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791.
Fantauzzi M Licheri C Atzei D Loi G Elsener B Rossi G Rossi A 《Analytical and bioanalytical chemistry》2011,401(7):2237-2248
In this work, a multi-technical bulk and surface analytical approach was used to investigate the bioleaching of a pyrite and
arsenopyrite flotation concentrate with a mixed microflora mainly consisting of Acidithiobacillus ferrooxidans. X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and X-ray-induced Auger electron spectroscopy mineral surfaces
investigations, along with inductively coupled plasma-atomic emission spectroscopy and carbon, hydrogen, nitrogen and sulphur
determination (CHNS) analyses, were carried out prior and after bioleaching. The flotation concentrate was a mixture of pyrite
(FeS2) and arsenopyrite (FeAsS); after bioleaching, 95% of the initial content of pyrite and 85% of arsenopyrite were dissolved.
The chemical state of the main elements (Fe, As and S) at the surface of the bioreactor feed particles and of the residue
after bioleaching was investigated by X-ray photoelectron and X-ray excited Auger electron spectroscopy. After bioleaching,
no signals of iron, arsenic and sulphur originating from pyrite and arsenopyrite were detected, confirming a strong oxidation
and the dissolution of the particles. On the surfaces of the mineral residue particles, elemental sulphur as reaction intermediate
of the leaching process and precipitated secondary phases (Fe–OOH and jarosite), together with adsorbed arsenates, was detected.
Evidence of microbial cells adhesion at mineral surfaces was also produced: carbon and nitrogen were revealed by CHNS, and
nitrogen was also detected on the bioleached surfaces by XPS. This was attributed to the deposition, on the mineral surfaces,
of the remnants of a bio-film consisting of an extra-cellular polymer layer that had favoured the bacterial action. 相似文献
792.
This perspective reports on some of the main copper-catalyzed routes to the construction of the pyrrole and furan rings incorporated into the indole and benzo[b]furan systems, respectively. The first part illustrates the synthesis of indoles through cyclizations of 2-alkynylanilid(n)es, preformed or generated in situ, and cyclizations via intramolecular N-arylation, N-vinylation, and C-C bond forming reactions. The second part illustrates the synthesis of benzo[b]furans through cyclizations of preformed 2-alkynylphenols, domino synthesis of 2-alkynylphenols/cyclization processes, and cyclizations via intramolecular O-arylation reactions. 相似文献
793.
Danilo Addari Adriana Mignani Erika Scavetta Domenica Tonelli Antonella Rossi 《Surface and interface analysis : SIA》2011,43(4):816-822
In this work, a Ni/Al hydrotalcite (HT) was used as glucose oxidase (GOx) immobilizer. Small‐area and angle‐resolved X‐ray photoelectron spectra were recorded on HTs electrosynthesized on Pt in the absence and in the presence of GOx, and compared with those obtained for a Pt surface, modified with the electrosynthesized HT, on which a drop of GOx solution was deposited. The simultaneous electrodeposition of HT + GOx resulted in a compact deposit, thicker than the XPS sampling depth (>10 nm), that is not homogeneous in the lateral and in‐depth composition. The presence of GOx can be deduced comparing the N1s spectra of HT and HT + GOx: in the latter, the N1s component at 400 eV binding energy (BE) is predominant whilst, depending on the analyzed point, a small or no contribution from the component at 407.2 eV, due to nitrate, is revealed. Angle‐resolved XPS provides evidence on the in‐depth composition of anions, cations and GOx. The results highlight the crucial role played by nickel in GOx immobilization. On the basis of the results, it can be suggested that enzyme activity is unevenly distributed and is localized in small areas, where Ni concentration is higher. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
794.
We have carried out quantum mechanical (QM) and QM/MM (combined QM and molecular mechanics) calculations, as well as molecular
dynamics (MD) simulations to study the binding of a series of six RAPTA (Ru(II)-arene-1,3,5-triaza-7-phosphatricyclo-[3.3.1.1]
decane) complexes with different arene substituents to cathepsin B. The recently developed QM/MM-PBSA approach (QM/MM combined
with Poisson–Boltzmann solvent-accessible surface area solvation) has been used to estimate binding affinities. The QM calculations
reproduce the antitumour activities of the complexes with a correlation coefficient (r
2) of 0.35–0.86 after a conformational search. The QM/MM-PBSA method gave a better correlation (r
2 = 0.59) when the protein was fixed to the crystal structure, but more reasonable ligand structures and absolute binding energies
were obtained if the protein was allowed to relax, indicating that the ligands are strained when the protein is kept fixed.
