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981.
In contrast to earlier reports [2] [8], the pure Cu2+ complex of phthalocyanine-tetrasulfonic acid (I) is found to be inactive in the decomposition of H2O2. The Cu2+ complexes of 1, 4, 8, 11-tetraazacyclotetradecan (II) and 2, 12-dimethyl-3,7,11,17-tetraazabicyclo [11.3.1]-heptadeca-1(17), 2,11,13,15-pentaen (III) are equally inactive. The results confirm that only Cu2+ complexes with a not «saturated» coordination sphere catalyse the decomposition of H2O2. 相似文献
982.
Richard H. Boyd 《Journal of polymer science. Part A, Polymer chemistry》1967,5(7):1573-1583
The effect of volatilization of molecules larger than monomer has been introduced into the solution of the Simha, Wall, and Blatz kinetic equations for the degradation of a high polymer with an initial “most probable” distribution. Equations describing the rate of sample weight and average molecular weight change result. They differ from the previous “most probable” equations primarily in the presence of an additive term representing the random splitting near the chain ends due to bond scission or transfer attack. Equations are also obtained for the rate of formation of each volatile species and hence the product distribution. The effect of volatilization of larger fragments is discussed in detail for the special case of random scission initiation. The product distribution is discussed for two special cases. 相似文献
983.
Zusammenfassung Das in der vorangehenden Mitt. vonE. Späth undF. Gandini-Kesztler beschriebene Nebenalkaloid wird auf synthetischem Wege mit dem 6-Hydroxy-peganin identifiziert. Die phenolische OH-Gruppe steht also, bezogen auf Formel III, nicht an der Stelle, welche dem CH3O des Harmins entspricht. 相似文献
984.
H D Brown 《Journal of chemical information and computer sciences》1983,23(2):78-80
An overview of the environment (from my perspective) related to information resource management in pharmaceutical R & D has been presented. Some notions of organizational preference (functional), employee selection (chemist turned information scientist), automation (user friendly, cost effective), and the value of project teams (information transfer) have been noted. Difficulties associated with keeping our innovative tools sharp were observed. Finally, we noted that our bottom line--productivity--should first consider what is useful (effectiveness) and then learn how to do it well--efficiency. Success in the management of information resources depends on the proactive delivery of information packets which find their way into problem solving and decision support for scientists or line managers. 相似文献
985.
The crystal structure of La3ReO8, prepared at 1425°C, is reported to be different from a previous result on a preparation at 900°C (BAUD et al., 1979). The high temperature modification crystallizes in the monoclinic space group P21/m with a = 7.757(1), b = 7.777(1), c = 5.928(1) Å, γ = 111.1°, Z = 2. The structure was solved by Patterson and Fourier methods from single crystal diffractometer data and refined to final R(F) = 0,073. The structure consists of isolated, distorted ReO6 octahedra and double chains of edge-shared La4O tetrahedra. 相似文献
986.
The kinetics of complexation reaction of Cu(II) with 9-ethyl-3-carbazolecarboxaldehyde-thiosemicarbazone (ECCAT) has been
examined spectrophotometrically. The ligand was synthesized for the first time. The complexation reaction was carried out
in a DMF-water medium at 35°C. The complex has maximum absorbance at 393 nm. Kinetic and activation parameters of the complexation
reaction were calculated by the Arrhenius and Eyring equations using the data obtained from investigating the effect of temperature
on reaction rates under the specified conditions. We also proposed reaction rate equations. Based on the studied complexation
reaction, a simple kinetic method for the spectrophotometric determination of copper(II) has been developed. The calibration
graphs are linear in the concentration range 0.2–1.9 μg/mL. The species that caused interference were investigated.
The text was submitted by the authors in English. 相似文献
987.
The basic obstacles for the general use of laser-ablation(LA)-ICP-MS in analytical laboratories are connected with its reproducibility and calibration. A mathematical relation deduced from the correlation function of the analytical signals allows the estimation of the number of craters needed for representative analyses. The procedure was applied to different samples such as manganese crusts and soils. The ion intensities of the major elements in the manganese crusts and nodules were used as internal standards, improving relative standard deviations by factors between 2 and 3. Selected samples of wood and manganese crusts were analyzed by LA-ICP-MS and the results compared with those obtained by solution ICP-MS. The agreement of the values is within the 95% confidence limits. Powdered reference materials and, in the case of wood analysis, cellulose doped with standard solutions were used for the calibration. 相似文献
988.
