全文获取类型
收费全文 | 7501篇 |
免费 | 1546篇 |
国内免费 | 946篇 |
专业分类
化学 | 5441篇 |
晶体学 | 172篇 |
力学 | 502篇 |
综合类 | 112篇 |
数学 | 697篇 |
物理学 | 3069篇 |
出版年
2024年 | 38篇 |
2023年 | 187篇 |
2022年 | 320篇 |
2021年 | 345篇 |
2020年 | 461篇 |
2019年 | 395篇 |
2018年 | 339篇 |
2017年 | 323篇 |
2016年 | 480篇 |
2015年 | 528篇 |
2014年 | 563篇 |
2013年 | 704篇 |
2012年 | 746篇 |
2011年 | 736篇 |
2010年 | 514篇 |
2009年 | 431篇 |
2008年 | 446篇 |
2007年 | 398篇 |
2006年 | 313篇 |
2005年 | 304篇 |
2004年 | 230篇 |
2003年 | 188篇 |
2002年 | 195篇 |
2001年 | 150篇 |
2000年 | 86篇 |
1999年 | 74篇 |
1998年 | 58篇 |
1997年 | 40篇 |
1996年 | 38篇 |
1995年 | 18篇 |
1994年 | 26篇 |
1993年 | 25篇 |
1992年 | 28篇 |
1991年 | 19篇 |
1990年 | 26篇 |
1989年 | 17篇 |
1988年 | 17篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 15篇 |
1984年 | 14篇 |
1983年 | 19篇 |
1982年 | 12篇 |
1981年 | 16篇 |
1980年 | 12篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1974年 | 9篇 |
1973年 | 5篇 |
排序方式: 共有9993条查询结果,搜索用时 15 毫秒
41.
A new simple and rapid electrochemical method for the determination of hydroxyl radical generated by Fenton reaction and its application 总被引:3,自引:0,他引:3
A simple and rapid electrochemical method to detect the hydroxyl radical is described. This method employed the reaction between.OH and dimethyl sulfoxide (DMSO) to generate quantitatively formaldehyde, which then reacted with hydrazine hydrochloride at pH 6.2. The product showed a second-order derivative cathodic wave with the peak potential of -1.08 V( vsSCE) by single sweep oscillopolarography. The electrochemical behavior of the product was investigated by single sweep oscillopolarography and cyclic voltammetry. The experimental conditions for the measurement were optimized and the scavenging activity of some flavonoids on hydroxyl radicals was studied. 相似文献
42.
43.
JIN Hua QI Yan-fei QIN Chao WANG Xin-long WANG En-bo ** XU Lin Institute of Polyoxometalate Chemistry Faculty of Chemistry Northeast Normal University Changchun P. R. China 《高等学校化学研究》2005,(6)
IntroductionPolyoxometalates(POMs),as an important familyof metal oxides,have been receiving considerable at-tention in solid-state materials chemistry due to their di-verse topological properties and potential applications incatalysis,photochemistry,electrochemistry,medicineand magnetism[1,2].Recently,one of the intriguingfields in the polyoxometalate chemistry is to find somenovel subunits and then connect them into one-,two-,even three-dimensional(1-,2-,even3-D)extendednetworks,either thro… 相似文献
44.
用ATRP法构筑核壳型梯度极性的多羟基多臂星状超支化聚合物及聚合物刷——双层聚合物刷的合成与表征 总被引:3,自引:0,他引:3
设计并通过原子转移自由基聚合方法 (ATRP)合成了核壳型多羟基多臂星状超支化聚合物刷 .以 2 溴异丁基酰溴封端的超支化聚 (3 乙基 3 羟甲基氧杂环丁烷 ) (HP Br)作为大分子引发剂 ,采用Cu(I)Br和N ,N ,N′ ,N′ ,N″ 五甲基二乙基三胺 (PMDETA)催化体系 ,在丁酮与丙醇的混和溶液中 ,通过甲基丙烯酸羟乙酯(HEMA)的ATRP溶液聚合 ,得到了一系列含有大量羟基的多臂星状超支化聚合物刷 (HP g PHEMA) ,并考察了其羟基的活性 ,发现羟基还可以与苯甲酰氯发生反应 .产物的结构和热性能用1 H NMR、FTIR、GPC、TGA、DSC等进行了表征和测试 . 相似文献
45.
Chao Wang Jing Wang Xiang Xiao Guobin Zhong Shijia Wu Kaiqi Xu Wei Zhao Wei Su Jie Zeng Baojun Wu Weili Zhang Changcheng Wu Zhiqiang Shi 《中国化学快报》2019,30(6):1269-1272
A novel cyclic ammonium salt, N,N-dimethylpyrrolidinium tetrafluoroborate (P11-BF4), was successfully synthesized for the first time. The smallest cyclic structure of P11-BF4 induced high solubility and conductivity in PC, which can easier enter the micropores of activated carbon and occupy more surface area during charge/discharge process. 相似文献
46.
A series of methacrylamide-based C16 monolithic columns were prepared and characterized to determine how their porous structural properties and chromatographic behavior are affected by the percentages of functional monomer, base monomer, and cross-linker in the polymerization solution. Baseline separation of 6 neutral compounds can be readily obtained in an optimized column. Furthermore, the effects of organic additive in the mobile phase, operating voltages, and temperature on retention behaviors and separation efficiencies were also studied. The separation mechanism is also discussed. High column efficiency and good reproducibility indicate that the monolithic columns hold considerable promise. 相似文献
47.
48.
In this study, we report the design and synthesis of a series of new simplified fumitremorgin C analogues. The preliminary biological study indicated some of these simplified fumitremorgin C might be developed into breast cancer resistance inhibitors. 相似文献
49.
Lei Qiao Chao Zhang Xiang‐Wen Zhang Zi‐Chuan Wang Haolin Yin Zhong‐Ming Sun 《中国化学》2020,38(3):295-304
The polypnictide complexes of rare earth cations have drawn the attention of the scientific community for their uncommon bonding modes and potential applications. Herein, we present a systematic and comprehensive summary on recent advances in the field of rare earth polypnictides, focusing on their synthesis, structures, and reactivities. The structural stabilizing effects imposed by the electropositive rare earth cations as well as the reducing capability of rare earth precursors in the synthesis of these polypnictide complexes are described in this review. We also disscuss in detail the bonding interactions and coordination modes between rare earth cations and polypnictide clusters as well as the similarities and the peculiarity of some structures. 相似文献
50.
胺、醇、醚类化合物电离能的自相关拓扑研究 总被引:1,自引:3,他引:1
原子的染色序数 fi 定义为 :fi=gi·xi,式中 gi 为原子i在分子中的序数 ,xi 为其染色系数 .基于fi 建立改进的原子序数自相关拓扑指数mF ,其中的1F对烷烃及其衍生物具有良好的结构选择性 .使用第一电离能 (Ip)与0 F ,1F的数量关系模型对 32种脂肪族胺、醇、醚进行估算、预测 ,结果令人满意 相似文献