全文获取类型
收费全文 | 83294篇 |
免费 | 1366篇 |
国内免费 | 989篇 |
专业分类
化学 | 27701篇 |
晶体学 | 838篇 |
力学 | 6971篇 |
综合类 | 37篇 |
数学 | 32608篇 |
物理学 | 17494篇 |
出版年
2023年 | 135篇 |
2022年 | 141篇 |
2021年 | 209篇 |
2020年 | 244篇 |
2019年 | 210篇 |
2018年 | 10581篇 |
2017年 | 10389篇 |
2016年 | 6310篇 |
2015年 | 1087篇 |
2014年 | 601篇 |
2013年 | 684篇 |
2012年 | 4234篇 |
2011年 | 11006篇 |
2010年 | 5941篇 |
2009年 | 6364篇 |
2008年 | 6927篇 |
2007年 | 9062篇 |
2006年 | 532篇 |
2005年 | 1557篇 |
2004年 | 1716篇 |
2003年 | 2132篇 |
2002年 | 1196篇 |
2001年 | 394篇 |
2000年 | 415篇 |
1999年 | 325篇 |
1998年 | 322篇 |
1997年 | 255篇 |
1996年 | 304篇 |
1995年 | 194篇 |
1994年 | 131篇 |
1993年 | 149篇 |
1992年 | 106篇 |
1991年 | 123篇 |
1990年 | 82篇 |
1989年 | 86篇 |
1988年 | 83篇 |
1987年 | 75篇 |
1986年 | 79篇 |
1985年 | 63篇 |
1984年 | 47篇 |
1983年 | 41篇 |
1982年 | 46篇 |
1981年 | 44篇 |
1980年 | 47篇 |
1979年 | 46篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
1.
High Energy Chemistry - Modification of Polyvinylidene fluoride (PVDF) by radiation grafting is a research hotspot in recent years. In this study, the monomer 2-Hydroxyethyl methacrylate (HEMA) was... 相似文献
2.
A numerical model was developed and validated to investigate the fluid–structure interactions between fully developed pipe flow and core–shell-structured microcapsule in a microchannel. Different flow rates and microcapsule shell thicknesses were considered. A sixth-order rotational symmetric distribution of von Mises stress over the microcapsule shell can be observed on the microcapsule with a thinner shell configuration, especially at higher flow rate conditions. It is also observed that when being carried along in a fully developed pipe flow, the microcapsule with a thinner shell tends to accumulate stress at a higher rate compared to that with a thicker shell. In general, for the same microcapsule configuration, higher flow velocity would induce a higher stress level over the microcapsule shell. The deformation gradient was used to capture the microcapsule's deformation in the present study. The effect of Young's modulus on the microcapsule shell on the microcapsule deformation was investigated as well. Our findings will shed light on the understanding of the stability of core–shell-structured microcapsule when subjected to flow-induced shear stress in a microfluidic system, enabling a more exquisite control over the breakup dynamics of drug-loaded microcapsule for biomedical applications. 相似文献
3.
Donglei Wei Huili Li Chuanqing Yang Jianmin Fu Hou Chen Liangjiu Bai Wenxiang Wang Huawei Yang Lixia Yang Ying Liang 《Journal of polymer science. Part A, Polymer chemistry》2022,60(10):1588-1594
Acridone as a new kind of visible light photocatalyst has been developed to catalyze metal free atom transfer radical polymerization (ATRP). The photocatalyst possess low excited state potential as can undergo an oxidative quenching pathway to initiate ATRP of vinyl monomers. Kinetic study and light on/off reaction demonstrate the “living”/controlled nature of the polymerization by light. Block copolymers can be achieved by using PMMA as macroinitiator to reinitiate polymerization of other vinyl monomers, which shows highly preserved Br chain-end functionality in the synthesized polymers. Moreover, the polymerization can be conducted under air atmosphere as most photocatalysts need anaerobic condition, which may give inspiration of further application of this kind of photocatalyst. 相似文献
4.
Wenpin Wang Qing Yao Jianhui Song Binbin Yao Hui Wang Zhibo Li 《Journal of Polymer Science.Polymer Physics》2019,57(11):662-669
The PeakForce Quantitative Nanomechanical Mapping based on atomic force microscope (AFM) is employed to first visualize and then quantify the elastic properties of a model nitrile rubber/poly(vinyl chloride) (NBR/PVC) blend at the nanoscale. This method allows us to consistently observe the changes in mechanical properties of each phase in polymer blends. Beyond measuring and discriminating elastic modulus and adhesion forces of each phase, we tune the AFM tips and the peak force parameters in order to reliably image samples. In view of viscoelastic difference in each phase, a three‐phase coexistence of an unmixed NBR phase, the mixed phase, and PVC microcrystallites is directly visualized in NBR/PVC blends. The nanomechanical investigation is also capable of recognizing the crosslinked rubber phase in cured rubber. The contribution of the mixed phase was quantified and it was found that the mechanical properties of blends are mainly determined by the homogeneity and stiffness of the mixed phase. This study furthers our understanding the structure–mechanical property relationship of thermoplastic elastomers, which is important for their potential design and applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 662–669 相似文献
5.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers. 相似文献
6.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant. 相似文献
7.
8.
Sarah Peluse 《Israel Journal of Mathematics》2018,227(1):379-396
We prove that the group of diffeomorphisms of the interval [0, 1] contains surface groups whose action on (0, 1) has no global fix point and such that only countably many points of the interval (0, 1) have non-trivial stabiliser. 相似文献
9.
10.