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41.
42.
Takuma Shinya Nakashima Noriyuki Tantirungkij Manee Kinoshita Shinichi Okada Hirosuke Sew TatsÜji Yoshida Toshiomi 《Applied biochemistry and biotechnology》1991,28(1):327-340
Applied Biochemistry and Biotechnology - A NADPH/NADH-dependent xylose reductase gene was isolated from the xylose-assimilating yeast,Pichia stipitis. DNA sequence analysis showed that the gene... 相似文献
43.
Asymmetric membrane potentials and transport properties of polypeptide membrane consisting of two layers with poly(L-glutamic acid) and poly (γ-methylL-glutamate) were studied in the pH range of 2 to 6 at 25 °C. Under the condition adopted, the poly (L-glutamic acid) layer of the membrane underwentα helix to coil transition which was confirmed by ATR-IR measurements. The membrane potentials of the asymmetric membrane between two identical solutions of KCl,Δψ asym, which is called asymmetric potential, were observed.Δψ asym values were effected by the structural transition of poly (L-glutamic acid) layer. As a result, the effective charge density of the membrane, which was derived by the asymmetric membrane potential measurements, had a maximum at the transition region of pH=4.8. On the other hand, the permeation coefficient of KCl,P i, was higher in the direction from poly (L-glutamic acid) side to poly (γ-methylL-glutamate) side, “G →M direction”, than in the oppositeM →G direction. Furthermore,P i inG →M direction was dependent on the solution pH, that is,P i decreased when pH was increased to 4.8 and increased on further increasing of pH These membrane behaviors were described in terms of the competition between structural transition and variation of fixed charge density owing to the helix to coil transition of the asymmetric polypeptide membrane. 相似文献
44.
45.
Poly(phenylisopropenylketone (PPIK) and copolymers of PIK and methylmethacrylate (MMA) or styrene (St) were irradiated in benzene solution at 30° with 313 nm light (stationary irradiations) or with 347 nm light (flash photolysis experiments). Homo PPIK undergoes main chain degradation (β-scission) with ø(S) ≈ 0.05. The quantum yield for α-scission is ø(α) = 0.3. For copolymers of MMA and PIK (1 to 15 mol%), ø(S) is 0.04 independent of the copolymer composition. With copolymers of St and PIK, ø(S) was found to increase with decreasing PIK content and to approach 0.15 for very small PIK contents. The flash photolysis experiments showed: (a) the carbonyl triplet decay rate constant kT(6 × 106 sec?1) for CP-MMA-PIK samples is independent of copolymer composition but is lower than for homo PPIK (1 × 107 sec?1). In CP-St-PIK samples kT decreases with decreasing PIK content [from 8 × 106 sec?1 (12 mol% PIK) to 3 × 106 sec?1 (1 mol% PIK)]; (b) the transient spectra of triplet decay products indicate the formation of benzoyl radicals in the cases of PPIK and CP-MMA-PIK, and the formation of various different species in the case of CP-St-PIK.The results are consistent with the following concept. In homo PPIK and CP-MMA-PIK, α-scission (Norrish type I) is the dominant chemical route of triplet deactivation. In CP-St-PIK, however, type II processes become more and more important as the PIK content decreases. 相似文献
46.
Tadahiro Kato Motoyuki Tanaka Shin‐suke Takagi Keita Nakanishi Masahiro Hoshikawa 《Helvetica chimica acta》2004,87(1):197-214
The synthesis of kempa‐6,8‐dien‐3β‐ol ( 4a ), as a synthetic leading model of the natural product 4b , was carried out starting from intermediate 12 , the synthetic route of which has been developed previously (Scheme 1). The conversion of 12 to the model compound 4a involved the elaboration of three structure modifications by three processes, Tasks A, B, and C (see Scheme 2). Task A was achieved by epoxy‐ring opening of 41 with Me3SiCl (Scheme 9), and Task B being performed by oxidation at the 13‐position, followed by hydrogenation, and then epimerization (Schemes 4 and 5). The removal of the 2‐OH group from 12 (Task C) was achieved via 30b according to Scheme 6, whereby 30b was formed exclusively from 30a / 31a 1 : 1 (Scheme 7). In addition, some useful reactions from the synthetic viewpoint were developed during the course of the present experiments. 相似文献
47.
