全文获取类型
收费全文 | 37352篇 |
免费 | 4046篇 |
国内免费 | 2668篇 |
专业分类
化学 | 1244篇 |
晶体学 | 84篇 |
力学 | 5008篇 |
综合类 | 286篇 |
数学 | 8772篇 |
物理学 | 7290篇 |
综合类 | 21382篇 |
出版年
2024年 | 101篇 |
2023年 | 349篇 |
2022年 | 586篇 |
2021年 | 702篇 |
2020年 | 802篇 |
2019年 | 756篇 |
2018年 | 765篇 |
2017年 | 947篇 |
2016年 | 1045篇 |
2015年 | 1065篇 |
2014年 | 1789篇 |
2013年 | 2182篇 |
2012年 | 2171篇 |
2011年 | 2361篇 |
2010年 | 1858篇 |
2009年 | 2080篇 |
2008年 | 1998篇 |
2007年 | 2577篇 |
2006年 | 2270篇 |
2005年 | 2201篇 |
2004年 | 1887篇 |
2003年 | 1755篇 |
2002年 | 1537篇 |
2001年 | 1338篇 |
2000年 | 1261篇 |
1999年 | 1107篇 |
1998年 | 915篇 |
1997年 | 917篇 |
1996年 | 782篇 |
1995年 | 632篇 |
1994年 | 540篇 |
1993年 | 447篇 |
1992年 | 462篇 |
1991年 | 406篇 |
1990年 | 323篇 |
1989年 | 268篇 |
1988年 | 231篇 |
1987年 | 184篇 |
1986年 | 109篇 |
1985年 | 93篇 |
1984年 | 52篇 |
1983年 | 33篇 |
1982年 | 35篇 |
1981年 | 28篇 |
1980年 | 18篇 |
1979年 | 19篇 |
1978年 | 18篇 |
1977年 | 18篇 |
1976年 | 8篇 |
1974年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Luis L. Bonilla 《Journal of statistical physics》1987,46(3-4):659-678
A nonlinear Fokker-Planck equation is derived to describe the cooperative behavior of general stochastic systems interacting via mean-field couplings, in the limit of an infinite number of such systems. Disordered systems are also considered. In the weak-noise limit; a general result yields the possibility of having bifurcations from stationary solutions of the nonlinear Fokker-Planck equation into stable time-dependent solutions. The latter are interpreted as non-equilibrium probability distributions (states), and the bifurcations to them as nonequilibrium phase transitions. In the thermodynamic limit, results for three models are given for illustrative purposes. A model of self-synchronization of nonlinear oscillators presents a Hopf bifurcation to a time-periodic probability density, which can be analyzed for any value of the noise. The effects of disorder are illustrated by a simplified version of the Sompolinsky-Zippelius model of spin-glasses. Finally, results for the Fukuyama-Lee-Fisher model of charge-density waves are given. A singular perturbation analysis shows that the depinning transition is a bifurcation problem modified by the disorder noise due to impurities. Far from the bifurcation point, the CDW is either pinned or free, obeying (to leading order) the Grüner-Zawadowki-Chaikin equation. Near the bifurcation, the disorder noise drastically modifies the pattern, giving a quenched average of the CDW current which is constant. Critical exponents are found to depend on the noise, and they are larger than Fisher's values for the two probability distributions considered. 相似文献
103.
104.
Annegret K. Wagler 《4OR: A Quarterly Journal of Operations Research》2005,3(4):329-336
Shepherd95 proved that the stable set polytopes of near-bipartite graphs are given by constraints associated with the complete
join of antiwebs only. For antiwebs, the facet set reduces to rank constraints associated with single antiwebs by Wagler2004.
We extend this result to a larger graph class, the complements of fuzzy circular interval graphs, recently introduced in ChudnovskySeymour2004.
Received: November 2004 / Revised version: June 2005 相似文献
105.
The luminous intensity unit of candela was realized based on filter-radiometer, which is traceable to detector-based primary standard electrical substitution cryogenic radiometer (ESCR). In that realization the traditional Osram Wi41/G-type incandescent lamp and filter-radiometer consisting of an aperture, a V(λ) filter and a silicon photodiode based trap detector were used as light source and detection element, respectively. Measurement techniques of effective aperture area, spectral transmittance of V(λ) filter and absolute responsivity of trap detector are also presented. 相似文献
106.
A. P. Prishivalko 《Journal of Applied Spectroscopy》1997,64(1):94-100
A method for finding the optimum sizes of pigment particles, their volume concentration, and the paint coating thickness that
provide the covering power and the required coloristic characteristics of reflected light for the minimum flow rate of pigments
is based on using a four-flow approximation of the solution to the equation of radiation transfer in dispersion media and
is extended to coatings of complex composition. The capabilities of the method are demonstrated by examples of coatings of
mixtures of hematite and rutile particles in a binder with n=1.5 for variations of the modal size and the half-width of the
size distribution of the pigment particles.
B. I. Stepanov Institute of Physics, Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated
from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 90–96, January–February, 1997. 相似文献
107.
电站锅炉系统性能仿真模型的建立 总被引:1,自引:0,他引:1
1引言根据热力学第二定律,燃料中的化学拥将近一半损失在锅炉的燃烧与传热过程中。因此,优化锅炉性能对降低整个火电机组的煤耗率具有明显效果。完整的锅炉系统由磨煤机、送风机、一次风机、弓讯机、炉膛、汽包、过热器、再热器、省煤器、空气预热器等单元组成,这些单元之间的联结错综复杂。本文建立了锅炉系统中通用单元的性能模型,并在此基础上,对锅炉系统的结构特点进行了分析,利用过程系统工程中的序贯模块法建立了整个锅炉系统的性能模型。对单元的划分、回路的切断及断裂流股的收敛与迭代策略提出了自己的观点。最后根据生产厂… 相似文献
108.
一类具有非局部反应扩散方程的奇摄动问题 总被引:7,自引:0,他引:7
本文讨论一类具非局部反应扩散方程的奇摄动初始边值问题,利用迭代法及微分不等式,研究了初始边值问题的存在唯一及其渐近性态。 相似文献
109.
110.
本文提出了流体力学解析边界拟合坐标系方法,及建立在这种坐标系基础上对流动方程进行摄动处理的方法,并列举几种流动建立了解析边界拟合坐标系中的方程。 相似文献