全文获取类型
收费全文 | 4969篇 |
免费 | 115篇 |
国内免费 | 7篇 |
专业分类
化学 | 3917篇 |
晶体学 | 6篇 |
力学 | 42篇 |
数学 | 660篇 |
物理学 | 466篇 |
出版年
2019年 | 40篇 |
2018年 | 36篇 |
2017年 | 26篇 |
2016年 | 100篇 |
2015年 | 64篇 |
2014年 | 99篇 |
2013年 | 145篇 |
2012年 | 146篇 |
2011年 | 154篇 |
2010年 | 130篇 |
2009年 | 118篇 |
2008年 | 161篇 |
2007年 | 159篇 |
2006年 | 181篇 |
2005年 | 198篇 |
2004年 | 172篇 |
2003年 | 139篇 |
2002年 | 181篇 |
2001年 | 109篇 |
2000年 | 107篇 |
1999年 | 105篇 |
1998年 | 85篇 |
1997年 | 97篇 |
1996年 | 96篇 |
1995年 | 76篇 |
1994年 | 88篇 |
1993年 | 90篇 |
1992年 | 96篇 |
1991年 | 89篇 |
1990年 | 67篇 |
1989年 | 91篇 |
1988年 | 87篇 |
1987年 | 84篇 |
1986年 | 71篇 |
1985年 | 96篇 |
1984年 | 111篇 |
1983年 | 64篇 |
1982年 | 86篇 |
1981年 | 112篇 |
1980年 | 84篇 |
1979年 | 102篇 |
1978年 | 68篇 |
1977年 | 68篇 |
1976年 | 59篇 |
1975年 | 77篇 |
1974年 | 50篇 |
1973年 | 70篇 |
1972年 | 51篇 |
1971年 | 43篇 |
1970年 | 52篇 |
排序方式: 共有5091条查询结果,搜索用时 0 毫秒
991.
Andreas Albrecht Lars-Christian Heinz Dieter Lilge Harald Pasch 《Macromolecular Symposia》2007,257(1):46-55
Summary: The chromatographic separation of ethylene-propylene (EP) copolymers with regard to chemical composition was accomplished by a new technique - high- temperature gradient HPLC. Using a mobile phase of ethylene glycol monobutylether (EGMBE) and 1,2,4–trichlorobenzene (TCB), and silica gel as the stationary phase, copolymers with different ethylene contents were separated according to their chemical compositions. Using a sample solvent of n-decanol and a column temperature of 140 °C, chromatographic conditions were established that correspond to separation in a precipitation-redissolution mechanism. With the aim to obtain further information on the separation process, the HPLC system was coupled to FTIR spectroscopy through a LC-Transform interface. The FTIR data confirmed that the copolymers were separated according to the ethylene content of the eluted samples. 相似文献
992.
In the present paper measured and simulated vibrations of viscoplastic plates under impulsive loadings are compared to each other. The aim is to determine how accurately the measured deformations can be calculated by the chosen constitutive and structural theories. The damage growth in the plate specimens until failure is predicted by finite element simulations and compared to shock tube experiments. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
993.
994.
Dietmar Appelhans Hartmut Komber Ralf Kirchner Jürgen Seidel Chih‐Feng Huang Dieter Voigt Dirk Kuckling Feng‐Chih Chang Brigitte Voit 《Macromolecular rapid communications》2005,26(8):586-591
Summary: Polypeptide‐shelled poly(propylene imine) dendrimers were realized by ring‐opening polymerization of α‐amino acid N‐carboxyanhydrides, initiated by dendrimers as core molecules. Polypeptides with 2nd generation core were used as model compounds to investigate interior complexes between metal ion and surface‐modified dendrimers. Micro‐calorimetric measurements outlined the formation of approximate 1:1 complexes between CuII and polypeptide‐shelled dendrimers and the influence of polypeptide chain compositions on differential molar heats of complexation.
995.
Xuehao He Jürgen Nagel Dieter Lehmann Gert Heinrich 《Macromolecular theory and simulations》2005,14(5):305-311
Summary: The interface structure between two immiscible melts, a polycondensate polymer A (e.g., polycarbonate, polyester or polyamide) and a polymer B, was studied by means of Monte Carlo simulations using the bond fluctuation model. Polymer B contained a reactive end group (e.g., OH, NH2 or COOH). Copolymers were generated in‐situ at the interfaces by transreactions (alcoholysis, aminolysis or acidolysis), composing of various length of block A, depending on the position of transreaction in the polycondensate chain A. The content of copolymer at the interface increased with the time, particular fast at the early stage. Fragments of polymers A were released with an end group, reactive to polymers A. This resulted in the proceeding of internal transreactions. An asymmetric interface structure was formed. The simulation also showed that copolymers generated by interfacial transreactions increased the compatibility of the two polymers and enhanced the adhesion strength at the interfaces.
996.
This paper provides definitions for the evolutionary stability of sets of strategies based on simple fitness comparisons in the spirit of the definition of an evolutionarily stable strategy (ESS) by Taylor and Jonker (1978). It compares these with the set-valued notions of Thomas (1985d) and Swinkels (1992). Provided
only that the fitness function is analytic, our approach yields an alternative characterization of Thomas' evolutionarily stable sets (ES Sets) which does not rely on the structure or topology of the underlying strategy space. Moreover, these sets are shown to have
a very special geometric structure and to be finite in number. For bimatrix games ES Sets are shown to be more uniformly robust
against mutations than apparent from the definition and hence to be equilibrium evolutionarily stable sets in the sense of Swinkels (1992).
Received November 1995/Final version December 2000 相似文献
997.
Henrik Birkedal Dieter Schwarzenbach Philip Pattison 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(8):975-977
The crystal structure of the neuroactive artificial dipeptide N‐benzyloxycarbonylprolyl‐d ‐leucine, C19H26N2O5, was solved using synchrotron radiation data collected on a very small crystal (20 × 20 × 380 μm). The molecules form hydrogen‐bonded 21 helices. The acid carbonyl group does not participate in strong hydrogen bonds. This is interpreted as a consequence of close‐packing requirements. 相似文献
998.
Lensless Fourier holography for digital holographic interferometry on biological samples 总被引:1,自引:0,他引:1
Dieter Dirksen H. Droste B. Kemper H. Deler M. Deiwick H. H. Scheld G. von Bally 《Optics and Lasers in Engineering》2001,36(3)
Digital holography as a tool for highly sensitive, interferometric non-destructive testing has several advantages compared to holographic measurements based on conventional storage media like an all-digital processing and a direct access to the phase of the object wave. Experimental results of interferometric investigations of heart valve bio-prostheses with a setup for lensless Fourier holography are presented which demonstrate that this technique is applicable to such biological samples with their wet and unstable surfaces. Limitations on size and resolution of the reconstructed object caused by the properties of the CCD sensor are discussed. 相似文献
999.
1000.
The Friedel–Crafts alkylation of furans by the Michael acceptor, β-nitrostyrene, is greatly accelerated by the use of the Lewis acid catalyst and solvent, 5 M lithium perchlorate in diethyl ether (LDPE). 相似文献