全文获取类型
收费全文 | 625424篇 |
免费 | 26255篇 |
国内免费 | 16697篇 |
专业分类
化学 | 304212篇 |
晶体学 | 7551篇 |
力学 | 24518篇 |
综合类 | 679篇 |
数学 | 62381篇 |
物理学 | 171277篇 |
无线电 | 97758篇 |
出版年
2022年 | 7078篇 |
2021年 | 9172篇 |
2020年 | 9752篇 |
2019年 | 9602篇 |
2018年 | 10744篇 |
2017年 | 10314篇 |
2016年 | 15306篇 |
2015年 | 12036篇 |
2014年 | 16818篇 |
2013年 | 31060篇 |
2012年 | 27547篇 |
2011年 | 31484篇 |
2010年 | 22974篇 |
2009年 | 23472篇 |
2008年 | 28414篇 |
2007年 | 27945篇 |
2006年 | 26224篇 |
2005年 | 23661篇 |
2004年 | 20701篇 |
2003年 | 18245篇 |
2002年 | 17560篇 |
2001年 | 18712篇 |
2000年 | 15061篇 |
1999年 | 12866篇 |
1998年 | 11041篇 |
1997年 | 10373篇 |
1996年 | 10049篇 |
1995年 | 9053篇 |
1994年 | 8671篇 |
1993年 | 8042篇 |
1992年 | 8519篇 |
1991年 | 8441篇 |
1990年 | 7911篇 |
1989年 | 7354篇 |
1988年 | 7055篇 |
1987年 | 6362篇 |
1986年 | 6022篇 |
1985年 | 7472篇 |
1984年 | 7475篇 |
1983年 | 6001篇 |
1982年 | 5939篇 |
1981年 | 5875篇 |
1980年 | 5399篇 |
1979年 | 5685篇 |
1978年 | 5811篇 |
1977年 | 5693篇 |
1976年 | 5585篇 |
1975年 | 5161篇 |
1974年 | 5115篇 |
1973年 | 5131篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Revin A. A. Mikhaylova A. M. Konakov A. A. Tsyplenkov V. V. Shastin V. N. 《Semiconductors》2021,55(12):879-884
Semiconductors - The wave functions of electrons localized at P, As, and Sb shallow donors in Ge are calculated in the envelope function approximation taking into account valley–orbit... 相似文献
63.
Russian Chemical Bulletin - The N-methylation of primary carboxamides is based on two consecutive reactions. The silylation of the corresponding carboxamides with chloro(chloromethyl)dimethylsilane... 相似文献
64.
Li Jun Zheng Dayong Wei Ning Sun Yunfeng Liu Li Yuan Yuan Jiang Qinghua 《Chemistry of Natural Compounds》2022,58(4):650-652
Chemistry of Natural Compounds - A new quassinoid, dehydrobruceantinol B (1), was isolated from the seeds of Brucea javanica, together with two known compounds, bruceantinol (2) and bruceine A (3).... 相似文献
65.
随着计算机技术以及并行求解技术的发展,区域分解方法越来越多地应用于计算电磁学的各个领域.针对微波管中的永磁聚焦系统仿真,该文提出一种基于有限元的非重叠区域分解方法,其引入一种新型传输条件,并采用内罚的方式推导出有限元弱形式.该区域分解法的最大优势是不需要引入多余的未知量,并且最终集成的有限元矩阵满足对称正定性,适合采用预处理共轭梯度法进行矩阵方程的求解.该文仿真了多个微波管永磁聚焦系统,并与商业软件Maxwell进行了详细的对比,结果表明所提出的区域分解方法和Maxwell精度相当,却拥有着更加优越的计算性能. 相似文献
66.
Crystallography Reports - Electron backscattered diffraction (EBSD) has been used to analyze structures of natural minerals and artificial compounds for almost three decades. In recent years, it is... 相似文献
67.
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
68.
Lili Hao Jiaxiang Li Peng Wang Zongliang Wang Zhenxu Wu Yu Wang Zixue Jiao Min Guo Tongfei Shi Qigang Wang Yoshihiro Ito Yen Wei Peibiao Zhang 《Advanced functional materials》2021,31(15):2009661
The degradation behavior of implants is significantly important for bone repair. However, it is still unprocurable to spatiotemporally regulate the degradation of the implants to match bone ingrowth. In this paper, a magneto-controlled biodegradation model is established to explore the degradation behavior of magnetic scaffolds in a magnetothermal microenvironment generated by an alternating magnetic field (AMF). The results demonstrate that the scaffolds can be heated by magnetic nanoparticles (NPs) under AMF, which dramatically accelerated scaffold degradation. Especially, magnetic NPs modified by oleic acid with a better interface compatibility exhibit a greater heating efficiency to further facilitate the degradation. Furthermore, the molecular dynamics simulations reveal that the enhanced motion correlation between magnetic NPs and polymer matrix can accelerate the energy transfer. As a proof-of-concept, the feasibility of magneto-controlled degradation for implants is demonstrated, and an optimizing strategy for better heating efficiency of nanomaterials is provided, which may have great instructive significance for clinical medicine. 相似文献
69.
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
70.
Chueshova A. G. Pavlova L. A. Peshcherova S. M. Nepomnyashchikh A. I. 《Crystallography Reports》2021,66(7):1206-1215
Crystallography Reports - The orientation of grains and the special boundaries formed by them in multicrystalline silicon has been studied by electron backscattered diffraction. It is found that... 相似文献