全文获取类型
收费全文 | 205篇 |
免费 | 15篇 |
国内免费 | 6篇 |
学科分类
数理化 | 226篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 12篇 |
2014年 | 9篇 |
2013年 | 16篇 |
2012年 | 10篇 |
2011年 | 20篇 |
2010年 | 17篇 |
2009年 | 11篇 |
2008年 | 20篇 |
2007年 | 12篇 |
2006年 | 14篇 |
2005年 | 12篇 |
2004年 | 10篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1985年 | 1篇 |
1980年 | 1篇 |
1968年 | 1篇 |
1963年 | 1篇 |
1961年 | 1篇 |
1940年 | 2篇 |
排序方式: 共有226条查询结果,搜索用时 15 毫秒
1.
Cover Picture: Coordination Chemistry of N‐Heterocyclic Nitrenium‐Based Ligands (Chem. Eur. J. 19/2015) 下载免费PDF全文
2.
Miklos Ajtai James Aspnes Moni Naor Yuval Rabani Leonard J Schulman Orli Waarts 《Journal of Algorithms in Cognition, Informatics and Logic》1998,29(2):306-357
On-line machine scheduling has been studied extensively, but the fundamental issue of fairness in scheduling is still mostly open. In this paper we explore the issue in settings where there are long-lived processes which should be repeatedly scheduled for various tasks throughout the lifetime of a system. For any such instance we develop a notion ofdesiredload of a process, which is a function of the tasks it participates in. Theunfairnessof a system is the maximum, taken over all processes, of the difference between the desired load and the actual load.An example of such a setting is thecarpool problemsuggested by Fagin and Williams [IBM Journal of Research and Development27(2) (1983), 133–139]. In this problem, a set ofnpeople form a carpool. On each day a subset of the people arrive and one of them is designated as the driver. A scheduling rule is required so that the driver will be determined in a “fair” way.We investigate this problem under various assumptions on the input distribution. We also show that the carpool problems can capture several other problems of fairness in scheduling. 相似文献
3.
Ahmed M. Assaf 《组合设计杂志》1993,1(6):453-458
A (v, k. λ) covering design of order v, block size k, and index λ is a collection of k-element subsets, called blocks, of a set V such that every 2-subset of V occurs in at least λ blocks. The covering problem is to determine the minimum number of blocks, α(v, k, λ), in a covering design. It is well known that $ \alpha \left({\nu,\kappa,\lambda } \right) \ge \left\lceil {\frac{\nu}{\kappa}\left\lceil {\frac{{\nu - 1}}{{\kappa - 1}}\lambda} \right\rceil} \right\rceil = \phi \left({\nu,\kappa,\lambda} \right) $, where [χ] is the smallest integer satisfying χ ≤ χ. It is shown here that α (v, 5, λ) = ?(v, 5, λ) + ? where λ ≡ 0 (mod 4) and e= 1 if λ (v?1)≡ 0(mod 4) and λv (v?1)/4 ≡ ?1 (mod 5) and e= 0 otherwise With the possible exception of (v,λ) = (28, 4). © 1993 John Wiley & Sons, Inc. 相似文献
4.
Assaf Rinot 《Mathematical Logic Quarterly》2019,65(2):200-204
We present a weak sufficient condition for the existence of Souslin trees at successor of regular cardinals. The result is optimal and simultaneously improves an old theorem of Gregory and a more recent theorem of the author. 相似文献
5.
Mohamed E. Abouelela Hamdy K. Assaf Reda A. Abdelhamid Ehab S. Elkhyat Ahmed M. Sayed Tomasz Oszako Lassaad Belbahri Ahmed E. El Zowalaty Mohamed Salaheldin A. Abdelkader 《Molecules (Basel, Switzerland)》2021,26(6)
Severe acute respiratory syndrome coronavirus (SARS-CoV-2) disease is a global rapidly spreading virus showing very high rates of complications and mortality. Till now, there is no effective specific treatment for the disease. Aloe is a rich source of isolated phytoconstituents that have an enormous range of biological activities. Since there are no available experimental techniques to examine these compounds for antiviral activity against SARS-CoV-2, we employed an in silico approach involving molecular docking, dynamics simulation, and binding free energy calculation using SARS-CoV-2 essential proteins as main protease and spike protein to identify lead compounds from Aloe that may help in novel drug discovery. Results retrieved from docking and molecular dynamics simulation suggested a number of promising inhibitors from Aloe. Root mean square deviation (RMSD) and root mean square fluctuation (RMSF) calculations indicated that compounds 132, 134, and 159 were the best scoring compounds against main protease, while compounds 115, 120, and 131 were the best scoring ones against spike glycoprotein. Compounds 120 and 131 were able to achieve significant stability and binding free energies during molecular dynamics simulation. In addition, the highest scoring compounds were investigated for their pharmacokinetic properties and drug-likeness. The Aloe compounds are promising active phytoconstituents for drug development for SARS-CoV-2. 相似文献
6.
Na'il Saleh Marieh B. Al‐Handawi Muna S. Bufaroosha Khaleel I. Assaf Werner M. Nau 《Journal of Physical Organic Chemistry》2016,29(2):101-106
The formation of host–guest complexes of cucurbit[7]uril (CB7) with the antihistamine drug tripelennamine (TRP) was studied by optical and NMR spectroscopy. The experimental and computational results are consistent with inclusion of a single TRP molecule in CB7. Addition of CB7 has tuned drug protonation states associated with (de)protonation of the ethyldimethylammonium and exocyclic nitrogens with an increase in the associated pKa values by 1.5 and 2.5 units, respectively. The incorporation of antihistamines drugs such as TRP in cucurbiturils could be utilized for switching their capability for selective binding to histamine H1‐receptors, in the future. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
7.
Dr. Koushik Chandra Dr. Tapta Kanchan Roy Dr. Deborah E. Shalev Prof. Abraham Loyter Prof. Chaim Gilon Prof. R. Benny Gerber Prof. Assaf Friedler 《Angewandte Chemie (International ed. in English)》2014,53(36):9450-9455
We present a new approach for peptide cyclization during solid phase synthesis under highly acidic conditions. Our approach involves simultaneous in situ deprotection, cyclization and trifluoroacetic acid (TFA) cleavage of the peptide, which is achieved by forming an amide bond between a lysine side chain and a succinic acid linker at the peptide N‐terminus. The reaction proceeds via a highly active succinimide intermediate, which was isolated and characterized. The structure of a model cyclic peptide was solved by NMR spectroscopy. Theoretical calculations support the proposed mechanism of cyclization. Our new methodology is applicable for the formation of macrocycles in solid‐phase synthesis of peptides and organic molecules. 相似文献
8.
Let be a simplicial model category and J : a simplicial coaugmented functor. Given an object X, the assignment nJn+1X defines a cofacial resolution (an augmented cosimplicial space without its codegeneracy maps). Following Bousfield and Kan we define JsX = tots([n] Jn+1X). An object X is called J-injective if it is a retract of JX in Ho() via the natural map. We show that certain homotopy limits of J-injective objects are Js-injective. Our method is to use the notion of pro-weak equivalences which was first introduced in a different language and context by David Edwards and Harold Hastings. The key observation is that a cofacial resolution X (-1) X which admits a left contraction gives rise to a pro-weak equivalence of towers {X(-1)}s0{totSX}s 0.The first author was supported in part by National Science Foundation grant DMS-0296117 相似文献
9.
10.