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991.
Anion recognition through novel C-thiophenecalix[4]resorcinarene: PVC based sensor for chromate ions
Novel ionophore, C-thiophenecalix[4]resorcinarene (I) has been synthesized and characterized by IR, NMR and C, H, N analysis. Poly(vinyl chloride) (PVC) based membranes of ionophore (I) using dibutylphthalate (DBP), dioctylphthalate (DOP), 1-chloronapthalene (CN), tris(2-ethylhexyl) phosphate (TEHP) and bis(2-ethylhexyl)sebacate (DOS) as plasticizing solvent mediators were prepared and used as Cr selective sensors. Of the various sensors prepared, the one with membrane composition 2:66:120 mg (I: PVC: DBP) exhibited the best performance. This sensor works well over a wide concentration range 5.6 × 10−6-1.0 × 10−1 M (detection limit ∼ 0.30 ppm) with Nernstian compliance (29.0 mV per decade) between pH 6.5-10.0 with a fast response time of ∼13 s. The selectivity coefficient values as determined by fixed interference method (FIM) indicate excellent selectivity for Cr ions over a large number of anions. The sensor exhibits adequate shelf-life ( ∼5 months) with good reproducibility (S.D. ± 0.2 mV). The sensor has been used in the potentiometric titration of chromate with Pb(II). Determination of chromium in electroplating waste using the sensor was successfully achieved. 相似文献
992.
Glycine cresol red (G. C. R) has been used as a complexometric indicator and a reagent for the spectrophotometric determination of inorganic ions1-4. It forms stable coloured chelates iusolution with some metal ions under appropriate conditions. This communication give the composition and stability of tungsten G. C. R. Chelate. 相似文献
993.
The composition and stability of the chelate formed between Zr(IV) and chromotrope 2R has been investigated using spectrophotometric methods. The chelate is violet in color and has λmax at 530 nm. The composition, determined by different methods is 1 : 1. The chelate is stable between pH 1.0-3.0. The value of log K as determined by two different methods are 4.48±0.2 and 4.21±0.1 and the values of free energy of formation are —6.21±0.2 and —5.83±0.1 respectively at 30°C. The system obeys Beer's Law over a concentration range of 2.50 to 20.0 ppm of zirconium. The effective range of photometric determination is 3.50 to 19.05 ppm of zirconium. 相似文献
994.
Summary Halogen oxidation of several LMo(CO)s andcis-L2Mo(CO)4 (L = Ph3P1Ph3As and Ph3Sb) derivatives has been studied. The LMo(CO)5 complexes react with halogens to give hexacoordinate LMo(CO)3 X2 (X = Cl, Br or I) derivatives which are of very rare occurrence. Similar reactions withcis-L2Mo(CO)4 give heptacoordinate L2Mo(CO)3X2 derivatives. The complexes have been characterised by elemental analysis, i.r. and conductivity measurements. 相似文献
995.
Srivastava A Ghorai S Bhattacharjya A Bhattacharya S 《The Journal of organic chemistry》2005,70(17):6574-6582
A novel low-molecular mass tetrameric sugar derivative containing azobenzene core, 1, showed pronounced hydrogelation at micromolar concentration. Based on this observation, four related azobenzene based tetrameric sugar derivatives, 4-7, and three tetrameric sugar derivatives with a bis-terephthalamide core, 9-11, were also synthesized. However, none of these closely related analogues of the compound 1 showed effective gelation. The gel formed from 1 was characterized extensively using melting temperature analysis, UV-vis, FT-IR, circular dichroism spectroscopy, and scanning electron microscopy. The resultant gel exhibited impressive tolerance to the pH variation of the aqueous phase and gelated water in the pH range of 4-10. While UV-vis and CD spectroscopy indicated that pronounced aggregation of the azobenzene chromophores in 1 was responsible for gelation, FT-IR studies showed that hydrogen bonding is also a contributing factor in the gelation process. The melting of gel was found to depend on the pH of the aqueous medium in which gel was formed. The gel showed considerable photostability to UV irradiation, indicating tight intermolecular packing inside the gelated state that rendered azobenzene groups in the resultant aggregate refractory to photoisomerization. The electron micrographs of the aqueous gels of 1 showed the existence of spongy globular aggregates in such gelated materials. Addition of salts to the aqueous medium led to a delay in the gelation process and also caused remarkable morphological changes in the microstructure of the gel. 相似文献
996.
