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991.
Carotenoid Glycosyl Esters Synthesis of β-D -Glucosyl 8′-Apo-β-carotene-8′-oate and β-D -Glucosyl Vitamin-A-oate (β-D -Glucosyl Retionate) β-D -glucosyl 8′-apo-β-carotene-8′-oate (III) and β-D -glucosyl vitamin-A-oate (VI) were regio- and stereoselectively synthesized in high yields from the N-acylimidazoles I and IV, respectively, or from the N-acyltriazoles II and V, respectively, and unprotected β-D -glucose, according to the method described for the synthesis of di(β-D -glucosyl) 8,8′-diapo-carotene-8,8′-dioate [1]. It seems that this method can generally be applied for the synthesis of β-D -glucosyl esters of polyene carboxylic acids. 相似文献
992.
Fourier transform infrared (FTIR) spectroscopy has been proven to be an appropriate analytical method for the qualitative assessment of compost stability. This study focuses on quantitative determination of two time-consuming parameters: humic acid (HA) contents and respiration activity. Reactivity/stability and humification were quantified by respiration activities (oxygen uptake) and humic acid contents. These features are also reflected by a specific infrared spectroscopic pattern. Based on this relationship partial least squares regression (PLS-R) models for the prediction of respiration activities and humic acid contents were calculated. Characteristic wavenumber regions that are assigned to the biological/chemical parameter were selected for multivariate data analysis. The coefficient of determination (R2) obtained for the humic acid prediction model from infrared spectra was 87% with a root mean square error of cross-validation (RMSECV) of 2.6% organic dry matter (ODM). The prediction model for respiration activity resulted in a R2 of 94% and a RMSECV for oxygen uptake of 2.9 mg g−1 dry matter (DM). 相似文献
993.
Synthesis of isomeric and homologous spermidine and spermine derivatives and their identification by mass spectrometry. The structure of homologous and isomeric spermidines and spermines follows from mass-spectroscopical analysis of their peracetyl (see text, footnote 3) (Table 1) or tosyl-acetyl (Table 2) derivatives. In the case of the peracetyl compounds, triads of peaks are recorded which, according to the number of methylene groups between the nitrogen atoms, show mass numbers characteristic for each of the substances (Scheme 1, ions b , d , e and c ). On the basis of cyclic ions of type f (Scheme 2), occurring in the mass spectra of N-acetyl derivatives, tosylated on a secondary amino nitrogen atom, deductions can be drawn as to the number of methylene groups between neighbouring tosylated and acetylated nitrogen atoms in these compounds. 相似文献
994.
Armin Guggisberg Hans-Jürgen Veith Manfred Hesse Hans Schmid 《Helvetica chimica acta》1976,59(8):3026-3033
Localization of the keto group in Inandenin-ones . By Schmidt degradation of the spermidine alkaloids inandenine-12-on ( 1 ) and inandenine-13-on ( 2 ) from Oncinotis inandensis followed by hydrolysis, acetylation and esterification four different types of products were obtained: the dicarboxylic diesters 9 and 10 , the ω-amino-carboxylic esters 11 and 12 , the acetylated polyamines 14 and 15 , and the acetylated triaminecarboxylic esters 16 and 17 . By GLC. and mass spectral analysis of these degradation products, and by comparison with synthetic compounds it was possible to confirm the structures 1 and 2 . The same alkaloid mixture ( 1+2 ) was obtained from the leaves of Oncinotis nitida BENTH . 相似文献
995.
Vinylogous epoxyaldehydes undergo stereospecific Wittig condensations in high yields. The resulting diolefinic epoxides are cleaved at the C(1)–C(2) single bond, when treated with periodic acid, to give the corresponding aldehydes. Direct transformation into the corresponding ethyl-ester leads to an efficient synthesis of the ‘pear ester’. 相似文献
996.
Manfred Schubert-Zsilavecz 《Monatshefte für Chemie / Chemical Monthly》1991,122(6-7):545-549
Summary 4a,6-Bis-(N-methylanilino)-7-hydroxy-2,3,8-trimethyl-4a,9a-dihydro-xanthene-dione (4) was obtained by thermolysis of 6-(N-methylanilino)-7a-methyl-3a,7a-dihydroindazol-4,7-dione (1) The structure was determined on basis of 1D- and 2D-NMR techniques.Herrn Prof. Dr. G. Zigeuner zum 70. Geburtstag gewidmet 相似文献
997.
Reaction of (CH3NPF3)2 with equimolar amounts of N-methylhexamethyldisilazane yields a reaction product, which can be separated in a polymer and a crystalline fraction. High-vacuum sublimation of the crystalline part yields the already known compound (CH3N)4P3F7, the new spiro-isomer F3P(CH3N)2PF(CH3N)2PF3 and the spiro-compound F3P(CH3N)2PF(CH3N)2PF(CH3N)2PF3, an isomer of the known compound (CH3N)6P4F8. 相似文献
998.
Five groundwater samples from the former ammunition production site at Elsnig, Germany, were analyzed for highly polar components by LC-NMR and LC-MS. A variety of unknown pollutants could be identified. Possibilities and limitations of the combined use of LC-NMR and LC-MS techniques for on-line identification are discussed. Further unknown components were identified through isolation by HPLC cuts and off-line NMR and MS investigations. Most of the polar compounds in the investigated samples could also be quantified. 相似文献
999.
Katharina Vollmayr Joseph D. Reger Manfred Scheucher Kurt Binder 《Zeitschrift für Physik B Condensed Matter》1993,91(1):113-125
We consider the rounding and shifting of a firstorder transition in a finited-dimensional hypercubicL
d geometry,L being the linear dimension of the system, and surface effects are avoided by periodic boundary conditions. We assume that upon lowering the temperature the system discontinuously goes to one ofq ordered states, such as it e.g. happens for the Potts model ind=3 forq3, with the correlation length of order parameter fluctuation staying finite at the transition. We then describe each of theseq ordered phases and the disordered phase forL by a properly weighted Gaussian. From this phenomenological ansatz for the total distribution of the order parameter, all moments of interest are calculated straight-forwardly. In particular, it is shown that forL exceeding a characteristic minimum sizeL
min the forthorder cumulantg
L
(T) exhibits a minimum atT
min>T
c, withT
min–T
cL
–d and the value of the cumulant and the minimum (g(T
min)) behaving asg(T
min)L
–d. All cumulantsg
L
(T) forL approximately intersect at a common crossing pointT
crossL
–2d, with a universal valueg(T
cross)=1–n/2q, wheren is the order parameter dimensionality. By searching for such a behavior in numerical simulation data, the first order character of a phase transition can be asserted. The usefulness of this approach is shown using data for theq=3,d=3 Potts ferromagnet. 相似文献
1000.
Seeded beam expansions of high-temperature sodium vapour in helium, neon, argon, krypton and nitrogen carrier gases are examined. Photoionization coupled with mass spectroscopic detection is used to determine beam constituents. Contrary to non-seeded supersonic expansions, in which the abundance of sodium clusters observed decreases exponentially with increasing cluster size, large abundances of higher clusters (Nax, x ?65) are observed. Maxima centered at m/z = 161, m/z = 437 and m/z = 874 occur under certain conditions. 相似文献