全文获取类型
收费全文 | 893篇 |
免费 | 13篇 |
国内免费 | 1篇 |
专业分类
化学 | 435篇 |
晶体学 | 21篇 |
力学 | 24篇 |
数学 | 60篇 |
物理学 | 367篇 |
出版年
2024年 | 7篇 |
2022年 | 12篇 |
2021年 | 14篇 |
2020年 | 7篇 |
2019年 | 21篇 |
2018年 | 23篇 |
2017年 | 22篇 |
2016年 | 19篇 |
2015年 | 15篇 |
2014年 | 29篇 |
2013年 | 74篇 |
2012年 | 52篇 |
2011年 | 61篇 |
2010年 | 46篇 |
2009年 | 39篇 |
2008年 | 48篇 |
2007年 | 40篇 |
2006年 | 31篇 |
2005年 | 36篇 |
2004年 | 21篇 |
2003年 | 22篇 |
2002年 | 20篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1995年 | 5篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 11篇 |
1977年 | 10篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 10篇 |
1973年 | 12篇 |
1971年 | 5篇 |
1959年 | 5篇 |
排序方式: 共有907条查询结果,搜索用时 15 毫秒
61.
In this paper the general non-static axially symmetric line element has been considered in the context of Petrov Classification.
The space-time is found to be of various Petrov Types under different circumstances. The necessary algebraic conditions for
such a space-time to be of class one have also been derived. It is found that there exists only one solution representing
a plane symmetric class-one null-electromagnetic field. 相似文献
62.
The energy transfer phenomenon has been studied from Tb3+ → Nd3+ and Tb3+ → Ho3+ in DMSO. A diffusion limited dipole-dipole mechanism of energy transfer is suggested for both systems. At high acceptor concentrations, Pda depends linearly on C2 consistent with the Fong and Diestler theory of energy transfer. However, at low acceptor concentrations the observations of time evolutions of Tb3+ luminescence decay following flash excitation has enabled us to examine diffusion limited energy transfer from Tb3+ to Nd3+ and Tb3+ to Ho3+ in DMSO. 相似文献
63.
The G-protein-coupled receptor (GPCR) superfamily represents one of the largest classes of molecules involved in signal transduction
across the plasma membrane. Fluorescence-based approaches have provided valuable insights into GPCR functions such as receptor–receptor
and receptor–ligand interactions, real-time assessment of signal transduction, receptor dynamics on the plasma membrane, and
intracellular trafficking of receptors. This has largely been possible with the use of fluorescent probes such as the green
fluorescent protein (GFP) from the jellyfish Aequoria victoria and its variants. We discuss the potential of fluorescence-based approaches in providing novel information on the membrane
organization and dynamics of the G-protein-coupled serotonin1A receptor tagged to the enhanced yellow fluorescent protein (EYFP).
These authors contributed equally to the work. 相似文献
64.
Wiedeking M Tabor SL Pavan J Volya A Aguilar AL Calderin IJ Campbell DB Cluff WT Diffenderfer E Fridmann J Hoffman CR Kemper KW Lee S Riley MA Roeder BT Teal C Tripathi V Wiedenhöver I 《Physical review letters》2005,94(13):132501
Excited states in 20O were populated in the reaction 10Be(14C,alpha) at Florida State University (FSU). Charged particles were detected with a particle telescope consisting of 4 annularly segmented Si surface barrier detectors and gamma radiation was detected with the FSU gamma detector array. Five new states were observed below 6 MeV from the alpha-gamma and alpha-gamma-gamma coincidence data. Shell model calculations suggest that most of the newly observed states are core-excited 1p-1h excitations across the N=Z=8 shell gap. Comparisons between experimental data and calculations for the neutron-rich O and F isotopes imply a steady reduction of the p-sd shell gap as neutrons are added. 相似文献
65.
We propose and demonstrate a simple technique for determining the M/# parameter of a holographic recording material. In this method, divergent object and reference beams are used to produce a spatially varying index modulation. One can analyze the resultant diffraction pattern to find M/# by using only a single grating; existing techniques require many gratings. 相似文献
66.
