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141.
142.
Does a high UV environment ensure adequate vitamin D status? 总被引:1,自引:0,他引:1
Kimlin M Harrison S Nowak M Moore M Brodie A Lang C 《Journal of photochemistry and photobiology. B, Biology》2007,89(2-3):139-147
This study assesses the Vitamin D status of 126 healthy free-living adults aged 18-87 years, in southeast Queensland, Australia (27 degrees S) at the end of the 2006 winter. Participants provided blood samples for analysis of 25(OH)D (the measure of an individual's Vitamin D status), PTH, Calcium, Phosphate, and Albumin, completed a questionnaire on sun-protective/sun-exposure behaviours, and were assessed for phenotypic characteristics such as skin/hair/eye colour and BMI. We found that 10.2% of the participants had serum 25(OH)D levels below 25 nmol/l (considered deficient) and a further 32.3% had levels between 25 nmol/l and 50 nmol/l (considered insufficient). Our results show that low levels of 25(OH)D can occur in a substantial proportion of the population at the end of winter, even in a sunny climate. 25(OH)D levels were higher amongst those who spent more time in the sun and lower among obese participants (BMI>30) than those who were not obese (BMI<30). 25(OH)D levels were also lower in participants who had black hair, dark/olive skin, or brown eyes, when compared with participants who had brown or fair hair, fair skin, or blue/green eyes. No associations were found between 25(OH)D status and age, gender, smoking status, or the use of sunscreen. 相似文献
143.
Smith DP Giles K Bateman RH Radford SE Ashcroft AE 《Journal of the American Society for Mass Spectrometry》2007,18(12):2180-2190
The precise mechanism of protein folding remains elusive and there is a deficiency of biophysical techniques that are capable of monitoring the individual behavior of copopulated protein conformers during the folding process. Herein, an ion mobility spectrometry (IMS) device integrated with electrospray ionization mass spectrometry (ESI-MS) has been used to successfully separate and analyze protein conformers differing in cross section and/or charge state. In an initial test, an ensemble of folded and partially folded conformers of the protein cytochrome c was separated. A detailed study undertaken on the amyloidogenic protein beta(2)-microglobulin (beta(2)m), which forms fibrils by protein unfolding followed by self-aggregation and is responsible for the disease dialysis-related amyloidosis, has generated important insights into its folding landscape. Initially, a systematic titration of beta(2)m over the pH range 2 to 7 using ESI-IMS-MS allowed individual conformers to be monitored and quantified throughout the acid denaturation process. Furthermore, a comparison of wild-type beta(2)m with single and double amino acid variants with a range of folding stabilities and propensities for amyloid fibril formation has provided illuminating evidence of the role of different conformers in protein stability and amyloidogenic aggregation. The ESI-IMS-MS data presented here not only demonstrate an important and informative further dimension to ESI-MS, but also illustrate the potential of the ESI-IMS-MS technique for unravelling protein folding enigmas in general and studying protein misfolding diseases in particular. 相似文献
144.
Yang XL Kapoor M Otero FJ Slike BM Tsuruta H Frausto R Bates A Ewalt KL Cheresh DA Schimmel P 《Chemistry & biology》2007,14(12):1323-1333
Disease-causing mutations occur in genes for aminoacyl tRNA synthetases. That some mutations are dominant suggests a gain of function. Native tRNA synthetases, such as tyrosyl-tRNA synthetase (TyrRS) and tryptophanyl-tRNA synthetase, catalyze aminoacylation and are also procytokines that are activated by natural fragmentation. In principle, however, gain-of-function phenotypes could arise from mutational activation of synthetase procytokines. From crystal structure analysis, we hypothesized that a steric block of a critical Glu-Leu-Arg (ELR) motif in full-length TyrRS suppresses the cytokine activity of a natural fragment. To test this hypothesis, we attempted to uncover ELR in the procytokine by mutating a conserved tyrosine (Y341) that tethers ELR. Site-specific proteolytic cleavage and small-angle X-ray scattering established subtle opening of the structure by the mutation. Strikingly, four different assays demonstrated mutational activation of cytokine functions. The results prove the possibilities for constitutive gain-of-function mutations in tRNA synthetases. 相似文献
145.
Gemma E Hulme AN Jahnke A Jin L Lyon M Müller RM Uhrín D 《Chemical communications (Cambridge, England)》2007,(26):2686-2688
Efficient functionalisation of the non-reducing end of uronic acid derivatives and glycosaminoglycan-derived disaccharides using peptide coupling has been achieved, mediated by the water-soluble agent DMT-MM. 相似文献
146.
The effectiveness of the 2,4-dinitrobenzenesulfenyl and 4-nitrobenzenesulfenyl groups as masking and directing groups at the 2-position of pyrrole has been investigated and compared to that of 2-phenylthiopyrrole. The presence of the nitro group(s) enhances stability of the corresponding pyrrole toward acid and does not significantly decrease the ability of the pyrrolic unit to undergo electrophilic aromatic substitution reactions in the form of formylation, nitration, and condensation with aldehydes. The synthetic utility of 2-(2,4-dinitrobenzenesulfenyl)pyrrole was demonstrated through the synthesis of meso-substituted dipyrromethanes. The sulfoxides 2-(2,4-dinitrobenzenesulfinyl)pyrrole and 2-(4-nitrobenzenesulfinyl)pyrrole underwent neither formylation nor nitration, and the increasing presence of nitro groups within the moiety at the 2-position resulted in decreased stability under acidic conditions. 相似文献
147.
