90.
Stochastic modeling of a billiard in a gravitational field: Power law behavior of Lyapunov exponents
We consider the motion of a point particle (billiard) in a uniform gravitational field constrained to move in a symmetric wedge-shaped region. The billiard is reflected at the wedge boundary. The phase space of the system naturally divides itself into two regions in which the tangent maps are respectively parabolic and hyperbolic. It is known that the system is integrable for two values of the wedge half-angle
1 and
2 and chaotic for
1<<
2. We study the system at three levels of approximation: first, where the deterministic dynamics is replaced by a random evolution; second, where, in addition, the tangent map in each region is, replaced by its average; and third, where the tangent map is replaced by a single global average. We show that at all three levels the Lyapunov exponent exhibits power law behavior near
1 and
2 with exponents 1/2 and 1, respectively. We indicate the origin of the exponent 1, which has not been observed in unaccelerated billiards. 相似文献