全文获取类型
收费全文 | 1550篇 |
免费 | 379篇 |
国内免费 | 87篇 |
专业分类
化学 | 781篇 |
晶体学 | 51篇 |
力学 | 9篇 |
综合类 | 8篇 |
数学 | 7篇 |
物理学 | 1160篇 |
出版年
2024年 | 7篇 |
2023年 | 11篇 |
2022年 | 35篇 |
2021年 | 43篇 |
2020年 | 52篇 |
2019年 | 34篇 |
2018年 | 40篇 |
2017年 | 48篇 |
2016年 | 91篇 |
2015年 | 72篇 |
2014年 | 113篇 |
2013年 | 166篇 |
2012年 | 96篇 |
2011年 | 81篇 |
2010年 | 74篇 |
2009年 | 94篇 |
2008年 | 94篇 |
2007年 | 109篇 |
2006年 | 86篇 |
2005年 | 79篇 |
2004年 | 82篇 |
2003年 | 80篇 |
2002年 | 52篇 |
2001年 | 36篇 |
2000年 | 43篇 |
1999年 | 38篇 |
1998年 | 32篇 |
1997年 | 32篇 |
1996年 | 39篇 |
1995年 | 31篇 |
1994年 | 29篇 |
1993年 | 22篇 |
1992年 | 12篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有2016条查询结果,搜索用时 15 毫秒
71.
72.
A three-dimensional chiral metamaterial consisting of arrays of the multi-layered mutually twisted metallic spirals is proposed. We theoretically demonstrate such a chiral spiral structure exhibiting negative refractive index at terahertz frequencies. The chirality with varied refractive index can be obtained by change of configurations of the structure. The presented design offers flexibility for investigation of electromagnetic properties of chiral metamaterials in the terahertz regime and thus leads to a unique route to terahertz device applications. 相似文献
73.
Covalently Assembled Dipeptide Nanospheres as Intrinsic Photosensitizers for Efficient Photodynamic Therapy in Vitro 下载免费PDF全文
Xiaoke Yang Jinbo Fei Qi Li Prof. Dr. Junbai Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(19):6477-6481
Monodispersed diphenylalanine‐based nanospheres with excellent biocompatibility are fabricated through a facile covalent reaction‐induced assembly. Interestingly, the nanospheres exhibit red autofluorescence. Most importantly, such assembled dipeptide nanospheres can serve as intrinsic photosensitizer to convert O2 to singlet oxygen (1O2). Thus, photodynamic therapy in vitro can be achieved effectively. The versatile strategy could be extended to other biomolecules containing a primary amine group for the fabrication of potential intrinsic photosensitizers. 相似文献
74.
Y. Benmimoun A. Bouhemadou R. Khenata A. H. Reshak B. Amrani M. Ameri H. Baltache 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(2):165-171
The results of first-principles theoretical study of the structural,
electronic and optical properties of SrCl2 in its cubic structure, have
been performed using the full-potential linear augmented plane-wave method
plus local orbitals (FP-APW+lo) as implemented in the WIEN2k code. In this
approach both the local density approximation (LDA) and the generalized
gradient approximation (GGA) are used for the exchange-correlation (XC)
potential. Also we have used the Engel-Vosko GGA formalism, which optimizes
the corresponding potential for band structure calculations. We performed
these calculations with and without spin-orbit interactions. Including
spin-orbit coupling cause to lifts the triple degeneracy at Γ point
and a double degeneracy at X point. Results are given for structural
properties. The pressure dependence of elastic constants and band gaps are
investigated. The dielectric function, reflectivity spectra and refractive
index are calculated up to 30 eV. Also we calculated the pressure and volume
dependence of the static optical dielectric constant. 相似文献
75.
The structure and optical properties of the films of ternary compounds AgInSe2, CuInSe2 and Cu
x
Ag1–x
InSe2 solid solutions obtained by pulsed laser evaporation are investigated. It has been established that the films like bulk crystals have the structure of chalcopyrite. By the transmission and reflection spectra near the edge of natural absorption the refractive index and coefficient of optical absorption are calculated and the energies of interband transitions and the crystalline and spinorbit splitting are determined. 相似文献
76.
The radial wave functions of inner electron shell and outer electron shell of a Ne atom were obtained by the approximate analytical
method and tested by calculating the ground state energy of the Ne atom. The equivalent volume of electron cloud and the refractive
index of Ne were calculated. The calculated refractive index agrees well with the experimental result. Relationship between
the refractive index and the wave function of Ne was discovered.
Supported by the New Star Program of Beijing Science and Technology, China (Grant No. 952870400), the Beijing Municipal Commission
of Education, and the Excellent Young Teachers Program of Ministry of Education, China 相似文献
77.
