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991.
K. K. Turgunov A. G. Tojiboev B. Tashkhodjaev KH. M. shakhidoyatov 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(1-2):23-26
The crystal structures of hydrate (1) and anhydrate (2) forms of 2,3-pentamethylene-3,4-dihydroquinazolin-4-one hydrochloride have been determined by X-ray structure analysis. Crystal data of 1 are 2(C13H14N2O)*3(HCl)*4.5 (H2O), triclinic P?1, Z=2, a=8.004(5), b=13.129(7), c=15.725(7) Å, α=106.45(4), β=92.61(4), γ=97.98(5), R=0.0652 and 2 are C13H14N2O*HCl, monoclinic C2/c, Z=8, a=21.360(4), b=5.954(1), c=21.263(4), β=117.89(3), R=0.0556. The crystal of the hydrate form 1is unstable. This form collapses easily with evaporation of H2O and part of HCl molecules from crystals. By recrystallizing destroyed form has been obtained stable crystal form 2. 相似文献
992.
J. P. Pérez-Trujillo S. Frías M. J. Sáchez J. E. Conde M. A. Rodríguez-Delgado 《Chromatographia》2002,56(3-4):191-197
Summary A study of different extraction techniques for the determination of a selected group of organochlorine compounds in surface
waters is presented. Comparison of liquid-liquid extraction (LLE) with solid-phase extraction (SPE) and solid-phase microextraction
(SPME) with fibers of different polarity shows that SPME with a recently commercialised fiber of polydimethylsiloxane divinylbenzene
allows these compounds to be determined in surface waters with good extraction efficiencies. Extraction time, effect of temperature,
ionic strength and pH were optimised, allowing quantification in agricultural effluents in the range 1.0–60 ng·L−1. 相似文献
993.
Summary Chlorobenzenes, triazine and phenylurea herbicides were separated by normal micellar electrokinetic chromatography (MEKC)
and by micellar electrokinetic chromatography with reversed flow (RF-MEKC) in running buffers containing organic solvents.
The relationship between the two techniques is similar to that between reversed-phase and normal-phase HPLC. Using RF-MEKC,
the separation of lipophilic compounds is often improved compared to normal MEKC.
The migration in MEKC and in RF-MEKC was characterised by lipophilic and polar indices. The experimental values of the lipophilic
indices of the compounds tested in the two techniques were close to the indices in reversed-phase HPLC (RP-HPLC). This enables
the use of the indices determined in RP-HPLC for predicting the effects of changing composition of the running buffers on
migration times in MEKC and in RF-MEKC.
Presented at Balaton Symposium '01 on High-Performance Separation Methods, siófok, Hungary, September 2–4, 2001 相似文献
994.
Reactions of perfluoropropylene and its oligomers with acetone oxime in the presence of a base afford perfluoroalkyl and/or perfluoroalkenyl ethers of acetone oxime. When heated to 100 °C, the 3-perfluoro-2-methyl-2-pentenyl ether of acetone oxime (3) is quantitatively converted to 4-hydroxy-3-methyl-5,5-bistrifluoromethyl-4-pentafluoroethyl-1-pyrroline (4), the structure of which was established by X-ray diffraction analysis. A convenient one-stage synthesis of perfluoro-3-isopropyl-4-methyl-3-penten-2-one (7) was proposed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1068–1072, June, 1994. 相似文献
995.
Ana C. D. Medeiros Lidiane P. Correia Mônica O. da S. Simões R. O. Macêdo 《Journal of Thermal Analysis and Calorimetry》2007,88(2):311-315
A number of disintegrants
are available on the market. They improve tablets’ disintegration. The
objective of this work is the comparison of the technological quality parameters
of disintegrants using different analytical techniques. Three batches of disintegrants
and their binary mixtures (water:disintegrants) were investigated. Cooling
experiments were used from –30 up to 200°C. The data obtained showed
calorimetric differences between the samples. In the binary mixtures water
showed different crystallization behaviour from the one found in the literature.
According to the results DSC technique helped the quality control of different
disintegrants. 相似文献
996.
The reaction of o-aminobenzohydroxamic acid with aliphatic, aromatic, or heterocyclic aldehydes leads to the formation of
derivatives of 3-hydroxy-1,2-dihydroquinazolin-4-one.
Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 115–117, January, 1997. 相似文献
997.
