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111.
Summary Conformational preferences of secretin as a model peptide have been analyzed by CD and IR spectroscopy in reverse micelles of AOT/isooctane/water and compared to those in aqueous TFE, in SDS micelles and in DMPG vesicles. Among the systems examined, reverse micelles and phospholipid vesicles displayed almost identical conformational equilibria. Very high lipid-to-peptide ratios can be obtained in reverse micelles with full retention of optical transparency, even at millimolar peptide concentrations, thus indicating this system to be an interesting mimic of cell membrane environments for spectroscopic analysis of bioactive peptide conformations.Abbreviations TFE
trifluoroethanol
- SDS
sodium dodecyl sulfate
- DMPG
dimyristoylphosphatidylglycerol
- AOT
bis(2-ethylhexyl)sulfosuccinate
- CMC
critical micellar concentration
- VIP
vasoactive intestinal peptide 相似文献
112.
113.
Characterization and regulation of the expression of FatB, an iron transport protein encoded by the pJM1 virulence plasmid 总被引:7,自引:0,他引:7
Luis A. Actis Marcelo E. Tolmasky Lidia M. Crosa Jorge H. Crosa 《Molecular microbiology》1995,17(1):197-204
The pJM1-encoded genes fatDCBA are essential for iron acquisition via the siderophore anguibactin. Sequence analysis indicated that the open reading frame corresponding to the fatB gene possesses domains that are characteristic of periplasmic proteins that bind the ferric siderophore. In this work, a monospecific antiserum against an oligopeptide containing the last 27 amino acids of the carboxy-terminal region from this open reading frame was used to demonstrate that fatB encodes a 35 kDa protein that is essential for iron transport. By using this antibody we were able to demonstrate that expression of the fatB gene is negatively regulated by the Fur protein at high iron concentrations. Conversely, its expression was positively regulated by the combined action of the AngR protein and products of the TAF region. FatB, the product of the fatB gene, is isolated with the membrane fraction. In accordance with these findings is the fact that the first 23 amino acid residues of this protein have the properties of a lipoprotein signal sequence. The lipoprotein nature of FatB is supported by the fact that treatment of Vibrio anguillarum cells with globomycin, an inhibitor of the lipoprotein signal peptidase, results in the accumulation of a 38 kDa pro-FatB precursor protein. 相似文献
114.
Location of the active site of the bean {alpha}-amylase inhibitor and involvement of a Trp, Arg, Tyr triad 总被引:1,自引:0,他引:1
Mirkov T.Erik; Evans Stephen V.; Washlstrom Janice; Gomez Luis; Young N.Martin; Chrispeels Maarten J. 《Glycobiology》1995,5(1):45-50
Seeds of the common bean contain three homologous proteins:phytohaemagglutinin E, phytohaemagglutinin L and the lectin-likeprotein 相似文献
115.
Luis Pezzi 《Bioscience reports》1984,4(3):231-237
The rate of ruthenium-red-induced Ca2+ efflux depends on the time that the calcium interacts with the mitochondria prior to the addition of the inhibitor. This time-dependency is abolished in the presence of nupercaine; it does not occur in the case of Sr2+ efflux from mitochondria in which the endogenous Ca2+ has been substituted by strontium (strontium-treated mitochondria, STM). Ruthenium red inhibits the respiratory-inhibitor- or uncoupler-induced Sr2+ efflux from STM, but not the Ca2+ efilux from standard mitochondria. The influence of the calcium-induced mitochondrial damage upon the effect of ruthenium red is discussed. 相似文献
116.
Lelio Orci Michael S. Brown Joseph L. Goldstein Luis M. Garcia-Segura Richard G.W. Anderson 《Cell》1984,36(4):835-845
The crystalloid endoplasmic reticulum (ER) houses large amounts of HMG CoA reductase, the rate-controlling enzyme in cholesterol synthesis. The crystalloid ER appears in UT-1 cells, a line of Chinese hamster ovary cells that has been chronically starved of cholesterol as a result of growth in the presence of compactin, an inhibitor of reductase. When cholesterol was provided to UT-1 cells in the form of low density lipoprotein (LDL), the reductase and crystalloid ER were destroyed. This destruction was preceded by an increase in the cholesterol content of crystalloid ER membranes, as judged by a 4- to 8-fold increase in their ability to form complexes with filipin, a cholesterol-binding compound that can be visualized in freeze-fracture electron micrographs. Filipin binding to other membranes was unchanged. Thus insertion of cholesterol into the crystalloid ER membrane may trigger the degradation of reductase and the membrane itself. 相似文献
117.
