全文获取类型
收费全文 | 321篇 |
免费 | 15篇 |
国内免费 | 2篇 |
专业分类
化学 | 210篇 |
晶体学 | 2篇 |
力学 | 4篇 |
数学 | 23篇 |
物理学 | 99篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 13篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 19篇 |
2012年 | 22篇 |
2011年 | 22篇 |
2010年 | 16篇 |
2009年 | 12篇 |
2008年 | 14篇 |
2007年 | 28篇 |
2006年 | 15篇 |
2005年 | 20篇 |
2004年 | 18篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1941年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有338条查询结果,搜索用时 156 毫秒
111.
Unlike the simple phenazine (PZ) molecule, one of its derivatives, dibenzo[a,c]phenazine (DBPZ) forms a charge-transfer complex in the triplet state (3ECT) with different amines, e.g., N,N-dimethylaniline (DMA), 4,4'-bis(dimethylamino)diphenylmethane (DMDPM), and triethylamine (TEA). Formation of the 3ECT and radical ion pairs (RIPs) due to electron transfer is identified by laser flash photolysis. The RIPs are much more abundant in the cases of DMA and DMDPM rather than in TEA. Interestingly, a prominent magnetic field effect (MFE) is observed in both the cases of 3ECT and RIPs in homogeneous acetonitrile-water (MeCN/H2O) mixtures. This rare observation of the 3ECT and MFE in non-viscous medium could be explained by considering the extended planar structure of DBPZ and inter-radical hydrogen bonding, mediated by the intervening water molecules. The magnetic field behavior is consistent with the hyperfine mechanism; however, the low B1/2 value for DBPZ-TEA system is ascribed to fast electron exchange due to the close proximity of the corresponding radical ions. 相似文献
112.
113.
The acronym “CADD” is often used interchangeably to refer to “Computer Aided Drug Discovery” and “Computer Aided Drug Design”. While the former definition implies the use of a computer to impact one or more aspects of discovering a drug, in this paper we contend that computational chemists are most effective when they enable teams to apply true design principles as they strive to create medicines to treat human disease. We argue that teams must bring to bear multiple sub-disciplines of computational chemistry in an integrated manner in order to utilize these principles to address the multi-objective nature of the drug discovery problem. Impact, resourcing principles, and future directions for the field are also discussed, including areas of future opportunity as well as a cautionary note about hype and hubris. 相似文献
114.
We combine a simple lattice-gas model for fluid mixtures along with polymer mean-field theory for block copolymer melts to study the stability of thin films of diblock copolymers in the presence of compressible fluid solvents. Using a free energy analysis, the stable and unstable thicknesses of a copolymer thin film are obtained for given solvent conditions. Our results suggest that the interplay between confinement, the compressibility of the solvent, and its selectivity to polymer component can lead to significant changes on the ordering and stability of the diblock copolymer thin films. Our results are in qualitative agreement with recent experimental results. 相似文献
115.
Elegbede AI Haldar MK Manokaran S Kooren J Roy BC Mallik S Srivastava DK 《Chemical communications (Cambridge, England)》2007,(32):3377-3379
We offer a novel strategy for designing "multi-prong" inhibitors of enzymes by incorporating selective ligands on the liposomal surface. 相似文献
116.
Bhattacharya S Chattopadhyay S Nayak SK Bhattacharya Banerjee S Banerjee M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,68(3):427-431
The host-guest interactions of various tetraarylporphyrins (TP), viz., 5,10,15,20-tetraphenyl-21H,23H-porphyrin (1), 5,10,15,20-tetrakis(octadecyloxyphenyl)-21H,23H-porphyrin (2) and 5,10,15,20-tetrakis(dodecyloxyphenyl)-21H,23H-porphyrin (3) with C60 and C70 have been studied by 1H NMR, UV-vis and fluorescence spectroscopic techniques in toluene medium. All the fullerene/porphyrin complexes are found to be stable with 1:1 stoichiometry. Binding constants (K) of all the fullerene/porphyrin complexes have been determined by fluorescence quenching experiment. The trend in K values revealed that the presence of long chain n-alkyl group in tetraarylporphyrin effectively and remarkably increases the selectivity ratio of C70 over C60. Theoretical calculations have extended a good support in interpreting the stability difference between various fullerene/TP complexes. 相似文献
117.
Lewis acid-mediated unprecedented ring-opening rearrangement of 2-aryl-N-tosylazetidines to enantiopure (E)-allylamines 总被引:1,自引:0,他引:1
A highly efficient strategy for Cu(OTf)2-mediated ring-opening of 2-aryl-N-tosylazetidines in polar and coordinating solvents followed by an unprecedented rearrangement to substituted achiral and chiral (E)-allylamines (ee >99%) is reported. The methodology has been applied for the synthesis of gamma-unsaturated-beta-amino acids. A plausible mechanism for the rearrangement is also described. 相似文献
118.
Highly Selective Addition of a Broad Spectrum of Trimethylsilane Pro‐nucleophiles to N‐tert‐Butanesulfinyl Imines
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)
Manas Das Prof. Dr. Donal F. O'Shea 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(51):18717-18723
Addition of organotrimethylsilane reagents to chiral N‐tert‐butanesulfinyl imines can be achieved in good yields and with excellent diastereoselectivities by employing TMSO?/Bu4N+ as a Lewis base activator in THF. A variety of aliphatic, aromatic, heteroaromatic and organometallic chiral imines were utilised as electrophiles for the synthesis of enantioenriched N‐tert‐butanesulfinyl amides. Remarkably, the same sets of reaction conditions could be used with a highly diverse range of bench‐stable organotrimethylsilane reagents, which highlights the generality and robustness of this methodology. 相似文献
119.
A highly regio- and stereoselective route for the synthesis of racemic and nonracemic tetrahydroquinoxalines via the S(N)2-type ring-opening of activated aziridines with 2-bromoanilines followed by the Pd-catalyzed intramolecular C-N bond formation is described. 相似文献
120.
Manas Kumar Maiti 《European Journal of Operational Research》2011,213(1):96-106
A genetic algorithm (GA) with varying population size is developed where crossover probability is a function of parents’ age-type (young, middle-aged, old, etc.) and is obtained using a fuzzy rule base and possibility theory. It is an improved GA where a subset of better children is included with the parent population for next generation and size of this subset is a percentage of the size of its parent set. This GA is used to make managerial decision for an inventory model of a newly launched product. It is assumed that lifetime of the product is finite and imprecise (fuzzy) in nature. Here wholesaler/producer offers a delay period of payment to its retailers to capture the market. Due to this facility retailer also offers a fixed credit-period to its customers for some cycles to boost the demand. During these cycles demand of the item increases with time at a decreasing rate depending upon the duration of customers’ credit-period. Models are formulated for both the crisp and fuzzy inventory parameters to maximize the present value of total possible profit from the whole planning horizon under inflation and time value of money. Fuzzy models are transferred to deterministic ones following possibility/necessity measure on fuzzy goal and necessity measure on imprecise constraints. Finally optimal decision is made using above mentioned GA. Performance of the proposed GA on the model with respect to some other GAs are compared. 相似文献