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681.
Bovine lymphocyte chromatin contains a protein capable of binding colchicine suggesting that it is tubulin. Polyacrylamide gel electrophoresis of the chromatin proteins in the presence of sodium dodecyl sulfate (SDS) shows the presence of proteins co-migrating with tubulin and actin respectively. These two proteins are among the major protein constituents of the chromatin. 相似文献
682.
The yielding and flow behaviour of plant suspensions are perhaps the most important rheological properties in process and
product design for applications in paper, biofuel and food industries. Studies are reported here on the yield properties and
flow behaviour of suspensions of plant particles with different shapes (clusters of cells, individual cells and cell fragments).
Carrot and tomato were selected as model plant systems to prepare suspensions at particle dry mass concentrations ranging
from 0.010 to 0.065. The flow behaviour was characterised by an apparent yield stress and shear thinning. The Herschel-Bulkley
yield stress obtained from up and return flow curves was compared to the yield stress calculated from oscillatory measurements.
The dependence of the yield stress values on particle dry mass concentration is approximately a power-law, with a fitted exponent
of 3 ± 0.5 for all the suspensions, independently of the plant origin and particle shape. This same power-law behaviour was
found for the elastic modulus G′, and in this case the exponent was 3 for carrot and 4 for the tomato suspensions. The yield
strain, calculated from oscillatory measurements, decreased slightly with dry mass fraction, but did not follow a power-law.
We discuss possible explanations for power law behaviour, and provide a model for G′ based on folded elastic sheets, which
predicts an exponent of 3, similar to the values obtained for these suspensions. 相似文献
683.
K. M. Farr D. M. Jones P. E. O'Sullivan G. Eglinton D. H. Tarling R. E. M. Hedges 《Hydrobiologia》1991,214(1):279-292
Studies of frozen and soft mud cores from Ellesmere Mere, Rostherne Mere and Berrington Pool, the three deepest of the Shropshire-Cheshire meres of the English Midlands, reveal the presence of laminations which may be varves. This hypothesis is being tested by means of fine resolution diatom and other microfossil analysis after the method of Simola (1977). Even where the laminations are faint and disrupted, it appears that seasonal signals from algal blooms are preserved.Organic geochemical analyses of sediments from Ellesmere show that the uppermost layers contain abundant organic matter (over 17% total dry matter) and that the extractable lipid fractions from different horizons exhibit clear compositional differences. These are produced by temporal changes in the organic inputs to the sediments, and also by diagnetic effects.The clastic and organic content of the cores also provides evidence for lake level variations in this area over the last 250 years. 相似文献
684.
A relational database for sequence-specific protein NMR data 总被引:9,自引:0,他引:9
Beverly R. Seavey Elizabeth A. Farr William M. Westler John L. Markley 《Journal of biomolecular NMR》1991,1(3):217-236
Summary A protein NMR database has been designed and is being implemented. The database is intended to contain solution NMR results from proteins and peptides (larger than 12 residues). A relational database format has been chosen that indexes data by: primary journal citation, molecular species, sequence-related and atom-specific assignments, and experimental conditions. At present, all data are entered from the primary refereed literature. Examples are given of sample queries to the database. Possible distribution formats are discussed. 相似文献
685.
The spontaneous breathing of a subject during measurements of respiratory impedance (Zrs) by the forced oscillation technique (FOT) induces errors that result in biased impedance estimates, especially at low frequencies. Although in standard measurements this bias may be avoided by using special impedance estimators, there are two applications of FOT for which such estimators are not useful: when a head generator is used and when measurements are made during intubation. In this paper we describe a data-processing procedure for unbiased impedance estimation for all FOT setups. The proposed estimator (Z) was devised for pseudorandom excitation and is based on time-domain signal averaging before frequency analysis. The performance of estimator Z was first analyzed by computer simulation of a head generator setup and a setup including an endotracheal tube to measure (2-32 Hz) a resistance-inertance-elastance model mimicking Zrs of a healthy subject. Second, Z was assessed during real measurements in 16 healthy subjects. The results obtained in the simulation (e.g., error in elastance was reduced from 15.6% with most conventional estimators to 3.3% with Z in simulation of head generator setup) and in the measurements in subjects (differences of less than 1.6% between Z and a reference) confirmed the theoretical lack of bias of Z and its practical suitability for the different FOT setups. In addition to its applicability in the situations in which no other unbiased estimators are available, estimator Z is also advantageous in most conventional applications of FOT, since it requires much less computing time and thus allows on-line Zrs measurements. 相似文献
686.
687.
M. A. Farré Castany H. H. Nguyen M. Pospíšil P. Frič H. Tlaskalová-Hogenová 《Folia microbiologica》1995,40(6):615-620
To analyze the possible involvement of natural killer (NK) cell activity in the pathogenetic mechanism of cœliac disease (CD)
we measured the spontaneous cytotoxic cell activity of peripheral blood mononuclear cells (PMNC) from patients with CD and
from healthy donors. No significant differences were found between the NK cell activity of PMNC from healthy donors and from
patients with CD using a standard51Cr release assay. However, a 30-min treatment of PMNC with gliadin inhibited NK cell activity in patients with CD. On the
other hand, a 1-d incubation with gliadin induced cytotoxic cell activity of PMNC against the NK-resistant target cells such
as the epithelial HT-29 and the lymphoblastoid RAJI cell lines, suggesting that activation of PMNC by cultivation with gliadin
can occur. 相似文献
688.
Differences in Zn-induced levels of hepatic metallothionein (MT) in inbred strains of the mouse are described. Three low-producing
strains, C57BL/6, C57BL/10, and NIH, are identified, while C3H and CBA display the highest levels of hepatic MT following
Zn treatment. These interstrain differences affect not only the level of MT protein, but also the amount of MT-bound Zn and
the total hepatic Zn concentration. Both MT isoforms are equally affected. A similar interstrain difference following Cu treatment
is present in C3H and C57BL/6. The origin of these interstrain differences is discussed. 相似文献