全文获取类型
收费全文 | 1797篇 |
免费 | 68篇 |
国内免费 | 11篇 |
专业分类
化学 | 1413篇 |
晶体学 | 22篇 |
力学 | 60篇 |
数学 | 112篇 |
物理学 | 269篇 |
出版年
2023年 | 9篇 |
2022年 | 20篇 |
2021年 | 51篇 |
2020年 | 40篇 |
2019年 | 48篇 |
2018年 | 46篇 |
2017年 | 45篇 |
2016年 | 83篇 |
2015年 | 64篇 |
2014年 | 115篇 |
2013年 | 157篇 |
2012年 | 138篇 |
2011年 | 153篇 |
2010年 | 83篇 |
2009年 | 63篇 |
2008年 | 109篇 |
2007年 | 112篇 |
2006年 | 89篇 |
2005年 | 89篇 |
2004年 | 53篇 |
2003年 | 47篇 |
2002年 | 44篇 |
2001年 | 12篇 |
2000年 | 16篇 |
1999年 | 10篇 |
1998年 | 19篇 |
1997年 | 12篇 |
1996年 | 13篇 |
1995年 | 12篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 12篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1969年 | 2篇 |
1964年 | 5篇 |
排序方式: 共有1876条查询结果,搜索用时 359 毫秒
991.
Tushar Kanti Chakraborty N. V. Suresh Kumar Saumya Roy Samit Kumar Dutta Ajit Chand Kunwar Balasubramanian Sridhar Harjinder Singh 《Journal of Physical Organic Chemistry》2011,24(8):720-731
Structural and electronic properties of diastereomers of tetrahydrofuran amino acids (TAA) derived tripeptide, Boc‐TAA‐Leu‐Val‐OMe, are studied using density functional theory. Predicted secondary folding patterns with hydrogen bonded pseudocycles of different sizes in peptides containing (2R,5S)‐cis‐TAA and (2S,5R)‐cis‐TAA are confirmed by detailed NMR studies of both, and single crystal X‐ray analysis of the former. A novel unusual folding pattern emanating from three‐centered hydrogen bond is found in peptide with (2R,5S)‐cis relationship. Stereochemical control on the orientation of interacting sites is substantiated by structural analysis of the peptides. Using natural bonding orbital and atoms in molecules analyses, charge transfer interactions are analyzed. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
992.
993.
Santosh V. Nalage Sidhanath V. Bhosale Suresh K. Bhargava Sheshanath V. Bhosale 《Tetrahedron letters》2012,53(23):2864-2867
We have synthesized a novel derivative of kanamycin A bearing a pyrenyl fluorophore which can be used for the specific recognition of heparin in EtOH:H2O (1:3) through formation of a 2:1 complex. The receptor shows specific optical signalling for heparin, but exhibits no significant changes on addition of various other biological molecules. 相似文献
994.
A theoretical model of propagation of Gaussian and Sine time irradiance of an electromagnetic beam in collisional dusty plasma has been done in the present analysis. It contains equilibrium of dust charge, particle density, and energy of plasma ingredients having charge neutrality. Ionization of neutral particles, recombination of free electrons with ions, adsorption and emission of electrons from dust grain surface, and binary collisions between plasma components are also considered in this treatment. Time varying behaviour of modified electron temperature and collision frequency has been illustrated numerically as a function of dust densities. Also, the comparative analyses of variation of beam waist parameter with the dimensionless length of transmission for both the Gaussian and Sine time irradiance are involved in this model as a function of distinguishable time width, collision frequencies, and dust densities under the condition that the size of dust nebulous is greater than the electrons mean free path for the adsorption on the dust grain surface. The observed results are significant for the applications in industry and astrophysics. 相似文献
995.
Veeranna Guguloth Narasimha Swamy Thirukovela Ramesh Balaboina Suresh Paidakula Ravinder Vadde 《Tetrahedron letters》2019,60(3):297-299
A first example of simple and efficient hydrophilic Pd-phosphine complexes catalyzed one-pot three-component reaction of ortho-bromo aldehydes, terminal alkynes and ammonium acetate proceeds through the tandem coupling-imination-annulation path for the synthesis of substituted isoquinolines, furopyridines and thienopyridines in good to excellent yields in green aqueous medium at mild temperature was described. 相似文献
996.