I. L. Odinets O. I. Artyushin E. A. Antonov P. V. Petrovskii B. I. Freger T. A. Mastryukova M. I. Kabachnik 《Russian Chemical Bulletin》1994,43(1):121-124
It was shown by31P and13C NMR spectroscopy that methyl(3-carboxy-3-oxopropyl)phosphinic acid (4-methylhydroxyphosphinyl-2-oxobutyric acid) (1) and the amide (2) of the latter exist in keto forms in non-aqueous solutions. In aqueous solutions an equilibrium between the keto,gem-diol, and enol forms has been observed. The proportions of the diol and enol forms increase as the acidity of the media increases. Silylation of acid 1 with hexamethyldisilazane gives the tris(trimethylsilyl) derivative of enol form (3) (Z- andE-isomers).Translated fromIzyestiya Akadetnii Nauk. Seriya Khimicheskaya, No. 1, pp. 125–128, January, 1994. 相似文献
998.
《Electroanalysis》2004,16(5):355-359
Water present in undiluted acetic acid can be monitored in situ with Pt and Au microelectrodes using differential pulse and square‐wave voltammetries. Both reduction and oxidation peaks can be obtained. The best quantitative analytical results were obtained for the anodic peak, the Pt microelectrode, and differential pulse voltammetry. The anodic water peak is located at +1.55 V vs. the quasi reference Pt electrode. The voltammetric peak obtained at Pt electrode is apparently not a diffusional one, however, the calibration plot obtained by employing this peak is linear over a wide concentration range, up to 4 mol dm?3. The detection limit has been estimated as 2.3 mM or 0.0043 v/v%. The developed method may be particularly useful, since the Karl Fischer method can not be used to determine water in glacial acetic acid due to the estrification reaction of acetic acid with methanol. A voltammetric wave of undiluted acetic acid could not be obtained in the positive and negative ranges of potential. 相似文献
999.
Zn3V3O8 two-dimensional micro sheets are successfully synthesized by combination of solvothermal method and heat treatment. The Zn3V3O8 has better electrochemical performances after calcinations. 相似文献
1000.
Helmut Pfitzner und Helmut Schweppe 《Fresenius' Journal of Analytical Chemistry》1974,268(5):337-342
Zusammenfassung In einer früheren Veröffentlichung [4] ist auf die Möglichkeit der chromatographischen Trennung strukturisomerer Metallchelate hingewiesen worden; sie soll hier ausführlicher dargestellt werden. Weiterhin wird die Trennung von 1:2-Mischkomplexen von Azofarbstoffen und von 1:2-Metallkomplex-Mischungen durch Dünnschicht-Chromatographie (DC) an Polyamid beschrieben. Unter bestimmten Voraussetzungen kann durch DC an Kieselgel zwischen 1:2-Metallkomplexfarbstoffen mit Sulfonsäureamid- bzw. Alkylsulfongruppen und solchen ohne diese Substituenten unterschieden werden. Die beschriebenen DC-Methoden ermöglichen bei richtiger Interpretation eine eindeutige Unterscheidung zwischen strukturisomeren Metallkomplexen der 1:1- und 1:2-Reihe, sowie Mischkomplexen und Komplexmischungen vom 1:2-Metall-chelattyp unsulfierter o,o-Dihydroxyazoverbindungen.Symmetrische o,o-Dihydroxyazoverbindungen, wie z.B. das 2,2-Dihydroxy-5,5-dimethyl-azobenzol(7), sind geeignete Komplexbildner für Schwermetallkationen, um diese als farbige Chelate mit Hilfe der DC voneinander zu trennen. Strukturisomere sind wegen der Molekülsymmetrie ausgeschlossen, so daß die Ergebnisse eindeutig sind.
1:1 and 1:2 metal chelates of unsulphonated o,o-dihydroxyazo compounds: A thin-layer chromatographic investigation
In an earlier publication [4] the possibility of the Chromatographic separation of structurally isomeric metal chelates was mentioned; this is dealt with here in more detail. Further the separation of 1:2 mixed complexes from azo dyes and 1:2 metal-complex mixtures by thin-layer chromatography (TLC) on polyamide is described. In certain circumstances it is possible to distinguish between 1:2 metal-complex dyes with sulphonamide or alkylsulphonyl groups and those without these substituents by TLC on silica gel. The TCL methods described allow-when correctly interpreted-an unambiguous distinction between structurally isomeric metal complexes of the 1:1 and 1:2 series, and mixed complexes and mixtures of complexes of the 1:2 metal-chelate type of unsulphonated o,o-dihydroxyazo compounds.Symmetrical o,o-dihydroxyazo compounds, such as 2,2-dihydroxy-5,5-dimethylazobenzene(7), are suitable as complex-formers for heavy-metal ions, allowing the separation of the latter as their coloured chelates with aid of TLC. Structural isomers are excluded because of the molecular symmetry, so that the results are unambiguous.相似文献