全文获取类型
收费全文 | 77696篇 |
免费 | 322篇 |
国内免费 | 374篇 |
专业分类
化学 | 23960篇 |
晶体学 | 789篇 |
力学 | 6720篇 |
数学 | 31926篇 |
物理学 | 14997篇 |
出版年
2018年 | 10436篇 |
2017年 | 10257篇 |
2016年 | 6053篇 |
2015年 | 837篇 |
2014年 | 284篇 |
2013年 | 303篇 |
2012年 | 3760篇 |
2011年 | 10476篇 |
2010年 | 5615篇 |
2009年 | 6028篇 |
2008年 | 6566篇 |
2007年 | 8733篇 |
2006年 | 199篇 |
2005年 | 1284篇 |
2004年 | 1511篇 |
2003年 | 1955篇 |
2002年 | 997篇 |
2001年 | 239篇 |
2000年 | 285篇 |
1999年 | 150篇 |
1998年 | 188篇 |
1997年 | 142篇 |
1996年 | 194篇 |
1995年 | 114篇 |
1994年 | 74篇 |
1993年 | 92篇 |
1992年 | 52篇 |
1991年 | 63篇 |
1990年 | 49篇 |
1989年 | 58篇 |
1988年 | 58篇 |
1987年 | 57篇 |
1986年 | 57篇 |
1985年 | 46篇 |
1984年 | 42篇 |
1983年 | 36篇 |
1982年 | 41篇 |
1981年 | 38篇 |
1980年 | 46篇 |
1979年 | 44篇 |
1978年 | 34篇 |
1973年 | 25篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1910年 | 24篇 |
1909年 | 41篇 |
1908年 | 40篇 |
1907年 | 32篇 |
1904年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
We have studied the tunneling conductance in ferromagnet/insulator/p-wave superconductor junctions, taking into account the
rough interface scattering effect. We find that there exist zero-bias conductance peaks and single-minimum structure in tunneling
spectroscopy. As the exchange energy increases, the Andreev reflection is always suppressed and the differential conductance
decreases. The differential conductance depends on the barrier strength and the roughness at the interface.
Supported by the Natural Science Foundation of Jiangsu Higher Education Institutions, China (Grant No. 06KJB140009) 相似文献
982.
We review recent structural studies that we have undertaken aimed at elucidating the fundamental properties of metal-organic
framework materials and their interactions with hydrogen. We have shown that exposing coordinatively unsaturated metal centers
can greatly enhance the hydrogen binding energy and that they result in a significant increase of the surface packing density
of adsorbed hydrogen molecules on materials’ surface. We will review some of the structural aspects of these materials, especially
the adsorbed hydrogen molecule surface packing density in one type of metal-organic framework, MOF-74, which can be packed
even denser than that in solid hydrogen.
相似文献
983.
The phase diagram of the coupled sine circle map system exhibits a variety of interesting phenomena including spreading regions
with spatiotemporal intermittency, non-spreading regions with spatial intermittency, and coherent structures termed solitons.
A spreading to non-spreading transition is seen in the system. A cellular automaton version of the coupled system maps the
spreading to non-spreading transition to a transition from a probabilistic to a deterministic cellular automaton. The solitonic
sector of the system shows spatiotemporal intermittency with soliton creation, propagation and absorption. A probabilistic
cellular automaton mapping is set up for this sector which can identify each one of these phenomena.
相似文献
984.
Maleic anhydride was grafted by long-chain alcohols (1-hexadecanol, 1-octadecanol) to amphiphilic mono-L cis-butene dicarboxylates (L = hexadecyl, octadecyl), i.e., MAH, MAO, respectively. Subsequently, corresponding amphiphilic cerium
complexes with these two mono-L cis-butene dicarboxylate ligands (Ce(L')3, L'= MAH, MAO) were synthesized and behaved as the precursors to prepare CeO2 nanoparticles for both of which can form nanosized micelle-like aggregates by special self-assembly in the wet chemical process.
The nanoparticles were further characterized by Fourier transform-infrared spectroscopy (FTIR), Diffuse reflectance ultraviolet-visible
spectra (DRUVS), scanning electron microscope (SEM), transmission electron microscope (TEM), and x-ray diffraction (XRD).
