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101.
Gomes P Wingert NR Paim CS Schapoval EE Steppe M 《Journal of AOAC International》2010,93(6):1829-1835
A stability-indicating HPLC assay method was developed for the quantitative determination of duloxetine (DLX) in a pharmaceutical dosage form in the presence of its degradation products, and kinetic determinations were evaluated in acid conditions and UV-C radiation exposure. Chromatographic separation was achieved by use of an ACE C18 column (250 x 4.0 mm id, 5 microm particle size). The mobile phase was prepared by mixing aqueous 50 mM potassium phosphate buffer (pH 6.0 containing 0.3% triethylamine) and acetonitrile (60 + 40, v/v). DLX was rapidly degraded in an acid medium and in the presence of hydrogen peroxide and UV-C radiation; it was more stable in alkaline medium. The described method was linear over a range of 4.0-14.0 microg/mL for determination of DLX (r = 0.9998). The precision was demonstrated by the RSD of intraday (0.79-1.07%) and interday (0.85%) studies. The mean recovery was found to be 100.56%. The acid degradation of DLX in 0.1 M HCI solution showed an apparent zero-order kinetics (k = 0.177 microg/mL/min), and the photodegradation demonstrated an apparent first-order kinetics (k = 0.082 microg/mL/min). The developed method was found to be simple, specific, robust, linear, precise, and accurate for the determination of DLX in enteric-coated pellets. 相似文献
102.
We present a method for ultra-low-loss coupling between two single-mode optical fibers with different mode-field diameters using multimode interference in a graded-index multimode optical fiber. We perform a detailed analysis of the interference effects and show that the graded-index fiber can also be used as a beam expander or condenser. The results are important for devices in which optical fibers with different mode-field diameters are coupled in series, such as in ultra-short-pulse fiber ring lasers, or in optical fiber communication links. 相似文献
103.
Clément Dubuisson 《Integral Equations and Operator Theory》2014,78(2):249-269
We prove a Lieb–Thirring type inequality for a complex perturbation of a d-dimensional massive Dirac operator ${D_m, m\geq 0, d \geq 1}$ whose spectrum is ${]-\infty,-m]\cup[m,+\infty[}$ . The difficulty of the study is that the unperturbed operator is not bounded from below in this case, and, to overcome it, we use the methods of complex function theory. The methods of the article also give similar results for complex perturbations of the Klein–Gordon operator. 相似文献
104.
105.
Denize C. Favaro Rubén H. Contreras Cláudio F. Tormena 《Magnetic resonance in chemistry : MRC》2013,51(6):334-338
SOPPA(CCSD) calculations show that the FC term is the most important contribution to the through‐space transmission of JFN coupling constants for the fluoroximes studied in this work. Because of the well‐known behavior of FC term, a new rationalization for the experimental TSJFN SSCC is presented. It is mainly based on the overlap matrix (Sij) between fluorine and nitrogen lone pairs obtained from NBO analyses. An expression is proposed to take into account the influence of the electronic density (Dij) between coupled nuclei as well as the s% character at the site of the coupling nuclei of bonds and non‐bonding electron pairs involved in Dij. In using this approach, a linear correlation between TSJFN versus Dij is obtained. The most important aspect of this rationalization is related to the facility for understanding the behavior of some unusual experimental coupling constants. It is shown that, at least in this case, the electronic origin of the so‐called through‐space coupling is transmitted through to the overlap of orbitals on the coupled atoms, suggesting that, at least for these compounds, instead of through‐space coupling, it should better be dubbed as ‘through overlapping orbital coupling’. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
106.
107.
108.
Cláudia Simões Vanda Simões Ana Reis Pedro Domingues M. Rosário M. Domingues 《Analytical and bioanalytical chemistry》2010,397(6):2417-2427
Phosphatidylethanolamine glycation occurs in diabetic patients and was found to be related with oxidative stress and with
diabetic complications. Glycated phosphatidylethanolamines seem to increase oxidation of other molecules; however, the reason
why is not understood. In this work, we have studied the oxidation of glycated phosphatidylethanolamines (1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphatidylethanolamine (PLPE) and 1,2-dipalmitoyl-sn-glycero-3-phosphatidylethanolamine (dPPE)) using a Fenton system. Liquid chromatography–electrospray ionization (ESI)–mass
spectrometry and ESI–tandem mass spectrometry in both positive and negative modes were used for detecting and identifying
the oxidation products. We were able to identify several oxidation products with oxidation in unsaturated sn-2 acyl chain of PLPE, as long- and short-chain products with main oxidation sites on C-7, C-8, C-9, and C-12 carbons. Other
products were identified in both glycated PLPE and glycated dPPE, revealing that oxidation also occurs in the glycated polar
head. This fact has not been reported before. These products may be generated from oxidation of glycated phosphatidylethanolamines
(PE) as Schiff base, leading to short-chain product without the amine moiety, due to cleavage of glycated polar head and long-chain
product with two keto groups linked to the glycated polar head or from glycated PE as Amadori product, short-chain products
with –NHCHO and –NHCHOHCHO terminal in polar head. Oxidation of glycated phosphatidylethanolamines occurred more quickly than
the oxidation of non-glycated phosphatidylethanolamines probably because of the existence of more oxidation sites derived
from glycation of polar head group. Monitoring glycated polar head oxidation could be important to evaluate oxidative stress
modifications that occur in diabetic patients. 相似文献
109.
Sonia de Almeida Evaneide N. Lima Marisa S. Crespi Clóvis A. Ribeiro Valdir Schalch 《Journal of Thermal Analysis and Calorimetry》2009,97(2):529-533
Urban solid residues are constituted of food remaining, grass leaves, fruit peelings, paper, cardboard, rubber, plastic, etc.
The organic fraction formed represents about 50% during the decomposition yields biogas and leachate, which are sources of
pollution. Residue samples were collected from the landfill in different and cells from several ages and the corresponding
leachate, both after treatments, were submitted to thermal analysis. Kinetic parameters were determined using Flynn–Wall–Ozawa
method. The linear relation between the two kinetic parameters (ln A and E) was verified for organic residue urban’s samples, but not for leachate’s sample. The occurred difference can be attributed
to the constituents present in leachate. 相似文献
110.