Ali AA Benson RE Blumentritt S Cameron TS Linden A Wolstenholme D Thompson A 《The Journal of organic chemistry》2007,72(13):4947-4952
The diastereoselective syntheses of Zn(II) bis(dipyrrinato) helicates is reported, involving ligands templated by the incorporation of homochiral binol within the linker joining the two dipyrrinato units. The most diastereoselective formation of dinuclear bis(dipyrrinato) helicates to date is reported. The formation of either mononuclear or dinuclear helicates can be tuned by varying the length of the linker between the dipyrrinato units and by varying the complexation procedure. The neutral dipyrrinato helicates were readily analyzed by HPLC to ascertain diastereoselectivity, and circular dichroism studies revealed the helical nature of the complexes. The molar ellipticities of the helicates produced by diastereoselective complexation are very large in the visible region and typically correspond to binol moieties in the UV region. Extensive X-ray crystallographic investigations further confirmed the helicity of the mononuclear Zn(II) helicates and identified significant interlayer displacement and bending within crystals. 相似文献
148.
Yu SS Tan ES Jane RT Downard AJ 《Langmuir : the ACS journal of surfaces and colloids》2007,23(22):11074-11082
Nitrophenyl (NP) films were grafted to glassy carbon and pyrolyzed photoresist films by electroreduction of the corresponding diazonium salt. The as-prepared, multilayered films were examined using electrochemistry and X-ray photoelectron spectroscopy (XPS). Electrochemical analysis confirmed the absence of electrooxidizable groups whereas XPS showed approximately 35% of N was present in a reduced form. The reduced N is assigned to azo groups, which are known to be electroinactive in the film environment. NP films were reduced electrochemically in three media and also by chemical reduction in ethanolic disodium sulfide. The concentrations of aminophenyl and hydroxylaminophenyl groups produced by each method were estimated electrochemically, and the relative amounts of unreacted NP groups were established from XPS measurements. Aminophenyl is the major product for all reduction methods, and Na2S gives the cleanest and most complete conversion to aminophenyl groups, with less than 5% residual NP. Reduced NP films were reacted with carboxylic acid and acid chloride derivatives; the highest yield of electroactive-coupled product was obtained for a film electroreduced in H2SO4 and reacted with acid chloride. The detailed electrochemical and XPS analysis reveals the limitations of electrochemistry for determining the composition of these films. 相似文献
149.
Owen T Pynn R Hammouda B Butler A 《Langmuir : the ACS journal of surfaces and colloids》2007,23(18):9393-9400
Small-angle neutron scattering (SANS), cryogenic transmission electron microscopy (cryo-TEM), and dynamic light scattering (DLS) were used to study the metal-dependent phase behavior of microbially produced surfactants-marinobactins B, D, and E (MB, MD, and ME). Marinobactins A-E are siderophores that facilitate Fe(III) acquisition by the source bacterium through the coordination of Fe(III) by the peptidic headgroup. All of the marinobactins have the same six amino acid headgroup but differ in the length and saturation of the monoalkyl fatty acid tail. Fe(III) coordinated to ME (Fe(III)-ME) was found to form micelles with a diameter of approximately 3.5 nm that underwent a supramolecular transformation to produce a monodisperse population of vesicles with an average diameter ranging from approximately 90 to 190 nm upon addition of Cd(II), Zn(II), or La(III). SANS profiles of the transition-metal-induced phase exhibit a Bragg peak at QB approximately 0.11-0.12 A-1 and were fit to a SANS model for multilamellar vesicles that have an interbilayer repeat distance of 2pi/QB approximately 5.6-5.0 nm. Cryo-TEM images of the Zn(II)-induced phase reveals the presence of approximately 100 nm diameter approximately spherical aggregates of uniform electron density. The temperature dependence of the Zn(II)-induced transformation was also investigated as a function of the length and degree of unsaturation of the Fe(III)-marinobactin fatty acid tail. The Cd(II)-, Zn(II)-, and La(III)-induced phase changes have features that are similar to those of the previously reported Fe(III)-induced micelle-to-vesicle transition, and this observation has opened questions regarding the role that Cd(II) and Zn(II) may play in bacterial iron uptake. 相似文献
150.
Organic films have been grafted to polished glassy carbon (GC) and as-prepared pyrolyzed photoresist film (PPF) by photolysis of alkenes and an alkyne. The alkene or alkyne is spin-coated onto the carbon surface and photolyzed in air at 254 nm. Characterization by water contact angle measurements, depth profiling and surface roughness measurements using atomic force microscopy (AFM), and electrochemistry reveal that for most modifiers a loosely packed monolayer is grafted to the surface. Grafted layers of 1-decene were further reacted by drop-coating with oxalyl chloride and photolyzing at 254 nm in air. The procedure adds acid chloride groups to the film. Amines were attached to these films via amide bond formation, and were characterized by electrochemistry and assembly of citrate-capped gold nanoparticles. Amines were also coupled to photografted 1-undecylenic acid layers and to carboxyphenyl layers prepared by electroreduction of the corresponding diazonium salt. Quantitative analysis using electrochemistry established that the highest concentration of amines was attached to the oxalyl chloride treated film, and that a higher concentration of amines was attached via reaction with the photografted 1-undecylenic acid layer than the electrografted carboxyphenyl layer. Thus photografting and photoreaction with oxalyl chloride are simple methods for generating amine-reactive tethers on GC and PPF surfaces. 相似文献