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91.
A simple folded-cavity used for intracavity frequency-doubled Nd:YVO4 laser was analyzed by transmission matrix and numerical calculation. We have selected a set of proper cavity parameters which can be used readily by operating at high power levels with low threshold, high efficiency, and wide dynamic operating range. 5.6-W TEM00 green laser has been obtained at a 22-W pumping power and with an optical–optical conversion efficiency of 25.5%. 相似文献
92.
飞秒激光脉冲诱导透明介质的非线性吸收和折射率改变轮廓研究 总被引:11,自引:11,他引:0
实验研究了飞秒激光脉冲诱导熔融石英的非线性吸收特性,利用激光诱导自由电子等离子体浓度取决于多光子吸收系数和入射光强的关系;数值模拟了激光诱导折射率变化区域的大小,结合非线性吸收机理和飞秒激光脉冲与介质的相互作用,解释了飞秒激光脉冲超精细加工不受衍射极限的约束,可实现纳米级加工的机理结果表明,电介质的电离能越大,飞秒脉冲诱导的折射率变化区域就越小,但要求的激光脉冲能量也越大;为飞秒激光脉冲超精细加工的材料和激光参量选择提供了理论依据. 相似文献
93.
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95.
CeO2-TiO2复合氧化物的制备、表征及其对CO氧化的催化性能 总被引:1,自引:0,他引:1
采用溶胶-凝胶法制备了一系列不同n(Ce)/n(Ti)的CeO2-TiO2复合氧化物,对复合氧化物的物相结构、形貌特征、比表面积和氧化还原性质进行了表征,并考察了复合氧化物对CO氧化反应的催化性能.结果表明,n(Ce)/n(Ti)>0.10时,复合氧化物为无定形结构;n(Ce)/n(Ti)=0.10~0.30时,复合氧化物失去CeO2和TiO2各自的特征,形成CeO2-TiO2固溶体,具有较大的比表面积.CeO2-TiO2复合氧化物本身对CO氧化反应的催化活性不如TiO2或CeO2的高,但Pd/CeO2-TiO2比Pd/TiO2或Pd/CeO2具有更高的催化活性. 相似文献
96.
A novel organocatalytic asymmetric tandem Michael-Henry reaction catalyzed by 9-amino-9-deoxyepiquinine (VI) has been developed. The reaction was efficiently catalyzed by catalyst VI to give highly functionalized cyclohexanes with four stereogenic carbons including two quaternary stereocenters in excellent enantioselectivities (97 to >99% ee) and high diastereoselectivities (93:7-99:1 dr). Thus, the first organocatalytic asymmetric Henry reaction of common ketones as acceptors is shown. 相似文献
97.
Prof. Xin Wang Dr. Xiaomin Zhang Yan Zhao Dr. Dan Luo Prof. Lingling Shui Yebao Li Dr. Ge Ma Yaojie Zhu Dr. Yongguang Zhang Prof. Guofu Zhou Prof. Aiping Yu Prof. Zhongwei Chen 《Angewandte Chemie (International ed. in English)》2023,62(42):e202306901
The sluggish sulfur redox kinetics and shuttle effect of lithium polysulfides (LiPSs) are recognized as the main obstacles to the practical applications of the lithium-sulfur (Li−S) batteries. Accelerated conversion by catalysis can mitigate these issues, leading to enhanced Li−S performance. However, a catalyst with single active site cannot simultaneously accelerate multiple LiPSs conversion. Herein, we developed a novel dual-defect (missing linker and missing cluster defects) metal–organic framework (MOF) as a new type of catalyst to achieve synergistic catalysis for the multi-step conversion reaction of LiPSs. Electrochemical tests and first-principle density functional theory (DFT) calculations revealed that different defects can realize targeted acceleration of stepwise reaction kinetics for LiPSs. Specifically, the missing linker defects can selectively accelerate the conversion of S8→Li2S4, while the missing cluster defects can catalyze the reaction of Li2S4→Li2S, so as to effectively inhibit the shuttle effect. Hence, the Li−S battery with an electrolyte to sulfur (E/S) ratio of 8.9 mL g−1 delivers a capacity of 1087 mAh g−1 at 0.2 C after 100 cycles. Even at high sulfur loading of 12.9 mg cm−2 and E/S=3.9 mL g−1, an areal capacity of 10.4 mAh cm−2 for 45 cycles can still be obtained. 相似文献
98.
