全文获取类型
收费全文 | 26819篇 |
免费 | 572篇 |
国内免费 | 112篇 |
专业分类
化学 | 15426篇 |
晶体学 | 179篇 |
力学 | 805篇 |
综合类 | 10篇 |
数学 | 3602篇 |
物理学 | 7481篇 |
出版年
2023年 | 125篇 |
2022年 | 343篇 |
2021年 | 413篇 |
2020年 | 390篇 |
2019年 | 375篇 |
2018年 | 421篇 |
2017年 | 386篇 |
2016年 | 695篇 |
2015年 | 585篇 |
2014年 | 684篇 |
2013年 | 1093篇 |
2012年 | 1405篇 |
2011年 | 1634篇 |
2010年 | 941篇 |
2009年 | 840篇 |
2008年 | 1346篇 |
2007年 | 1272篇 |
2006年 | 1154篇 |
2005年 | 1598篇 |
2004年 | 1606篇 |
2003年 | 1135篇 |
2002年 | 797篇 |
2001年 | 624篇 |
2000年 | 587篇 |
1999年 | 363篇 |
1998年 | 302篇 |
1997年 | 296篇 |
1996年 | 369篇 |
1995年 | 319篇 |
1994年 | 311篇 |
1993年 | 335篇 |
1992年 | 320篇 |
1991年 | 268篇 |
1990年 | 224篇 |
1989年 | 207篇 |
1988年 | 182篇 |
1987年 | 176篇 |
1986年 | 177篇 |
1985年 | 231篇 |
1984年 | 215篇 |
1983年 | 186篇 |
1982年 | 190篇 |
1981年 | 191篇 |
1980年 | 171篇 |
1979年 | 151篇 |
1978年 | 178篇 |
1977年 | 143篇 |
1976年 | 138篇 |
1974年 | 134篇 |
1973年 | 124篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
S. S. Banerjee S. Goldberg Y. Myasoedov M. Rappaport E. Zeldov A. Soibel F. de la Cruz J. van der Beek M. Konczykowski T. Tamegai V. Vinokur 《Pramana》2006,66(1):43-54
Disorder and porosity are parameters that strongly influence the physical behavior of materials, including their mechanical,
electrical, magnetic and optical properties. Vortices in superconductors can provide important insight into the effects of
disorder because their size is comparable to characteristic sizes of nanofabricated structures. Here we present experimental
evidence for a novel form of vortex matter that consists of inter-connected nanodroplets of vortex liquid caged in the pores
of a solid vortex structure, like a liquid permeated into a nanoporous solid skeleton. Our nanoporous skeleton is formed by
vortices pinned by correlated disorder created by high-energy heavy ion irradiation. By sweeping the applied magnetic field,
the number of vortices in the nanodroplets is varied continuously from a few to several hundred. Upon cooling, the caged nanodroplets
freeze into ordered nanocrystals through either a first-order or a continuous transition, whereas at high temperatures a uniform
liquid phase is formed upon delocalization-induced melting of the solid skeleton. This new vortex nanoliquid displays unique
properties and symmetries that are distinct from both solid and liquid phases. 相似文献
992.
Jong Seong Bae Kyoo Sung Shim Soung-soo Yi Young Soo Kim 《Applied Surface Science》2006,252(13):4564-4568
The influence of lithium doping on the crystallization, the surface morphology, and the luminescent properties of pulsed laser deposited Y2−xGdxO3:Eu3+ thin film phosphors was investigated. The crystallinity, the surface morphology, and the photoluminescence (PL) of films depended highly on the Li-doping and the Gd content. The relationship between the crystalline and morphological structures and the luminescent properties was studied, and Li+ doping was found to effectively enhance not only the crystallinity but also the luminescent brightness of Y2−xGdxO3:Eu3+ thin films. In particular, the incorporation of Li and Gd into the Y2O3 lattice could induce remarkable increase in the PL. The highest emission intensity was observed Li-doped Y1.35Gd0.6O3:Eu3+ thin films whose brightness was increased by a factor of 4.6 in comparison with that of Li-doped Y2O3:Eu3+ thin films. 相似文献
993.