H Yamamoto T Arai K Masuda K Ikei H Hashimoto I Taguchi K Kinoshita 《Radioisotopes》1986,35(9):461-466
Multivariate statistical analyses using principal component analyses (PCA) and Mahalanobis' method were applied to the quality control of radioallergosorbent test (RAST). Mites and foods allergen were analyzed by PCA method, and foods allergen were analyzed by Mahalanobis' method. The vast differences in the distribution on titers among the mites and the foods were observed. To evaluate the results of a test and the quality of kits for test statistically, it should be better to use multivariate analyses such as PCA or Mahalanobis' method. 相似文献
48.
Unlike micelles of straight hydrocarbon chain-surfactants, isoprenoid surfactants, CH3 [CH(CH3)CH2CH2CH2]3 CH(CH3)CH2–R (R=CH2N+ (CH3)3 Br–, CH2OPO3H– Na+, CH2OSO
3
–
Na+, CO
2
–
Na+), gave large globular and cellular assemblies in water which could be observed directly by transmission electron microscopy; critical micelle concentration of 0.31.4×10–3 M at 20°C, aggregation number of 215×104, and diameter of 200–2000 Å. A basic structure of the assemblies was a thin layer with a thickness (about 30 Å) which was close to the molecular length of the surfactants. The assemblies were decomposed during gel column chromatography; viz., they were not as stable as the liposomes of lecithins. The morphology was discussed in conjunction with a steric effect of the isoprenoid chain. 相似文献
49.
Fabrication of mesoporous ZnO nanosheets from precursor templates grown in aqueous solutions 总被引:1,自引:0,他引:1
Keita Kakiuchi Eiji Hosono Toshio Kimura Hiroaki Imai Shinobu Fujihara 《Journal of Sol-Gel Science and Technology》2006,39(1):63-72
Mesoporous ZnO nanosheets were successfully prepared by pyrolytic transformation of zinc carbonate hydroxide hydrate, Zn4CO3(OH)6·H2O. The nanosheets were initially formed as assemblies on glass substrates during chemical bath deposition (CBD) in aqueous
solutions of urea and zinc acetate dihydrate, zinc chloride, zinc nitrate hexahydrate, or zinc sulfate heptahydrate at 80°C.
It was key to induce heterogeneous nucleation of Zn4CO3(OH)6·H2O by promoting a gradual hydrolysis reaction of urea and controlling the degree of supersaturation of zinc hydroxide species.
Morphology of Zn4CO3(OH)6·H2O was largely influenced by the anions present in the CBD solutions. The Zn4CO3(OH)6·H2O nanosheets were transformed into wurtzite ZnO by heating at 300°C in air without losing the microstructural feature. 相似文献
50.
Two new sesterterpenes, 6-epi-ophiobolin G (1) and 6-epi-ophiobolin N (3), and six known ophiobolins were isolated from the extracts of the fungus, Emericella variecolor GF10, which was separated from marine sediment. The planar structures of the new compounds were deduced from analysis of the 2D NMR spectra, and the stereochemistry was determined by extensive examination of the NOESY spectrum. Additionally, the configuration of the C-6 proton in ophiobolin G (2) was revised from α to β, and the unsolved stereochemistry of ophiobolin H (4) was determined by its physicochemical evidence and the chemical correlation with ophiobolin K (8). Ophiobolin K (8) showed cytotoxic activity against various tumor cell lines, including adriamycin-resistant mouse leukemia cells (P388), with IC50 of 0.27-0.65 μM. 相似文献