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991.
Fermentation of Inulin by Clostridium thermosuccinogenes sp. nov., a Thermophilic Anaerobic Bacterium Isolated from Various Habitats 总被引:2,自引:0,他引:2 下载免费PDF全文
Wim J. Drent Greetje A. Lahpor Wim M. Wiegant Jan C. Gottschal 《Applied microbiology》1991,57(2):455-462
Four closely related strains of thermophilic bacteria were isolated via enrichment in batch and continuous culture with inulin as the sole source of carbon and energy by using inoculations from various sources. These new strains were isolated from beet pulp from a sugar refinery, soil around a Jerusalem artichoke, fresh cow manure, and mud from a tropical pond in a botanical garden. The cells of this novel species of strictly anaerobic, gram-positive bacteria were rod shaped and nonmotile. Growth on inulin was possible between 40 and 65°C, with optimum growth at 58°C. All strains were capable of fermenting a large number of sugars. Formate, acetate, ethanol, lactate, H2, and succinate were the main organic fermentation products after growth on fructose, glucose, or inulin. Synthesis of inulinase in batch culture closely paralleled growth, and the enzyme was almost completely cell bound. Strain IC is described as the type strain of a new species, Clostridium thermosuccinogenes sp. nov., with a G+C content of 35.9 mol%. 相似文献
992.
Wim Van Hul Hubert Backhovens Guy Van Camp Piet Stinissen Marc Cruts Anita Wehnert Christine Van Broeckhoven 《Human genetics》1991,87(2):109-111
Summary We were able to refine the chromosomal position of two existing marker loci, using an extended chromosome 21 somatic cell hybrid panel. The locus D21S26 mapped in the region 21q11.2–q21.1, and the locus D21S24 in 21q22.1–q22.2. Physical and genetic analysis indicated that D21S26 is tightly linked to D21S13 and D21S16, two markers previously linked to familial Alzheimer's disease. 相似文献
993.
994.
Patricia L. Ringeling Maud I. Cleton Marja I. E. Huijskes-Heins Marionne J. E. Seip Wim C. de Bruijn Henk G. van Eijk 《Biometals》1990,3(3-4):176-182
Summary The livers of iron-loaded rats were fractionated and a cytosolic fraction, a lysosomal fraction, a siderosomal fraction and haemosiderin were obtained. All iron-containing compounds from these fractions were isolated and their morphology, Fe/P ratios, iron core diameter and peptide content were compared. The cytosolic fraction contained ferritin (CF) and a slower sedimenting, light ferritin (CLF). The lysosomal fraction also contained ferritin (LF) and a slower sedimenting light ferritin (LLF). The siderosomal fraction contained ferritin (SF), a faster sedimenting non-ferritin iron compound (SIC) and haemosiderin (HS). SIC and HS did not resemble ferritin as much as the other products did, but were found to be water-insoluble aggregates. The Fe/P ratios of CF and CLF were lower than the Fe/P ratios of LF and LLF and these in turn had lower Fe/P ratios than SF, SIC and HS. The iron core diameter of the cytosolic ferritin was increased after lysosomal uptake. The iron core diameters of the siderosomal products were smaller. CLF, CF, LF, LLF and SF contained one kind of subunit of approximately 20.5 kDa. SIC and HS contained other peptides in addition to the 20.5-kDa subunit. The results indicate that storage of ferritin molecules is not limited to the cytosolic compartment, but is also the case in the lysosomes. Extensive degradation of the ferritin molecule seems to be confined to the siderosomes. 相似文献
995.
Evidence for duplication of the human salivary amylase gene 总被引:3,自引:0,他引:3
Jan C. Pronk Rune R. Frants Wim Jansen Aldur W. Eriksson Gerard J. M. Tonino 《Human genetics》1982,60(1):32-35
Summary Isoelectric focusing of human parotid saliva reveals different -amylase patterns reflecting qualitative and quantitative variations. A puzzling pattern, which shows three different amylase gene products, was found in four individuals. Based on this observation a model is presented in which the salivary amylase gene is duplicated. Family studies show that the AMY1
*
A2 gene forms a haplotype with the normal gene, AMY1
*
A1, whereas the AMY1
*
A3 gene still exists in a single form. The absence of homozygote 2-2 in offspring of 1-2x1-2 marriages and in population material, and the fact that the variant protein makes up about only 20–30% of the total amylase protein in heterozygotes can be considered as additional evidence supporting the hypothesis. The possibility that cis-acting regulatory variants are involved in the patterns with quantitative variation is discussed. 相似文献
996.
997.
998.
