全文获取类型
收费全文 | 15794篇 |
免费 | 241篇 |
国内免费 | 67篇 |
专业分类
化学 | 5759篇 |
晶体学 | 358篇 |
力学 | 985篇 |
综合类 | 3篇 |
数学 | 1439篇 |
物理学 | 7558篇 |
出版年
2023年 | 61篇 |
2022年 | 178篇 |
2021年 | 149篇 |
2020年 | 86篇 |
2019年 | 102篇 |
2018年 | 197篇 |
2017年 | 168篇 |
2016年 | 282篇 |
2015年 | 199篇 |
2014年 | 339篇 |
2013年 | 693篇 |
2012年 | 871篇 |
2011年 | 1137篇 |
2010年 | 820篇 |
2009年 | 804篇 |
2008年 | 914篇 |
2007年 | 912篇 |
2006年 | 935篇 |
2005年 | 744篇 |
2004年 | 658篇 |
2003年 | 510篇 |
2002年 | 486篇 |
2001年 | 906篇 |
2000年 | 609篇 |
1999年 | 501篇 |
1998年 | 329篇 |
1997年 | 343篇 |
1996年 | 262篇 |
1995年 | 216篇 |
1994年 | 209篇 |
1993年 | 162篇 |
1992年 | 178篇 |
1991年 | 156篇 |
1990年 | 145篇 |
1989年 | 121篇 |
1988年 | 97篇 |
1987年 | 87篇 |
1986年 | 71篇 |
1985年 | 77篇 |
1984年 | 57篇 |
1983年 | 37篇 |
1982年 | 28篇 |
1981年 | 28篇 |
1980年 | 17篇 |
1978年 | 17篇 |
1977年 | 18篇 |
1976年 | 27篇 |
1975年 | 28篇 |
1974年 | 21篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
S. J.?Yuan Y. X.?Sui S. M.?ZhouEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,44(4):557-562
Exchange-coupled wedged-permalloy (Py)/FeMn bilayers are studied by ferromagnetic resonance (FMR) technique at room temperature. In comparison, Py single layer films were also made. For Py single layer films and Py/FeMn bilayers, only one uniform resonance peak was observed at high magnetic fields, indicating no interfacial diffusion at the Py/FeMn and Py/Cu interfaces. Negative isotropic in-plane resonance field does exist in Py/FeMn bilayers and its magnitude increases with decreasing Py layer thickness. In order to explain above phenomena, interfacial perpendicular anisotropy must be considered simultaneously, in addition to irreversible rotation of spins in FeMn layers. This is because the perpendicular resonance field of the bilayers is larger than that of Py single layer films. 相似文献
952.
S.?Barland X.?Hachair M.?GiudiciEmail author S.?Balle J. R.?Tredicce G.?Tissoni L.?Spinelli L.?Lugiato M.?Brambilla 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,32(1):75-82
We analyze experimentally the spatio-temporal dynamics of the
transverse structures appearing in broad area edge-emitting
semiconductor amplifiers under CW optical injection. We
demonstrate that, in certain conditions, the light reflected by
the system exhibits a multipeaked structure whose dependence on
the parameters suggests an interpretation in terms of
cavity solitons. These structures can exhibit self-pulsations with
periods of the order of few milliseconds, which we explain in
terms of regenerative thermal oscillations. In a particular device,
we generate two single-peak structures which are spatially
uncorrelated, as required for cavity solitons. A microscopic model
shows good agreement with the main body of the experimental
results. 相似文献
953.
S. H. Li C. Wang J. S. Liu X. X. Wang R. X. Li G. Q. Ni Z. Z. Xu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,34(1-3):215-218
Using time-of-flight spectrometry, the interaction of intense femtosecond
laser pulses with argon clusters has been studied by measuring the energy
and yield of emitted ions. With two different supersonic nozzles, the
dependence of average ion energy
on cluster size
in a large range of
has been measured. The experimental results indicate that
when the cluster size
, the average ion
energy
Coulomb explosion is the
dominant expansion mechanism. Beyond this size, the average ion energy gets
saturated gradually, the clusters exhibit a mixed Coulomb-hydrodynamic
expansion behavior. We also find that with the increasing gas backing
pressure, there is a maximum ion yield, the ion yield decreases as the gas
backing pressure is further increased. 相似文献
954.
