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991.
An ion-pair liquid chromatographic assay was developed and validated for the determination of ceftriaxone in cerebrospinal fluid. Chromatographic separation was achieved on a C18 column (125 x 4 mm, 5 microm) with detection at 270 nm, a 1 mL/min flow rate and a 50 microL loop. The mobile phase consisted of 300 mL acetonitrile, 50 mL 0.1M phosphate buffer (pH 7.4), 3.2 g tetrabutylammonium bromide as the ion-pairing agent, and dilution with distilled deionized water to 1 L. Cephradine was used as the internal standard. The assay was linear for ceftriaxone concentrations of 0.5-50 microg/mL. The coefficients of variation for precision were <4.61%. The accuracy ranged from 96.07 to 102.42%. The detection and quantitation limits were 0.019 and 0.065 microg/mL, respectively. This method was used to quantify ceftriaxone in the cerebrospinal fluid of children with meningitis. The results showed that the method described here is useful for the determination of ceftriaxone in cerebrospinal fluid. 相似文献
992.
Ricardo Riguera 《Tetrahedron》1978,34(13):2039-2043
A number of hydroxybicyclo[2.2.2]octane carboxylic acids and the corresponding delta lactones have been prepared, and the 13C NMR spectra show trends that, together with some deuteration experiments, provide a self consistent and unambiguous assignment of the resonance peaks. The effects produced by the substituents and the changes in chemical shifts brought about by the lactonization process are analysed. 相似文献
993.
Ricardo N. Garavaglia Rubén E. Rodríguez D. A. Batistoni 《Fresenius' Journal of Analytical Chemistry》1998,360(6):683-688
An evaluation of butanol-1 as dilution solvent for the determination of boron (B) and phosphorus (P) in lubricating oils
by inductively coupled plasma-atomic emission spectrometry (ICP-AES) has been performed. Standard solutions of boric acid
and tri-n-butyl phosphate (TBP) in butanol were employed as calibrants for B and P, respectively. Solutions of phosphoric
acid and tris(2-ethylhexyl)phosphate (TEHP) in butanol were also tested as possible P standards. Increased concentrations
of oil in the sample in the range of 0 to 20% showed no significant effects on B and P emission intensities indicating that
matrix matching is not required for lubricating oils of about 2–15 cPoise. Detection limits in absence of spectral interferences
were 0.06 μg B/g oil and 2 μg P/g oil. Overall estimated precision was 2.5% for B concentrations above 4 μg/g oil, and 6.5%
for P concentrations above 20 μg/g oil. We evaluated the performance of a high resolution scanning spectrometer for mitigating
the effects of overlapping spectral interferences from iron (Fe) and copper (Cu) on B and P emission lines. An interference
from Fe 249.782 nm on the primary B line at 249.773 nm is observed for Fe concentrations higher than 100 μg/g oil, but a secondary
B line at 249.678 nm is completely resolved from Fe 249.653 nm. In the case of P 213.618 nm, a contribution of the right wing
of a Cu line at 213.598 nm generates a signal equivalent to P 18 μg/g oil for Cu 1000 μg/g oil.
Received: 25 June 1997 / Revised: 16 September 1997 / Accepted: 7 October 1997 相似文献
994.
Ricardo Baumhardt-Neto Srgio Emanuel Galembeck Ins Joekes Fernando Galembeck 《Journal of polymer science. Part A, Polymer chemistry》1981,19(3):819-829
Polytetrafluoroethylene (PTFE) surfaces can be modified by impregnation with Fe and Mn oxides by procedures based on Fe(CO)5 sorption in the polymer and followed by oxidation with H2O2 or KMnO4. The effect of some variables (reagent concentrations and temperature) on the amount of oxides deposited was examined. The oxides incorporated in PTFE can be only partly removed by acid cleaning. Water–PTFE contact angles and PTFE surface resistivity are altered. Electron and x-ray diffractograms of the oxides were obtained but unambiguous identification was not achieved. Transmission electron microscopy examination of surface replicas showed that impregnation with oxides which covered most of the PTFE surface was fairly uniform. 相似文献
995.
