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101.
102.
Carbon Monoxide Oxidation by Polyoxometalate‐Supported Gold Nanoparticulate Catalysts: Activity,Stability, and Temperature‐ Dependent Activation Properties 下载免费PDF全文
Dr. Takuya Yoshida Prof. Dr. Toru Murayama Prof. Dr. Norihito Sakaguchi Prof. Dr. Mitsutaka Okumura Prof. Dr. Tamao Ishida Prof. Dr. Masatake Haruta 《Angewandte Chemie (International ed. in English)》2018,57(6):1523-1527
Nanoparticulate gold supported on a Keggin‐type polyoxometalate (POM), Cs4[α‐SiW12O40]?n H2O, was prepared by the sol immobilization method. The size of the gold nanoparticles (NPs) was approximately 2 nm, which was almost the same as the size of the gold colloid precursor. Deposition of gold NPs smaller than 2 nm onto POM (Au/POM) was essential for a high catalytic activity for CO oxidation. The temperature for 50 % CO conversion was ?67 °C. The catalyst showed extremely high stability for at least one month at 0 °C with full conversion. The catalytic activity and the reaction mechanism drastically changed at temperatures higher than 40 °C, showing a unique behavior called a U‐shaped curve. It was revealed by IR measurement that Auδ+ was a CO adsorption site and that adsorbed water promoted CO oxidation for the Au/POM catalyst. This is the first report on CO oxidation utilizing Au/POMs catalysts, and there is a potential for expansion to various gas‐phase reactions. 相似文献
103.
Fluorinated Vinylsilanes from the Copper‐Catalyzed Defluorosilylation of Fluoroalkene Feedstocks 下载免费PDF全文
Hironobu Sakaguchi Prof. Dr. Masato Ohashi Prof. Dr. Sensuke Ogoshi 《Angewandte Chemie (International ed. in English)》2018,57(1):328-332
Herein, a copper‐catalyzed C?F bond defluorosilylation reaction of tetrafluoroethylene and other polyfluoroalkenes is described. Mechanistic studies, based on a series of stoichiometric reactions with copper complexes, revealed that the key steps of this defluorosilylation reaction are 1) the 1,2‐addition of a silylcopper intermediate to the polyfluoroalkene and 2) a subsequent selective β‐fluorine elimination, which generates a Cu?F species. The β‐fluorine elimination is facilitated by Lewis acidic F?Bpin, which is generated in situ during the defluorosilylation. 相似文献
104.
A total synthesis of (-)-kainic acid starting from the commercially available 2-azetidinone is described. The key delta-lactone intermediate was concisely prepared from the commercially available azetidinone through the Reformatsky-type reaction and an introduction of a glycine moiety. The construction of the functionalized pyrrolidine ring was executed by a one-pot sequential elimination-Michael addition protocol of a beta-amino-delta-lactone intermediate with high diastereoselectivity. 相似文献
105.
Yamamoto M Yamada M Nonaka N Fukushima S Yasuda M Seki M 《Journal of the American Chemical Society》2008,130(43):14044-14045
This paper describes a facile technique to pattern reactive microdomains inside polydimethylsiloxane microchannels by utilizing polymer particles as the carrier of functional groups. The air/liquid interface formed in microchannels equipped with microwells exerts lateral force on the particles, trapping particles only inside the wells. We then fix the polymer matrix on the wells by melting the trapped particles to form reactive domains with flexible shapes and high resolution. We employed monodisperse poly(styrene-co-glycidyl methacrylate) microparticles having an epoxy group and patterned various types of microdomains with a resolution of several micrometers. Several tests confirmed the presence of the epoxy group and the flatness of the patterned domain. The presented scheme provides a new way of preparing highly functional microsystems by using simple operations and would be useful for various applications, including local patterning of graft polymers and the site-specific cultivation of cells in a confined space. 相似文献
106.
Aratono M Onimaru N Yoshikai Y Shigehisa M Koga I Wongwailikhit K Ohta A Takiue T Lhoussaine B Strey R Takata Y Villeneuve M Matsubara H 《The journal of physical chemistry. B》2007,111(1):107-115
The concentration vs composition diagram of aggregate formation of the dodecyltrimethylammonium bromide (DTAB) and didodecyldimethylammonium bromide (DDAB) mixture in aqueous solution at rather dilute region was constructed by analyzing the surface tension, turbidity, and electrical conductivity data and inspected by cryo-TEM images and dynamic light scattering data. Although the aqueous solution of DTAB forms only micelles, the transition from monomer to small aggregates and then to vesicle was found at 0.1 < X2 相似文献
107.
108.
We consider solutions of initial-boundary value problems for the heat equation on bounded domains in and their spatial critical points as in the previous paper [MS]. In Dirichlet, Neumann, and Robin homogeneous initial-boundary
value problems on bounded domains, it is proved that if the origin is a spatial critical point never moving for sufficiently
many compactly supported initial data being centrosymmetric with respect to the origin, then the domain must be centrosymmetric
with respect to the origin. Furthermore, we consider spatial zero points instead of spatial critical points, and prove some
similar symmetry theorems. Also, it is proved that these symmetry theorems hold for initial-boundary value problems for the
wave equation.
Received October 31, 1997; in final form February 3, 1998 相似文献
109.
A practical catalytic method to convert alkanes into the corresponding oxygen‐containing compounds with O2 under mild conditions using N‐hydroxyphthalimide (NHPI) in the presence or absence of a transition metal was developed. Thus, cyclohexane was successfully converted into adipic acid in good conversion and selectivity by a combined catalytic system consisting of NHPI and Mn(acac)2. Lower alkane such as isobutane was converted into t‐butyl alcohol (83%) under 10 atm of air by NHPI‐Co(OAc)2 system. Alkylbenzene such as toluene was oxidized to benzoic acid in high yield (81%) under normal temperature and pressure of dioxygen in the presence of a catalytic amount of NHPI and Co(OAc)2. ESR measurements showed that phthalimide‐N‐oxyl generated from NHPI under dioxygen atmosphere is a key species in this oxidation and functions as a radical catalyst. 相似文献
110.