全文获取类型
收费全文 | 341篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 235篇 |
晶体学 | 7篇 |
力学 | 4篇 |
数学 | 21篇 |
物理学 | 84篇 |
出版年
2023年 | 4篇 |
2022年 | 3篇 |
2020年 | 2篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2017年 | 10篇 |
2016年 | 11篇 |
2015年 | 10篇 |
2014年 | 7篇 |
2013年 | 15篇 |
2012年 | 27篇 |
2011年 | 26篇 |
2010年 | 18篇 |
2009年 | 16篇 |
2008年 | 18篇 |
2007年 | 23篇 |
2006年 | 19篇 |
2005年 | 27篇 |
2004年 | 20篇 |
2003年 | 20篇 |
2002年 | 16篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 6篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有351条查询结果,搜索用时 0 毫秒
201.
202.
Susumu Saito Masahito Shiozawa Hisashi Yamamoto 《Angewandte Chemie (International ed. in English)》1999,38(12):1769-1771
The combined use of aluminum tris(2,6-diphenylphenoxide) (ATPH) and lithium 2,2,6,6-tetramethylpiperidide (LTMP) has proven to be effective for the mixed crossed aldol condensation between conjugated esters and various aldehydes. An example is shown in Equation (1). 相似文献
203.
Hajime Yasuda Eiji Ihara Masakazu Morimoto Mitsufumi Nodono Shiro Yoshioka Masahito Furo 《Macromolecular Symposia》1995,95(1):203-216
Organolanthanide (III) initiated polymerization of alkyl acrylates gave high molecular weight poly(alkyl acrylate)s with extremely narrow molecular weight distribution in high yield. Molecular weight of the polymers increased linearly with the conversion. Random and block copolymerizations of acrylate monomers (alkyl acrylates and MMA) were successful. For development of olefin polymerization catalystsbased on lanthanide complexes, bulky substituents were introduced into Me2Si bridged Cp rings and they were used as ligands of lanthanide complexes. Tri- and divalent lanthanide complexes with such a ligand system showed high activity for olefin polymerization and gave high molecular weight polyolefins. 相似文献
204.
Yasumasa Kanekiyo Masahito Sano Ritsuko Iguchi Seiji Shinkai 《Journal of polymer science. Part A, Polymer chemistry》2000,38(8):1302-1310
Hydrogels comprised of boronic acid monomer (3), cationic monomer (4), and crosslinker monomer (5) were prepared by radical copolymerization. These hydrogels could efficiently bind nucleotides such as AMP and ATP by a cooperative action of the boronic acid‐cis‐diol complexation and the electrostatic interaction between the cationic unit and the phosphate group. The binding processes were conveniently monitored by the swelling and deswelling behaviors of these hydrogels in aqueous solution. For the hydrogel with the specific monomer composition an interesting “charge inversion” was observable: with increasing AMP or ATP concentration, the cation‐rich hydrogel was gradually charge neutralized, once shrunken at the neutral stage, and then swollen again because of the anion‐rich charge state. These nucleotide‐induced swelling and deswelling phenomena were reproduced on the gold surface of a QCM resonator. Therefore, the present system is not only interesting to consider nucleotide‐induced mechanochemical properties, but also applicable as a sensor to the nucleotide detection. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1302–1310, 2000 相似文献
205.
Kodama T Ueda M Nakamuro Y Shimizu K Komarneni S 《Langmuir : the ACS journal of surfaces and colloids》2004,20(12):4920-4925
The cation exchange properties of alkali and alkaline earth metal cations at room temperature were investigated on an ultrafine, highly charged Na-4-mica (with the ideal mica composition Na4Mg6Al4Si4O20F4.xH2O). Ultrafine mica crystallites of 200 nm in size led to faster Sr2+ uptake kinetics in comparison to larger mica crystallites. The alkali metal ion (K+, Cs+, and Li+) exchange uptake was rapid, and complete exchange occurred within 30 min. For the alkaline earth metal ions Ba2+, Ca2+, and Mg2+, however, the exchange uptake required lengthy periods from 3 days to 4 weeks to be completed, similar to its Sr uptake, as previously reported. Kinetic models of the modified Freundlich and parabolic diffusion were examined for the experimental data on the Ba2+, Ca2+, and Mg2+ uptakes. The modified Freundlich model described well the Ba2+ ion uptake kinetics as well as that for the Sr2+ ion, while for the Ca2+ and Mg2+ ions the parabolic diffusion model showed better fitting. The alkali and alkaline earth ion exchange isotherms were also determined in comparison to the Sr2+ exchange isotherm. The thermodynamic equilibria for these cations were compared by using Kielland plots evaluated from the isotherms. 相似文献
206.
