全文获取类型
收费全文 | 20250篇 |
免费 | 3487篇 |
国内免费 | 2287篇 |
专业分类
化学 | 14533篇 |
晶体学 | 221篇 |
力学 | 1125篇 |
综合类 | 111篇 |
数学 | 2225篇 |
物理学 | 7809篇 |
出版年
2024年 | 45篇 |
2023年 | 434篇 |
2022年 | 433篇 |
2021年 | 704篇 |
2020年 | 842篇 |
2019年 | 814篇 |
2018年 | 717篇 |
2017年 | 648篇 |
2016年 | 978篇 |
2015年 | 969篇 |
2014年 | 1127篇 |
2013年 | 1513篇 |
2012年 | 1840篇 |
2011年 | 1783篇 |
2010年 | 1215篇 |
2009年 | 1124篇 |
2008年 | 1279篇 |
2007年 | 1202篇 |
2006年 | 1077篇 |
2005年 | 981篇 |
2004年 | 696篇 |
2003年 | 622篇 |
2002年 | 580篇 |
2001年 | 473篇 |
2000年 | 415篇 |
1999年 | 474篇 |
1998年 | 391篇 |
1997年 | 373篇 |
1996年 | 364篇 |
1995年 | 305篇 |
1994年 | 260篇 |
1993年 | 233篇 |
1992年 | 180篇 |
1991年 | 158篇 |
1990年 | 163篇 |
1989年 | 138篇 |
1988年 | 89篇 |
1987年 | 60篇 |
1986年 | 78篇 |
1985年 | 69篇 |
1984年 | 41篇 |
1983年 | 32篇 |
1982年 | 35篇 |
1981年 | 20篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1977年 | 6篇 |
1975年 | 3篇 |
1973年 | 4篇 |
1916年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 750 毫秒
11.
Tianyu Gong Longhai Guo Jun Ye Lifan He Teng Qiu Xiaoyu Li 《Journal of polymer science. Part A, Polymer chemistry》2021,59(16):1807-1820
The implementation of covalent adaptable networks (CANs) in general resin system is becoming attractive. In this work, we propose a simple post-curing strategy based on the core-shell structured acrylate latex for the achievement on both the improved general performance and the CANs characteristics in latex films. The building to the CANs was relied on the introduction of 4,4′-diaminophenyl disulfide as the curing agent, which cured the acetoacetoxy decorated shell polymer through the ketoamine reaction. The metathesis reaction of aromatic disulfides in the crosslinking segments enabled the thermally induced dynamic behavior of the network as revealed in the stress relaxation tests by comparison with other diamine crosslinking agents without the incorporation of disulfide. The synergism of the dynamic crosslinking of the shell polymer and static crosslinking in the core polymer contributed to the improved mechanical strength (15 MPa, strain% = 250%) and the suppressed water adsorption (~1% in 24 h of soaking) of the latex film, which exhibited above 90% of recovery in both strength and strain from a cut-off film damage within 1 h at 80°C. Moreover, the cured latex film could be recycled, and 75% of the mechanical performance was regained after three fragmentation-hot-pressing cycles. These, in addition with the feasible and environmental friendly characteristics, suggest a sustainable paradigm toward the smart thermosetting latex polymers. 相似文献
12.
13.
14.
15.
16.
17.
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
18.
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
19.
20.
He Haidong Yang Haifeng Zhou Longpeng Chen Tianchi 《Journal of Russian Laser Research》2015,36(3):292-299
Ni–Co alloys have a wide range of applications in various fields owning to their excellent physical, chemical, and mechanical properties. In this paper, we prepare Ni–Co alloy coatings on 316L stain steel surfaces by electroplating. We present a novel approach utilizing a nanosecond laser to induce microtextures on Ni–Co alloy coatings. We study experimentally the effects of laser power and scanning rate on the surface morphologies of Ni–Co alloy coatings. The results indicate that the shape and size of induced microtextures can be controlled by the laser power and scanning rate. The size of grains increases with increase in the work current of the laser (WCL) at a certain scanning rate. With the WCL constant, the size of grains decreases with increase in scanning rate while their average height increases. It is a simple and easily-controlled method for the fabrication of microstructures on Ni–Co alloy coatings, which has promising applications in investigations of the properties of microtextured surfaces, such as friction, adhesion, and wetting. 相似文献