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81.
A newly-developed energy-based model for cavitation in rubber particles provides a quantitative basis for understanding the factors controlling toughness in rubber-modified plastics. Cavitation of the rubber is the initial step in the toughening mechanism, and is shown to accelerate yielding of the matrix, either by the formation of dilatation bands or by multiple crazing. Cavitation is thus a strain-softening effect. However, in some cases the cavitated rubber forms fibrils which become highly stretched as local strains increase, and thus begin to carry a significant fraction of the applied stress. The resulting strain-hardening ensures that yielding is not limited to a small deformation zone at a crack tip, but spreads outwards. 相似文献
82.
Thaís Silva da Rocha Alessandro de Lima Jurandy do Nascimento Silva Geni Rodrigues Sampaio Rosana Aparecida Manlio Soares Freitas Renan Danielski Adriano Costa de Camargo Fereidoon Shahidi Elizabeth Aparecida Ferraz da Silva Torres 《Molecules (Basel, Switzerland)》2022,27(3)
Jua (juá in Portuguese) is an underexplored fruit from Brazil’s northeast. This fruit is rich in antioxidant substances. However, there is a dearth of information about jua’s bioactive potential. The present study evaluated two extraction methods (continuous agitation and ultrasound-assisted extraction—UAE) and employed three different solvents (water, ethanol, and acetone) to efficiently recover soluble phenolic compounds. Aqueous extracts obtained by UAE showed the highest total phenolic content (TPC) and antiradical activity. Besides being an eco-friendly procedure, extraction and/or solubility in an aqueous medium is also important for food application. Ellagic acids were the predominant phenolics (80%) found in aqueous jua pulp extract obtained by UAE, as determined by HPLC, while its TPC was 405.8 gallic acid equivalent per gram of fruit. This extract also exhibited a higher scavenging activity towards peroxyl radicals when compared to that of several other fruits from the literature, including grape, strawberry, cranberry, and walnuts, which are known references in terms of antioxidants. This is the first report that demonstrates jua pulp’s potential as an alternative source of ellagic acid and other phenolic acids and flavonoids. Therefore, the outcome of this study provides new information that can be useful for functional food and nutraceutical industries. 相似文献
83.
A generic mathematical model for analyzing the effect of ideal and non-ideal reactor residence time distributions on the size distribution of polymer particles produced with heterogeneous Ziegler-Natta and supported metallocene catalysts was developed. It was shown that the residence time distribution in polymerization reactors can have a significant effect on the size distribution of polymer particles and this can lead to imperfect replication of the catalyst particle size distribution. 相似文献
84.
María Fernanda Manrique-de-la-Cuba Luis Leyva-Parra Diego Inostroza Prof. Badhin Gomez Dr. Alejandro Vásquez-Espinal Prof. Jorge Garza Dr. Osvaldo Yañez Prof. William Tiznado 《Chemphyschem》2021,22(10):906-910
We report the global minima structures of Li8Si8, Li10Si9, and Li12Si10 systems, in which silicon moieties maintain structural and chemical bonding characteristics similar to those of their building blocks: the aromatic clusters Td−Li4Si4 and C2v−Li6Si5. Electron counting rules, chemical bonding analysis, and magnetic response properties verify the silicon unit‘s aromaticity persistence. This study demonstrates the feasibility of assembling silicon-based nanostructures from aromatics clusters as building blocks. 相似文献
85.
In this study, a suitable method is reported to produce reinforced antibacterial paper packaging using the antimicrobial triclosan (TC) and organically modified montmorillonite (OMMT) as “model” compounds. Direct incorporation of TC at a concentration of 1 wt% and OMMT at concentrations of 1, 4, 7, and 10 wt% into papers was performed via coating process, and the resulting materials were characterized by in vitro antimicrobial assays, thermogravimetric analysis, scanning electron microscopy, mechanical tests, and water vapor transmission rate determinations. It was demonstrated that the presence of 1% TC in the coated papers exhibited inhibitory effects against Staphylococcus aureus and Escherichia coli. It was also pointed out that increases of approximately 30% in the tensile strength of commercial paper are obtained by using the OMMT at a concentration of 1 wt%. Water barrier property and thermal stability of paper were also enhanced because of the coating process and the incorporation of OMMT. The results from this study demonstrate that OMMT has a great potential to be incorporated into coating formulations to obtain antibacterial‐coated papers with improved properties for various packaging applications. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
86.
Pereira CF Pimentel MF Galvão RK Honorato FA Stragevitch L Martins MN 《Analytica chimica acta》2008,611(1):41-47
This work presents a comparative study of calibration transfer among three near infrared spectrometers for determination of naphthenes and RON (Research Octane Number) in gasoline. Seven transfer methods are compared: direct standardization (DS), piecewise direct standardization (PDS), orthogonal signal correction (OSC), reverse standardization (RS), piecewise reverse standardization (PRS), slope and bias correction (SBC) and model updating (MU). Two pre-treatment procedures, namely standard normal variate (SNV) and multiplicative scatter correction (MSC), are also investigated. The choice of an appropriate number of transfer samples for each technique, as well as the effect of window size in PDS/PRS and OSC components, are discussed. A broad set of gasoline samples representative of the Northeastern states of Brazil is employed in the investigation. The results show that the use of calibration transfer yields prediction errors comparable to those obtained with complete recalibration of the secondary instrument. Overall, the results point to RS as the best method for the analytical problem under consideration. When storage and/or physical transportation of transfer samples are impractical, MU is more appropriate. The comprehensive investigation carried out in the present work will be of value for practitioners involved in networks of fuel monitoring. 相似文献
87.
