全文获取类型
收费全文 | 8131篇 |
免费 | 284篇 |
国内免费 | 5篇 |
专业分类
化学 | 4797篇 |
晶体学 | 165篇 |
力学 | 175篇 |
数学 | 1635篇 |
物理学 | 1648篇 |
出版年
2023年 | 41篇 |
2022年 | 48篇 |
2021年 | 65篇 |
2020年 | 123篇 |
2019年 | 175篇 |
2018年 | 201篇 |
2017年 | 233篇 |
2016年 | 429篇 |
2015年 | 315篇 |
2014年 | 384篇 |
2013年 | 717篇 |
2012年 | 456篇 |
2011年 | 511篇 |
2010年 | 350篇 |
2009年 | 291篇 |
2008年 | 504篇 |
2007年 | 442篇 |
2006年 | 384篇 |
2005年 | 303篇 |
2004年 | 254篇 |
2003年 | 193篇 |
2002年 | 153篇 |
2001年 | 113篇 |
2000年 | 111篇 |
1999年 | 65篇 |
1998年 | 77篇 |
1997年 | 51篇 |
1996年 | 65篇 |
1995年 | 57篇 |
1994年 | 45篇 |
1993年 | 36篇 |
1992年 | 41篇 |
1991年 | 64篇 |
1990年 | 52篇 |
1989年 | 61篇 |
1988年 | 57篇 |
1987年 | 53篇 |
1986年 | 52篇 |
1985年 | 101篇 |
1984年 | 104篇 |
1983年 | 69篇 |
1982年 | 62篇 |
1981年 | 70篇 |
1980年 | 67篇 |
1979年 | 52篇 |
1978年 | 41篇 |
1977年 | 33篇 |
1976年 | 43篇 |
1975年 | 36篇 |
1974年 | 32篇 |
排序方式: 共有8420条查询结果,搜索用时 656 毫秒
961.
Aequationes mathematicae - For a family $$(\mathscr {A}_x)_{x \in (0,1)}$$ of integral quasi-arithmetic means satisfying certain measurability-type assumptions we search for an integral mean K such... 相似文献
962.
Anna Chachaj-Brekiesz Krzysztof Zborowski Joanna Zemła Katarzyna Makyła-Juzak 《Molecular physics》2013,111(24):3567-3577
Symmetrical triblock semifluorinated n-alkane, di(perfluorohexyl)hexane of the formula F(CF2)6(CH2)6(CF2)6F (abbreviated F6H6F6), has been synthesised and investigated at the air/water interface. Our results show for the first time that this unusual film-forming material, completely hydrophobic in nature and possessing no polar group, is capable of stable film formation at the free water surface. The surface pressure–area isotherm of the studied compound exhibited two regions: corresponding to monotonous pressure rise, followed by a pseudo-plateau region. Visualisation of film structure with Brewster angle microscope (BAM) proved the formation of domains within the pseudo-plateau region. A closer insight into the structure of these domains with atomic force microscope (AFM) proved their ordered, circular shape. The average area of F6H6F6 domain was found to depend on surface pressure value, as it is 4.98 ± 1.75 μm2 at π = 1.2 mN/m to 16.54 ± 0.31 μm2 at π = 1.7 mN/m. Following performed quantum-chemical calculations, it can be concluded that the observed surface aggregates from F6H6F6 are formed by linear conformers with shifted CF and CH parts. The calculated domain thickness is between 20 and 21 Å, which perfectly agrees with the experimental value estimated from AFM measurements (20.3 ± 1.4 Å). 相似文献
963.
We report on studies of changes in the emission spectra (excited at 808 nm) of the Yb-doped Ca4NdO(BO3)3 single crystals due to the photothermal effects caused by the pulsed Nd:YAG laser. Increase of the sample's surface temperature after laser treatment leads to significant enhancement of the 1040 to 1060 nm emission (ascribed to the Nd3+ 4F3/2 → 4I9/2, 4I11/2 transitions) and simultaneous decrease of the 975 to 1050 nm emission (corresponding to the Yb3+ 2F5/2 → 2F7/2 transition). We explain such an increase of the Nd3+ luminescence by thermally activated Yb3+ → Nd3+ energy transfer. 相似文献
964.
J. Równicka-Zubik A. Sułkowska M. Maciążek-Jurczyk L. Sułkowski W. W. Sułkowski 《光谱学快报》2013,46(7):520-529
Sulindac (SDC) is a nonsteroidal anti-inflammatory drug, useful in the treatment of chronic and acute inflammatory conditions. The binding of SDC to human serum albumin and bovine serum albumin was studied by fluorescence spectroscopy and the results compared with those obtained for human and bovine serum albumin destabilized with urea and guanidine hydrochloride. SDC interacts with serum albumin within the hydrophobic subdomain IIA and/or IB. The analysis of the binding constants shows that the studied albumins preserve their binding capacity in the presence of destabilizing/denaturating agents. The denaturation coefficient has been calculated to estimate the degree of denaturation of protein. 相似文献
965.
