全文获取类型
收费全文 | 97438篇 |
免费 | 4369篇 |
国内免费 | 3512篇 |
专业分类
化学 | 38711篇 |
晶体学 | 1058篇 |
力学 | 7928篇 |
综合类 | 302篇 |
数学 | 34273篇 |
物理学 | 23047篇 |
出版年
2023年 | 363篇 |
2022年 | 456篇 |
2021年 | 625篇 |
2020年 | 881篇 |
2019年 | 866篇 |
2018年 | 11014篇 |
2017年 | 10829篇 |
2016年 | 6953篇 |
2015年 | 1866篇 |
2014年 | 1556篇 |
2013年 | 1876篇 |
2012年 | 5632篇 |
2011年 | 12415篇 |
2010年 | 7033篇 |
2009年 | 7445篇 |
2008年 | 8093篇 |
2007年 | 10032篇 |
2006年 | 1503篇 |
2005年 | 2362篇 |
2004年 | 2404篇 |
2003年 | 2613篇 |
2002年 | 1659篇 |
2001年 | 822篇 |
2000年 | 734篇 |
1999年 | 552篇 |
1998年 | 504篇 |
1997年 | 458篇 |
1996年 | 468篇 |
1995年 | 351篇 |
1994年 | 297篇 |
1993年 | 251篇 |
1992年 | 157篇 |
1991年 | 188篇 |
1990年 | 154篇 |
1989年 | 133篇 |
1988年 | 132篇 |
1987年 | 121篇 |
1986年 | 103篇 |
1985年 | 79篇 |
1984年 | 71篇 |
1983年 | 64篇 |
1982年 | 68篇 |
1981年 | 56篇 |
1980年 | 62篇 |
1979年 | 50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 156 毫秒
1.
Rui Feng Zi-Ying Li Zhao-Quan Yao Zi-Ang Guo Yi-Nan Zhang Hao-Xiang Sun Wei Li Xian-He Bu 《中国科学:化学(英文版)》2022,65(1):128-134
The rational designability and chemical tunability of metal-organic frameworks(MOFs)are enabling tributes to efficaciously enhance their room temperature phosphorescence(RTP)performance.A family of stable anionic MOFs,[Zn2(4,5-ImDC)2]M2(NKU-132,M=(CH3)2NH2or(CH2CH3)2NH2),featuring significant RTP have been synthesized.By rational cation selection and in-situ replacement from dimethylammonium to diethylammonium,the phosphorescence lifetime is increased from 30.88 to126.3 ms,along with less sensitivity to air.This work provides an anti-quenching and lifetime tuning example for RTP-MOFmaterials via facile host-guest chemistry. 相似文献
2.
Zhi Sun Mengfan Zhao Lihua Zuo Shengnan Zhou Feng Fan Qingquan Jia Lianping Xue Hanbing Li Jian Kang Xiaojian Zhang 《Journal of separation science》2022,45(2):518-528
Juglandis Mandshuricae Cortex is the bark of Juglans mandshurica Maxim., which has been used as a folk medicine plant in China and India. In this study, an ultra-high performance liquid chromatography–quadrupole/orbitrap high-resolution mass spectrometry method was developed to clarify and quantify the chemical profiling of Juglandis Mandshuricae Cortex rapidly. A total of 113 compounds were characterized. Among them, seven flavonoids were simultaneously quantified in 15 min, including myricetin, myricetrin, taxifolin, kaempferol, quercetin, quercitrin, and naringenin. The method was validated for accuracy, precision, and the limits of detection and quantification. All calibration curves showed a good linear relationship (r > 0.9990) within test ranges. The intra- and inter-day relative standard deviations were less than 2.16%. Accuracy validation showed that the recovery was between 95.6 and 101.3% with relative standard deviation values below 2.85%. The validated method was successfully applied to determine the contents of seven flavones in Juglandis Mandshuricae Cortex from seven sources and the contents of these places were calculated respectively. This method provides a theoretical basis for further developing the medicinal value of Juglandis Mandshuricae Cortex. 相似文献
3.
以过渡金属为催化衬底的化学气相沉积法(Chemical Vapor Deposition,CVD)已经可以制备与机械剥离样品相媲美的石墨烯,是实现石墨烯工业应用的关键技术之一。原子尺度理论研究能够帮助我们深刻理解石墨烯生长机理,为实验现象提供合理的解释,并有可能成为将来实验设计的理论指导。本文从理论计算的角度,总结了各种金属衬底在石墨烯CVD生长过程中的各种作用与相应的机理,包括在催化碳源裂解、降低石墨烯成核密度等,催化加快石墨烯快速生长,修复石墨烯生长过程中产生的缺陷,控制外延生长石墨烯的晶格取向,以及在降温过程中石墨烯褶皱与金属表面台阶束的形成过程等。在本文最后,我们对当前石墨烯生长领域中亟需解决的理论问题进行了深入探讨与展望。 相似文献
4.
Acta Mechanica Sinica - 相似文献
5.
6.
7.
Fuzzy Optimization and Decision Making - Data envelopment analysis (DEA) is a classical and prevailing tool for estimating relative efficiencies of multiple decision making units (DMUs). However,... 相似文献
8.
9.
Martin Obst 《Aequationes Mathematicae》2018,92(1):135-163
Measuring angles in the Euclidean plane is a well-known topic, but for general normed planes there exists a variety of different concepts. These can be of a special kind, e.g. also preserving special orthogonality types. But these concepts are no angle measures in the sense of measure theory since they are not additive. This motivates us to define a new angle measure for normed planes that is in fact a measure in the sense of measure theory. Furthermore, we look at related types of rotation and reflection. 相似文献
10.
We analyze isolated resonance curves (IRCs) in single-degree-of-freedom systems possessing nonlinear damping. Through the combination of singularity theory and the averaging method, the onset and merging of IRCs, which coincide to isola and simple bifurcation singularities, respectively, can be analytically predicted. Numerical simulations confirm the accuracy of the analytical developments. Another important finding of this paper is that we unveil a geometrical connection between the topology of the damping force and IRCs. Specifically, we demonstrate that extremas and zeros of the damping force correspond to the appearance and merging of IRCs. Considering a damping force possessing several minima and maxima confirms the general validity of the analytical result. It also evidences a very complex scenario for which different IRCs are created, co-exist and then merge together to form a super IRC which eventually merges with the main resonance peak. 相似文献