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941.
Suzuki S Morita Y Fukui K Sato K Shiomi D Takui T Nakasuji K 《Journal of the American Chemical Society》2006,128(8):2530-2531
We have demonstrated the first MS and NMR observation of a face-to-face pi-bonded dimer of an organic radical (pancake-bonded dimer coined by R. S. Mulliken) in solution, using tri-tert-butylated phenalenyl radical 1, a 3-fold symmetric neutral hydrocarbon. In addition to the direct detection of the dimer signal by cold-spray ionization mass spectrometry (CSI-MS), 1H and 13C NMR spectra in solution gave definitive evidence of a well-defined D3d dimer structure with a 12-center-2-electron-long C-C bond formation, which is the same symmetry as seen in the crystalline state. On the basis of the NMR peaks of the dimer in the aromatic region (6.47 ppm for 1H NMR and 120-143 ppm for 13C NMR), we carried out nucleus-independent chemical shift (NICS) analysis, which showed that the ring center of the dimer became more aromatic (-7.1 ppm) than that of the monomer (-3.8 ppm). The trend of aromaticity generation was more pronounced in the interior of the dimer, which has been interpreted by the negative electron density induced in the bonding region as seen in the electrostatic potential surface. 相似文献
942.
Bai YL Tao J Wernsdorfer W Sato O Huang RB Zheng LS 《Journal of the American Chemical Society》2006,128(51):16428-16429
A novel single-chain magnet, [MnIII3O(Meppz)3(EtOH)4(OAc)] (1), has been successfully synthesized from a secondary building block [MnIII3O(Meppz)3(EtOH)5Cl] (2) with an S = 1 ground state. SCM 1 exhibits both magnetization relaxation and dielectric relaxation properties. 相似文献
943.
Gao YF Nagai M Masuda Y Sato F Seo WS Koumoto K 《Langmuir : the ACS journal of surfaces and colloids》2006,22(8):3521-3527
A hydrotalcite-like film has been successfully deposited on an Al-bearing glass substrate based on an interface reaction between an Al layer and a zinc aqueous solution. The film selectively grew on the Al surface but not on the glass surface. The film on Al was composed of layered nanosheets of a hydrotalcite-like compound containing Al and Zn. Comparably, deposits on the plastic surface and precipitates in solution were wurzite-type ZnO with various morphologies depending upon the preparation conditions. At low supersaturation degrees, single crystals and superstructures of Zn-Al hydrotalcite were also obtained. This porous hydrotalcite film has a potential application as catalyst supports, environmental materials, or matrixes for hydrotalcite-based nanocomposite films. Using Al as a reaction interface makes it easy to coat porous hydrotalcites on a series of matrix materials varying in shapes and properties, which is important for achieving practical applications. In addition, the method developed should be widely applicable to other systems for the preparation of porous or oriented hydrotalcite-like thin films by an appropriate combination of divalent/trivalent solution-substrate systems. 相似文献
944.
Yasuhiro Matsuda Takefumi Kawata Shinji Sugihara Sadahito Aoshima Takahiro Sato 《Journal of Polymer Science.Polymer Physics》2006,44(8):1179-1187
The aqueous solution of a thermoresponsive polymer, poly[2‐(2‐ethoxy) ethoxyethyl vinyl ether] poly(EOEOVE), contains a tiny amount of large polymer aggregates at low polymer concentrations far below the lower critical solution temperature (~40 °C). The molar mass Mw,slow, radius of gyration 〈S2〉, and hydrodynamic radius RH,slow of the aggregating component of poly(EOEOVE) were obtained by simultaneous static and dynamic light scattering as functions of the polymer concentration and temperature, while the weight fraction wslow of the component was estimated by size‐exclusion chromatography. The Mw,slow dependencies of 〈S2〉 and RH,slow, as well as the ratio 〈S2〉/RH,slow, indicated that the poly(EOEOVE) aggregate takes a sparsely branched polymer‐like conformation. We have analyzed the structure of the aggregate, using the branched polymer model of random type. The Mw,slow dependence of 〈S2〉 obtained was favorably compared with this model with reasonable structural parameters. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1179–1187, 2006 相似文献
945.
Terao K Kikuchi N Sato T Teramoto A Fujiki M Dobashi T 《Langmuir : the ACS journal of surfaces and colloids》2006,22(19):7975-7980
Poly[n-hexyl-(S)-3-methylpentylsilane] aggregates confined in microcapsules to keep the aggregation number and ranging in average polymer mass m(p) in a microcapsule from 2 x 10(-)(16) to 2 x 10(-)(14) g were studied by circular dichroism measurements in ethanol (a nonsolvent) and tetrahydrofuran (an associative solvent at low temperature) at various temperatures. The weight-average molecular weight M(w) and the polydispersity index (the ratio of M(w) to the number-average molecular weight) of the polysilane sample were 6.6 x 10(4) and 1.07, respectively, and the average number of polymer molecules in each capsule was estimated to be 1.9 x 10(3) for m(p) = 2 x 10(-)(16) g and 1.7 x 10(5) for m(p) = 2 x 10(-)(14) g. The size of each aggregate did not affect the optical activity because the circular dichroism thus obtained was proportional to m(p) under the same conditions in the investigated m(p) range; on the other hand, the peak height of the circular dichroism in tetrahydrofuran had a significant hysteresis between 0 and 25 degrees C. Moreover, the circular dichroism appreciably reflected the prepared method, that is, the temperature and solvent; in other words, the aggregates memorized the initial conditions in their stacking structures. 相似文献
946.
