全文获取类型
收费全文 | 23049篇 |
免费 | 2208篇 |
国内免费 | 1271篇 |
专业分类
化学 | 6994篇 |
晶体学 | 186篇 |
力学 | 7591篇 |
综合类 | 252篇 |
数学 | 4893篇 |
物理学 | 6612篇 |
出版年
2024年 | 25篇 |
2023年 | 256篇 |
2022年 | 378篇 |
2021年 | 495篇 |
2020年 | 602篇 |
2019年 | 494篇 |
2018年 | 512篇 |
2017年 | 640篇 |
2016年 | 770篇 |
2015年 | 730篇 |
2014年 | 990篇 |
2013年 | 1663篇 |
2012年 | 1192篇 |
2011年 | 1465篇 |
2010年 | 1122篇 |
2009年 | 1457篇 |
2008年 | 1368篇 |
2007年 | 1375篇 |
2006年 | 1233篇 |
2005年 | 1076篇 |
2004年 | 1019篇 |
2003年 | 894篇 |
2002年 | 765篇 |
2001年 | 619篇 |
2000年 | 610篇 |
1999年 | 546篇 |
1998年 | 517篇 |
1997年 | 485篇 |
1996年 | 455篇 |
1995年 | 414篇 |
1994年 | 325篇 |
1993年 | 298篇 |
1992年 | 284篇 |
1991年 | 230篇 |
1990年 | 204篇 |
1989年 | 164篇 |
1988年 | 155篇 |
1987年 | 100篇 |
1986年 | 95篇 |
1985年 | 118篇 |
1984年 | 102篇 |
1983年 | 47篇 |
1982年 | 97篇 |
1981年 | 41篇 |
1980年 | 18篇 |
1979年 | 17篇 |
1978年 | 13篇 |
1976年 | 11篇 |
1971年 | 7篇 |
1957年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Summary The combination affinity chromatography-mass spectrometry can be drastically improved by introducing a reversed phase column
prior to the mass spectrometric detection. The interactions of the macrocyclic antibiotic vancomycin with oligopeptides were
used to illustrate the performance of the technique. A library of 36 peptides was successfully screened and the active compounds
identified by electrospray MS(n). The strong affinity of compounds ending with (D)-alanine and with (D)-alanine or an aromatic (D)-amino acid in the penultimate
position with vancomycin was confirmed. 相似文献
992.
V. Lepiller A. Goharzadeh A. Prigent I. Mutabazi 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(4):445-455
We have investigated the influence of a weak radial
temperature gradient in a wide gap and large aspect ratio
Couette-Taylor system. The inner cylinder is rotating and can be
heated or cooled, the outer cylinder is at rest and immersed in a
large thermal bath. We found that a radial temperature gradient
destabilizes the Couette flow leading to a pattern of traveling
helicoidal vortices occurring only near the bottom of the system.
The size of the pattern increases as the rotation frequency of the cylinder is increased. We
have characterized the spatiotemporal properties of the pattern and we have shown that it
behaves as a wall mode found in the simulation of the
complex Ginzburg-Landau equation with homogeneous boundary
conditions. 相似文献
993.
S. E. Mangioni H. S. Wio 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(1):67-73
We analyze the effect of a colored non Gaussian noise on a model of
a random walker moving along a ratchet potential. Such a model was
motivated by the transport properties of motor proteins, like
kinesin and myosin. Previous studies have been realized assuming
white noises. However, for real situations, in general we could
expect that those noises be correlated and non Gaussian. Among other
aspects, in addition to a maximum in the current as the noise
intensity is varied, we have also found another optimal value of the
current when departing from Gaussian behavior. We show the relevant
effects that arise when departing from Gaussian behavior,
particularly related to current's enhancement, and discuss its
relevance for both biological and technological situations. 相似文献
994.
Yu. Ya. Trifonov 《Journal of Engineering Thermophysics》2008,17(1):30-52
This paper is devoted to a theoretical analysis of nonlinear two-dimensional waves using the Navier-Stokes equations in their
full statement. Steady-state travelling wave regimes have been found and an analysis of their linear stability has been carried
out. It is shown that the flow regimes obtained using the Navier-Stokes equations are qualitatively different from the solutions
of Shkadov’s integral approach starting from some values of the Kapitza number. It is also found that the wave regimes of
the Navier-Stokes equations have an internal vortex at moderate Reynolds numbers. The results obtained using “the regularized
integral model” are in excellent agreement with the Navier-Stokes calculations for Re/Ka ≤2. Unlike the solutions found using an integral approach, it is shown that only a few types of nonlinear waves exist when
the full Navier-Stokes equations are considered.
