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131.
The electrochemical reduction of the title compounds in dimethylformamide affords in all cases stilbene as a major product, leading to the conclusion that cyclization to a three-membered ring containing sulfur is a common feature in these reductions. Other products isolated in the reductions help to shed light upon the course of the reactions. 相似文献
132.
Regioselectivity is observed in -adduct formation between phenylethynyltriisopropoxytitanium and 2(1/H)-pyrimidinones; the new carbon-carbon bond is formed at C(4). In contrast the 3,4- and 3,6-dihydro products are formed together from the corresponding magnesium and lithium reagents, but from the magnesium compound the major product is the 3,6-dihydro isomer. Ethynylmagnesium bromide gives equimolar amounts of the 3,4- and 3,6-dihydro isomers. Dehydrogenation of the products gives the alkynylated aromatic heterocycles. 相似文献
133.
The various calculations of the Delbrück scattering amplitude are presented. This is followed by some generalities on the elastic scattering of photons by heavy atoms and finally by a review of the experiments together with a comparison with the calculations. 相似文献
134.
The ionisation potential shows that fulven-6one is formed pyrolytically from o-benzo-diazo-oxide. Appearance potential measurements show increasing pyrolytic contribution to the [M – N2] species with increase in ion source temperature. 相似文献
135.
Dorota M. Dabrowska Kjell A. Doksum Ryozo Miura 《Annals of the Institute of Statistical Mathematics》1989,41(1):63-79
We consider a two-sample semiparametric model involving a real parameter and a nuisance parameter F which is a distribution function. This model includes the proportional hazard, proportional odds, linear transformation and Harrington-Fleming models (1982, Biometrika, 69, 533–546). We propose two types of estimates based on ranks. The first is a rank approximation to Huber's M-estimates (1981, Robust Statistics, Wiley) and the second is a Hodges-Lehmann type rank inversion estimate (1963, Ann. Math. Statist., 34, 598–611). We obtain asymptotic normality and efficiency results. The estimates are consistent and asymptotically normal generally but fully efficient only for special cases.Research partially supported by National Science Foundation Grant DMS-86-02083 and National Institute of General Medical Sciences Grant SSS-Y1RO1GM35416-01 相似文献
136.
Gunnar Westin Kjell Jansson Annika Pohl Michael Leideborg 《Journal of Sol-Gel Science and Technology》2004,32(1-3):25-29
The molecular alkoxide, ErNb2(OPri)13 was prepared by metathesis with 2KNb(OPri)6, KOPri and ErCl3, and structurally determined by single-crystal X-ray diffraction techniques. Each molecule contains a central Er3+-ion coordinated by six OPri groups of which one is terminal. On each side is an Nb5+-ion coordinated by six OPri groups placed, one via a double alkoxo-bridge and the other via a triple alkoxo-bridge. It is isostructural with LaNb2(OPri)13, in spite of the large difference in ionic radius between Er3+ and La3+ (16%). The compound was characterized by its IR- and UV-vis-NIR-spectroscopic fine structures, and found to be structurally intact in hexane:isopropanol solution. 相似文献
137.
3-Vinyl derivatives of 4(3H)-pyrimidinethiones have been prepared from 2,3-dihydrothiazolo[3,2-c]pyrimidinium derivatives through ring-opening by a strong base such as potassium t-butoxide in DMF. The pyrimidinium derivative is initially prepared from 4(3H)-pyrimidinethiones. 3-Vinyl-4(3H)-pyrimidinethiones are also formed by the ready decarboxylation of 2,3-dihydrothiazolo[3,2-c]pyrimidinium-3-carboxylates. In the mass spectrometer the nature of the volatile species was elucidated by means of appearance potentials and fragmentation patterns. 相似文献
138.
A representation of total angular momentum conservation in energy space is described. Several advantages of such a representation are discussed, primarily in connection with statistical unimolecular theory, experimental branching ratios and product energy distributions. Specific examples are given for the systems K + CsF and O + I2. 相似文献
139.
A method for the determination of exhaled ethane, pentane and isoprene was developed and validated. The method was based on pre-concentration of the analytes on a multi-bed solid adsorbent tube containing Tenax TA, Carboxen 569 and Carboxen 1000, thermal desorption and gas chromatography (GC) with flame ionisation detection (FID). A pre-column in an end-cut GC system was used to avoid problems with water and strongly retained substances. The detection limits were 5, 2 and 6 pmol per sample for ethane, pentane and isoprene, respectively, using a sample volume of 500 ml. The linearity was good for all analytes with correlation coefficients exceeding 0.999. The repeatability for exhaled air samples was 7, 10 and 12% for ethane, pentane and isoprene, respectively. Analysis of a certified reference material of ethane and pentane did not differ significantly from the certified values. Ethane and pentane levels were stable up to six days of storage in sample tubes. Isoprene levels were not stable during storage in the sample tubes used here, but using Carbopack X instead of Carboxen 569, levels were stable up to two days. The levels of exhaled ethane, pentane and isoprene in healthy subjects (n = 4) were 8.1+/-5.8 pmol l(-1), 11+/-5.8 pmol l(-1) and 2.4+/-0.90 mnol l(-1), respectively. The method could, with minor modifications, be used to determine other low-molecular hydrocarbons in exhaled air as well. 相似文献
140.
Kjell Nilsson Peter Brodelius Klaus Mosbach 《Applied biochemistry and biotechnology》1982,7(1-2):47-49
The yeast,Trigonopsis variabilis, was immobilized by entrapment in alginate. The immobilized cells containing high amounts of D-amino acid oxidase were used
to convert D-amino acids to their corresponding α-keto acids. 相似文献