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21.
Yinghai Liu Jianping Zhang Rongyue Zhang Weiqi Zhou Shengxian Li 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10):1127-1132
In this article, the graft copolymerization of 4‐vinyl pyridine (4VP) onto nylon‐6 (PA6) using potassium diperiodacuprate (III) (DPC)–PA6 redox system as initiator is investigated in an alkaline medium. The structure and the properties of graft copolymer are confirmed by Fourier transfer infrared spectroscopy (IR), X‐ray diffraction and thermogravimetric analysis (TGA). The mechanism is proposed to explain the generation of radicals and the initiation. The effects of reaction variables, such as the initiator concentration, ratio of 4VP to PA6, pH, as well as reaction temperature and time are investigated. Graft copolymers with high grafting efficiency (>95%) were obtained, which indicated that the DPC–PA6 redox system was an efficient initiator for this graft copolymerization. The quaternized PA6‐g‐P4VP (QPAVP) is proven to be an excellent adsorbent to heavy metal ions. 相似文献
22.
大口径氘化磷酸二氢钾(DKDP)晶体抗激光损伤性能偏低严重地制约着大型高功率激光装置输出水平.本研究利用离线亚纳秒激光预处理技术有效地提升了大口径DKDP晶体抗激光损伤性能.实际使用情况表明,采用离线亚纳秒激光预处理后,DKDP晶体在9 J/cm2激光通量辐照下的表面平均损伤密度得到大幅下降,由未处理前的5.02 pp/cm2(1pp表示1个百分点)降至0.55 pp/cm2,降幅为一个数量级.同时,激光预处理对晶体损伤尺寸具有一定的抑制作用,预处理后晶体损伤点尺寸分布曲线向尺寸减小的方向平移,尺寸分布峰值由预处理前的25μm降至预处理后的18—20μm. 相似文献
23.
Markus Balmer Dr. Florian Weigend Prof. Dr. Carsten von Hänisch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(19):4914-4919
The N-heterocyclic carbene (NHC)-stabilized phosphinidenide, SIMesPK [SIMes=1,3-bis(2,4,6-trimethylphenyl)imidazolidine-2-ylidene], was used as an (NHC)P-transfer reagent for the synthesis of the low-valent Group 14 ate complexes K[(SIMesP)3E] (E=Ge: 2 , Sn: 3 , Pb: 4 ), which were characterized by 1H NMR, 31P NMR, IR spectroscopy as well as elemental and X-ray analysis. Furthermore, SIMesPK was used in reactions with potassium amides and alkoxides to form the molecular phosphorus–potassium clusters [K4(SIMesP)2(hmds)2] [ 5 , hmds=N(SiMe3)2] and [K6(SIMesP)2(OtBu)4] ( 6 ). Finally, the reaction of SIMesPK with Li[Al(OC4F9)4] led to the potassium-rich ionic compound [(SIMesP)4K5][Al(OC4F9)4] ( 7 ). 相似文献
24.
25.
Kentaro Iwasaki Kazunori Umishita Shojun Hino Koichi Kikuchi Yohji Achiba 《Molecular Crystals and Liquid Crystals》2013,570(1):623-628
Abstract Ultraviolet photoelectron spectra of potassium dosed higher fullerenes are measured with a synchrotron radiation light source. Potassium dosing to higher fullerenes brings a new structure between the spectral onset of pristine fullerenes and the Fermi level. As the spectral edge of the new structure does not cross the Fermi level, potassium dosed higher fullerenes are not metallic but semiconductive. When the potassium is excessively dosed to the fullerenes, the lower binding energy structures above 5 eV become faint. In contrast to this phenomenon, four distinct structures appear between 5 and 14 eV. 相似文献
26.
《Mendeleev Communications》2021,31(5):715-717
Nanoporous silicon carbide with a specific surface area of up to 186.45 m2 g−1 has been efficiently synthesized from waste rice husk using a magnesiothermic reduction at 950 °C as a key step. Throughout the entire process, the recovery rates of silicon, potassium and phosphorus from rice husk can reach 88.46, 91.5 and 65.5%, respectively. Turning rice husk waste into a real treasure, this promising method for producing porous SiC protects the environment and brings economic benefits. 相似文献
27.
Studies on different phases in the Y-Ba-Cu-O system have revealed that TC around 90 K is obtainable with different Cu /Cu ratios provided the correct oxygen proportion is maintained. 相似文献
28.
An efficient palladium catalyst was synthesized using nicotine, benzyl chloride and palladium chloride. The structure of this catalyst was characterized and it was then used for the synthesis of diaryl sufides. A variety of diaryl thioethers were synthesized under relatively mild reaction conditions. This protocol avoids foul‐smelling thiols via cross‐coupling of aryl halides with potassium thiocyanate and all substrates give the corresponding products in good to excellent yields in the presence of low amounts of the catalyst. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
29.
Aleksandar Kremenovi Predrag Vuli 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(3):256-259
The X‐ray powder diffraction pattern that corresponds to the disordered state of kalsilite (potassium aluminium orthosilicate), KAlSiO4, is investigated. The directionality of (Al,Si)O4 tetrahedra within single six‐membered tetrahedral ring building units (S6R) could not be defined. With equal probability for the directionality of each tetrahedra within one S6R [free apex pointing up (U) or down (D)], an undefined sequence of U and D directionalities is needed to describe the S6R building units. The extinction conditions of disordered kalsilite are also different compared to ordered kalsilite within the space group P63. In disordered kalsilite, h0l and hhl reflections with l = 2n + 1 are systematically absent. 相似文献
30.
Diana Gonzalez Joseph T. Golab Andrew J. Cigler James A. Kaduk 《Acta Crystallographica. Section C, Structural Chemistry》2020,76(7):706-715
The crystal structures of a new polymorph of dipotassium hydrogen citrate, 2K+·HC6H5O72?, and potassium rubidium hydrogen citrate, K+·Rb+·HC6H5O72?, have been solved and refined using laboratory powder X‐ray diffraction and optimized using density functional techniques. In the new polymorph of the dipotassium salt, KO7 and KO8 coordination polyhedra share corners and edges to form a three‐dimensional framework with channels parallel to the a axis and [111]. The hydrophobic methylene groups face each other in the channels. The un‐ionized carboxylic acid group forms a strong charge‐assisted hydrogen bond to the central ionized carboxylate group. The hydroxy group forms an intermolecular hydrogen bond to a different central carboxylate group. In the potassium rubidium salt, the K+ and Rb+ cations are disordered over two sites, in approximately 0.72:0.28 and 0.28:0.72 ratios. KO8 and RbO9 coordination polyhedra share corners and edges to form a three‐dimensional framework with channels parallel to the a axis. The un‐ionized carboxylic acid group forms a strong charge‐assisted hydrogen bond to an ionized carboxylate group. The hydroxy group forms an intermolecular hydrogen bond to the central carboxylate group. Density functional theory (DFT) calculations on the ordered cation structures suggest that interchange of K+ and Rb+ at the two cation sites changes the energy insignificantly. 相似文献