J.?Zhu Y.-P.?Lu X.-R.?ChenEmail author Y.?Cheng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,33(1):43-48
The intermolecular interaction potentials of van der
Waals Ar-N2 complex have been studied by ab initio calculations using the single
and double excitation coupled cluster [CCSD(T)] theory with perturbative
triples correction. The full counterpoise method is applied to correct the
basis set superposition error (BSSE). It is found that the T-shaped
structure is the most stable conformation with the well depth De of
12.40 meV at the minimum distance Rm of 3.70 Å. The calculated anisotropic
values for Rm, R0 and De are 0.56 Å,
0.54 Å and 2.68 meV, respectively. Compared with those obtained by others, our
calculated PES seems to be in better agreement with experiments. 相似文献
955.
Background
Analysis of fatty acid composition of biological materials is a common task in lipid research. Conventionally, preparation of samples for fatty acid analysis by gas chromatography involves two separate procedures: lipid extraction and methylation. This conventional method is complicated, tedious and time consuming. Development of a rapid and simple method for lipid analysis is warranted. 相似文献956.
A high-throughput experimental methodology was developed for photocatalysis reaction. In this work, a CCD imaging analysis system and photocatalytic reactor for UV light was designed and tested. By making use of the technologies, we have screened several catalyst libraries. From the SiO2-supported single component catalyst library, we found that TiO2, ZrO2, Nb2O5, and WO3 were good candidates for highly active catalyst formulation. We designed and screened several triangle catalyst libraries and found that the WO3- and Nb2O5-codoped TiO2 catalyst showed much higher photodegradation activities for the degradation of 1,6-hexamethylenediamine than did the pure TiO2 catalyst. The doping of ZrO2 into TiO2 did not generate apparent positive effects on catalytic activity. 相似文献
957.
We report the observation of individual steps taken by motor proteins in living cells by following movements of endocytic vesicles that contain quantum dots (QDs) with a fast camera. The brightness and photostability of quantum dots allow us to record motor displacement traces with 300 micros time resolution and 1.5 nm spatial precision. We observed individual 8 nm steps in active transport toward both the microtubule plus- and minus-ends, the directions of kinesin and dynein movements, respectively. In addition, we clearly resolved abrupt 16 nm steps in the plus-end direction and often consecutive 16 nm and occasional 24 nm steps in minus-end directed movements. This work demonstrates the ability of the QD assay to probe the operation of motor proteins at the molecular level in living cells under physiological conditions. 相似文献
958.
Huang JY Chen S Jo SH Wang Z Han DX Chen G Dresselhaus MS Ren ZF 《Physical review letters》2005,94(23):236802
We report the atomic-scale imaging with concurrent transport measurements of the breakdown of individual multiwall carbon nanotubes inside a transmission electron microscope equipped with a piezomanipulator. We found unexpectedly three distinct breakdown sequences: namely, from the outermost wall inward, from the innermost wall outward, and alternatively between the innermost and the outmost walls. Remarkably, a significant amount of current drop was observed when an innermost wall is broken, proving unambiguously that every wall is conducting. Moreover, the breakdown of each wall in any sequence initiates in the middle of the nanotube, not at the contact, proving that the transport is not ballistic. 相似文献
959.
In a two-dimensional soap film convection experiment, the velocity fields are found to be strongly intermittent in the buoyancy subrange, which was reported to be nonintermittent in a recent numerical simulation. The structure functions Sq(l)(= ) exhibit self-similar structures and can be described by power laws l(zetaq) for integers 8 > or = q < or = 1. By extending Kolmogorov's refined similarity hypothesis to our system, an analytical form is derived for the scaling exponent zeta(q) = q/2 + (mu/18)(3q - q2). Our measurements yield mu = 0.42, which is significantly greater than 0.2 found in high Reynolds number turbulence in wind tunnels. 相似文献
960.
Tian CS Qian D Wu D He RH Wu YZ Tang WX Yin LF Shi YS Dong GS Jin XF Jiang XM Liu FQ Qian HJ Sun K Wang LM Rossi G Qiu ZQ Shi J 《Physical review letters》2005,94(13):137210
The body-centered-cubic (bcc) phase of Ni, which does not exist in nature, has been achieved as a thin film on GaAs(001) at 170 K via molecular beam epitaxy. The bcc Ni is ferromagnetic with a Curie temperature of 456 K and possesses a magnetic moment of 0.52+/-0.08 micro(B)/atom. The cubic magnetocrystalline anisotropy of bcc Ni is determined to be +4.0x10(5) ergs x cm(-3), as opposed to -5.7x10(4) ergs x cm(-3) for the naturally occurring face-centered-cubic (fcc) Ni. This sharp contrast in the magnetic anisotropy is attributed to the different electronic band structures between bcc Ni and fcc Ni, which are determined using angle-resolved photoemission with synchrotron radiation. 相似文献