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22.
Palanisamy Shanmugasundaram K. Joseph Prabahar Vayalakkavoor T. Ramakrishnan 《Journal of heterocyclic chemistry》1993,30(4):1003-1007
Synthesis of 10-aryl-3,4,6,7,9,10-hexahydro-1,8(2H,5H)-acridinedione as a new class of laser dyes is reported. These dyes lase around 475–495 nm and are compared to the standard dye coumarin 102. 相似文献
23.
The use of multi-dimensional “chemistry spaces” to represent large compound collections has become widespread in pharmaceutical
research. In such spaces compounds are treated as points. Points in close proximity represent similar compounds, while distant
points represent dissimilar compounds. Assessing the diversity of a compound collection, thus, is tantamount to characterizing
the distribution of points in chemistry space. To facilitate many procedures such as selecting subsets of compounds for screening,
for compound acquisition and designing combinatorial libraries, chemistry spaces have been partitioned into sets of non-overlapping,
multi-dimensional cells, which are generated by dividing each axis into a number of equal-sized bins. This leads to a lattice
of (Nbins)Ndim{(N_{bins})^{N_{\rm dim}}} cells, where N
bins
is the number of bins on each axis and N
dim is the dimensionality of the space. One diversity measure that is typically used in cell-based chemistry spaces is identical
in form to Shannon entropy, DNcpdcpd{D_{N_{cpd}}^{cpd}} A normalized measure of this Shannon entropy given by, Drelcpd{D_{rel}^{cpd}} enables comparison between compound collections that occupy different number of occupied cells. Although Drelcpd{D_{rel}^{cpd}} characterizes the uniformity and “spreadout” of the corresponding compound collection, it treats cells as positionally independent. Some of the positional information lost can be recaptured by another diversity measure, which is also related in form to
Shannon entropy. This new measure DNbincell (l){D_{N_{bin}}^{cell} (\lambda)} characterizes the distribution of occupied cells along each axis of chemistry space. The normalized measure
á Drelcell
ñ{\left\langle {D_{rel}^{cell}}\right\rangle} over all axes is given then by the average. Examples illustrating the applicability of these two Shannon-like measures to
compound collections are presented. 相似文献
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25.
The gluco‐configured C(2)‐substituted tetrahydroimidazopyridines 8 – 14 were prepared and tested as inhibitors of the β‐glucosidases from Caldocellum saccharolyticum and from sweet almonds, and of the α‐glucosidase from brewer's yeast. All new imidazopyridines are nanomolar inhibitors of the β‐glucosidases and micromolar inhibitors of the α‐glucosidase. The 3‐phenylpropyl derivative 14 proved the strongest inhibitor of the Caldocellum β‐glucosidase (Ki = 0.9 nM ), only slightly weaker than the known 2‐phenylethyl analogue 7 , and the propyl derivative 13 is the strongest inhibitor of the sweet almond β‐glucosidases (Ki = 3.2 nM ), again slightly weaker than 7 . There is no strong dependence of the inhibition on the nature of the C(2)‐substituent and no clear correlation between the inhibitory strength of the known manno‐configured imidazopyridines 2 – 6 and the gluco‐analogues 8 – 12 . While most manno‐imidazopyridines are competitive inhibitors, the gluco‐analogues proved non‐competitive inhibitors of the Caldocellum β‐glucosidase and mixed‐type or partial mixed‐type inhibitors of the sweet almond β‐glucosidases. 相似文献
26.
Devaraj Somasundaram Kalpattu K. Balasubramanain Bhagavathy Shanmugasundaram 《Tetrahedron letters》2019,60(11):764-767
The ring opening of α-d-1,2-anhydrohexapyranoses with phenols proceeded smoothly in ethyl acetate (neutral conditions) in the absence of metal ion catalysts or additives to stereoselectively furnish 1,2-cis-α-aryl glycosides as the major product and 1,2-trans-β-aryl glycosides as the minor product in good yields. Under similar conditions, this ring opening reaction with alcohols afforded exclusively β-alkyl glycosides in excellent yields. 相似文献
27.
Santhanaraman Manikandan Muthian Shanmugasundaram Raghavachary Raghunathan 《Heteroatom Chemistry》2001,12(6):463-467
Synthesis of a series of novel spiro[3,4‐diaryl‐4,5‐dihydroisoxazole‐5,2′‐1′,2′,3′,4′‐tetrahydro‐1′‐naphthalenone] has been described by the regioselective cycloaddition of nitrile oxides with 2‐arylmethylene‐1,2,3,4‐tetrahydro‐1‐naphthalenone. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:463–467, 2001 相似文献
28.
A methodology, derived by analogy to Shannon’s information-theoretic theory of communication and utilizing the concept of mutual information, has been developed to characterize partitioned property spaces. A family of non-intersecting subsets that cover the “universe” of objects represents a partitioned property space. Each subset is thus an equivalence class. A partition and it’s associated equivalence classes can be generated using any one of a number of procedures including hierarchical and non-hierarchical clustering, direct approaches using rough set methods, and cell-based partitioning, to name a few. Thus, partitioned property spaces arise in many instances and represent a very large class of problems. The approach is based on set-valued mappings from equivalence classes in one partition to those in another and provides a coarse-grained means for comparing property spaces. From these mappings it is possible to compute a number of Shannon entropies that afford calculation of mutual information, which represents that amount of information shared by two partitions of a set of objects. Taking the ratio of the mutual information with the maximum possible mutual information yields a quantity that measures the similarity of the two partitions. While the focus in this work is directed towards small sets of objects the approach can be extended to many more classes of problems that can be put into a similar form, which includes many types of cheminformatic and biological problems. A number of scenarios are presented that illustrate the concept and indicate the broader class of problems that can be handled by this method. 相似文献
29.
30.
Zusammenfassung Auf Grund von Symmetrieüberlegungen wurden aus den kürzlich erhaltenen Schwingungs- und Strukturdaten des Dichlorfluoramins und des Difluorchloramins, die beide Cs-Symmetrie besitzen, Schwingungskonstanten, wie die Schwingungskraftkonstanten und die mittleren Schwingungsamplituden, spektroskopisch ermittelt. Die Bindungskraftkonstanten der genannten Moleküle wurden unter Verwendung eines Bindungskraftfeldes von sechs Konstanten errechnet. Weiters wurden die mittleren Schwingungskonstanten sowohl der gebundenen als auch der nichtgebundenen Atompaare für Zimmertemperatur berechnet. Schließlich wurden unter Annahme eines starren Rotators und harmonischen Oszillators die statistischen thermodynamischen Funktionen für den Temperaturebereich von 200–2000° K berechnet. Eine kurze Diskussion ist angeschlossen.
Mit 1 Abbildung 相似文献
Vibrational constants and thermodynamic functions of difluorochloramine and dichlorofluoramine
On the basis of symmetry considerations, vibrational constants such as valence force constants and mean amplitudes of vibration have been spectroscopically evaluated from the recent vibrational and structural data for NF2Cl and NCl2F possessing a Cs symmetry. Valence force constants by employing a six-constant valence force field and mean amplitudes of vibration for both bonded and nonbonded atom pairs at the room temperature have been computed for these molecules. In addition to these, statistical thermodynamic functions have
Mit 1 Abbildung 相似文献