Hellingwerf KJ Crielaard WC Joost Teixeira de Mattos M Hoff WD Kort R Verhamme DT Avignone-Rossa C 《Antonie van Leeuwenhoek》1998,74(4):211-227
Among the signal transfer systems in bacteria two types predominate: two-component regulatory systems and quorum sensing systems. Both types of system can mediate signal transfer across the bacterial cell envelope; however, the signalling molecule typically is not taken up into the cells in the former type of system, whereas it usually is in the latter. The Two-component systems include the recently described (eukaryotic) phosphorelay systems; quorum sensing systems can be based upon autoinducers of the N-acylated homoserine lactones, and on autoinducers of a peptidic nature. A single bacterial cell contains many signalling modules that primarily operate in parallel. This may give rise to neural-network behaviour. Recently, however, for both types of basic signal transfer modules, it has been demonstrated that they also can be organised in series (i.e. in a hierarchical order). Besides their hierarchical position in the signal transduction network of the cell, the spatial distribution of individual signalling modules may also be an important factor in their efficiency in signal transfer. Many challenges lie hidden in future work to understand these signal transfer processes in more detail. These are discussed here, with emphasis on the mutual interactions between different signal transfer processes. Successful contributions to this work will require rigorous mathematical modelling of the performance of signal transduction components, and -networks, as well as studies on light-sensing signal transduction systems, because of the unsurpassed time resolution obtainable in those latter systems, the opportunity to apply repeated reproducible stimuli, etc. The increased understanding of bacterial behaviour that already has resulted – and may further result – from these studies, can be used to fine-tune the beneficial activities of bacteria and/or more efficiently inhibit their deleterious ones. 相似文献
999.
Methods of assessing population increase in aphids and the effect of growth stage of the host plant on population growth rates 总被引:1,自引:0,他引:1
J. Adriaan Guldemond Wim J. van den Brink Eefje den Belder 《Entomologia Experimentalis et Applicata》1998,86(2):163-173
Realistic values of population growth rates are needed when used in forecasting programmes, e.g., in a programme of integrated control. Therefore, comparisons were made in a chrysanthemum – aphid system between different methods of assessing population growth rates. The reproductive performances of the aphid species Aphis gossypii and Myzus persicae were measured on two chrysanthemum cultivars using three plant growth stages (young vegetative, budding and flowering). In the first set of experiments, development time and reproduction were used to estimate the population growth rate rm. The mean relative growth rates (MRGR) were also assessed. It was shown for the first time that the relationship between rm and MRGR was influenced by aphid species. In a second experiment, the aphid population increase on a whole plant was measured and rm was estimated by calculating the slope of the (ln transformed) population increase. It is shown that population growth rate is affected by the growth stage of the plant, and that cultivar and aphid species interact with plant growth stage in influencing population growth rate. Thus, no single growth stage of chrysanthemum for maximal aphid population growth can be assigned, but the budding and flowering stage are the most suitable in three out of four aphid × cultivar combinations. Comparison between the results from both experiments demonstrates clearly that more realistic values for rm are obtained when measured on whole plants. 相似文献
1000.
Ton H. J. Naber Cornelis J. A. van den Hamer Wim J. M. van den Broek Jan H. M. van Tongeren 《Biological trace element research》1992,35(2):137-152
In zinc deficiency, the function of leukocytes is impaired. However, the results of studies on the zinc concentration of blood
cells in zinc deficiency are conflicting, probably in part because of technical and analytical problems. The aim of this study
was to investigate, under standard conditions, the uptake of65Zn-labeled zinc by blood cells, taken from zinc-deficient rats and from rats in which an inflammation is induced. In both
conditions, the serum zinc concentration is reduced. In clinical practice, this makes it difficult to determine whether the
decrease in serum zinc is the result of a real or an apparent zinc deficiency. In stress, like an inflammatory disease, the
decrease of zinc reflects an apparent zinc deficiency because of redistribution of serum zinc into the liver and because of
decrease in serum albumin concentration. Over 70% of the serum zinc is bound to albumin. Blood cells from zinc-deficient and
control rats were isolated using a discontinuous Percoll gradient and incubated under nearly physiological conditions in a65Zn-containing medium. A significant increase in the in vitro uptake of65Zn-labeled zinc by the blood cells of zinc-deficient rats was seen: erythrocytes 1.3, mononuclear cells 2.0, and polymorphonuclear
cells 2.6 times the control values. During inflammation, no change in65Zn-labeled zinc uptake by erythrocytes and mononuclear cells was demonstrated after 2 d, although the serum zinc and albumin
concentrations were decreased, but a small but significant increase in zinc uptake by polymorphonuclear cells was observed.
This study of65Zn uptake in vitro under standard conditions may prove of value for distinguishing in patients real zinc deficiency from apparent
zinc deficiency owing to, e.g., stress, although additional experiments should be performed.
A part of this study has been presented at the Meeting of The American Gastroenterological Association on May 12–18, 1990,
San Antonio, TX, and has been published in abstract inGastroenterology
98 suppl., A423. 相似文献