全文获取类型
收费全文 | 8064篇 |
免费 | 804篇 |
国内免费 | 675篇 |
专业分类
化学 | 3480篇 |
晶体学 | 40篇 |
力学 | 185篇 |
综合类 | 94篇 |
数学 | 4610篇 |
物理学 | 1134篇 |
出版年
2024年 | 10篇 |
2023年 | 43篇 |
2022年 | 170篇 |
2021年 | 202篇 |
2020年 | 207篇 |
2019年 | 231篇 |
2018年 | 190篇 |
2017年 | 272篇 |
2016年 | 321篇 |
2015年 | 254篇 |
2014年 | 438篇 |
2013年 | 754篇 |
2012年 | 480篇 |
2011年 | 481篇 |
2010年 | 431篇 |
2009年 | 499篇 |
2008年 | 539篇 |
2007年 | 577篇 |
2006年 | 396篇 |
2005年 | 362篇 |
2004年 | 266篇 |
2003年 | 286篇 |
2002年 | 258篇 |
2001年 | 259篇 |
2000年 | 206篇 |
1999年 | 190篇 |
1998年 | 142篇 |
1997年 | 133篇 |
1996年 | 128篇 |
1995年 | 120篇 |
1994年 | 103篇 |
1993年 | 85篇 |
1992年 | 80篇 |
1991年 | 72篇 |
1990年 | 30篇 |
1989年 | 40篇 |
1988年 | 36篇 |
1987年 | 29篇 |
1986年 | 26篇 |
1985年 | 40篇 |
1984年 | 24篇 |
1983年 | 18篇 |
1982年 | 25篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 22篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1975年 | 8篇 |
1973年 | 7篇 |
排序方式: 共有9543条查询结果,搜索用时 15 毫秒
21.
In this paper we show that the Boltzmann weights of the three-dimensional Baxter-Bazhanov model give representations of the braid group if some suitable spectral limits are taken. In the trigonometric case we classify all possible spectral limits which produce braid group representations. Furthermore, we prove that for some of them we get cyclotomic invariants of links and for others we obtain tangle invariants generalizing the cyclotomic ones. 相似文献
22.
23.
OU型Markov过程的不变测度及弱对偶性 总被引:1,自引:1,他引:0
本文研究OU型Markov过程的不变测度、参考测度和弱对偶半群的存在性问题,并得出了不变测度的唯一性。 相似文献
24.
Marco Sangermano Mehmet Atilla Tasdelen Yusuf Yagci 《Journal of polymer science. Part A, Polymer chemistry》2007,45(21):4914-4920
Photoinitiated cationic polymerization of mono‐ and bifunctional epoxy monomers, namely cyclohexeneoxide (CHO), 4‐epoxycyclohexylmethyl‐3′,4′‐epoxycyclohexanecarboxylate (EEC), respectively by using sulphonium salts in the presence of hydroxylbutyl vinyl ether (HBVE) was studied. The real‐time FTIR spectroscopic, gel content determination, and thermal characterization studies revealed that both hydroxyl and vinyl ether functionalities of HBVE take part in the polymerization. During the polymerization, HBVE has the ability to react via both active chain end (ACE) and activated monomer mechanisms through its hydroxyl and vinyl ether functionalities, respectively. Thus, more efficient curing was observed with the addition of HBVE into EEC‐containing formulations. It was also demonstrated that HBVE is effective in facilitating the photoinduced crosslinking of monofunctional epoxy monomer, CHO in the absence of a conventional crosslinker. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4914–4920, 2007 相似文献
25.
E. Mathieu Y. Foucher P. Dellamonica J. P. Daures 《Methodology and Computing in Applied Probability》2007,9(3):389-397
In AIDS control, physicians have a growing need to use pragmatically useful and interpretable tools in their daily medical
taking care of patients. Semi-Markov process seems to be well adapted to model the evolution of HIV-1 infected patients. In
this study, we introduce and define a non homogeneous semi-Markov (NHSM) model in continuous time. Then the problem of finding
the equations that describe the biological evolution of patient is studied and the interval transition probabilities are computed.
A parametric approach is used and the maximum likelihood estimators of the process are given. A Monte Carlo algorithm is presented
for realizing non homogeneous semi-Markov trajectories. As results, interval transition probabilities are computed for distinct
times and follow-up has an impact on the evolution of patients.
相似文献
26.
关于任意随机变量序列泛函的强极限定理 总被引:1,自引:1,他引:0
本文在k是固定的正整数,{fn}是R^k 1上的Borel可测函数列时,得到了任意随机变量序列{Xrn≥0}的泛函{fn(Xn-k,…,Xn)}的强极限定理,它是Chung的关于独立随机变量序列的强大数律的推广,作为推论,得到了k重非齐次马尔科夫链的一类强极限定理. 相似文献
27.
D. Baleanu 《Czechoslovak Journal of Physics》2003,53(11):971-976
The variational formulation of the Schrödinger field was investigated and the applicability of the chain method was analyzed. Using Batalin-Fradkin-Tyutin formalism a gauge invariant theory was constructed. 相似文献
28.
Capacity Constrained Transit Assignment with Common Lines 总被引:1,自引:0,他引:1
Fumitaka Kurauchi Michael G. H. Bell Jan-Dirk Schmöcker 《Journal of Mathematical Modelling and Algorithms》2003,2(4):309-327
This paper proposes the use of absorbing Markov chains to solve the capacity constrained transit network loading problem taking
common lines into account. The approach handles congested transit networks, where some passengers will not be able to board
because of the absence of sufficient space. The model also handles the common lines problem, where choice of route depends
on frequency of arrivals. The mathematical formulation of the problem is presented together with a numerical example.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
29.
This work is devoted to near-optimal controls of large-scale discrete-time nonlinear dynamic systems driven by Markov chains; the underlying problem is to minimize an expected cost function. Our main goal is to reduce the complexity of the underlying systems. To achieve this goal, discrete-time control models under singularly-perturbed Markov chains are introduced. Using a relaxed control representation, our effort is devoted to finding near-optimal controls. Lumping the states in each irreducible class into a single state gives rise to a limit system. Applying near-optimal controls of the limit system to the original system, near-optimal controls of the original system are derived. 相似文献
30.
Rolando Cavazos-Cadena 《Annals of Operations Research》1991,28(1):169-184
We consider a class of Markov decision processes withfinite state and action spaces which, essentially, is determined by the following condition: The state space isirreducible under the action of any stationary policy. However, except by this restriction, the transition law iscompletely unknown to the controller. In this context, we find a set of policies under which thefrequency estimators of the transition law are strongly consistent and then, this result is applied to constructadaptive asymptotically discount-optimal policies.Dedicated to Professor Truman O. Lewis, on the occasion of his sixtieth birthdayThis research was supported in part by the Third World Academy of Sciences (TWAS) under Grant TWAS RG MP 898-152, and in part by the Consejo Nacional de Ciencia y Tecnología (CONACYT) under Grant A128CCOEO550 (MT-2). 相似文献