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41.
Andrés G. León Ana I. Olives M. Antonia Martín Benito del Castillo 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):577-583
The use of cyclodextrins (CDs) in HPLC as mobile phase additives provides a flexible alternative for the separation of chemically
related compounds because these separations can be performed on conventional columns and are economically advantageous over
the use of chiral stationary phases. The present paper describes the influence of the presence of β-cyclodextrin (β-CD) and
2-hydroxypropyl-β-cyclodextrin (HPβ-CD) on the separation of the β-carboline alkaloids norharmane, harmane and harmine. The
nature of the stationary phase (reverse phases C1 and C18) affects the chromatographic separations and also the stability of the inclusion complexes that are developed. The changes
in the proportion of the organic solvents at constant concentration of CDs (3 mM for β-CD and 15 mM for HPβ-CD) modify the
retention factors (k′) for all alkaloids studied. The nature of the organic solvent in the mobile phase also changes the chromatographic parameters.
The logarithm of the capacity factor (k′) is linearly increased with the proportion of water in the hydro-organic mobile phase (ethanolic or methanolic) but the
slopes obtained vary depending on the CD added to the mobile phase. The role of competitive equilibria, i.e., chromatographic
distribution and inclusion complexes formation is discussed.
This paper was presented at XIIIth International Cyclodextrin Symposium. Torino, Italy, May, 14–17, 2006 相似文献
42.
43.
Enrique Castillo Rosa Eva Pruneda MÓnica Esquivel IV 《International Journal of Mathematical Education in Science & Technology》2013,44(2):209-232
The paper presents a method for generating random linear programming problems with a previously selected type of solution. The user can choose a problem whose solution is unbounded, bounded for minima, maxima or both, unique or multiple, with given structure, at wish. Initially, the feasible solution of the LPP is generated as the sum of a linear space, a cone, and a polytope, depending on the desired properties of the solution. With the aim of obtaining a simple set of constraints, the generators of these three structures are selected as random vectors with integer simple components, the range of which can be given. Next, an objective function that satisfies the required conditions, i.e. leads to a solution of the desired type, is obtained. The generating algorithms have been implemented in Mathematica and some illustrative examples are given to clarify the generation process. With this tool, a LPP can be generated, according to the instructor requirements, where this is a human or an expert system. They can control student progress and generate a sequence of problems covering all possible cases, in steps of increasing difficulty. Combining this tool with another (also produced by the same authors) that solves the problems and explains the whole process, step by step, a computer aided module for learning LPP, which is completely autonomous, can be easily obtained. 相似文献
44.
45.
Optimization Letters - Differential evolution (de) is a popular population-based meta-heuristic that has been successfully used in complex optimization problems. Premature convergence is one of the... 相似文献
46.
Sarah J. R. Staton Josemar A. Castillo Thomas J. Taylor Pierre Herckes Mark A. Hayes 《Analytical and bioanalytical chemistry》2013,405(1):351-357
A substantial portion of the atmospheric particle budget is of biological origin (human and animal dander, plant and insect debris, etc.). These bioaerosols can be considered information-rich packets of biochemical data specific to the organism of origin. In this study, bioaerosol samples from various indoor environments were analyzed to create identifiable patterns attributable to a source level of occupation. Air samples were collected from environments representative of human high-traffic- and low-traffic indoor spaces along with direct human skin sampling. In all settings, total suspended particulate matter was collected and the total aerosol protein concentration ranged from 0.03 to 1.2 μg/m3. High performance liquid chromatography was chosen as a standard analysis technique for the examination of aqueous aerosol extracts to distinguish signatures of occupation compared to environmental background. The results of this study suggest that bioaerosol “fingerprinting” is possible with the two test environments being distinguishable at a 97 % confidence interval. Figure
Generalized schematic of human debris-based occupation detection. The various human occupation-related aerosolized material are collected via the filtration assembly along with other non-related aerosolized material. The collected material was then analyzed for total protein concentration as well as coarsely separated to generated unique pattern profiles. These profiles are information-rich enough to identify human occupation in an indoor space 相似文献
47.
