全文获取类型
收费全文 | 16450篇 |
免费 | 2693篇 |
国内免费 | 2324篇 |
专业分类
化学 | 12409篇 |
晶体学 | 186篇 |
力学 | 990篇 |
综合类 | 188篇 |
数学 | 2175篇 |
物理学 | 5519篇 |
出版年
2024年 | 13篇 |
2023年 | 233篇 |
2022年 | 324篇 |
2021年 | 431篇 |
2020年 | 556篇 |
2019年 | 586篇 |
2018年 | 517篇 |
2017年 | 490篇 |
2016年 | 749篇 |
2015年 | 752篇 |
2014年 | 972篇 |
2013年 | 1235篇 |
2012年 | 1432篇 |
2011年 | 1528篇 |
2010年 | 1176篇 |
2009年 | 1153篇 |
2008年 | 1267篇 |
2007年 | 1106篇 |
2006年 | 1034篇 |
2005年 | 798篇 |
2004年 | 636篇 |
2003年 | 546篇 |
2002年 | 653篇 |
2001年 | 578篇 |
2000年 | 423篇 |
1999年 | 366篇 |
1998年 | 273篇 |
1997年 | 219篇 |
1996年 | 240篇 |
1995年 | 206篇 |
1994年 | 152篇 |
1993年 | 114篇 |
1992年 | 103篇 |
1991年 | 111篇 |
1990年 | 89篇 |
1989年 | 82篇 |
1988年 | 54篇 |
1987年 | 54篇 |
1986年 | 45篇 |
1985年 | 36篇 |
1984年 | 27篇 |
1983年 | 22篇 |
1982年 | 19篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1974年 | 5篇 |
1972年 | 6篇 |
1971年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
1.
Applications of Mathematics - We focus on the free boundary problems for a Leslie-Gower predator-prey model with radial symmetry in a higher dimensional environment that is initially well populated... 相似文献
2.
Science China Chemistry - 相似文献
3.
Yersak Thomas A. Hao Fang Kang Chansoon Salvador James R. Zhang Qinglin Malabet Hernando Jesus Gonzalez Cai Mei 《Journal of Solid State Electrochemistry》2022,26(3):709-718
Journal of Solid State Electrochemistry - In this study, hot pressing was evaluated as a method of cell fabrication to increase the energy density of next-generation all-solid-state batteries with... 相似文献
4.
Given a graph sequence denote by T3(Gn) the number of monochromatic triangles in a uniformly random coloring of the vertices of Gn with colors. In this paper we prove a central limit theorem (CLT) for T3(Gn) with explicit error rates, using a quantitative version of the martingale CLT. We then relate this error term to the well-known fourth-moment phenomenon, which, interestingly, holds only when the number of colors satisfies . We also show that the convergence of the fourth moment is necessary to obtain a Gaussian limit for any , which, together with the above result, implies that the fourth-moment condition characterizes the limiting normal distribution of T3(Gn), whenever . Finally, to illustrate the promise of our approach, we include an alternative proof of the CLT for the number of monochromatic edges, which provides quantitative rates for the results obtained in [7]. 相似文献
5.
Zhao Tianqi Luo Tianzi Fang Bo Shi Lijiang Jin Yongxing Zhou Pengwei Yao Dong Li Chenxia Jing Xufeng Hong Zhi 《Journal of Russian Laser Research》2021,42(5):586-597
Journal of Russian Laser Research - The zero-refractive-index metamaterials have excellent electromagnetic properties, which provide new ideas and methods to realize the control of electromagnetic... 相似文献
6.
Journal of Visualization - In the in situ visualization of large-scale simulation, if using the traditional sort-last parallel rendering method, the performance cannot be fully improved due to the... 相似文献
7.
Yang Shaoming Deng Kaiqiang Shao Shan Zhang Jian Peng Jiaxi Fang Zhili Xu Wenyuan 《Journal of Solid State Electrochemistry》2022,26(3):821-830
Journal of Solid State Electrochemistry - A molecularly imprinted photoelectrochemical (PEC) cathodic sensor was developed for the detection of bovine serum albumin (BSA). The PEC sensor was... 相似文献
8.
9.
Dr. Zhe Zhang Dr. Xiaofeng Fang Dr. Zhihe Liu Dr. Haichao Liu Dr. Dandan Chen Prof. Shuqing He Prof. Jie Zheng Prof. Bing Yang Prof. Weiping Qin Prof. Xuanjun Zhang Prof. Changfeng Wu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(9):3720-3727
Fluorescence probes in the NIR-IIa region show drastically improved imaging owing to the reduced photon scattering and autofluorescence in biological tissues. Now, NIR-IIa polymer dots (Pdots) are developed with a dual fluorescence enhancement mechanism. First, the aggregation induced emission of phenothiazine was used to reduce the nonradiative decay pathways of the polymers in condensed states. Second, fluorescence quenching was minimized by different levels of steric hindrance to further boost the fluorescence. The resulting Pdots displayed a fluorescence QY of ca. 1.7 % in aqueous solution, suggesting an enhancement of ca. 21 times in comparison with the original polymer in tetrahydrofuran (THF) solution. Small-animal imaging by using the NIR-IIa Pdots exhibited a remarkable improvement in penetration depth and signal to background ratio, as confirmed by through-skull and through-scalp fluorescent imaging of the cerebral vasculature of live mice. 相似文献
10.
You Qin Rongrong Zhou Jian Jin Jing Xie Hao Liu Ping Cai Jun Shu Yahui Zhao Luqi Huang Shuihan Zhang 《Biomedical chromatography : BMC》2020,34(8):e4841
Ophiocordyceps xuefengensis (O. xuefengensis), a new species of caterpillar fungus, has been identified as the sister taxon of Ophiocordyceps sinensis (O. sinensis). The aims of the present study are to evaluate the anticancer activity and to qualitatively analyze the potential bioactive chemical constituents of O. xuefengensis and O. sinensis, comparatively. An MTT assay was used to evaluate the in vitro anticancer activities of different fractions from O. xuefengensis and O. sinensis. The results show that ethyl acetate fractions of O. xuefengensis and O. sinensis have significant in vitro anticancer activity. These two bioactive fractions were analyzed by ultra-performance liquid chromatography–electrospray ionization with quadrupole–time of flight tandem mass spectrometry technology. A total of 82 compounds and 101 compounds were identified or tentatively characterized in the bioactive fractions of O. xuefengensis and O. sinensis, respectively. Among these compounds, 68 existed in both O. xuefengensis and O. sinensis. A total of 67 compounds were reported in O. xuefengensis and 8 compounds were reported in caterpillar fungus for the first time. This is the first detailed comparative analysis of the in vitro anticancer activity and chemical ingredients between O. xuefengensis and O. sinensis. The application of this work will provide reliable fundamental pharmacological substances for the use of O. xuefengensis by Yao people. 相似文献