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951.
Warô Nakanishi Satoko Hayashi Takashi Furuta Norio Itoh Yusaku Nishina Makoto Yamashita 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5-6):1351-1355
Abstract Structures of 1,8-(ArZ)2C14H6O2 and 9-(MeO)-1,8-(ArZ)2C14H7 (Z = S, Se) are determined by X-ray crystallographic analysis. Five C─Z- - -O- - -Z─C atoms of the compounds align linearly, which are analyzed by the extended hypervalent 5c–6e model, based on QC calculations. CT of the 5c–6e occurs as the σ*(C─Z) ← n p (O)→ σ*(Z─C) direction. 相似文献
952.
The synthesis of a linear polymer having a tertiary amino group in a part of the main chain has been attempted by several methods. However, it was difficult for the linear polyamine to form because of the complicated reaction of the amino group. In the polymerization of weakly basic cyclic amines, e.g., 1-cyanoethylazetidine or 1-cyanoethylaziridine, high molecular weight polymers, poly-1-cyanoethyltrimethyleneimine (poly-CET) and poly-1-cyanoethyl-ethyleneimine (poly-CEE), were obtained. An attempt was made to convert poly-CET and poly-CEE into poly(l-benzylalkyleneimine)s (poly-BET and poly-BEE). Linear poly-BET was prepared by the alkylation of poly-CET (MW about 6000) with benzylbromide, followed by the elimination of the cyanoethyl group of polymer by heating. The poly-BET obtained was a white, greasy substance with a molecular weight of about 5000; its structure was determined by NMR spectroscopy. The cyanoethyl groups were replaced completely by benzyl groups. However, poly-BEE with a complete exchange to benzyl group was not obtained from poly-CEE due to the remaining cyanoethyl groups. Residual cyanoethyl groups replaced about 40% of the amino groups in poly-CEE. 相似文献
953.
The monomer and configurational sequences of several radical copolymers between substituted styrenes and acrylates have been examined by analyzing the high-resolution NMR spectra with the previously reported treatment of the styrene-methyl methacrylate system. The analyses have led to the conclusion that the monomer sequence distribution is just as expected from the usual copolymerization theory with r 1 and r 2. 相似文献
954.
Shinzo Yamashita 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1897-1922
Abstract Future trends in rubber processing are discussed with special emphasis on the chemical aspects that might be used to develop new and improved properties of rubber materials. They include optimization of such properties as resiliency and “softness,” of reinforcement and the control of crosslinking, and of the crosslink densities of rubbers during vulcanization. 相似文献
955.
ABSTRACT A-B Type block copolymer of N-vinylpyrrolidone (NVP) and 4-vinylpyridine (VPy) [poly(NVP-b-VPy) and graft copolymers of VPy onto copolymers of NVP with 4-vinylbenzyl N,N-diethyldithiocarbamate (VBDC) [poly(NVP-g-VPy) were synthesized by the iniferter method. the compatibility between NVP and VPy units in the copolymers was evaluated from the glass transition temperature of these copolymers. Hydroquinone was then oxidized by the synthesized NVP-VPy copolymers-Cu(II) complex catalysts. the influence of the distribution of each monomer unit in copolymers on the catalytic activity was studied by comparing the activity of these copolymers. the catalytic activity of these copolymers increased in the order: NVP-VPy blend polymer, poly(NVP-b-VPy), poly(NVP-g-VPy), random copolymer [poly(NVP-ran-VPy)]. This order parallels the compatibility between NVP units and VPy units in these copolymers. 相似文献
956.
