全文获取类型
收费全文 | 373篇 |
免费 | 15篇 |
国内免费 | 2篇 |
专业分类
化学 | 235篇 |
晶体学 | 4篇 |
力学 | 9篇 |
数学 | 18篇 |
物理学 | 65篇 |
无线电 | 59篇 |
出版年
2024年 | 5篇 |
2023年 | 7篇 |
2022年 | 19篇 |
2021年 | 23篇 |
2020年 | 16篇 |
2019年 | 22篇 |
2018年 | 18篇 |
2017年 | 13篇 |
2016年 | 21篇 |
2015年 | 19篇 |
2014年 | 20篇 |
2013年 | 36篇 |
2012年 | 25篇 |
2011年 | 22篇 |
2010年 | 9篇 |
2009年 | 14篇 |
2008年 | 15篇 |
2007年 | 16篇 |
2006年 | 18篇 |
2005年 | 14篇 |
2004年 | 16篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 1篇 |
2000年 | 4篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1982年 | 1篇 |
排序方式: 共有390条查询结果,搜索用时 392 毫秒
101.
Methyl N-(E-enoyl)pyroglutamates, derived from inexpensive and readily available in both enantiomeric forms pyroglutamic acid were found to be an efficient Michael acceptors in the addition reactions with nucleophilic glycine equivalent allowing for an efficient practical asymmetric synthesis of β-substituted pyroglutamic acids and related compounds. 相似文献
102.
Manju Solra Rohit Kapila Sourav Das Preeti Bhatt Dr. Subinoy Rana 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(15):e202400348
Dissipative supramolecular assemblies are hallmarks of living systems, contributing to their complex, dynamic structures and emerging functions. Living cells can spatiotemporally control diverse biochemical reactions in membrane compartments and condensates, regulating metabolite levels, signal transduction or remodeling of the cytoskeleton. Herein, we constructed membranous compartments using self-assembly of lipid-like amphiphiles (lipidoid) in aqueous medium. The new double-tailed lipidoid features Cu(II) coordinated with a tetravalent chelator that dictates the binding of two amphiphilic ligands in cis-orientation. Hydrophobic interactions between the lipidoids coupled with intermolecular hydrogen bonding led to a well-defined bilayer vesicle structure. Oil-soluble SNAr reaction is efficiently upregulated in the hydrophobic cavity, acting as a catalytic crucible. The modular system allows easy incorporation of exposed primary amine groups, which augments the catalysis of retro aldol and C−N bond formation reactions. Moreover, a higher-affinity chelator enables consumption of the Cu(II) template leveraging the differential thermodynamic stability, which allows a controllable lifetime of the vesicular assemblies. Concomitant temporal upregulation of the catalytic reactions could be tuned by the metal ion concentration. This work offers new possibilities for metal ion-mediated dynamic supramolecular systems, opening up a massive repertoire of functionally active dynamic “life-like” materials. 相似文献
103.
Mahipal Singh Sankhla Rohit Kumar Verma Varad Nagar Vaibhav Sharma Divyansh Jain Anuj Sharma Sanjay Kumar Kumud Kant Awasthi Harsh Pandey Kamakshi Pandey 《Macromolecular Symposia》2024,413(1):2300038
Since waste materials are used to identify, individualize, and evaluate evidence like fingerprints, palmprints, footprints, etc. that are found at a crime scene, they have a substantial impact on the field of forensic science. Many waste powders have recently been employed in fingerprint recognition. Nanosheets made up of eggshells have been put forward as an application in friction ridge development. Eggshell is a biochemical substance made up of chemical compounds like calcium carbonate, which is considered as a waste product. For the formation of an eggshell nanosheet (ESN), shells are dried and crushed into a fine powder and to get this powder in the form of a nanosheet, the Ball milling technique is used. The synthesis of pure ESN is confirmed by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) techniques. The size of nanosheets ranged from 30 to 90 nm as shown in SEM images. Developed powder is then used for the application of fingerprint development and it provides excellent results on all porous, non-porous, and semi-porous surfaces. Thus, this newly synthesized ESN powder can be used as a significant powder method in latent fingerprint technology. 相似文献
104.