Marie‐Claire Giel Christopher J. Smedley Emily R. R. Mackie Taijie Guo Jiajia Dong Tatiana P. Soares da Costa John E. Moses 《Angewandte Chemie (International ed. in English)》2020,59(3):1181-1186
The boom in growth of 1,4‐disubstituted triazole products, in particular, since the early 2000’s, can be largely attributed to the birth of click chemistry and the discovery of the CuI‐catalyzed azide–alkyne cycloaddition (CuAAC). Yet the synthesis of relatively simple, albeit important, 1‐substituted‐1,2,3‐triazoles has been surprisingly more challenging. Reported here is a straightforward and scalable click‐inspired protocol for the synthesis of 1‐substituted‐1,2,3‐triazoles from organic azides and the bench stable acetylene surrogate ethenesulfonyl fluoride (ESF). The new transformation tolerates a wide selection of substrates and proceeds smoothly under metal‐free conditions to give the products in excellent yield. Under controlled acidic conditions, the 1‐substituted‐1,2,3‐triazole products undergo a Michael addition reaction with a second equivalent of ESF to give the unprecedented 1‐substituted triazolium sulfonyl fluoride salts. 相似文献
88.
M. Peres A. Cruz S. Pereira M.R. Correia M.J. Soares A. Neves M.C. Carmo T. Monteiro A.S. Pereira M.A. Martins T. Trindade E. Alves S.S. Nobre R.A. Sá Ferreira 《Applied Physics A: Materials Science & Processing》2007,88(1):129-133
Synthetic ZnO nanocrystals have been intentionally doped with Eu3+ ions. Structural analysis performed on the nanocrystals showed wurtzite-ZnO as the only phase present in the samples. Photoluminescence
in emission and excitation modes allows the assignment of the intra-4f6 transitions for the Eu3+ ions. From the analysis of the optical data we are able to demonstrate that multiple Eu-related optical centres are present
in the studied samples. Oxygen vacancies are likely candidates to be responsible for the ion accommodation in the ZnO lattice
and from the photoluminescence excitation data we tentatively assign a trap level at ∼200 meV below the conduction band to
this intrinsic defect.
PACS 78.66.Hf; 78.67.-n; 82.80.Yc 相似文献
89.
CaII Binding Regulates and Dominates the Reactivity of a Transition‐Metal‐Ion‐Dependent Diesterase from Mycobacterium tuberculosis 下载免费PDF全文
Dr. Marcelo M. Pedroso Prof. James A. Larrabee Dr. Fernanda Ely Shuhui E. Gwee Dr. Nataša Mitić Prof. David L. Ollis Prof. Lawrence R. Gahan Prof. Gerhard Schenk 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(3):999-1009
The diesterase Rv0805 from Mycobacterium tuberculosis is a dinuclear metallohydrolase that plays an important role in signal transduction by controlling the intracellular levels of cyclic nucleotides. As Rv0805 is essential for mycobacterial growth it is a promising new target for the development of chemotherapeutics to treat tuberculosis. The in vivo metal‐ion composition of Rv0805 is subject to debate. Here, we demonstrate that the active site accommodates two divalent transition metal ions with binding affinities ranging from approximately 50 nm for MnII to about 600 nm for ZnII. In contrast, the enzyme GpdQ from Enterobacter aerogenes, despite having a coordination sphere identical to that of Rv0805, binds only one metal ion in the absence of substrate, thus demonstrating the significance of the outer sphere to modulate metal‐ion binding and enzymatic reactivity. CaII also binds tightly to Rv0805 (Kd≈40 nm ), but kinetic, calorimetric, and spectroscopic data indicate that two CaII ions bind at a site different from the dinuclear transition‐metal‐ion binding site. CaII acts as an activator of the enzymatic activity but is able to promote the hydrolysis of substrates even in the absence of transition‐metal ions, thus providing an effective strategy for the regulation of the enzymatic activity. 相似文献
90.
Francisco J. Prado‐Prado Florencio M. Ubeira Fernanda Borges Humberto González‐Díaz 《Journal of computational chemistry》2010,31(1):164-173
In the previous work, we reported a multitarget Quantitative Structure‐Activity Relationship (mt‐QSAR) model to predict drug activity against different fungal species. This mt‐QSAR allowed us to construct a drug–drug multispecies Complex Network (msCN) to investigate drug–drug similarity (González‐Díaz and Prado‐Prado, J Comput Chem 2008, 29, 656). However, important methodological points remained unclear, such as follows: (1) the accuracy of the methods when applied to other problems; (2) the effect of the distance type used to construct the msCN; (3) how to perform the inverse procedure to study species–species similarity with multidrug resistance CNs (mdrCN); and (4) the implications and necessary steps to perform a substructural Triadic Census Analysis (TCA) of the msCN. To continue the present series with other important problem, we developed here a mt‐QSAR model for more than 700 drugs tested in the literature against different parasites (predicting antiparasitic drugs). The data were processed by Linear Discriminate Analysis (LDA) and the model classifies correctly 93.62% (1160 out of 1239 cases) in training. The model validation was carried out by means of external predicting series; the model classified 573 out of 607, that is, 94.4% of cases. Next, we carried out the first comparative study of the topology of six different drug–drug msCNs based on six different distances such as Euclidean, Chebychev, Manhattan, etc. Furthermore, we compared the selected drug–drug msCN and species–species mdsCN with random networks. We also introduced here the inverse methodology to construct species–species msCN based on a mt‐QSAR model. Last, we reported the first substructural analysis of drug–drug msCN using Triadic Census Analysis (TCA) algorithm. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010 相似文献