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781.
[reaction: see text] Samarium iodide mediated reductive cross-coupling of N-tosyl benzylideneamine with benzaldehydes or the corresponding chromium complexes gave syn-beta-amino alcohol derivatives. A dynamic kinetic resolution of a configurationally equilibrated reactive species occurred in the cross-coupling with planar chiral benzaldehyde chromium complexes. 相似文献
782.
Takano Y Taniguchi T Isobe H Kubo T Morita Y Yamamoto K Nakasuji K Takui T Yamaguchi K 《Journal of the American Chemical Society》2002,124(37):11122-11130
The phenalenyl radical (1) is a prototype of the hydrocarbon radical. Recently, the single crystal of 2,5,8-tri-tert-butylphenalenyl (2) was isolated and showed that the two phenalenyl radicals form a staggered dimeric pair, giving rise to strong antiferromagnetic interactions. The origin of the antiferromagnetic interactions and the nature of the chemical bond for the dimeric pair are challenging issues for chemists. First, spin-polarized hybrid DFT (Becke's half and half LYP (UB2LYP)) and CASSCF calculations were performed for 2 and its simplified model, the staggered-stacking phenalenyl radical dimeric pair (3a), to elucidate the origin of the strong antiferromagnetic coupling and the characteristics of the chemical bond. The calculated results showed that a SOMO-SOMO overlap effect was responsible for the strong antiferromagnetic interactions and weak or intermediate covalent bonding between phenalenyl radicals. The tert-butyl groups introduced at three beta-positions hardly affected the magnetic coupling, mainly causing steric hindrances in the crystalline state. Next, to obtain insight into ferromagnetic stacking, we investigated the stacking effect of staggered (3a)- and eclipsed (3b)-stacking phenalenyl radical dimeric pairs with a change of the SOMO-SOMO overlap on the basis of the extended McConnell model. We found that the stacking mode of the dimeric pair with both a small SOMO-SOMO overlap and a ferromagnetic spin polarization effect provided a ferromagnetic coupling. 相似文献
783.
Tsugio Kitamura Tatsuya Takachi Hironobu Kawasato Shinjiro Kobayashi Hiroshi Taniguchi 《Tetrahedron letters》1989,30(52):7445-7446
Treatment of
-(phenyloxy)phenylalkyne
with HClO4 or HBF4 gave dibenz(b, f)oxepin
, whereas the sulfur analogue,
-(phenylthio)phenylalkyne
, provided 1-phenyl-1-benzothiophenium salts
. 相似文献
784.
Y. Kitazawa Y. Kunimoto M. Wakihara M. Taniguchi 《Journal of Thermal Analysis and Calorimetry》1982,25(2):279-290
The phase diagram of the La-S-O system at 1073 K was established with the vacuum seal technique. Six phases exist at this temperature: La2O3 (B-type), LaS2, La2S3, La2O2SO4, La2O2S and La2O2S2. The thermodynamic functions for the reaction La2O2SO4=La2O3+SO2+1/2 O2 were determined by using the emf method at temperatures from 1123 to 1373 K. The mechanisms of the oxidation reactions in the La-S-O system under different partial pressures of oxygen (–4.4 < log
<–0.7) were also investigated by means of DTA, TG and powder X-ray diffractometry.
Zusammenfassung Das Phasendiagramm des La-S-O-Systems bei 1073 K wurde bestimmt. Bei dieser Temperatur liegen 6 Phasen vor, und zwar La2O3 (B-Typ), LaS2, La2S3, La2O2SO4, La2O2S und La2O2S2. Für die Reaktion La2O2SO4=La2O3+SO2+1/2 O2 wurden die thermodynamischen Funktionen im Temperaturbereich von 1123–1373 K nach der EMF-Methode bestimmt. DTA, TG und Pulver-Röntgendiffraktometrie wurden zur Untersuchung der Mechanismen der im La-S-O-System verlaufenden Oxydationsreaktionen herangezogen, wobei der Sauerstoffpartialdruck in den Grenzen von – 4.4 < log < <-0.7 variiert wurde.
La-S-O 1073 . : La2O3 (-), LaS2, La2S3, La2O2SO4, La2O2S La2O2S2. . . ., La2O2SO4=La2O3+ SO2+1/2 2 1123–1373. , La-S-O –4.4 < log < –0.7.相似文献
785.
Axially chiral N-methylanilides were synthesized by enantioselective lithiation of prochiral tricarbonyl(N-methyl-N-pivaloyl-2,6-dimethylaniline)chromium (1) with the lithium amide of the 4-methylpiperazinylethylamine derivative 13 followed by electrophilic quenching up to 97% ee in good yields. The resulting axially chiral chromium-complexd anilides 2 were oxidized under air to give the axially chiral anilides 14 in enantiomerically active form without axial bond rotation at room temperature. 相似文献
786.
Tadashi Saito Taichi Miura Atsushi Shinohara Junichiro Shintai Eugene Taniguchi Michiaki Furukawa Kazuhiro Takesako Nobutsugu Imanishi Hisakazu Muramatsu Yoshio Yoshimura Hiroshi Baba Hidekazu Doe 《Hyperfine Interactions》1994,84(1):193-198
Atomic capture probabilities of negative pions in some metal hydrides were measured. The capture by a hydrogen atom was detected by means of a pair of the annihilation rays of 0 which had been produced by the charge-exchange reaction of – with the capturing hydrogen nucleus (proton). This method ensures a high sensitivity and reliability of the measurements. The probabilities obtained were in agreement with previous measurements except for palladium hydride, which showed a much smaller probability than that given in the literature. The atomic capture of – is well described in the framework of the large mesic molecular model, in which the proportionality constant reflects the chemical states of the capturing atoms and also the neighboring ones. 相似文献
787.
Atsushi Shinohara Toshiharu Muroyama Junichirou Shintai Eugene Taniguchi Tadashi Saito Taichi Miura Nobutsugu Imanishi Yoshio Yoshimura Michiaki Furukawa 《Hyperfine Interactions》1994,84(1):569-574
The transfer of negative pions captured by hydrogen to heavier atoms has been investigated in a series of alcohols by measuring both 2 rays from 0 decay and pionic X rays. Capture rates for the pionic hydrogen of different chemical states in the molecule were determined from a comparison between the data for the ordinary compound and the deuterated one. The external transfer in the condensed phase was revealed by the dependence of the capture rate of hydrogen on the number of carbon atoms in the alkyl group. The influence of the chemical structure on the transfer process is discussed with respect to the large difference between the relative transfer rates,
C=1.5±0.2 and
O = 4.5±0.4, corresponding to carbon and oxygen, respectively. 相似文献
788.
789.
790.
The availability of stable chlorins bearing few or no substituents has enabled a variety of fundamental studies. The studies described herein report absorption spectra of diverse chlorins, comparative NMR features of chlorins bearing 0-3 meso-aryl substituents, and X-ray structures of the fully unsubstituted chlorin and the oxochlorin. 相似文献