全文获取类型
收费全文 | 5378篇 |
免费 | 44篇 |
国内免费 | 7篇 |
专业分类
化学 | 2650篇 |
晶体学 | 126篇 |
力学 | 161篇 |
综合类 | 3篇 |
数学 | 619篇 |
物理学 | 1870篇 |
出版年
2019年 | 55篇 |
2018年 | 70篇 |
2017年 | 74篇 |
2016年 | 79篇 |
2015年 | 54篇 |
2014年 | 92篇 |
2013年 | 227篇 |
2012年 | 171篇 |
2011年 | 199篇 |
2010年 | 110篇 |
2009年 | 155篇 |
2008年 | 190篇 |
2007年 | 200篇 |
2006年 | 157篇 |
2005年 | 141篇 |
2004年 | 144篇 |
2003年 | 126篇 |
2002年 | 132篇 |
2001年 | 111篇 |
2000年 | 103篇 |
1999年 | 88篇 |
1998年 | 57篇 |
1997年 | 59篇 |
1996年 | 73篇 |
1995年 | 61篇 |
1994年 | 72篇 |
1993年 | 56篇 |
1992年 | 73篇 |
1991年 | 76篇 |
1990年 | 82篇 |
1989年 | 58篇 |
1988年 | 46篇 |
1987年 | 61篇 |
1986年 | 65篇 |
1985年 | 65篇 |
1984年 | 85篇 |
1983年 | 88篇 |
1982年 | 80篇 |
1981年 | 87篇 |
1980年 | 100篇 |
1979年 | 76篇 |
1978年 | 93篇 |
1977年 | 95篇 |
1976年 | 71篇 |
1975年 | 58篇 |
1974年 | 51篇 |
1973年 | 50篇 |
1972年 | 41篇 |
1971年 | 36篇 |
1970年 | 39篇 |
排序方式: 共有5429条查询结果,搜索用时 15 毫秒
991.
Gaillard de Sémainville P Hoffmann D George Ch Herrmann H 《Physical chemistry chemical physics : PCCP》2007,9(8):958-968
Using laser photolysis experiments, the reactivity of the nitrate radical towards four carbonyl compounds and three carboxylic acids was studied. All kinetics measurements were carried out as a function of the temperature in the range from 278 K to 318 K. Furthermore, the effect of the acid-base equilibrium on the reactivity of the three acids was studied by measuring the activation parameters of the dissociated and undissociated acids at pH = 6 and pH = 0.5, respectively. The following Arrhenius expressions were obtained: [Formulas: see text]. Errors stated throughout this study are statistical errors for a confidence interval of 95%. The importance of the obtained results for the understanding of the tropospheric oxidation processes is discussed. The kinetics resulting from this work are compared with results for other atmospheric radicals. 相似文献
992.
Aleksander Kufelnicki Magdalena Woźniczka Lilianna Chęcińska Magdalena Miernicka Elżbieta Budzisz 《Polyhedron》2007
Two new ligands of the coumarin type have been synthesized and characterized by 1H, 13C NMR, IR and MS. The crystal and molecular structures of ligand 2, determined by the X-ray diffraction method, are presented. With copper(II) these ligands create solid complexes of the type CuLCl2, where L is 5-(2-hydroxybenzoyl)-3-methyl-1-(2-pyridinyl)pyrazol-4-carboxylic acid methyl ester (2) or 3-methyl-1-(2-pyridinyl)-1H-chromene[4,3-c]pyrazol-4-on (3). The new copper(II) complexes have been characterized by elemental analysis and solid state FT-IR. The protonation constants of ligands 2 and 3 have been determined in 5% v/v 1,4-dioxane–water solution (25 °C). The coordination modes in the complexes with copper(II) are discussed for 2 on the basis of potentiometric and UV–Vis data. 相似文献
993.
In order to clarify the doping behavior of different alkali metals in perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), Fourier transform infrared spectra of PTCDA thin films doped with sodium, potassium, and cesium were measured and compared. Furthermore the vibrational properties were calculated using density-functional theory and these calculated vibrational frequencies were assigned to the experimental IR modes of the thin films. 相似文献
994.
P. Pawłowski B. Borderie G. Auger Ch.O. Bacri N. Bellaize F. Bocage R. Bougault R. Brou P. Buchet J.L. Charvet A. Chbihi J. Colin D. Cussol R. Dayras A. Demeyer D. Doré D. Durand J.D. Frankland E. Galichet E. Genouin-Duhamel E. Gerlic D. Guinet P. Lautesse J.L. Laville J.F. Lecolley R. Legrain N. Le Neindre O. Lopez M. Louvel A.M. Maskay L. Nalpas A.D. Nguyen M. Pârlog J. Péter E. Plagnol M.F. Rivet E. Rosato F. Saint-Laurent S. Salou J.C. Steckmeyer M. Stern G. Tăbăcaru B. Tamain L. Tassan-Got O. Tirel E. Vient C. Volant J.P. Wieleczko 《The European Physical Journal A - Hadrons and Nuclei》2000,9(3):371-383
The prompt component at intermediate velocity of light charged particles is investigated. An improved coalescence model coupled
to the intra-nuclear cascade code ISABEL is used to obtain light complex particle energy spectra and multiplicities as a function
of impact parameter. The results are compared with experimental data from the 36Ar + 58Ni experiment at 95 MeV/nucleon, performed with the INDRA 4π detection system. The calculated prompt component is found to
rather well reproduce proton spectra. For complex light charged particles the calculated components well populate the high
energy part of spectra. Prompt emission can therefore explain the large transverse energies experimentally observed at mid-rapidity.