T. N. Srivastava A. K. S. Chauhan Miss Manjula Agarwal 《Transition Metal Chemistry》1978,3(1):378-379
Summary Binuclear complexes of phenyltin(IV) chlorides with transition metal chelates of tetradentate Schiff bases derived from acetylacetone, benzoylacetone oro-hydroxyacetophenone and ethylenediamine or propylenediamine, of the general formula PhnSnCl4-nML (where n = 1 or 2, M = Ni11 or Cu11 and L2–= the Schiff base dianion), have been synthesised and characterized through elemental analysis, conductance and i.r. spectroscopic data. The coordination of metal chelates to tin involves two triply bonded oxygen atoms giving rise to an octahedral environment around SnIV. The molar conductance of the complexes in nitrobenzene shows the presence of the uncoordinated ML and phenyltin(IV) chloride moieties in solution.Author to whom all correspondence should be directed. 相似文献
997.
The metal chelates of V(IV), Mo(VI) and W(VI) formed with asparagine and glutamine have been studied potentiometrically. Stepwise stability constants in O.1M sodium perchlorate at 25 degrees C are reported as follows. Asparagine chelates--log K(1)K(2) 14.50 and log K(3) 4.04 for V, log K(1) 8.06, log K(2) 7.29 and log K(3) 3.45 for Mo, and log K(1) 5.84, log K(2) 5.11 and log K(3) 3.30 for W. Glutamine chelates--log K(1)K(2) 14.45, and log K(3) 4.07 for V, log K(1) 7.90, log K(2) 6.93, and log K(3) 3.35 for Mo, and log K(1) 5.76, log K(2) 5.09 and log K(3) 3.20 for W. 相似文献
998.
Summary A direct complexometric titration of iron(III) with EDTA using o- and p-cresotic acids indicators is given. The colour change at the end point is from blue-violet to light yellow or colourless [at low concentrations of iron(III)]. The optimum range of pH and temperature for carrying out the titrations is 1.99 to 4.2 and 35° to 55°C and 1.42 to 4.4 and 30° to 60° C, respectively. Iron(III) may easily and accurately be estimated in macro- and micro-gram quantities with the help of these metal indicators. Be, Mg, Ca, Sr, Ba, Cd, UO2 and Mn are without any interference in the estimation. Back titration procedures for determination of zirconium and thorium with iron(III) and o- and p-cresotic acids are carried out.Part V: See Z. analyt. Chem. 173, 196 (1960). 相似文献
999.
The paper describes the synthesis and characterization of comb polymers by a two-step chemo-enzymatic process. In the first step macromonomers bearing unsaturation at the chain end were prepared by lipase catalyzed ring-opening polymerization (ROP) of ε-caprolactone (CL) and 1,5-dioxepane-2-one (DXO). The ROP was carried out in bulk at 60 °C under anhydrous conditions using 2-hydroxyethyl methacrylate (HEMA) as the initiator. The DP of the macromonomers was controlled by regulating the monomer: HEMA molar feed concentration. The macromonomers were then homo- or co-polymerized in the second step with alkyl methacrylate monomers (methyl methacrylate or HEMA) using AIBN initiated free radical polymerization. Characterization of the polymers was done by 1H NMR, SEC and DSC techniques. 相似文献
1000.
Seema Tripathi A. K. Srivastava 《Journal of polymer science. Part A, Polymer chemistry》2004,42(9):2060-2065
Triphenylbismuthonium 1,2,3,4‐tetraphenylcyclopentadienylide in 1,4‐dioxan initiated radical polymerization of methyl acrylate to ~30% conversion without gelation because of autoacceleration. The polymer had a viscosity‐average molecular weight of 200,000. The kinetic expression was Rpα[I]0.3[M]1.16, that is, the system followed nonideal kinetics because of primary radical termination and degradative chain‐transfer reactions. The values of kkt and the energy of activation were computed as 3.12 × 10?5 Lmol?1s?1 and 28 kJ/mol, respectively. The ylide dissociated to form a phenyl radical, which brought about polymerization of methyl acrylate. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2060–2065, 2004 相似文献