全文获取类型
收费全文 | 1330篇 |
免费 | 49篇 |
国内免费 | 3篇 |
专业分类
化学 | 824篇 |
晶体学 | 4篇 |
力学 | 40篇 |
数学 | 96篇 |
物理学 | 418篇 |
出版年
2023年 | 16篇 |
2022年 | 15篇 |
2021年 | 17篇 |
2020年 | 33篇 |
2019年 | 46篇 |
2018年 | 31篇 |
2017年 | 24篇 |
2016年 | 50篇 |
2015年 | 33篇 |
2014年 | 66篇 |
2013年 | 107篇 |
2012年 | 97篇 |
2011年 | 100篇 |
2010年 | 63篇 |
2009年 | 54篇 |
2008年 | 72篇 |
2007年 | 89篇 |
2006年 | 74篇 |
2005年 | 69篇 |
2004年 | 43篇 |
2003年 | 20篇 |
2002年 | 24篇 |
2001年 | 4篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 10篇 |
1997年 | 11篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1994年 | 9篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 12篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 6篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1975年 | 10篇 |
1974年 | 2篇 |
1973年 | 4篇 |
排序方式: 共有1382条查询结果,搜索用时 724 毫秒
51.
Yashwantsinh S. Jadeja Khushal M. Kapadiya Hetal J. Jebaliya Anamik K. Shah Ranjan C. Khunt 《Magnetic resonance in chemistry : MRC》2017,55(6):589-594
Hesperidin is flavonoid molecule found in citrus fruits (Citrus reticulata), especially difficult to extract, classify and characterize. Present work is to study the unresolved relative configuration of Hesperidin through the dihedral angle, coupling constant and different NMR techniques. The Karplus equation and its modifications have been originated from the valence bond theory and associated with dihedral angle and coupling constant. The result data set of calculated dihedral angle can probe significant method to assign the virtual configuration of natural products and also resolved stereochemistry of Hesperidin at C‐2 position in. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
52.
53.
Corrigendum: Triazole‐Tailored Guanosine Dinucleosides as Biomimetic Ion Channels to Modulate Transmembrane Potential
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)
54.
55.
56.
We present an analysis of structural, electronic, and mechanical properties of cubic titanium dioxide(TiO_2) using an all electron orthogonalzed linear combinations of atomic orbitals(OLCAO) basis set under the framework of density functional theory(DFT). The structural property, especially the lattice constant a, and the electronic properties such as the band diagram and density of states(DOS) are studied and analyzed. The mechanical properties such as bulk moduli, shear moduli, Young's Moduli, and Poison's ratio are also investigated thoroughly. The calculations are carried out on shear moduli and anisotropy factor for cubic TiO_2. The Vickers hardness is also tested for fluorite and pyrite cubic-structured TiO_2. Furthermore, the results are compared with the previous theoretical and experimental results. It is found that DFTbased simulation produces results which are approximation to experimental results, whereas the calculated elastic constants are better than the previous theoretical and experimental values. 相似文献
57.
Gakhyun Kim Dr. Ranjan Dutta Dr. Won-Young Cha Dr. Seong-Jin Hong Dr. Juwon Oh Dr. Dikhi Firmansyah Hongil Jo Prof. Dr. Kang Min Ok Prof. Dr. Chang-Hee Lee Prof. Dr. Dongho Kim 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(69):16434-16440
π–π Stacking is omnipresent not only in nature but in a wide variety of practical fields applied to our lives. Because of its importance in a performance of natural and artificial systems, such as light harvesting system and working layer in device, many researchers have put intensive effort into identifying its underlying nature. However, for the case of π–π stacked systems composed of antiaromatic units, the understanding of the fundamental mechanisms is still unclear. Herein, we synthesized a new type of planar β,β’-phenylene-bridged hexaphyrin (1.0.1.0.1.0), referred as naphthorosarin which possesses the 24π-electron conjugated pathway. Especially, the corresponding antiaromatic porphyrinoid shows the unique property to form dimeric species adopting the face-to-face geometry which is unprecedented in cases of known annulated naphthorosarins. In order to elucidate the intriguing properties derived from the stacked dimer, the current study focuses on the experimental support to rationalize the observed π–π interactions between the two subunits. 相似文献
58.
Ambarish Mondal Rajat K. Tripathy Parul Dutta Manas Kumar Santra Anvarhusein A. Isab Christopher W. Bielawski Hemanta K. Kisan Swapan K. Chandra Joydev Dinda 《应用有机金属化学》2019,33(1)
The syntheses, structures, and chemotherapeutic activities of Ag(I)‐, Au(I)‐, and Ru(II)‐complexes ligated to a novel N‐heterocyclic carbene ligand, 2‐(4‐nitrophenyl)imidazo[1,5‐a]pyridin‐2‐ylidene ( 1 ), are described. The corresponding complexes, [Ag( 1 )2][PF6], [Au( 1 )2][PF6] ( 3 ), and [Ru( 1 )(p‐cymene)Cl][PF6] ( 4 ), were prepared using convenient transmetallation chemistry and characterized using a range of spectroscopic and analytical techniques. X‐ray crystallography revealed that complexes 2 and 3 adopted linear structures whereas 4 exhibited a prototypical “piano‐stool”‐like geometry; the structural assignments were further supported by DFT calculations. A series of in vitro studies revealed that while the aforementioned Ag(I), Au(I) and Ru(II) complexes exhibited significant cytotoxicities against the human colon adenocarcinoma (HCT 116), lung cancer (A549), and breast cancer (MCF7) cell lines, the Ru derivative was most prominent. 相似文献
59.
60.
Ranjan Maitra 《Journal of computational and graphical statistics》2013,22(1):132-142
Abstract Functional imaging of biologic parameters like in vivo tissue metabolism is made possible by Positron Emission Tomography (PET). Many techniques have been suggested for extracting such images from dynamic time-course sequences of reconstructed PET scans. Quantitating the precision of these estimates is important for drawing inferences on the biologic parameters. Analytic variance formulas are not immediate owing to the nonlinear methods used in extraction. The usual resampling approach is infeasible because each image reconstruction in PET is a computationally demanding solution to a high-dimensional linear inverse problem. We suggest an alternative simulation approach that approximates the distribution of reconstructed PET scans and performs a parametric bootstrap in the imaging domain. Results on a simplified model chosen to match the characteristics of PET reconstruction are very encouraging. Mixture analysis is used to estimate functional images; however, the suggested approach is general enough to extend to other techniques or imaging methods. 相似文献