全文获取类型
收费全文 | 7272篇 |
免费 | 174篇 |
国内免费 | 25篇 |
专业分类
化学 | 4852篇 |
晶体学 | 32篇 |
力学 | 129篇 |
数学 | 1040篇 |
物理学 | 1418篇 |
出版年
2021年 | 60篇 |
2020年 | 84篇 |
2019年 | 65篇 |
2017年 | 52篇 |
2016年 | 129篇 |
2015年 | 123篇 |
2014年 | 142篇 |
2013年 | 278篇 |
2012年 | 242篇 |
2011年 | 265篇 |
2010年 | 163篇 |
2009年 | 167篇 |
2008年 | 204篇 |
2007年 | 243篇 |
2006年 | 247篇 |
2005年 | 240篇 |
2004年 | 206篇 |
2003年 | 198篇 |
2002年 | 198篇 |
2001年 | 137篇 |
2000年 | 128篇 |
1999年 | 125篇 |
1998年 | 104篇 |
1997年 | 85篇 |
1996年 | 120篇 |
1995年 | 109篇 |
1994年 | 119篇 |
1993年 | 131篇 |
1992年 | 154篇 |
1991年 | 138篇 |
1990年 | 103篇 |
1989年 | 113篇 |
1988年 | 103篇 |
1987年 | 122篇 |
1986年 | 104篇 |
1985年 | 149篇 |
1984年 | 146篇 |
1983年 | 116篇 |
1982年 | 144篇 |
1981年 | 124篇 |
1980年 | 125篇 |
1979年 | 143篇 |
1978年 | 112篇 |
1977年 | 126篇 |
1976年 | 102篇 |
1975年 | 87篇 |
1974年 | 120篇 |
1973年 | 97篇 |
1972年 | 43篇 |
1971年 | 63篇 |
排序方式: 共有7471条查询结果,搜索用时 15 毫秒
1.
2.
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
3.
Julia K Pruns Jens-Peter Vietzke Manfred Strassner Claudius Rapp Ulrich Hintze Wilfried A K?nig 《Rapid communications in mass spectrometry : RCM》2002,16(3):208-211
A new solvent-free sample preparation method using silver trifluoroacetate (AgTFA) was developed for the analysis of low molecular weight paraffins and microcrystalline waxes by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS). Experiments show that spectral quality can be enhanced by dispersing AgTFA directly in liquid paraffins without the use of additional solvents. This preparation mixture is applied directly to the MALDI probe. Solid waxes could be examined by melting prior to analysis. The method also provides sufficiently reproducible spectra that peak area ratios between mono- and bicyclic alkane peaks indicated variations in the cycloalkane content of paraffin samples. Dehydrogenation of hydrocarbons observed during the desorption/ionization process was studied by analysis of alkane standards. 相似文献
4.
Michel Weber 《Transactions of the American Mathematical Society》2006,358(2):911-936
We apply a majorizing measure theorem of Talagrand to obtain uniform bounds for sums of random variables satisfying increment conditions of the type considered in Gál-Koksma Theorems. We give some applications.
5.
6.
O. Kortner M.P. Locher V.E. Markushin P. Weber O. Wigger 《The European Physical Journal C - Particles and Fields》2002,25(3):353-360
We study correlations in the exclusive reaction at rest with complete reconstruction of the kinematics for each event. The inclusive distribution is fairly flat at small
invariant mass of the pion pair while a small enhancement in the double differential distribution is observed for small invariant
masses of both pion pairs. Dynamical models with resonances in the final state are shown to be consistent with the data while
the stochastic HBT mechanism is not supported by the present findings.
Received: 26 February 2002 / Revised version: 22 July 2002 / Published online: 30 August 2002 相似文献
7.
Michel Weber 《Results in Mathematics》2005,47(3-4):340-354
Under a very moderate assumption on the Fourier coefficients of a periodic function, we show the convergence almost everywhere of the sequence of averages of its associated Riemann sums. The structure of the set of averages is analyzed by proving a spectral regularization type inequality, which allows to control the corresponding Littlewood-Paley square function. 相似文献
8.
9.
The control of piecewise-deterministic processes is studied where only local boundedness of the data is assumed. Moreover the discount rate may be zero. The value function is shown to be solution to the Bellman equation in a weak sense; however the solution concept is strong enough to generate optimal policies. Continuity and compactness conditions are given for the existence of nonrelaxed optimal feedback controls. 相似文献
10.
Kenneth Weber Vilmar Trevisan Luiz Felipe Martins 《Journal of Algorithms in Cognition, Informatics and Logic》2005,54(2):152-167
This paper describes the first algorithm to compute the greatest common divisor (GCD) of two n-bit integers using a modular representation for intermediate values U, V and also for the result. It is based on a reduction step, similar to one used in the accelerated algorithm [T. Jebelean, A generalization of the binary GCD algorithm, in: ISSAC '93: International Symposium on Symbolic and Algebraic Computation, Kiev, Ukraine, 1993, pp. 111–116; K. Weber, The accelerated integer GCD algorithm, ACM Trans. Math. Softw. 21 (1995) 111–122] when U and V are close to the same size, that replaces U by (U−bV)/p, where p is one of the prime moduli and b is the unique integer in the interval (−p/2,p/2) such that . When the algorithm is executed on a bit common CRCW PRAM with O(nlognlogloglogn) processors, it takes O(n) time in the worst case. A heuristic model of the average case yields O(n/logn) time on the same number of processors. 相似文献