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排序方式: 共有98条查询结果,搜索用时 15 毫秒
71.
Kazuhide Tani Kenichi Suwa Eiji Tanigawa Tomokazu Ise Tsuneaki Yamagata Yoshitaka Tatsuno Sei Otsuka 《Journal of organometallic chemistry》1989,370(1-3):203-221
Two types of the optically active peralkyldiphosphine, 2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(dialkylphosphino)butane (Rdiop 3) and N-(N′-substituted carbamoyl-4-dicyclohexylphosphino-2-dicyclohexylphosphinomethylpyrrolidine (R-Cycapp 8), have been prepared by various synthetic methods. Rhodium(I) complexes of 3 and 8 showed high catalytic activity for hydrogenation of various kinds of prochiral ketones, which were reduced smoothly to the corresponding optically active hydroxy compounds, under hydrogen at atmospheric pressure and ambient temperature. The neutral rhodium(I) complexes (diphosphine-RhN) hydrogenated -ketoamides and -ketopantolactone in fairly high optical yields (66–77%ee). In the hydrogenation of N-(-ketoacyl)--amino esters, the Cydiop-RhN catalyst showed a marked contrast to the diop-RhN system; in the hydrogenation of the methyl ester of N-(phenylglyoxyl)-(S)--phenylalanine, 72%de was attained with little double asymmetric induction by the chiral center in the substrate. 相似文献
72.
Tetsuro Shimo Tsuneaki Iwakiri Kenichi Somekawa Takaaki Suishu 《Journal of heterocyclic chemistry》1992,29(1):199-201
Photosensitized cycloaddition reaction of methyl 2-pyrone-5-carboxylate ( 1 ) with 2,3-dihydrofuran gave cis- exo- and cis-endo-[2 + 2] cycloadducts across the C3-C4 double bond in 1 , and a [4 + 2] cycloadduct which was different in addition-orientation from the Diels-Alder adducts. Each [2 + 2] cycloadduct was obtained by the use of sensitizers having different triplet energies. Photosensitized reactions of 1 with 3,4-dihydro-2H-pyrans afforded cis-endo-[2 + 2] cycloadducts, respectively. The photocycloaddition mechanism was also explained from the excited state of 1 calculated by means of MNDO-Cl method. 相似文献
73.
A splitless injection method using make-up flow was developed for SFC. Dilution of sample solvent with carbon dioxide mobile phase was very effective for focusing the solutes onto the column. Injection of a 4.5-μl sample volume on a 100-μm i.d. capillary column became possible. 相似文献
74.
A solid-phase extraction (SPE) method using triacontyl bonded silica (C30) as sorbent was developed for the determination of 16 US Environmental Protection Agency polycyclic aromatic hydrocarbons (PAHs) in airborne particulate matters quantitatively by gas chromatography-mass spectrometry (GC-MS). Optimization experiments were conducted using spiked standard aqueous solution of PAHs and real airborne particulates samples aiming to obtain highest SPE recoveries and extraction efficiency. Factors were studied in SPE procedures including the concentration of organic modifier, flow rate of sample loading and elution solvents. The ultrasonication time and solvents were also investigated. Recoveries were in the range of 68-107% for standard PAHs aqueous solution and 61-116% for real spiked sample. Limits of detection (LODs) and limits of quantification (LOQs) with standard solution were in the range of 0.0070-0.21 microgL(-1) and 0.022-0.67 microgL(-1), respectively. The optimized method was successfully applied to the determination of 16 PAHs in real airborne particulate matters. 相似文献
75.
