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921.
922.
Hannes Flckner Michael Braxenthaler Peter Lackner Markus Jaritz Maria Ortner Manfred J. Sippl 《Proteins》1995,23(3):376-386
The prediction experiment reveals that fold recognition has become a powerful tool in structural biology. We applied our fold recognition technique to 13 target sequences. In two cases, replication terminating protein and prosequence of subtilisin, the predicted structures are very similar to the experimentally determined folds. For the first time, in a public blind test, the unknown structures of proteins have been predicted ahead of experiment to an accuracy approaching molecular detail. In two other cases the approximate folds have been predicted correctly. According to the assessors there were 12 recognizable folds among the target proteins. In our postprediction analysis we find that in 7 cases our fold recognition technique is successful. In several of the remaining cases the predicted folds have interesting features in common with the experimental results. We present our procedure, discuss the results, and comment on several fundamental and technical problems encountered in fold recognition. © 1995 Wiley-Liss, Inc. 相似文献
923.
Frieder Schauer Kirsten Henning Helmut Pscheidl Rolf M. Wittich Peter Fortnagel Heinz Wilkes Volker Sinnwell Wittko Francke 《Biodegradation》1995,6(2):173-180
Trichosporon beigelii SBUG 752 was able to transform diphenyl ether. By TLC, HPLC, GC, GC-MS, NMR- and UV-spectroscopy, several oxidation products were identified. The primary attack was initiated by a monooxygenation step, resulting in the formation of 4-hydroxydiphenyl ether, 2-hydroxydiphenyl ether and 3-hydroxydiphenyl ether (48:47:5). Further oxidation led to 3,4-dihydroxydiphenyl ether. As a characteristic product resulting from the cleavage of an aromatic ring, the lactone of 2-hydroxy-4-phenoxymuconic acid was identified. The possible mechanism of ring cleavage to yield this metabolite is discussed. 相似文献
924.
Peter Sowig 《Ecography》1995,18(2):147-154
Paracoprid dung beetles build brood chambers in the soil beneath a dung pat and provide them with dung Onthophagus species lay one egg into each chamber This paper deals with the influence of soil type and soil moisture on micro-habitat selection and survival of offspring m three middle-European Onthophagus-species ( O coenobita, O fracticonis and O vacca) Discrimination between sandy soils with three different loam contents (0%, 20%, 40%) and four different water contents (4%, 8%, 12%, 16%) was tested in the laboratory During the first 24 h of each replicate beetles which colonized one of the patches did not distinguish between different soil conditions Emigration rates, measured as time when 50% of all individuals had left the patch, and numbers of brood chambers proved to be species specific and depended on soil moisture and soil type Survival rates of the larvae in the brood chambers were influenced nearly exclusively by soil moisture The results are discussed in relation to the ecology of the three species and in context with optimal foraging theories 相似文献
925.
Summary Proton chemical shifts of a series of disordered linear peptides (H-Gly-Gly-X-Gly-Gly-OH, with X being one of the 20 naturally
occurring amino acids) have been obtained using 1D and 2D 1H NMR at pH 5.0 as a function of temperature and solvent composition. The use of 2D methods has allowed some ambiguities in
side-chain assignments in previous studies to be resolved. An additional benefit of the temperature data is that they can
be used to obtain ‘random coil’ amide proton chemical shifts at any temperature between 278 and 318 K by interpolation. Changes
of chemical shift as a function of trifluoroethanol concentration have also been determined at a variety of temperatures for
a subset of peptides. Significant changes are found in backbone and side-chain amide proton chemical shifts in these ‘random
coil’ peptides with increasing amounts of trifluoroethanol, suggesting that caution is required when interpreting chemical
shift changes as a measure of helix formation in peptides in the presence of this solvent. Comparison of the proton chemical
shifts obtained here for H-Gly-Gly-X-Gly-Gly-OH with those for H-Gly-Gly-X-Ala-OH [Bundi, A. and Wüthrich, K. (1979) Biopolymers, 18, 285–297] and for Ac-Gly-Gly-X-Ala-Gly-Gly-NH2 [Wishart, D.S., Bigam, C.G., Holm, A., Hodges, R.S. and Sykes, B.D. (1995) J. Biomol. NMR, 5, 67–81] generally shows good agreement for CH protons, but reveals significant variability for NH protons. Amide proton chemical
shifts appear to be highly sensitive to local sequence variations and probably also to solution conditions. Caution must therefore
be exercised in any structural interpretation based on amide proton chemical shifts. 相似文献
926.
