全文获取类型
收费全文 | 1059篇 |
免费 | 40篇 |
国内免费 | 13篇 |
专业分类
化学 | 722篇 |
晶体学 | 9篇 |
力学 | 30篇 |
综合类 | 5篇 |
数学 | 99篇 |
物理学 | 247篇 |
出版年
2022年 | 9篇 |
2021年 | 13篇 |
2020年 | 19篇 |
2019年 | 15篇 |
2018年 | 16篇 |
2017年 | 11篇 |
2016年 | 26篇 |
2015年 | 15篇 |
2014年 | 30篇 |
2013年 | 75篇 |
2012年 | 44篇 |
2011年 | 62篇 |
2010年 | 46篇 |
2009年 | 52篇 |
2008年 | 42篇 |
2007年 | 48篇 |
2006年 | 27篇 |
2005年 | 37篇 |
2004年 | 48篇 |
2003年 | 36篇 |
2002年 | 24篇 |
2001年 | 20篇 |
2000年 | 11篇 |
1999年 | 12篇 |
1998年 | 17篇 |
1997年 | 8篇 |
1996年 | 13篇 |
1994年 | 6篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 12篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 6篇 |
1979年 | 12篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1971年 | 6篇 |
1930年 | 7篇 |
1923年 | 14篇 |
1918年 | 14篇 |
1916年 | 5篇 |
1904年 | 5篇 |
1897年 | 12篇 |
1891年 | 11篇 |
1890年 | 5篇 |
排序方式: 共有1112条查询结果,搜索用时 15 毫秒
61.
A composite electrode was prepared by modifying glassy carbon microparticles with gold nanoparticles (Au-nps) and xanthine oxidase enzyme (XOD) for xanthine (X) and hypoxanthine (Hx) detection. After the optimization of the system for X, the biosensor was characterized for X and Hx. A linearity was obtained in the concentration range between 5.00 × 10−7 and 1.00 × 10−5 M for X with equation of y = 0.24x + 0.712 and 5.00 × 10−6 to 1.50 × 10−4 M for Hx, with equation of y = 0.014x + 0.575, respectively. Obtained results were compared to X and/or Hx biosensors including/not including Au-np in the structure. The developed system was also applied for detection of Hx in canned tuna fish sample and very promising results were obtained. 相似文献
62.
63.
Raluca Pele Gabriel Marc Anca Stana Ioana Ionu Cristina Nastas Brîndua Tiperciuc Ilioara Oniga Adrian Pîrnu Laurian Vlase Ovidiu Oniga 《Molecules (Basel, Switzerland)》2022,27(8)
Considering the important damage caused by the reactive oxygen (ROS) and nitrogen (RNS) species in the human organism, the need for new therapeutic agents, with superior efficacy to the known natural and synthetic antioxidants, is crucial. Quinazolin-4-ones are known for their wide range of biological activities, and phenolic compounds display an important antioxidant effect. Linking the two active pharmacophores may lead to an increase of the antioxidant activity. Therefore, we synthesized four series of new hybrid molecules bearing the quinazolin-4-one and phenol scaffolds. Their antioxidant potential was evaluated in vitro, considering different possible mechanisms of action: hydrogen atom transfer, ability to donate electrons and metal ions chelation. Theoretical quantum and thermodynamical calculations were also performed. Some compounds, especially the ortho diphenolic ones, exerted a stronger antioxidant effect than ascorbic acid and Trolox. 相似文献
64.
65.
The effects of cubic potentials on discrete breathers in a mixed Klein-Gordon /Fermi-Pasta-Ulam chain
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Nonlinearity has a crucial impact on the symmetry properties of dynamical
systems. This paper studies a one-dimensional mixed Klein--Gordon/Fermi--Pasta--Ulam diatomic
chain using the expanded rotating plane-wave approximation and numerical
calculations to determine the effect of cubic potentials on the symmetry
properties of discrete breathers in this system. The results will be very
useful to researchers in the field of numerical calculations on
discrete breathers. 相似文献
66.
