全文获取类型
收费全文 | 662篇 |
免费 | 15篇 |
国内免费 | 2篇 |
专业分类
化学 | 399篇 |
晶体学 | 29篇 |
力学 | 24篇 |
数学 | 70篇 |
物理学 | 157篇 |
出版年
2023年 | 8篇 |
2022年 | 10篇 |
2021年 | 18篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 19篇 |
2017年 | 15篇 |
2016年 | 22篇 |
2015年 | 13篇 |
2014年 | 21篇 |
2013年 | 40篇 |
2012年 | 51篇 |
2011年 | 48篇 |
2010年 | 20篇 |
2009年 | 30篇 |
2008年 | 23篇 |
2007年 | 31篇 |
2006年 | 34篇 |
2005年 | 29篇 |
2004年 | 25篇 |
2003年 | 15篇 |
2002年 | 8篇 |
2001年 | 10篇 |
2000年 | 12篇 |
1999年 | 4篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1970年 | 3篇 |
1969年 | 7篇 |
1968年 | 3篇 |
排序方式: 共有679条查询结果,搜索用时 31 毫秒
91.
R.P. Pant Manju Arora Balwinder Kaur Vinod Kumar Ashok Kumar 《Journal of magnetism and magnetic materials》2010,322(22):3688-3691
Nanoparticles of CoGdxFe2−xO4 (where x=0.0, 0.1, 0.3, 0.5) series have been prepared by chemical co-precipitation. The effect of Gd3+ ion concentration on crystalline phase, crystallinity, crystallite size, molecular vibrations and magnetic resonance has been investigated in detail. The crystallinity decreases with an increase in Gd3+ ion concentration and changes the structural parameters. The spin lattice relaxation has been correlated with the doping ion concentration. Similarly, the superparamagnetic behavior of these particles has been observed with EPR spectroscopy. 相似文献
92.
Mohan K. Kadalbajoo Puneet Arora 《Numerical Methods for Partial Differential Equations》2010,26(5):1206-1223
The advection‐diffusion equation has a long history as a benchmark for numerical methods. Taylor‐Galerkin methods are used together with the type of splines known as B‐splines to construct the approximation functions over the finite elements for the solution of time‐dependent advection‐diffusion problems. If advection dominates over diffusion, the numerical solution is difficult especially if boundary layers are to be resolved. Known test problems have been studied to demonstrate the accuracy of the method. Numerical results show the behavior of the method with emphasis on treatment of boundary conditions. Taylor‐Galerkin methods have been constructed by using both linear and quadratic B‐spline shape functions. Results shown by the method are found to be in good agreement with the exact solution. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2010 相似文献
93.
A logarithmic signature (LS) for a finite group G is an ordered tuple α = [A 1, A 2, . . . , A n ] of subsets A i of G, such that every element ${g \in G}$ can be expressed uniquely as a product g = a 1 a 2 . . . a n , where ${a_i \in A_i}$ . The length of an LS α is defined to be ${l(\alpha)= \sum^{n}_{i=1}|A_i|}$ . It can be easily seen that for a group G of order ${\prod^k_{j=1}{p_j}^{m_j}}$ , the length of any LS α for G, satisfies, ${l(\alpha) \geq \sum^k_{j=1}m_jp_j}$ . An LS for which this lower bound is achieved is called a minimal logarithmic signature (MLS) (González Vasco et al., Tatra Mt. Math. Publ. 25:2337, 2002). The MLS conjecture states that every finite simple group has an MLS. This paper addresses the MLS conjecture for classical groups of Lie type and is shown to be true for the families PSL n (q) and PSp 2n (q). Our methods use Singer subgroups and the Levi decomposition of parabolic subgroups for these groups. 相似文献
94.
S. V. Vidwans V. P. Salvi A. A. Rangwala Kuldeep Animesh K. Jain B. M. Arora 《辐射效应与固体损伤》2013,168(2-4):111-119
We have used ion implantation of 30 keV48Ti+ ions into a-Si films at nominal doses of 1020-1021 ions/m2 to fabricate coherent silicide layers. Characterization of these layers and study of their annealing behaviour were carried out using XRD and RBS techniques. We find that the layers are a mixture of Ti5Si4, TiSi, TiSi2 and Si. On annealing at relatively lower temperatures (up to ~ 300° C), predominant silicide phases present in the layer are Ti-rich, such as Ti5Si4 and TiSi. At higher temperatures, the Ti-rich layer has a tendency to consume unreacted Si from the film and to form a predominantly Si-rich silicide layer. A structure of silicon different from the diamond cubic structure is noticed in these implanted layers. 相似文献
95.
