全文获取类型
收费全文 | 4752篇 |
免费 | 120篇 |
专业分类
化学 | 2820篇 |
晶体学 | 37篇 |
力学 | 153篇 |
数学 | 717篇 |
物理学 | 1145篇 |
出版年
2021年 | 28篇 |
2020年 | 63篇 |
2019年 | 42篇 |
2018年 | 52篇 |
2017年 | 41篇 |
2016年 | 93篇 |
2015年 | 106篇 |
2014年 | 101篇 |
2013年 | 201篇 |
2012年 | 264篇 |
2011年 | 282篇 |
2010年 | 157篇 |
2009年 | 129篇 |
2008年 | 215篇 |
2007年 | 220篇 |
2006年 | 204篇 |
2005年 | 210篇 |
2004年 | 193篇 |
2003年 | 148篇 |
2002年 | 156篇 |
2001年 | 74篇 |
2000年 | 68篇 |
1999年 | 59篇 |
1998年 | 48篇 |
1997年 | 57篇 |
1996年 | 41篇 |
1995年 | 58篇 |
1994年 | 34篇 |
1993年 | 35篇 |
1992年 | 49篇 |
1991年 | 33篇 |
1990年 | 39篇 |
1989年 | 33篇 |
1988年 | 51篇 |
1987年 | 44篇 |
1985年 | 33篇 |
1984年 | 30篇 |
1983年 | 27篇 |
1982年 | 36篇 |
1981年 | 48篇 |
1980年 | 39篇 |
1979年 | 28篇 |
1978年 | 40篇 |
1977年 | 32篇 |
1976年 | 35篇 |
1975年 | 31篇 |
1974年 | 31篇 |
1973年 | 26篇 |
1933年 | 24篇 |
1908年 | 27篇 |
排序方式: 共有4872条查询结果,搜索用时 15 毫秒
31.
Abstract Taking advantage of the same configuration present at C-5 and C-5′ in sucrose, 6,6′-diprotected sucrose derivatives were transformed into enantiomerically pure glycerol derivatives. This was achieved by oxidative ring cleavage of both the glucopyranosyl ring as well as the fructofuranosyl moiety followed by reduction of the resulting tetraaldehyde and subsequent per-O-protection of the resulting pentahydroxy compound. The obtained intermediate was hydrolysed under acidic conditions to furnish two equivalents of partially protected chiral glycerol derivative per molecule of starting material. The efficiencies of sodium metaperiodate and lead tetraacetate as oxidizing agents were compared and the side reactions observed in these procedures were investigated. 相似文献
32.
33.
34.
M. Jonker F. Udo J. V. Allaby U. Amaldi G. Barbiellini A. Capone W. Flegel M. Metcalf J. Meyer F. L. Navarria J. Panman A. M. Wetherell K. Winter F. W. Büsser H. Daumann P. D. Gall E. Metz F. Niebergall K. H. Ranitzsch P. Stähelin E. Grigoriev V. Kaftanov V. Khovansky A. Rosanov A. Baroncelli B. Borgia C. Bosio F. Ferroni E. Longo P. Monacelli F. de Notaristefani P. Pistilli C. Santoni V. Valente 《Zeitschrift fur Physik C Particles and Fields》1983,17(3):211-217
The question whether scalar-type interactions contribute to weak interactions at large momentum transfer has been investigated by a measurement of the longitudinal polarization of positive muons produced in charged-current interactions of high-energy antineutrinos with iron. At an average momentum transfer <Q 2>=4 GeV2 the muon spin is found to be oriented forward with respect to the muon momentum vector, with an average polarization of 1.10±0.24, consistent with positive helicity. A limit on scalar contributions of σs, p/σtot <7% at the 95% confidence level can be deduced. A search for violation of time reversal invariance which could manifest itself by a polarization component perpendicular to the muon production plane gave a limit of σtv/σtot <16% (95% c.l.). It is concluded that the weak leptonic charged current retains its dominant vector and axial vector structure at large momentum transfers. 相似文献
35.
