全文获取类型
收费全文 | 1198篇 |
免费 | 79篇 |
国内免费 | 173篇 |
专业分类
化学 | 426篇 |
晶体学 | 24篇 |
力学 | 37篇 |
综合类 | 10篇 |
数学 | 41篇 |
物理学 | 912篇 |
出版年
2024年 | 14篇 |
2023年 | 131篇 |
2022年 | 43篇 |
2021年 | 50篇 |
2020年 | 42篇 |
2019年 | 43篇 |
2018年 | 31篇 |
2017年 | 56篇 |
2016年 | 43篇 |
2015年 | 46篇 |
2014年 | 73篇 |
2013年 | 63篇 |
2012年 | 55篇 |
2011年 | 104篇 |
2010年 | 89篇 |
2009年 | 64篇 |
2008年 | 78篇 |
2007年 | 44篇 |
2006年 | 50篇 |
2005年 | 43篇 |
2004年 | 34篇 |
2003年 | 26篇 |
2002年 | 46篇 |
2001年 | 23篇 |
2000年 | 32篇 |
1999年 | 15篇 |
1998年 | 12篇 |
1997年 | 14篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 11篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 8篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有1450条查询结果,搜索用时 10 毫秒
1.
R. Bairava Ganesh Hitoshi Matsuo Takahiro Kawamura Yoshihiro Kangawa Koji Arafune Yoshio Ohshita Masafumi Yamaguchi Koichi Kakimoto 《Journal of Crystal Growth》2008,310(11):2697-2701
Multicrystalline silicon was grown by unidirectional solidification method using the accelerated crucible rotation technique. The application of the accelerated crucible rotation technique in unidirectional solidification method induced growth striations across the axial direction of the grown crystal. This striation pattern was observed from carbon concentration distribution, obtained by using Fourier transform infrared spectroscopy. The generated striation pattern was found to be weak and discontinuous. Some striations were absent, probably due to back melting, caused during each crucible rotation. From the growth striations and applied time period in crucible rotation, the growth rate was estimated by using Fourier transformation analysis. 相似文献
2.
B. Bavassano 《Il Nuovo Cimento C》1992,15(5):501-508
Summary A study has been promoted by NASA to evaluate the scientific return and the technological problems of a close-to-the-Sun mission
(Solar Probe). It has come out that using current technology it is possible to deliver at 4 solar radii from the Sun's centre
a scientific payload with such performances to allow a great improvement of our understanding of the coronal phenomena. The
mission concept currently under study uses planetary encounters to reach the required orbit. The final orbit period is 2.5
years, the estimated mission duration about 9 years. The orbit inclination is such as to give the maximum coverage in terms
of heliographic latitude. During the perihelion phases a conical structure shields the spacecraft from the intense solar radiation.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
3.
Solid solutions NaCl—CdCl2 were studied in an interval of CdCl2 concentrations of 0.05—3 mol.% by Raman spectroscopy. The molecular form Na2CdCl4 decomposes: Na2CdCl4 2Na+ + Cd2+ + 2Cl2
– + 2e–; 2Na + 2e– 2Na0. Free sodium atoms form color centers of crystal (F centers) in the region of jumpwise changing the partition coefficient of CdCl2 in NaCl (K jump). 相似文献
4.
In a novel parametrization of neutrino mixing and in the approximation of т-lepton dominance, we show that the one-loop renormalization-group equations (RGEs) of Dirac neutrinos are different from those of Majorana neutrinos even if two Majorana CP-violating phases vanish. As the latter can keep vanishing from the electroweak scale to the typical seesaw scale, it makes sense to distinguish between the RGE running effects of neutrino mixing parameters in Dirac and Majorana cases. The differences are found to be quite large in the minimal supersymmetric standard model with sizable tanβ, provided the masses of three neutrinos are nearly degenerate or have an inverted hierarchy. 相似文献
5.
