全文获取类型
收费全文 | 114286篇 |
免费 | 6858篇 |
国内免费 | 4746篇 |
专业分类
化学 | 49324篇 |
晶体学 | 1285篇 |
力学 | 8994篇 |
综合类 | 285篇 |
数学 | 35948篇 |
物理学 | 30054篇 |
出版年
2024年 | 143篇 |
2023年 | 779篇 |
2022年 | 1289篇 |
2021年 | 1371篇 |
2020年 | 1488篇 |
2019年 | 1419篇 |
2018年 | 11366篇 |
2017年 | 11127篇 |
2016年 | 7665篇 |
2015年 | 2585篇 |
2014年 | 2432篇 |
2013年 | 3007篇 |
2012年 | 6935篇 |
2011年 | 13714篇 |
2010年 | 7848篇 |
2009年 | 8179篇 |
2008年 | 8956篇 |
2007年 | 10817篇 |
2006年 | 2369篇 |
2005年 | 2939篇 |
2004年 | 2814篇 |
2003年 | 3049篇 |
2002年 | 2026篇 |
2001年 | 1073篇 |
2000年 | 1155篇 |
1999年 | 971篇 |
1998年 | 920篇 |
1997年 | 826篇 |
1996年 | 881篇 |
1995年 | 730篇 |
1994年 | 613篇 |
1993年 | 522篇 |
1992年 | 477篇 |
1991年 | 391篇 |
1990年 | 351篇 |
1989年 | 297篇 |
1988年 | 262篇 |
1987年 | 229篇 |
1986年 | 210篇 |
1985年 | 198篇 |
1984年 | 146篇 |
1983年 | 107篇 |
1982年 | 101篇 |
1981年 | 74篇 |
1980年 | 62篇 |
1979年 | 54篇 |
1914年 | 45篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Zhang Wen Liu Yang Song Dengpeng Guo Heng Hu Jinbang Wang Yunli Xu Weilin 《Cellulose (London, England)》2021,28(9):5911-5922
Cellulose - Traditional cotton fiber dyeing requires an abundance of salt, which leads to environmental pollution. Consequently, decreasing or eliminating the use of salt has become the primary... 相似文献
992.
993.
Carbon nanostructures (CNS) with high electrical conductivity and unique branched structure of carbon nanotubes combined with NiO nanofibers (NFs) were used as anode for lithium-ion batteries. CNS works as a framework substrate for the anodic conversion reaction of nickel oxide (NiO). Electrochemical performance and behavior of CNS/NiO anodes is compared with the conventional carbon (C)/NiO anodes. CNS/NiO NF-based anode retains high specific capacity under different current densities compared to C/NiO anode. Moreover, specific capacity as high as 450 mAh/g for CNS/NiO NF anode is observed compared to only 90 mAh/g for C/NiO NFs using a current density of 500 mA/g after 500 cycles. This improved performance is attributed to the highly conductive network of CNS leading to efficient charge transfer. The high porosity, electrical conductivity as well as the branched and networked nature of CNS reveal to be of critical importance to allow the electrochemical conversion reactions. 相似文献
994.
995.
996.
997.
998.
999.
N. Kuroda S. Ulmer D. J. Murtagh S. Van Gorp Y. Nagata M. Diermaier S. Federmann M. Leali C. Malbrunot V. Mascagna O. Massiczek K. Michishio T. Mizutani A. Mohri H. Nagahama M. Ohtsuka B. Radics S. Sakurai C. Sauerzopf K. Suzuki M. Tajima H. A. Torii L. Venturelli B. Wünschek J. Zmeskal N. Zurlo H. Higaki Y. Kanai E. Lodi Rizzini Y. Nagashima Y. Matsuda E. Widmann Y. Yamazaki 《Hyperfine Interactions》2015,235(1-3):13-20
In order to test CPT symmetry between antihydrogen and its counterpart hydrogen, the ASACUSA collaboration plans to perform high precision microwave spectroscopy of ground-state hyperfine splitting of antihydrogen atom in-flight. We have developed an apparatus (“cusp trap”) which consists of a superconducting anti-Helmholtz coil and multiple ring electrodes. For the preparation of slow antiprotons and positrons, Penning-Malmberg type traps were utilized. The spectrometer line was positioned downstream of the cusp trap. At the end of the beamline, an antihydrogen beam detector was located, which comprises an inorganic Bismuth Germanium Oxide (BGO) single-crystal scintillator housed in a vacuum duct and surrounding plastic scintillators. A significant fraction of antihydrogen atoms flowing out the cusp trap were detected. 相似文献
1000.
Three-dimensional fluorescence spectroscopy coupled with parallel factor analysis and neural network was applied to the year discrimination of mild aroma Chinese liquors. The excitation-emission fluorescence matrices (EEMs) of 120 samples with various years were measured by FLS920 fluorescence spectrometer. The trilinear decomposition of the data array was performed and the loading scores of and the excitation-emission profiles of four components were also obtained. The scores were employed as the inputs of the BP neural networks and the PARAFAC-BP identification model was constructed. 10 samples were collected from 10, 20 and 30 years of liquors respectively, and 30 samples were selected as the test sets. The remaining 90 samples were used as the training sets to build the training model. The year prediction of unknown samples was also carried out, and the prediction accuracy was 90%, 100% and 100%, respectively. Meanwhile, the discrimination analysis method and the multi way partial least squares discriminant analysis were compared, namely PARAFAC-BP and NPLS-DA. The results indicated that parallel factor combined with the neural network (PARAFAC-BP) has higher prediction accuracy. The proposed method can effectively extract the spectral characteristics, and also reduce the dimension of the input variables of neural network. A good year discrimination result was finally achieved. 相似文献