全文获取类型
收费全文 | 96346篇 |
免费 | 3593篇 |
国内免费 | 2673篇 |
专业分类
化学 | 37151篇 |
晶体学 | 945篇 |
力学 | 7738篇 |
综合类 | 118篇 |
数学 | 34403篇 |
物理学 | 22257篇 |
出版年
2024年 | 86篇 |
2023年 | 429篇 |
2022年 | 645篇 |
2021年 | 720篇 |
2020年 | 850篇 |
2019年 | 773篇 |
2018年 | 10958篇 |
2017年 | 10739篇 |
2016年 | 6935篇 |
2015年 | 1785篇 |
2014年 | 1373篇 |
2013年 | 1756篇 |
2012年 | 5391篇 |
2011年 | 12094篇 |
2010年 | 6769篇 |
2009年 | 7050篇 |
2008年 | 7739篇 |
2007年 | 9748篇 |
2006年 | 1174篇 |
2005年 | 2154篇 |
2004年 | 2198篇 |
2003年 | 2545篇 |
2002年 | 1675篇 |
2001年 | 786篇 |
2000年 | 722篇 |
1999年 | 578篇 |
1998年 | 530篇 |
1997年 | 453篇 |
1996年 | 524篇 |
1995年 | 405篇 |
1994年 | 306篇 |
1993年 | 255篇 |
1992年 | 217篇 |
1991年 | 220篇 |
1990年 | 172篇 |
1989年 | 152篇 |
1988年 | 112篇 |
1987年 | 113篇 |
1986年 | 128篇 |
1985年 | 93篇 |
1984年 | 74篇 |
1983年 | 62篇 |
1982年 | 56篇 |
1981年 | 49篇 |
1980年 | 50篇 |
1979年 | 45篇 |
1914年 | 45篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
In this paper we, firstly, classify the complex networks in which the nodes
are of the lifetime distribution. Secondly, in order to study complex networks
in terms of queuing system and homogeneous Markov chain, we
establish the relation between the complex networks and queuing system,
providing a new way of studying complex networks. Thirdly, we prove that there
exist stationary degree distributions of M--G--P network, and obtain the
analytic expression of the distribution by means of Markov chain theory. We
also obtain the average path length and clustering coefficient of the
network. The results show that M--G--P network is not only scale-free but also
of a small-world feature in proper conditions. 相似文献
992.
Lie symmetrical perturbation and adiabatic invariants of generalized Hojman type for Lagrange systems 下载免费PDF全文
Based on the invariance of differential equations under
infinitesimal transformations of group, Lie symmetries, exact
invariants, perturbation to the symmetries and adiabatic invariants
in form of non-Noether for a Lagrange system are presented. Firstly,
the exact invariants of generalized Hojman type led directly by Lie
symmetries for a Lagrange system without perturbations are given.
Then, on the basis of the concepts of Lie symmetries and higher
order adiabatic invariants of a mechanical system, the perturbation
of Lie symmetries for the system with the action of small
disturbance is investigated, the adiabatic invariants of generalized
Hojman type for the system are directly obtained, the conditions for
existence of the adiabatic invariants and their forms are proved.
Finally an example is presented to illustrate these results. 相似文献
993.
Grzegorz Stepniak Lukasz Maksymiuk Jerzy Siuzdak 《Optical and Quantum Electronics》2007,39(15):1281-1288
Frequency response of passive optical network (PON) based on multimode fibers is investigated. The network comprises fibers,
connectors and splitters/couplers. It is shown that due to mode filtering at splitters, the frequency response is different
for different network nodes in otherwise symmetrical network. 相似文献
994.
Alexander I. Nosich Elena I. Smotrova Svetlana V. Boriskina Trevor M. Benson Phillip Sewell 《Optical and Quantum Electronics》2007,39(15):1253-1272
Research into microdisk lasers demonstrates new achievements both in the technology and in the associated physical effects
and applications. Melting and rounding of the disk edge boosts the Q-factors due to improved surface smoothness. In-plane
cavity shape is widely used as a design instrument. Optimal shaping of pumped area lowers the threshold power. Photonic molecules
made of several microdisks as “photonic atoms” show lasing at several closely spaced frequencies. A microdisk with a single
quantum dot as an active region is considered as the most promising system for realisation of a single photon emitter necessary
for quantum computing. These new effects and devices can be simulated with accurate numerical techniques, developed recently
for “warm-cavity” linear modelling, that are able to bring a new vision of the physics of lasing. 相似文献
995.
996.
997.
998.
After taking into account energy conservation and the particle’s self-gravitation interaction, Hawking radiation of the massive
particle as tunneling from Schwarzshild-anti-de Sitter black hole is studied by using Parikh-Wilczek’s semi-classical quantum
tunneling approach. Meanwhile, Hawking radiation as tunneling from the black hole is reexamined by developing Angheben–Nadalini–Vanzo–Zerbini
(ANVZ) covariant method to cover energy conservation and the particle’s self-gravitation interaction. Both the results perfectly
generalize those obtained by Parikh and Wilczek, and show that the tunneling rate is related to the change of Bekenstein-Hawking
entropy, and the factual emission spectrum is not exactly thermal, but satisfies the underlying unitary theory.
PACS: 04.70-s, 9760. Lf. 相似文献
999.
David Ruelle 《Communications in Mathematical Physics》2007,270(1):233-265
We analyze the dynamics of a simple but nontrivial classical Hamiltonian system of infinitely many coupled rotators. We assume
that this infinite system is driven out of thermal equilibrium either because energy is injected by an external force (Case
I), or because heat flows between two thermostats at different temperatures (Case II). We discuss several possible definitions
of the entropy production associated with a finite or infinite region, or with a partition of the system into a finite number
of pieces. We show that these definitions satisfy the expected bounds in terms of thermostat temperatures and energy flow. 相似文献
1000.
The vibrational dynamics of protein folding is analyzed in the framework of Tsallis statistics. We employ exact expressions
for classical harmonic oscillators by considering the unnormalized constraints. As q→1, we show that these approximations agree with the result of Gaussian network model. 相似文献