Guofu Zhang Xuefei Luo Chenfei Guan Yin Cui Prof. Chengrong Ding 《European journal of organic chemistry》2023,26(17):e202300114
Multimetallic catalysis can effectively enhance the selectivity for the heterocoupling product over homocoupling products in cross-electrophilic couplings. We report the selective cross-coupling of aryl bromides with aryl fluorosulfonates via palladium and nickel cooperative catalysis for the synthesis of biaryls, which can be carried out at room temperature while having marvelous chemoselectivity. In addition, the reaction also has a good performance on the gram-scale reaction. 相似文献
99.
A new series of amidolanthanides have been prepared from the reactions between Ln[N(SiMe3)2]3 and the chiral NNO ligands, (S)-2-(pyrrol-2-ylmethyleneamino)-2'-hydroxy-6,6'-dimethyl-1,1'-biphenyl (2H2) and (S)-5,5',6,6',7,7',8,8'-octahydro-2-(pyrrol-2-ylmethyleneamino)-2'-hydroxy-1,1'-binaphthyl (3H2), which are synthesized from the condensation of pyrrole-2-carboxaldehyde with 1 equiv of (S)-2-amino-2'-hydroxy-6,6'-dimethyl-1,1'-biphenyl or (S)-5,5',6,6',7,7',8,8'-octahydro-2-amino-2'-hydroxy-1,1'-binaphthyl, in the presence of molecular sieves at 70 degrees C, respectively. Treatment of 2H2 with 1 equiv of Ln[N(SiMe3)2]3 (Ln=Sm, Yb) in toluene under reflux, followed by recrystallization from a toluene solution, gives the dimeric amido complexes, {2-SmN(SiMe3)2}2.0.5C7H8 (6.0.5C7H8) and {2-YbN(SiMe3)2} 2.1.5C7H8(8.1.5C7H8), in good yields. While under similar reaction conditions, the reaction of 2H2 with 1 equiv of Y[N(SiMe3)2]3 leads to the isolation of a mixture of {2-YN(SiMe3)2}2 (7a) and {(2)2Y}Y[N(SiMe3)2]2(7b) in 82% total yield; the reaction of 3H2 with 1 equiv of Ln[N(SiMe3)2]3 (Ln=Y, Yb) gives the trinuclear complexes, {(3)2Ln}2LnN(SiMe3) 2.1.5C7H8 (Ln=Y(9.1.5C7H8), Yb(10.1.5C7H8)), in good yields. All compounds have been characterized by various spectroscopic techniques and elemental analyses. The solid-state structures of compounds 2H2 and 6- 10 have been further confirmed by X-ray diffraction analyses. Complexes 6- 9 are active catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in good yields with moderate ee values. 相似文献
100.
Guofu Ma Zhiguo Zhang Hui Peng Kanjun Sun Feitian Ran Ziqiang Lei 《Journal of Solid State Electrochemistry》2016,20(6):1613-1623
In this work, the micromolecule l-glutamic acid (Glu) is employed as nitrogen-rich precursor to prepare a novel porous carbon, and ZnCl2 is used as activating agent to improve the surface area and electrochemical performance of the carbon. The nitrogen content of the carbon (Glu-2.5) prepared by Glu and ZnCl2 with a mass ratio of 1:2.5 retains as high as 7.1 % at an activation temperature of 700 °C. The surface area and pore volume of Glu-2.5 are 1007.4 m2 g?1 and 0.57 cm3 g?1, respectively. Glu-2.5 exhibits a high specific capacitance of 330.6 F g?1 in 2 M KOH electrolyte at the current density of 1 A g?1and good cycling stability (89 % retention of capacitance after 5000 charge/discharge cycles). More importantly, the assembled symmetric supercapacitor using Glu-2.5 as electrodes reveals a high energy density (16.7 Wh kg?1) under the power density of 404.7 W kg?1. Owing to its inherent advantages, Glu-2.5 could be a promising and scalable alternative applied to energy storage/conversion. 相似文献