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51.
The Hexagallane [Ga6{SiMe(SiMe3)2}6] and the closo‐Hexagallanate [Ga6{Si(CMe3)3}4 (CH2C6H5)2]2— — the Transition to an Unusual precloso‐Cluster The closo hexagallanate [Ga6R4(CH2Ph)2]2— (R = SitBu3) as well as the hexagallane Ga6R6 (R = SiMe(SiMe3)2) with only six cluster electron pairs were isolated from reactions of “GaI” with the corresponding silanides. The structure of the latter is derived from an octahedron by a Jahn‐Teller‐distortion and is different from the capped trigonal bipyramidal one expected by the Wade‐Mingos rules. Both compounds were characterized by X‐ray crystallography. The bonding is discussed with simplified Ga6H6 and Ga6H62— models via DFT methods. 相似文献
52.
G. Bruno P. Capezzuto G. Cicala F. Cramarossa 《Plasma Chemistry and Plasma Processing》1986,6(2):109-125
Plasma-chemical reduction of SiCl4 in mixtures with H2 and Ar has been studied by optical emission spectroscopy (OES) and laser interferometry techniques. It has been found that the Ar:H2 ratio strongly affects the plasma composition as well as the deposition (r
D) and etch (r
E) rates of Si: H, Cl films and that the electron impact dissociation is the most important channel for the production of SiClx species, which are the precursors of the film growth. Chemisorption of SiClx and the reactive surface reaction SiClx+H–SiCl(x–1)0+HCl are important steps in the deposition process. The suggested deposition model givesr
D [SiClx][H], in agreement with the experimental data. Etching of Si: H, Cl films occurs at high Ar: H2 ratio when Cl atoms in the gas phase become appreciable and increases with increasing Cl concentration. The etch rate is controlled by the Cl atom chemisorption step. 相似文献
53.
As an extention of previous reports, variables affecting the performance of columns modified by silicon deposition have been optimized. The aim of this work was to produce thermostable apolar glass capillary columns regardless of the glass type used and to maintain column performance under stressful conditions. The main parameters studied were the influence of glass type, leaching effects, and silicon layer thickness on column activity. Deactivation and stationary phase conditions were held constant. Both coated and uncoated columns were tested. The thickness of the silicon layer was found to be relatively unimportant. There was no difference whether soft glass or borosiiicate glass was used and leaching before silicon deposition did not influence column activity. Bare silicon surfaces showed considerable activity especially in respect to interactions with free acids and bases. There are indications that the surface consists of silicon oxide and other oxygenated forms of silicon rather than of the element. Treatment of the silicon layers with dilute hydrofluoric acid and the strict exclusion of traces of oxygen and water did not improve the situation. In spite of such specific interactions, silicon surfaces were easily deactivated by heat treatment with polysiloxanes. Silicon surfaces deactivated by baking with octamethyltetrasiloxane at 400°C are inert and temperature stable and show characteristics similar to persilylated surfaces. 相似文献
54.
A stereoselective total synthesis of (S)-Virol C and (S)-1-dehydroxyvirol A has been developed, based upon the selective and sequential substitution of the two trimethylsilyl groups of readily available 1,4-bis(trimethylsilyl)-1,3-butadiyne. 相似文献
55.
The multielement trace analytical method ‘total reflection X-ray fluorescence’ (TXRF) has become a successfully established method in the semiconductor industry, particularly, in the ultra trace element analysis of silicon wafer surfaces. TXRF applications can fulfill general industrial requirements on daily routine of monitoring wafer cleanliness up to 300 mm diameter under cleanroom conditions. Nowadays, TXRF and hyphenated TXRF methods such as ‘vapor phase decomposition (VPD)-TXRF’, i.e. TXRF with a preceding surface and acid digestion and preconcentration procedure, are automated routine techniques (‘wafer surface preparation system’, WSPS). A linear range from 108 to 1014 [atoms/cm2] for some elements is regularly controlled. Instrument uptime is higher than 90%. The method is not tedious and can automatically be operated for 24 h/7 days. Elements such as S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Br, Sn, Sb, Ba and Pb are included in the software for standard peak search. The detection limits of recovered elements are between 1×1011 and 1×107 [atoms/cm2] depending upon X-ray excitation energy and the element of interest. For the determination of low Z elements, i.e. Na, Al and Mg, TXRF has also been extended but its implementation for routine analysis needs further research. At present, VPD-TXRF determination of light elements is viable in a range of 109 [atoms/cm2]. Novel detectors such as silicon drift detectors (SDD) with an active area of 5 mm2, 10 mm2 or 20 mm2, respectively, and multi-array detectors forming up to 70 mm2 are commercially available. The first SDD with 100 mm2 (!) area and integrated backside FET is working under laboratory conditions. Applications of and comparison with ICP-MS, HR-ICP-MS and SR-TXRF, an extension of TXRF capabilities with an extremely powerful energy source, are also reported. 相似文献
56.
