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101.
Sergio Scognamillo Valeria Alzari Daniele Nuvoli Alberto Mariani 《Journal of polymer science. Part A, Polymer chemistry》2010,48(11):2486-2490
Frontal polymerization was used as an alternative technique for the preparation of super water absorbent hydrogels obtained from acrylamide and 3‐sulfopropyl acrylate, potassium salt (SPAK) in the presence of N,N′‐methylene‐bisacrylamide as a crosslinker. All samples were synthesized in dimethyl sulfoxide, and their swelling behavior in water was investigated. It was found that their features are dependent on the monomer ratio used, which influenced the porous morphology, and consequently, the swelling capability. The swelling ratio ranges from about 1000% for the acrylamide homopolymer up to 14,000% for the sample containing 87.5 mol % of SPAK, thus indicating that this parameter can be easily tuned by using the appropriate monomer ratio. The affinity towards water was eventually confirmed by contact angle analysis. Polymer hydrogels made from at least 62.5 mol % SPAK exhibit a thermoresponsive behavior, with a lower critical solution temperature of ~30 °C. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2486–2490, 2010 相似文献
102.
We have studied the structure and shear flow behaviour of a side chain liquid crystal polymer, namely P12, in the smectic (SmAd) phase. Simultaneous oscillatory shear and small angle X-ray scattering experiments showed that, as expected, the shearing of P12 at high frequency and large strain amplitudes leads to the alignment of the smectic layer normals parallel to the neutral direction. It was also found that, on erasing the memory of the prior shear alignment through melting, P12 can unexpectedly orient with the smectic layers perpendicular to the shear flow direction (b-configuration). We speculate that the b-configuration is adopted due to a counter-balance between the rather long spacer in P12 which decouples mesogens from the backbone, and the oscillatory character of the shear applied to P12. 相似文献
103.
Silvia Bonettini Emanuele Galligani Valeria Ruggiero 《Computational Optimization and Applications》2007,37(1):1-34
This paper deals with the solution of nonlinear programming problems arising from elliptic control problems by an interior
point scheme. At each step of the scheme, we have to solve a large scale symmetric and indefinite system; inner iterative
solvers, with an adaptive stopping rule, can be used in order to avoid unnecessary inner iterations, especially when the current
outer iterate is far from the solution.
In this work, we analyse the method of multipliers and the preconditioned conjugate gradient method as inner solvers for interior
point schemes. We discuss the convergence of the whole approach, the implementation details and report the results of numerical
experimentation on a set of large scale test problems arising from the discretization of elliptic control problems. A comparison
with other interior point codes is also reported.
This research was supported by the Italian Ministry for Education, University and Research (MIUR) projects: FIRB Project:
“Parallel Nonlinear Numerical Optimization PN
2
O” (grant n. RBAU01JYPN, ) and COFIN/PRIN04 Project “Numerical Methods and Mathematical Software for Applications” (grant n. 2004012559, ). 相似文献
104.
Silvia Bonettini Valeria Ruggiero Federica Tinti 《Numerical Linear Algebra with Applications》2007,14(10):807-831
This work is concerned with the convergence properties and the numerical analysis of the preconditioned conjugate gradient (PCG) method applied to the solution of indefinite linear systems arising in nonlinear optimization. Our approach is based on the choice of quasidefinite preconditioners and of a suitable factorization routine. Some theoretical and numerical results about these preconditioners are obtained. Furthermore, we show the behaviour of the PCG method for different formulations of the indefinite system and we compare the effectiveness of the proposed variants. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
105.
The effect of the angular momentum density of a gravitational source on the times of flight of light rays in an interferometer is analyzed. The calculation is made imagining that the interferometer is at the equator of an axisymmetric steadily rotating gravity source. In order to evaluate the size of the effect in the case of the Earth a weak field approximation for the metric elements is introduced. For laboratory scales and non-geodesic paths the correction due to the angular momentum turns out to be comparable with the sensitivity expected in gravitational waves interferometric detectors, whereas it drops under the threshold of detectability when using free (geodesic) light rays. 相似文献
106.
In‐line coupled single drop liquid–liquid–liquid microextraction with capillary electrophoresis for determining fluoroquinolones in water samples 下载免费PDF全文
A simple in‐line single drop liquid–liquid–liquid microextraction (SD‐LLLME) coupled with CE for the determination of two fluoroquinolones was developed. The method is capable to quantify trace amount of analytes in water samples and to improve the sensitivity of CE detection. For the SD‐LLLME, a thin layer of organic phase was used to separate a drop of 0.1 M NaOH hanging at the inlet of the capillary from the aqueous donor phase. By this way, the analytes were extracted to the acceptor phase through the organic layer based on their acidic/basic dissociation equilibrium. The drop was immersed into the organic phase during 10 min for extraction and then it is directly injected into the capillary for the analysis. Parameters such as type and volume of organic solvent phase, aqueous donor, and acceptor phases and extraction time and temperature were optimized. The enrichment factor was calculated, resulting 40‐fold for enrofloxacin (ENR) and sixfold for ciprofloxacin (CIP). The linear range were 20–400 μg/L for ENR and 60–400 μg/L for CIP. The detection limits were 10.1 μg/L and 55.3 μg/L for ENR and CIP, respectively, and a good reproducibility was obtained (4.4% for ENR and 5.6% for CIP). Two real water samples were analysed applying the new method and the obtained results presented satisfactory recovery percentages (90–100.3%). 相似文献
107.
