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81.
S Drescher G Hempel WH Binder B Dobner A Blume A Meister 《Langmuir : the ACS journal of surfaces and colloids》2012,28(31):11615-11624
In the present work, we describe the successful stabilization of bolalipid nanofibers by sol-gel condensation (silicification) of tetraethoxysilane (TEOS) or 3-mercaptopropyltriethoxysilane (MP-TEOS), respectively, onto the nanofibers. The conditions for an effective and reproducible silicification reaction were determined, and the silicification process was pursued by transmission electron microscopy (TEM). The resulting bolalipid-silica composite nanofibers were characterized by means of differential scanning calorimetry (DSC), TEM, (13)C, and (31)P NMR spectroscopy. Finally, the novel silicified bolalipid nanofibers were used as templates for the fixation of 5 and 2 nm AuNPs, respectively, resulting in one of the rare examples of one-dimensional AuNP arrangements in aqueous suspension. 相似文献
82.
Alfred D. French 《Cellulose (London, England)》2011,18(4):889-896
Thorough conformational study of cellobiose requires consideration of numerous arrangements of the exocyclic groups. Therefore,
it is customary to prepare a number of structures with different arrangements of hydroxyl and hydroxymethyl groups. These
“starting geometries” are then given different values of the glycosidic linkage torsion angles ϕ and ψ. At each increment
of ϕ and ψ, the energy is calculated. Usually, the final product is an “adiabatic” contour plot of the lowest energy at each
ϕ/ψ point after considering all of the starting geometries. The present paper advocates for adiabatic maps despite the statement
by Schnupf and Momany (preceding paper) that adiabatic maps are not of interest because they contain sparse details about
the structures at each minimum. Similar information is computed by their method and adiabatic mapping, and comparable details
can be provided from adiabatic studies. Although Schnupf and Momany presented maps from calculations in vacuum and in water
that considered all of their calculated energies, they favored the presentation of two to four maps for each of 36 individual
minima, each with its own zero of relative energy. However, previous work showed that more structures are needed to provide
the lowest energies at each point in ϕ/ψ space. Following their preferred strategy would result in even more maps when the
added structures are considered. The need to map individual minima can be avoided by starting calculations with the same exocyclic
orientations at each ϕ/ψ point instead of using the preceding optimized structure to start the next energy minimization. Using
the same orientations at each point allows periodic maps that depict barriers between minima. 相似文献
83.
Isobaric tagging reagents such as isobaric tag for relative and absolute quantitation (iTRAQ) and tandem mass tag (TMT) typically have isotopic impurities that cause significant cross‐talk between channels. Here, we present an efficient solution to compensate for channel cross‐talk using linear algebra and find that it is between 20× and 120× faster than previous methods. We also find that the effects of channel cross‐talk are as important to manage as the effects of ratio compression because of precursor impurities, and we have released an open‐source tool to perform both types of calculations. 相似文献
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Ohne Zusammenfassung 相似文献
86.
Silvia E. Braslavsky Alfred R. Holzwarth Harald Lehner Kurt Schaffner 《Helvetica chimica acta》1978,61(6):2219-2222
Freshly prepared solutions of biliverdin dimethyl ester ( 2 ) in ethanol showed fluorescence maxima at 710 and 770 nm [ΦF = 1.1. 10?4 (room temperature) and 5.0 10?4 (77 K)]. The maxima of monoprotonated 2 at 77 K were shifted to 725 and 806 nm and the quantum yield was increased to 2.6. 10?2. This acid effect was reversible by neutralization with base. When a neutral solution was kept standing in the dark at room temperature, or when an acidic solution was neutralized by base, an additional fluorescence maximum at 500 nm with a mirror image excitation spectrum with λmax = 470 nm developed, which disappeared on addition of acid and which is attributed to a chemical change of 2 . 相似文献
87.
Syntheses of Sulfonated Derivatives of 4-Amino-1, 3-dimethylbenzene and 2-Amino-1, 3-dimethylbenzene Direct sulfonation of 4-amino-1, 3-dimethylbenzene (1) and sulfonation of 4-nitro-1,3-dimethylbenzene ( 4 ) to 4-nitro-1,3-dimethylbenzene-6-sulfonic acid ( 3 ) followed by reduction yield 4-amino-1,3-dimethylbenzene-6-sulfonic acid ( 2 ). The isomeric 5-sulfonic acid ( 5 ) however is prepared solely by baking the acid sulfate salt of 1 . Reaction of sulfur dioxide with the diazonium chloride derived from 2-amino-4-nitro-1,3-dimethylbenzene ( 7 ) leads to 4-nitro-1,3-dimethylbenzene-2-sulfonyl chloride ( 8 ), which is successively hydrolyzed to 4-nitro-1,3-dimethylbenzene-2-sulfonic acid ( 9 ) and reduced to 4-amino-1, 3-dimethylbenzene-2-sulfonic acid ( 6 ). Treatment of 4-amino-6-bromo-1,3-dimethylbenzene ( 12 ) and 4-amino-6-chloro-1, 3-dimethylbenzene ( 13 ), the former obtained by reduction of 4-chloro-6-nitro-1,3-dimethyl-benzene ( 10 ) and the latter from 4-chloro-6-nitro-1, 3-dimethylbenzene ( 11 ), with oleum yield 4-amino-6-bromo-1,3-dimethylbenzene-2-sulfonic acid ( 14 ) and 4-amino-6-chloro-1,3-dimethylbenzene-2-sulfonic acid ( 15 ) respectively; subsequent carbon-halogen hydrogenolyses of 14 and 15 lead also to 6 (Scheme 1). Baking the acid sulfate salt of 2-amino-1, 3-dimethylbenzene ( 17 ) gives 2-amino-1, 3-dimethylbenzene-5-sulfonic acid ( 16 ), whereas the isomeric 4-sulfonic acid ( 18 ) can be prepared by either of the following three possible pathways: Sulfonation of 2-nitro-1,3-dimethylbenzene ( 20 ) to 2-nitro-1,3-dimethylbenzene-4-sulfonic acid ( 21 ) followed by reduction or sulfonation of 2-acetylamino-1,3-dimethylbenzene ( 19 ) to 2-acetylamino-1,3-dimethylbenzene-4-sulfonic acid ( 22 ) with subsequent hydrolysis or direct sulfonation of 17 . Further sulfonation of 18 yields 2-amino 1,3-dimethylbenzene-4,6-disulfonic acid ( 23 ), the structure of which is independently confirmed by reduction of unequivocally prepared 2-nitro- 1,:3-dimethylbenzene-4,6-disulfonic acid ( 24 )(Scheme 2). 相似文献
88.
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90.
Dieter Weber Günther Burget Karl-Heinz Zirzow Hans Georg Von Schnering Alfred Schmidpeter 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4)
Abstract Alkalimetal diphenylphosphinites degrade (Ph-P)5 and P4 to give anions containing a chain of 2, 3 or 4 four- and two-coordinated phosphorus atoms. Representatives of the chain with two four-coordinated and one two-coordinated P atoms became first available from the aminolysis of tris (phosphoryl)phosphides1. 相似文献