全文获取类型
收费全文 | 2743篇 |
免费 | 95篇 |
国内免费 | 18篇 |
专业分类
化学 | 1938篇 |
晶体学 | 19篇 |
力学 | 41篇 |
数学 | 360篇 |
物理学 | 498篇 |
出版年
2023年 | 18篇 |
2022年 | 43篇 |
2021年 | 46篇 |
2020年 | 44篇 |
2019年 | 41篇 |
2018年 | 33篇 |
2017年 | 34篇 |
2016年 | 73篇 |
2015年 | 69篇 |
2014年 | 67篇 |
2013年 | 116篇 |
2012年 | 181篇 |
2011年 | 212篇 |
2010年 | 119篇 |
2009年 | 133篇 |
2008年 | 190篇 |
2007年 | 196篇 |
2006年 | 194篇 |
2005年 | 140篇 |
2004年 | 97篇 |
2003年 | 104篇 |
2002年 | 95篇 |
2001年 | 50篇 |
2000年 | 58篇 |
1999年 | 36篇 |
1998年 | 30篇 |
1997年 | 31篇 |
1996年 | 43篇 |
1995年 | 33篇 |
1994年 | 20篇 |
1993年 | 19篇 |
1992年 | 19篇 |
1991年 | 17篇 |
1990年 | 18篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1984年 | 20篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 6篇 |
1980年 | 14篇 |
1979年 | 10篇 |
1978年 | 11篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1934年 | 6篇 |
1930年 | 6篇 |
排序方式: 共有2856条查询结果,搜索用时 0 毫秒
121.
Nierengarten H Leize E Breuning E Garcia A Romero-Salguero F Rojo J Lehn JM Van Dorsselaer A 《Journal of mass spectrometry : JMS》2002,37(1):56-62
The self-assembly of the terdentate ligands 1a-h, based on terpyridine-like binding sites, with octahedrally coordinated metal ions, such as Fe(II), Co(II), Cu(II), Zn(II), Cd(II), Hg(II) and Pb(II), leads to the formation of the supramolecular grid-type complexes 2a-c(M(II)), 3d-g(M(II)) and 4h(M(II)). The structures and compositions of these coordination complexes in solution were deduced from electrospray mass spectrometry (ESMS) measurements. The results agree with the data available from x-ray radiocrystallography in the solid state and/or NMR spectroscopy in solution. ESMS may be applied in cases where other methods are difficult to use or inconclusive. This study stresses the power of ESMS in supramolecular chemistry. 相似文献
122.
Morilla ME Morfes G Nicasio MC Belderrain TR Mar Díaz-Requejo M Graiff C Tiripicchio A Sánchez-Delgado R Pérez PJ 《Chemical communications (Cambridge, England)》2002,(17):1848-1849
N,N, N',N'-Tetraethylethylenediamine undergoes simple or double intramolecular dealkylation reactions in the presence of the complexes [RuCl2(diene)]n (diene = cod, nbd) or trans-[RuCl2(diene)(morfoline)2 at 80 degrees C to afford chelating amine ligands which contains one or two N-H functionalities. 相似文献
123.
124.
Pasternack RF Gibbs EJ Bruzewicz D Stewart D Engstrom KS 《Journal of the American Chemical Society》2002,124(14):3533-3539
trans-Bis(N-methylpyridinium-4-yl)diphenylporphine forms extended, organized assemblies on DNA templates under appropriate conditions of concentration, ionic strength, and temperature. Addition of beta-cyclodextrin to these arrays leads to their disassembly as evidenced by changes in extinction, circular dichroism, and resonance light scattering spectra. The structure or flexibility of the polymer template has an effect on the rate of disassembly; the reaction is faster on a poly(dG-dC)(2) surface than on ct DNA. The kinetic profiles for the disassembly process can be fit with great precision with a two-kinetic parameter equation in which the rate constant is itself a function of time. The reaction rate, studied in the presence of excess beta-CD, shows a dependence on the mode of detection. A model is presented to account for these observations in which the arrays become increasingly reactive with time due to beta-CD attack at the interior of the porphyrin assemblies as well as the ends. 相似文献
125.
García-Herrero A Montero E Muñoz JL Espinosa JF Vián A García JL Asensio JL Cañada FJ Jiménez-Barbero J 《Journal of the American Chemical Society》2002,124(17):4804-4810
We show that the conformational features of the molecular complexes of E. coli beta-galactosidase and O-glycosides may differ from those formed with closely related compounds in their chemical nature, such as C- and S-glycosyl analogues. In the particular case presented here, NMR and ab initio quantum mechanical results show that the 3D-shapes of the ligand/inhibitor within the enzyme binding site depend on the chemical nature of the compounds. In fact, they depend on the relative size of the stereoelectronic barriers for chair deformation or for rotation around Phi glycosidic linkage. 相似文献
126.
We discuss forward-backward charge asymmetries for lepton-pair production in association with a large-transverse-momentum jet at hadron colliders. The lepton charge asymmetry relative to the jet direction A(j)(FB) gives a new determination of the effective weak mixing angle sin((2)theta(lept)(eff)(M(2)(Z)) with a statistical precision after cuts of approximately 10(-3) (8x10(-3)) at LHC (Tevatron). This is to be compared with the current uncertainty at LEP and SLD from the asymmetries alone, 2x10(-4). The identification of b jets also allows for the measurement of the bottom-quark-Z asymmetry A(b)(FB) at hadron colliders, the resulting statistical precision for sin((2)theta(lept)(eff)(M(2)(Z)) being approximately 9x10(-4) (2x10(-2) at Tevatron), also lower than the reported precision at e(+)e(-) colliders, 3x10(-4). 相似文献
127.
Rüdel A Hentges R Becker U Chakraborty HS Madjet ME Rost JM 《Physical review letters》2002,89(12):125503
The dynamics of the photoionization of the two outermost orbitals of C(60) has been studied in the oscillatory regime from threshold to the carbon K edge. We show that geometrical properties of the fullerene electronic hull, such as its diameter and thickness, are contained in the partial photoionization cross sections by examining ratios of partial cross sections as a function of the photon wave number in the Fourier conjugated space. Evaluated in this unconventional manner photoemission data reveal directly the desired spatial information. 相似文献
128.
We present in this work some new theoretical results concerning an influence of the shape of core on the development of magnetization. As a special case the rotary symmetric objects with non-homogeneous magnetization were investigated. The shape of core was optimized on the basis of various practical criteria. 相似文献
129.
Guido E del Pino 《Statistics & probability letters》1984,2(4):245-248
In this paper we consider the full rank regression model with arbitrary covariance matrix: Y = Xß + ε. It is shown that the effect of restricting the information Y to T = A′Y may be analyzed through an associatedi regression problem which is amenable to solution by two step least squares. The results are applied to the important case of missing observations, where some classical results are rederived. 相似文献
130.