Abstract α,ω-Tertiary diamines react under high pressure with α,ω-di-iodo compounds to give cyclic or bicyclic bis-quaternary salts in almost quantitative yields. The role of high-pressure-induced changes in conformation of linear intermediates and the viscosity factor are discussed. 相似文献
966.
Wojciech Paszkowicz Scott M. Woodley Paweł Piszora Bohdan Bojanowski Jarosław Piętosa Yngve Cerenius Stefan Carlson Christine Martin 《Applied Physics A: Materials Science & Processing》2013,112(4):839-845
Elastic properties of CaMnO3 are of primary importance in the science and technology of CaMnO3-based perovskites. From X-ray diffraction experiments performed at pressures up to 100 kbar using a diamond-anvil cell to hydrostatically compress our sample, a bulk modulus, K 0, of 1734(96) kbar was obtained after fitting parameters to the third-order Birch–Murnaghan equation of state. Mean field, semiclassical simulations predict, for the first time, the third-order equation-of-state parameters and show how the bulk modulus increases with pressure (the zero pressure value being 2062.1 kbar) and decreases with the extent of nonstoichiometry caused by the formation of oxygen vacancies. These trends are amplified for the shear modulus. A more accurate model that allows for the explicit reduction of Mn ions, or localization of excess electrons, yields qualitatively similar results. The experimental and calculated axial ratios show the same trends in their variation with rising pressure. 相似文献
967.
The anode supported cell for solid oxide fuel cell, as a modification of the traditional Ni-YSZ anode supported on electrolyte, is examined in this work. The materials obtained on the base of citric method are presented and investigated in this work. The materials consisted of 40 wt.% Ni/YSZ, 50 wt.% Ni/YSZ and 60 wt.% Ni/YSZ were obtained. The base Ni/YSZ materials are tested on the two ways: (a) aging tests and (b) sintering tests. All the materials after aging and sintering are tested by the impedance spectroscopy. The results of electrical conductivity for samples before and after aging show that only in the case of 40 wt.% Ni/YSZ, sample loses of metallic conductivity after 500 h of heating. The other samples reveal metallic conductivity even after long period of aging. The tests of sintering temperature show that this process does not affect significantly on electrical conductivity of the materials. 相似文献
968.
Małgorzata Norek Grzegorz Łuka Marek Godlewski Tomasz Płociński Marta Michalska-Domańska Wojciech J. Stępniowski 《Applied Physics A: Materials Science & Processing》2013,111(1):265-271
Luminescent properties of ZnO nanorods covered with Ag nanoparticles are examined. Nanorods were synthesized on AAO templates using Atomic Layer Deposition (ALD) technique. Two types of the samples were prepared with different arrangement of ZnO nanorods and doping conditions. Nanorods of the second type were codoped with Al, to stimulate defect-related emissions. The ZnO material fills heterogeneously the interior of the AAO nanopores and has hexagonal, wurtzite structure. Both types of structures exhibit a broad defect-related emission at about 440 nm, most probably related to recombination at zinc interstitial (Zni) defects. This emission in samples with a random distribution of ZnO:Al nanorods and finer Ag nanoparticles is enhanced by factor of ~2.5 upon Ag deposition. The so-obtained material is interesting from the point of view of its application in blue range emitting diodes. 相似文献
969.
Summary Analytic equations of the multiconfigurational SCF (MCSCF) response theory are combined with the finite-field (FF) approach to compute static and frequency dependent electric and magnetic properties of the Argon atom. A complete active space (CAS SCF) function including the 3s, 3p, 3d, 4s and 4p orbitals in the active space and a large (17s 13p 7d 5f 3g) basis set are employed. This permits an accurate determination of various linear and non-linear response properties such as e.g. electric dipole polarisability and second hyperpolarisability, Verdet constant, magnetisability and second hyperpolarisability. The results, both for the static values and for the frequency dependence of these properties, compare well with other most recent experimental and theoretical data.Dedicated to Jan Linderberg on the occasion of his 60th birthday 相似文献
970.
We show that it is consistent with MA + ?CH that the Forcing Axiom fails for all forcing notions in the class of ωω–bounding forcing notions with norms of [17].
Received: 28 April 1999 / Published online: 12 December 2001 相似文献