Exposure of 1-alkenyl(phenyl)- and 1-alkynyl(phenyl)-λ3-iodanes to THF at room temperature in the presence of a catalytic amount of trialkylborane results in smooth reduction to give 1-iodo-1-alkenes and 1-iodo-1-alkynes as major products, respectively. The key step in the reductions probably involves a single-electron transfer from α-tetrahydrofuryl radical to the λ3-iodanes, which generates the labile [9-I-2] iodanyl radicals. 相似文献
207.
M Kodera Y Kawahara Y Hitomi T Nomura T Ogura Y Kobayashi 《Journal of the American Chemical Society》2012,134(32):13236-13239
The conversion of peroxodiiron(III) to high-spin S = 2 oxodiiron(IV) via reversible O-O bond scission in a diiron complex with a bis-tpa dinucleating ligand, 6-hpa, has been characterized by elemental analysis; kinetic measurements for alkene epoxidation; cold-spray ionization mass spectrometry; and electronic absorption, M?ssbauer, and resonance Raman spectroscopy to gain insight into the O(2) activation mechanism of soluble methane monooxygenases. This is the first synthetic example of a high-spin S = 2 oxodiiron(IV) species that oxidizes alkenes to epoxides efficiently. The bistability of the peroxodiiron(III) and high-spin S = 2 oxodiiron(IV) moieties is the key feature for the reversible O-O bond scission. 相似文献
208.
Kazuaki Ito Ryosuke Nomura Takuya Fujii Masahito Tanaka Tomoaki Tsumura Hiroyuki Shibata Takeshi Hirokawa 《Analytical and bioanalytical chemistry》2012,404(8):2513-2517
A method was developed for determination of inorganic anions, including nitrite (NO 2 ? ), nitrate (NO 3 ? ), bromide (Br?), and iodide (I?), in seawater by ion chromatography (IC). The IC system used two dilauryldimethylammonium bromide (DDAB)-coated monolithic ODS columns (50?×?4.6?mm i.d. and 100?×?4.6?mm i.d.) connected in series for separation of the ions. Aqueous NaCl (0.5?mol/L; flow rate, 3?mL/min) containing 5?mmol/L phosphate buffer (pH 5) was used as the eluent, and detection was with a UV detector at 225?nm. The monolithic ODS columns were coated and equilibrated with a 1-mmol/L DDAB solution (in H2O/methanol, 90:10 v/v). The hydrophilic ions (NO 2 ? , NO 3 ? , and Br?) were separated within 3?min and the retention time of I? was 16?min. No interferences from matrix ions, such as chloride and sulfate ions, were observed in 35?‰ artificial seawater. The detection limits were 0.6?μg/L for NO 2 ? , 1.1?μg/L for NO 3 ? , 70?μg/L for Br?, and 1.6?μg/L for I? with a 200-μL sample injection. The performance of the coated columns was maintained without addition of DDAB in the eluent. The IC system was successfully applied to real seawater samples with recovery rates of 94–108?% for all ions. Figure
The hydrophilic ions (NO 2 ? , NO 3 ? , and Br?) and I? in seawater was determined by a single run using the IC system consisting of two dilauryldimethylammonium bromide (DDAB)-coated monolithic ODS columns (50?×?4.6?mm i.d. and 100?×?4.6?mm i.d.) connected in series, NaCl (0.5?mol/L; flow rate, 3?mL/min) containing 5?mmol/L phosphate buffer (pH 5) as the eluent, and a UV detector (225?nm). No interferences from matrix ions, such as chloride and sulfate ions, were observed in 35?‰ artificial and real seawaters. 相似文献
209.
A rapid and novel ultra-HPLC (u-HPLC) method for the determination of vitamins A (retinol) and E (alpha-, gamma-, and delta-tocopherol) in foods was validated in terms of its precision, accuracy, and linearity. The u-HPLC separation was performed on an RP C18 column (particle size 2 microm, id 2 mm, and length 75 mm), followed by fluorescence detection. The recovery of retinol was more than 84.58%; the LOD and LOQ of the u-HPLC analysis were 0.015 and 0.045 mg/kg, respectively. The intraday and interday precision was less than 9.12%. The recoveries of alpha-, gamma-, and delta-tocopherol were more than 81.37%; the LOD and the LOQ were 0.014, 0.002, and 0.001 mg/kg and 0.042, 0.005, and 0.004 mg/kg, respectively. All calibration curves had good linearity (r2 = 0.99) within the test ranges. The novel, rapid method coupled to u-HPLC can provide significant improvements in the speed, sensitivity, and resolution compared with a conventional HPLC method. 相似文献
210.
Ochiai M Yamane S Hoque MM Saito M Miyamoto K 《Chemical communications (Cambridge, England)》2012,48(43):5280-5282
Hypervalent N-triflylimino-λ(3)-bromane undergoes direct and regioselective α-C-H amination of ethers at room temperature under transition metal-free conditions. Kinetic results, substituent and deuterium isotope effects suggest an asynchronous concerted organonitrenoid transition state with some hydride transfer character, analogous to that for alkane C-H insertions. 相似文献