Peter Allard Jüri Jarvet Anders Ehrenberg Astrid Gräslund 《Journal of biomolecular NMR》1995,5(2):133-146
Summary The peptide hormone motilin was synthesised with a 13C-enriched -carbon in the leucine at position 10. In aqueous solution, six different relaxation rates were measured for the 13C–H fragment as a function of temperature and with and without the addition of 30% (v/v) of the cosolvent d
2-1,1,1,3,3,3-hexafluoro-2-propanol (HFP). The relaxation rates were analysed employing the spectral density mapping technique introduced by Peng and Wagner [(1992) J. Magn. Reson., 98, 308–322] and using the model-free approach by Lipari and Szabo [(1982) J. Am. Chem. Soc., 104, 4546–4570]. The fit to various models of dynamics was also considered. Different procedures to evaluate the overall rotational correlation time were compared. A single exponential time correlation function was found to give a good fit to the measured spectral densities only for motilin in 30% (v/v) HFP at low temperatures, whereas at high temperatures in this solvent, and in D2O at all temperatures, none of the considered models gave an acceptable fit. A new empirical spectral density function was tested and found to accurately fit the experimental spectral density mapping points. The application of spectral density mapping based on NMR relaxation data for specific 13C–1H vector is shown to be a highly useful method to study biomolecular dynamics. Advantages are high sensitivity, high precision and uniform sampling of the spectral density function over the frequency range.Abbreviations CD
circular dichroism
- NOE
nuclear Overhauser enhancement
- NOESY
two-dimensional NOE spectroscopy
- INEPT
insensitive nuclei enhanced by polarisation transfer
- DANTE
delays alternating with nutations for tailored excitation
- WALTZ-16
wideband, alternating phase, low-power technique for zero residual splitting
- FID
Free induction decay
- ppm
parts per million
- TSPA
3-trimethylsilyl-(3,3,2,2-d)-propionic acid
- HFP
d
2-1,1,1,3,3,3-hexafluoro-2-propanol
- CPMG
Carr-Purcell-Meiboom-Gill
- TFD
time-resolved fluorescence depolarisation
- CSA
chemical shift anisotropy
Partly presented at the symposium Dynamics and Function of Biomolecules, Szeged, Hungary, July 31–August 2, 1993. 相似文献
927.
He Liu H. Peter Spielmann Nikolai B. Ulyanov David E. Wemmer Thomas L. James 《Journal of biomolecular NMR》1995,6(4):390-402
Summary The effect of experimental and integration errors on the calculations in interproton distances from NOE intensities is examined. It is shown that NOE intensity errors can have a large impact on the distances determined. When multiple spin (spin diffusion) effects are significant, the calculated distances are often underestimated, even when using a complete relaxation matrix analysis. In this case, the bias of distances to smaller values is due to the random errors in the NOE intensities. We show here that accurate upper and lower bounds of the distances can be obtained if the intensity errors are properly accounted for in the complete relaxation matrix calculations, specifically the MARDIGRAS algorithm. The basic MARDIGRAS algorithm has been previously described [Borgias, B.A. and James, T.L. (1990) J. Magn. Reson., 87, 475–487]. It has been shown to provide reasonably good interproton distance bounds, but experimental errors can compromise the quality of the resulting restraints, especially for weak cross peaks. In a new approach introduced here, termed RANDMARDI (random error MARDIGRAS), errors due to random noise and integration errors are mimicked by the addition of random numbers from within a specified range to each input intensity. Interproton distances are then calculated for the modified intensity set using MARDIGRAS. The distribution of distances that define the upper and lower distance bounds is obtained by using N randomly modified intensity sets. RANDMARDI has been used in the solution structure determination of the interstrand cross-link (XL) formed between 4-hydroxymethyl-4,5,8-trimethylpsoralen (HMT) and the DNA oligomer d(5-GCGTACGC-3)2 [Spielmann, H.P. et al. (1995) Biochemistry, 34, 12937–12953]. RANDMARDI generates accurate distance bounds from the experimental NOESY cross-peak intensities for the fixed (known) interproton distances in XL. This provides an independent internal check for the ability of RANDMARDI to accurately fit the experimental data. The XL structure determined using RANDMARDI-generated restrains is in good agreement with other biophysical data that indicate that there is no bend introduced into the DNA by the cross-link. In contrast, isolated spin-pair approximation calculations give distance restraints that, when applied in a restrained molecular dynamics protocol, produce a bent structure.Abbreviations NOE
nuclear Overhauser effect
- SD
standard deviation
- HMT
4-hydroxymethyl-4,5,8-trimethylpsoralen
- XL
psoralen-DNA interstrand cross-link 相似文献
928.
