全文获取类型
收费全文 | 2721篇 |
免费 | 136篇 |
国内免费 | 17篇 |
专业分类
化学 | 1824篇 |
晶体学 | 39篇 |
力学 | 60篇 |
数学 | 457篇 |
物理学 | 494篇 |
出版年
2023年 | 21篇 |
2022年 | 47篇 |
2021年 | 62篇 |
2020年 | 65篇 |
2019年 | 85篇 |
2018年 | 75篇 |
2017年 | 76篇 |
2016年 | 123篇 |
2015年 | 83篇 |
2014年 | 158篇 |
2013年 | 222篇 |
2012年 | 198篇 |
2011年 | 208篇 |
2010年 | 123篇 |
2009年 | 107篇 |
2008年 | 164篇 |
2007年 | 142篇 |
2006年 | 129篇 |
2005年 | 80篇 |
2004年 | 96篇 |
2003年 | 81篇 |
2002年 | 66篇 |
2001年 | 34篇 |
2000年 | 27篇 |
1999年 | 22篇 |
1998年 | 9篇 |
1997年 | 15篇 |
1996年 | 20篇 |
1995年 | 21篇 |
1994年 | 19篇 |
1993年 | 17篇 |
1992年 | 22篇 |
1991年 | 12篇 |
1990年 | 11篇 |
1989年 | 20篇 |
1988年 | 13篇 |
1987年 | 18篇 |
1986年 | 7篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 26篇 |
1981年 | 9篇 |
1980年 | 19篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1976年 | 8篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1961年 | 5篇 |
排序方式: 共有2874条查询结果,搜索用时 343 毫秒
11.
Prapti Saxena Sankar P. Sanyal 《Physica E: Low-dimensional Systems and Nanostructures》2004,24(3-4):244-248
We report a detailed study of the phonon properties of hexagonal boron nitride (BN) monolayers as well as nanotubes by using De Launay type of angular force model. The force constants used for calculation of phonon dispersion relations of the nanotube are derived from those for the monolayers of hexagonal by employing force constant method. These force constants have been modified to include the effect of curvature of the tubule. The results are then used to derive the phonon dispersion relations for (10,10) BN nanotubes using ‘zone-folding’ method. Calculated phonon modes are in good agreement with the experimental values obtained so far, for (10,10) armchair BN nanotubes. 相似文献
12.
S Uma Sankar 《Pramana》2006,67(4):655-663
In this talk I review the physics possible at India-based Neutrino Observatory (INO). I discuss the improvement in the precision
of currently known quantities and the possibility measuring the presently unknown quantities. 相似文献
13.
A graphite electrode modified with cobalt hexacyanoferrate by mechanical immobilization was used for amperometric determination of hydrazine. The modified electrode exhibits good catalytic activity for the oxidation of hydrazine at a reduced overpotential with remarkable sensitivity. The modified electrode showed a linear response for hydrazine in the concentration range of 2.0 × 10–5 to 2.8 × 10–4 M. The detection limit was 9.8 × 10–6 M (S/N = 3). The proposed modified electrode was simple, sensitive, rapid, stable and promising. 相似文献
14.
D. M. Bhardwaj D. C. Jain S. Dalela Ravi Kumar N. L. Saini K. B. Garg 《Physica B: Condensed Matter》2004,350(4):366-374
We have made the XAFS measurements at the Cr–K-edge on natural Indian ruby single crystals (corundum) and its two irradiated samples with fluence 1×1012 Ni6+ and 5×1012 Ni6+ ions/cm2. Irradiated samples show interesting changes in their physical appearance. XANES measurements show progressive decrease in Δoct value on increase of Ni fluence in irradiated samples. EXAFS measurements on these samples show decrease in Cr–O distance on increase of Ni fluence. Lowering of Δoct value is correlated with the increase of Cr–O distance. 相似文献
15.
