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261.
262.
Summary From tested yeast-like organisms, onlyGeotrichum candidum showed the same activity of glucose-6-phosphate dehydrogenase with both NAD+ and NADP+. i. e. 0.017–0.019 mol NADH/min. mg dry weight of cell free extracts. Omission of Mg++ in the reaction mixture did not influence the activity of the enzyme in the presence of NAD+. Cell free extracts ofEndomyces magnusii showed only low activity of this enzyme and the ratio of its activity in the presence of NAD+ and NADP+, respectively, varied in individual cultures.Rhodotorula glutinis showed only an NADP+-dependent activity. 相似文献
263.
The possible impact of long-term overexposure to ethanol was studied in a group of chronic alcoholics in the psychiatric hospital. The level of DNA methylation and unscheduled DNA synthesis (UDS) induced by N-methyl-N-nitrosourea (MNU) in lymphocytes and lipid peroxidation (LPO) in plasma were used as markers of injury caused by alcohol abuse. The data were correlated with plasma levels of some natural antioxidants (vitamins A, C and E) and vitamin B12. The following results were obtained. The degree of DNA methylation by MNU in lymphocytes was the same in the exposed and control groups under our experimental conditions. The DNA excision-repair capacity of lymphocytes measured as UDS was decreased in alcoholics (p less than 0.01) and LPO in plasma was significantly higher (p less than 0.01) as a consequence of alcohol overconsumption. By the simple regression method, a correlation was found between LPO and vitamin C levels (LPO = -0.078 x vit. C + 1.9; p less than 0.05) and between UDS and LPO values (UDS = -0.384 x LPO + 4.1; p less than 0.05). These results support the hypothesis of a connection of cell membrane status and DNA damage and repair and the possible role of active oxygen species in cell damage caused by ethanol. 相似文献
264.
Blanka Úlehlová 《Folia Geobotanica》1973,8(4):367-376
In 1963, 1964 and 1965, a comparative ecological study was made of the distribution of mineral elements in the soil and phytomass of some Stipa species, viz.Stipa capillata L., S. pulcherrima C. Koch,S. joannis ?elak.,S. dasyphylla ?erň.,and S. stenophylla ?erň. in various locations of Central Europe. In all species and sites studied, chemical analyses of the soil, fresh phytomass (shoots and roots) and dead phytomass were made, together with relevant statistical evaluation. IndividualStipa species differ according to their mineral composition. In comparison with fresh green plant material, the old dead plant material shows a marked increase in ash, calcium, and natrium content. Potassium, nitrogen, and phosphorus show a decrease in the dead plant material. The mineral composition of the roots differs considerably from that of green plant parts: the roots have much higher ash, phosphorus, calcium and natrium content, and lower organic matter, nitrogen, and potassium content. On the basis of the data collected, an attempt was made to estimate cycling of the individual mineral elements. 相似文献
265.
Slobodan Barbarié Branko Kozulié Blanka Ries Pavao Mildner 《Biochemical and biophysical research communications》1980,95(1):404-409
The protoplast-secreted acid phosphatase of yeast was purified about 60 fold by ultrafiltration, gel filtration and chromatography on DEAE-Sephadex A-25. It was established that the enzyme is free of inactive proteins as well as polysaccharides and contains 48% of neutral sugars. The failure to separate the protein from the carbohydrates by several procedures indicates that the carbohydrate part is covalently linked to the protein. A pronounced heterogeneity of the enzyme with respect to charge as well as to molecular weight was found. The data obtained by gel filtration indicated enzyme heterogeneity in respect to carbohydrate content. 相似文献
266.
267.
Blanka Rovenská 《Biologia Plantarum》1963,5(2):161-165
Sledovali jsme semeník p?enice (Triticum aestivum L. var.erythrospermum cv. Niva, jarní) od oplození vají?ka a? do plné zralosti obilky. Na trvalých preparátech jsme pozorovali tvorbu oplodí a osemení. Zjistili jsme, ?e v dospělé obilce oplodí těsně lne k osermení, z něho? z?stala zachována pouze jednolitá vrstva krytá kutikulou. Epidermis a hypodermis nesr?stá s p?í?nými buňkami, nýbr? pouze k ním p?isychá; je tě?ké mluvit o sr?stu tam, kde skon?il proces dělení a kde vrstvy pletiv jsou odděleny kutikulou. 相似文献
268.
