全文获取类型
收费全文 | 17125篇 |
免费 | 3163篇 |
国内免费 | 2062篇 |
专业分类
化学 | 12354篇 |
晶体学 | 167篇 |
力学 | 1020篇 |
综合类 | 103篇 |
数学 | 1812篇 |
物理学 | 6894篇 |
出版年
2024年 | 18篇 |
2023年 | 398篇 |
2022年 | 365篇 |
2021年 | 575篇 |
2020年 | 736篇 |
2019年 | 715篇 |
2018年 | 632篇 |
2017年 | 569篇 |
2016年 | 856篇 |
2015年 | 824篇 |
2014年 | 993篇 |
2013年 | 1265篇 |
2012年 | 1586篇 |
2011年 | 1522篇 |
2010年 | 1058篇 |
2009年 | 988篇 |
2008年 | 1096篇 |
2007年 | 1023篇 |
2006年 | 941篇 |
2005年 | 849篇 |
2004年 | 606篇 |
2003年 | 508篇 |
2002年 | 483篇 |
2001年 | 386篇 |
2000年 | 346篇 |
1999年 | 404篇 |
1998年 | 340篇 |
1997年 | 330篇 |
1996年 | 306篇 |
1995年 | 269篇 |
1994年 | 222篇 |
1993年 | 198篇 |
1992年 | 152篇 |
1991年 | 134篇 |
1990年 | 154篇 |
1989年 | 111篇 |
1988年 | 75篇 |
1987年 | 52篇 |
1986年 | 59篇 |
1985年 | 60篇 |
1984年 | 29篇 |
1983年 | 30篇 |
1982年 | 31篇 |
1981年 | 20篇 |
1980年 | 11篇 |
1977年 | 3篇 |
1957年 | 2篇 |
1942年 | 2篇 |
1930年 | 2篇 |
1916年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
35.
Imine Macrocycle with a Deep Cavity: Guest‐Selected Formation of syn/anti Configuration and Guest‐Controlled Reconfiguration 下载免费PDF全文
Dr. Zhenfeng He Gang Ye Dr. Wei Jiang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(7):3005-3012
A dynamic covalent bond is one of the ideal linkages for the construction of large and robust organic architectures. In the present article, we show how organic templates can efficiently transform a complex dynamic imine library into a dynamic imine macrocycle. Not only is the constitution well controlled, but also the syn/anti host configuration is efficiently selected and even the orientation of the guest in the asymmetric cavity of the host can be well aligned. This is attributed to the delicate balance and the cooperation of multiple noncovalent interactions between the hosts and the guests. Through sequential additions of three guests in appropriate amounts, controlled structural reconfiguration of dynamic covalent architectures has been achieved for the first time. 相似文献
36.
37.
一维非共轭烷烃链虽不具富电子或少电子特征,但常存在于单分子器件或多肽、蛋白质等生物分子中,对电子传输产生重要影响.为理解这类物质的电子输运特征,本研究设计了一维线性非共轭(CH2)n分子结模型,并利用密度泛函理论结合非平衡态格林函数的方法,对(CH2)n(n=1-12)线性分子链与两个石墨烯电极耦合而成的分子结进行了第一性原理计算.结果表明,CH2分子链随着n值的变化,其电导值表现出明显的奇偶振荡现象,并且随着链长的增加呈指数级的衰减,这一结果与实验研究取得了很好的一致性,为理解和设计性能更加优良的单分子器件提供了重要理论依据. 相似文献
38.
Li‐Ming Sun Bo Zhang Yu‐Chen Wang Hao‐Ke He Xiao‐Guang Chen Su‐Juan Wang 《Biomedical chromatography : BMC》2019,33(2)
Alum‐processing is a traditional method to attenuate the toxicity of Pinelliae Rhizoma (tubers of Pinellia ternate, PT). The present study aimed at investigating the chemical and cytotoxic changes during alum processing. Metabolomic profiles of raw and alum‐processed PT were studied based on ultra‐performance liquid chromatography coupled with Orbitrap mass spectrometry. More than 80 chemicals in positive MS mode and 40 chemicals in negative MS mode, such as organic acids, amino acids, glucosides and nucleosides, were identified after multivariate statistical analysis, including principal component analysis and orthogonal partial least‐square discriminant analysis. Almost all of the identified chemical markers were significantly decreased ~10‐ to 100‐fold after alum processing. Meanwhile, the correlations between the chemical markers were assimilated to a positive coefficient from disorderly distribution during the processing. Raw PT extracts could inhibit the proliferation of human carcinoma cells (HCT‐116, HepG2, and A549) at the rate of 40.5, 24.8 and 31.6% more strongly than processed PT. It was concluded that the alum processing of PT could decrease the number of actively water‐soluble principles at the same time as decreasing toxicity. Given the water‐insoluble property of toxic calcium oxalate raphides in PT, we suggest that a more scientific processing method should be sought. 相似文献
39.
Dr. Lei He Prof. Wen-Cui Li Shuang Xu Prof. An-Hui Lu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(13):3209-3218
Microporous carbons afford high surface areas, large pore volumes, and good conductivity, and are fascinating over a wide range of applications. Traditionally synthesized microporous carbon materials usually suffer from some limitations, such as poor accessibility and slow mass transport of molecules due to the micrometer-scale diffusion pathways and space confinement imposed by small pore sizes. Two-dimensional microporous carbon materials, denoted as microporous carbon nanosheets (MCNs), possess nanoscale thickness, which allows fast mass and heat transport along the z axis; thus overcoming the drawbacks of their bulk counterparts. Herein, recent breakthroughs in the synthetic strategies for MCNs are summarized. Three typical methods are discussed in detail with several examples: pyrolysis of organic precursors with 2D units, a templating method that uses wet chemistry, and the molten salt method. Among them, molecular-based assembly of MCNs in the liquid phase shows more controllable morphology, thickness, and pore size distribution. Finally, challenges in this research area are discussed to inspire future explorations. 相似文献
40.
Jinhua Gao Yuanfang Tao Dr. Jian Zhang Nannan Wang Xin Ji Dr. Jinling He Prof. Yubing Si Prof. Weili Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(48):11246-11256
Our previous discovery suggested that substituents on the 1,7 positions delicately modulate the sensing ability of the meso-arylmercapto boron-dipyrromethene (BODIPY) to biothiols. In this work, the impact of delicate modulations on the sensing ability is investigated. Therefore, 1,7-dimethyl, 3,5-diaryl substituted BODIPY is designed and developed and its conformationally restricted species with a meso-arylmercapto moiety ( DM-BDP-SAr and DM-BDP-R-SAr ) as selective fluorescent probes for Cys. Moreover, the lysosome-target probes ( Lyso-S and Lyso-D ) based on DM-BDP-SAr carrying one or two morpholinoethoxy moieties were developed. They were able to detect Cys selectively in vitro with low detection limits. Both Lyso-S and Lyso-D localized nicely in lysosomes in living HeLa cells and exhibited red fluorescence for Cys. Moreover, a novel fluorescence quenching mechanism was proposed from the calculations by density functional theory (DFT). The probes may go through intersystem crossing (from singlet excited state to triplet excited state) to result in fluorescence quenching. 相似文献