全文获取类型
收费全文 | 73425篇 |
免费 | 12851篇 |
国内免费 | 7279篇 |
专业分类
化学 | 50818篇 |
晶体学 | 657篇 |
力学 | 4740篇 |
综合类 | 310篇 |
数学 | 8198篇 |
物理学 | 28832篇 |
出版年
2024年 | 279篇 |
2023年 | 1601篇 |
2022年 | 2718篇 |
2021年 | 2788篇 |
2020年 | 3106篇 |
2019年 | 2906篇 |
2018年 | 2564篇 |
2017年 | 2335篇 |
2016年 | 3569篇 |
2015年 | 3474篇 |
2014年 | 4135篇 |
2013年 | 5307篇 |
2012年 | 6729篇 |
2011年 | 6725篇 |
2010年 | 4468篇 |
2009年 | 4252篇 |
2008年 | 4591篇 |
2007年 | 4107篇 |
2006年 | 3755篇 |
2005年 | 3131篇 |
2004年 | 2425篇 |
2003年 | 1919篇 |
2002年 | 1760篇 |
2001年 | 1472篇 |
2000年 | 1356篇 |
1999年 | 1540篇 |
1998年 | 1305篇 |
1997年 | 1291篇 |
1996年 | 1289篇 |
1995年 | 1050篇 |
1994年 | 921篇 |
1993年 | 763篇 |
1992年 | 674篇 |
1991年 | 580篇 |
1990年 | 501篇 |
1989年 | 384篇 |
1988年 | 335篇 |
1987年 | 274篇 |
1986年 | 249篇 |
1985年 | 204篇 |
1984年 | 143篇 |
1983年 | 102篇 |
1982年 | 80篇 |
1981年 | 67篇 |
1980年 | 65篇 |
1979年 | 33篇 |
1978年 | 30篇 |
1977年 | 40篇 |
1976年 | 30篇 |
1973年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Chao Liu Liying Wang Lin Yang Famei Wang Chunhong Xu Jingwei Lv Guanglai Fu Xianli Li Qiang Liu Haiwei Mu Tao Sun Paul K. Chu 《Physics letters. A》2019,383(25):3200-3206
A single-polarization filter comprising a gold-coated photonic crystal fiber based on surface plasmon resonance is designed and investigated. The pattern matching and coupled polarization characteristics analyzed by the full-vector finite element method (FEM) and losses at 1,540 nm are achieved to 1,016.01739 dB/cm (x-pol core mode) and 33.81917 dB/cm (y-pol core mode). The crosstalk (CT) value of the 1,540 nm band is ?853.12653 dB for fiber length and the bandwidth is 850 nm. The working wavelength of the filter ranges from 1,280 nm to 1,540 nm by varying the diameter of outer air holes (), the diameter of inner air holes (), the metal film thickness (t), as well as the liquid refractive index (n). 相似文献
62.
Numerical Algorithms - A singularly perturbed Volterra integro-differential equation with an integrable singularity in the integral term is considered. The upwind difference method is used to... 相似文献
63.
Aequationes mathematicae - We discuss equivalence conditions for the non-existence of non-trivial meromorphic solutions to the Fermat Diophantine equation $$f^m(z)+g^n(z)=1$$ with integers $$m,n\ge... 相似文献
64.
65.
66.
In this Letter,a novel system for adaptively correcting the phase of a dynamic multimode beam is proposed.While using merely one spatial light modulator,the phase measurement of the first-order diffraction pattern and the correction of the zeroth diffraction order are simultaneously realized.The real-time experimental result is obtained at a control rate of 10 Hz.The power-in-the-bucket value is improved from 38.5%to 61.8%,even with fundamental mode content that is consistently below 30%.To the best of our knowledge,this is the first implementation of real-time adaptive correction of the entire multimode beam. 相似文献
67.
Floquet engineering appears as a new protocol for designing topological states of matter,and features anomalous edge modes pinned at quasi-energy π/T with vanished topological index.We propose how to predict the anomalous edge modes via the bulk Hamiltonian in frequency space,and use Zak phase to quantitatively index the topological properties.The above methods are clarified by the example of time periodic Kitaev chain with chemical potential of harmonic driving and pulse driving,and topological phase transitions are manifested at different driving frequencies. 相似文献
68.
69.
In order to improve the signal-to-noise ratio and mitigate the damage of noise to the communication quality,an effective interference suppression algorithm,which is based on the improved density-based spatial clustering of applications with noise algorithms,is proposed for visible light communication systems using the complementary metal–oxide–semiconductor image sensor as the receiver.Experimental results show that the algorithm can learn the region where the payload data is located,filter out the noise data,and greatly decrease the interference.The effect of the algorithm is also studied through bit error ratio performance. 相似文献
70.
Dr. Feifan Wang Jie Tian Dr. Mengzhu Li Dr. Weizhen Li Dr. Lifang Chen Xiaozhi Liu Dr. Jian Li Aidaer Muhetaer Prof. Dr. Qi Li Prof. Dr. Yuan Wang Prof. Dr. Lin Gu Prof. Dr. Ding Ma Prof. Dr. Dongsheng Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(21):8280-8286
Fully utilizing solar energy for catalysis requires the integration of conversion mechanisms and therefore delicate design of catalyst structures and active species. Herein, a MOF crystal engineering method was developed to controllably synthesize a copper–ceria catalyst with well-dispersed photoactive Cu-[O]-Ce species. Using the preferential oxidation of CO as a model reaction, the catalyst showed remarkably efficient and stable photoactivated catalysis, which found practical application in feed gas treatment for fuel cell gas supply. The coexistence of photochemistry and thermochemistry effects contributes to the high efficiency. Our results demonstrate a catalyst design approach with atomic or molecular precision and a combinatorial photoactivation strategy for solar energy conversion. 相似文献