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991.
992.
Barbara Schüpp Liane Schrder Helga Schulte Carsten Bhtz Norbert Mattern Hans‐Lothar Keller 《无机化学与普通化学杂志》2002,628(7):1708-1714
Hochtemperatur‐Cs2[PdCl4] — New Results on a “wellknown” Compound Two modifications of Cs2[PdCl4] have been characterized by X‐ray powder and single crystal diffraction, respectively. The crystal structures are described and the group‐subgroup‐relations between these structures are discussed. In addition to the tetragonal (P4/mmm (No. 123), a = 7.4158(8) Å, c = 4.6792(6) Å) and the orthorhombic (Cmcm (No. 63), a = 10.529(1) Å, b = 10.310(1) Å, c = 9.460(1) Å) modification DSC investigations and high‐temperature X‐ray diffraction experiments with synchrotron radiation show the existence of another modification or of yet unknown decomposition products. The phase transformation from the orthorhombic to the tetragonal polymorph is completely finished at 100 °C. The second effect is detected at 319 °C. 相似文献
993.
Giacomo Biagiotti Ilaria Perini Barbara Richichi Stefano Cicchi 《Molecules (Basel, Switzerland)》2021,26(20)
The success of the rational bottom-up approach to nanostructured carbon materials and the discovery of the importance of their doping with heteroatoms puts under the spotlight all synthetic organic approaches to polycyclic aromatic hydrocarbons. The construction of atomically precise heteroatom doped nanographenes has evidenced the importance of controlling its geometry and the position of the doping heteroatoms, since these parameters influence their chemical–physical properties and their applications. The growing interest towards this research topic is testified by the large number of works published in this area, which have transformed a once “fundamental research” into applied research at the cutting edge of technology. This review analyzes the most recent synthetic approaches to this class of compounds. 相似文献
994.
995.
Barbara S. Larsen William J. Simonsick Charles N. McEwen 《Journal of the American Society for Mass Spectrometry》1996,7(3):287-292
Matrix-assisted laser desorption-ionization (MALDI) time of flight is shown to give a molar peak area response for isolated methylmethacrylate oligomers that have 25 and 50 repeat units when run on three different instruments in reflectron or linear mode and using three different matrix materials. In addition, fragmentation was not observed in any of the three different matrices or at higher laser power. No spectral differences were observed for syndiotactic and isotactic methylmethacrylate oligomers. These results suggest that the low most probable peak values observed for narrow distribution poly(methylmethacrylate) standards by MALDI mass spectrometry are not the result of mass discrimination or fragmentation. 相似文献
996.
Peter Seidel Barbara Sandner Udo Gopp Martin Schch Simone Steurich J. Paul Santerre 《Macromolecular Symposia》1999,144(1):165-177
Partially resorbable composite materials were developed for bone applications and were prepared by crosslinking copolymerization of oligo(lactone) macromonomers with selected comonomers in the presence of hydroxy apatite. The composites were incubated in aqueous solution of different pH and electrolyte content over a period up to 300 days. The percentage of the released hydroxycarboxylic acid from the oligo(lactone) branches was determined by the titration or by high performance liquid chromatography (HPLC). A catalytic influence of cholesterol esterase (CE) on the hydrolysis of the materials was observed. Determination of CE activity in the presence of the different composite materials showed that the half-life time of CE was the lowest in the presence of the material undergoing the fastest degradation. After degradation the composite materials have preserved their coherence and have shown higher glass transition temperatures in the dried state than the materials before degradation. 相似文献
997.
Simone Fausti Giovanni La Penna Angelo Perico Roberto Pratolongo 《Macromolecular Symposia》1999,146(1):97-101
A mode-coupling approach has been used to solve the Smoluchowski diffusion equation describing the correlation functions relevant in nuclear magnetic relaxation experiments on biological molecules like protein and DNA. A good reproduction of relaxation patterns for molecules that are fluctuating about three-dimensional structures imposed by secondary motives has been found. Important differences can be explained with the poor statistics collected by numerical simulations that do not contain fluctuations contributing to rates in the ns time-scale, therefore comparable with rotational rates. 相似文献
998.
999.
Celastrus hindsii is a popular medicinal plant in Vietnam and Southeast Asian countries as well as in South America. In this study, an amount of 12.05 g of an α-amyrin and β-amyrin mixture was isolated from C. hindsii (10.75 g/kg dry weight) by column chromatography applying different solvent systems to obtain maximum efficiency. α-Amyrin and β-amyrin were then confirmed by gas chromatography-mass spectrometry (GC-MS), electrospray ionization-mass spectrometry (ESI-MS), and nuclear magnetic resonance (NMR). The antioxidant activities of the α-amyrin and β-amyrin mixture were determined via 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,20-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays with IC50 of 125.55 and 155.28 µg/mL, respectively. The mixture exhibited a high potential for preventing gout by inhibiting a relevant key enzyme, xanthine oxidase (XO) (IC50 = 258.22 µg/mL). Additionally, an important enzyme in skin hyperpigmentation, tyrosinase, was suppressed by the α-amyrin and β-amyrin mixture (IC50 = 178.85 µg/mL). This study showed that C. hindsii is an abundant source for the isolation of α-amyrin and β-amyrin. Furthermore, this was the first study indicating that α-amyrin and β-amyrin mixture are promising in future therapies for gout and skin hyperpigmentation. 相似文献
1000.
The reactions of iodate and periodate with Fe(phen)32+ have been studied in neutral medium iodate ion is unreactive with ferroin in aqueous solution. The reaction is autocatalytic in the case of IO4−. The autocatalysis disappears in an excess of IO3−. The rate constants of both processes were determined and a reaction mechanism has been proposed. © 1996 John Wiley & Sons, Inc. 相似文献