全文获取类型
收费全文 | 3757篇 |
免费 | 158篇 |
国内免费 | 54篇 |
专业分类
化学 | 2109篇 |
晶体学 | 58篇 |
力学 | 175篇 |
综合类 | 16篇 |
数学 | 769篇 |
物理学 | 842篇 |
出版年
2023年 | 29篇 |
2022年 | 50篇 |
2021年 | 69篇 |
2020年 | 100篇 |
2019年 | 97篇 |
2018年 | 142篇 |
2017年 | 130篇 |
2016年 | 181篇 |
2015年 | 138篇 |
2014年 | 179篇 |
2013年 | 379篇 |
2012年 | 239篇 |
2011年 | 244篇 |
2010年 | 256篇 |
2009年 | 165篇 |
2008年 | 232篇 |
2007年 | 205篇 |
2006年 | 150篇 |
2005年 | 112篇 |
2004年 | 84篇 |
2003年 | 84篇 |
2002年 | 99篇 |
2001年 | 82篇 |
2000年 | 57篇 |
1999年 | 36篇 |
1998年 | 43篇 |
1997年 | 38篇 |
1996年 | 35篇 |
1995年 | 17篇 |
1994年 | 23篇 |
1993年 | 14篇 |
1992年 | 12篇 |
1991年 | 14篇 |
1990年 | 15篇 |
1989年 | 17篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1984年 | 18篇 |
1983年 | 14篇 |
1981年 | 15篇 |
1980年 | 17篇 |
1979年 | 8篇 |
1978年 | 11篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1975年 | 8篇 |
1974年 | 8篇 |
1964年 | 8篇 |
排序方式: 共有3969条查询结果,搜索用时 15 毫秒
111.
Oğuz Türünç Michael A. R. Meier 《Journal of polymer science. Part A, Polymer chemistry》2012,50(9):1689-1695
The ability of thiyl radicals to add to terminal unsaturations in an efficient way made them considered being one of the click reactions. Recently, thiol‐yne addition reactions have been used extensively for the synthesis of crosslinked networks and dendrimers and postpolymerization functionalization protocols. Herein, we report a novel step‐growth type reaction for highly functional linear polymers using a monoalkyne and dithiol compound. First, we investigated the model reaction between 1‐octyne and 1‐octanethiol as well as 1,4‐butanedithiol compounds, which were initiated via self‐, thermal‐, and UV‐initiation; the UV‐initiation was found to be the most efficient method and completed within 2‐h reaction time. The same conditions were applied for the polymerization of four different functional alkynes bearing different functional groups with two dithiol compounds. All polymerizations resulted in highly functional linear polymers with number averaged molecular weights ranging from 5 to 30 kDa, except for propargylic acid and its methyl ester, where only oligomers formed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
112.
A distance based measure of dependence is proposed for stable distributions that completely characterizes independence for a bivariate stable distribution. Properties of this measure are analyzed, and contrasted with the covariation and co-difference. A sample analog of the measure is defined and demonstrated on simulated and real data, including time series and distributions in the domain of attraction of a stable law. 相似文献
113.
114.
Martin Danko Matej Mičušík Mária Omastová Juraj Bujdák Dušan Chorvát Jr. 《Chemical Papers》2014,68(11):1621-1622
115.
116.
Mesoporous chitosan‐immobilized iron tetrakis(4‐carboxyphenyl)porphyrin as a model of cytochrome P‐450 enzyme for oxidation of ethylbenzene
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mesoporous chitosan‐grafted iron tetra (4‐carboxyphenyl) porphyrin catalyst (Fe TCPP/mesp‐CTS) was prepared and investigated as a practical model for the nano‐cavity and coordinate regulation‐catalysis(CRC) function in cytochrome P‐450 enzyme. Fe TCPP/mesp‐CTS was characterized by X‐ray Diffraction (XRD), Thermogravimetry (TG), Ultraviolet–visible spectroscopy(UV‐Vis), Ultraviolet–visible– Diffuse reflectance spectroscopy (UV‐DRS), Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT‐IR), and X‐ray photoelectron spectroscopy (XPS) techniques. The catalytic activity of Fe TCPP/mesp‐CTS for ethylbenzene oxidation was investigated and it was proved to be a better catalyst than Fe TCPP/macp‐CTS based on the ethylbenzene conversion, turnover numbers(TON), and the reusability. These results are attributed to the mesocavity and CRC of amino group in Fe TCPP/mesp‐CTS. The highest ethylbenzene conversion and yields of ketone and alcohol were 24.4% and 18.2%, respectively. 相似文献
117.
