全文获取类型
收费全文 | 45603篇 |
免费 | 1452篇 |
国内免费 | 265篇 |
专业分类
化学 | 31865篇 |
晶体学 | 313篇 |
力学 | 1021篇 |
综合类 | 1篇 |
数学 | 7659篇 |
物理学 | 6461篇 |
出版年
2022年 | 236篇 |
2021年 | 506篇 |
2020年 | 713篇 |
2019年 | 731篇 |
2018年 | 476篇 |
2017年 | 413篇 |
2016年 | 1000篇 |
2015年 | 924篇 |
2014年 | 1040篇 |
2013年 | 2361篇 |
2012年 | 2318篇 |
2011年 | 2884篇 |
2010年 | 1449篇 |
2009年 | 1300篇 |
2008年 | 2380篇 |
2007年 | 2461篇 |
2006年 | 2373篇 |
2005年 | 2331篇 |
2004年 | 1970篇 |
2003年 | 1678篇 |
2002年 | 1549篇 |
2001年 | 612篇 |
2000年 | 549篇 |
1999年 | 493篇 |
1998年 | 510篇 |
1997年 | 570篇 |
1996年 | 645篇 |
1995年 | 477篇 |
1994年 | 492篇 |
1993年 | 502篇 |
1992年 | 437篇 |
1991年 | 423篇 |
1990年 | 351篇 |
1989年 | 374篇 |
1988年 | 375篇 |
1987年 | 358篇 |
1986年 | 330篇 |
1985年 | 488篇 |
1984年 | 581篇 |
1983年 | 390篇 |
1982年 | 586篇 |
1981年 | 570篇 |
1980年 | 490篇 |
1979年 | 496篇 |
1978年 | 530篇 |
1977年 | 448篇 |
1976年 | 435篇 |
1975年 | 402篇 |
1974年 | 405篇 |
1973年 | 371篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Daylight photodynamic therapy (DPDT) is an effective and patient preferred treatment for the management of field change actinic keratosis. An important factor in DPDT is light dosimetry, to ensure that patients receive sufficient daylight for effective treatment, and this is the focus of the contribution to this issue by (La Rochelle et al. [2019] Photochem. Photobiol., https://doi.org/10.1111/php.13170 ). In this work, the authors present an easy-to-use method for obtaining real-time information about patient received light dose during treatment and for determining indoor locations best suited to DPDT. 相似文献
12.
13.
Hui Li Jian Liu Juan Zhao Huiting He Dr. Dabo Jiang Prof. Steven Robert Kirk Prof. Qiong Xu Dr. Xianxiang Liu Prof. Dulin Yin 《ChemistryOpen》2021,10(4):477-485
A series of tetraimidazolium salts with different anions was prepared and applied in the isomerization of β-pinene oxide. After examining the activity of different catalysts, a remarkable enhancement of the selectivity of perillyl alcohol (47 %) was obtained over [PEimi][HNO3]4 under mild reaction conditions and using DMSO as the solvent. Furthermore, noncovalent interactions between solvent molecules and the catalyst were found by FT-IR spectroscopy and confirmed by computational chemistry. The homogeneous catalyst showed excellent stability and was reused up to six times without significant loss. 相似文献
14.
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
15.
Photoisomerisation in Aminoazobenzene‐Substituted Ruthenium(II) Tris(bipyridine) Complexes: Influence of the Conjugation Pathway
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Anissa Amar Dr. Paul Savel Dr. Huriye Akdas‐Kilig Dr. Claudine Katan Prof. Hacène Meghezzi Prof. Abdou Boucekkine Dr. Jean‐Pierre Malval Dr. Jean‐Luc Fillaut 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8262-8270
Transition‐metal complexes containing stimuli‐responsive systems are attractive for applications in optical devices, photonic memory, photosensing, as well as luminescence imaging. Amongst them, photochromic metal complexes offer the possibility of combining the specific properties of the metal centre and the optical response of the photochromic group. The synthesis, the electrochemical properties and the photophysical characterisation of a series of donor–acceptor azobenzene derivatives that possess bipyridine groups connected to a 4‐dialkylaminoazobenzene moiety through various linkers are presented. DFT and TD‐DFT calculations were performed to complement the experimental findings and contribute to their interpretation. The position and nature of the linker (ethynyl, triazolyl, none) were engineered and shown to induce different electronic coupling between donor and acceptor in ligands and complexes. This in turn led to strong modulations in terms of photoisomerisation of the ligands and complexes. 相似文献
16.
17.
Physical aging in amorphous poly(ethylene furanoate): Enthalpic recovery,density, and oxygen transport considerations
下载免费PDF全文
![点击此处可从《Journal of Polymer Science.Polymer Physics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Steven K. Burgess Christopher R. Mubarak Robert M. Kriegel William J. Koros 《Journal of Polymer Science.Polymer Physics》2015,53(6):389-399
The current work utilizes three separate techniques to study the physical aging process in amorphous poly(ethylene furanoate) (PEF), which is a recently introduced engineering thermoplastic with enhanced properties compared to petroleum‐sourced poly(ethylene terephthalate). Differential scanning calorimetry aging experiments were conducted at multiple aging temperatures and times, and the resultant enthalpic recovery values compared to the theoretical maximum enthalpy loss evaluated from calculations involving extrapolation of the equilibrium liquid line. Density measurements reveal densification of the matrix for the aged versus unaged samples, and provide an estimate for the reduction in free volume for the aged samples. Complementary oxygen permeation and pressure‐decay sorption experiments provide independent verification of the free volume reduction mechanism for physical aging in glassy polymers. The current work provides the first detailed aging study for PEF. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 389–399 相似文献
18.
19.
20.