全文获取类型
收费全文 | 527篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
化学 | 329篇 |
晶体学 | 69篇 |
力学 | 10篇 |
数学 | 42篇 |
物理学 | 82篇 |
出版年
2017年 | 4篇 |
2016年 | 4篇 |
2014年 | 7篇 |
2013年 | 13篇 |
2012年 | 5篇 |
2011年 | 9篇 |
2010年 | 5篇 |
2009年 | 7篇 |
2008年 | 18篇 |
2007年 | 17篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 13篇 |
2003年 | 18篇 |
2002年 | 9篇 |
2001年 | 12篇 |
2000年 | 14篇 |
1999年 | 12篇 |
1998年 | 9篇 |
1997年 | 11篇 |
1996年 | 15篇 |
1995年 | 7篇 |
1994年 | 15篇 |
1993年 | 11篇 |
1992年 | 12篇 |
1991年 | 19篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 13篇 |
1982年 | 4篇 |
1981年 | 12篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 16篇 |
1975年 | 13篇 |
1974年 | 8篇 |
1973年 | 10篇 |
1972年 | 3篇 |
1970年 | 5篇 |
1969年 | 6篇 |
1968年 | 10篇 |
1967年 | 4篇 |
1935年 | 4篇 |
排序方式: 共有532条查询结果,搜索用时 328 毫秒
1.
2.
3.
T. Gleisberg F. Krauss C. G. Papadopoulos A. Schälicke S. Schumann 《The European Physical Journal C - Particles and Fields》2004,34(2):173-180
In this paper total cross sections for signals and backgrounds of top- and Higgs-production channels in e + e- collisions at a future linear collider are presented. All channels considered are characterized by the emergence of six-particle final states. The calculation takes into account the full set of tree-level amplitudes in each process. Two multi-purpose parton level generators, HELAC/PHEGAS and AMEGIC + + , are used, and their results are found to be in perfect agreement.Received: 26 November 2003, Revised: 15 January 2004, Published online: 3 March 2004 相似文献
4.
The primary objective of this investigation was to document fluctuations of levels of ions in airborne particles and in rain water with the help of ion chromatography. The environmental emission situation in the investigated geographic area is characterized by a widespread use of domestic coal-burning furnaces. The use of a parallel impactor for particulate sampling permits the results to be interpreted additionally in terms of particle size. The anions and cations were extracted from the filters in the sampling devices into ethanol-water mixtures by sonication. Rain water samples were analysed after a simple dilution step. The data obtained on ionic fluctuations are compared with similar data sets published by other laboratories. 相似文献
5.
6.
Khoroshen'kov G. V. Fag A. A. Bochkarev M. N. Dechert S. Schumann H. 《Russian Chemical Bulletin》2003,52(8):1715-1719
The reactions of LnI2 (Ln = Nd (1) or Dy (2)) with cyclopentadiene (CpH) in THF at 0 °C afforded the CpLnI2(THF)3 complexes in 65—67% yields. The reaction of thulium diiodide (3) with an excess of CpH at 60 °C produced CpTmI2(THF)3, Cp2TmI(THF)2, and TmI3(THF)3 in 21, 58, and 63% yields, respectively. The reactions of 1 and 2 with pentamethylcyclopentadiene (Cp*H) in THF were accompanied by disproportionation giving rise to the Cp*2LnI(THF)2 and LnI3(THF)
x
complexes. Neodymium triiodide was isolated in the ionic form [NdI2(THF)5]+[NdI4(THF)2]–. Its structure and the structure of CpTmI2(THF)3 were established by X-ray diffraction analysis. 相似文献
7.
Iron-silicon thin films have been characterized by means of analytical transmission electron microscopic methods. Under certain conditions — composition and annealing temperature — these films exhibit thermoelectric behavior. In particular, the morphology and phase formation which results from annealing of these films, and doping with oxygen and nitrogen, are of interest. The thermoelectric phase -FeSi2 is formed at temperatures above 500°C. This phase is transformed into electrically conducting phases at about 1000°C. A small oxygen content does not influence this crystallization process. If the oxygen content is higher than 15 atom-% the electrically conducting phases exist even at 500°C. The presence of a small nitrogen content inhibits the formation of the -FeSi2 phase. The development of silicon and iron nitrides is possible. 相似文献
8.