d'Espinose de Lacaillerie JB Fretigny C Massiot D 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2008,192(2):244-251
Structural disorder at the scale of two to three atomic positions around the probe nucleus results in variations of the EFG and thus in a distribution of the quadrupolar interaction. This distribution is at the origin of the lineshape tailing toward high fields which is often observed in the MAS NMR spectra of quadrupolar nuclei in disordered solids. The Czjzek model provides an analytical expression for the joint distribution of the NMR quadrupolar parameters upsilon(Q) and eta from which a lineshape can be predicted. This model is derived from the Central Limit Theorem and the statistical isotropy inherent to disorder. It is thus applicable to a wide range of materials as we have illustrated for 27Al spectra on selected examples of glasses (slag), spinels (alumina), and hydrates (cement aluminum hydrates). In particular, when relevant, the use of the Czjzek model allows a quantitative decomposition of the spectra and an accurate extraction of the second moment of the quadrupolar product. In this respect, it is important to realize that only rotational invariants such as the quadrupolar product can make sense to describe the quadrupolar interaction in disordered solids. 相似文献
994.
S. Gaspard M. Oujja R. de Nalda M. Castillejo L. Bañares S. Lazare R. Bonneau 《Applied Physics A: Materials Science & Processing》2008,93(1):209-213
We have recently shown that irradiation of self-standing films of the biopolymers collagen and gelatine with single femtosecond
laser pulses produces a nanofoaming layer with regular bubble size which can be controlled by wavelength selection. Following
these initial studies, here we report on the temporal evolution of the foaming effect by measurements in situ and in real
time of the change in the transmittance of a cw probe HeNe laser through the irradiated films. Self standing films of the
biopolymers were irradiated with 90 fs laser pulses at 800, 400, and 266 nm. For fluences below and above the modification
threshold a permanent attenuation of the transmission occurs (increasing with fluence). The initial decay of the transmission
is fast (around few tens of ns), and is followed by dynamics in the longer timescale (micro and milliseconds). The temporal
evolution of the transmission measured upon fs laser irradiation is similar with that determined in the irradiation of the
biopolymer films at 248 nm with 25 ns laser pulses. The method allows separating in time the different processes occurring
after irradiation that lead to a permanent nanofoaming structure, while the results allow us to understand the mechanisms
of femtosecond laser processing of the biopolymers and their interest in biomedical applications. 相似文献
995.
F. Martinez-Pinon J. A. Alvarez-Chavez D. Jaramillo-Vigueras L. de la Cruz-May H. L. Offerhaus 《Laser Physics》2008,18(11):1340-1343
Results on high radiance Yb3+-doped fiber lasers with novel double innerclad structures (double-D clad and four hole) and polarized output at ≈1090 nm are presented. We have demonstrated >40% of the total output power being polarized, making the fiber laser suitable for LIDAR and second-harmonic generation (SHG) applications. It also showed a 10-nm tuning range with low (less than 10 mW) average power variations. The narrow linewidth source was pumped with a low cost, low brightness laser diode, and exhibited a relatively low slope efficiency, which gives room for improvement by using a 976-nm pump source where Yb3+ has a narrower linewidth and at least five times higher absorption. 相似文献
996.