118.
Firstly, poly[phenyl thiadiazole methacrylamide-co-divinylbenzene-co-2-acrylamido-2-methylpropane sulfonic acid] (PTMAAm-co-DVB-co-AMPS), a new polymer resin was synthesized. This polymer resin was characterized by elemental analyzer, X-ray diffractometer, scanning electron microscope (SEM) and IR spectrometer. The glass column packed with the synthesized polymer resin was used for solid phase extraction (SPE). At the same time, the analytes were separated and preconcentrated from various water, dried vegetables samples and standard reference material (CRM) with SPE and determined by flame atomic absorption spectrometer (FAAS). The experimental conditions of this method such as pH, flow rates of sample, flow rates of eluent, type / concentration / volume of eluent, sample volume and matrix ions were examined. The limits of detection (µg L?1) were calculated (3s) 0.9 for Mn(II), 1.4 for Cd(II), Co(II) and Zn(II), 1.5 for Cr(III), 2.2. for Cu(II), 1.9 for Pb(II),1.5 for Ni(II) and 1.9 for Fe(III) (n = 21). The low relative standard deviation, ≤ 2% (n = 11) and preconcentration factor as 75 for analytes were obtained. 相似文献
119.
Bünyamin Ak Duygu Elma Nermin Meriç Cezmi Kayan Uğur Işık Murat Aydemir Feyyaz Durap Akın Baysal 《Tetrahedron: Asymmetry》2013,24(20):1257-1264
A new and versatile class of unsymmetrical ferrocenyl-phosphinite ligands possessing a stereogenic center has been prepared from commercially available, inexpensive aminoacids such as, d-, l-phenylglycine and d-, l-phenylalanine, through a concise synthetic procedure. These ligands are not very sensitive to air and moisture, and display good enantioselectivities in the ruthenium-catalyzed asymmetric transfer hydrogenation of acetophenone derivatives, in which up to 91% ee was obtained. A comparison of the catalytic properties of amino alcohols and other analogues based on a ferrocenyl backbone is also discussed briefly. The structures of these ligands and their corresponding complexes have been elucidated by a combination of multinuclear NMR spectroscopy, IR spectroscopy, and elemental analysis. 相似文献
120.
Kristina D. Radosavljević Jelena D. Lović Dušan Ž. Mijin Slobodan D. Petrović Milka B. Jadranin Aleksandar R. Mladenović Milka L. Avramov Ivić 《Chemical Papers》2017,71(7):1217-1224
The electrodegradation of azithromycin was studied by its indirect oxidation using dimensionally stable Ti/RuO2 anode as catalyst in the electrolyte containing methanol, 0.05 M NaHCO3, sodium chloride and deionized water. The optimal conditions for galvanostatic electrodegradation for the azithromycin concentration of 0.472 mg cm?3 were found to be NaCl concentration of 7 mg cm?3 and the applied current of 300 mA. The differential pulse voltammetry using glassy carbon electrode was performed for the first time in the above-mentioned content of electrolyte for the nine concentration of azithromycin (0.075–0.675 mg cm?3) giving the limits of azithromycin detection and of quantification as: LOD 0.044 mg cm?3 and LOQ 0.145 mg cm?3. The calibration curve was constructed enabling the electrolyte analysis during its electrodegradation process. The electrolyte was analyzed by high-performance liquid chromatography and electrospray ionization time-of-flight mass spectrometry. The electrooxidation products were identified and after 180 min there was no azithromycin in the electrolyte while TOC analysis showed that 79% of azithromycin was mineralized. The proposed degradation scheme is presented. 相似文献