全文获取类型
收费全文 | 4027篇 |
免费 | 657篇 |
国内免费 | 505篇 |
专业分类
化学 | 3100篇 |
晶体学 | 45篇 |
力学 | 232篇 |
综合类 | 39篇 |
数学 | 419篇 |
物理学 | 1354篇 |
出版年
2024年 | 11篇 |
2023年 | 112篇 |
2022年 | 120篇 |
2021年 | 182篇 |
2020年 | 216篇 |
2019年 | 194篇 |
2018年 | 179篇 |
2017年 | 116篇 |
2016年 | 245篇 |
2015年 | 212篇 |
2014年 | 245篇 |
2013年 | 289篇 |
2012年 | 380篇 |
2011年 | 427篇 |
2010年 | 255篇 |
2009年 | 285篇 |
2008年 | 282篇 |
2007年 | 226篇 |
2006年 | 195篇 |
2005年 | 156篇 |
2004年 | 118篇 |
2003年 | 98篇 |
2002年 | 93篇 |
2001年 | 67篇 |
2000年 | 70篇 |
1999年 | 66篇 |
1998年 | 55篇 |
1997年 | 47篇 |
1996年 | 62篇 |
1995年 | 34篇 |
1994年 | 36篇 |
1993年 | 23篇 |
1992年 | 18篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1974年 | 1篇 |
1957年 | 3篇 |
排序方式: 共有5189条查询结果,搜索用时 823 毫秒
111.
112.
Jiancong Du Suhui Deng Shangguo Hou Lingling Qiao Jianfang Chen Qing Huang Chunhai Fan Ya Cheng Yun Zhao 《中国光学快报(英文版)》2014,12(4):41101-38
DNA tetrahedral nanostructures are considered to be uew nanocarriers because they can be precisely controlled and hold excellent penetration ability to the cellular membrane. Although the DNA tetrahedral nanostructure is extensively studied in biology and medicine, its behavior in the cells with nanoscale resolution is not understood clearly. In this letter, we demonstrate superrcsolution fluorescence imaging of the distribution of DNA tetrahedral nanostructures in the cell with a simulated emission depletion (STED) microscope, which is built based on a conventional eonfocal microscope and can t)rovide a resolution of 70 nm. 相似文献
113.
Yuying Qu Yingchun Li Xiaoli Tan Weixiang Zhai Dr. Guifang Han Dr. Jingli Hou Prof. Guoquan Liu Prof. Yuguang Song Prof. Yangping Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(33):7888-7895
Tetrathiatriarylmethyl (TAM, trityl) radicals have found wide applications as spin probes/labels for EPR spectroscopy and imaging, and as polarizing agents for dynamic nuclear polarization. The high hydrophilicity of TAM radicals is essential for their biomedical applications. However, the synthesis of hydrophilic TAM radicals (e.g., OX063) is extremely challenging and has only been reported in the patent literature, to date. Herein, an efficient synthesis of a highly water-soluble TAM radical bis(8-carboxyl-2,2,6,6-tetramethylbenzo[1,2-d:4,5-d′]bis([1,3]dithiol-4-yl)-mono-(8-carboxyl-2,2,6,6-tetrakis(2-hydroxyethyl)benzo[1,2-d:4,5-d′]bis([1,3]dithiol-4-yl)methyl (TFO), which contains four additional hydroxylethyl groups, relative to the Finland trityl radical CT-03, is reported. Similar to OX063, TFO exhibits excellent properties, including high water solubility in phosphate buffer, low log P, low pKa, long relaxation times, and negligible binding with bovine serum albumin. On the other hand, TFO has a sharper EPR line and higher O2 sensitivity than those of OX063. Therefore, in combination with its facile synthesis, TFO should find wide applications in magnetic resonance related fields and this synthetic approach would shed new light on the synthesis of other hydrophilic TAM radicals. 相似文献
114.
Muhammad Arsalan Xiujuan Qiao Azka Awais Yahui Wang Shuying Yang Qinglin Sheng Tianli Yue 《Electroanalysis》2021,33(6):1528-1538
The simple and effective method for the novel synthesis of Pt-based nanoparticle was presented with high efficiency. The sensitive catalyst for the simultaneous detection of catechol and hydroquinone was prepared by depositing ternary metal complex on fluorine-doped tin-oxide (FTO). The composition and morphology of nanomaterials were characterized by TEM, HRTEM, XRD, XPS, and EDS (energy dispersive spectroscopy). The size of the Pt-based nanomaterial was about 5±1 nm. The electrochemical performance of the modified catalyst was studied by CV, DPV, and EIS. The modified PtNiCu@FTO catalyst possessed good electro-oxidation activity for hydroquinone and catechol and used for simultaneous detection of catechol and hydroquinone at scan rate of 20 mV s−1 (vs. Ag/AgCl). Detection responses were found in the ranges of 5–2900 μM for hydroquinone and 5–3000 μM for catechol. The detection limits (LOD) for HQ and CC were observed as 0.35 and 0.29 μM, respectively. The sensitivity of HQ and CC were 1515.55 and 1485 μA mM−1 cm−2, respectively. The prepared nanomaterial were effectively applied for the determination of CC and HQ in real samples. 相似文献
115.
