全文获取类型
收费全文 | 615466篇 |
免费 | 21762篇 |
国内免费 | 13339篇 |
专业分类
化学 | 326784篇 |
晶体学 | 9520篇 |
力学 | 31034篇 |
综合类 | 678篇 |
数学 | 79985篇 |
物理学 | 202566篇 |
出版年
2022年 | 5790篇 |
2021年 | 6417篇 |
2020年 | 7158篇 |
2019年 | 7188篇 |
2018年 | 15350篇 |
2017年 | 15678篇 |
2016年 | 14775篇 |
2015年 | 9836篇 |
2014年 | 12671篇 |
2013年 | 26177篇 |
2012年 | 25693篇 |
2011年 | 35967篇 |
2010年 | 24115篇 |
2009年 | 23848篇 |
2008年 | 30481篇 |
2007年 | 32703篇 |
2006年 | 19792篇 |
2005年 | 23397篇 |
2004年 | 18479篇 |
2003年 | 16430篇 |
2002年 | 14279篇 |
2001年 | 15511篇 |
2000年 | 12196篇 |
1999年 | 9958篇 |
1998年 | 8159篇 |
1997年 | 7899篇 |
1996年 | 7737篇 |
1995年 | 7047篇 |
1994年 | 6715篇 |
1993年 | 6408篇 |
1992年 | 7010篇 |
1991年 | 6945篇 |
1990年 | 6497篇 |
1989年 | 6284篇 |
1988年 | 6143篇 |
1987年 | 6036篇 |
1986年 | 5681篇 |
1985年 | 7462篇 |
1984年 | 7564篇 |
1983年 | 6140篇 |
1982年 | 6366篇 |
1981年 | 6244篇 |
1980年 | 6019篇 |
1979年 | 6345篇 |
1978年 | 6726篇 |
1977年 | 6384篇 |
1976年 | 6388篇 |
1975年 | 5894篇 |
1974年 | 5914篇 |
1973年 | 5914篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Xu Mengtao Li Changyou Sun Yang Yang Tianzhi Zhang Hongzhuang Liu Zhendong Liu Haiyang Li Zhenyuan Zhang Yimin 《Nonlinear dynamics》2021,105(4):3061-3092
Nonlinear Dynamics - Investigation of the dynamic characteristics of linear guideway is essential for enhancing structural performance of machine tools. However, few mechanical models are... 相似文献
52.
53.
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
54.
Crystallography Reports - Some questions related to the establishment, development, and prospects of physical studies using inelastic thermal-neutron scattering are briefly reviewed. The directions... 相似文献
55.
Avrutskiy V. I. Ishkhanyan A. M. Krainov V. P. 《Theoretical and Mathematical Physics》2021,208(3):1201-1206
Theoretical and Mathematical Physics - The fractional derivative method is used to take wave dispersion into account in the wave equation when describing the propagation of gravitational soliton... 相似文献
56.
Herein, we successfully construct the 3D biocompatible graphene through crosslinking 2D graphene nanosheet onto carbon fiber paper with poly(diallyldimethylammonium chloride) (PDDA) as anode of the alcohol biofuel cell. Compared with the bioanode without 3D graphene, the current density and output power of PDDA-graphene-ADH bioanode is increased by 23 % and 41 % at a high concentration of ethanol at pH 8.9, suggesting the stabilization role of graphene in enzyme loading. The study provides us a deep analysis on structures and performances of the bioanode incl. electrochemistry, X-ray photoelectron spectra, and atomic force microscopy images, which is significant to develop the new methods to construct 3D porous electrodes in energy conversion device. 相似文献
57.
S. Venkatesan S. Suresh P. Ramu M. Kandasamy J. Arumugam S. Thambidurai K.M. Prabu N. Pugazhenthiran 《印度化学会志》2022,99(5):100436
A facile biosynthesis route was followed to prepare zinc oxide nanoparticles (ZnO NPs) using Euphorbia milii (E. milii) leaf constituents. The SEM images exhibited presence of spherical ZnO NPs and the corresponding TEM images disclosed monodisperse nature of the ZnO NPs with diameter ranges between 12 and 20 nm. The Brunauer–Emmett–Teller (BET) analysis revealed that the ZnO NPs have specific surface area of 20.46 m2/g with pore diameter of 2 nm–10 nm and pore volume of 0.908 cm3/g. The EDAX spectrum exemplified the existence of Zn and O elements and non-appearance of impurities that confirmed pristine nature of the ZnO NPs. The XRD pattern indicated crystalline peaks corresponding to hexagonal wurtzite structured ZnO with an average crystallite size of 16.11 nm. The FTIR spectrum displayed strong absorption bands at 512 and 534 cm?1 related to ZnO. The photocatalytic action of ZnO NPs exhibited noteworthy degradation of methylene blue dye under natural sunlight illumination. The maximum degradation efficiency achieved was 98.17% at an illumination period of 50 min. The reusability study proved considerable photostability of the ZnO NPs during photocatalytic experiments. These findings suggest that the E. milii leaf constituents can be utilized as suitable biological source to synthesis ZnO NPs for photocatalytic applications. 相似文献
58.
Crystallography Reports - Methods of coherent X-ray diffraction imaging of the spatial structure of noncrystalline objects and nanocrystals (nanostructures) are considered. Particular attention is... 相似文献
59.
Nonlinear Dynamics - This paper investigates the guaranteed cost positive consensus for linear multi-agent systems (MASs) with multiple time-varying delays and switching topologies. First,... 相似文献
60.
Nonlinear Dynamics - Epilepsy is the second largest neurological disease which seriously threatens human life and health. The one important reason of inducing epileptic seizures is ischemic stroke... 相似文献