David E. Lacy Anthony W. Smith David E. Stableforth Grace Smith Peter H. Weller Michael R.W. Brown 《FEMS immunology and medical microbiology》1995,10(3-4):253-262
Abstract Burkholderia cepacia (Pseudomonas cepacia) is now recognised as an important pathogen in cystic fibrosis patients, and several reports have suggested that sputum-culture-proven colonisation occurs despite the presence of specific antibody. In an attempt to establish the use of antibody studies as diagnostic and prognostic indicators of B. cepacia infection, we have examined the IgG response to B. cepacia outer membrane proteins and lipopolysaccharide in patients also colonised with P. aeruginosa . The B. cepacia strains were grown in a modified iron-depleted chemically defined medium and outer membrane components examined by SDS-PAGE and immunoblotting. IgG antibodies were detected against B. cepacia outer membrane antigens, which were not diminished by extensive preadsorption with P. aeruginosa . The response to B. cepacia O-antigen could be readily removed by adsorption of serum either with B. cepacia whole cells or purified LPS, whereas we were unable to adsorb anti-outer membrane protein antibodies using B. cepacia whole cells. The inability to adsorb anti-outer membrane protein antibodies using B. cepacia whole cells maybe due to non-exposed surface epitopes. Several B. cepacia sputum-culture negative patients colonised with P. aeruginosa had antibodies directed against B. cepacia outer membrane protein. This study suggests that there is a specific anti- B. cepacia LPS IgG response, which is not due to antibodies cross-reactive with P. aeruginosa . Our studies indicate that much of the B. cepacia anti-outer membrane protein response is specific and not attributable to reactivity against co-migrating LPS. 相似文献
929.
M. Teresa García-López Ibon Alkorta M. José Domínguez Rosario González-Mu?iz Rosario Herranz Nils L. Johansen Kjeld Madsen Henning Th?gersen Peter Suzdak 《Letters in Peptide Science》1995,1(6):269-276
Summary In order to enforce different spatial orientations in the C-terminal hexapeptide of neurotensin (NT8–13) and to gain information about the importance of the 10–11 peptide bond for binding to NT receptors, the Pro10-Tyr11 fragment has been replaced with (2R,8S,8aR)-, (2S,8S,8aR)-, (2S,8S,8aS)-, (2S,8R,8aS)- and (2R,8R,8aS)-8-amino-2-benzyl-3-oxoindolizidine-2-carboxylic acid. Molecular dynamics calculations and energy minimization studies have shown that, contrarily to the Pro-Tyr moiety, none of these indolizidines display a tendency to adopt type I and III -turns, but those having (8S,8aR) or (8R,8aS) stereochemistry essentially adopt extended conformations and the (8S,8aS) stereoisomer prefers a nonstandard folding. The four diastereomeric NT8–13 analogues incorporating (8S,8aR) or (8R,8aS) indolizidines displayed binding affinities for the brain NT receptor similar to that of [Ala11]-NT8–13 and only five- to ninefold lower than that of the corresponding analogue, [Phe11]NT8–13. Although this slight decrease could be attributed to differences in conformational behavior between these constrained NT8–13 analogues and [Phe11]NT8–13 or NT8–13, it is not clear whether the -turn around Pro10-AA11 (AA=Phe, Tyr) is conserved upon receptor binding. An excessive restriction in the motions of the aromatic side chain, imposed by the highly steric constraint of the indolizidine moiety, emerges as an alternative explanation. The findings reported here demonstrate the possibility of replacing the Pro10-Tyr11 dipeptide in NT8–13 with a non-peptide residue without affecting considerably the affinity for brain NT receptors. 相似文献
930.
Klaus Kayser Sabine André Gerhard Böhm Sonia Donaldo-Jacinto Peter Fritz Herbert Kaltner Gian Kayser Wolf-Peter Kunze Andreas Nehrlich Fu-Yue Zeng Hans-Joachim Gabius 《Development genes and evolution》1995,204(5):344-349
Protein-carbohydrate interactions are supposed to play key roles in the mechanisms of cell adhesion, biosignalling and intracellular routing, warranting the analysis of the developmental course of expression of epitopes of this system. Thus, a panel of carrier-immobilized carbohydrate ligands was used as probes, namely lactose,N-acetylgalactosamine,N-acetylglucosamine, mannose, fucose and maltose. Additionally, an antibody to an endogenous -galactoside-binding lectin (anti-galectin-1), the biotinylated lectin and two further human lectins, namely the macrophage migration inhibitory factor-binding sarcolectin and serum amyloid P component (SAP) that displays selectivity for sulphated sugars and mannose-6-phosphate, were included. They enabled us to assess the extent of the presence of respective binding sites in fixed sections from human lungs (pulmonary epithelial cells), livers (hepatocytes) and hearts (myocard cells) of 10–50 weeks gestation. Invariably, specific binding was detected in the three organ types, at least in certain stages. In most of the cases, the intensity of staining exhibited developmental regulation. The apparent patterns reveal similarities between the different cell types, as seen with immobilizedN-acetylglucosamine as well as with labelled galectin-1 and sarcolectin. However, drastic differences among such patterns with nearly opposite developmental courses do also occur, as detected for carrier-attached mannose and maltose residues. These results point to a potential importance for the detected glycohistochemical features in human development and substantiate the possibility of differential regulation of the presence of binding sites for distinct sugars within a certain organ and between the individual cell types of the monitored organs. 相似文献