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781.
K. Burger M. Rudolph E. Windeisen A. Worku S. Fehn 《Monatshefte für Chemie / Chemical Monthly》1993,124(4):453-463
Summary 2,5-Dioxopiperazines with symmetrical as well as unsymmetrical substituent pattern can be obtained via 2,2-bis(trifluoromethyl)-1,3-oxazolidin-5-ones, and 2,5-dioxomorpholines via 2,2-bis-(trifluoromethyl)-1,3-dioxolan-4-ones, respectively.
Herrn Prof. Dr. Wolfgang Beck, Anorganisch-Chemisches Institut der Universität München, mit den besten Wünschen zum 60. Geburtstag gewidmet. 相似文献
782.
Russell Hilf Pauline Bo Leakey Steven J. Sollott Scott L. Gibson 《Photochemistry and photobiology》1983,37(6):633-642
Abstract Primary cultures of the R3230AC mammary adenocarcinoma were used for pharmacokinetic studies of hematoporphyrin derivative (HPD), a preparation containing several porphyrin species and useful as a photoactivatable anti-tumor agent. Uptake of HPD in vitro was shown to be time-, dose- and temperature-dependent with an apparent plateau reached at 2 - 4 h. An increase in the amount of serum in the medium progressively reduced the amount of HPD taken up by the cells; at a level of 10% serum, uptake of HPD was reduced by >95%. The time-course of efflux of HPD from these cells demonstrated a complex pattern, with an initial rapid component followed by a more gradual rate of efflux up to 4 h. Assessment of photoradiation-induced cytotoxicity was performed by a method developed to quantitatively measure trypan blue exclusion. Relative cytotoxicity was determined by use of heat-killed cells as a standard. At two different concentrations of HPD, cytotoxicity was dependent on light exposure time. The presence of serum, which reduced uptake of HPD was correctable to reduced cytotoxicity. Based on the amount of light exposure to produce 50% cell kill, an order of potency was obtained for HPD > hematoporphyrin > hydroxyethylvinyldeuteroporphyrin in vitro. This order of potency correlated with the relative proportion of hydrophobic components as estimated by HPLC analysis. The results indicate that HPD is an effective cytotoxic agent in vitro in a well-differentiated mammary adenocarcinoma model. 相似文献
783.
Zusammenfassung Es wurde die Molekulargewichtsverteilung von Polystyrolen untersucht, die durch Polymerisation von unverdünntem Styrol mit Azoisobutyronitril als Starter (0,5 bis 6·10–3 Mole pro Mol Styrol) im Temperaturbereich von 30–90°C erhalten worden waren. Unter diesen Bedingungen kann die Beteiligung der Kettenübertragung an der Beendigung des Wachstums einer Kettenmolekel vernachlässigt werden. Es wird gezeigt, daß aus den erhaltenen Molekulargewichtsverteilungen der Anteil der Kettenaddition und der Kettendisproportionierung an der Abbruchsreaktion berechnet werden kann. Bei allen untersuchten Proben überwiegt zwar der Additionsanteil, doch ist stets auch eine Radikaldisproportionierung mit Sicherheit festzustellen. Unerwarteterweise nimmt der Additionsanteil mit steigender Polymerisationstemperatur zu. Eine Erklärungsmöglichkeit wird diskutiert.Mit 8 Abbildungen 相似文献
784.
Edgar A. Steck R. Pauline Brundage Lynn T. Fletcher 《Journal of heterocyclic chemistry》1974,11(5):755-761
A series of 6-substituted 3(2H)pyridazinones was prepared. The 6-substituent was either aromatic of heter-aromatic in structure. A few basically-substituted representatives were also made. 相似文献
785.
K. Burger N. Buzás K. Gajda-Schrantz T. Gajda Zs. Nemes-Vetéssy A. Vértes E. Kuzmann I. Dékány M. Szekeres 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》1997,53(14):2525-2536
Combined NMR and Mössbauer investigations were performed on two coordination chemical models of biological interest: an aqueous solution of the N-d-gluconylglycine complex of dimethyltin(IV), and methanolic and aqueous solutions of the ascorbic acid–chloride mixed complex of iron(II). When these solutions were fixed as nanosize droplets in solid matrixes, significant changes occurred in both the structure and the composition of the coordination spheres of the central atoms in the complexes situated in the bulk positions with no direct connection to the surfaces of the holes in the matrix. The phenomenon was attributed to the significant decrease in solvent activity in the pores of the matrix due to the appreciable amount of surface-bound solvent in the system. The model mimics coordination chemical systems in cell tissues. 相似文献
786.