Etsuo Yonemochi Shohei Sano Yasuo Yoshihashi Katsuhide Terada 《Journal of Thermal Analysis and Calorimetry》2013,113(3):1505-1510
Filmy solid dispersion of terfenadine (TFD), fenofibrate (FFB), and carbamazepine (CBZ) and methacrylic acid methyl methacrylate copolymer (Eudragit®) was prepared by evaporating their solution. Raman and IR measurements for the filmy samples were performed. Concentration profile of TFD, FFB, and CBZ in solid dispersions was evaluated by their characteristic peaks, and then their diffusion rate constants were calculated. The start point of the crystallization peak under isothermal condition was determined by XRD–DSC. Viscoelastic character of Eudragit® was evaluated by dynamic mechanical analysis (DMA). The distribution map of drugs in their solid dispersions showed the diffusion state of drugs during storage. The concentration profile of TFD, FFB, and CBZ in the solid dispersion was calculated from obtained mapping data. The diffusion rate constant of both drug in Eudragit® EPO was higher than that in Eudragit® RLPO. The induction period of crystallization from amorphous CBZ was gradually delayed with increasing amounts of Eudragit®. The IR peak due to C=O was shifted to higher wave number; it suggested that there were some molecular interactions between CBZ and Eudragit®. From the results of the change in the interaction of drug-Eudragit®, it may be concluded that the diffusivity of drug molecule in polymer closely related to the delay of the induction period of crystallization of amorphous. DMA measurement clarified the difference in the viscosity of Eudragit® having different functional groups and molecular mass. These results suggested that the retardation of crystallization by Eudragit® could be related to the sample viscosity. 相似文献
957.
958.
Peter B. Karadakov Shohei Saito 《Angewandte Chemie (International ed. in English)》2020,59(24):9228-9230
The simple anti‐aufbau DFT approach for estimating singlet excited state aromaticity suggested in a recent Communication published in this journal is shown to produce incorrect results because it targets a linear combination of the singlet and triplet configurations involving the HOMO and LUMO rather than the first singlet excited state. If the S1 state of a molecule is dominated by the HOMO→LUMO excitation, a comparably simple but theoretically consistent and qualitatively correct approximation to the S1 wavefunction can be achieved by performing a small “two electrons in two orbitals” CASSCF(2,2) calculation which can be followed by the evaluation of magnetic aromaticity criteria such as NICS. 相似文献
959.
Nobuto Yoshinari Natthaya Meundaeng Hiroyasu Tabe Yusuke Yamada Satoshi Yamashita Yasuhiro Nakazawa Takumi Konno 《Angewandte Chemie (International ed. in English)》2020,59(41):18048-18053
Postsynthetic installation of lanthanide cubanes into a metallosupramolecular framework via a single‐crystal‐to‐single‐crystal (SCSC) transformation is presented. Soaking single crystals of K6[Rh4Zn4O(l ‐cys)12] (K6[ 1 ]; l ‐H2cys=l ‐cysteine) in a water/ethanol solution containing Ln(OAc)3 (Ln3+=lanthanide ion) results in the exchange of K+ by Ln3+ with retention of the single crystallinity, producing Ln2[ 1 ] ( 2Ln ) and Ln0.33[Ln4(OH)4(OAc)3(H2O)7][ 1 ] ( 3Ln ) for early and late lanthanides, respectively. While the Ln3+ ions in 2Ln exist as disordered aqua species, those in 3Ln form ordered hydroxide‐bridged cubane clusters that connect [ 1 ]6? anions in a 3D metal‐organic framework through coordination bonds with carboxylate groups. This study shows the utility of an anionic metallosupramolecular framework with carboxylate groups for the creation of a series of metal cubanes that have great potential for various applications, such as magnetic materials and heterogeneous catalysts. 相似文献
960.
Yasutaka Kuwahara Genki Kato Akihiro Fujibayashi Kohsuke Mori Hiromi Yamashita 《化学:亚洲杂志》2020,15(13):2005-2014
Catalytic diesel soot combustion was examined using a series of Mn2O3 catalysts with different morphologies, including plate, prism, hollow spheres and powders. The plate‐shaped Mn2O3 (Mn2O3‐plate) exhibited superior carbon soot combustion activity compared to the prism‐shaped, hollow‐structured and powdery Mn2O3 under both tight and loose contact modes at soot combustion temperatures (T50) of 327 °C and 457 °C, respectively. Comprehensive characterization studies using scanning electron microscopy, scanning transmission electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, temperature‐programmed reduction and oxygen release measurements, revealed that the improved activity of Mn2O3‐plate was mainly attributed to the high oxygen release rate of surface‐adsorbed active oxygen species, which originated from oxygen vacancy sites introduced during the catalyst preparation, rather than specific surface‐exposed planes. The study provides new insights for the design and synthesis of efficient oxidation catalysts for carbon soot combustion as well as for other oxidation reactions of harmful hydrocarbon compounds. 相似文献