Carboxylate‐Driven Supramolecular Assemblies of Protonated meso‐Aryl‐Substituted Dipyrrolylpyrazoles
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Prof. Hiromitsu Maeda Kengo Chigusa Dr. Ryohei Yamakado Dr. Tsuneaki Sakurai Prof. Shu Seki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(26):9520-9527
Dipyrrolylpyrazole (dpp) derivatives possessing an aryl ring at the pyrazole 4‐position were synthesized. Upon protonation, modified dpp derivatives formed a variety of assembled structures through complexation with carboxylates, as observed by single‐crystal X‐ray and synchrotron XRD analyses. In particular, the complexation of protonated dpp species possessing long alkyl chains with dicarboxylates resulted in highly ordered assembled structures, the packing modes of which as lamellar structures were controlled by the lengths of the spacer units between two carboxylate moieties. The charge‐carrier transporting properties of the solid materials were also controlled by bound anions, including dicarboxylates. 相似文献
76.
Partitioning sample collection/solvent extraction cartridge packed with octadecyl‐derivatized macroporous silica particles for the analysis of sesquiterpenes in air samples
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Ikuo Ueta Moe Onikata Suguru Mochizuki Koji Fujimura Tomohiro Sasaki Junji Aoki Tsuneaki Maeda 《Journal of separation science》2015,38(22):3891-3896
A novel sampling device based on the partition of target analytes to the extraction medium was developed for the determination of sesquiterpenes in air samples. The extraction medium was prepared by the chemical derivatization of a specially prepared macroporous silica, with a specific surface area of 2.0 m2/g. Taking advantage of the sample extraction, which was mainly based on the partition of sesquiterpenes between air and a C18‐bonded phase, the extracted analytes were rapidly and quantitatively desorbed just by passing a small amount of desorption solvent for subsequent analysis by gas chromatography with mass spectrometry. Several experimental conditions, such as the sampling volume and temperature, were systematically evaluated. Under optimized conditions, desorption of the extracted analytes was completed within 1 min with a desorption efficiency of more than 99.9%, achieved using 5 mL of acetone for all the evaluated sesquiterpenes. The applicability of the developed device was confirmed by the determination of several sesquiterpenes from coniferous trees. Although further improvements of the device are required for collecting large volumes or high‐temperature air samples, the potential of the developed sampling device was confirmed by determining traces of semivolatile organic compounds in air samples. 相似文献
77.
A review is presented on the recent advances in theoretical and experimental studies of itinerant electron metamagnetism (IEM) found in 3d and 5f intermetallic compounds without magnetic rare-earth elements. These compounds exhibit various peculiar magnetic properties characteristic of IEM under high magnetic fields and high pressures. The observed IEM and peculiar properties are found to be qualitatively explained very well by theories of IEM based on the spin fluctuation model. 相似文献
78.
Toshiyuki Miyata Takumi Mizuno Yoshio Nagahama Ikuzo Nishiguchi Tsuneaki Hirashima Noboru Sonoda 《Heteroatom Chemistry》1991,2(4):473-475
2,4-Dioxo-1,2,3,4-tetrahydroquinazolines were easily synthesized in excellent yields by sulfur-assisted carbonylation of 2′-aminobenzamides with carbon monoxide in the presence of a base, such as DBU or DBN. 相似文献
79.
α‐exomethylene lactone possessing acetal–ester linkage: Polymerization and postpolymerization modification for water‐soluble polymer
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Yasuhiro Kohsaka Yusuke Matsumoto Tianyi Zhang Yosuke Matsuhashi Tatsuki Kitayama 《Journal of polymer science. Part A, Polymer chemistry》2016,54(7):955-961
2,6‐Dimethyl‐5‐methylene‐1,3‐dioxa‐4‐one (DMDO), a cyclic acrylate possessing acetal–ester linkage, was obtained as a mixture of cis‐ and trans‐isomers (95:5) from Baylis–Hillman reaction of an aryl acrylate. The radical and anionic polymerizations of DMDO yielded the corresponding vinyl polymers without any side reactions such as cleavage of the acetal–ester linkage. The polymerization behaviors were significantly different from that of the acyclic acrylate, α‐(hydroxymethyl)acrylic acid, which was expected inactive against polymerization due to the steric hindrance around the vinylidene group by the α‐substituent. The acetal–ester linkage of the obtained polymer ( P1 ) was completely cleaved via acid hydrolysis to afford a water soluble polymer, P2 . © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 955–961 相似文献
80.