全文获取类型
收费全文 | 10833篇 |
免费 | 1457篇 |
国内免费 | 924篇 |
专业分类
化学 | 6512篇 |
晶体学 | 64篇 |
力学 | 483篇 |
综合类 | 154篇 |
数学 | 1139篇 |
物理学 | 4862篇 |
出版年
2024年 | 40篇 |
2023年 | 150篇 |
2022年 | 364篇 |
2021年 | 417篇 |
2020年 | 409篇 |
2019年 | 337篇 |
2018年 | 291篇 |
2017年 | 468篇 |
2016年 | 522篇 |
2015年 | 494篇 |
2014年 | 710篇 |
2013年 | 711篇 |
2012年 | 738篇 |
2011年 | 647篇 |
2010年 | 567篇 |
2009年 | 674篇 |
2008年 | 655篇 |
2007年 | 637篇 |
2006年 | 551篇 |
2005年 | 586篇 |
2004年 | 518篇 |
2003年 | 395篇 |
2002年 | 294篇 |
2001年 | 217篇 |
2000年 | 237篇 |
1999年 | 206篇 |
1998年 | 184篇 |
1997年 | 178篇 |
1996年 | 143篇 |
1995年 | 142篇 |
1994年 | 83篇 |
1993年 | 92篇 |
1992年 | 78篇 |
1991年 | 49篇 |
1990年 | 63篇 |
1989年 | 57篇 |
1988年 | 60篇 |
1987年 | 50篇 |
1986年 | 35篇 |
1985年 | 35篇 |
1984年 | 27篇 |
1983年 | 17篇 |
1982年 | 35篇 |
1981年 | 14篇 |
1980年 | 6篇 |
1979年 | 12篇 |
1978年 | 4篇 |
1971年 | 4篇 |
1969年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 463 毫秒
81.
The wavelet and harmonic filtering method suggested by Zalevsky and Ouzieli is introduced in this paper and adopted in our volume holographic image recognition system. This composite filter combines several scaled versions of the cascaded wavelet and harmonic filter, obtaining high discrimination ability and wide dynamic range of rotation and scale deformations. Optical experiments are conducted to demonstrate the validity and practicability of the algorithm. To the best of our knowledge, this is the first report of using this algorithm in a volume holographic system. Moreover, the separate correlation approach proposed in this paper greatly simplifies the manufacturing process and reduces the cost of the system. 相似文献
82.
Infrared (IR)-induced second-harmonic generation in the chalcogenide glasses is observed. A phenomenological approach of IR picosecond non-linear optical (NLO) response in glass is developed for the middle IR spectral range (5–15 μm). The observed effect is explained within the framework of fifth-order NLO susceptibilities. A model that reproduces the basic characteristics of the experimental data, in which the optical non-linearities caused by photoinduced electron–phonon anharmonic interactions, is proposed. The role of the IR-induced phase matching conditions in the observed phenomenon is discussed. 相似文献
83.
Torbjörn Kolsrud 《Journal of Theoretical Probability》1989,2(4):399-418
We derive explicit isomorphism formulas between weighted Dirichlet integrals for harmonic functions and boundary Dirichlet forms. Applications yield results on traces of Markov processes and convergence quasieverywhere of harmonic functions. 相似文献
84.
85.
Humans have always dreamt about the possibility of existence of planets in solar systems other than our own. After flying by, dropping probes, and even landing devices on most planets within our own solar system, the search for extra-solar planet is included in every proposal to either build a larger and better earth-, space-, or moon-based telescope, or observatory facility. The preliminary analysis seems to indicate that wavelength band from 25 μm to 30 μm is most promising in solving this problem. A number of IR technological challenges are to be overcome before the actual detection system can even be considered in a detailed design. The significant technical challenges of finding a planet will be described. Then details are given on the feasibility of detecting a planet with an instrument concept designed specifically for this purpose, a space-based, rotating rotationally shearing interferometer. 相似文献
86.
Uwe Bandelow Mindaugas Radziunas Andrei Vladimirov Bernd Hüttl Ronald Kaiser 《Optical and Quantum Electronics》2006,38(4-6):495-512
We study both theoretically and experimentally typical operation regimes of 40 GHz monolithic mode-locked lasers. The underlying
Traveling Wave Equation model reveals quantitative agreement for characteristics of the fundamental mode-locking as pulse
width and repetition frequency tuning, as well as qualitative agreement with the experiments for other dynamic regimes. Especially
the appearance of stable harmonic mode-locking at 80 GHz has been predicted theoretically and confirmed by measurements. Furthermore,
we derive and apply a simplified Delay-Differential-Equation model which guides us to a qualitative analysis of bifurcations
responsible for the appearance and the breakup of different mode-locking regimes. Higher harmonics of mode-locking are predicted
by this model as well. 相似文献
87.
Atsushi Kasue 《Potential Analysis》2006,24(2):137-194
We study spectral convergence of compact Riemannian manifolds or more generally certain Dirichlet spaces, obtaining some compactness
results on harmonic functions and harmonic maps.
Mathematics Subject Classifications (2000) 53C21, 58D17, 58J50.
Atsushi Kasue: Partly supported by the Grant-in-Aid for Scientific Research (B) No. 15340053 of the Japan Society for the
Promotion of Science. 相似文献
88.
《Surface and interface analysis : SIA》2006,38(1):19-24
We have been developing a new analytical transmission electron microscope (TEM), called a coincidence TEM, which in principle enables elemental mapping images to be observed at a high signal‐to‐noise (S/N) ratio under very low dose radiation conditions. In this paper, we report the development of a coincidence TEM with a digital waveform measuring system for obtaining a coincidence elemental mapping image. In this system, analog signals detected by a Si(Li) detector and a multianode, position‐sensitive photomultiplier (PSPM) are continuously converted into 12‐bit digital waveform data at a rate of 100 MHz, and transferred to a PC. From the transferred digital waveform data, information on X‐ray photon energy, electron incident position, and detection times of both X rays and electrons are calculated by digital waveform measurement, which lead to the observation of a successful coincidence elemental mapping image. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
89.
激光对生物分子的共振激发作用 总被引:7,自引:0,他引:7
在生物分子的“谐”和“非谐”振子势模型的基础上,用量子力学讨论了激光对生物分子的共振激作用;并用之对激光的生物激活、诱变机理的“共振吸收”定性理论作一解析分析。 相似文献
90.
透射式跑道能见度激光测量仪的研究 总被引:10,自引:0,他引:10
介绍了一种利用激光测量跑道水平及斜视能见度的智能化仪器。该仪器主要由光学系统、信号放大与处理系统及显示系统三部分组成。简要介绍了该仪器的基本结构、工作原理和主要技术指标,讨论了其中的技术难点及其相应的解决办法。 相似文献