Cloning of the glycerol kinase gene of Bacillus subtilis 总被引:1,自引:0,他引:1
A 3.5 kb fragment of Bacillus subtilis DNA which contains wild type alleles of mutations in glpK (glycerol kinase) and glpD (glycerol-3-phosphate [G3P] dehydrogenase) was cloned in plasmid pHV32 in Escherichia coli. The cloned fragment expresses glycerol kinase in B. subtilis mutants carrying the mutations glpK11 and recE4 after induction with glycerol or G3P whereas it does not express G3P dehydrogenase. The cloned fragment thus contains the complete glpK but probably only part of glpD. 相似文献
269.
General locomotor activity decreases with normal aging in animals and could be partially explained by decreases in neuronal function. Voltage-gated Na+ channels are essential in initiating and propagating rapid electrical impulses underlying normal locomotor activity and behavior in animals. Isolation of mutations conferring temperature-sensitive (ts) paralysis has been an extremely powerful paradigm for identifying genes involved in neuronal functions, such as membrane excitability and synaptic transmission. For instance, decreased expression of wild-type Na+ channels in flies harboring the no-action-potential ( nap ) mutant allele ( mlenapts ) confers rapid and reversible ts paralysis, because of failure of action potential propagation. Here, we report that aging wild-type Drosophila gradually develops an acquired susceptibility to ts paralysis that is indistinguishable from that seen in young ts paralytic mlenapts mutants. Moreover, we show that this general age-dependent susceptibility is also present in mlenapts flies, although the effects are shifted to lower temperature regimes. The mlenapts flies also exhibit decreased lifespan and increased frailty. Paralysis and decreased lifespan of mlenapts flies were partially rescued by increasing the dosage of para , the structural gene for the major action potential Na+ channel in central nervous system of Drosophila . Lastly, we show a dramatic scaling of ts paralysis susceptibility with chronological age in short-lived and long-lived mutant flies, further demonstrating that this age-dependent risk is independent of genetic background. Thus, decreased neural transmission, a hallmark of which is ts paralysis, is a biomarker of aging. 相似文献
270.
Ondřej Koukol Blanka Beňová Magda Vosmanská Tomáš Frantík Miroslav Vosátka Marcela Kovářová 《Plant and Soil》2008,303(1-2):151-159
Different components of functional biodiversity, such as functional type richness and composition, have been reported to affect
the decomposition of litter mixtures. In spite of the numerous reports of these effects, mechanisms underlying patterns of
decomposition in litter mixtures are still unclear. We analyzed whether mixture decomposition was affected by: (a) the number
of species in the mixture (mixture richness); and (b) the mixture’s functional composition (% of fast- vs. slow-decomposing
species included in the mixture). We then tested if variation between observed and expected values of decomposition in mixtures
was associated to: (c) the initial litter characteristics of the component species (initial nitrogen, lignin, cellulose and
hemicellulose content of litters); and (d) the chemical heterogeneity of the mixtures (variation in the same chemical compounds
between the components in each mixture). When up to 5 species representing different functional types were included, both
species richness and functional composition showed statistically significant non-additive, and in general positive, effects
on litter mixture decomposition. The positive effect of mixture richness on decomposition did not disappear, but was much
less marked, when considering mixture with slow-decomposing species only. Although the main driver of decomposition in a mixture
is still the average decomposability of the component species (itself largely determined by litter quality), the species interactions
in a mixture add a consistent source of variability that is worth considering when predicting the decomposability of a given
mixture. We showed that a greater positive difference between observed decomposition rates and that expected from its component
species alone was found in mixtures with higher mean nitrogen content and a higher heterogeneity in non-labile compounds.
Our results offer quantitative proof that litter chemical heterogeneity, as well as the mean quality of the mixture, can affect
the decomposability in litter mixtures. 相似文献