全文获取类型
收费全文 | 543篇 |
免费 | 17篇 |
国内免费 | 1篇 |
专业分类
化学 | 358篇 |
晶体学 | 8篇 |
力学 | 25篇 |
数学 | 57篇 |
物理学 | 113篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 15篇 |
2021年 | 16篇 |
2020年 | 23篇 |
2019年 | 19篇 |
2018年 | 16篇 |
2017年 | 24篇 |
2016年 | 31篇 |
2015年 | 15篇 |
2014年 | 27篇 |
2013年 | 48篇 |
2012年 | 40篇 |
2011年 | 53篇 |
2010年 | 17篇 |
2009年 | 20篇 |
2008年 | 28篇 |
2007年 | 26篇 |
2006年 | 31篇 |
2005年 | 21篇 |
2004年 | 24篇 |
2003年 | 13篇 |
2002年 | 9篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1981年 | 3篇 |
排序方式: 共有561条查询结果,搜索用时 218 毫秒
141.
142.
Pankaj Kumar Gaurav 《Phase Transitions》2013,86(3):312-324
The compound 4-methyl (2′-hydroxy,4′-n-hexadecyloxy) azobenzene was synthesized by Prajapati and co-workers (Mol. Cryst. Liq. Cryst. 369 (2001), pp. 37–46). Subsequent experiments (D. Pal, [PhD thesis], University of Lucknow, Lucknow, India, 2007) confirmed that the compound exists in nematic phase for a small range of temperature (72°C–80°C). In the present work, optimization of molecular geometry has been carried out by employing the Gaussian 03 suit of programs without any constraint using density functional B3LYP along with 6-31G** basis set and checked for imaginary frequencies. A detailed investigation on intermolecular interaction energy at various interacting configurations has been carried out. In order to study the mesogenic characteristics of the molecule, an attempt has been made to estimate the variation of order parameter with respect to the change in temperature as well as degrees of freedom. These studies will be helpful to understanding the mesogenic character of any molecule prior to synthesis and promises future application in molecular engineering. 相似文献
143.
Sarah Jane Mear Tobias Lucas Grace P. Ahlqvist Dr. Juliana M. S. Robey Dr. Jule-Philipp Dietz Dr. Pankaj V. Khairnar Dr. Sanjay Maity Corshai L. Williams Dr. David R. Snead Dr. Ryan C. Nelson Prof. Till Opatz Prof. Timothy F. Jamison 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(47):e202201311
Bedaquiline is a crucial medicine in the global fight against tuberculosis, yet its high price places it out of reach for many patients. Herein, we describe improvements to the key industrial lithiation-addition sequence that enable a higher yielding and therefore more economical synthesis of bedaquiline. Prioritization of mechanistic understanding and multi-lab reproducibility led to optimized reaction conditions that feature an unusual base-salt pairing and afford a doubling of the yield of racemic bedaquiline. We anticipate that implementation of these improvements on manufacturing scale will be facile, thereby substantially increasing the accessibility of this essential medication. 相似文献
144.
Akash Prabhu Robert D. Crapnell Kasper Eersels Bart van Grinsven Aruna K. Kunhiraman Pankaj Singla Jake McClements Craig E. Banks Katarina Novakovic Marloes Peeters 《Current Opinion in Electrochemistry》2022
Biopolymers possess highly favorable properties for electrochemical biosensing such as their inherent biocompatibility, inexpensive nature, and strong interfacial adhesion. In this mini-review, we will focus on chitosan and polydopamine, two of the most commonly used biopolymers, for electrochemical sensing applications. Chitosan is a polysaccharide that exhibits high chemical resistance, offers straightforward modification and cross-linking, and possesses antibacterial properties and mucoadhesion. Polydopamine has the benefit of universal adhesion, in addition to the ability to form self-assembled structures. We will demonstrate how the unique structural and electrochemical features of these biopolymers can be used in a range of electrochemical biosensing platforms. 相似文献
145.
146.
147.
148.
Dubey DK Pardasani D Gupta AK Palit M Kanaujia PK Tak V 《Journal of chromatography. A》2006,1107(1-2):29-35
Unambiguous detection and identification of chemical warfare agents (CWAs) and related compounds are of paramount importance from verification point of view of Chemical Weapons Convention (CWC). It requires development of fast, reliable, simple and reproducible sample preparation of CWAs from water which is likely to be contaminated during deliberate or inadvertent spread of CWAs. This work describes development of hollow fiber liquid-phase microextraction (HF-LPME) method for efficient extraction of CWAs (such as sarin, sulfur mustard and their analogues) from water followed by gas chromatography-mass spectrometric analysis. Extraction parameters, such as organic solvent, agitation, extraction time, and salt concentration were optimized. Best recoveries of target analytes were achieved using 1 microL trichloroethylene as extracting solvent, 1000 rpm stirring rate, 15 min extraction time, and 30% NaCl. Excellent precision was observed with less than 7.6% RSD. The limit of detection by HF-LPME was achieved up to 0.1 microg/L at 30% salt concentration. 相似文献
149.
We investigate here quantum effects in gravitational collapse of a scalar field model which classically leads to a naked singularity. We show that nonperturbative semiclassical modifications near the singularity, based on loop quantum gravity, give rise to a strong outward flux of energy. This leads to the dissolution of the collapsing cloud before the singularity can form. Quantum gravitational effects thus censor naked singularities by avoiding their formation. Further, quantum gravity induced mass flux has a distinct feature which may lead to a novel observable signature in astrophysical bursts. 相似文献
150.
A simple catalytic system based on PdCl2 and triphenylphosphine chalcogenides (PPh3X; X = O, S, Se) is found to be highly effective (up to 97% isolated yield) in the room temperature Suzuki-Miyaura reactions. Under the same experimental conditions, triphenylphosphine chalcogenides as ligands show superior activities compared to free triphenylphosphine. 相似文献