Shahriar MS Tripathi R Kleinschmit M Donoghue J Weathers W Huq M Shen JT 《Optics letters》2003,28(7):525-527
We describe a superparallel holographic optical correlator that performs two-dimensional spatial and angular multiplexing simultaneously. The key step in this architecture is the use of a holographic multiplexer to split a query image into many copies before it applies them to the holographic database. A holographic demultiplexer, in conjunction with an aperture, is used to identify the location and the angle of the brightest correlation peak. This architecture uses only O(square root of N) detector elements to search through N unsorted images in a single query. We demonstrate the basic features of this architecture, using three spatial locations with eight angle-multiplexed images in each location. 相似文献
67.
Alavi-Harati A Alexopoulos T Arenton M Arisaka K Barbosa RF Barker AR Barrio M Bellantoni L Bellavance A Blucher E Bock GJ Bown C Bright S Cheu E Coleman R Corcoran MD Cox B Erwin AR Escobar CO Ford R Glazov A Golossanov A Gouffon P Graham J Hamm J Hanagaki K Hsiung YB Huang H Jejer V Jensen DA Kessler R Kobrak HG Kotera K LaDue J Lai N Ledovskoy A McBride PL Monnier E Nelson KS Nguyen H Prasad V Qi XR Quinn B Ramberg EJ Ray RE Santos E Senyo K Shanahan P Shields J Slater W Solomey N Swallow EC 《Physical review letters》2003,90(14):141801
The KTeV experiment at Fermilab has isolated a total of 132 events from the rare decay K(L)-->e+ e- mu+ mu-, with an estimated background of 0.8 events. The branching ratio of this mode is determined to be [2.69+/-0.24(stat)+/-0.12(syst)]x10(-9), with a radiative cutoff of M(2)(ee mu mu)/M(2)(K)>0.95. The first measurement using this mode of the parameter alpha from the D'Ambrosio-Isidori-Portolès (DIP) model of the K(L)gamma*gamma* vertex yields a result of -1.59+/-0.37, consistent with values obtained from other decay modes. Because of the limited statistics, no sensitivity is found to the DIP parameter beta. We use this decay mode to set limits on CP and lepton violation. 相似文献
68.
M. K. Pandey R. K. Dubey D. N. Tripathi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):275-279
The Classical Trajectory Monte Carlo (CTMC) Method has
been used to calculate the differential, partial and total single electron
capture cross sections for the collision of H+/D+ with Ca and Mg
atoms in the energy range of 1–100 keV. The differential cross sections
at angles near the diffraction limit (<0.1○) in both systems
show a forward peak followed by an asymptotic fall at higher angles. Total
and partial capture cross sections are found to be in good agreement with
the experimental observations. Oscillations in the partial capture cross sections have been explained due to the swapping
of the field electron.
Isotope effect in the electron transfer is reported to be negligible. 相似文献
69.
We demonstrate theoretically as well as experimentally that a four-layer polymeric waveguide structure can be used to produce a mode and a polarization filter. Various optical properties such as refractive index, birefringence and propagation constant of polycarbonate, polystyrene and a commercially available photoresist (from Shipley) are presented. The thin film structures consisting of glass/polycarbonate/polystyrene/air are used for demonstrating polarization filter action and glass/photoresist/polystyrene/air structure for mode filter. Expressions for the electric field intensity spatial distribution for the structure are used to calculate the intensity profiles to support the observed behavior. The experimental values were in good agreement with the one obtained theoretically. 相似文献
70.
Photoluminescence (PL) properties of swift heavy ions-induced F2 and F3+ color centers in nano-granular lithium fluoride (LiF) thin film were studied. LiF films were deposited on glass and silica substrates and irradiated with various ion species (Ag, Ni and Au) at different irradiation temperatures. The role of ion species, their fluence and the irradiation temperature on the PL intensity of color centers induced in LiF thin films is discussed. 相似文献