全文获取类型
收费全文 | 1170篇 |
免费 | 28篇 |
专业分类
化学 | 566篇 |
晶体学 | 16篇 |
力学 | 23篇 |
数学 | 190篇 |
物理学 | 403篇 |
出版年
2021年 | 8篇 |
2020年 | 16篇 |
2019年 | 16篇 |
2018年 | 12篇 |
2017年 | 9篇 |
2016年 | 52篇 |
2015年 | 46篇 |
2014年 | 51篇 |
2013年 | 119篇 |
2012年 | 38篇 |
2011年 | 19篇 |
2010年 | 28篇 |
2009年 | 29篇 |
2008年 | 29篇 |
2007年 | 23篇 |
2006年 | 35篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 33篇 |
2001年 | 20篇 |
2000年 | 20篇 |
1999年 | 19篇 |
1998年 | 23篇 |
1997年 | 18篇 |
1996年 | 18篇 |
1995年 | 19篇 |
1994年 | 17篇 |
1993年 | 15篇 |
1992年 | 25篇 |
1991年 | 16篇 |
1990年 | 16篇 |
1989年 | 11篇 |
1988年 | 11篇 |
1987年 | 13篇 |
1986年 | 14篇 |
1985年 | 17篇 |
1984年 | 20篇 |
1982年 | 15篇 |
1981年 | 18篇 |
1980年 | 17篇 |
1979年 | 18篇 |
1978年 | 19篇 |
1977年 | 13篇 |
1976年 | 18篇 |
1975年 | 20篇 |
1974年 | 21篇 |
1973年 | 9篇 |
1972年 | 9篇 |
1971年 | 8篇 |
1969年 | 18篇 |
排序方式: 共有1198条查询结果,搜索用时 0 毫秒
81.
82.
Formation of the plasma potential in a plasma that contains energetic electrons and is bounded by a floating collector that
emits electrons is studied theoretically. The problem is treated by a static. kinetic plasma-sheath model of Schwager and
Birdsall [Phys. Fluids B2 (1990) 1057], which we have extended in order to include additional energetic electron population. The distribution of these
electrons is assumed to be a high-temperature Maxwellian. They are called hot electrons. In the paper we study effects of
the density and temperature of the hot electrons on the formation of the plasma potential. The model shows that for certain
densities and temperatures of the hot electron population plasmas with two different plasma potentials can coexist in the
system. These two plasmas are separated spatially by a double layer. For the case when there is no emission of electrons from
the collector, results of the model are compared with computer simulation and very good agreement between the model and the
simulation is found. The simulation also confirms existence of two plasmas with two different potentials separated by a double
layer. 相似文献
83.
Considering the Markov binomial distribution, we study large deviations for the Poisson approximation. Apart from the standard choice of parameters, we use the approach where the parameter of approximation depends on the argument of the approximated distribution function. 相似文献
84.
It is well known that in the non-depleted pump approximation, the efficiency of a second harmonic generation (SHG) of a guided mode in a non-linear optical waveguide increases quadratically with the interaction length (P
2 L
2), and linearly (P
2 L) in the erenkov regime. The efficiency of the erenkov SHG in the waveguide with a non-linear substrate and linear guiding layer is known to be strongly peaked at a particular pump wavelength and a particular waveguide thickness, with the erenkov angle approaching zero. The known theory predicts an infinite efficiency value at the peak, however. In this contribution, a simple integral expression for the SHG efficiency in the erenkov regime is derived. For large erenkov angles and interaction lengths it yields the expected P
2 L dependence, while in the limit of small erenkov angles the dependence is found to have the form of P L
3/2, possessing also a finite value at the efficiency peak. The condition determining the accurate position of the efficiency peak in the waveguide thickness–pump wavelength plane is given, too. 相似文献
85.
Alexander Čeklovský Juraj Bujdák Adriana Czímerová Nobuo Iyi 《Central European Journal of Physics》2007,5(2):236-243
Tetracationic porphyrin dyes TMPyP and ZnPyP were intercalated into hydrophobized layered silicate films of three smectites.
