全文获取类型
收费全文 | 86103篇 |
免费 | 6446篇 |
国内免费 | 3476篇 |
专业分类
化学 | 47341篇 |
晶体学 | 1117篇 |
力学 | 4864篇 |
综合类 | 144篇 |
数学 | 7530篇 |
物理学 | 35029篇 |
出版年
2023年 | 776篇 |
2022年 | 1121篇 |
2021年 | 1469篇 |
2020年 | 1791篇 |
2019年 | 1755篇 |
2018年 | 1679篇 |
2017年 | 1481篇 |
2016年 | 2410篇 |
2015年 | 2056篇 |
2014年 | 2823篇 |
2013年 | 4746篇 |
2012年 | 5040篇 |
2011年 | 5753篇 |
2010年 | 3889篇 |
2009年 | 3872篇 |
2008年 | 4655篇 |
2007年 | 4243篇 |
2006年 | 4003篇 |
2005年 | 3368篇 |
2004年 | 2879篇 |
2003年 | 2439篇 |
2002年 | 2236篇 |
2001年 | 3467篇 |
2000年 | 2473篇 |
1999年 | 2020篇 |
1998年 | 1500篇 |
1997年 | 1455篇 |
1996年 | 1280篇 |
1995年 | 1182篇 |
1994年 | 1030篇 |
1993年 | 873篇 |
1992年 | 1204篇 |
1991年 | 1142篇 |
1990年 | 1024篇 |
1989年 | 876篇 |
1988年 | 814篇 |
1987年 | 867篇 |
1986年 | 748篇 |
1985年 | 945篇 |
1984年 | 855篇 |
1983年 | 602篇 |
1982年 | 584篇 |
1981年 | 553篇 |
1980年 | 500篇 |
1979年 | 619篇 |
1978年 | 644篇 |
1977年 | 658篇 |
1976年 | 573篇 |
1975年 | 481篇 |
1974年 | 521篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
1.
Circularly polarized luminescence (CPL) has attracted attention as a next-generation light signal because of its carrying more information compared with normal and linearly polarized lights as well as its potential wide application in information fields. Recently, much attention has been paid to small organic molecules-based CPL emitters because of easy synthesis, fine structural modification at molecular level, and tunable wide range emission wavelength. This review highlights the development of small organic molecules-based CPL emitters in the past 5 years (2017–2021). The progress suggests that small organic molecules-based CPL emitters provide a simple and efficient way to generate CPL. 相似文献
2.
Journal of Applied Spectroscopy - The concentration of heavy metals in drinking water is an important standard for water quality evaluation and water pipeline corrosion detection. This research... 相似文献
3.
4.
Xin Liu Lili Chen Yanfeng Zhao Xianhua Song 《Mathematical Methods in the Applied Sciences》2022,45(1):77-92
In this paper, the problem of the uniform stability for a class of fuzzy fractional-order genetic regulatory networks with random discrete delays, distributed delays, and parameter uncertainties is studied. Although there is a portion of literature on using fixed point theorems to study the stability of fractional neural networks, most of them required the fractional order to be in . However, the case of the fractional-order belonging to has not been discussed. To solve it, this work proposes a novel idea of using fixed point theory to study the stability of fuzzy (0,1) order neural networks, the problem of the uniqueness of the solution of the considered genetic regulatory networks is resolved, and a novel sufficient condition to guarantee the uniform stability of above genetic regulatory networks is also derived. Eventually, an example is given to demonstrate that the obtained result is effective. 相似文献
5.
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
6.
Numerical Algorithms - An inverse central ordering of the nodes is proposed for the Newton interpolation formula. This ordering may improve the stability for certain distributions of nodes. For... 相似文献
7.
8.
Theoretical and Mathematical Physics - By introducing shift relations satisfied by a matrix $$\boldsymbol{r}$$ , we propose a generalized Cauchy matrix scheme and construct a discrete second-order... 相似文献
9.
10.
BIT Numerical Mathematics - In this paper, we introduce a novel class of embedded exponential-type low-regularity integrators (ELRIs) for solving the KdV equation and establish their optimal... 相似文献