T. Voigt M.O. Lenz F. Mitschke E. Roldán G.J. de Valcárcel 《Applied physics. B, Lasers and optics》2004,79(2):175-183
It has been suggested (by Pessina et al. in 1997) that the observed spontaneous mode beating of erbium-doped-fiber ring lasers can be explained as the multimode instability described in 1968 by Risken and Nummedal and by Graham and Haken (the RNGH instability), which is based on Rabi-splitting-induced gain. If true, this would constitute the first ever example of this instability in an actual experiment. We test the hypothesis through a quantitative experimental investigation. We demonstrate that there is indeed a clear, marked onset of the instability, a fact that went unnoticed in all previous experiments because it is very close to the lasing threshold. We intentionally raise cavity loss to better separate onset of lasing and of instability. We obtain quantitative information on the instability onset. An interpretation as the predicted second threshold is reasonable provided inhomogeneous gain line broadening is taken into account. We also observe that instability above its onset exists only intermittently; this may hint at a subcritical bifurcation and noise-driven transitions. In any event, the RNGH mechanism is present, if not in a pure form. PACS 42.65.Sf; 42.60.Mi; 42.55.Wd 相似文献
997.
M. Sawicka I. Matea H. Grawe R. Grzywacz M. Pfützner M. Lewitowicz J. M. Daugas B. A. Brown A. Lisetskiy F. Becker G. Bélier C. Bingham R. Borcea E. Bouchez A. Buta E. Dragulescu G. de France G. Georgiev J. Giovinazzo F. Hammache F. Ibrahim P. Mayet V. Méot F. Negoita F. De Oliveira-Santos O. Perru O. Roig K. Rykaczewski M. G. Saint-Laurent J. E. Sauvestre O. Sorlin M. Stanoiu I. Stefan C. Stodel Ch. Theisen D. Verney J. Żylicz 《The European Physical Journal A - Hadrons and Nuclei》2004,22(3):455-459
A decay spectroscopy study of the neutron-rich cobalt isotopes has been performed using fragmentation of a 86Kr36+ beam and the new LISE2000 spectrometer at GANIL. For 71Co and 73Co, the -delayed radiation has been observed for the first time, and the half-lives were found to be 79(5) ms and 41(4) ms, respectively. Features of the decay are discussed qualitatively in terms of nuclear models. 相似文献
998.
Microstructure characterization of titanium dioxide nanodispersions and thin films for dye-sensitized solar cell devices 总被引:1,自引:0,他引:1
P.?de AlmeidaEmail author J.?van Deelen C.?Catry H.?Sneyers T.?Pataki R.?Andriessen C.?Van Roost J.M.?Kroon 《Applied Physics A: Materials Science & Processing》2004,79(7):1819-1828
This article reports on the microstructure characterization of titanium dioxide nanodispersions and thin films made thereof for dye-sensitized solar cell devices. Structure–property relationships have been investigated mainly using electron microscopy to assess how microstructure (crystalline structure, defects) and morphological (e.g. heterogeneities, inclusions, voids) features in the electron transport element of the solar cell device correlate with electrical performance, namely, short-circuit photocurrent density (Jsc). This work shows that for a nanodispersion synthesized in the laboratory different electrical performances are measurable depending on the thin film forming process, more specifically, heat-sintering at 450 °C or pressure-sintering at 500 bar. For the heat-sintered device Jsc is about 7.3 mA/cm2 whereas for the pressure-sintered one this value is much lower, this difference being attributed to the existence of inclusions in the titanium dioxide matrix, which are spatially isolated from the rest of the electron transport element thereby limiting the charge transport process by promoting their premature recombination. PACS 68.37.Lp; 73.61.Le; 81.40.-z; 84.60.Jt 相似文献
999.
Mutual mass diffusion and thermal diffusion has been investigated in poly(dimethylsiloxane)/ poly(ethylmethylsiloxane) (PDMS/PEMS) polymer blends of equal weight fractions. Molar masses ranged from below 1 to over 20 kg/mol. Both the mutual mass (D) and the thermal diffusion (DT) coefficient contain a thermally activated factor with an activation temperature of 1415 K. The molar mass dependence of DT is due to an end-group effect of the local friction coefficient. The thermal diffusion coefficient in the limit of long chains and infinite temperature is DT0, = - 1.69×10-7cm2(sK)-1. The Soret coefficient ST of blends far enough away from a critical point is proportional to the static structure factor S(q = 0). 相似文献
1000.