J. Badalec J. Ďatlov K. Jakubka VI. Kopecký Š. Körbel L. Kryška P. Magula J. Stöckel F. Žáček S. Nanobashvili 《Czechoslovak Journal of Physics》1983,33(7):787-790
The work is devoted to the study of the LH wave effect on the peripheral plasma of the TM-1-MH tokamak. The observed enhancement of the ion saturated current in the limiter shadow is interpreted as heating of the peripheral ions by absorption of decay waves generated in this region due to the nonlinear wave-plasma interaction. 相似文献
36.
P. Heitjans B. Bader H. -J. Stöckmann K. Dörr G. Kiese H. Ackermann P. Freiländer W. Müller-Warmuth K. Meise-Gresch 《Hyperfine Interactions》1983,16(1-4):597-600
Nuclear spin-lattice relaxation in Li20·2Si02 glass below 200 K has been studied using the asymmetric Β-decay radiation of polarized8Li (T1/2=0.Bs) nuclei produced by capture of polarized neutrons. Transients of the8Li polarization follow an exp(?√E/T1) law. The dependence of the spin-lattice relaxation rate ⊥¯1 1 on temperature T and magnetic field B can roughly be described by T¯1 1~T/B. The interpretation is based on the assumption that for8Li, contrary to7Li in the same glass, spin-diffusion is absent and that each probe nucleus is coupled by quadrupolar interaction to an individual distribution of nearby centres typical of glasses. The fluctuation of these centres causing relaxation may be induced by either a multi-phonon or a thermally activated motional process. 相似文献
37.
Trond Stølen Gustavsen 《Compositio Mathematica》2003,138(2):199-231
We relate the equisingular deformation theory of plane curve singularities and sandwiched surface singularities. We show the existence of a smooth map between the two corresponding deformation functors and study the kernel of this map. In particular we show that the map is an isomorphism when a certain invariant is large enough. 相似文献
38.
We prove global existence of solutions to the continuous nonhomogeneous Smoluchowski equation for coagulation rates satisfying a more general structure condition than the Galkin–Tupchiev monotony hypothesis considered in (Ph. Laurençot, S. Mischler, Arch. Rational Mech. Anal. 162 (1) (2002) 45–99). The Smoluchowski coagulation rate fulfils this condition as well as some rates which vanish on the diagonal. Under the condition of positivity of the coagulation rate outside of the diagonal we prove that solutions tend to 0 in the large time asymptotic. These results depend on a new estimate from below for the dissipation rate of the Lp-norm, p>1. To cite this article: S. Mischler, M. Rodriguez Ricard, C. R. Acad. Sci. Paris, Ser. I 336 (2003). 相似文献
39.
Microarrays are a popular technology to study genes that are differentially expressed between two conditions. In this Note, we propose an iterative procedure to determine the biggest subset of non-differentially expressed genes. We prove a pseudo Markov relationship that allows practical computations. We obtain explicit expressions for FDR and the level of the proposed test at each step. To cite this article: A. Bar-Hen, S. Robin, C. R. Acad. Sci. Paris, Ser. I 337 (2003). 相似文献
40.
Charles K. Chui Wenjie He Joachim Stöckler Qiyu Sun 《Advances in Computational Mathematics》2003,18(2-4):159-187
When a cardinal B-spline of order greater than 1 is used as the scaling function to generate a multiresolution approximation of L
2=L
2(R) with dilation integer factor M2, the standard matrix extension approach for constructing compactly supported tight frames has the limitation that at least one of the tight frame generators does not annihilate any polynomial except the constant. The notion of vanishing moment recovery (VMR) was introduced in our earlier work (and independently by Daubechies et al.) for dilation M=2 to increase the order of vanishing moments. This present paper extends the tight frame results in the above mentioned papers from dilation M=2 to arbitrary integer M2 for any compactly supported M-dilation scaling functions. It is shown, in particular, that M compactly supported tight frame generators suffice, but not M–1 in general. A complete characterization of the M-dilation polynomial symbol is derived for the existence of M–1 such frame generators. Linear spline examples are given for M=3,4 to demonstrate our constructive approach. 相似文献