Juan C. Castillo Rodrigo Abonía Justo Cobo Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(7):798-802
In dibenzylammonium hydrogen maleate [or dibenzylammonium (2Z)‐3‐carboxyprop‐2‐enoate], C14H16N+·C4H3O4−, (I), the anion contains a fairly short and nearly linear O—H...O hydrogen bond, with an O...·O distance of 2.4603 (16) Å, but with the H atom clearly offset from the mid‐point of the O...O vector. The counter‐ions in (I) are linked by two N—H...O hydrogen bonds to form C22(6) chains and these chains are weakly linked into sheets by a C—H...O hydrogen bond. Bis(dibenzylamino)methane, C29H30N2, (II), crystallizes with two independent molecules lying across twofold rotation axes in the space group C2/c, and the molecules are conformationally chiral; there are no direction‐specific intermolecular interactions in the crystal structure of (II). 相似文献
48.
Juan C. Castillo Rodrigo Abonía Justo Cobo Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(5):544-548
In the molecule of 4‐(2‐chlorophenyl)pyrrolo[1,2‐a]quinoxaline, C17H11ClN2, (I), the bond lengths are consistent with electron delocalization in the two outer rings of the fused tricyclic system, with a localized double bond in the central ring. The molecules of (I) are linked into chains by a π–π stacking interaction. In (4RS)‐4‐(1,3‐benzodioxol‐6‐yl)‐4,5‐dihydropyrrolo[1,2‐a]quinoxaline, C18H14N2O2, (II), the central ring of the fused tricyclic system adopts a conformation intermediate between screw‐boat and half‐chair forms. A combination of N—H...O and C—H...π(arene) hydrogen bonds links the molecules of (II) into a sheet. Comparisons are made with related compounds. 相似文献
49.
Yelder A. Castillo Luis F. Zapata Jorge Trilleras Justo Cobo Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(1):50-54
The title compound, C23H17N3O4S, crystallizes with Z′ = 3 in the space group P. Two of the three independent molecules are broadly similar in terms of both their molecular conformations and their participation in hydrogen bonds, but the third molecule differs from the other two in both of these respects. The molecules are linked by a combination of N—H...O, N—H...N, C—H...O, C—H...N and C—H...π(arene) hydrogen bonds to form a continuous three‐dimensional framework structure within which a centrosymmetric six‐molecule aggregate can be identified as a key structural element. 相似文献
50.
Bernardita Cayupe Carlos Morgan Gustavo Puentes Luis Valladares Hctor Burgos Amparo Castillo Alejandro Hernndez Luis Constandil Miguel Ríos Patricio Sez-Briones Rafael Barra 《Molecules (Basel, Switzerland)》2021,26(12)
Prenatally malnourished rats develop hypertension in adulthood, in part through increased α1-adrenoceptor-mediated outflow from the paraventricular nucleus (PVN) to the sympathetic system. We studied whether both α1-adrenoceptor-mediated noradrenergic excitatory pathways from the locus coeruleus (LC) to the PVN and their reciprocal excitatory CRFergic connections contribute to prenatal undernutrition-induced hypertension. For that purpose, we microinjected either α1-adrenoceptor or CRH receptor agonists and/or antagonists in the PVN or the LC, respectively. We also determined the α1-adrenoceptor density in whole hypothalamus and the expression levels of α1A-adrenoceptor mRNA in the PVN. The results showed that: (i) agonists microinjection increased systolic blood pressure and heart rate in normotensive eutrophic rats, but not in prenatally malnourished subjects; (ii) antagonists microinjection reduced hypertension and tachycardia in undernourished rats, but not in eutrophic controls; (iii) in undernourished animals, antagonist administration to one nuclei allowed the agonists recover full efficacy in the complementary nucleus, inducing hypertension and tachycardia; (iv) early undernutrition did not modify the number of α1-adrenoceptor binding sites in hypothalamus, but reduced the number of cells expressing α1A-adrenoceptor mRNA in the PVN. These results support the hypothesis that systolic pressure and heart rate are increased by tonic reciprocal paraventricular–coerulear excitatory interactions in prenatally undernourished young-adult rats. 相似文献