The aqueous solution behavior of polyethyleneimine (a synthetic cationic polymer) in the presence of anions with two or more electrical charges (citrate, phosphate, sulphate, malate, malonate and succinate) was studied by means of turbidimetry and light scattering. Polyethyleneimine forms non-soluble complexes with these anions, which behave as a pseudo-polyampholyte with an isoelectrical pH value dependent on the type of anion. The effect of pH, polymer concentration and ionic strength on the non-soluble complexes formation was examined. The complex precipitation pH range was between 3.5 and 8.0 and also depended on the type of anion. The complex formation was inhibited by the ionic strength in agreement with the electrostatic mechanism of the non-soluble complex formation. Model proteins with isoelectric pH from 1 to 10 were assayed in orden to be precipitated by these complexes. It was found that the non-soluble polyethyleneimine-anion complexes have the property to precipitate macromolecules charged with an opposite electrical charge. 相似文献
108.
Valeria Tagliazucca Emanuela Callone Sandra Dirè 《Journal of Sol-Gel Science and Technology》2011,60(3):236-245
The esterification reaction between carboxylic acids and alcohols has been used as the source of water for the hydrolysis-condensation
reactions of difunctional and trifunctional organosilanes. Diphenylsilanediol (DPDO) has been reacted with methacryloxypropyltrimethoxysilane
(MPTMS) and glycidoxypropyltrimethoxysilane (GPTMS) and the obtained products have been characterized by vibrational spectroscopy
(FT-IR, FT-Raman) nuclear magnetic resonance (NMR) and gel permeation chromatography. The relation between water availability
from the in situ water production process (ISWP) and silsesquioxanes morphology has been evaluated in the case of DPDO/MPTMS
mixtures, changing molecular features of acids and alcohols. These measurements have shown that the pK of the carboxylic acid
used in the esterification reaction has a valuable influence on the silanes cross-linking ability. Acids with low pK values
and heteroatoms substituents favor the silane hydrolysis and allow the growth of high molecular weight species. Using acetic
acid/ethanol mixture leads to the best results for DPDO/MPTMS reaction, with a narrow distribution of silsesquioxane species.
Under the same conditions, the reaction of DPDO with GPTMS produces polymeric species and only avoiding the presence of the
difunctional precursor allows to limiting the silsesquioxanes species growth. 相似文献
109.
Narcisi V Mascini M Perez G Del Carlo M Tiscar PG Yamanaka H Compagnone D 《Talanta》2011,85(4):1927-1932
A post-PCR nucleic acid work by comparing experimental data, from electrochemical genosensors, and bioinformatics data, derived from the simulation of the secondary structure folding and prediction of hybridisation reaction, was carried out in order to rationalize the selection of ssDNA probes for the detection of two Bonamia species, B. exitiosa and B. ostreae, parasites of Ostrea edulis.Six ssDNA probes (from 11 to 25 bases in length, 2 thiolated and 4 biotinylated) were selected within different regions of B. ostreae and B. exitiosa PCR amplicons (300 and 304 bases, respectively) with the aim to discriminate between these parasite species. ssDNA amplicons and probes were analyzed separately using the “Mfold Web Server” simulating the secondary structure folding behaviour. The hybridisation of amplicon-probe was predicted by means of “Dinamelt Web Server”. The results were evaluated considering the number of hydrogen bonds broken and formed in the simulated folding and hybridisation process, variance in gaps for each sequence and number of available bases. In the experimental part, thermally denatured PCR products were captured at the sensor interface via sandwich hybridisation with surface-tethered probes (thiolated probes) and biotinylated signalling probes. A convergence between analytical signals and simulated results was observed, indicating the possibility to use bioinformatic data for ssDNA probes selection to be incorporated in genosensors. 相似文献
110.
Amendola V Fabbrizzi L Mosca L Schmidtchen FP 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(21):5972-5981
In this work, we compare the anion-binding capabilities of receptors 1-5, characterized by similar structures, but possessing different hydrogen-bond-donor moieties (urea, squaramide, and sulfonamide). The presence of chromophoric substituents on the receptor's skeleton allowed the determination of association constants by performing UV/Vis titrations with the investigated anions on solutions of the receptors in pure acetonitrile. Additional quantitative studies of the anion-binding properties of receptors 1-5 were performed by isothermal titration calorimetry (ITC). The experimental results indicated that 1 and 2 formed 1:1 hydrogen-bonded complexes with most of the anions investigated. In the case of receptors 3-5, the formation of the 1:1 adduct was observed only with anions of low basicity (i.e., chloride, bromide, iodide, and hydrogen sulfate). With more basic anions (i.e., acetate and dihydrogen phosphate), both spectrophotometric and ITC titrations accounted for the deprotonation of the sulfonamide group, involving the formation of the conjugated base of the receptor. 相似文献