全文获取类型
收费全文 | 11124篇 |
免费 | 573篇 |
国内免费 | 44篇 |
专业分类
化学 | 7942篇 |
晶体学 | 52篇 |
力学 | 200篇 |
数学 | 1617篇 |
物理学 | 1930篇 |
出版年
2023年 | 81篇 |
2022年 | 112篇 |
2021年 | 163篇 |
2020年 | 246篇 |
2019年 | 213篇 |
2018年 | 153篇 |
2017年 | 127篇 |
2016年 | 444篇 |
2015年 | 397篇 |
2014年 | 435篇 |
2013年 | 529篇 |
2012年 | 728篇 |
2011年 | 755篇 |
2010年 | 538篇 |
2009年 | 450篇 |
2008年 | 700篇 |
2007年 | 610篇 |
2006年 | 578篇 |
2005年 | 581篇 |
2004年 | 508篇 |
2003年 | 367篇 |
2002年 | 340篇 |
2001年 | 203篇 |
2000年 | 166篇 |
1999年 | 179篇 |
1998年 | 130篇 |
1997年 | 180篇 |
1996年 | 143篇 |
1995年 | 122篇 |
1994年 | 124篇 |
1993年 | 119篇 |
1992年 | 102篇 |
1991年 | 84篇 |
1990年 | 51篇 |
1989年 | 99篇 |
1988年 | 72篇 |
1987年 | 51篇 |
1986年 | 54篇 |
1985年 | 65篇 |
1984年 | 59篇 |
1983年 | 34篇 |
1982年 | 68篇 |
1981年 | 53篇 |
1980年 | 39篇 |
1979年 | 41篇 |
1978年 | 42篇 |
1977年 | 40篇 |
1976年 | 31篇 |
1975年 | 31篇 |
1974年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
For classical solutions of the incompressible Navier-Stokes equations (NSE) the energybalance between kinetic energy, work done by external forces, and viscous dissipation holds rigorously true. It is shown in this paper that standard Galerkin approximations violate energy balance in the case of plane Couette flow, whereas Poiseuille flow turns out to be energy consistent at any cutoff. The main reason for this discrepancy is seen in the different boundary conditions between the stationary linear shear flow and its disturbances. In our analysis, essentially, we introduce an auxiliary external force field which enforces the finite dimensional Galerkin approximation to fulfil the NSE. It is exemplarily demonstrated how the energy discrepancy decreases when the number of disturbed modes is increased which couple to the stationary shear flow. 相似文献
42.
The temperature dependence of pressure broadening of 134 rovibrational transitions of several branches in the ν4 and 2ν2 bands of ammonia perturbed by H2 and N2 has been measured using a high-resolution Fourier transform spectrometer. The temperature range covered during the experiments was between 235 and 296 K. The pressure-broadening linewidths were obtained using the method of multipressure fitting to the measured shapes of the lines. These broadenings were also calculated using a semiclassical model leading to a reasonable agreement with the observations and reproduces well the strong systematic experimental J and K quantum number dependencies. The retrieved values of the linewidths, along with those previously determined from the spectra at room temperature, were used to derive the temperature dependence of both H2 and N2 broadening of NH3 lines. The broadening coefficients were shown to fit closely the well-known exponential law. For both experimental and theoretical results, the temperature exponent n has been obtained. Careful inspection of the experimental values shows that, contrary to the linewidths, the coefficient n is nearly K independent within each J multiplet. Also for a given J it does not seem to exhibit any noticeable variation with the type of rotational transition. On the other hand, the calculated n values exhibit a strong J and K systematic dependencies. n increases with K for a given J, decreases with J for a given K and are independent of the type of rotational transition. 相似文献
43.
44.
We present two methods for the creation of two-particle entangled states of excitons in a coupled quantum dot system. The system contains two identical quantum dots that are coupled by an inter-dot hopping process. The manipulation of the system is succeeded by proper application of an external laser field. 相似文献
45.
Andreas Wallner Margit Hölbling Judith Baumgartner Christoph Marschner 《Silicon Chemistry》2007,3(3-4):175-185
A number of cyclo-and bicyclosilanes have been prepared and structurally characterized by X-ray crystallography and Raman
spectroscopy. 1,1,4,4- and 1,1,3,3-tetrakis(trimethylsilyl)octamethylcyclohexasilanes were found to exhibit unusual twist- and twisted boat-conformations. The UV absorption properties of all compounds were studied and found to show absorption maxima red shifted
compared to the parent compound dodecamethylcyclohexasilane.
Dedicated to Prof. Mitsuo Kira on the occasion of his reception of the Wacker Silicon Award 2005 and in recongnition of his
numerous outstanding achievements in organosilicon chemistry. 相似文献
46.
47.
Andreas E. Schroth 《Journal of Geometry》1991,42(1-2):141-147
The number of circles of a flat Laguerre plane touching three given circles or points depends only on the given geometric configuration but not on the Laguerre plane.Dedicated to Prof. J. Joussen on his 60th birthday 相似文献
48.
49.
50.
Lufthansa Technical Training GmbH (LTT) performs training courses for Lufthansa Technik AG as well as for several other international airlines. Courses of about 670 different types are offered of which several hundred take place each year. The course scheduling problem faced by LTT is to construct a yearly schedule which maximizes the profit margin incurred while meeting a variety of complex precedence, temporal, and resource-related constraints. A “good” operational schedule should also meet a number of additional subordinate objectives. We formalize the problem and develop a heuristic scheme along with several priority rules, as well as a local search algorithm to determine well-suited weights for weighted composite rules. The operational planning situation of 1996 served as our major test instance; additional test instances were constructed by modifying this data. Several computational experiments were carried out to evaluate the performance of the algorithms. It turned out that the best so-found schedule is substantially better in terms of the profit margin incurred than the solution manually constructed by LTT. 相似文献