全文获取类型
收费全文 | 3307篇 |
免费 | 76篇 |
国内免费 | 12篇 |
专业分类
化学 | 2496篇 |
晶体学 | 37篇 |
力学 | 56篇 |
数学 | 197篇 |
物理学 | 609篇 |
出版年
2022年 | 31篇 |
2021年 | 23篇 |
2020年 | 37篇 |
2019年 | 56篇 |
2018年 | 34篇 |
2017年 | 18篇 |
2016年 | 53篇 |
2015年 | 37篇 |
2014年 | 59篇 |
2013年 | 129篇 |
2012年 | 138篇 |
2011年 | 184篇 |
2010年 | 85篇 |
2009年 | 105篇 |
2008年 | 176篇 |
2007年 | 178篇 |
2006年 | 192篇 |
2005年 | 175篇 |
2004年 | 148篇 |
2003年 | 127篇 |
2002年 | 105篇 |
2001年 | 77篇 |
2000年 | 58篇 |
1999年 | 56篇 |
1998年 | 33篇 |
1997年 | 38篇 |
1996年 | 51篇 |
1995年 | 40篇 |
1994年 | 31篇 |
1993年 | 44篇 |
1992年 | 51篇 |
1991年 | 35篇 |
1990年 | 37篇 |
1989年 | 38篇 |
1988年 | 45篇 |
1987年 | 37篇 |
1986年 | 31篇 |
1985年 | 72篇 |
1984年 | 50篇 |
1983年 | 34篇 |
1982年 | 42篇 |
1981年 | 46篇 |
1980年 | 36篇 |
1979年 | 51篇 |
1978年 | 37篇 |
1977年 | 33篇 |
1976年 | 26篇 |
1975年 | 33篇 |
1974年 | 28篇 |
1973年 | 29篇 |
排序方式: 共有3395条查询结果,搜索用时 15 毫秒
141.
A spin-Peierls system (DMe-DCNQI)2Li is studied with W-band electron paramagnetic resonance (EPR) ( approximately 94 GHz) to unveil a charge transport mechanism in the insulating 4k(F) charge density wave state above T(SP). The electron hopping between the neighbor DCNQI columns provides an additional broadening of the EPR linewidth, since the neighbor columns are generally nonequivalent to each other with respect to g shift. The obtained intercolumn hopping rates lead us to the conclusion that the electron hopping to a hole soliton carrying a fractional charge of e / 2 in the neighbor column dominates the intercolumn charge transport. 相似文献
142.
The present investigation deals with the light-driven morphological changes in multilamella films of N-methyl-4-octadecyloxystilbazolium arylcarboxylates (C18OStz+X-) cast on glass slides. The results of XRD analysis show a photostimulated layer expansion and shrinkage of the stacked thin films along the c-axis under alternative illumination at >350 and 254 nm, respectively. It was revealed that such lamellar changes could be switched either way by a reversible transformation between the mono- and bilayer units in these stacked multilamella films. Moreover, such controlled structural adjustments in the alignment could be initiated by the photocyclodimerization of the stilbazolium moieties of the arylcarboxylate salts; i.e., a monolayer-to-bilayer transformation could be induced at a stage of only 10% cyclodimer formation. The photoinduced patterning on the surface of the films was also analyzed by SEM and fluorescence microscopic investigations. 相似文献
143.
Let X and Y be Banach spaces and ψ a continuous convex function on the unit interval [0,1] satisfying certain conditions. Let X⊕ψY be the direct sum of X and Y equipped with the associated norm with ψ. We show that X⊕ψY is uniformly convex if and only if X,Y are uniformly convex and ψ is strictly convex. As a corollary we obtain that the ?p,q-direct sum (not p=q=1 nor ∞), is uniformly convex if and only if X,Y are, where ?p,q is the Lorentz sequence space. These results extend the well-known fact for the ?p-sum . Some other examples are also presented. 相似文献
144.
145.
