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661.
Gad Frankel Alan D. Phillips Ilan Rosenshine Gordon Dougan James B. Kaper & Stuart Knutton 《Molecular microbiology》1998,30(5):911-921
Enteropathogenic (EPEC) and enterohaemorrhagic Escherichia coli (EHEC) constitute a significant risk to human health worldwide. Both pathogens colonize the intestinal mucosa and, by subverting intestinal epithelial cell function, produce a characteristic histopathological feature known as the 'attaching and effacing' (A/E) lesion. Although EPEC was the first E. coli to be associated with human disease in the 1940s and 1950s, it was not until the late 1980s and early 1990s that the mechanisms and bacterial gene products used to induce this complex brush border membrane lesion and diarrhoeal disease started to be unravelled. During the past few months, there has been a burst of new data that have revolutionized some basic concepts of the molecular basis of bacterial pathogenesis in general and EPEC pathogenesis in particular. Major breakthroughs and developments in the genetic basis of A/E lesion formation, signal transduction, protein translocation, host cell receptors and intestinal colonization are highlighted in this review. 相似文献
662.
663.
Ina Fabian Ilan Bleiberg Moshe Aronson 《Biochimica et Biophysica Acta (BBA)/General Subjects》1978,544(1):69-76
Heparin uptake and desulphation by cultured macrophages were investigated. Histones, polyamino-acids, protamine and eosinophil-basic protein stimulated both heparin uptake and desulphation, processes found to be non-related. Poly-l-ornithine and poly-dl-lysine increased the heparin uptake by about 33-fold, and histone produced up to 7.5-fold increase in the desulphation. The same polycations inhibited heparin desulphation by macrophage extracts. 相似文献
664.
Explants of bovine eyes consisting of retina, with its underlying choroid and sclera (termed retinal explants) were maintained in organ culture in the absence or presence of alpha-melanocyte stimulating hormone (alpha-MSH) for up to 19 days. The conditioned media was collected twice a week and assayed for the following eicosanoids, prostaglandin E2 (PGE2) and prostacyclin. The addition of alpha-MSH to the incubation media resulted in a 1.5 fold enhancement in the production of both PGE2 and prostacyclin. This stimulatory effect diminished after 11 days. Additionally, the three tissue components comprising the retinal explants i.e. 1. neural retina 2. retinal pigment epithelium (RPE) with its underlying vascular layer (choroid) and 3. scleral tissue were separated and incubated in the presence or absence of alpha-MSH. Hormone treatment caused an enhanced eicosanoid production by RPE tissue alone, while its production by the neuronal retina and sclera was reduced or unaffected respectively. This demonstrates that the RPE layer is the source for the alpha-MSH induced eicosanoid production observed in the whole retinal explant. Our findings demonstrate, for the first time that alpha-MSH can stimulate prostaglandin production by RPE maintained in organ culture. 相似文献
665.
Ilan Eshel 《Journal of mathematical biology》1981,12(3):355-362
A branching process method is employed to study the survival probability of a slightly advantageous mutant gene with a general distribution of progeny size in a large population. A counter-example to a classic proposition is given. A somewhat weaker result is proved.Supported in part by NIH Grant 5R01 GM10452-18 相似文献
666.
Batchwise purification of liver ribosomes and polysomes on hydroxyl-apatite is a rapid procedure to remove glycogen, hemoglobin, ribonuclease and other contaminants from ribosomal preparations. Ribosomes and polysomes are adsorbed to hydroxylapatite in a Büchner filter funnel and the contaminants are eluted from the hydroxylapatite with 0.15 M KH2PO4. The ribosomes and polysomes are then eluted with 0.3–0.4 M KH2PO4 and concentrated by centrifugation. The resolution of the polysome profiles was greatly improved following purification. The purified ribosomes could be dissociated into subunits at 0.3 M KCl, and showed no loss of activity in poly-U directed phenylalanine synthesis. 相似文献
667.
H. Lorberboum D. Weinstein H. Galski N. de Groot S. Segal J. Ilan R. Folman A. A. Hochberg 《Molecular biology reports》1982,8(2):103-110
The in vitro synthesis of RNA in the human placental tissue, incubated in organ culture, was investigated. We followed the synthesis of the poly A(-) and poly A(+) RNA fractions, and investigated the distribution of the newly synthesized RNA among the subcellular fractions isolated from first and third trimester placentas.The poly A(-) RNA was the major fraction of the RNA synthesized in vitro. The incorporation of [3H]uridine into the poly A(+) RNA fraction was very low.As protein synthesis occurred during the entire incubation period, we suggest the presence of a pool of mRNA molecules in the form of mRNP particles. 相似文献
668.
cytokinin-induced amylolytic activity in bean cotyledons: Identification of the regulated enzyme 总被引:1,自引:0,他引:1
Separation of an extract of cotyledons of Phaseolus vulgarison a column of Sephadex G-200 revealed three amylolytic fractions.The slower migrating fraction hydrolyzed/ß-Limit dextrinazure and was inhibited by EDTA. The activity of this fractionwas enhanced by the embryo axis and this effect could be fullyreplaced by kinetin or benzyladenine. These results suggestthat the bean embryo axis exerts a promotive influence on theactivity of a-amylase in the cotyledons and that this effectis mediated by cytokinins. The other two amylolytic fractions did not show a-amylase activity.No effect of the embryo axis or of cytokinins on their activitycould be noted.
1Present address: The Thimann Laboratories, University of California,Santa Cruz, California, U.S.A. (Received June 27, 1979; ) 相似文献
669.
R. Folman J. Ilan J. Shiklosh N. De Groot S. Segal A. A. Hochberg 《Molecular biology reports》1979,5(3):175-179
Placental tissue slices from first trimester placentas synthesize and secrete proteins labeled by radioactive glucosamine are preferentially secreted as compared to proteins in general. One of the proteins synthesized and secreted is hCG. Processing and secretion of proteins, including hCG, by the tissue slices need a two-hour period. Both secretion and glycosylation of the protein can take place independently of protein synthesis. A method was developed for the specific determination of newly synthesized radioactive hCG in placental tissue.Department of Reproductive Biology, Case Western Reserve University, Cleveland, Ohio, USA 相似文献
670.
Ilan Eshel 《Journal of mathematical biology》1996,34(5-6):485-510
Eighteen different terms, currently employed to define various concepts of evolutionary stability in population dynamics
are mentioned in this paper. Most of these terms are used in different connotations and even different meanings by different
authors. On the other hand, different terms are often employed by different authors to define quite the same concept. Twenty-five
years ago there was only one, well-defined, concept of stability, universally recognized in the field. In this paper I will
try to relate the recent confusion, concerning concepts of population stability, with a more serious, though not that well-recognized,
confusion in the modern analytic approach to population dynamics and quantitative evolution. Concepts of population stability
will be examined in relation to each other on the one hand and, on the other hand, in relation to two dichotomies regarding
the dynamic processes to which they correspond: Short-term versus long-term processes and processes concerning phenotypic
changes versus process concerning genotypic changes. A hopefully more consistent use of the current terminology is suggested.
Received 15 August 1993; received in revised form 15 September 1994 相似文献