全文获取类型
收费全文 | 169篇 |
免费 | 8篇 |
专业分类
化学 | 113篇 |
晶体学 | 2篇 |
力学 | 16篇 |
数学 | 25篇 |
物理学 | 21篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 8篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 10篇 |
2013年 | 4篇 |
2012年 | 22篇 |
2011年 | 17篇 |
2010年 | 6篇 |
2009年 | 10篇 |
2008年 | 6篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 7篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1963年 | 3篇 |
排序方式: 共有177条查询结果,搜索用时 15 毫秒
101.
Pessia Gilinsky‐Sharon Hugo E. Gottlieb David E. Rajsfus Keren Keinan‐Adamsky Vered Marks Pinchas Aped Aryeh A. Frimer 《Magnetic resonance in chemistry : MRC》2012,50(10):672-679
The nitration of tetraiodoethylene (7) yields 1,1‐diiodo‐2,2‐dinitroethylene (8). The latter reacts with alkylamines 9 or alkyldiamines 11 to give the corresponding acyclic 1,1‐diamino‐2,2‐dinitroethylenes 10 or their cyclic analogs 12, respectively. On the basis of liquid and solid‐state 13C and 15N NMR data, x‐ray analysis and ab initio calculations, we suggest that the title compounds are always zwitterionic and that the CA–CN bond is not a true double bond. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
102.
Roxana TucaliucValeriu V. Cotea Costel MoldoveanuGheorghita Zbancioc Calin DeleanuPeter G. Jones Ionel I. Mangalagiu 《Tetrahedron letters》2011,52(48):6439-6442
A straightforward, efficient and selective route for obtaining hybrid trifluoromethyl-substituted γ-lactones and fused nitrogen heterocycles is presented. The reaction could be guided either to γ-lactones with a nitrogen-containing heterocyclic skeleton (for monocyclic systems) or to fused nitrogen heterocycles (for fused bicyclic systems). A new class of γ-lactone with a nitrogen heterocyclic skeleton was obtained. Feasible reaction mechanisms involving cascade reactions are presented. 相似文献
103.
A. E. Cioabl? G. Trif Tordai P. Rotaru Margareta Socaciu Ioana Ionel 《Journal of Thermal Analysis and Calorimetry》2012,110(1):395-403
This article studied two sorts of biomass (corn and beech sawdust) and two varieties of coal (bituminous coal and lignite), which can produce energy using two different technologies: co-firing and anaerobic fermentation in pilot installations, in order to determine the future perspectives of those materials for large scale applications. By thermal analysis, the thermochemical characteristics of biomass (corn and beech sawdust) and of coal (bituminous coal from Jiu Valley and lignite from Oltenia basin) were determined. The co-firing tests have been achieved at a ratio of 15?% biomass, the rest being coal. At biomass?Ccoal co-firing, the SO2, NOx, CO, CO2 and fly ash concentrations in the flue gases is lower than the burning of fossil fuels. In the anaerobic fermentation of biomass, the maximum concentration of methane inside the produced biogas was 50?C55?% by volume in the beech sawdust batch and 67?C68?% by volume in the corn batch. 相似文献
104.
Ionel Rovenţa 《Mediterranean Journal of Mathematics》2016,13(2):573-583
In this paper, we study some weak majorization properties with applications for the trees. A strongly notion of majorization is introduced and Hardy–Littlewood–Polya’s inequality is generalized. 相似文献
105.
