全文获取类型
收费全文 | 39594篇 |
免费 | 1262篇 |
国内免费 | 6篇 |
专业分类
化学 | 22383篇 |
晶体学 | 170篇 |
力学 | 791篇 |
综合类 | 1篇 |
数学 | 6453篇 |
物理学 | 11064篇 |
出版年
2021年 | 282篇 |
2020年 | 474篇 |
2019年 | 310篇 |
2018年 | 441篇 |
2017年 | 424篇 |
2016年 | 959篇 |
2015年 | 819篇 |
2014年 | 919篇 |
2013年 | 2031篇 |
2012年 | 1543篇 |
2011年 | 1908篇 |
2010年 | 959篇 |
2009年 | 793篇 |
2008年 | 1815篇 |
2007年 | 1803篇 |
2006年 | 1578篇 |
2005年 | 1397篇 |
2004年 | 1095篇 |
2003年 | 944篇 |
2002年 | 890篇 |
2001年 | 749篇 |
2000年 | 668篇 |
1999年 | 463篇 |
1998年 | 414篇 |
1997年 | 412篇 |
1996年 | 513篇 |
1995年 | 468篇 |
1994年 | 489篇 |
1993年 | 569篇 |
1992年 | 460篇 |
1991年 | 353篇 |
1990年 | 398篇 |
1989年 | 326篇 |
1988年 | 331篇 |
1987年 | 336篇 |
1986年 | 309篇 |
1985年 | 478篇 |
1984年 | 472篇 |
1983年 | 446篇 |
1982年 | 460篇 |
1981年 | 463篇 |
1980年 | 429篇 |
1979年 | 386篇 |
1978年 | 429篇 |
1977年 | 401篇 |
1976年 | 362篇 |
1975年 | 332篇 |
1974年 | 323篇 |
1973年 | 334篇 |
1957年 | 285篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
161.
Summary We prove that the error inn-point Gaussian quadrature, with respect to the standard weight functionw1, is of best possible orderO(n
–2) for every bounded convex function. This result solves an open problem proposed by H. Braß and published in the problem section of the proceedings of the 2. Conference on Numerical Integration held in 1981 at the Mathematisches Forschungsinstitut Oberwolfach (Hämmerlin 1982; Problem 2). Furthermore, we investigate this problem for positive quadrature rules and for general product quadrature. In particular, for the special class of Jacobian weight functionsw
, (x)=(1–x)(1+x), we show that the above result for Gaussian quadrature is not valid precisely ifw
, is unbounded.Dedicated to Prof. H. Braß on the occasion of his 55th birthday 相似文献
162.
163.
164.
165.
166.
A. Dönni P. Fischer A. Furrer P. Bonville F. Hulliger H. R. Ott 《Zeitschrift für Physik B Condensed Matter》1990,81(1):83-88
A polycrystalline smaple of nonstoichiometric ytterbium phosphide, YbP0.84, was investigated by neutron scattering, Mössbauer spectroscopy and bulk magnetic measurements. Neutron diffraction experiments prove the existence of antiferromagnetic type II ordering belowT
N
=0.64 K, in contrast to the observed antiferromagnetic type III ordering in the stoichiometric Kondo-like compounds YbN and YbAs. The temperature dependence of the average ordered magnetic moment per Yb3+ ion with saturation value Yb = 1.03(7)
B
is similar to that of YbN. Mössbauer experiments prove the magnetic phase transition to be first order with different regions in the sample having slightly different transition temperatures. By means of inelastic neutron scattering the crystal-field level scheme was established to be
6 –
8(19meV) –
7(43meV). 相似文献
167.
168.
G. Scamarcio L. Tapfer W. König K. Ploog A. Cingolani 《Applied Physics A: Materials Science & Processing》1990,51(3):252-254
Far infrared reflectivity measurements are performed on a series of GaAs/AlAs multiple quantum well (MQW) heterostructures with systematically varied thicknesses of the constituent layers. In addition to the artificial anisotropy we observe two distinct bulk-like Reststrahlen regions. The widths of the GaAs-like and the AlAs-like Reststrahlen bands strongly depend on the relative thicknesses of the constituent layers of the MQW heterostructures, in excellent agreement with the predictions of the effective-medium theory.Prof. Aldo Cingolani passed away just before the publication of this article. We would like to dedicate this paper to his memory 相似文献
169.
Let {W(t), t0} be a standard Wiener process, and let L(x, t) be its jointly continuous local time. Define
相似文献
170.
Karen Aardal Örjan Jonsson Henrik Jönsson 《The Journal of the Operational Research Society》1989,40(1):65-73
In a practical situation it is often difficult to determine the value of the shortage costs for use in in ventory-control systems. However, in cost-minimization problems including service-level constraints, shortage costs are implicitly prevailing. With the purpose of exploring these relations, a continuous review (Q, r) stock-control system is considered, where the order points and lot sizes are computed simultaneously. Instead of explicitly expressing the shortage cost in the objective function, it is taken into consideration through a service-level constraint. The shadow price of this constraint can in some sense be interpreted as the shortage cost corresponding to the requested service level. By changing the value of the service level, interesting relations between shortage costs and service levels can be viewed for different sets of other inventory parameters. In order to investigate the sensitivity for probabilistic variations in the input data, two different probability distributions are used to describe the lead-time demand. 相似文献
|