In addition, the best correlation (r
2 = 0.80) was obtained when only the QM energies were used, which suggests that the MM and continuum solvation energies are
not accurate enough to predict the binding of a charged metal complex to a charged protein. Taking into account the protein
flexibility by means of MD simulations slightly improves the correlation (r
2 = 0.91), but the absolute energies are still too large and the results are sensitive to the details in the calculations,
illustrating that it is hard to obtain stable predictions when full flexible protein is included in the calculations. 相似文献
795.
Antiviral properties of lactoferrin--a natural immunity molecule 总被引:1,自引:0,他引:1
Berlutti F Pantanella F Natalizi T Frioni A Paesano R Polimeni A Valenti P 《Molecules (Basel, Switzerland)》2011,16(8):6992-7018
Lactoferrin, a multifunctional iron binding glycoprotein, plays an important role in immune regulation and defence mechanisms against bacteria, fungi and viruses. Lactoferrin's iron withholding ability is related to inhibition of microbial growth as well as to modulation of motility, aggregation and biofilm formation of pathogenic bacteria. Independently of iron binding capability, lactoferrin interacts with microbial, viral and cell surfaces thus inhibiting microbial and viral adhesion and entry into host cells. Lactoferrin can be considered not only a primary defense factor against mucosal infections, but also a polyvalent regulator which interacts in viral infectious processes. Its antiviral activity, demonstrated against both enveloped and naked viruses, lies in the early phase of infection, thus preventing entry of virus in the host cell. This activity is exerted by binding to heparan sulphate glycosaminoglycan cell receptors, or viral particles or both. Despite the antiviral effect of lactoferrin, widely demonstrated in vitro studies, few clinical trials have been carried out and the related mechanism of action is still under debate. The nuclear localization of lactoferrin in different epithelial human cells suggests that lactoferrin exerts its antiviral effect not only in the early phase of surface interaction virus-cell, but also intracellularly. The capability of lactoferrin to exert a potent antiviral activity, through its binding to host cells and/or viral particles, and its nuclear localization strengthens the idea that lactoferrin is an important brick in the mucosal wall, effective against viral attacks and it could be usefully applied as novel strategy for treatment of viral infections. 相似文献
796.
160?Gbit/s all-optical binary-to-quaternary amplitude shift keying format conversion is carried out in a nonlinear optical fiber. This scheme, which also acts as a 2 bit digital-to-analog convertor, has been confirmed through Q-factor measurements. 相似文献
797.
Carlo G. Zambonin Antonella Aresta Torben Nilsson 《International journal of environmental analytical chemistry》2013,93(10):651-657
Solid-phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS) was optimized for the analysis of hexachlorocyclohexanes, DDD, DDE, DDT and other organochlorine pesticides in aqueous samples. Higher extraction efficiency was observed with the SPME fibre coated with 100 µm polydimethylsiloxane than with the fibres coated with 85 µm polyacrylate or 65 µm polydimethylsiloxane/divinylbenzene. Equilibration times were longer than 60 min, except for the hexachlorocyclohexanes, in spite of rapid stirring of the sample. However, precise quantitative analysis could be performed also under non-equilibrium conditions: i.e. repeatability standard deviations below 20%. Salt addition had a positive effect on the response for the hexachlorocyclohexanes, whereas the extraction of the other analytes was affected negatively. The pH of the sample solution did not influence the extraction efficiency. The desorption was performed for 5 min at 275°C directly in the GC injector. At shorter desorption times or lower temperatures a significant carry-over was observed for the heavier analytes. Generally, detection limits in the ng/L range were obtainable. 相似文献
798.
Antonella Capperucci Alessandro Degl'innocenti Catherine Leriverend Patrick Metzner 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):343-344
Abstract A novel and general functionalization of sulfines with organosilanes is reported, disclosing a mild methodology to obtain a regiospecific access to a wide range of different substituted sulfoxides. 相似文献
799.
Antonella Capperucci Alessandro Degl'Innocenti Tiziano Nocentini Giulio Castagnoli Irene Malesci Arianna Cerreti 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5-6):1247-1251
Abstract Bis(trimethylsilyl)sulfide (HMDST) was demostrated to be a very efficient reagent in the delivery of sulfur functionalities, allowing us to synthesize a wide range of thiocarbonyl compounds. The most reactive derivatives were trapped with suitable dienes, leading to the synthesis of different heterocyclic molecules with an high degree of chemo- and regioselectivity. Recently, the mildness of this methodology also allowed us to obtain particularly reactive thiooxocompounds, such as thioformylsilanes, α,β-unsaturated thioaldehydes, thioketones, thioacylsilanes, and thioacylstannanes. 相似文献
800.