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71.
E. Hoffmeister J. E. Kropp T. L. McDowell R. H. Michel W. L. Rippie 《Journal of polymer science. Part A, Polymer chemistry》1969,7(1):55-72
New, bifunctional, bridgehead-substituted triptycenes were synthesized and used to prepare a series of triptycene polymers, including polyesters, polyamides, polyurethanes, and a polyoxadiazole. Certain of these partially aliphatic polymers were thermally stable. Clear and colorless films were obtained in some instances. 相似文献
72.
W. Hoffmeister 《Fresenius' Journal of Analytical Chemistry》1969,245(4):244-246
Zusammenfassung Mittels Röntgenfluorescenz läßt sich der Argongehalt in gesputterten SiO2-Schichten mit Schichtdicken von 100–1500 Å quantitativ ermitteln. Das Nichtvorhandensein eines Argonstandards wird mit Hilfe eines synthetischen Standards aus KCl überwunden. Die Nachweisgrenze liegt unter den benutzten Bedingungen bei 10–7 g Ar. Argongehalte von 1–3 Mol-% wurden in den SiO2-Schichten gefunden.
Vortrag bei der Tagung Analytische Probleme der Reindarstellung von Halbleitern, Wiesbaden, 24./25. 9. 1968.
Mein Dank gilt Herrn Dr. M. Zügel für die Herstellung der gesputterten Argonschichten, und Frl. H. Schumacher für die experimentelle Durchführung der Röntgenfluorescenzanalysen. 相似文献
X-ray fluorimetric determination of argon in SiO2 films made by cathodic sputtering
Films of 100–1500 Å thickness can be analysed. A synthetic standard of KCl is employed as no argon standard is available. With the conditions described the limit of detection is 10–7 g of Ar. Amounts of 1–3 Mol-% have been found in the SiO2 films.
Vortrag bei der Tagung Analytische Probleme der Reindarstellung von Halbleitern, Wiesbaden, 24./25. 9. 1968.
Mein Dank gilt Herrn Dr. M. Zügel für die Herstellung der gesputterten Argonschichten, und Frl. H. Schumacher für die experimentelle Durchführung der Röntgenfluorescenzanalysen. 相似文献
73.
Trefzer A Hoffmeister D Künzel E Stockert S Weitnauer G Westrich L Rix U Fuchser J Bindseil KU Rohr J Bechthold A 《Chemistry & biology》2000,7(2):133-142
BACKGROUND: Urdamycin A, the principle product of Streptomyces fradiae Tü2717, is an angucycline-type antibiotic. The polyketide-derived aglycone moiety is glycosylated at two positions, but only limited information is available about glycosyltransferases involved in urdamycin biosynthesis. RESULTS: To determine the function of three glycosyltransferase genes in the urdamycin biosynthetic gene cluster, we have carried out gene inactivation and expression experiments. Inactivation of urdGT1a resulted in the predominant accumulation of urdamycin B. A mutant lacking urdGT1b and urdGT1c mainly produced compound 100-2. When urdGT1c was expressed in the urdGT1b/urdGT1c double mutant, urdamycin G and urdamycin A were detected. The mutant lacking all three genes mainly accumulated aquayamycin and urdamycinone B. Expression of urdGT1c in the triple mutant led to the formation of compound 100-1, whereas expression of urdGT1a resulted in the formation of compound 100-2. Co-expression of urdGT1b and urdGT1c resulted in the production of 12b-derhodinosyl-urdamycin A, and co-expression of urdGT1a, urdGT1b and urdGT1c resulted in the formation of urdamycin A. CONCLUSIONS: Analysis of glycosyltransferase genes of the urdamycin biosynthetic gene cluster led to an unambiguous assignment of each glycosyltransferase to a certain biosynthetic saccharide attachment step. 相似文献
74.
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76.
The CBELSA/TAPS Collaboration M. Nanova S. Friedrich V. Metag E. Ya. Paryev F. N. Afzal D. Bayadilov B. Bantes R. Beck M. Becker S. Böse K. -T. Brinkmann V. Crede P. Drexler H. Eberhardt D. Elsner F. Frommberger Ch. Funke M. Gottschall M. Grüner E. Gutz Ch. Hammann J. Hannappel J. Hartmann W. Hillert Ph. Hoffmeister Ch. Honisch T. Jude D. Kaiser F. Kalischewski I. Keshelashvili F. Klein K. Koop B. Krusche M. Lang K. Makonyi F. Messi J. Müller J. Müllers D. Piontek T. Rostomyan D. Schaab Ch. Schmidt H. Schmieden R. Schmitz T. Seifen V. Sokhoyan C. Sowa K. Spieker A. Thiel U. Thoma T. Triffterer M. Urban H. van Pee D. Walther Ch. Wendel D. Werthmüller U. Wiedner A. Wilson L. Witthauer Y. Wunderlich H. -G. Zaunick 《The European Physical Journal A - Hadrons and Nuclei》2018,54(10):182
77.
