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71.
72.
Marc J. Kaufman Tak-Ming Chiu Jack H. Mendelson Bryan T. Woods Nancy K. Mello Scott E. Lukas Peter A. Fivel Lynne G. Wighton 《Magnetic resonance imaging》1994,12(8):1245-1253
Brain alcohol was measured in rhesus monkeys (Macaca mulatta) by proton magnetic resonance spectroscopy (MRS) following acute nasogastric alcohol administration (0.8 g/kg). Monkeys were anesthetized with ketamine and xylazine. A 1.5 T whole body imager and a 3-inch surface coil were used to acquire TE 30 and 270 ms spectra from a 7.5 cc voxel localized with a stimulated echo (STEAM) sequence. Venous blood samples were collected during spectral acquisitions for gas chromatographic determination of temporally concordant blood alcohol levels (BALs). Acute alcohol administration did not alter the resonance areas of N-acetylaspartate/N-acetyl containing compounds (NAA), choline containing compounds, or total creatine. The NAA resonance was used as an internal standard to calculate approximate brain alcohol concentrations, which averaged 27 ± 3% and 27 ± 8% of temporally concordant BALs (T2-corrected TE 30 and TE 270 ms spectra, respectively). In addition to reconfirming results from prior studies finding incomplete detection of brain alcohol with MRS, these results demonstrate the feasibility of measuring brain alcohol in anesthetized nonhuman primates to examine relationships between alcohol exposure history and MRS-visibility of brain alcohol. 相似文献
73.
Parametric ranked set sampling 总被引:1,自引:0,他引:1
Lynne Stokes 《Annals of the Institute of Statistical Mathematics》1995,47(3):465-482
Ranked set sampling was introduced by McIntyre (1952,Australian Journal of Agricultural Research,3, 385–390) as a cost-effective method of selecting data if observations are much more cheaply ranked than measured. He proposed its use for estimating the population mean when the distribution of the data was unknown. In this paper, we examine the advantage, if any, that this method of sampling has if the distribution is known, for a specific family of distributions. Specifically, we consider estimation of and for the family of random variables with cdf's of the formF(x–/). We find that the ranked set sample does provide more information about both and than a random sample of the same number of observations. We examine both maximum likelihood and best linear unbiased estimation of and , as well as methods for modifying the ranked set sampling procedure to provide even better estimation.This paper has been prepared with partial support from the United States Environmental Protection Agency under Cooperative Agreement Number CR821801-01-0. The contents have not been subjected to Agency review and therefore do not necessarily reflect the views or policies of the Agency and no official endorsement should be inferred. 相似文献
74.
Autoantibodies to thyroglobulin in health and disease 总被引:2,自引:0,他引:2
Thyroglobulin (Tg)—a heavily glycosylated, iodinated protein—isa major autoantigen in autoimmune thyroiditis. Tg also induces
thyroiditis by immunization of experimental animals. Humans with chronic lymphocytic thyroiditis characteristically produce
autoantibodies to thyroglobu lin, but similar autoantibodies are also found in some clinically normal, euthyroid individuals.
A comparison of the fine specificity of autoantibodies in humans and in experimentally immunized mice was carried out, based
on their ability to inhibit a panel of monoclonal antibodies (MAbs). Patients with autoimmune thyroid disease, as well as
normal individuals, produced autoantibodies mainly to the conserved, cross-reactive determinants of thyroglobulin. Patients
developed additional autoantibodies to species-restricted epitopes. The determinants recognized by patients with Graves' disease
differed in some respects from epitopes recognized by thyroiditis patients or patients with differentiated thyroid carcinoma.
Similarly, mice that are genetically susceptible to thyroiditis produced autoantibodies that reacted with the mouse-specific
antigenic determinants. Using an autoantibody that reacts with one of the epitopes associated with thyroiditis, a reactive
15-k Da fragment of human Tg—localized at the carboxy end of the molecule—was isolated and sequenced. Iodine plays an important
role in the precise specificity of the disease-associated epitope, since T cells from patients with thyroiditis react with
iodinated but not noniodinated human thyroglobulin. Addition of iodine to Tg generates new or cryptic epitopes. Use of a selected
MAb as a surrogate for the T-cell receptor suggests that a specific iodine-containing epitope is sometimes involved in recognition.
Finally, thyroglobulin-reactive autoantibodies exhibit proteolytic activity on thyroglobulin. 相似文献
75.
