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941.
《Journal of Coordination Chemistry》2012,65(11):943-951
Cu(II), Ni(II) and Zn(II) complexes with the Schiff base derived from 1,2-bis-(o-aminophenoxy)ethane with salicylaldehyde have been prepared. The complexes have been characterized by elemental analysis, magnetic measurements, 1H NMR, 13C NMR, UV, visible and IR spectra as well as conductance measurements. The ligand is coordinated to the central metal as a tetradentate ONNO ligand. The four bonding sites are the central azomethine nitrogen and aldehydic OH groups. The ligand was used for complexation studies. Stability constants were measured by a conductometric method. Furthermore, the stability constants for complexation between ZnCl2 and Cu(NO3)2 salts and N,N′-bis(salicylidene)-1,2-bis-(o-aminophenoxy)ethane (H2L) in 80% dioxane/water and pure methanol were determined from conductance measurements. The magnitudes of these ion association constants are related to the nature of the solvation of the cation and the complexed cation. The mobilities of the complexes are also dependent, in part, upon solvation effects. 相似文献
942.
943.
Frustrated delivery: Frustrated Lewis pairs derived from tBu(3) P and Al(C(6) F(5) )(3) activate H(2) to give [tBu(3) PH][(μ-H)(Al(C(6) F(5) )(3) )(2) ], which reacts with unactivated olefins to give RAl(C(6) F(5) )(2) (R=Et or Cy) and [tBu(3) PH][Al(C(6) F(5) )(4) ]. The proposed mechanism involves olefin activation by aluminum, which is supported by the isolation of the cyclohexene complex [Al(C(6) F(5) )(3) ?(C(6) H(10) )]. 相似文献
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945.
946.
947.
This paper is devoted to constructing some recollements of additive categories associated to concentric twin cotorsion pairs on an extriangulated category. As an application, this result generalizes the work by W. J. Chen, Z. K. Liu, and X. Y. Yang in a triangulated case [J. Algebra Appl., 2018, 17(5): 1–15]. Moreover, it highlights new phenomena when it applied to an exact category. Finally, we give some applications of our main results. In particular, we obtain Krause's recollement whose proofs are both elementary and very general. 相似文献
948.
Two simple and sensitive high performance liquid chromatographic (HPLC) methods have been developed for the simultaneous determination of three different quinolones: enrofloxacin, lomefloxacin and ofloxacin in their pure and dosage forms, one with reversed phase HPLC and the other with ion-pair HPLC. In reversed phase HPLC, method (A), the mobile phase consists of 2.18% aqueous solution of KH2PO4 with pH adjusted to 2.4 ± 0.2 with acetonitrile (80:20; v/v), the mobile phase pumped at flow rate of 1.2 ml min?1. A Neucleosil C18 column (10 μm, 100 Å), 250 mm length × 4.6 mm diameter was utilized as stationary phase. Detection was affected spectrophotometrically at 294 nm. While in ion-pair HPLC, method (B), the mobile phase was aqueous solution of 0.65% sodium perchlorate and 0.31% ammonium acetate adjusted to pH 2.2 ± 0.2 with orthophosphoric acid: acetonitrile (81:19; v/v), the mobile phase pumped at flow rate of 1.5 ml min?1. A μ bondapack C18 column (10 μm, 100 Å), 250 mm length × 4.6 mm diameter was utilized as stationary phase. Detection was affected spectrophotometrically at 294 nm. Linearity ranges for enrofloxacin, lomefloxacin and ofloxacin were 4.0–108, 7.0–112 and 8.0–113 μg ml?1, respectively using method A and 8.0–112, 7.0–112 and 5.0–105 μg ml?1, respectively applying method B. Minimum detection limits obtained were 0.013, 0.023 and 0.035 μg ml?1 for enrofloxacin, lomefloxacin and ofloxacin, respectively using method A, and 0.028, 0.023 and 0.011 μg ml?1 using method B. The proposed methods were further applied to the analysis of enrofloxacin in injection and tablets containing the ofloxacin and lomefloxacin drugs, and the results were satisfied. 相似文献
949.
Quirino JP 《Journal of separation science》2011,34(9):1020-1026
Online sample concentration of acidic drugs by transient isotachophoresis (t-ITP) with the injection of a base is described in capillary zone electrophoresis (CZE). A positively coated capillary was conditioned with background electrolyte (ammonium acetate at pH 6). A long plug of sample solution (S) prepared in ammonium acetate was then hydrodynamically injected followed by the base (tetrapropylammonium hydroxide). A negative voltage was applied and caused the hydroxide ions from the base to penetrate the S zone and created a pH junction that swept through the S zone. The analytes stack at the junction where the mechanism of focusing was transient ITP with the acetate and hydroxide ions as leading and terminating ions, respectively. The concentrated analytes separated in co-EOF CZE once the hydroxide was exhausted. The base stacking strategy was tested using hypolipidemic, nonsteroidal anti-inflammatory, and diuretic drugs, and afforded 19-37 improvements in peak height. 相似文献
950.