全文获取类型
收费全文 | 532186篇 |
免费 | 4021篇 |
国内免费 | 1326篇 |
专业分类
化学 | 254294篇 |
晶体学 | 8231篇 |
力学 | 28704篇 |
综合类 | 17篇 |
数学 | 75883篇 |
物理学 | 170404篇 |
出版年
2021年 | 4302篇 |
2020年 | 4562篇 |
2019年 | 5302篇 |
2018年 | 12794篇 |
2017年 | 13278篇 |
2016年 | 12918篇 |
2015年 | 6162篇 |
2014年 | 9801篇 |
2013年 | 21776篇 |
2012年 | 19621篇 |
2011年 | 28219篇 |
2010年 | 19837篇 |
2009年 | 20038篇 |
2008年 | 25388篇 |
2007年 | 27579篇 |
2006年 | 16786篇 |
2005年 | 18605篇 |
2004年 | 15697篇 |
2003年 | 14474篇 |
2002年 | 13199篇 |
2001年 | 14260篇 |
2000年 | 10733篇 |
1999年 | 8124篇 |
1998年 | 6849篇 |
1997年 | 6743篇 |
1996年 | 6379篇 |
1995年 | 5542篇 |
1994年 | 5578篇 |
1993年 | 5353篇 |
1992年 | 5958篇 |
1991年 | 6256篇 |
1990年 | 5903篇 |
1989年 | 5920篇 |
1988年 | 5634篇 |
1987年 | 5767篇 |
1986年 | 5414篇 |
1985年 | 6873篇 |
1984年 | 7046篇 |
1983年 | 5858篇 |
1982年 | 5884篇 |
1981年 | 5667篇 |
1980年 | 5423篇 |
1979年 | 5986篇 |
1978年 | 5946篇 |
1977年 | 6039篇 |
1976年 | 6043篇 |
1975年 | 5701篇 |
1974年 | 5592篇 |
1973年 | 5731篇 |
1972年 | 4176篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
33.
J. Berny 《The Journal of the Operational Research Society》1989,40(12):1121-1127
This paper presents an alternative to the beta continuous probability distribution for risk analysis. Particular attention has been given to two major applications of distributions, namely project management risk and critical path analysis (PERT). In conjunction with the beta, the triangular and normal distributions are frequently employed in order to give sufficient robustness to risk analysis. The beta distribution, as used in PERT, has a major theoretical implementation flaw. The new distribution was developed to give a possible alternative method of assessing risk. It is shown that the requirement to estimate the most pessimistic variate may be replaced by the probability to exceed the mode. Proposals for other simplifications in risk analysis are discussed. Practical means to validate the most appropriate distributions for risk analysis are outlined, and a cost-data case study is included. 相似文献
34.
We consider the growth of a spherical crystal in a supersaturatedsolution. In the first part, existence and uniqueness resultsfor radially symmetric growth are obtained, provided that thesupersaturation is not too large; conversely, when the far-fieldsupersaturation exceeds a critical value, it is shown that theradially symmetric solution ceases to exist in finite time.In the second part, we examine the linear stability of a radiallysymmetric similarity solution (in which the radius grows ast?) to shape perturbations. The results are compared with previousquasi-static analyses, and, in particular, the critical radiusat which the crystal becomes unstable is found to be largerfor small supersaturations, but smaller for large supersaturations,than those predicted by the quasi-static analysis 相似文献
35.
36.
37.
A convenient method is proposed for the synthesis of all the individual methyl ethers of methyl 2-acetamido-2-deoxy-α-D-glucopyranoside based on the partial methylation of 2-acetamido-2-deoxy-α-D-glucopyranoside with dimethyl sulfate in an alkaline medium followed by preparative liquid column chromatography on silica gel of the resulting mixture of methyl ethers. 相似文献
38.
D. N. Zaporozhets 《Journal of Mathematical Sciences》2006,137(1):4525-4530
In this note, we find the distibution of the number of real zeros of a random polynomial. We also derive a formula for the
expected number of complex zeros lying in a given domain of the complex plane. Bibliography: 7 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 320, 2004, pp. 69–79. 相似文献
39.
The main result of the paper is a theorem, using which a new proof of Roth’s theorem is obtained, a new solvability criterion
for the matrix equation AX-YB = C is proved, a formula for a particular solution of the latter is derived, and the least of
the orders of square nonsingular matrices containing a given rectangular matrix as a submatrix is determined. Bibliography:
5 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 323, 2005, pp. 15–23. 相似文献
40.
Using the method of the tensor Green’s function of the wave equation, the differential and total cross sections for the scattering of surface optical electromagnetic waves (surface plasmon polaritons) by a spherical nanoparticle into surface plasmon polaritons and light have been obtained with the inclusion of the magnetic dipole contribution. Using the example of noble metal systems, it has been shown that the magnetic dipole contribution may significantly affect the angular dependence of the differential cross sections and increase their anisotropy as the plasmon wavelength increases. 相似文献