全文获取类型
收费全文 | 878篇 |
免费 | 10篇 |
国内免费 | 2篇 |
专业分类
化学 | 508篇 |
晶体学 | 3篇 |
力学 | 47篇 |
数学 | 65篇 |
物理学 | 267篇 |
出版年
2017年 | 5篇 |
2016年 | 15篇 |
2015年 | 8篇 |
2014年 | 8篇 |
2013年 | 34篇 |
2012年 | 12篇 |
2011年 | 28篇 |
2010年 | 24篇 |
2009年 | 18篇 |
2008年 | 37篇 |
2007年 | 43篇 |
2006年 | 41篇 |
2005年 | 33篇 |
2004年 | 34篇 |
2003年 | 37篇 |
2002年 | 34篇 |
2001年 | 19篇 |
2000年 | 27篇 |
1999年 | 18篇 |
1998年 | 12篇 |
1997年 | 13篇 |
1996年 | 14篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 17篇 |
1992年 | 17篇 |
1991年 | 16篇 |
1990年 | 19篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 15篇 |
1984年 | 21篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 17篇 |
1980年 | 21篇 |
1979年 | 13篇 |
1978年 | 16篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1975年 | 14篇 |
1974年 | 10篇 |
1973年 | 13篇 |
1972年 | 6篇 |
1971年 | 5篇 |
1970年 | 5篇 |
1969年 | 6篇 |
1935年 | 4篇 |
排序方式: 共有890条查询结果,搜索用时 15 毫秒
81.
Rishav Choudhary Julian J. Girard Sean Clees Sarah E. Johnson Jiankun Shao David F. Davidson Ronald K. Hanson Allen A. Aradi 《Proceedings of the Combustion Institute》2021,38(1):957-965
We report the first shock tube measurements of formaldehyde (CH2O) during the first stage ignition of n-heptane, 2-methylhexane and 3,3-dimethylpentane, in highly diluted fuel/oxygen mixtures in the pressure range of 7–10 atm and temperature range of 700–880 K. Combined time histories of all carbonyl (–C = O) species, CO and fuel were also measured simultaneously in an effort to study the impact of fuel structure on the concentration and the rate of evolution of first stage ignition products. Of the three isomers studied in this work, n-heptane was found to be the fastest, while 3,3-dimethylpentane was found to be the slowest. The differences in the time scale of formation, and plateau concentration of the intermediates between the isomers across the entire range of test conditions suggests a strong dependency of the measured time histories to fuel structure. These species therefore act as markers of the Negative Temperature Coefficient (NTC) behavior of fuels and can be used as targets for developing semi-empirical, hybrid chemistry models of complex, multi-component petroleum derived gasoline and jet fuels. The time histories reported in this work should prove very useful in the refinement of detailed kinetic models of n-heptane, and development of rate rules for branched alkane isomers. 相似文献
82.
A.?N.?WilsonEmail author G.?D.?Dracoulis A.?P.?Byrne P.?M.?Davidson G.?J.?Lane R.?M.?Clark P.?Fallon A.?G?rgen A.?O.?Macchiavelli D.?Ward 《The European Physical Journal A - Hadrons and Nuclei》2005,24(2):179-183
A superdeformed band has been observed in the N = 108 isotope 190Pb. This is the most neutron-deficient Pb isotope in which superdeformed states have been observed. Several theoretical approaches have predicted that N = 108 will mark the limit of observable superdeformation in the Pb isotopes. The band, which consists of five (possibly six) transitions, is observed to feed at least one isomeric level in its decay to the ground state. This decay pattern supports a spin assignment of 10 for the lowest observed level. 相似文献
83.
Sharona Sedghani Cohen Vardit Eckhouse Asher A. Friesem Nir Davidson 《Optics Communications》2009,282(9):1861-1866
We show that by coherently combining several solid state lasers it is possible to obtain a single frequency output. This is experimentally demonstrated by coherently combining four Nd:YAG lasers channels, each with a properly chosen cavity length, in order to suppress unwanted longitudinal modes and obtain a single frequency output. We also present a model that accurately predicts and supports out experimental results. 相似文献
84.
The restriction principle is used to implement a realization of the holomorphic representations of SL(2,R) on L
2 (R
+,t
dt) by way of the standard upper half plane realization. The resulting unitary equivalence establishes a correspondence between functions that transform according to the character e–i(2n++1); under rotations and the Laguerre polynomials. The standard recursion relations amongst Laguerre polynomials are derived from the action of the Lie algebra. 相似文献
85.
[reaction: see text] Mucohalic acids (mucochloric acid (1, 3,4-dichloro-5-hydroxy-5H-furan-2-one) and mucobromic acid (2, 3,4-dibromo-5-hydroxy-5H-furan-2-one)) are inexpensive, commercially available starting materials with multiple functional groups. These compounds have been modified by way of reduction followed by Suzuki cross-coupling reactions involving arylboronic acids to afford highly functionalized alpha,beta-unsaturated gamma-butyrolactones in excellent yield. The synthetic utility of these building blocks was effectively demonstrated through preparation of the antiinflammatory drug Vioxx. 相似文献
86.
R. A. Ritchie D. W. von Oertzen N. J. Davidson R. M. Quick H. G. Miller 《Zeitschrift fur Physik C Particles and Fields》1992,55(2):347-351
Hadron gas models have proved successful in predicting particle production in relativistic nucleus-nucleus collisions. The extension of these models to the smaller systems formed in proton-nucleus collisions requires that the finite size of the system be considered. We study two features introduced by the finite size: the need to conserve strangeness and baryon number exactly by performing calculations in the canonical ensemble, and the inclusion of a finite size geometrical correction term in the single particle density of states. We find significant differences between the grand canonical and canonical ensembles and a strong dependence on the baryon number of the system. 相似文献
87.
Richard L. Martin Larry E. McMurchie Ernest R. Davidson 《International journal of quantum chemistry》1978,13(2):161-168
The completeness of a basis set for ethylene is examined relative to its ability to describe transition moments. The double zeta (Dunning contraction) plus polarization plus Rydberg Cartesian Gaussian set does much better for length than for velocity moments. An attempt is made to interpret the transition moment sums for the occupied orbitals. 相似文献
89.
Ohne Zusammenfassung 相似文献
90.
Stereoselective synthesis of d-desosamine diacetate ester (iii, R = Ac) was achieved from the glycal (ii). generated by tungsten carbonyl-catalyzed cycloisomerization of the corresponding amino-alkynol (i). A wide variety of N-substituents (R, R') are compatible with the cycloisomerization, provided that at least one R or R' is an acyl derivative. 相似文献