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981.
Yukiya Kitayama Kazuya Kishida Hideto Minami Masayoshi Okubo 《Journal of polymer science. Part A, Polymer chemistry》2012,50(10):1991-1996
We have successfully demonstrated the preparation of poly(n‐butyl acrylate)‐b‐polystyrene particles without any coagulation by two‐step emulsifier‐free, organotellurium‐mediated living radical emulsion polymerization (emulsion TERP) using poly(methacrylic acid) (PMAA)–methyltellanyl (TeMe) (PMAA30‐TeMe) (degree of polymerization of PMAA, 30) and 4,4′‐azobis(4‐cyanovaleric acid) (V‐501). The final particle size was ~30 nm and second particle nucleation was not observed throughout the polymerization. Mn increased linearly in both steps with conversion and blocking efficiency was ~75%. PDI was improved by increasing radical entry frequency into each polymer particle due to an increase of the polymerization temperature. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
982.
Dr. Jun Kikuchi Kyohei Takano Dr. Yusuke Ota Dr. Shigenobu Umemiya Prof. Dr. Masahiro Terada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(49):11124-11128
Despite the significant progress of the enantioselective reaction using chiral catalysts, the enantioselective nucleophilic substitution reaction at the chiral sp3-hybridized carbon atom of a racemic electrophile has not been largely explored. Herein, we report the enantioconvergent propargylic substitution reaction of racemic propargylic alcohols with thiols using chiral bis-phosphoric acid as the chiral Brønsted acid catalyst. The substitution products were formed in high yields with high enantioselectivities in most cases. The cation-stabilizing effect of the sulfur functional group introduced at the alkynyl terminus is the key to achieving the efficient enantioconvergent process, in which chiral information originating from not only the racemic stereogenic center but also the formed contact ion pair is completely eliminated from the present system. 相似文献
983.
Dr. Jun Kikuchi Prof. Dr. Masahiro Terada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(40):10215-10225
Over the past decades, the development of enantioselective catalysis using organocatalysts has evolved into an active research field and a number of enantioselective transformations have been established. However, despite their being a highly desirable process for the synthesis of organic molecules in an enantioenriched form, the enantioconvergent substitution reactions of racemic electrophiles using organocatalysts still present several challenges. Although intrinsic difficulties in the catalytic stereocontrol abound due to the initial chiral information of racemic electrophiles, in recent years, mechanistically diverse enantioconvergent processes have been intensively investigated in organocatalysis. This Minireview focuses on recent achievements in the development of enantioconvergent substitution reactions of racemic electrophiles using organocatalysts. The contents are classified on the basis of the mechanistic types of enantioconvergent processes. 相似文献
984.
985.
Dr. Haruhisa Kikuchi Kosuke Kawai Yota Nakashiro Takayuki Yonezawa Kumi Kawaji Prof. Dr. Eiichi. N. Kodama Prof. Dr. Yoshiteru Oshima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(4):1106-1112
The structural diversity of natural products and their derivatives have long contributed to the development of new drugs. However, the difficulty in obtaining compounds bearing skeletally novel structures has recently led to a decline of pharmaceutical research into natural products. This paper reports the construction of a meroterpenoid-like library containing 25 compounds with diverse molecular scaffolds obtained from diversity-enhanced extracts. This method constitutes an approach for increasing the chemical diversity of natural-product-like compounds by combining natural product chemistry and diversity-oriented synthesis. Extensive pharmacological screening of the library revealed promising compounds for anti-osteoporotic and anti-lymphoma/leukemia drugs. This result indicates that the use of diversity-enhanced extracts is an effective methodology for producing chemical libraries for the purpose of drug discovery. 相似文献
986.
987.
988.
Kensuke Shigeta Masafumi Kikuchi Masaki Tanaka Shinya Takasaki Hisashi Oishi Tetsu Sado Yasushi Matsuda Masafumi Noda Yoshinori Okada Nariyasu Mano Hiroaki Yamaguchi 《Biomedical chromatography : BMC》2020,34(8):e4853
Sirolimus is used on patients after solid organ transplantation and on lymphangioleiomyomatosis (LAM) patients, and therapeutic drug monitoring is required in clinical practice. We have previously reported an accurate method for quantitative determination of sirolimus, but its sample preparation step was complicated. In this study, we developed a modified liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI–MS/MS) method for sirolimus quantification. A supported liquid extraction cartridge was used to purify sirolimus from whole blood and ion suppression was mostly prevented. The validation results met the acceptance criteria. This method was compared with the antigen conjugated magnetic immunoassay (ACMIA) and our previously reported method, using whole blood samples from LAM patients. Comparison of the Bland–Altman plots of the currently developed method and the previous method revealed no significant difference between the two methods (mean bias, −2.02%; 95% CI, −7.81–3.78). The values obtained using ACMIA were significantly higher than those obtained using the current method by 13.87% (95% CI, 6.49–21.25) owing to cross-reactivity. The degrees of cross reactivities in LAM patients and in organ transplant patients were similar, and our LC/ESI–MS/MS method precisely measured the blood concentrations of sirolimus. 相似文献
989.
Journal of Thermal Analysis and Calorimetry - In this study, the thermal behavior of the perlite concrete used in a sodium-cooled fast reactor was investigated for obtaining information on a plant... 相似文献
990.
Takuya Kochi Kazuya Ichinose Masayuki Shigekane Taro Hamasaki Fumitoshi Kakiuchi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(16):5315-5319
Sequential formation of distant bonds in organic molecules was achieved for the palladium‐catalyzed hydrosilylation/cyclization of various 1,n‐dienes by chain walking of the metal catalyst. The reaction was applicable to various 1,n‐dienes, including a 1,13‐diene, to form a cyclopentane ring as well as a carbon–silicon bond at a remote site. The use of “nondissociative” chain walking provides a fascinating strategy in organic synthesis to functionalize distant parts of organic molecules, in a particular order, within a catalytic cycle by effectively moving the reactive center from a remote position. 相似文献