Both the CeO2 nanoparticles are in a cubic fluorite structure and present regular and well-dispersion club-like morphology with average
particle size in the range of 40–70 nm. Besides, the strong ultraviolet–visible absorption for these CeO2 nanoparticles can be found at the long-wavelength ultraviolet to visible region of 200–500 nm. 相似文献
985.
Xinzheng Zhang Jingmin Zhang Li Chen Jun Xu Liping You Dapeng Yu 《Applied Physics A: Materials Science & Processing》2008,92(3):669-672
In order to well understand the growth mechanism of the diverse morphology of the ZnO nanostructures, in situ analysis of
the formation of different ZnO nanostructures, such as nanowires, nanocombs, and nanosheets, has been conducted in an environmental
scanning electron microscope (ESEM). It is found that both nanocombs and nanosheets grew in two-stage heating processes on
parent nanowires. The difference is that the nanocombs were synthesized in extremely high pressure of zinc vapor via a self-catalyzed
vapor-liquid-solid process, while the ZnO nanosheets were grown in relatively low pressure of zinc vapor. All the growth processes
were revealed in real time imaging. It is demonstrated that the change in the growth environments can influence the thickness
of the ZnO polycrystalline surface of the zinc powder, which alters the pressure of the zinc vapor and in turn determines
the morphology of the final nanostructures. 相似文献
986.
Jiří Herec 《Czechoslovak Journal of Physics》2004,54(12):1473-1481
In this paper the quantum-statistical properties of light beams propagating in a directional nonlinear coupler are investigated.
This device is composed of a pair of linearly coupled nonlinear waveguides operating by means of degenerate parametric downconversion.
The possibility of generation of nonclassical states of light in single and compound modes, using the short-length approximation,
is discussed. Influence of linear and nonlinear mismatches for generation of nonclassical light is taken into account.
This work was supported by Project LN00A015, Research Project No. CEZ: J14/98 and the COST project OC P11.003 of the Czech
Ministry of Education. 相似文献
987.
Using a right-angled magnetic air prism, we have achieved a separation of ~10 arcsec between ~2 arcsec wide up and down-spin peaks of 5.4 Å neutrons. The polarised neutron option has thus been introduced into the SUSANS instrument. Strongly spindependent SUSANS spectra have been observed over ±1.3 × 10?4 Å?1 range for several magnetic alloy samples. Spatial pair-distribution functions for the up and down-spins as well as the nuclear and magnetic scattering length density distributions in the micrometer domain, have been deduced from these spectra. 相似文献
988.
John F. Gunion 《Pramana》2004,62(2):283-305
I summarize the basic theory and selected phenomenology for the Higgs boson(s) of the standard model, the minimal supersymmetric
model and some extensions thereof, including the next-to-minimal supersymmetric model. 相似文献
989.
Novel effects resulting from joint action of chirality and non-linearity are discussed using a basic equation describing the
temporal evolution of fields in a chiral medium with Kerr non-linearity. The spatial chirality effect is characterized through
the Born-Fedorov formalism. Our simulations are based on the split-step Fourier method and the solution of the Stokes parameters.
The numerical results show the chiral effect on solitons with circular polarization and mixed polarization spatial solitons. 相似文献
990.
Francesco Chiadini Antonio Scaglione Gaetano Panariello 《Optical and Quantum Electronics》2004,36(11):981-995
A numerical method for calculating cutoff frequencies of modes of weakly guiding optical fibers is described. Starting from a properly constructed field representation, the method follows a variational approach to obtain an eigenvalue problem for the cutoff frequencies which can be easily solved by a standard numerical routine. The field representation uses an expansion in terms of the Laguerre–Gauss functions in the fiber core and limiting form for small arguments of modified Bessel functions in the fiber cladding. Fibers with power-law refractive index profiles and fibers with a profile showing a dip on the axis are analyzed. Results obtained for modes of arbitrary order (both azimuthal and radial) show that our method is very efficient and accurate. 相似文献