全文获取类型
收费全文 | 2273篇 |
免费 | 350篇 |
国内免费 | 217篇 |
专业分类
化学 | 1704篇 |
晶体学 | 16篇 |
力学 | 150篇 |
综合类 | 29篇 |
数学 | 184篇 |
物理学 | 757篇 |
出版年
2024年 | 9篇 |
2023年 | 53篇 |
2022年 | 66篇 |
2021年 | 91篇 |
2020年 | 102篇 |
2019年 | 94篇 |
2018年 | 78篇 |
2017年 | 55篇 |
2016年 | 109篇 |
2015年 | 114篇 |
2014年 | 106篇 |
2013年 | 148篇 |
2012年 | 190篇 |
2011年 | 204篇 |
2010年 | 122篇 |
2009年 | 112篇 |
2008年 | 156篇 |
2007年 | 137篇 |
2006年 | 121篇 |
2005年 | 127篇 |
2004年 | 73篇 |
2003年 | 56篇 |
2002年 | 59篇 |
2001年 | 51篇 |
2000年 | 51篇 |
1999年 | 47篇 |
1998年 | 38篇 |
1997年 | 35篇 |
1996年 | 30篇 |
1995年 | 29篇 |
1994年 | 31篇 |
1993年 | 22篇 |
1992年 | 18篇 |
1991年 | 28篇 |
1990年 | 18篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 8篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1959年 | 1篇 |
1947年 | 1篇 |
1946年 | 1篇 |
排序方式: 共有2840条查询结果,搜索用时 46 毫秒
71.
Microemulsions are important organized molecular assembles in surfactant solutions and are used in various fields such as tertiary oil recovery, pharmaceutics, cosmetics, nanoparticle synthe-sis and chemical engineering. The more commonly used nonionic surfactants to produce micro- emulsions are the ethylene oxide-based compounds (CiEj). In recent years alkyl polyglucosides have been received considerable attention in producing microemulsions[17]. Alkyl polyglucosides (APG), which are widely… 相似文献
72.
本文用X射线衍射及差热分析等方法, 研究了BaO-B_2O_3-GeO_2(BaO≤50 mol%)三元系的室温截面相图。发现了一个新的三元化合物Ba_3B_6Ge_2O_(16)(3BaO·3B_2O_3·2GeO_2)。并且研究了BaB_2O_4-Ba_3B_6Ge_2O_(16), BaGeO_3-Ba_3B_6Ge_2O_(16), BaB_2O_4-BaGeO_3三个二元系相图。它们都是共晶体系, 共晶温度分别为937±3 ℃、879±3 ℃875±3 ℃; 共晶组分分别为(BaO)_(0.42)(B_2O_3)_(0.42)(GeO_2)_(0.16), (BaO)_(0.42)(B_2O_3)_(0.24)(GeO_2)_(0.34), (BaO)_(0.50)(B_2O_3)_(0.27)(GeO_2)_(0.23)。这三个二元系组成一个三元共晶体系, 其三元共晶温度为870±3 ℃, 共晶组分为(BaO)_(0.46)(B_2O_3)_(0.27)(GeO_2)_(0.27)。 相似文献
73.
74.
Chen J.-J. Huang P.-Y. Yang Z.-S. Cai X.-Z. Shi Y. Hu W.-Y. Zhang X.-H. Chai H.-F. Huang Z.-Y. 《Journal of Structural Chemistry》2021,62(10):1543-1550
Journal of Structural Chemistry - N-(2-methoxy-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridin-3-yl)cyclopropanesulfonamide is an organic intermediate with borate and sulfonamide groups,... 相似文献
75.
