全文获取类型
收费全文 | 50481篇 |
免费 | 7195篇 |
国内免费 | 5003篇 |
专业分类
化学 | 15407篇 |
晶体学 | 991篇 |
力学 | 10110篇 |
综合类 | 715篇 |
数学 | 15433篇 |
物理学 | 20023篇 |
出版年
2024年 | 123篇 |
2023年 | 513篇 |
2022年 | 1112篇 |
2021年 | 1326篇 |
2020年 | 1624篇 |
2019年 | 1432篇 |
2018年 | 1380篇 |
2017年 | 1884篇 |
2016年 | 2182篇 |
2015年 | 1770篇 |
2014年 | 2893篇 |
2013年 | 3720篇 |
2012年 | 3169篇 |
2011年 | 3546篇 |
2010年 | 2948篇 |
2009年 | 3289篇 |
2008年 | 3192篇 |
2007年 | 3221篇 |
2006年 | 2813篇 |
2005年 | 2608篇 |
2004年 | 2260篇 |
2003年 | 2029篇 |
2002年 | 1823篇 |
2001年 | 1482篇 |
2000年 | 1409篇 |
1999年 | 1266篇 |
1998年 | 1182篇 |
1997年 | 1009篇 |
1996年 | 821篇 |
1995年 | 692篇 |
1994年 | 631篇 |
1993年 | 502篇 |
1992年 | 517篇 |
1991年 | 401篇 |
1990年 | 329篇 |
1989年 | 261篇 |
1988年 | 214篇 |
1987年 | 167篇 |
1986年 | 112篇 |
1985年 | 159篇 |
1984年 | 142篇 |
1983年 | 61篇 |
1982年 | 101篇 |
1981年 | 77篇 |
1980年 | 40篇 |
1979年 | 55篇 |
1978年 | 43篇 |
1977年 | 50篇 |
1976年 | 27篇 |
1974年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
非线性互补问题的一种全局收敛的显式光滑Newton方法 总被引:2,自引:0,他引:2
本针对Po函数非线性互补问题,给出了一种显式光滑Newton方法,该方法将光滑参数μ进行显式迭代而不依赖于Newton方向的搜索过程,并在适当的假设条件下,证明了算法的全局收敛性。 相似文献
32.
电路过渡过程所列方程是微分方程,本文中采用的是方框图模型分析法,即将微分方程的复杂示解分解成最基本的加(减)、乘(除)、积分(微分)、增益等运算,采用VB设计用户界面产进行计算,并给出了一算例。 相似文献
33.
D. J. Plazek C. A. Bero S. Neumeister G. Floudas G. Fytas K. L. Ngai 《Colloid and polymer science》1994,272(11):1430-1438
By making creep and recoverable creep measurements of a nearly monodisperse low molecular weight poly(methyl phenyl siloxane) sample, we have found on decreasing temperature towardsT
g that there is continuously a change in the viscoelastic spectrum concomitant with a decrease of the steadystate recoverable compliance. This behavior is exactly the same as previously observed in low molecular weight poly(styrene), proving that this spectacular anomaly in the viscoelasticity of low molecular weight polymers is general and deserves an explanation. Photon correlation spectroscopic measurements performed on the same sample have extended the observation of the viscoelastic response to shorter times and the result corroborates the trend of variation established by the creep data.Dedicated to Prof.Dr. E. W. Fischer on his 65th Birthday. Prof.Dr. Fischer is known for his valuable contribution to fosterine, international collaboration of research in polymer science. This work is an example of his contribution because it would not be possible without him bringing us together. One of us (KLN) would like to take this opportunity to thank Prof. Dr. Fischer for his unwaiving support of the 1st (Crete) and the 2nd (Alicante) International Discussion Meeting on Relaxations in Complex Systems 相似文献
34.
It is proved that for any integerk≥ 54 000, there isN
k
>0 depending onk only such that every even integer ≥N
k
is a sum of two odd prime numbers andk powers of 2.
Project partially supported by RGC Research Grant (No.HKU 7122/97P) and Post-Doctoral Fellowship of the University of Hong
Kong. 相似文献
35.
间歇式高速同步相机新型全数字化微机控制系统 总被引:2,自引:2,他引:0
本文提出了一种间歇式高速同步相机的全新设计方法,介绍了系统的工作原理,硬件,软件设计以及核心控制算法,最后给出了实际应用结果。 相似文献
36.
WANG Zhong HONG Haitao XIAO Hai SUN Changku MENG Yan YE Shenghua 《Chinese Journal of Lasers》1997,6(5):435-440
1.IntroductionAbsolutedistancemeasurementisfarfromanewtopic.However,itisstillafieldstimulatinggreatinterestsnowadaysduetoitSimportantroleinmanufacturingandassembly['J.SincethegreatsuccessachievedbyMichelsonandBenoitwhentheyfirstdevelopedaninterferometertodeterminethestandardmeterintermsofthemonochromaticredcadmiumline,theopticinterferometerhasbeenprovedtobeoneofthemostpreciseandefficientwayindisplacementmeasurementbecauseofitshighdiscriminationandsimplestructure.However,thetraditionalinterfe… 相似文献
37.
Rafael López 《Annals of Global Analysis and Geometry》1997,15(3):201-210
In this paper we study constant mean curvature compact surfaces with two Jordan curves in parallel planes as boundary and we investigate the point at which the surface inherits the symmetries of its boundary. 相似文献
38.
本文利用统计计量学方法对山西省农民家庭消费水平和消费结构的变化及原因进行了实证分析。建立了山西省农民人均消费的消费函数和山西省农民总消费支出与食品、衣着、住房、日用品、燃料及文化生活服务支出的关系模型,并通过模型分析解释了农民的消费结构,也为决策者提供一些有效的参考资料。 相似文献
39.
J.V.P. de OliveiraA.V. Cardona M.T. VilhenaR.C. Barros 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,73(1):55-62
We describe a semi-analytical numerical method for coherent isotropic scattering time-dependent radiative transfer problems in slab geometry. This numerical method is based on a combination of two classes of numerical methods: the spectral methods and the Laplace transform (LTSN) methods applied to the radiative transfer equation in the discrete ordinates (SN) formulation. The basic idea is to use the essence of the spectral methods and expand the intensity of radiation in a truncated series of Laguerre polynomials in the time variable and then solve recursively the resulting set of “time-independent” SN problems by using the LTSN method. We show some numerical experiments for a typical model problem. 相似文献
40.
In circuit-switched networks call streams are characterized by their mean and peakedness (two-moment method). The GI/M/C/0 system is used to model a single link, where the GI-stream is determined by fitting moments appropriately. For the moments of the overflow traffic of a GI/M/C/0 system there are efficient numerical algorithms available. However, for the moments of the freed carried traffic, defined as the moments of a virtual link of infinite capacity to which the process of calls accepted by the link (carried arrival process) is virtually directed and where the virtual calls get fresh exponential i.i.d. holding times, only complex numerical algorithms are available. This is the reason why the concept of the freed carried traffic is not used. The main result of this paper is a numerically stable and efficient algorithm for computing the moments of freed carried traffic, in particular an explicit formula for its peakedness. This result offers a unified handling of both overflow and carried traffics in networks. Furthermore, some refined characteristics for the overflow and freed carried streams are derived. 相似文献