Rohit Jindal Joel L. Plawsky Steven M. Cramer 《Journal of Sol-Gel Science and Technology》2008,45(2):133-141
Sol–gel immobilization provides a simple method for introducing different functions into microfluidic devices. In this study,
sol–gel was employed for the immobilization of C4 modified silica particles in microfluidic channels, which were etched in
quartz using photolithography and wet etching. The effect of variation in sol–gel synthesis conditions was evaluated by preparing
a variety of composite materials. Sol–gel syntheses were carried out under both acidic and basic conditions. The effect of
additives was also evaluated by introducing formamide and urea into the sol–gel precursor solutions. Composite materials prepared
under different conditions were characterized using SEM visualization, nitrogen adsorption experiments, conductivity ratio
of packed to empty channels, and separation experiments. SEM visualization provided qualitative information about the overall
morphology of the composite material. In addition, more quantitative characterization was obtained by calculating pore size
distributions and by measurements of conductivity ratios. Separation experiments were employed in order to evaluate the accessibility
of the C4 functional group in the materials prepared under different sol–gel synthesis conditions. While acidic conditions
promoted accessibility of the C4 functional group and improved separations, other conditions lead to reduced accessibility
and separation efficacy. 相似文献
105.
Trevor K. Ellis Hisanori Ueki Rohit Tiwari Vadim A. Soloshonok 《Tetrahedron: Asymmetry》2009,20(22):2629-2634
(S)-5-Oxo-N-phenyl-1-[(E)-3-phenylacryloyl]pyrrolidine-2-carboxamide, easily prepared from inexpensive and readily available, in both enantiomeric forms, glutamic/pyroglutamic acid was designed as an optimal type of chiral Michael acceptor for reactions with a series of nucleophilic glycine equivalents. A study of the corresponding Michael addition reactions revealed that the new generation of modular glycine derivatives, as a counterpart to the Michael acceptor, provides for operationally convenient preparation of β-phenyl pyroglutamic acids and related compounds with virtually complete chemical and stereochemical outcomes. 相似文献
106.
Rohini M. Godbole Agnes Grau Rohit Hegde Giulia Pancheri Yogi Srivastava 《Pramana》2006,66(4):657-668
In this note, we summarize and compare various model predictions forpp total cross-section σ
tot
pp
, giving an estimate of the range of predictions for the total cross-section, σ
tot
pp
expected at the LHC. We concentrate on the results for σ
tot
pp
obtained in a particular QCD based model of the energy dependence of the total cross-section, including the effect of soft
gluon radiation. We obtain the range of predictions in this model by exploring the allowed range of model parameters. We further
give a handy parametrisation of these results which incidentally spans the range of various other available predictions at
the LHC as well 相似文献
107.
108.
N-Heterocyclic carbenes (NHC) are efficient catalysts for transesterification/acylation reactions involving secondary alcohols. The catalytic transformations are carried out employing low catalyst loadings in convenient reaction times at room temperature. 相似文献
109.
110.
Madhuresh K. Sethi Somashekar R. Bhandya Nagaraj Maddur Rohit Shukla Anish Kumar V.S.N. Jayalakshmi Mittapalli 《Tetrahedron: Asymmetry》2013,24(7):374-379
A novel chemo-enzymatic synthesis of (S)-rivastigmine using ketoreductases with NADH/NADPH as the proton donor has been demonstrated. An exclusive enzymatic process has been developed by exploring the possible ketoreductases by screening to identify enzymes useful for the preparation of the (S)-isomer intermediate, and scaling up of the enzymatic process for the production of an adequate, enantiomerically pure precursor of rivastigmine and for the total synthesis of (S)-rivastigmine. 相似文献