全文获取类型
收费全文 | 19833篇 |
免费 | 3293篇 |
国内免费 | 3639篇 |
专业分类
化学 | 16163篇 |
晶体学 | 437篇 |
力学 | 934篇 |
综合类 | 366篇 |
数学 | 2278篇 |
物理学 | 6587篇 |
出版年
2024年 | 16篇 |
2023年 | 304篇 |
2022年 | 476篇 |
2021年 | 563篇 |
2020年 | 788篇 |
2019年 | 793篇 |
2018年 | 696篇 |
2017年 | 709篇 |
2016年 | 946篇 |
2015年 | 1038篇 |
2014年 | 1236篇 |
2013年 | 1587篇 |
2012年 | 1742篇 |
2011年 | 1923篇 |
2010年 | 1578篇 |
2009年 | 1431篇 |
2008年 | 1598篇 |
2007年 | 1522篇 |
2006年 | 1328篇 |
2005年 | 1068篇 |
2004年 | 915篇 |
2003年 | 713篇 |
2002年 | 759篇 |
2001年 | 646篇 |
2000年 | 468篇 |
1999年 | 354篇 |
1998年 | 241篇 |
1997年 | 195篇 |
1996年 | 201篇 |
1995年 | 137篇 |
1994年 | 133篇 |
1993年 | 101篇 |
1992年 | 85篇 |
1991年 | 77篇 |
1990年 | 65篇 |
1989年 | 43篇 |
1988年 | 34篇 |
1987年 | 39篇 |
1986年 | 26篇 |
1985年 | 35篇 |
1984年 | 16篇 |
1983年 | 24篇 |
1982年 | 19篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 11篇 |
1976年 | 8篇 |
1974年 | 6篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
1.
2.
3.
4.
Journal of Theoretical Probability - Consider the sample covariance matrices of form $$W=n^{-1}C C^{\top }$$ , where C is a $$k\times n$$ matrix with real-valued, independent and identically... 相似文献
5.
6.
Herein, we successfully construct the 3D biocompatible graphene through crosslinking 2D graphene nanosheet onto carbon fiber paper with poly(diallyldimethylammonium chloride) (PDDA) as anode of the alcohol biofuel cell. Compared with the bioanode without 3D graphene, the current density and output power of PDDA-graphene-ADH bioanode is increased by 23 % and 41 % at a high concentration of ethanol at pH 8.9, suggesting the stabilization role of graphene in enzyme loading. The study provides us a deep analysis on structures and performances of the bioanode incl. electrochemistry, X-ray photoelectron spectra, and atomic force microscopy images, which is significant to develop the new methods to construct 3D porous electrodes in energy conversion device. 相似文献
7.
使用改良的hummers法制备出的氧化石墨烯为载体,采用共沉淀法制备出磁性CoFe2O4/氧化石墨烯(MGO),再使用三乙烯四胺(TETA)对磁性CoFe2O4/氧化石墨烯进行氨基功能化,制备出氨基功能化磁性CoFe2O4/氧化石墨烯吸附剂.采用X-射线衍射仪(XRD)、傅里叶变换红外光谱仪(FT-IR)和扫描电子显微镜(SEM)对TETA-MGO的物相、化学组成和微观形貌进行表征,以TETA-MGO作为吸附剂去除电镀废水中Cr(Ⅵ),探讨吸附性能和吸附机理,分析TETA-MGO在外加磁场下的液固分离和再生吸附性能.结果表明纳米级立方尖晶石相磁性CoFe2O4均匀生长于氧化石墨烯的表面和片层之间,TETA通过C-N键与磁性氧化石墨烯(MGO)相连,氨基功能化成功,活性吸附位点增点.室温下,pH =2时吸附效果最佳,吸附120 min时达到吸附平衡,平衡吸附量约为48.66 mg·g-1,TETA-MGO对Cr(Ⅵ)的吸附动力学和吸附热力学可分别使用拟二级动力学模型和Langmuir等温吸附模型描述,吸附过程主要属于化学吸附控制的单分子层吸附,使用外加磁场可以对TETA-MGO实现简单的固液分离,TETA-MGO经过6次再生吸附后,对Cr(Ⅵ)的吸附量仅下降19.67;,说明具有良好的循环再生吸附能力. 相似文献
8.
Chen Yujie Sang Weixuan Chen Rong Liu Xue Li Xiaoyan Guan Fenfen Li Xun Xiao Hui 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(1):367-373
Journal of Radioanalytical and Nuclear Chemistry - The nanoscale zero-valent nickel (nano-Ni0) was prepared by liquid-phase reduction method and characterized by BET, XPS, FT-IR and XRD and be used... 相似文献
9.
Natural enzymes have been praised highly as ideal catalysts, presumably owing to their remarkable advantages of high efficiency, high selectivity, and mild reaction conditions. The reports of chemical simulation and systematic synthesis of natural enzymes such as peroxidase (POD) are rare because of their complex biological structures. POD represents a large family of oxidoreductases and offers a wide range of applications in many fields of science. Recent advance in the fusion of nanomaterial, catalysis, and biochemistry has inspired the development of artificial enzymes implemented with desired catalytic features of natural enzymes. Herein, we review the redox chemistry of POD and compare its catalytic performance to graphene-based nanomaterials (G-NMs) as POD mimetic nanoenzymes bases on catalytic center, binding site, and carrier function. Based on the viewpoints of stereo chemistry and molecular kinetic and dynamics in heterogeneous system, we evaluate and compare the suitability of different NMs as artificial enzyme constituent. We propose that reevaluates design strategies of graphene-based peroxidase (G-POD) mimetic materials and emphasizes on their selectivity (role as catalytic center, binding site, or carrier) is of uttermost. 相似文献
10.
Polyaniline (PANI)/MIL-88A(Fe) (Px@M88) composites were constructed through a simple one-pot hydrothermal method. The photocatalytic and photo-Fenton activities of Px@M88 composites toward reduction of Cr(VI) and degradation organic pollutants were explored by white light irradiation. PANI, as a conductive polymer, can improve MIL-88A(Fe)’s conductivity and the efficiency of photogenerated e−–h+ pair separation. In the presence of H2O2, a photo-Fenton reaction occured to boost the degradation efficiency of organic pollutants like bisphenol A. In addition, P9@M88 showed excellent recycling and stability in cycling experiments. Finally, a possible reaction mechanism for photocatalytic degradation was proposed and verified by X-ray photoelectron spectroscopy and electron spin resonance determination and electrochemical characterizations. 相似文献