Masoud Behzad Karel Samec Sang-In Bak Yacine Kadi Claudio Tenreiro Seung-Woo Hong Jong-Seo Chai 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(2):1001-1006
A worldwide challenge in the near future will be to find a way of producing radioisotopes in sufficient quantity without relying on research reactors. The motivation for this innovative work on targets lies in the accelerator-based production of radioisotopes using a neutron converter target as in the transmutation by adiabatic resonance crossing concept. Thermal analysis of a multi-channel helium cooled device is performed with the computational fluid dynamics code CFX. Different boundary conditions are taken into account in the simulation process and many important parameters such as maximum allowable solid target temperature as well as uniform inlet velocity and outlet pressure changes in the channels are investigated. The results confirm that the cooling configuration works well; hence such a solid target could be operated safely and may be considered for a prototype target. 相似文献
76.
Zhong Lvling Li Baolin Zhang Liang Ma Xinjie Chai Shouning 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2018,92(4):785-792
Russian Journal of Physical Chemistry A - A new mesoporous carbon containing nitrogen and copper was prepared by carbonizing a polymer obtained by blending p-phenylenediamine, copper(II) sulfate,... 相似文献
77.
The aim of this paper is to study the exact controllability of the Petrovsky equation. Under some checkable geometric assumptions, we establish the observability inequality via the multiplier method for the Dirichlet control problem. 相似文献
78.
Dr. Ze-Jie Lv Wei Liu Miaomiao Zhu Zhengqi Chai Junnian Wei Prof. Wen-Xiong Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(66):16498-16504
Although the reaction chemistry of transition metallacyclopropenes has been well-established in the last decades, the reactivity of rare-earth metallacyclopropenes remains elusive. Herein, we report the reaction of lutetacyclopropene 1 toward a series of unsaturated molecules. The reaction of 1 with one equiv. of PhCOMe, Ar1CHO (Ar1=2,6-Me2C6H3), W(CO)6, and PhCH=NPh provided oxalutetacyclopentenes, metallacyclic lutetoxycarbene, and azalutetacyclopentene via 1,2-insertion of C=O, C≡O, or C=N bonds into Lu−Csp2 bond, respectively. However, the reaction between 1 and Ar2N=C=NAr2 (Ar2=4-MeC6H4) gave an acyclic lutetium complex with a diamidinate ligand by the coupling of one molecule of 1 with two carbodiimides, irrespective of the amount of carbodiimide employed. More interestingly, when 1 was treated with two equiv. of Ar1CHO, the reductive coupling of two C=O bonds was discovered to give a lutetium pinacolate complex along with the release of tolan. Remarkably, the reactivity of 1 is significantly different from that of scandacyclopropenes; these metallacycles derived from 1 all represent the first cases in rare-earth organometallic chemistry. 相似文献
79.
Synthesis and rheological investigation of self‐healable deferoxamine grafted alginate hydrogel
下载免费PDF全文
![点击此处可从《Journal of Polymer Science.Polymer Physics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Guanzhe Xu Yan Xiao Liang Cheng Runhua Zhou Heng Xu Yimin Chai Meidong Lang 《Journal of Polymer Science.Polymer Physics》2017,55(11):856-865
Deferoxamine grafted alginate (SA‐DFA) was successfully synthesized via amidation of sodium alginate with deferoxamine mesylate as determined by H‐NMR and elemental analysis. SA‐DFA with different graft yield was obtained by adjusting the ratio of sodium alginate and deferoxamine mesylate. It was found that aqueous solution of SA‐DFA could form hydrogel spontaneously due to hydrogen bonding interactions, which also endowed the SA‐DFA hydrogel with self‐healing capability. The healing efficiency of SA‐DFA hydrogels ranged from 53.64 to 90.16%. In addition, surface morphologies of SA‐DFA hydrogels before/after self‐healing process were demonstrated by SEM images. We anticipated that such self‐healable alginate hydrogel would be applied in the field of wound healing. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 856–865 相似文献
80.
A practical eight-step synthesis of lignanamide cannabisin F starting from vanillin is reported for the first time. This synthetic strategy applies the aldol reaction followed by the Wittig reaction to afford the key 8-O-4′-neolignan intermediate diacid. The diacid was condensed with N,O-protected tyramine giving, after deprotection, cannabisin F. 相似文献