67.
V. A. Shcherbacov A. Kh. Tabarov D. I. Puşcaşu 《Journal of Mathematical Sciences》2009,163(6):785-795
Conditions when a congruence of a left (right) division groupoid and a left (right) cancellation groupoid is closed (“normal”)
are given. Conditions for the simplicity of the above-mentioned groupoids are obtained. 相似文献
68.
Elvan Üstün Aykut Özgür Kübra A. Coşkun Serpil Demir Düşünceli İsmail Özdemir Yusuf Tutar 《Transition Metal Chemistry》2017,42(4):331-337
Carbon monoxide is an important signaling molecule which is produced by heme oxygenase-1. CO shows antiproliferative activity against cancer cells; hence, activation of HO-1 is a significant inhibition strategy against tumor formation and survival of cancer cells. In this work, manganese-based CO-releasing molecules (CORMs) were designed and synthesized to inhibit breast cancer cell proliferation. Human invasive ductal breast cancer cells (MCF-7) were treated with the synthesized CORMs to investigate the effect of the complexes on breast cancer survival under UV light. In vitro experiments indicated that the complexes inhibited breast cancer cell proliferation, and further, the antiproliferative effects were increased under UV light. Thus, these novel CORMs may provide a drug template for the treatment of invasive ductal breast cancer. 相似文献
69.
Limiting the Number of Potential Binding Modes by Introducing Symmetry into Ligands: Structure‐Based Design of Inhibitors for Trypsin‐Like Serine Proteases
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Norbert Furtmann Daniela Häußler Tamara Scheidt Dr. Marit Stirnberg Prof. Dr. Torsten Steinmetzer Prof. Dr. Jürgen Bajorath Prof. Dr. Michael Gütschow 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):610-625
In the absence of X‐ray data, the exploration of compound binding modes continues to be a challenging task. For structure‐based design, specific features of active sites in different targets play a major role in rationalizing ligand binding characteristics. For example, dibasic compounds have been reported as potent inhibitors of various trypsin‐like serine proteases, the active sites of which contain several binding pockets that can be targeted by cationic moieties. This results in several possible orientations within the active site, complicating the binding mode prediction of such compounds by docking tools. Therefore, we introduced symmetry in bi‐ and tribasic compounds to reduce conformational space in docking calculations and to simplify binding mode selection by limiting the number of possible pocket occupations. Asymmetric bisbenzamidines were used as starting points for a multistage and structure‐guided optimization. A series of 24 final compounds with either two or three benzamidine substructures was ultimately synthesized and evaluated as inhibitors of five serine proteases, leading to potent symmetric inhibitors for the pharmaceutical drug targets matriptase, matriptase‐2, thrombin and factor Xa. This study underlines the relevance of ligand symmetry for chemical biology. 相似文献
70.
Advances in wide bandgap SiC for optoelectronics 总被引:1,自引:0,他引:1
Haiyan Ou Yiyu Ou Aikaterini Argyraki Saskia Schimmel Michl Kaiser Peter Wellmann Margareta K. Linnarsson Valdas Jokubavicius Jianwu Sun Rickard Liljedahl Mikael Syväjärvi 《The European Physical Journal B - Condensed Matter and Complex Systems》2014,87(3):1-16
Silicon carbide (SiC) has played a key role in power electronics thanks to its unique physical properties like wide bandgap, high breakdown field, etc. During the past decade, SiC is also becoming more and more active in optoelectronics thanks to the progress in materials growth and nanofabrication. This paper will review the advances in fluorescent SiC for white light-emitting diodes, covering the poly-crystalline doped SiC source material growth, single crystalline epitaxy growth of fluorescent SiC, and nanofabrication of SiC to enhance the extraction efficiency for fluorescent SiC based white LEDs. 相似文献