Gulamnabi L. Vanti Vijendra B. Nargund Basavesha K. N Rajinikanth Vanarchi Mahantesh Kurjogi Sikandar I. Mulla Suresh Tubaki Rajashekar R. Patil 《应用有机金属化学》2019,33(1)
Malvaceae and Brassicaceae family crops are economically important; however, their production has been markedly decreased in recent years due to various plant pests. Hence, the search for novel classes of efficient biological approaches continues due to unavailability of precise pesticides. The present study was designed to synthesize, characterize and evaluate the efficacy of silver nanoparticles (AgNPs) obtained using stem extract of Gossypium hirsutum (cotton plant) against plant pathogens Xanthomonas axonopodis pv. malvacearum and Xanthomonas campestris pv. campestris. Biosynthesized AgNPs were characterized using UV–visible spectrophotometry, Dynamic Light Scattering, Scanning Electron Microscopy combined with energy‐dispersive X‐ray analysis and Fourier transform infrared spectroscopy. The synthesized AgNPs were spherical in shape with size ranging from 20 to 100 nm. The characterized AgNPs were investigated for their efficacy against bacterial plant pathogens using the paper disc method. In vitro studies with two concentrations of AgNPs (50 and 100 μg mL?1) showed zone of inhibition 11.0 ± 1.0 and 12.3 ± 0.5 mm for X. axonopodis pv. malvacearum and 9.7 ± 0.6 and 15.33 ± 1.0 mm for X. campestris pv. campestris. Furthermore, the AgNPs exhibited strong antioxidant activity, and a phytotoxicity study on Vigna unguiculata (cowpea plant) showed no toxicity. Overall, the findings suggest that G. hirsutum stem extract could be efficiently used in the synthesis of AgNPs and showed antimicrobial activity against plant pathogens. Hence, the synthesized nanoparticles could be used to combat plant pathogens in the agriculture sector. 相似文献
997.
Applied Biochemistry and Biotechnology - Luteolin, a naturally derived polyphenol, has shown to induce apoptosis in HaCaT cells. Its role in induction of caspase-14 and thus in the terminal... 相似文献
998.
Silver sequestration of halides for the activation of Pd(OAc)2 catalyzed Mizoroki‐Heck reaction of 1,1 and 1,2 ‐ Disubstituted alkenes 下载免费PDF全文
Pronnoy G. Bangar Priyanka R. Jawalkar Swapnil R. Dumbre Dharmaraj J. Patil Suresh Iyer 《应用有机金属化学》2018,32(3)
A ligand free catalytic system consisting of Pd(OAc)2 (cat) and stoichiometric quantities of silver salts, AgOAc or AgBF4, exhibit high efficiency in the Mizoroki‐Heck arylation, transforming aryl iodides and 1,1 as well as 1,2 disubstituted alkenes into 1,1,2 – trisubstituted aryl alkenes in excellent yields in very short reaction times. 相似文献
999.
Patil Bhagyashree M. Shinde Sachinkumar K. Jagdale Ashutosh A. Jadhav Swati D. Patil Suresh S. 《Research on Chemical Intermediates》2021,47(10):4369-4398
Research on Chemical Intermediates - A transition metal/ligand/additive/promoter-free synthesis of 3-methyl-4-arylmethylene-isoxazol-5(4H)-ones and the Biginelli-like synthesis is carried out in a... 相似文献
1000.
The Active Site of a Prototypical “Rigid” Drug Target is Marked by Extensive Conformational Dynamics
Dr. Himanshu Singh Dr. Chandan K. Das Dr. Suresh K. Vasa Kristof Grohe Prof. Dr. Lars V. Schäfer Prof. Dr. Rasmus Linser 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(51):23116-23121
Drug discovery, in particular optimization of candidates using medicinal chemistry, is generally guided by structural biology. However, for optimizing binding kinetics, relevant for efficacy and off-target effects, information on protein motion is important. Herein, we demonstrate for the prototypical textbook example of an allegedly “rigid protein” that substantial active-site dynamics have generally remained unrecognized, despite thousands of medicinal-chemistry studies on this model over decades. Comparing cryogenic X-ray structures, solid-state NMR on micro-crystalline protein at room temperature, and solution NMR structure and dynamics, supported by MD simulations, we show that under physiologically relevant conditions the pocket is in fact shaped by pronounced open/close conformational-exchange dynamics. The study, which is of general significance for pharmacological research, evinces a generic pitfall in drug discovery routines. 相似文献