We have performed calculations on the fullerene cage and stacked structures of neutral and ionic Si50 cluster by full-potential linear-muffin-tin-orbital molecular-dynamics (FP-LMTO-MD) method. It is found that the neutral and charged fullerene cages relax into distorted structures resembling puckered balls. Their electronic structures are remarkably similar besides their geometrical structures. However, the relaxed cages are still not so stable as the stacked structure built from tricapped trigonal prism. By comparison, for the fullerene cages and stacked structures of neutral and ionic Si60 cluster, similar characteristics are found. 相似文献
57.
Hans Bock 《Angewandte Chemie (International ed. in English)》1989,28(12):1627-1650
Silicon and its compounds have made possible the design of new materials, which, from computers to space travel, have helped to shape the technology of our 20th century. Conversely, the demands of new technology have stimulated the fast development of silicon chemistry as part of the “renaissance” of inorganic chemistry. This article uses selected examples of predominantly organosilicon compounds to discuss in simplified terms the measurement and assignment of suitable spectroscopic “molecular fingerprints” as well as the resulting benefit for the preparative chemist. The comparison of “equivalent” states of “chemically related” molecules is emphasized, based on perturbation arguments and supporting quantum-chemical models. Special attention is given to the relation between structure and energy, which allows us to understand and to predict the connectivity between and the spatial arrangement of silicon “building blocks”, the energy-dependent electron distribution over the effective nuclear potentials of a molecular framework, and, especially, the partly considerable effects of “silicon substituents” on molecular properties. Future-directed extensions and applications include polysilane band structures, Rydberg states of chromophores containing silicon centers, redox reactions and ion-pair formation of silicon-substituted π systems, and molecular dynamic phenomena in solution or on thermal fragmentation in the gas phase. The main objective is a set of clear and practical rules for interpreting measurements and planning experiments. 相似文献
58.
Selective hydrogenation of α,β‐unsaturated carbonyls into saturated carbonyls is important to obtain remunerative products. However, it is still a challenge to achieve high activity and selectivity under mild conditions. Herein, Pd, Ir and bimetallic Pd‐Ir nanoparticles were uniformly deposited with high dispersity on the surface of SiC by a facile impregnation method, respectively. The as‐prepared Pd/SiC catalysts efficiently hydrogenate cinnamaldehyde to hydrocinnamaldehyde at room temperature and atmospheric pressure, and the activity of Pd/SiC is observed further enhanced by adding Ir component (conversion of 100%). In addition, the dependence of Pd‐Ir catalyst activity on Pd/Ir molar ratio confirms a synergistic effect between Ir and Pd, which originates from the electron transfer between Pd and Ir. 相似文献
59.
Tetraallylsilane was functionalised using (chloromethyl)dimethylsilane to give the first generation chloromethyl terminated dendrimer 1. The resulting dendrimer was successfully reacted with K[CpM(CO)2] (Cp=η5-C5H5; M=Fe, Ru) to give Si[(CH2)3SiMe2CH2MCp(CO)2]4 functionalised dendrimers in satisfactory yield. Reaction of dendrimer 1 with NaI in acetone gave the -SiMe2CH2I functionalised dendrimer, while reactions of 1 with K[CpM(CO)3] (M=Mo, W, Re), Li[C5Me4H], Na[C5Me4H], the cobaloxime nucleophile or tert-BuLi were not successful. 相似文献
60.
Agnieszka G?dek 《Journal of organometallic chemistry》2005,690(3):685-690
Photolysis of W(CO)6 in the presence of Ph3SiH in n-heptane leads to the formation of the first tricarbonyl(η6-triphenylhydrosilane)tungsten complex W(CO)3(η6-PhSiHPh2) (1) in good yield (ca. 70%). The molecular structure of the new tungsten-silane compound was established by single-crystal X-ray diffraction studies and characterized by IR, UV-Vis, 1H, 13C{1H}, and 29Si{1H} NMR spectroscopy. 相似文献