Received: 27 July 2000 / Accepted: 20 November 2000 相似文献
995.
T. S. Argunova R. F. Vitman I. V. Grekhov L. S. Kostina T. V. Kudryavtseva M. Yu. Gutkin A. V. Shturbin J. Härtwig M. Ohler E. D. Kim S. Ch. Kim 《Physics of the Solid State》1999,41(11):1790-1798
The elastically strained state of the interface in directly-bonded silicon structures has been studied by x-ray diffraction topography and IR spectrometry. The pattern of the contrast observed in the x-ray topographs and the intensity oscillations in the IR spectra indicate a periodic strain distribution caused by the long-period surface microroughness on the plates to be bonded. The local microroughness did not exceed 2 Å, and it did not noticeably affect the interface structure. Two types of the structure were subjected to a comparative analysis, (i) with a smooth interface prepared by standard direct-bonding technology, and (ii) with an interface displaying a regular relief. The strain level in type-II structures was found to be lower by more than an order of magnitude. A model is proposed to account for the observed reduction of elastic strains at the bonded sections of the interface in terms of elastic relaxation of the free surfaces in the relief voids through their deflection and displacement. 相似文献
996.
G. Ch. Shushkevich 《Technical Physics》1999,44(2):133-136
The axisymmetric electrostatic problem of a thin, unclosed ellipsoidal shell and disk is solved. The capacitance coefficients
are calculated for a representative set of values of the geometrical parameters of the conductors.
Zh. Tekh. Fiz. 69, 1–5 (February 1999) 相似文献
997.
Cotton fabric is modified by means of polycarboxylic acids in combination with an inorganic or an organic catalyst in order
to impart durable press properties. After the curing process the cellulosic specimen is washed off to remove both the portion
of the polycarboxylic acid that has not reacted and the catalyst applied. The treated cellulosic fabric is saponified with
a sodium hydroxide solution to extract the PCA that has reacted with the cellulosic material. Both the wash liquor and the
saponification liquor are investigated by means of isocratic HPLC using Aminex HPX-87-H as stationary phase. Excellent separation
of the various polycarboxylic acids that are applied as crosslinking agents or as organic catalysts is achieved. The HPLC
method presented enables the identification and quantification of the polycarboxylic acids.
Received: 19 January 1999 / Revised: 24 March 1999 / Accepted: 28 March 1999 相似文献
998.
M. Waiblinger Ch. Sommerhalter B. Pietzak J. Krauser B. Mertesacker M.Ch. Lux-Steiner S. Klaumünzer A. Weidinger C. Ronning H. Hofsäß 《Applied Physics A: Materials Science & Processing》1999,69(2):239-240
Electrically conducting channels in an insulating carbon matrix were produced by 140-MeV Xe ion irradiation. The high local
energy deposition of the individual ions along their pathes causes a rearrangement of the carbon atoms and leads to a transformation
of the insulating, diamond-like (sp3-bonding) form of carbon into the conducting, graphitic (sp2-bonding) configuration. The conducting ion tracks are clearly seen in the current mapping performed with an atomic force
microscope (AFM). These conducting tracks are of possible use in field emission applications.
Received: 4 May 1999 / Accepted: 5 May 1999 / Published online: 1 July 1999 相似文献
999.
The title compounds were synthesized from the elements by reactions at high temperature. They crystallize with a hexagonal structure which was determined from single‐crystal X‐ray data of Dy12Ni30As21: P63/m, Z = 1, a = 1698.5(5) pm, c = 387.7(1) pm, R = 0.053 for 797 F values and 69 variable parameters. It belongs to a large family of hexagonal structures with a metal to metalloid ratio of 2 : 1. In these hexagonal structures an ordered distribution of occupied atomic positions around the hexagonal 63 axis is possible only for refinements in space groups of lower symmetry. This is discussed for the present case and the very closely related structures reported for (La, Ce)12Rh30P21 and Nd3Ni7P5. 相似文献
1000.
The Crystal Structure of Ga5Pd13 – a Low‐Symmetrical Ordering Variant of the Cubic Close Sphere Packing Ga5Pd13 is accessible from the elements in the presence of catalytically active amounts of iodine at 520 °C. The phase decomposes at 897 °C in a peritectoid reaction. The monoclinic crystal structure was determined from the intensities of an X‐ray powder diffractogram and refined by a Rietveld profile fit: C 2/m, Z = 2, a = 2425.99(5) pm, b = 405.060(7) pm, c = 544.37(1) pm, β = 102.690(1)°, Rp = 0.069. The new structure type is described as an ordering variant of the cubic close sphere packing. The ordering pattern and the distortions in the primary coordination of the atoms reflect the definite impact of the intermetallic bonding interactions on the differentiation of the structure. 相似文献