We have compared the reproducibility precisions provided by collaborative trials with precisions obtained from ruggedness tests specially designed to try to simulate between-laboratory variation. We found that the ruggedness tests underestimated the reproducibility variability consistently for those analytical methods requiring empirical calibration. The ruggedness tests provided on average a precision merely comparable with repeatability precision. This finding has implications for the estimation of uncertainty. 相似文献
787.
Rolf Gleiter Klaus Gubernator Mirjana Eckert-Maksi Jens Spanget-Larsen Bernard Bianco Grard Gandillon Ulrich Burger 《Helvetica chimica acta》1981,64(5):1312-1321
The photoelectron (PE.) spectra of 1,2,3-methenoindane ( 2 ), 1,2,3-metheno-2,3-dihydro-1H-cyclopenta [b]naphthalene ( 3 ) and 1,2,3-metheno-2,3-dihydro-1H-phenalene ( 4 ) are investigated. The PE. spectrum of 1,3-methano-2,3-dihydrophenalene ( 7 ) is reported and compared with that of 4 . The experimental results are analyzed in terms of empirical correlation diagrams and the results of semiempirical MINDO/3 and CNDO/S calculations. The analysis indicates that the strong impact of the bicyclobutylene group on the spectroscopic properties of the aromatic π-systems in 2 , 3 and 4 is due to hyperconjugative interactions involving bicyclobutane Walsh orbitals. 相似文献
788.
NO as temporary guanidino-protecting group provides efficient access to Pbf-protected argininic acid
Pbf-protected argininic acid [H-OArg(Pbf)-OH], a building block for Fmoc-solid phase peptide synthesis, is obtained in high yield when a large excess of nitrosating agent is used in conjunction with intermediate Nδ-nitrosyl protection and Nδ-denitrosation in aqueous acidic medium. 相似文献
789.
S. Amberg-Schwab H. Katschorek U. Weber A. Burger R. Hänsel B. Steinbrecher D. Harzer 《Journal of Sol-Gel Science and Technology》2003,26(1-3):699-703
In addition to the barrier properties against water vapor and oxygen, inorganic-organic polymers can also function as protection layers against unwanted migration of chemical substances in two ways. First, hybrid polymers prevent components from migrating out of polymer substrates. This is of special interest for polymeric materials containing substances like plasticizing agents, unreacted monomers or catalysts. Thus the olfactory nuisance and the toxicological emission are decreased. The plastics are also prevented from becoming prematurely brittle. Second, the coated materials are also protected against the interaction of dyes or dirt staining the material.These functions can be achieved by thermally or UV curable coating materials, synthesized by the sol-gel technique. Since several polymer materials show only a low heat resistance (e.g. PVC, polyolefines), this publication is focussed on the development of new migration barriers based on photochemically curable sols.Another advantage of the UV process in comparison to thermal treatments are the short curing times and low power consumption which make this process even more attractive for industrial applications. The coatings were characterized by IR and solid state NMR spectroscopy. The migration barrier properties were tested according to industrial standards.Due to the choice of specific functional groups, these hybrid polymers can be further modified in order to combine the migration barrier function with additional properties: scratch and abrasion resistance, hydrophobicity, antistatic effects. Examples of feasible combinations of properties are also given. 相似文献
790.
Untersuchungen im Dreistoff: Ni−Al−Si sowie von Mono- und Disilicidsystemen einiger Übergangsmetalle
Zusammenfassung An Hand von Schmelzproben wird das Mischungsverhalten einiger Disilicidpaare (V, Cr, Mn, Fe, Co und Ni) festgestellt. VSi2–CrSi2 bilden eine lückenlose Mischreihe; CrSi2 löst rund 25 Molproz. MnSi2; in etwa gleichem Ausmaße lösen einander MnSi2 und FeSi2. Alle übrigen Paare: CrSi2–FeSi2, –CoSi2 bzw.–NiSi2 und MnSi2–CoSi2 bzw.–NiSi2 zeigen nur geringe Mischbarkeit. Auch die Löslichkeit von CrSi2 in MnSi2 ist nicht ausgeprägt.Im Dreistoff Ni–Al–Si werden die ternären Kristallarten Ni(Al0,5Si0,5) mit FeSi-Typ (a=4,528 kX·E.) und Ni3 (Al, Si)7 mit Ir3Ge7-Type (a=8,274 kX·E.) aufgefunden. Der weitgehende Übergang von NiAl nach NiSi2 wird vom Standpunkt der Strukturverwandtschaft diskutiert. Auch in der Phase Ni2Al3 erfolgt ein merklicher Austausch Al/Si.Mit 2 Abbildungen 相似文献