全文获取类型
收费全文 | 1585篇 |
免费 | 22篇 |
国内免费 | 58篇 |
专业分类
化学 | 896篇 |
晶体学 | 16篇 |
力学 | 25篇 |
数学 | 76篇 |
物理学 | 652篇 |
出版年
2024年 | 10篇 |
2023年 | 45篇 |
2022年 | 49篇 |
2021年 | 30篇 |
2020年 | 46篇 |
2019年 | 28篇 |
2018年 | 29篇 |
2017年 | 29篇 |
2016年 | 39篇 |
2015年 | 53篇 |
2014年 | 39篇 |
2013年 | 110篇 |
2012年 | 119篇 |
2011年 | 130篇 |
2010年 | 91篇 |
2009年 | 113篇 |
2008年 | 82篇 |
2007年 | 121篇 |
2006年 | 75篇 |
2005年 | 63篇 |
2004年 | 67篇 |
2003年 | 52篇 |
2002年 | 40篇 |
2001年 | 29篇 |
2000年 | 27篇 |
1999年 | 34篇 |
1998年 | 14篇 |
1997年 | 18篇 |
1996年 | 20篇 |
1995年 | 12篇 |
1994年 | 13篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1976年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有1665条查询结果,搜索用时 15 毫秒
1.
For more than 25 yearsJΨ production has helped to sharpen our understanding of QCD. In proton induced reaction some observations are rather well understood
while others are still unclear. The current status of the theory ofJΨ production will be sketched, paying special attention to the issues of formation time andJΨ re-interaction in a nuclear medium. 相似文献
2.
Djamel Meraghni Abdelhakim Necir 《Methodology and Computing in Applied Probability》2007,9(4):557-572
The characteristic exponent α of a Lévy-stable law S
α
(σ, β, μ) was thoroughly studied as the extreme value index of a heavy tailed distribution. For 1 < α < 2, Peng (Statist. Probab. Lett. 52: 255–264, 2001) has proposed, via the extreme value approach, an asymptotically normal estimator for the location parameter μ. In this paper, we derive by the same approach, an estimator for the scale parameter σ and we discuss its limiting behavior.
相似文献
3.
M.A. Domínguez-Crespo L. Díaz-García A.M. Torres-Huerta 《Applied Surface Science》2006,253(3):1205-1214
Four NiMo catalyst supported on Al2O3 with different textural properties have been studied in the hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrodearomatization (HDA) of a Mexican straight run gasoil (SRGO). All reactions were carried out at three different temperatures 613, 633, and 653 K. Alumina supports were analysed by pyridine FTIR-TPD and nitrogen physisorption in order to determine their surface acidity and textural properties, respectively. TPR studies of the NiMo catalysts were analysed to correlate their hydrogenating properties. Metallic particles were characterized (after sulfidation) using transmission electron microscopy (TEM). Catalytic activities are discussed in relation to the physicochemical properties of NiMo catalysts. The importance of textural properties on coke deposition has been emphasized. The results of catalytic activity of these materials varied depending on dispersed MoS particles and pore distribution in final catalysts. The optimum pore diameter was found around 80 Å for HDS and HDN. 相似文献
4.
合成了重稀土高氯酸盐甲基苯甲酰甲基亚砜配合物RE(ClO4)3·L5·C2H5OH(RE=Gd,Tb,Dy,Tm,Yb;L=C6H5COCH2SOCH3).经元素分析、稀土络合滴定、摩尔电导及热重分析确定了配合物的组成,测定了配体及配合物的IR谱、1H NMR及铽配合物的磷光光谱、荧光激发和发射光谱,根据荧光发射光谱数据计算了铽配合物的各能级值. 相似文献
5.
A current interpretation of XPS spectra of Ni metal assumes that the main 6 eV satellite is due to a two hole c3d94s2 (c is a core hole) final state effect. We report REELS observation in AES at low voltages of losses (plasmons and inter-band transitions) corresponding to the satellite structures in Ni metal 2p spectra. The satellite near 6 eV is attributed to a predominant surface plasmon loss. A current interpretation of Ni 2p spectra of oxides and other compounds is based on charge transfer assignments of the main peak at 854.6 eV and the broad satellite centred at around 861 eV to the cd9L and the unscreened cd8 final-state configurations, respectively (L is a ligand hole). Multiplet splittings have been shown to be necessary for assignment of Fe 2p and Cr 2p spectral profiles and chemical states. The assignments of Ni 2p states are re-examined with intra-atomic multiplet envelopes applied to Ni(OH)2, NiOOH and NiO spectra. It is shown that the free ion multiplet envelopes for Ni2+ and Ni3+ simulate the main line and satellite structures for Ni(OH)2 and NiOOH. Fitting the NiO Ni 2p spectral profile is not as straightforward as the hydroxide and oxyhydroxide. It may involve contributions from inter-atomic, non-local electronic coupling and screening effects with multiplet structures significantly different from the free ions as found for MnO. A scheme for fitting these spectra using multiplet envelopes is proposed. 相似文献
6.