The text was submitted by the author in English. 相似文献
995.
The optical torque and the trapping position (focal point) in optical tweezers are analyzed for upward-directed focused laser
illumination using a ray optics model, considering that laser light is incident at not only the lower surface but also the
side surface of a 3-wing rotor. The viscous drag force due to the pressure and the shearing stress on all surfaces of the
rotor is evaluated using computational fluid dynamics. The rotation rate is simulated in water by balancing the optical torque
with the drag force, resulting in 500 rpm for an SU-8 rotor with 20 μm diameter at a laser power of 200 mW. The trapping position
is estimated to be 7.6 μm in the rotor with an upward-directed laser at 200 mW via an objective lens having a numerical aperture
of 1.4. Both the rotation rate and the trapping position agree well with the values obtained in the experiment. 相似文献
996.
Josephson oscillation of a superfluid Fermi gas 总被引:1,自引:0,他引:1
S. K. Adhikari 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):413-419
Using the complete numerical solution of a time-dependent
three-dimensional mean-field model we
study the Josephson oscillation of a superfluid Fermi gas (SFG) at zero temperature formed in a combined axially-symmetric
harmonic plus one-dimensional periodic optical-lattice (OL) potentials after displacing the harmonic trap along the axial
OL
axis. We study the dependence of Josephson frequency on the strength of the OL potential. The Josephson frequency decreases
with increasing strength as found in the experiment of Cataliotti et al. [Science 293, 843 (2001)] for a Bose-Einstein condensate and of the experiment of Pezzè et al. [Phys. Rev. Lett. 93, 120401 (2004)] for an ideal Fermi gas. We demonstrate a
breakdown of Josephson oscillation in the SFG for a large displacement
of the harmonic trap. These features of Josephson oscillation of a SFG can be tested experimentally. 相似文献
997.
998.
M. Mukherjee D. Beck K. Blaum G. Bollen J. Dilling S. George F. Herfurth A. Herlert A. Kellerbauer H. -J. Kluge S. Schwarz L. Schweikhard C. Yazidjian 《The European Physical Journal A - Hadrons and Nuclei》2008,35(1):1-29
ISOLTRAP is a Penning trap mass spectrometer for high-precision mass measurements on short-lived nuclides installed at the
on-line isotope separator ISOLDE at CERN. The masses of close to 300 radionuclides have been determined up to now. The applicability
of Penning trap mass spectrometry to mass measurements of exotic nuclei has been extended considerably at ISOLTRAP by improving
and developing this double Penning trap mass spectrometer over the past two decades. The accurate determination of nuclear
binding energies far from stability includes nuclei that are produced at rates less than 100 ions/s and with half-lives well
below 100ms. The mass-resolving power reaches 107 corresponding to 10keV for medium heavy nuclei and the uncertainty of the resulting mass values has been pushed down to below
10-8. The article describes technical developments achieved since 1996 and the present performance of ISOLTRAP. 相似文献
999.
A. B. Bhattacherjee 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):499-506
We study the effect of a one dimensional optical superlattice on the superfluid properties (superfluid fraction, number squeezing,
dynamic structure factor) and the quasi-momentum distribution of the Mott-insulator. We show that due to the secondary lattice,
there is a decrease in the superfluid fraction and the number fluctuation. The dynamic structure factor which can be measured
by Bragg spectroscopy is also suppressed due to the addition of the secondary lattice. The visibility of the interference
pattern (the quasi-momentum distribution) of the Mott-insulator is found to decrease due to the presence of the secondary
lattice. Our results have important implications in atom interferometry and quantum computation in optical lattices. 相似文献
1000.
Cellular Automaton (CA) based traffic flow models have been extensively studied due to their effectiveness and simplicity in recent years. This paper develops a discrete time Markov chain (DTMC) analytical framework for a Nagel-Schreckenberg and Fukui Ishibashi combined CA model (W^2H traffic flow model) from microscopic point of view to capture the macroscopic steady state speed distributions. The inter-vehicle spacing Maxkov chain and the steady state speed Markov chain are proved to be irreducible and ergodic. The theoretical speed probability distributions depending on the traffic density and stochastic delay probability are in good accordance with numerical simulations. The derived fundamental diagram of the average speed from theoretical speed distributions is equivalent to the results in the previous work. 相似文献