In this article, we look beyond convexity and introduce the four new classes of functions, namely, approximate pseudoconvex functions of type I and type II and approximate quasiconvex functions of type I and type II. Suitable examples illustrating the non emptiness of the newly defined classes and distinguishing them from the existing classical notions of pseudoconvexity and quasiconvexity are provided. These newly defined concepts are then employed to establish sufficient optimality conditions for the quasi efficient solutions of a vector optimization problem. 相似文献
96.
T. R. Ravindran A. K. Arora S. Ramya R. V. Subba Rao Baldev Raj 《Journal of Raman spectroscopy : JRS》2011,42(4):803-807
We report the first Raman spectroscopic investigations of medieval Indian art of 17th century. Three miniature paintings, belonging to Mogul and Rajput schools from the collections of the Madras Museum, were investigated by micro‐Raman spectroscopy using different excitation wavelengths. Many areas in the paintings exhibited rich spectra containing several intense Raman bands. The Raman bands were assigned on the basis of the reported reference spectra of the pigments. Evidences for the presence of massicot, red‐lead, lead‐white, vermilion, litharge, Indian yellow and anatase are found. In addition, tentative assignments of some of the Raman bands to atacamite and orpiment are also made. The present studies suggest that several mineral‐based unique pigments were popular among the Indian artists of this period. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
97.
Improvement on Quantum Teleportation of Three and Four Qubit States Using Multi-Qubit Cluster States
Verma Vikram Singh Nidhi Singh Ravi S. 《International Journal of Theoretical Physics》2021,60(10):3973-3981
International Journal of Theoretical Physics - In 2016, Li et al. [Int. J. Theor. Phys. 55, 1820–1823 (2016)] proposed schemes for quantum teleportation of certain class of three and four... 相似文献
98.
Yedukondalu Nalli Palak Arora Syed Riyaz-Ul-Hassan Asif Ali 《Tetrahedron letters》2018,59(25):2470-2472
The discovery of a new spiran based natural product, prenylspirodinone (1), together with six known cannabinoids (2–7) from the leaves of Cannabis sativa (Marijuana) is reported. All compounds were screened for antifungal and antibacterial activity against a panel of microbial pathogens and exhibited antimicrobial activities with IC50 values ranging from 2.6 to 49.6?µM. Compound 2, a propyl substituted cannabidiol, was determined to be a specific inhibitor against C. albicans (IC50 11.9?µM) and can be considered as a new lead against Candidiasis. 相似文献
99.
The use of dimedone in green chemistry has been described for the synthesis of selective heterocyclic motifs which are both pharmacologically and industrially important. The objective of this review is to summarize some of the selected recent advances of dimedone in the synthesis of organic compounds utilizing green chemistry procedures. 相似文献
100.
Effect of loop orientation on quadruplex-TMPyP4 interaction 总被引:1,自引:0,他引:1
G-quadruplexes are believed to be potential targets for therapeutic intervention and this has resulted in designing of various quadruplex interacting ligands. Moreover, reports about existence of quadruplex forming sequences across the genome have propelled greater interest in understanding their interaction with small molecules. An intramolecular quadruplex sequence can adopt different conformations, owing to different orientation of loops in the structure. The differences in the loop orientation can affect their molecular recognition. Herein, we have studied the interaction of 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H, 23H-porphine (TMPyP4), a well-known G quadruplex binding ligand with three DNA quadruplexes differing in loop orientations. Results obtained from UV, ITC, and SPR studies have coherently revealed that the TMPyP4 molecule shows preferential binding to parallel G-quadruplex ( c-myc and c-kit) over its antiparallel counterpart (human telomeric). The binding affinity for parallel quadruplex was (10(7)) 1 order of magnitude higher than that for antiparallel DNA quadruplex (10 ). The study shows two binding modes, stronger binding (10(7)) of TMPyP4 involving end stacking and a weaker external binding (10 ), while TMPyP4 shows only one binding mode with duplex with a binding affinity of the order of 10(6). Overall, the study emphasizes that differences in the loop orientation give rise to different conformations of quadruplex, which in turn govern its binding to small molecules, and thereby play a pivotal role in molecular recognition. 相似文献