D. C. Aumann H. J. Born und R. Henkelmann 《Fresenius' Journal of Analytical Chemistry》1966,221(1):101-108
Zusammenfassung Der intensive Fluß schneller Neutronen, wie er von Kernreaktoren geliefert wird, kann für eine rasche und zerstörungsfreie, aktivierungs-analytische Bestimmung einer Vielzahl von Elementen verwendet werden. Bei manchen Elementen läßt sich sogar bei der Aktivierung mit schnellen Reaktorneutronen eine im Vergleich zur Aktivierungsanalyse mit thermischen Neutronen tiefere Erfassungsgrenze erreichen. Werden die Proben in einem schnellen, halbautomatischen Rohrpostsystem zum Reaktorkern befördert, können auch sehr kurzlebige Radionuklide gemessen werden. Besonders Sauerstoff läßt sich über die Kernreaktion 16O(n, p)16N sehr empfindlich bestimmen, wobei die hochenergetischen -Quanten des 7,2 sec Stickstoff-16 gemessen werden. Es können so bis zu 10 ppm Sauerstoff in vielen Arten von Analysenproben erfaßt werden. Das halbautomatische Analysensystem, das mit Hilfe einer schnellen Rohrpost die Durchführung rascher und zerstörungsfreier Aktivierungs-analysen im Forschungsreaktor München erlaubt, wird beschrieben. Die Verwendung des Systems zur Sauerstoffanalyse und die damit zusammenhängenden Probleme werden genauer besprochen.
Summary The intense fast-neutron fluxes, which are available in nuclear reactors, can be used for rapid and non-destructive activation analysis of many elements. Some elements have even superior detection limits for activation with fast reactor neutrons compared to reactor thermal-neutron activation. Short-lived radionuclides can also be measured using a fast pneumatic tube system. Oxygen can be determined by the nuclear reaction 16O(n, p)16N initiated by fast reactor neutrons counting the high-energy gamma rays of the 7.4 sec nitrogen-16. The method is suitable for determining as little as 10 ppm of oxygen in many types of analytical samples. The fast transfer system, which is used in the Munich research reactor for rapid and non-destructive activation analysis is described. The use of the transfer-system for oxygen activation analysis and problems associated with oxygen analysis are discussed.相似文献
989.
1,4-Cyclohexanedione has been determined by reaction with o-phthalaldehyde in sulfuric acid. The determinations depend on the formation of a dicationic salt of pentacenequinone. A sensitive and highly selective fluorimetric method is recommended, but the reaction can also be used spectrophotometrically. Many organic compounds, as well as the isomers of 1,4-cyclohexanedione, give negative results. A spot test is described which can be used for quick preliminary investigations of complex mixtures for I,4-cyclohexanedione. 相似文献
990.
Wytko JA Michels M Zander L Lex J Schmickler H Vogel E 《The Journal of organic chemistry》2000,65(25):8709-8714
In connection with a study aimed at the evaluation of electronic effects in spiro-dicorrole (1a) and its binuclear Ni(II) complex (1b) we became interested in gem-dimethyl-substituted cyclotetrapyrrole (2a) and the corresponding Ni(II) complex (2b). Attempts to prepare 2a as the 12,13,16,17-tetraethyl-2,3,7, 8-tetramethyl derivative (5) by an acid-catalyzed (1 + 1) condensation of dimethyldipyrrylmethane 3 and diformylbipyrrole 4 resulted in the formation of the (2 + 2) and (3 + 3) condensation products, i.e., the cyclooctapyrrole 6 and the cyclododecapyrrole 7, respectively, rather than in that of the desired gem-dimethyl cyclotetrapyrrole. The cyclododecapyrrole 7, isolated as the major product, is among the largest cyclopolypyrroles known to date. These two new macrocycles have been structurally characterized by variable temperature 1D and 2D NMR experiments, as well as by single-crystal X-ray diffraction analysis. In solution both the cyclooctapyrrole 6 and cyclododecapyrrole 7 exhibit dynamic behavior. At 337 K 6 adopts a D(2)-symmetric conformation, whereas at 196 K two equivalent C(2) conformers that interconvert through the D(2)-symmetric intermediate are observed. The energy barrier for the interconversion process between these two degenerate conformers is found to be 10.6 kcal mol(-)(1). The solution dynamics of 7 could be described in an analogous manner, with the time-averaged conformation at 378 K displaying D(3)(h)() symmetry. X-ray analyses showed that for both macrocycles, 6 and 7, the solid state structures were nearly identical to the low-temperature solution conformers. 相似文献