全文获取类型
收费全文 | 1293篇 |
免费 | 126篇 |
国内免费 | 112篇 |
专业分类
化学 | 825篇 |
晶体学 | 28篇 |
力学 | 61篇 |
综合类 | 6篇 |
数学 | 208篇 |
物理学 | 403篇 |
出版年
2023年 | 18篇 |
2022年 | 31篇 |
2021年 | 36篇 |
2020年 | 32篇 |
2019年 | 35篇 |
2018年 | 38篇 |
2017年 | 32篇 |
2016年 | 41篇 |
2015年 | 50篇 |
2014年 | 73篇 |
2013年 | 97篇 |
2012年 | 96篇 |
2011年 | 104篇 |
2010年 | 66篇 |
2009年 | 47篇 |
2008年 | 66篇 |
2007年 | 68篇 |
2006年 | 74篇 |
2005年 | 46篇 |
2004年 | 51篇 |
2003年 | 33篇 |
2002年 | 29篇 |
2001年 | 28篇 |
2000年 | 28篇 |
1999年 | 28篇 |
1998年 | 22篇 |
1997年 | 20篇 |
1996年 | 18篇 |
1995年 | 22篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 21篇 |
1979年 | 6篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1972年 | 4篇 |
1969年 | 4篇 |
排序方式: 共有1531条查询结果,搜索用时 927 毫秒
991.
In this paper,thermoexpandable polymeric microspheres were prepared by suspension polymerization with acrylonitrile(AN) and methyl methacrylate(MMA) as monomers and i-butane as a blowing agent.The micromorphology and thermal stability were researched by polarized microscopy and TGA.The diameter of the expandable microspheres increased from about 20 mm(unexpanded) to 40–80 mm(expanded) upon heating.The maximum expansion volume was higher than 22 times of the original volume and the density of the expanded microspheres was about 16.7 kg/m3.The blowing agent content in microspheres was about 20 wt% and To.e.,Tm.e.and To.s.were 80 8C,120–130 8C and 140–145 8C,respectively. 相似文献
992.
A Reliable Aerosol‐Spray‐Assisted Approach to Produce and Optimize Amorphous Metal Oxide Catalysts for Electrochemical Water Splitting 下载免费PDF全文
Long Kuai Jing Geng Changyu Chen Erjie Kan Yadong Liu Qing Wang Prof. Dr. Baoyou Geng 《Angewandte Chemie (International ed. in English)》2014,53(29):7547-7551
An aerosol‐spray‐assisted approach (ASAA) is proposed and confirmed as a precisely controllable and continuous method to fabricate amorphous mixed metal oxides for electrochemical water splitting. The proportion of metal elements can be accurately controlled to within (5±5) %. The products can be sustainably obtained, which is highly suitable for industrial applications. ASAA was used to show that Fe6Ni10Ox is the best catalyst among the investigated Fe‐Ni‐Ox series with an overpotential of as low as 0.286 V (10 mA cm?2) and a Tafel slope of 48 mV/decade for the electrochemical oxygen evolution reaction. Therefore, this work contributes a versatile, continuous, and reliable way to produce and optimize amorphous metal oxide catalysts. 相似文献
993.
Self‐Assembly of Fullerene‐Based Janus Particles in Solution: Effects of Molecular Architecture and Solvent 下载免费PDF全文
Zhiwei Lin Pengtao Lu Chih‐Hao Hsu Dr. Kan Yue Dr. Xue‐Hui Dong Hao Liu Kai Guo Prof. Chrys Wesdemiotis Dr. Wen‐Bin Zhang Dr. Xinfei Yu Prof. Stephen Z. D. Cheng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(37):11630-11635
Two molecular Janus particles based on amphiphilic [60]fullerene (C60) derivatives were designed and synthesized by using the regioselective Bingel–Hirsh reaction and the click reaction. These particles contain carboxylic acid functional groups, a hydrophilic fullerene (AC60), and a hydrophobic C60 in different ratios and have distinct molecular architectures: 1:1 (AC60–C60) and 1:2 (AC60–2C60). These molecular Janus particles can self‐assemble in solution to form aggregates with various types of micellar morphology. Whereas vesicular morphology was observed for both AC60–C60 and AC60–2C60 in tetrahydrofuran, in a mixture of N,N‐dimethylformamide (DMF)/water, spherical micelles and cylindrical micelles were observed for AC60–C60 and AC60–2C60, respectively. A mechanism of formation was tentatively proposed based on the effects of molecular architecture and solvent polarity on self‐assembly. 相似文献
994.