Raj Gandhi Kamales Kar S. Uma Sankar Abhijit Bandyopadhyay Rahul Basu Pijushpani Bhattacharjee Biswajoy Brahmachari Debrupa Chakraborti M. Chaudhury J. Chaudhury Sandhya Choubey E. J. Chun Atri Desmukhya Anindya Datta Gautam Dutta Sukanta Dutta Anjan Giri Sourendu Gupta Srubabati Goswami Namit Mahajan H. S. Mani A. Mukherjee Biswarup Mukhopadhyaya S. N. Nayak M. Randhawa Subhendu Rakshit Asim K. Ray Amitava Raychaudhuri D. P. Roy Probir Roy Suryadeep Roy Shiv Sethi G. Sigl Arunansu Sil N. Nimai Singh Mark Vagins Urjit Yagnik 《Pramana》2003,60(2):405-409
This is the report of neutrino and astroparticle physics working group at WHEPP-7. Discussions and work on CP violation in
long baseline neutrino experiments, ultra high energy neutrinos, supernova neutrinos and water Cerenkov detectors are discussed. 相似文献
16.
17.
Sankar Prasad Bhuniya Safikur Rahman Anshul J. Satyanand Mahendrasinh M. Gharia Ashok M. Dave 《Journal of polymer science. Part A, Polymer chemistry》2003,41(11):1650-1658
Maize starch was modified by allyl chloride adopting an interfacial reaction technique with cetyltrimethyl ammonium bromide as a phase‐transfer catalyst and pyridine as an acid acceptor. The degree of substitution was determined from an increasing carbon content of the modified starch. The percentage of carbon and hydrogen of the allyl‐modified starch was estimated by elemental analysis (C, H, and N), and the product characterization was done through 1H NMR and 13C NMR analyses. The allyl‐modified starch was then copolymerized with methacrylic acid and a combination of methacrylic acid and acrylamide at 50 and 70 °C with potassium persulfate as an initiator. The copolymer thus formed swelled in distilled water after neutralization with sodium carbonate. The percentage of absorption capacity of the hydrogels was determined with distilled water and 0.9% NaCl solution. The highest percentage of absorption, 6500%, was achieved for the developed hydrogel containing allyl starch and acrylic monomer in a 1.7:1 w/w ratio and acrylic monomer, namely, methacrylic acid and acrylamide in a 3.2:1 w/w ratio. The study on biodegradability of the developed hydrogel showed that the hydrogel is degradable in the presence of diastase (amylase). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1650–1658, 2003 相似文献
18.
M K Parida Nita Sinha B Adhikary B Allanach A Alok K S Babu B Brahmachari D Choudhury E J Chun P K Das A Ghosal D Hitlin W S Hou S Kumar H N Li E Ma S K Majee G Majumdar B Mishra G Mohanty S Nandi H Pas M K Parida S D Rindani J P Saha N Sahu Y Sakai S Sen C Sharma C D Sharma S Shalgar N N Singh S Uma Sankar N Sinha R Sinha F Simonetto R Srikanth R Vaidya 《Pramana》2006,67(5):849-860
This is the report of flavor physics and model building working group at WHEPP-9. While activites in flavor physics have been
mainly focused on B-physics, those in model building have been primarily devoted to neutrino physics. We present summary of working group discussions
carried out during the workshop in the above fields, and also briefly review the progress made in some projects subsequently. 相似文献
19.
Structural studies were performed on catalytically active ruthenium(II) complexes used in interphases, by means of XAFS spectroscopy. The EXAFS investigations indicate that the complexes retain their structural integrity when they are embedded on polysiloxane matrices to form stationary phase materials. The AXAFS studies reveal that the variations in the catalytic activity of the complexes with different ligands can be correlated to the differences in the electronic structure around the active ruthenium center. The EXAFS investigations show that, in asymmetric transfer hydrogenation reactions catalysed by ruthenium(II) complexes, the co‐catalyst plays a crucial role not only in enhancing the catalytic activity, but also in determining the structure of the intermediate species. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
20.