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81.
Watson William H. Kashyap Ram P. Krawiec Mariusz Marchand Alan P. Tsay Fuh-Rong 《Structural chemistry》1994,5(1):21-35
5-Methyl-2-phenylpentacyclo[5.4.0.02, 6.03, 10.05, 9]undecane-8, 11-dione,5-methyl-2-phenylpentacyclo [5.4.0.02,6.03,10.05,9]undecane-8-one-11-ol,and 5-methyl-2-phenylpentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-diol are three cage compounds which differ only in the oxidation state at C(8) and C(11). The three compounds contain a four-membered, a six-membered, and four five-membered rings fused into a cagelike structure. An X-ray structure analysis shows the C(1)-C(7) and C(9)-C(10) bonds in the diketo cage to be 1.606(2) and 1.586(2) Å, which are significantly longer than in the other two molecules. In order to assess the effects of strain, steric, and electronic factors in these compounds, we investigated the unsubstituted parent cage compounds and a series of derivatives by molecular mechanics (MM3), AMPAC (AM1), MOPAC (PM3), and GAUSSIAN 90 calculations. These data suggest that dipolar through space interactions are responsible for the bond elongation and not a
–
* interaction, which has been postulated in parallel-systems originating from a common bond. A small degree of
–
* through-bond interaction may contribute to the lengthening in the dimethylene cage analogues. 相似文献
82.
New multiresidue analytical method dedicated to trace level measurement of brominated flame retardants in human biological matrices 总被引:1,自引:0,他引:1
Cariou R Antignac JP Marchand P Berrebi A Zalko D Andre F Le Bizec B 《Journal of chromatography. A》2005,1100(2):144-152
A new method has been developed for the multi-residue measurement of the main brominated flame retardants (alpha- and gamma-hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBP-A) and polybrominated diphenyl ethers including decabromodiphenyl ether) in human biological matrices (serum, adipose tissue and breast milk). The proposed sample preparation procedure focused on reduced solvent and consumable consumption and associated procedural contamination, as well as reduced sample size. This protocol was fully validated and was proved to be suitable for identification of brominated flame retardant residues at ultra-trace level, as attested by preliminary results on real samples. 相似文献
83.
Catherine Michaux Claudio Salvagnini Bernadette Norberg Jacqueline Marchand‐Brynaert Johan Wouters 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(12):o691-o693
In the title compound, C18H27F3N5O3S+·Cl−, the guanidine group forms N—H⋯Cl hydrogen bonds, with four N⋯Cl distances in the range 3.164 (3)–3.337 (4) Å. In the crystal packing, the cations are further linked by N—H⋯O and C—H⋯O interactions. The structure is compared with that of argatroban complexed with thrombin and is the subject of docking studies in the active site of thrombin. 相似文献
84.
A. Adam F. Schmidt B. Tollens Marchand Grote F. Soxhlet Szombathy A. Wynter Blyth Boorhoeve Ph. du Roi F. Clausnizer Adolf Mayer N. Gerber und P. Radenhausen 《Fresenius' Journal of Analytical Chemistry》1880,19(1):362-368
Ohne Zusammenfassung 相似文献
85.
Eleven cyanopropyl ("cyano") columns were characterized by means of a relationship developed originally for alkyl-silica columns. Compared to type-B alkyl-silica columns (i.e., made from pure silica), cyano columns are much less hydrophobic (smaller H), less sterically restricted (smaller S*), and have lower hydrogen-bond acidity (smaller A). Because sample retention is generally much weaker on cyano versus other columns (e.g., C8, C18), a change to a cyano column usually requires a significantly weaker mobile phase in order to maintain comparable values of k for both columns. For this reason, practical comparisons of selectivity between cyano and other columns (i.e., involving different mobile phases for each column) must take into account possible changes in separation due to the change in mobile phase, as well as change in the column. 相似文献
86.
87.
88.
A simple and efficient two-step, one-pot synthesis of substituted 1,4-dihydro-1,4-methanonaphthalene-5,8-diones is reported. This synthesis, which utilizes readily available starting materials and inexpensive reagents, can be used to prepare 1a-1c in 70–90% overall yield. This procedure was extended successfully to prepare a more highly complex annulated p-benzoquinone i.e., 8. 相似文献
89.