Detecting protein-protein interactions with a green fluorescent protein fragment reassembly trap: scope and mechanism 总被引:1,自引:0,他引:1
Magliery TJ Wilson CG Pan W Mishler D Ghosh I Hamilton AD Regan L 《Journal of the American Chemical Society》2005,127(1):146-157
Identification of protein binding partners is one of the key challenges of proteomics. We recently introduced a screen for detecting protein-protein interactions based on reassembly of dissected fragments of green fluorescent protein fused to interacting peptides. Here, we present a set of comaintained Escherichia coli plasmids for the facile subcloning of fusions to the green fluorescent protein fragments. Using a library of antiparallel leucine zippers, we have shown that the screen can detect very weak interactions (K(D) approximately 1 mM). In vitro kinetics show that the reassembly reaction is essentially irreversible, suggesting that the screen may be useful for detecting transient interactions. Finally, we used the screen to discriminate cognate from noncognate protein-ligand interactions for tetratricopeptide repeat domains. These experiments demonstrate the general utility of the screen for larger proteins and elucidate mechanistic details to guide the further use of this screen in proteomic analysis. Additionally, this work gives insight into the positional inequivalence of stabilizing interactions in antiparallel coiled coils. 相似文献
76.
The condensation of an unsymmetrical aromatic diamine with a β-ketoester can afford two theoretically possible dihydrodiazepinone products, differentiation between which is, at best, difficult and laborious. A recently described (3) rearrangement reaction, whereby dihydrodiazepinones are thermally converted into N-substituted imidazolones, has now been applied to the elucidation of structures of ambiguous diazepinone derivatives. By means of the thermal rearrangement method, the diazepinone derivative resulting from the reaction of 2,3-diamino-pyridine and ethyl benzoylacetate, for which structures 1a and 1b are equally plausible, has been definitively characterized as the 2-phenyl-4-one compound, 1a . 相似文献
77.
Byeong C. Jeong Hyun-Won Klm Stephen Owen R. Elaine Dick Lynne E. Macaskie 《Applied biochemistry and biotechnology》1994,47(1):21-32
Tributyl phosphate (TBP) and other alkyl phosphates represent a class of persistent organophosphorus compounds of widespread use. Biodegradation of the phosphotriesters is postulated to occur through sequential hydrolytic cleavages via the phosphodiester and monoester intermediates to alcohol and inorganic phosphate (Pi). Immobilized cells of aCitrobacter sp. liberated Pi upon challenge with TBP but the reaction was short-lived. In vitro studies with purified phosphomonoesterase (phosphatase) used31P nuclear magnetic resonance to demonstrate Pi transfer onto ethanol (phosphotransferase activity). This suggested that in vivo the onset of a futile phosphohydrolytic and transphosphorylation cycle would limit the extent of phosphate production. A mutant deficient in the transphosphorylating phosphomonoesterase showed an extended release of Pi under challenge with TBP that was not subject to the complete and premature reaction termination that precluded application of the parent strain to possible industrial processes for alkyl phosphate biodegradation. 相似文献
78.
The solubilities of bis-8-quinolinolo-zincII, bis-2-methyl-8-quinolinolo-zincII and bis-5 : 7-dibromo-S-quinolinolo-zincII have been measured over the pH range of 4.5 to 9 at ionic strengths of 0.114 and 0.230 and at 25° and 40°. A mathematical treatment of the results gave nearly constant solubility products only when a dissolved but undissociated molecule, in addition to all of the dissociated and partly dissociated species, was considered. The relative abundance of each species of molecule in solution has been calculated. 相似文献
79.
[reaction: see text] At 275 degrees C, 8-exo-methylbicyclo[4.2.0]oct-2-ene (1a) undergoes a [1,3] sigmatropic rearrangement to 5-methylbicyclo[2.2.2]oct-2-enes, of which the orbital symmetry-allowed si product is only marginally favored over the forbidden sr product; that is, si/sr is 2.4. Accompanying the [1,3] shift are significant amounts of epimerization and fragmentation. The 8-endo epimer 1b, which yields no [1,3] product, experiences primarily direct fragmentation and secondarily epimerization. A diradical intermediate can account for all such observations. 相似文献
80.
Kajander T Cortajarena AL Main ER Mochrie SG Regan L 《Journal of the American Chemical Society》2005,127(29):10188-10190
The folding/unfolding transitions of a series of designed consensus tetratricopeptide repeat proteins are quantitatively described by the classical one-dimensional Ising model, which thus represents a new folding paradigm for repeat proteins. Moreover, for the first time for any protein, a theoretical model predicts the folding/unfolding transition midpoint and the width of the transition. 相似文献