Cover Picture: Biosynthesis of the Halogenated Mycotoxin Aspirochlorine in Koji Mold Involves a Cryptic Amino Acid Conversion (Angew. Chem. Int. Ed. 49/2014) 下载免费PDF全文
78.
Biosynthesis of the Halogenated Mycotoxin Aspirochlorine in Koji Mold Involves a Cryptic Amino Acid Conversion 下载免费PDF全文
Pranatchareeya Chankhamjon Dr. Daniela Boettger‐Schmidt Dr. Kirstin Scherlach Barbara Urbansky Dr. Gerald Lackner Daniel Kalb Hans‐Martin Dahse Prof. Dr. Dirk Hoffmeister Prof. Dr. Christian Hertweck 《Angewandte Chemie (International ed. in English)》2014,53(49):13409-13413
Aspirochlorine ( 1 ) is an epidithiodiketopiperazine (ETP) toxin produced from koji mold (Aspergillus oryzae), which has been used in the oriental cuisine for over two millennia. Considering its potential risk for food safety, we have elucidated the molecular basis of aspirochlorine biosynthesis. By a combination of genetic and chemical analyses we found the acl gene locus and identified the key role of AclH as a chlorinase. Stable isotope labeling, biotransformation, and mutational experiments, analysis of intermediates and an in vitro adenylation domain assay gave totally unexpected insights into the acl pathway: Instead of one Phe and one Gly, two Phe units are assembled by an iterative non‐ribosomal peptide synthetase (NRPS, AclP), followed by halogenation and an unprecedented Phe to Gly amino acid conversion. Biological assays showed that both amino acid transformations are required to confer cytotoxicity and antifungal activity to the mycotoxin. 相似文献
79.
Copper and Silver Carbene Complexes without Heteroatom‐Stabilization: Structure,Spectroscopy, and Relativistic Effects 下载免费PDF全文
M. Sc. Matthias W. Hussong Dipl.‐Chem. Wilhelm T. Hoffmeister Prof. Dr. Bernd F. Straub 《Angewandte Chemie (International ed. in English)》2015,54(35):10331-10335
Salts of a copper and a silver carbene complex were prepared from dimesityl diazomethane, made possible by the steric shielding of the N‐heterocyclic carbene (NHC) ancillary ligand IPr**. The mint‐green complex [IPr**Ag=CMes2]+[NTf2]? is the first isolated silver carbene complex without heteroatom donor substituents. Single‐crystal X‐ray diffraction provides evidence for a predominant carbenoid character, and supports the postulation of such reactive species as intermediates in silver‐catalyzed C? H activation reactions. The greenish yellow copper carbene complex [IPr**Cu=CMes2]+[NTf2]? has spectroscopic properties in between the isostructural silver complex and the already reported emerald green gold carbene complex. A comparison in the Group 11 series indicates that relativistic effects are responsible for the strong σ bond and the significant π back‐bonding in the gold carbene moiety. 相似文献
80.
Spillane T Raiola F Rolfs C Schürmann D Strieder F Zeng S Becker HW Bordeanu C Gialanella L Romano M Schweitzer J 《Physical review letters》2007,98(12):122501
The fusion reactions 12C(12C,alpha)20Ne and 12C(12C,p)23Na have been studied from E=2.10 to 4.75 MeV by gamma-ray spectroscopy using a C target with ultralow hydrogen contamination. The deduced astrophysical S(E)* factor exhibits new resonances at E< or =3.0 MeV, in particular, a strong resonance at E=2.14 MeV, which lies at the high-energy tail of the Gamow peak. The resonance increases the present nonresonant reaction rate of the alpha channel by a factor of 5 near T=8x10(8) K. Because of the resonance structure, extrapolation to the Gamow energy EG=1.5 MeV is quite uncertain. An experimental approach based on an underground accelerator placed in a salt mine in combination with a high efficiency detection setup could provide data over the full EG energy range. 相似文献