Accurately predicting loop structures is important for understanding functions of many proteins. In order to obtain loop models with high accuracy, efficiently sampling the loop conformation space to discover reasonable structures is a critical step. In loop conformation sampling, coarse-grain energy (scoring) functions coupling with reduced protein representations are often used to reduce the number of degrees of freedom as well as sampling computational time. However, due to implicitly considering many factors by reduced representations, the coarse-grain scoring functions may have potential insensitivity and inaccuracy, which can mislead the sampling process and consequently ignore important loop conformations. In this paper, we present a new computational sampling approach to obtain reasonable loop backbone models, so-called the Pareto optimal sampling (POS) method. The rationale of the POS method is to sample the function space of multiple, carefully selected scoring functions to discover an ensemble of diversified structures yielding Pareto optimality to all sampled conformations. The POS method can efficiently tolerate insensitivity and inaccuracy in individual scoring functions and thereby lead to significant accuracy improvement in loop structure prediction. We apply the POS method to a set of 4-12-residue loop targets using a function space composed of backbone-only Rosetta and distance-scale finite ideal-gas reference (DFIRE) and a triplet backbone dihedral potential developed in our lab. Our computational results show that in 501 out of 502 targets, the model sets generated by POS contain structure models are within subangstrom resolution. Moreover, the top-ranked models have a root mean square deviation (rmsd) less than 1 A in 96.8, 84.1, and 72.2% of the short (4-6 residues), medium (7-9 residues), and long (10-12 residues) targets, respectively, when the all-atom models are generated by local optimization from the backbone models and are ranked by our recently developed Pareto optimal consensus (POC) method. Similar sampling effectiveness can also be found in a set of 13-residue loop targets. 相似文献
106.
Zukerman-Schpector J Haiduc I Tiekink ER 《Chemical communications (Cambridge, England)》2011,47(47):12682-12684
M-carbonyl(lone pair)···π(aryl) interactions provide stability to their transition metal crystal structures. This supramolecular synthon usually leads to zero- or one-dimensional aggregation patterns; a rare example of a three-dimensional architecture based on the M-CO(lone pair)···π(aryl) synthon has also been revealed. 相似文献
107.
Shetty SG Ciobîcă IM Hensen EJ van Santen RA 《Chemical communications (Cambridge, England)》2011,47(35):9822-9824
A critical issue in the Fischer-Tropsch synthesis reaction is the blocking of the active sites for low barrier CO dissociation by the C(1) adsorbed species generated from CO dissociation, which can hinder the further steps in the FT process. Here, we propose a synchronized pathway for low barrier CO dissociation and C-C coupling on a corrugated Ru surface. 相似文献
108.
Popa I Cahill BP Maroni P Papastavrou G Borkovec M 《Journal of colloid and interface science》2007,309(1):28-35
The adsorption of poly(diallyldimethyl ammonium chloride) (DADMAC) on planar silica substrates was examined as a function of ionic strength and pH. The study was carried out with reflectometry in an impinging-jet cell and complemented by atomic force microscopy (AFM) and ellipsometry investigations. The adsorption process is initially transport limited, whereby the adsorption rate increases somewhat with increasing ionic strength. This effect is caused by a simultaneous decrease of the hydrodynamic radius of the polymer. After a transient period, the adsorption process saturates and leads to an adsorption plateau. The plateau value increases strongly with increasing ionic strength. This increase can be explained by progressive screening of the electrostatic repulsion between the adsorbing polyelectrolyte chains, as can be rationalized by a random sequential adsorption (RSA) model. The adsorbed amount further increases with increasing pH, and this effect is probably caused by the corresponding increase of the surface charge of the silica substrate. 相似文献
109.
Roxana M. Butnariu Maria D. Caprosu Vasilichia Bejan Ionel I. Mangalagiu Margareta Ungureanu Antonia Poiata Cristina Tuchilus Margareta Florescu 《Journal of heterocyclic chemistry》2007,44(5):1149-1152
110.
This study investigates the conformity to Benford’s Law of the information disclosed in financial statements. Using the first digit test of Benford’s Law, the study analyses the reliability of financial information provided by listed companies on an emerging capital market before and after the implementation of International Financial Reporting Standards (IFRS). The results of the study confirm the increase of reliability on the information disclosed in the financial statements after IFRS implementation. The study contributes to the existing literature by bringing new insights into the types of financial information that do not comply with Benford’s Law such as the amounts determined by estimates or by applying professional judgment. 相似文献