Fedushkin I. L. Kurskii Yu. A. Nevodchikov V. I. Bochkarev M. N. Müchle S. Schumann H. 《Russian Chemical Bulletin》2002,51(1):160-169
ansa-Metallocenes (5:5-C24H16)M(THF)2 (M = Sm (1), Yb (2), Ca (3)) and (5:5-C24H16)MI(THF) (M = Dy (8), Er (9), Tm (10), Lu (11)) were prepared in 50—90% yields by the in situ reactions of two equivalents of potassium acenaphthylenide K+C12H8
– with MI2 or MI3, respectively. Complexes 2 and 3 were also obtained by direct reduction of acenaphthylene with ytterbium and calcium naphthalenides, respectively. An ESR signal of the acenaphthylene radical anion, which was observed upon dissolution of compound 2 in THF, indicates that the [C24H16]2–
ansa-ligand dissociated into two [C12H8]·– radical anions. Hydrolysis of complex 2 in benzene afforded 1,1",3,3"-tetrahydro-3,3"-biacenaphthylene (4) and 3,3",4,4"-tetrahydro-3,3"-biacenaphthylene (5). The reaction of complex 2 with ZrCl4 and the reaction of compound 3 with Me3SiCl proceeded with the cleavage of the C—C bond between two acenaphthylene fragments of the [C24H16]2–
ansa-ligand to produce (2-C12H8)ZrCl2(THF)3 (6) and bis(trimethylsilyl)acenaphthene (Me3Si)2C12H8 (7), respectively. Compounds 1—3, 6, 7, and 11 were characterized by 1H and 13C NMR spectroscopy. The temperature dependence of the 1H NMR spectrum of compound 11 in tetrahydrofuran is indicative of the dynamic exchange of the solvent molecules in the coordination sphere of the Lu atom. After cooling of the solution to 210 K, the dynamic process was terminated as evidenced by the nonequivalence of the 1H signals of two acenaphthylene fragments. According to the X-ray diffraction data for complex 11, dimerization of two acenaphthylene radical anions at the Lu atom gave rise to the rac-ansa-metallocene structure. In compound 11, the Lu atom is 5-coordinated by two five-membered rings of the acenaphthylene ligands and also by the I atom and the THF molecule. The coordination environment about the Lu atom is a distorted tetrahedron. The average distance between the lutetium atom and the carbon atoms of the five-membered rings is 2.623 . 相似文献
9.
A method for the determination of geosmin and 2-methylisoborneol (MIB) in water by solid-phase microextraction (SPME) is presented. Various SPME fibre chemistries have been compared for their efficiency in extracting MIB from water. Extraction conditions including the extraction time and temperature have been optimised. A 30 ml water sample is extracted for 20 min at 60 degrees C using a divinylbenzene fibre, and the extract analysed by gas chromatography with ion-trap mass spectrometry detection. d5-Geosmin and d3-MIB are added as internal standards to compensate for any variability in the SPME process which is not carried out to equilibrium. Chemical ionisation, using acetonitrile as the reagent gas, was found to give superior sensitivity to electron impact ionisation (EI) for the detection of MIB. EI was used as the ionisation mode for detection of geosmin. The method shows good linearity over the concentration range 5-40 ng l-1 and gives detection limits of 1 ng l-1 for both geosmin and MIB. Recovery (93-110%) and precision (3-12%) over this concentration range, for both raw and treated drinking waters, are comparable to currently employed methods such as closed-loop stripping analysis (CLSA). The method offers the advantage of being simple to use, with much shorter analysis times in comparison to CLSA. 相似文献
10.
Contributions to the Chemistry of Transition Metal Alkyl Compounds. 63. Preparation and Crystal Structure of Tetramethyltitanium Tetrahydrofuran Me4Ti · 2THF 1 dissoziates partially in n-pentane. The formed Me4Ti · THF 2 could be isolated. According to X-ray structure determination the molecules of 2 have a trigonalbipyramidal shape with the THF molecule in axial position. 相似文献