We introduce a new method to estimate the importance of hydrogen-bonding sitepoints in the binding site of a protein as part of a structure-based design strategy. Our method identifies hydrogen-bonding sitepoints within a binding pocket and ranks them according to both the accessibility of their hydrogen bonding regions to incoming ligands and their hydrogen-bonding strength. The combination of these components produces a prioritised list of sitepoints that are more likely to be involved in hydrogen bonding with an incoming ligand. A dataset of known protein-ligand interactions was used to compare the prioritisation of sitepoints identified by our method with those observed to be engaged in hydrogen bonding in their crystal structures. Our method was able to remove those sitepoints unable to bind the ligand due to a low accessibility or an unfavourable orientation and to award significantly higher hydrogen-bonding ranking values to those sitepoints observed to form hydrogen bonds. Our method can thus be used to identify hydrogen-bonding sitepoints that should be targeted preferentially in a drug design strategy. 相似文献
996.
Dos Santos DS Goulet PJ Pieczonka NP Oliveira ON Aroca RF 《Langmuir : the ACS journal of surfaces and colloids》2004,20(23):10273-10277
In this work, self-sustained, biocompatible, biodegradable films containing gold nanostructures have been fabricated for potential application in nanobioscience and ultrasensitive chemical and biochemical analysis. We report a novel synthesis of gold nanoparticles mediated by the biopolymer chitosan. Self-supporting thin films are formed from the resultant gold-chitosan nanocomposite solutions and characterized by UV-visible surface plasmon absorption, transmission electron microscopy, atomic force microscopy, infrared absorption, and Raman scattering measurements. Results demonstrate control over the size and distribution of the nanoparticles produced, which is promising for several applications, including the development of biosensors. As a proof of principle, we demonstrate that gold-chitosan films can be employed in trace analysis using surface-enhanced Raman scattering. 相似文献
997.
Summary The electron propagator theory is presented with somewhat of a historical perspective and the working equations are developed with the aim of taking advantage of molecular point group symmetry. A new electron propagator code, the vectorized electron propagator program (VEP), is introduced without full details about its structure and capabilities (such details are being published elsewhere). Applications to the (UV) photoelectron spectra of some donor-acceptor complexes of borane with carbon monoxide and water are presented at the level of second-order theory as an illustration of the theory and the VEP code. 相似文献
998.
Wolfgang A. Herrmann Ricardo Serrano Josef Weichmann 《Journal of organometallic chemistry》1983,246(2):c57-c60
Photolysis of the manganese half-sandwich complex (η5-C5Me5)Mn(CO)3 (1) in tetrahydrofuran (THF) yields cleanly the solvent complex (η5-C5Me5)(Mn(CO)2THF (2). Compound 2 undergoes spontaneous elimination of carbon monoxide to give at ambient temperature in approx. 20 h, or upon removal of solvent in vacuo, the novel dinuclear derivative (η5-C5Me5)2Mn2(μ-CO)3 (3). Elemental analyses and infrared and mass as wel as the 1H and 13C NMR spectra unequivocally demonstrate this compound to adopt a triply carbonyl-bridged structure containing the first example of a manganesemanganese multiple bond. 相似文献
999.
Ricardo Q. Aucélio Roseli Martins de SouzaReinaldo Calixto de Campos Norbert MiekeleyCarmem L. Porto da Silveira 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007
The determination of trace metals in lubricating oils using atomic spectrometric methods is reviewed. The importance of such analyses for technical diagnostics as well as the specific sample characteristics related to the analyte form (metallo-organic and metal particles) is discussed. Problems related to sample pre-treatment for appropriate sample introduction and calibration are addressed as well as the strategies to overcome them. Recent trends aimed at simplifying sample manipulation are presented. The applications and scope of AAS, ICP OES and ICP MS techniques for the determination of trace metals in lubricating oil is individually discussed, as well as some present instrumental trends. 相似文献
1000.
With a view to the development of new composite electrodes for lithium-ion batteries with electroactive tin and cobalt, Co-doped tin dioxide samples are studied. The role played by oxygen and cobalt atoms in the electrochemical behavior of tin-based electrodes for Li-ion batteries is examined by the powerful and selective (119)Sn M?ssbauer spectroscopy. For the discharged electrodes, the oxygen atoms in the lithia matrix tend to destabilize the Sn(0) atoms. In contrast, the presence of cobalt atoms helps to form a matrix that stabilizes the reduced tin atoms. Cobalt-tin interactions in electrochemical reduced Co(x)Sn(1-x)O(2) electrodes are deduced from the electrochemical and M?ssbauer results. 相似文献