全文获取类型
收费全文 | 1210篇 |
免费 | 30篇 |
国内免费 | 8篇 |
专业分类
化学 | 880篇 |
晶体学 | 21篇 |
力学 | 20篇 |
数学 | 86篇 |
物理学 | 241篇 |
出版年
2021年 | 8篇 |
2020年 | 20篇 |
2019年 | 12篇 |
2018年 | 17篇 |
2017年 | 14篇 |
2016年 | 19篇 |
2015年 | 13篇 |
2014年 | 32篇 |
2013年 | 51篇 |
2012年 | 63篇 |
2011年 | 86篇 |
2010年 | 45篇 |
2009年 | 44篇 |
2008年 | 86篇 |
2007年 | 76篇 |
2006年 | 75篇 |
2005年 | 53篇 |
2004年 | 44篇 |
2003年 | 56篇 |
2002年 | 42篇 |
2001年 | 24篇 |
2000年 | 16篇 |
1999年 | 13篇 |
1998年 | 9篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 19篇 |
1993年 | 11篇 |
1992年 | 8篇 |
1991年 | 11篇 |
1990年 | 5篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 20篇 |
1985年 | 26篇 |
1984年 | 15篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 24篇 |
1975年 | 17篇 |
1974年 | 13篇 |
1973年 | 5篇 |
1968年 | 5篇 |
1966年 | 5篇 |
排序方式: 共有1248条查询结果,搜索用时 15 毫秒
1.
Tetsuo Irifune Chiaki Ueda Shohei Ohshita Hiroaki Ohfuji Takehiro Kunimoto Toru Shinmei 《高压研究》2020,40(1):96-106
ABSTRACTNano-polycrystalline diamond (NPD) with various grain sizes has been synthesized from glassy carbon at pressures 15–25?GPa and temperatures 1700–2300°C using multianvil apparatus. The minimum temperature for the synthesis of pure NPD, below which a small amount of compressed graphite was formed, significantly increased with pressure from ~1700°C at 15?GPa to ~1900°C at 25?GPa. The NPD having grain sizes less than ~50?nm was synthesized at temperatures below ~2000°C at 15?GPa and ~2300°C at 25?GPa, above which significant grain growth was observed. The grain size of NPD decreases with increasing pressure and decreasing temperature, and the pure NPD with grain sizes less than 10?nm is obtained in a limited temperature range around 1800–2000°C, depending on pressure. The pure NPD from glassy carbon is highly transparent and exhibits a granular nano-texture, whose grain size is tunable by selecting adequate pressure and temperature conditions. 相似文献
2.
Yukio Iida Masahiro Shibutani Katsuhiko Kobayashi Kazuhiko Ohnuma Yoichi Miyake Toru Noda 《Optical Review》2006,13(2):87-92
The double-pass method is thought to obtain the point spread function (PSF) in human eyes based on two techniques: the symmetric
double-pass method using the same pupil size and the asymmetric double-pass method using a different pupil size. The symmetric
double-pass method provides autocorrelation of the retinal PSF and, thus, the modulation transfer function. The asymmetric
double-pass method provides low-frequency partial-phase information and the partial phase-retrieval algorithm is applied to
obtain the complete-phase information, and to estimate the PSF. The partial phase-retrieval algorithm is based on the iteration
method proposed by Fineup and Kowalczyk and requires a lengthy computation. In this study, we propose a new high-speed phase-retrieval
algorithm based on the property that the real and imaginary parts of optical transfer functions (OTFs) continuously change
in value. 相似文献
3.
The existence of a Nash equilibrium in the undiscounted repeated two-person game of incomplete information on one side is
established. The proof depends on a new topological result resembling in some respect the Borsuk-Ulam theorem. 相似文献
4.
We study two estimators of the long-range parameter of a covariance stationary linear process. We show that one of the estimators
achieve the optimal semiparametric rate of convergence, whereas the other has a rate of convergence as close as desired to
the optimal rate. Moreover, we show that the estimators are asymptotically normal with a variance, which does not depend on
any unknown parameter, smaller than others suggested in the literature. Finally, a small Monte Carlo study is included to
illustrate the finite sample relative performance of our estimators compared to other suggested semiparametric estimators.
More specifically, the Monte-Carlo experiment shows the superiority of the proposed estimators in terms of the Mean Squared
Error.
The first author research was funded by the Economic and Social Research Council (ESRC) reference number: R000238212. The
second author research was funded by the Ministry of Education, Culture, Sports and Technology of Japan, reference number:
09CE2002 and B(2)10202202. 相似文献
5.
6.
Takaaki Kakitsuka Shinji Matsuo Seok–Hwan Jeong Toru Segawa Hiroshi Okamoto Yoshihiro Kawaguchi Yasuhiro Kondo Yuzo Yoshikuni Hiroyuki Suzuki 《Optical and Quantum Electronics》2006,38(12-14):1053-1060
We theoretically investigated a digitally tunable laser with a chirped ladder filter and a ring resonator to obtain a wide wavelength tuning range covering the whole C- or L- band. The clear relation between the tuning range and laser structure, especially the ladder filter, is described analytically. The introduction of a chirped structure into a ladder filter is effective in achieving both wide tunability and a stable lasing mode. A numerical simulation based on multimode rate equations shows that a tuning range of over 40 nm and a mode suppression ratio over 40 dB can be achieved by introducing a chirped ladder filter. 相似文献
7.
8.
9.
Kimio Asaka Yoshihito Hirano Kenji Tatsumi Kumio Kasahara Toru Tajime 《Optical Review》1998,5(5):310-314
We propose a new detection method for a pseudo-random frequency modulation continuous wave (RM-CW) coherent lidar. The feature of this method is modulation of local beam with a time delayed pseudo-random sequence. Heterodyne detection and correlation detection between the received beam and the local beam are simultaneously carried out in an optical field. In the RM-CW coherent lidar using the optical field correlation detection method, the received equipment is greatly simplified. We carried out preliminary experiments and demonstrated that the new method is effective for detection of a CW coherent lidar. 相似文献
10.
N Fujii T Watanabe A Otaka K Bessho I Yamamoto T Noda H Yajima 《Chemical & pharmaceutical bulletin》1987,35(12):4769-4776