H. J. Lewerenz K. Skorupska M. Aggour T. Stempel J. Grzanna 《Journal of Solid State Electrochemistry》2009,13(2):185-194
Photoelectrochemically prepared nanotopographies on semiconductors are used for realization of nanoemitter solar devices that
are active in the photovoltaic and the photoelectrocatalytic mode. The development of solar devices by a nonlinear electrochemical
process and combined chemical/electrochemical metal deposition is described. Based on this low-temperature scalable approach,
first efficiencies of 7.3% in the photovoltaic mode are reported for the photoelectrochemical solar cell n-Si/SiO2/Pt/I3
−–I−. With p-Si/Pt nanocomposite structures, light-induced H2 evolution is achieved. The surface chemistry and morphology is analyzed by photoelectron spectroscopy (PES), Fourier transform
infrared spectroscopy, and high-resolution scanning electron microscopy. The operational principle of Pt-based nanoemitter
solar devices that use silicon single crystal absorbers is analyzed by Mott–Schottky plots, chronoamperometric profiles, and
PES. Related to simultaneous oxide formation during Pt deposition, evidence for the formation of a metal–oxide–semiconductor
junction is obtained that explains the observed electronic behavior.
Contribution to the Fall Meeting of the European Materials Research Society, Symposium D: 9th International Symposium on Electrochemical/Chemical
Reactivity of Metastable Materials, Warsaw, 17th–21st September 2007. 相似文献
6.
Organic perovskite has potential to replace organic dye as light absorber in solar cell since it possesses better optical absorption in visible region than organic dye. This work is concerned with the investigation of the influence of CH3NH3PbI3 perovskite dipping time on the performance of perovskite-sensitized solar cell (PSSC). The effect of the dipping time on the morphology and photoluminescence of the sample has also been investigated. It was found that the device achieved a power conversion efficiency (PCE) as high as 5.57 ± 0.4% at the optimum dipping time of 4 h. The highest PCE is due to the highest IPCE, lowest Rct and the longest carrier lifetime (τ). 相似文献
7.
We report a new type of black silicon: flexible black silicon. A silicon-on-insulator (SOI) wafer is irradiated by automatically scanning a femtosecond laser and then split by etching out the SOI silica middle layer. Large-area, uniform micro spikes on the surface of a very thin flexible silicon layer are obtained. The black silicon shows good flexibility and optical properties. The absorption spectrum of the flexible black silicon is as high as 97% in the visible and insensitive to the change of the incident angle of the light, which makes it a potential good candidate as an absorber for the solar-thermo generator. 相似文献
8.
Summary In this note we describe the image acquisition system realized as a part of an experiment designed to record high-spectral-resolution
solar images in the visible part of the spectrum. The system is based on a Charge Coupled Device Thomson THX31159. The electronics
for driving the sensor and for the amplification and conditioning of the video signal has been designed and built in the laboratory,
while a VME-bus-based computer has been used for the timing of operations, for the signal A/D conversion and for image presentation
and storage.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
9.
XING Zhi-Zhong 《中国物理C(英文版)》2008,32(2):96-99
The observation of neutrino oscillations requires new physics beyond the standard model (SM).A SM-like gauge theory with p lepton families can be extended by introducing q heavy right-handed Majorana neutrinos but preserving its SU(2)L x U(1)y gauge symmetry.The overall neutrino mass matrix M turns out to be a symmetric (p+q) x (p+q) matrix.Given p>q,the rank of M is in general equal to 2q,corresponding to 2q non-zero mass eigenvalues.The existence of (p-q) massless left-handed Majorana neutrinos is an exact consequence of the model,independent of the usual approximation made in deriving the Type-I seesaw relation between the effective p x p light Majorana neutrino mass matrix M,and the q x q heavy Majorana neutrino mass matrix MR.In other words,the numbers of massive left- and right-handed neutrinos are fairly matched.A good example to illustrate this "seesaw fair play rule"is the minimal seesaw model with p = 3 and q = 2,in which one masslese neutrino sits on the unbalanced seesaw. 相似文献
10.
The effective action of chiral QCD2 was studied in
two-dimensional non-commutative space-time by using path integral
approach. It is shown that vector boson has a mass generation and
the effective Lagrangian contains a term corresponding to a
Wess-Zumino-Witten-like term. 相似文献