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91.
Yu. Yu. Samitov A. A. Musina L. I. Gurarii É. T. Mukmenev B. A. Arbuzov 《Russian Chemical Bulletin》1975,24(7):1407-1413
92.
93.
[reaction: see text] A convenient approach to racemic analogues of N-benzoyl-syn-phenylisoserine was realized via the stereoselective iodocyclization of amides obtained from Baylis-Hillman adducts. 相似文献
94.
Pichini S Pellegrini M Pacifici R Marchei E Murillo J Puig C Vall O García-Algar O 《Rapid communications in mass spectrometry : RCM》2003,17(17):1958-1964
A high-performance liquid chromatography (HPLC) method with mass spectrometric detection is described for determination of arecoline in newborn meconium, urine and cord serum, using pilocarpine as internal standard. The analytes were extracted from neonatal biological matrices with chloroform/isopropanol (95:5, v/v) at alkaline pH. Extracts were analyzed by HPLC coupled to an electrospray (ESI) interface and a quadrupole mass spectrometer. Chromatography was performed on a C(8) reversed-phase column using 10 mM ammonium acetate (pH 4.3)/acetonitrile (90:10, v/v) as mobile phase. The mass spectrometer was operated in selected ion monitoring mode. The method was validated over the concentration range 0.005-1.00 micro g/g meconium, 0.004-1.00 micro g/mL cord serum and 0.001-1.00 micro /mL urine. Mean recoveries ranged between 86.5 and 90.7% for arecoline in the different biological matrices, with precision always better than 10%. The quantification limits of arecoline were 0.005 micro g/g meconium, 0.004 micro g/mL cord serum, and 0.001 micro g/mL urine. The method was applied to the analysis of neonatal biological matrices to assess eventual fetal exposition to arecoline. Two newborns from Asian mothers who declared areca nut consumption presented arecoline in meconium with concentrations in the range 0.006-0.008 micro g/g; also the urine from one neonate tested positive for the drug. 相似文献
95.
96.
Busico V Van Axel Castelli V Aprea P Cipullo R Segre A Talarico G Vacatello M 《Journal of the American Chemical Society》2003,125(18):5451-5460
The 150 MHz (13)C NMR microstructural analysis of polypropylene samples produced with two representative "oscillating" metallocene catalysts of largely different steric hindrance, namely [(2-(3,5-di-tert-butyl-4-methoxyphenyl)indenyl)(2)ZrP](+) and [(2-phenylindenyl)(2)ZrP](+) (P = polymeryl), and the implications on the origin of the stereocontrol are presented and discussed in detail. The original mechanistic proposal of an "oscillation" between a rac-like (isotactic-selective) and a meso-like (nonstereoselective) conformation cannot explain the observed polymer configuration. The isotactic-stereoblock nature of the polymers obtained with the former catalyst proves unambiguously that the active cation "oscillates" between the two enantiomorphous rac-like conformations at an average frequency that, even at high propene concentration, is only slightly lower than that of monomer insertion. The less-hindered [(2-phenylindenyl)(2)ZrP](+) gives instead a largely stereoirregular polypropylene, which is the logical consequence of a faster ligand rotation; however, depending on the use conditions (in particular, on the nature of the cocatalyst and the polarity of the solvent), the polymerization products may also contain appreciable amounts of a fairly isotactic fraction. The peculiar microstructure of this fraction, with isotactic blocks of the same relative configuration spanned by very short atactic ones, rules out the possibility that the latter are due to an active species in meso-like conformation and points rather to a conformationally "locked" rac-like species with restricted ring mobility. The hypothesis of a stereorigidity induced by the proximity to a counteranion, which would play the role of the interannular bridge in the rac-bis(indenyl) ansa-metallocenes, was tested by computer modeling on a [rac-(2-phenylindenyl)(2)ZrMe(C(3)H(6))][B(C(6)F(5))(4)] ion couple and found viable. 相似文献
97.
R. M. Galimullina M. I. Valitov Yu. S. Spiridonova E. I. Musina S. A. Krasnov M. K. Kadirov A. A. Karasik Yu. G. Budnikova O. G. Sinyashin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(12):2214-2221
The efficiency of a series of nickel complexes of P,N-cyclic ligands (potential catalysts in hydrogen fuel cells) in the electrocatalytic
reduction of H+ to hydrogen and the oxidation of H2 in the coordination shell/cavity of the catalyst in DMF (acetonitrile with variable nickel: ligand ratio (1: 1, 1: 2) and
different counterions (X=Cl− and BF4−)) was tested, and the most favorable conditions and structures were determined. The relation between the activity of the
catalysts and the values of the electrochemical gap was found. 相似文献
98.
Roberta Sburlati 《Journal of Elasticity》2009,95(1-2):79-97
In this paper, we propose a method for the solution of the axisymmetric boundary value problem for a finite elastic cylinder with assigned stress and/or displacements acting on the ends and side. The technique utilizes the Love representation, which allows for reduction of the solution of the elastic problem to the search for a biharmonic function on a cylindrical domain. In the solution method suggested here, we write the Love function with a Bessel expansion and analyze in detail the conditions under which it is possible to differentiate the expansion term by term. We show that this is possible only for a restricted class of elastic solutions. In the general case, we introduce two new auxiliary functions of the z-coordinate. In this way, we obtain the general form of the axisymmetric biharmonic function, which is discussed in relation to certain specific boundary conditions applied on the side and ends of the cylinder. We obtain an exact explicit solution of practical interest for a cylinder with free ends and assigned displacements applied to the side. 相似文献
99.
This paper deals with some Sobolev-type inequalities with weights that were proved by Maz’ya in 1980 and by Caffarelli–Kohn–Nirenberg in 1984. 相似文献
100.
Bruna Cláudia Lourenção Roberta Antigo Medeiros Romeu C. Rocha‐Filho Orlando Fatibello‐Filho 《Electroanalysis》2010,22(15):1717-1723
A cathodically pretreated boron‐doped diamond electrode was used for the simultaneous anodic determination of ascorbic acid (AA) and caffeine (CAF) by differential pulse voltammetry. Linear calibration curves (r=0.999) were obtained from 1.9×10?5 to 2.1×10?4 mol L?1 for AA and from 9.7×10?6 to 1.1×10?4 mol L?1 for CAF, with detection limits of 19 μmol L?1 and 7.0 μmol L?1, respectively. This method was successfully applied for the determination of AA and CAF in pharmaceutical formulations, with results equal to those obtained using a HPLC reference method. 相似文献