Okamura H Kawahara J Nanba T Kimura S Soda K Mizutani U Nishino Y Kato M Shimoyama I Miura H Fukui K Nakagawa K Nakagawa H Kinoshita T 《Physical review letters》2000,84(16):3674-3677
Optical conductivity data of the intermetallic compounds (Fe1-xVx)3Al ( 0=x=0.33) reveal that their density of states around the Fermi energy ( E(F)) is strongly reduced as x is increased. In particular, Fe2VAl ( x = 0.33) has a deep, well-developed pseudogap of 0.1-0.2 eV at E(F) and a small density ( approximately 5x10(20) cm(-3)) of carriers, which is highly unusual for intermetallic compounds. It is shown that the pseudogap results from the band structure of Fe2VAl, rather than from temperature-dependent correlation effects. Based on the present results, we propose a simple model that consistently explains both the semiconductorlike transport and the metallic photoemission results previously observed for Fe2VAl. 相似文献
146.
K. Kato K. Tanaka S. Kayukawa K. Suzuki Y. Masuda T. Kimura K. Nishizawa T. Miki 《Applied Physics A: Materials Science & Processing》2007,88(2):273-276
CaBi4Ti4O15 (CBTi144) micro-plateaus were fabricated on Si wafers and Pt foils using a self-assembled monolayer (SAM) and a complex metal
alkoxide solution. The micro-plateaus are delineated by metal masks, which are used for shadowing against the ultraviolet
(UV) irradiation for decomposition of SAM to make the surface hydrophilic. The micro-plateaus crystallized to a ferroelectric
phase with random orientation. The crystallization depended on the SAM-derived ultra thin layers at the surface of the substrates.
The primitive PFM measurements without any top electrodes confirmed that the micro-plateaus exhibited the piezoresponse behaviors.
The piezoelectric constant, d33, had some distribution, and the maximum d33 was confirmed as about 45 pm/V, which is identical to the d33 of the polar-axis oriented CBTi144 thin films.
PACS 77.84.-s; 81.20.Fw; 77.65.-j 相似文献
147.
Oxygen adsorption on a C-terminated α-Mo2C(0 0 0 1) surface has been investigated with Auger electron spectroscopy, low-energy electron diffraction, and angle-resolved photoemission spectroscopy utilizing synchrotron radiation. It is found that the oxygen atoms adsorb on the Mo atoms in the second layer forming a (1 × 1) orthorhombic periodicity. The oxygen adsorption induces a peculiar state around the Fermi level, which is observed at 0.4 eV in the normal-emission spectra. ARPES measurements show that the state is a partially occupied metallic state. The photoionization cross section of the state shows a maximum at the photon energy of 56 eV, which is assigned as originating from the resonance of the Mo 4d photoemission involving Mo 4p → 4d photoexcitation. 相似文献
148.
A high-resolution angle-resolved photoemission spectroscopy (ARPES) study of Fe(1 1 0) single crystal was conducted to elucidate many-body interactions between quasi-particles at the Fermi level at low-temperature. Two kink structures were observed in the energy-band dispersion at the binding energies of ∼40 meV and ∼270 meV for the bulk-derived band on the majority-spin Fermi surface around the Γ point. Based on analyses of the experimentally obtained real parts of the self-energy, these kink structures are derived from electron-phonon and electron-magnon interactions. 相似文献
149.
We are concerned with a general model of size structured population dynamics with the growth rate depending on the individual's size and time. In this paper, we shall study the continuous dependence of the solution on all given data such as aging and birth functions, growth rate functions and initial data. 相似文献
150.
Dova E Peschar R Sakata M Kato K Schenk H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(19):5043-5052
The spin-crossover complex [Fe(teec)(6)](ClO(4))(2) (teec = chloroethyltetrazole) exhibits a 50 % incomplete spin crossover in the temperature range 300-30 K. Time-resolved synchrotron powder diffraction experiments have been carried out to elucidate its structural behavior. We report crystal structure models of this material at 300 K (high spin) and 90 K (low spin), as solved from synchrotron powder diffraction data by using Genetic Algorithm and Parallel Tempering techniques and refined with Rietveld refinement. During short synchrotron powder diffraction experiments (five minutes duration) two distinguishable lattices were observed the quantities of which vary with temperature. The implication of this phenomenon, that is interpreted as a structural phase transition associated with the high-to-low spin crossover, and the structural characteristics of the high-spin and low-spin models are discussed in relation to other compounds showing a similar type of spin-crossover behavior. 相似文献