Crosslinked x-P(St-MAA) seed latex was first prepared via soap-free emulsion copolymerization of styrene (St) and methyl methacrylic acid (MAA) with divinyl benzene as crosslinker and ammonium persulfate as initiator, and x-P(St-MAA)/x-P(St-NaSS) core/shell latex particles were then synthesized through a novel seeded emulsion copolymerization of St and sodium styrene sulphonate (NaSS) in the presence of water-soluble crosslinker N,N′-methylene bisacrylamide (BAA) using oil-soluble 2,2-azobis isobutyronitrile as initiator. TEM observation indicated that narrow dispersed core/shell latex particles were obtained, and element analysis showed that NaSS unit content in the whole particle and in the shell reached 22.8 wt% and 51.2 wt%, respectively. 相似文献
995.
996.
Mercury(II) Chloride‐Mediated Desulphurization of Amidinothioureas: Synthesis and Antimicrobial Activity of 3‐Amino‐1,2,4‐triazole Derivatives 下载免费PDF全文
Swapnil G. Yerande Chetna D. Baviskar Kiran M. Newase Wei Wang Kan Wang Alexander Dömling 《Journal of heterocyclic chemistry》2014,51(6):1883-1887
The synthesis of 3‐amino‐1,2,4‐triazole via mercury(II) chloride‐mediated cyclization of amidinothiourea is described. This procedure offers a general and efficient route to synthesize the title compound by 3 + 2 annulation reaction. On the basis of the literature precedence, the mechanism for the formation of 3‐amino‐1,2,4‐triazole is proposed. When the synthesized compounds were tested for their antimicrobial activity showed promising inhibition against tested microbes. 相似文献
997.
Efficient Dynamic Nuclear Polarization at 800 MHz/527 GHz with Trityl‐Nitroxide Biradicals 下载免费PDF全文
Dr. Guinevere Mathies Dr. Marc A. Caporini Dr. Vladimir K. Michaelis Prof. Yangping Liu Dr. Kan‐Nian Hu Deni Mance Prof. Jay L. Zweier Dr. Melanie Rosay Prof. Marc Baldus Prof. Robert G. Griffin 《Angewandte Chemie (International ed. in English)》2015,54(40):11770-11774
Cross‐effect (CE) dynamic nuclear polarization (DNP) is a rapidly developing technique that enhances the signal intensities in magic‐angle spinning (MAS) NMR spectra. We report CE DNP experiments at 211, 600, and 800 MHz using a new series of biradical polarizing agents referred to as TEMTriPols, in which a nitroxide (TEMPO) and a trityl radical are chemically tethered. The TEMTriPol molecule with the optimal performance yields a record 1H NMR signal enhancement of 65 at 800 MHz at a concentration of 10 mM in a glycerol/water solvent matrix. The CE DNP enhancement for the TEMTriPol biradicals does not decrease as the magnetic field is increased in the manner usually observed for bis‐nitroxides. Instead, the relatively strong exchange interaction between the trityl and nitroxide moieties determines the magnetic field at which the optimum enhancement is observed. 相似文献
998.
999.
在二维单介质磁驱动数值模拟程序(MDSC2)的基础上,采用局部结构整体非结构的网格拼接方法,研制了处理滑移界面的二维多介质程序。二维多介质程序解决了单介质程序无法处理的电极与飞片之间相互作用的模拟问题,能更准确地模拟磁驱动发射实验的飞片状态。计算结果表明:发射飞片的自由面部分始终保持固体密度状态;自由面速度历史和VISAR测量的速度曲线相吻合;飞片中间部分在电流加载过程中始终具有良好的平面性,飞片两端出现拖尾质量,产生不稳定性,这是由于飞片两端与飞片中间部分的磁场强度分布不同造成的。 相似文献
1000.
Hydrogen‐bonding characteristics and unique ring‐opening polymerization behavior of Ortho‐methylol functional benzoxazine 下载免费PDF全文
Kan Zhang Pablo Froimowicz Lu Han Hatsuo Ishida 《Journal of polymer science. Part A, Polymer chemistry》2016,54(22):3635-3642
Monofunctional benzoxazine with ortho‐methylol functionality has been synthesized and highly purified. The chemical structure of the synthesized monomer has been confirmed by 1H and 13C nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FT‐IR) and elemental analysis. One‐dimensional (1D) 1H NMR is used with respect to varied concentration of benzoxazines to study the specific nature of hydrogen bonding in both ortho‐methylol functional benzoxazine and its para counterpart. The polymerization behavior of benzoxazine monomer has been also studied by in situ FT‐IR and differential scanning calorimetry, experimentally supporting the polymerization mechanism of ortho‐methylol functional benzoxazine we proposed before. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3635–3642 相似文献