Danley A. S. Callieri Carlos G. Núñez Juan C. Díaz Ricci Luis Scidá 《Applied microbiology and biotechnology》1984,19(4):267-271
Summary
Candida utilis var. major NRRL-Y-1084 was grown in a defined medium without a phosphorous (P) source. During the exponential phase, cells divided according to a specific growth rate of 0.32 h-1, which is lower than the usual rate for a balanced medium (0.4–0.6 h-1). The relative P content of the biomass decreased from 2.70% to 0.75% over a period of 6 h, including 2 h of cell division arrest. At the end of this period there was another interruption of cell division. After that, multiplication restarted at a considerably lower rate and it deviated slightly from the exponential pattern. The stationary phase began when biomass P content reached 0.4%–0.5%, slowly decreasing afterwards to 0.25–0.20%. Biomass synthesis was less affected than cell division by the relative decrease of endogenous P, the two processes differing partially in their kinetics. Cell lysis started shortly before the stationary phase and affected about 20% of the population by the end of the assay. RNA and P content of the resulting biomass were 2.4% and 0.25% respecitvely, P being mainly incorporated to RNA.The relationship of biomass production to glucose uptake was very low, probably because the marked P deficiency called for an increase in energy consumption for growth and specially for maintenance. Compared with yeasts grown in a balanced medium, 40% increase in glycogen was observed, whereas no mean changes in the content of cell wall carbohydrates (glucan and mannan) and that of true protein were found.Member of the Scientific Researcher's Career of the Consejo Nacional de Investigaciones Cientificas y Técnicas (CONICET). Agrentina 相似文献
118.
The songs of 15 colour-marked, mated pairs of white-crowned sparrows (Zonotrichia leucophrys nuttalli) were recorded in a contact zone between the Presidio and San Francisco, California dialect regions. Males were recorded in the field and females were trapped after the breeding season and injected with testosterone to induce singing. The song of each member of a mated pair was classified using two different markers. It was found that most pairs did not match song types, and that the reproductive success of those that matched did not differ from those that did not match. Most of the territorial males sang the Presidio dialect, while most injected females sang the San Francisco dialect. The results fail to support a positive assortative mating hypothesis regarding the functional significance of learning dialects. It is suggested that the mismatching of songs could be due to sexual differences in the disposition to learn songs of neighbours at the breeding site. 相似文献
119.
Luis Rodríguez Teresa Ruiz Julio R. Villanueva Rafael Sentandreu 《Current microbiology》1978,1(1):41-44
The intracellular invertase ofSaccharomyces cerevisiae is mainly found in a soluble form (91–95%), while only minor amounts are found bound to the internal (4–8%) and plasma membranes
(less than 1%). In the processes of derepression or repression, inhibition of RNA or protein synthesis, or in the presence
of 2-deoxy-d-glucose, the levels of the membrane-bound and external activities are modified in a way in which their relation is clear,
while the soluble enzyme does not change at all. These results, together with the fact that the membrane-bound and the external
enzymes are glycoproteins, suggest a precursor-product relationship between the enzymic forms. 相似文献
120.
Summary Microelectrode techniques were employed to study the mechanisms of the transepithelial voltage transients (V
ms
) observed during transmural current clamps in the isolatedNecturus gallbladder. The results indicate that: a) part of V
ms
is due to a transepithelial resistance change (R
t
), and part to a tissue emf change. b) R
t
is entirely caused by changes of the resistance of the paracellular pathway. At all current densities employed, the measured changes are probably due to changes in both fluid conductivity and width of the lateral intercellular spaces. At high currents, in addition to the effects on the lateral spaces, the resistance of other elements of the pathway (probably the limiting junction) drops, regardless of the direction of the current. c) The magnitude and polarity of the R
t
-independent transepithelial and cell membrane potential transients indicate that the largest emf change takes place at the basolateral membrane (E
b
), with smaller changes at the luminal membrane (E
a
) and the paracellular (shunt) pathway (E
s
). It is shown that two-thirds of the transient are caused by E
s
, and one-third by (E
b
–E
a
). E
s
can be explained by a diffusion potential generated by a current-dependent NaCl concentration gradient across the tissue. E
a
and E
b
are caused by [K] changes, mainly at the unstirred layer in contact with the basolateral membrane. 相似文献