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61.
62.
63.
Ryosuke Matsui Erina Niijima Tomomi Imai Hiroyuki Kobayashi Akiko Hori Azusa Sato Yuko Nakamura Osamu Kitagawa 《Molecules (Basel, Switzerland)》2022,27(7)
The halogen bond has been widely used as an important supramolecular tool in various research areas. However, there are relatively few studies on halogen bonding related to molecular chirality. 3-(2-Halophenyl)quinazoline-4-thione derivatives have stable atropisomeric structures due to the rotational restriction around an N-C single bond. In X-ray single crystal structures of the racemic and optically pure N-C axially chiral quinazoline-4-thiones, we found that different types of intermolecular halogen bonds (C=S⋯X) are formed. That is, in the racemic crystals, the intermolecular halogen bond between the ortho-halogen atom and sulfur atom was found to be oriented in a periplanar conformation toward the thiocarbonyl plane, leading to a syndiotactic zig-zag array. On the other hand, the halogen bond in the enantiomerically pure crystals was oriented orthogonally toward the thiocarbonyl plane, resulting in the formation of a homochiral dimer. These results indicate that the corresponding racemic and optically pure forms in chiral molecules are expected to display different halogen bonding properties, respectively, and should be separately studied as different chemical entities. 相似文献
64.
Mikio Hori Tadashi Kataoka Hiroshi Shimizu Kiminori Tomimatsu 《Tetrahedron letters》1982,23(8):901-904
The isolates cis- and trans-9phenylselenoxanthene-N-arylsulfonylselenilimines were not interconverted thermally. cis-Isomers were converted to trans-isomers by chloramine-T or -B in a fashion of SN2 type substitution. cis-Isomers did not rearrange but trans-isomers rearranged thermally to 9-arylsulfonamido-9-phenylselenoxanthenes, whereas both isomers underwent the base-catalyzed intermolecular rearrangement. 相似文献
65.
Perfluorocarboxylic acids and their anions (PFCAs), such as perfluorooctanate (C7F15C(O)O?), have been generally recognized to be global pollutants and are believed to persist in the environment. Kinetic data for reactions of sulfate anion radicals (SO4?) with PFCAs are needed to evaluate the residence times of PFCAs in the environment, but no kinetic data have been reported, except for the rate constant for the reaction of SO4? with trifluoroacetate (CF3C(O)O?) (k1). In this study, using the fact that PFCAs react with SO4? to form shorter chain PFCAs, we determined rates relative to k1 of the reactions of photolytically generated SO4? with two short‐chain PFCAs, pentafluoropropionate (C2F5C(O)O?; k2) and heptafluorobutyrate (C3F7C(O)O?; k3), along with conversion ratios for conversion of C2F5C(O)O? into CF3C(O)O? (α) and conversion of C3F7C(O)O? into C2F5C(O)O? (β) and CF3C(O)O? (γ) at 298 K. Values of k1, k2, or k3 might change over the course of reaction with increasing ionic strength. Nevertheless, if the values of k1/k2, k2/k3, α, β, and γ remain almost constant during the reaction, a simple equation involving relative rates, such as k1/k2, can be used to relate the concentrations of C3F7C(O)O?, C2F5C(O)O?, and CF3C(O)O?. We compared the relative rates, such as k1/k2, and the conversion ratios determined from various experimental runs with different initial conditions to check whether relative rates and conversion ratios remained almost constant during each experimental run. The values of k1/k2, k2/k3, α, β, and γ seemed to remain almost constant, which facilitated determination of k2/k1 = 0.89 ± 0.07, k3/k1 = 0.84 ± 0.08, α = 0.88 ± 0.05, β = 0.75 ± 0.05, and γ = 0.17 ± 0.02. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 276–288, 2007 相似文献
66.
Masato Sakaguchi Hiromu Kinpara Yasuro Hori Shigetaka Shimada Hisatsugu Kashiwabara 《Journal of Polymer Science.Polymer Physics》1988,26(6):1307-1312
When poly(vinylidene fluoride) (PVDF) was ground with tetracyanoethylene (TCNE) powder in a vibration glass ball mill in vacuum in the dark at 77 K, the TCNE anion radical (TCNE-) was detected in the mixture by ESR spectroscopy. The TCNE.- is formed by the abstraction of electrons by TCNE from the anion that is produced by a heterogeneous bond scission of carbon-carbon bonds in the polymer main chain. The assignment of TCNE.- was carried out by the ESR spectral simulation on the basis of an anisotropic effective hyperfine tensor that includes a forbidden transition term. At least 85% of the bond scission of the PVDF main chain is induced by a heterogeneous process to produce ionic products. The yield of these mechanions seems to increase with the polarity of carbon-carbon bond owing to a substituent group bonded to the carbon in the polymer main chain. 相似文献
67.
Vanadium content of the eggs and embryos of ascidian, Halocynthia roretzi was determined by activation analysis. The determination
was performed by the comparison of the activity around 1.434 MeV peak of52V in the sample to that of the standard. The concentration of vanadium in the eggs remained unchanged during the cleavage
stage and the animal accumulated it progressively in the early embryogenesis. The content in the larvae after metamorphosis
amounted to nearly fifteen times of that of the unfertilized eggs. 相似文献
68.
69.
Yukio Inoue Hirokazu Hori Takeki Sakurai Yukiko Tokitomo Junko Saito Taku Misonou 《Optical Review》2002,9(2):75-80
Optical properties of an ultraviolet-absorbing substance (UVAS) extracted from the marine red alga, Porphyra yezoensis, have been investigated. The substance is excited by UV light, and the emitted fluorescence is detected using an intelligent fluorescence detector. The fluorescence of UVAS is weaker by four orders of magnitude than the fluorescence intensity emitted by anthracene in the same optical system. The absorbed energy is apparently not transferred to the photosynthesis process and is believed to be consumed as heat. Using photothermal spectroscopy, a signal is observed indicating that the absorbed photon energy has transferred to the heat. The waveform of the photothermal signal of UVAS is similar to that of quinoxaline, whose fluorescence quantum yield is known to be zero. It is determined that the fluorescence quantum yield and the energy of the triplet state of UVAS are 1.7 ± 0.7 ± 10−4 and 21000 ± 1000 cm −1, respectively. The conclusion is that the excited molecules of UVAS decay by passing through the triplet state and dissipate all absorbed energy as heat. 相似文献
70.
Non-stereospecific ring expansions of 3-acetylbenzothiazoline sulfoxides to benzothiazines from the reaction with acetic anhydride are reported. 相似文献