Interaction forces between alumina surfaces were measured using an AFM-colloid probe method at different pHs. For an alpha-alumina-sapphire system at acidic pH, the force curve exhibited a well-defined repulsive barrier and an attractive minimum. At basic pH, the interactive force was repulsive at all separations with no primary minimum. Lateral force measurements under the same conditions showed that frictional forces were nearly an order of magnitude smaller at basic pH than those observed at acidic pH. This behavior was attributed to the hydration of the alumina surface. Normal and lateral force measurements with the strongly hydrated rho-alumina surfaces supported these findings. 相似文献
947.
Fujimori I Mita T Maki K Shiro M Sato A Furusho S Kanai M Shibasaki M 《Journal of the American Chemical Society》2006,128(51):16438-16439
New chiral ligands for asymmetric polymetallic catalysts were designed on the basis of the assumption that the higher-order assembly structure is stabilized by modifying the modular unit. The designed ligands 6 and 7 contained a scaffolding cyclohexane ring with a Lewis base phosphine oxide directly attached to the scaffold. A module in the polymetallic complex contains two metals per ligand, and a stable 6-, 5-, 5-membered fused chelation ring system should be generated. Synthesis of these ligands is simple and high yielding, using a catalytic dynamic kinetic resolution promoted by the Trost catalyst as a key step. Ligand function was assessed in a catalytic asymmetric ring-opening reaction of meso-aziridines with TMSCN, a useful reaction for the synthesis of optically active beta-amino acids. The Gd complex generated from Gd(OiPr)3 and the ligand was a highly active and enantioselective catalyst in this reaction. Enantioselectivity was reversed compared to the previously reported d-glucose-derived catalyst containing the same chirality of the individual module. ESI-MS analysis and X-ray crystallographic studies indicate that the assembly state of the modules in the polymetallic catalysts differs depending on the chiral ligand. The difference in the higher-order structure stems from a subtle change (one carbon) in the position of the Lewis base relative to the Gd metal. The change in the higher-order structure of the polymetallic complex led to a dramatic reversal of the enantioselectivity and increased catalyst activity. 相似文献
948.
Kawai T Shibata A Kurosawa K Sato Y Kato S Ohki K Hashimoto T Sakura N 《Chemical & pharmaceutical bulletin》2006,54(5):659-664
Porcine neuromedin U-8 (X-Asn-NH(2), X=H-Tyr-Phe-Leu-Phe-Arg-Pro-Arg) is occasionally unstable in the biological fluids used for bioassay as well as in the acidic solutions used for purification of synthetic peptides. In this study, HPLC examination of an incubate solution of X-Asn-NH(2) revealed that the main decomposition products in Tyrode's solution (pH 7.4) were either alpha- or beta-monocarboxylic acid analogs (X-Asn-OH or X-Asp-NH(2)), and that no dicarboxylic acid analog (X-Asp-OH) was produced. Further investigation, employing a model peptide (Y-Asn-NH(2), Y=Benzoyl-Pro-Arg) incubated in a 0.1 M sodium bicarbonate solution at 60 degrees C, revealed that the decomposition of C-terminal Asn-NH(2) occurred through the formation of an aminosuccinimide intermediate (Y-Asu), at a rate faster than that of Y-Asn-Ser peptide but slower than that of Y-Asn-Gly peptide. Mild acid hydrolysis of X-Asn-NH(2) examined in a 1 M HCl solution at 60 degrees C yielded X-Asn-OH and X-Asp-NH(2), which further decomposed to yield X-Asp-OH. The C-terminal degradation of X-Asn-NH(2) resulted in reduced biological and immunochemical binding activities. 相似文献
949.
Hai Yen Thi Phan Takashi Yano Hai Anh Thi Phan Tsuyoshi Nishimura Tetsumi Sato Yoritaka Hashimoto 《Applied Acoustics》2010,71(2):107-114
Vietnam is a developing country in southeast Asia, and its environment has been seriously affected by industrialization and urbanization. In large cities like Hanoi (northern Vietnam) and Ho Chi Minh City (southern Vietnam), noise emission from road traffic has been found to be a serious concern among general public. In 2005 and 2007, two large-scale socio-acoustic surveys of community response to road traffic noise were conducted to investigate human reactions to road traffic noise in these cities; the sample sizes were 1503 people in Hanoi and 1471 in Ho Chi Minh City. The noise exposure levels (Lden) were 70–83 dB in Hanoi and 75–83 dB in Ho Chi Minh City. Noise annoyance was estimated using standardized annoyance scales. For both cities, dose–response relationships were established between Lden and the percentage of highly annoyed respondents. Compared to annoyance responses of European people, Vietnamese were less annoyed by road traffic noise by about 5 dB. Hanoi respondents seemed to be more annoyed by noise than Ho Chi Minh City respondents. Conversation and sleep disturbances were not as serious as expected in either city. Furthermore, window orientation in the home was found to affect activity disturbances. 相似文献
950.