Erik Woldt 《Journal of Physics and Chemistry of Solids》2002,63(4):699-704
The paper investigates whether a change from a homogeneous to an inhomogeneous dislocation distribution, assumed to be caused by a slight additional deformation, can lead to an increase of the recrystallization temperature of a deformed metal. In this case, the higher temperature would indicate a more stable deformation structure despite the increase of stored energy. The recrystallization temperature is related to the growth rate. Hence, the steady state velocity of a recrystallization front moving either parallel or vertically to the stripes of a simplified two-dimensional heterogeneous dislocation distribution of parallel sections of higher and lower dislocation densities is calculated. The results show that if a front growths through the high and low density sections in series an overall slower rate despite higher mean dislocation density is, indeed, possible. However, growing in the parallel arrangement always leads to a higher growth rate compared with the homogeneous case of slightly less stored energy. Since in a real structure the faster growth is likely to succeed, the recrystallization temperature observed will be lowered with additional deformation in accordance with experimental experience. 相似文献
7.
V.V. Glushkov S.V. Demishev M.I. Ignatov Yu.B. Paderno N.Yu. Shitsevalova O.A. Churkin N.E. Sluchanko 《Journal of solid state chemistry》2006,179(9):2871-2874
In order to reveal the nature of the ground state of archetypal intermediate-valence compound SmB6, a comprehensive study of its transport and magnetic properties was carried out on high-quality single crystals at temperatures of 1.8-300 K in magnetic fields up to 7 T. A drastic enhancement of negative magnetoresistance was observed below 14 K, with the maximum absolute value of Δρ/ρB2∼2.2×10−3 T−2 at T≈5.2 K. This effect seems to be attributable to anomalous magnetic scattering of many-body (exciton-polaronic) complexes induced by fast valence fluctuations on Sm sites. The observed anomalies of magnetotransport, thermoelectric and magnetic characteristics are discussed in terms of electron phase transition to the coherent state of interacting many-body complexes occurring at T*∼5 K. 相似文献
8.
A. Loidl A. Krimmel K. Knorr G. Sparn M. Lang C. Geibel S. Horn A. Grauel F. Steglich B. Welslau N. Grewe H. Nakotte F. R. de Boer A. P. Murani 《Annalen der Physik》1992,504(2):78-91
Elastic and inelastic neutron-scattering studies on the system Ce(Cu1?xNix)2Ge2 are reported. These measurements are complemented by measurements of the magnetic susceptibility, high-field magnetization, heat capacity, thermal expansion, electrical resistivity and thermopower. The results reveal an interesting T-x phase diagram consisting of two different antiferromagnetic phases for x < 0.2 and 0.2 < x < 0.75, respectively, and a heavy-Fermi-liquid regime at higher Ni concentrations. The experimental results are interpreted in terms of an alloying-induced transition from local-moment to itinerant heavy-fermion magnetism. Fingerprints of this latter phase are a strongly reduced ordered moment and a short incommensurate ordering wave vector, in accord with theoretical predictions. A surprisingly good agreement between theory and experiment is found for x > 0.5. Further experimental evidence for different types of antiferromagnetic ordering derives from a line-shape analysis of the quasielastic neutron-scattering intensity, from magnetization and thermopower experiments. 相似文献
9.
The role of filamentation instability of quark-gluon plasma, in explaining collective phenomena in relativistic heavy-ion
collisions, has been analyzed. Using equations of SU(2) two fluid color hydrodynamics it is shown that this instability can
significantly enhance nuclear stopping and might contribute to collective sideward flows. 相似文献
10.
The thermoluminescence (TL) and optically stimulated luminescence (OSL) response of Al2O3 dosimeters to high-energy heavy charged particles (HCP) has been studied using the heavy ion medical accelarator at Chiba, Japan. The samples were Al2O3 single-crystal chips, of the type usually known as TLD-500, and LuxelTM dosimeters (Al2O3:C powder in plastic) from Landauer Inc. The samples were exposed to 4He (150 MeV/u), 12C (400 MeV/u), 28Si (490 MeV/u) and 56Fe (500 MeV/u) ions, with linear energy transfer values covering the range from 2.26 to 189 keV/μm in water and doses from 1 to 100 mGy (to water). A 90Sr/90Y beta source, calibrated against a 60Co secondary standard, was used for calibration purposes. For OSL, we used both continuous-wave OSL measurements (CW-OSL, using green light stimulation at 525 nm) and pulsed OSL measurements (POSL, using 532 nm stimulation from a Nd:YAG Q-switched laser). The efficiencies (ηHCP,γ) of the different HCPs at producing OSL or TL were observed to depend not only upon the linear energy transfer (LET) of the HCP, but also upon the sample type (single crystal chip or LuxelTM) and the luminescence method used to define the signal—i.e. TL, CW-OSL initial intensity, CW-OSL total area, or POSL. Observed changes in shape of the decay curve lead to potential methods for extracting LET information of unknown radiation fields. A discussion of the results is given, including the potential use of OSL from Al2O3 in the areas of space radiation dosimetry and radiation oncology. 相似文献