Qianqian Sun Yuwei Long Hongxi Li Shuang Pan Jidong Yang Shaopu Liu Xiaoli Hu 《Journal of fluorescence》2018,28(2):523-531
Caffeic acid (CA), a familiar color stabilizing reagent, has aroused general concern due to its uncontrolled addition, and thus the detection of CA is increasingly important. In our report, the bright carbon dots (CDs) were prepared via hydrothermal treatment with urea and citric acid act as raw material and their characteristics were discussed through X-ray diffraction (XRD), transmission electron microscopy (TEM) and so on. Impressively, the strong emission of the as-prepared CDs (Quantum Yield: 24.3%) decreased sharply upon a full reaction with the added CA. Hence, we first present an improved strategy for determining CA based upon the quenching of the strong emission of CDs. In this strategy, 0.79–100.0 µmol L??1 caffeic acid could be simply detected, and a detection limit of 0.24 µmol L??1 was allowed. Additionally, CA in red wine samples can be successfully detected by this method and the exploration of the quenching mechanism of the CA-CDs system was done. 相似文献
116.
Wei Zhou Xiangning Fang Qinglong Qiao Wenchao Jiang Yue Zhang Zhaochao Xu 《中国化学快报》2021,32(2):943-946
With the development of single-molecule detection and super-resolution fluorescence imaging, rhodamine dyes gain new life. Through the modification of the N-substituents and the replacement of the oxygen atom in xanthene, the wavelength and brightness can be effectively changed. However, the spectra of rhodamine, especially due to the balance between ring-closed non-fluorescent lactone and ring-opened fluorescent zwitterion/cation, are sensitive to interference from various environmental factors. In this way, the spectral data of various rhodamines reported by different research groups under different test conditions lacked comparability, sometimes even lacked accuracy. In order to meet the requirements for the accuracy and uniformity of spectral data in the research of single molecule imaging and dye structure-fluorescence relationship study, we have tested the spectra of fifteen rhodamine dyes that cover the visible and near-infrared regions under exactly the same conditions. By studying the dependence of the spectra on dye concentrations, it was confirmed that 1 μmol/L was ideal for detection less from the interference of dye molecule aggregation. We provide comprehensive and reliable spectral data of these fifteen dyes, which are expected to be used as references for future research. And the direct comparison of different rhodamine spectra would help to understand the structure-fluorescence relationship of rhodamines. 相似文献
117.
118.
In this paper, the nonlinear dynamical behavior of two coupled pipes conveying pulsating fluid is studied. The connection between the two pipes is considered as a distributed linear spring. Based on this consideration, the equations of motion of the coupled two-pipe system are obtained. The two coupled nonlinear partial differential equations, discretized using the fourth- order Galerkin method, are solved by a fourth-order Runge-Kutta integration algorithm. Results show that the connection stiffness has a significant effect on the dynamical behavior of the coupled system. It is found that for some parameter values the motion types of the two pipes might be synchronous. 相似文献
119.
120.
Qiao Wang Lefan Li Zongjin Li Siyao Guo Guoxing Sun 《Journal of Polymer Science.Polymer Physics》2019,57(11):713-721
It remains challenging to satisfy the combined performances for hydrogels with excellent mechanical behavior, high deformability, and super recoverability under harsh environmental conditions. In this study, we first established a strong polymer network via the crosslinking of polymer chains on the surfaces of sub‐5‐nm calcium hydroxide nanospherulites in ethylene glycol solvent. The organic gel expressed excellent mechanical properties such as a recoverable compressive engineering stress of 249 MPa and an elongation stress of 402 KPa, which was attributed to the uniform nanosized crosslinking structure as characterized by SEM. Moreover, the nonvolatile solvent remained in the gel, meaning that the sample can resist a wide temperature range of ?56 to 100 °C without losing the elastic properties. This novel organic gel could provide promising routes to develop the ideal elastic carriers for wearable devices, smart skin sensors, and damping materials. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 713–721 相似文献