M. E. Bashtanov N. N. Drozdova A. A. Krasnovskii 《Journal of Applied Spectroscopy》1999,66(4):550-555
The relative intensity of photosensitized phosphorescence of singlet oxygen (1O2) at 1270 nm (L1270) and1O2-induced delayed fluorescence (Ldf) of bacteriopheophytin a (BPh) (770 nm) in air-saturated solutions of BPh in hexafluorobenzene in excitation by 337-nm pulses
of a nitrogen laso is investigated. It is established that Ldf≪L1270. The ratio of the initial intensity of delayed fluorescence and phosphorescence of1O2(Ldf)0/(L1270)0 changed from 0.02 to 0.30 as a function of the energies of laser pulses (2.5–5.0 mJ/cm1) and the BPh concentration (6–18 μM). As the index of quantum efficiency of the delayed fluorescence, the authors used the
coefficient
where [1O2]0 is the initial concentration of1O2 after the laser burst; [Bpn] is the concentration of BPh; kr is the constant of the rate of1O2 radiative deactivation in the solvent under study; γf is the quantum yield of BPh fluorescence. It is established that this
coefficient is smaller by a factor of ∼2000 than in phthalocyanine, while its absolute value is ∼2·1010M−2sec−1. The saturation of BPh solutions with oxygen at atmospheric pressure is shown to lead to a fivefold attenuation of the delayed
fluorescence as compared to air-saturated solutions. The possibility of BPh triplet molecules being involved in the radiation
of delayed fluorescence of the pigment is discussed.
Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 504–508, July–August, 1999. 相似文献
78.
Effects of Refractive Index and Viscosity on Fluorescence and Anisotropy Decays of Enhanced Cyan and Yellow Fluorescent Proteins 总被引:1,自引:1,他引:0
The fluorescence lifetime strongly depends on the immediate environment of the fluorophore. Time-resolved fluorescence measurements of the enhanced forms of ECFP and EYFP in water–glycerol mixtures were performed to quantify the effects of the refractive index and viscosity on the fluorescence lifetimes of these proteins. The experimental data show for ECFP and EYFP two fluorescence lifetime components: one short lifetime of about 1 ns and a longer lifetime of about 3.7 ns of ECFP and for EYFP 3.4. The fluorescence of ECFP is very heterogeneous, which can be explained by the presence of two populations: a conformation (67% present) where the fluorophore is less quenched than in the other conformation (33% present). The fluorescence decay of EYFP is much more homogeneous and the amplitude of the short fluorescence lifetime is about 5%. The fluorescence anisotropy decays show that the rotational correlation time of both proteins scales with increasing viscosity of the solvent similarly as shown earlier for GFP. The rotational correlation times are identical for ECFP and EYFP, which can be expected since both proteins have the same shape and size. The only difference observed is the slightly lower initial anisotropy for ECFP as compared to the one of EYFP. 相似文献
79.
K. Nakayama H. Tazawa S. Okajima K. Kawahata K. Tanaka T. Tokuzawa Y. Ito 《International Journal of Infrared and Millimeter Waves》2003,24(9):1421-1430
A diagnostic system using short-wavelength far-infrared (FIR) lasers (40–70 m in wavelength) is now being developed for high density and large volume plasmas. In the wavelength region, a CVD-diamond is the excellent materials for optical windows of the laser and the plasma vessel and beam splitters of a multichannel interferometer. To design these optical elements, the optical constants (refractive index n, absorption coefficient and transmissivity T) of the CVD-diamond have been measured precisely by using FIR lasers of 48-, 57- and 71-m in wavelength. As an example, the result for 57.1511 m light is n = 2.383(1) ± 0.002, = 0.19 ± 0.05 cm-1 and T = 97.5 ± 1.5% at 1.023 mm in thickness. 相似文献
80.
N. E. Koval'skaya N. A. Kuznetsova O. L. Kaliya N. S. Gretsova I. V. Sokolova 《Journal of Applied Spectroscopy》2001,68(2):287-290
Using zinc octa(diethoxyphosphenylmethyl)phthalocyanine as an example, we determined experimentally the quantum yield of generation of singlet oxygen () which makes it possible to evaluate quantitatively the efficiency of photogeneration of 1O2 and the influence of biomolecules on this parameter. It is shown that the efficiency of generation of singlet oxygen by the sensitizers used in photodynamic therapy depends on their state in a solution and increases with disaggregation of the dye and its interaction with biomolecules. It is established that phthalocyanine in an aqueous buffer solution sensitizes the formation of 1O2 with the quantum yield = 0.16 ± 0.02. On introduction of the detergent Triton X100 into the buffer solution of phthalocyanine, increases up to 0.48 ± 0.07. In a microheterogeneous medium (buffer + albumin) = 0.42. 相似文献