The smectites represented the layered silicate specimens of high (Fluorohectorite, Corning; FHT), medium (Kunipia F montmorillonite;
KF) and low layer charge (Laponite, Laporte; LAP). The molecular orientations of the dye cations were studied by means of
linearly-polarized ultraviolet-visible (UV-VIS) spectroscopy. The spectral analysis and consequent calculations of tilting
angles of the transition moments at the wavelengths of Soret band transitions were in the range of 25°-35°. The determined
angles indicated molecular orientation of the dye cations being almost parallel to the surface of the silicates. Slightly
higher values (above 35°), determined for a FHT film, indicated either a slightly tilted orientation of the dye cations or
the change of molecular comformation after the intercalation of the dye.
Presented at 5-th International Conference Solid State Surfaces and Interfaces, November 19–24, 2006, Smolenice Castle, Slovakia 相似文献
86.
Laila Čakare Marija Kosec Barbara Malič 《Journal of Sol-Gel Science and Technology》2000,19(1-3):603-606
PbZrO3 (PZ) thin films have been prepared by 2-methoxyethanol route from lead oxide or lead acetate and zirconium n-butoxide. The use of lead oxide as lead source and the seeding layer of TiO2 on Pt/TiO2/SiO2/Si substrate facilitate the formation of the perovskite phase. 相似文献
87.
Adsorption isotherms of carbon dioxide were measured on cation-exchanged (Li+, Na+, K+, Cs+) MCM-22 zeolite with the molar ratio of Si/Al=15 and series of Na-MCM-22 of Si/Al molar ratios varying in the range from
15 to 40 at 273, 293, 313 and 333 K. Based on the known temperature dependence of CO2 adsorption, isosteric heats of adsorption were calculated. The obtained dependences of isosteric heats related to the amount
of CO2 adsorbed have provided detailed insight into the interaction of carbon dioxide molecule with alkali metal cations. 相似文献
88.
Enquist H Navirian H Nüske R von Korff Schmising C Jurgilaitis A Herzog M Bargheer M Sondhauss P Larsson J 《Optics letters》2010,35(19):3219-3221
We have developed and characterized a hard x-ray accumulating streak camera that achieves subpicosecond time resolution by using single-photon counting. A high repetition rate of 2 kHz was achieved by use of a readout camera with built-in image processing capabilities. The effects of sweep jitter were removed by using a UV timing reference. The use of single-photon counting allows the camera to reach a high quantum efficiency by not limiting the divergence of the photoelectrons. 相似文献
89.
Pimková K Bocková M Hegnerová K Suttnar J Cermák J Homola J Dyr JE 《Analytical and bioanalytical chemistry》2012,402(1):381-387
The surface plasmon resonance (SPR) biosensor system with dispersionless microfluidics for the direct and label-free detection
of a soluble vascular endothelial growth factor receptor (sVEGFR-1) is described. The detection approach takes advantage of
an affinity interaction between sVEGFR-1 and its ligand, vascular endothelial growth factor (VEGF-A), which is covalently
immobilized on the surface of the SPR sensor. The ability of the immobilized VEGF-A to specifically bind the sVEGFR-1 receptor
is demonstrated in a buffer. The detection of sVEGFR-1 in 2% human blood plasma is carried out by using the sequential injection
approach. The detection limit of 25 ng/mL is achieved. In addition, we demonstrate that the functional surface of the sensor
can be regenerated for repeated use. 相似文献
90.
Determination of Sulfide by Hematoxylin Multiwalled Carbon Nanotubes Modified Carbon Paste Electrode
This study investigates a new approach for the amperometric determination of sulfide using a hematoxylin multiwalled carbon nanotubes modified carbon paste electrode (HM‐MWCNTs/CPE). The experimental results show that HM‐MWCNTs/CPE significantly enhances the electrocatalytic activity towards sulfide oxidation. Cyclic voltammetric studies show that the peak potential of sulfide shifted from +400 mV at unmodified CPE to +175 mV at HM‐MWCNTs/CPE. The currents obtained from amperometric measurements at optimum conditions were linearly correlated with the concentration of sulfide. The calibration curve was obtained for sulfide concentrations in the range of 0.5–150×10?6 mol L?1. The detection limit was found to be 0.2×10?6 mol L?1 for the amperometric method. The proposed method was successfully applied to a river water sample in Pardubice, Czech Republic. 相似文献