全文获取类型
收费全文 | 3159篇 |
免费 | 95篇 |
国内免费 | 24篇 |
专业分类
化学 | 2585篇 |
晶体学 | 25篇 |
力学 | 18篇 |
数学 | 177篇 |
物理学 | 473篇 |
出版年
2023年 | 19篇 |
2022年 | 22篇 |
2021年 | 32篇 |
2020年 | 42篇 |
2019年 | 59篇 |
2018年 | 40篇 |
2017年 | 35篇 |
2016年 | 68篇 |
2015年 | 89篇 |
2014年 | 82篇 |
2013年 | 144篇 |
2012年 | 212篇 |
2011年 | 247篇 |
2010年 | 133篇 |
2009年 | 131篇 |
2008年 | 226篇 |
2007年 | 208篇 |
2006年 | 173篇 |
2005年 | 189篇 |
2004年 | 182篇 |
2003年 | 145篇 |
2002年 | 152篇 |
2001年 | 50篇 |
2000年 | 48篇 |
1999年 | 40篇 |
1998年 | 35篇 |
1997年 | 27篇 |
1996年 | 37篇 |
1995年 | 30篇 |
1994年 | 30篇 |
1993年 | 29篇 |
1992年 | 29篇 |
1991年 | 24篇 |
1990年 | 20篇 |
1989年 | 23篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 23篇 |
1985年 | 33篇 |
1984年 | 25篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1972年 | 7篇 |
排序方式: 共有3278条查询结果,搜索用时 15 毫秒
91.
Hirosawa K Furumochi H Tada A Kannari F Takeoka M Sasaki M 《Physical review letters》2005,94(20):203601
To the best of our knowledge, we demonstrate for the first time the generation of photon number squeezing by spectral filtering for ultrabroadband light generated by microstructure fibers at 800 nm. A maximum squeezing of 4.6 dB is observed, corresponding to 10.3 dB after correcting for detection losses. We numerically analyzed the quantum dynamics of ultrashort laser pulse propagation through optical fibers by solving a nonlinear quantum Schr?dinger equation that included Raman scattering, especially for the quantum correlation of photon number fluctuation among frequency modes in broadband pulses. 相似文献
92.
We propose a fundamental interconnection method using a polarization alignment system for waveguides having different spatial
modes. In addition, as an example for the verification of the fundamental operation, we demonstrate an interconnection between
a photonic crystal fiber and a laser that have obviously different spatial modes. The polarization alignment system operates
synergistically with a self-written waveguide formed with a double phaseconjugate mirror. This technique enables us to interconnect
a photonic crystal fiber with a laser source without complicated and time-consuming optical alignment. In this method, although
it is not necessary to perform an external control for interconnection, the waveguide most suitable for connection is formed
autonomously in a Sn2P2S6:Sb crystal developed for this purpose. There was a marked reduction in the polarization dependence of coupling efficiency,
compared with that observed using a stand-alone double phase-conjugate mirror. 相似文献
93.
T1ρ imaging is useful in a number of clinical applications. T1ρ preparation methods, however, are sensitive to non-uniformities of the B0 magnetic field and the B1 RF field. These common system imperfections can result in image artifacts and quantification errors in T1ρ imaging. We report on a phase-cycling method which can eliminate B1 RF inhomogeneity effects in T1ρ imaging. This method does not only correct for image artifacts but also for T2ρ contamination caused by B1 RF inhomogeneity. The presence of B0 magnetic field inhomogeneity can compromise the effectiveness of this method for B1 RF inhomogeneity correction. We demonstrate that, by combining the spin-locking scheme reported by Dixon et al. (Myocardial suppression in vivo by spin locking with composite pulses. Magn Reson Med 1996; 36:90-94) with phase cycling, we can simultaneously correct B0 magnetic field inhomogeneity effects and B1 RF inhomogeneity effects in T1ρ imaging. Phantom and in vivo data sets are used to demonstrate the proposed methods and to compare them with other existing T1ρ preparation methods. 相似文献
94.
Yukinobu Mild Atsushi Onae Tomizo Kurosawa Eiichi Sakuma 《International Journal of Infrared and Millimeter Waves》1993,14(11):2345-2359
A system for measuring the absolute frequency of a far-infrared (FIR) laser is described. Josephson point contacts have been utilized in the system as a frequency harmonic mixer connecting microwaves and optically pumped CH3OH laser lines. The Josephson point contacts are capable of generating beat signals of 90 GHz microwaves and FIR waves of up to 4.25 THz. To measure the frequency of the beat signals from the Josephson junction with a frequency counter, tracking oscillators have been developed, which tracks the beat signals by phase locking and regenerate clean signals for frequency counting. It is shown that the absolute frequency can be measured to an accuracy of about 100 Hz by using the tracking oscillators. 相似文献
95.
Effects of a finite ion temperature on the Hall magnetohydrodynamics (MHD), which breaks down for a finite ion temperature, are clarified in terms of a rigorous three-field kinetic dispersion relation. The MHD mode equation becomes anisotropic with respect to the ion pressure because of the double adiabaticity in ion dynamics. 相似文献
96.
Kumagai Yuta Kimura Atsushi Taguchi Mitsumasa Watanabe Masayuki 《Journal of Radioanalytical and Nuclear Chemistry》2018,316(1):341-348
Journal of Radioanalytical and Nuclear Chemistry - This study aims to demonstrate that zeolite has the potential to increase the efficiency of radiolysis treatment of aqueous organic pollutants by... 相似文献
97.
98.
Yasuyuki Mori Atsushi Sudo Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2019,57(7):792-798
A series of soluble oligo(spiroorthocarbonate)s (OSOCs) were synthesized by polycondensation of tetraethylorthocarbonate with pentaerythritol derivatives. The pentaerythritol derivatives used herein were synthesized from pentaerythritol by attaching substituents on it to improve the solubility of themselves and the resulting OSOCs. The structures of the OSOCs were confirmed by NMR spectroscopy and MALDI‐TOF mass analysis. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 792–798 相似文献
99.
100.
Naoto Sato Taiki Hayashi Kazuma Tochigi Prof. Hiroaki Wada Prof. Atsushi Shimojima Prof. Kazuyuki Kuroda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(33):7860-7865
Eight corners of a double-four ring cage-type germanoxane, containing a fluoride ion, were successfully silylated by the combination of chlorosilanes and silazanes. Three different silyl groups, trimethylsilyl, dimethylsilyl, and dimethylvinylsilyl, were attached on the corners of germanoxane cage. The solubility and reactivity of the cage modified with dimethylvinylsilyl groups were significantly increased, allowing for further reaction. Hydrosilylation reaction between dimethylvinylsilylated cage geramanoxanes and dimethylsilylated cage siloxanes afforded porous solids. Functionalization of the corners of germanoxanes with silyl groups should provide valuable building blocks in various functional materials. 相似文献