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51.
Activation of the aryl hydrocarbon receptor (AHR) can occur in polluted environments, either from smoking-related toxicants or from endogenous ligands. We tested whether acute or chronic exposure to the AHR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) alters the transition to reproductive senescence in female Sprague-Dawley rats. In experiment 1, rats (n = 6 per experimental group) received a single dose of 0 or 10 mug/kg of TCDD orally (p.o.) on Postnatal Day 29. Vaginal cytology was monitored for 1 wk each month until rats were killed at 1 yr of age. The single prepubertal exposure to TCDD hastened the transition to reproductive senescence in female rats and was associated with delayed puberty, abnormal cyclicity, and premature reproductive senescence. In a second experiment, rats were exposed to TCDD chronically through weekly dosing (0, 50, or 200 ng kg(-1) wk(-1) p.o., n = 7 each dose) beginning in utero. Lifelong exposure to these lower doses of TCDD induced a dose- and time-dependent loss of normal cyclicity and significantly hastened the onset of the transition to reproductive senescence (P < 0.05). This premature transition to reproductive senescence was associated with prolonged estrous cycles and, at the highest dose of TCDD, persistent estrus or diestrus. The number and size of ovarian follicles were not altered by TCDD. Diestrous concentrations of LH in rats exposed chronically to TCDD were similar to those in controls, whereas progesterone tended to be elevated at both doses of the dioxin (P < 0.08). Serum FSH was elevated in the group exposed to 50 ng/kg of TCDD (P < 0.02), whereas estradiol was decreased at both doses of dioxin (P < 0.01). Data thus far support endocrine disruption rather than depletion of follicular reserves as a primary mechanism of the premature transition to reproductive senescence following activation of the AHR pathway by TCDD in female rats. 相似文献
52.
53.
Yamaji Y Valdez DM Seki S Yazawa K Urakawa C Jin B Kasai M Kleinhans FW Edashige K 《Cryobiology》2006,53(2):258-267
It has been shown that aquaporin-3, a water channel, is expressed in mouse embryos. This type of aquaporin transports not only water but also neutral solutes, including cell-permeating cryoprotectants. Therefore, the expression of this channel may have significant influence on the survival of cryopreserved embryos. However, permeability coefficients of aquaporin-3 to cryoprotectants have not been determined except for glycerol. In addition, permeability coefficients under concentration gradients are important for developing and improving cryopreservation protocols. In this study, we examined the permeability of aquaporin-3 to various cryoprotectants using Xenopus oocytes. The permeability of aquaporin-3 to cryoprotectants was measured by the volume change of aquaporin-3 cRNA-injected oocytes in modified Barth's solution containing either 10% glycerol, 8% ethylene glycol, 10% propylene glycol, 1.5 M acetamide, or 9.5% DMSO (1.51-1.83 Osm/kg) at 25 degrees C. Permeability coefficients of aquaporin-3 for ethylene glycol and propylene glycol were 33.50 and 31.45 x 10(-3) cm/min, respectively, which were as high as the value for glycerol (36.13 x 10(-3) cm/min). These values were much higher than those for water-injected control oocytes (0.04-0.11 x 10(-3) cm/min). On the other hand, the coefficients for acetamide and DMSO were not well determined because the volume data were poorly fitted by the two parameter model, possibly because of membrane damage. To avoid this, the permeability for these cryoprotectants was measured under a low concentration gradient by suspending oocytes in aqueous solutions containing low concentrations of acetamide or DMSO dissolved in water (0.20 Osm/kg). The coefficient for acetamide (24.60 x 10(-3) cm/min) was as high as the coefficients for glycerol, ethylene glycol, and propylene glycol, and was significantly higher than the value for control (6.50 x 10(-3) cm/min). The value for DMSO (6.33 x 10(-3) cm/min) was relatively low, although higher than the value for control (0.79 x 10(-3) cm/min). This is the first reported observation of DMSO transport by aquaporin-3. 相似文献
54.
M Hoppert M Valdez M Enseleit W Theilmann O Valerius GH Braus C Föst W Liebl 《Systematic and applied microbiology》2012,35(5):279-290
Several closely related strains of the thermophilic bacterium Dictyoglomus have been isolated from various hot springs on the Philippine archipelago. These strains as well as Dictyoglomus thermophilum H-6-12 were analyzed in view of the structure-functional relationships of the cell envelopes. All envelopes of Dictyoglomus strains show several peculiar features that are apparently either unique for the genus or common for other phylogenetically related Thermotogales. The filamentous cells develop pili at the cell poles, guided by large columnar protein assemblies that traverse the periplasm. Filamentous protein complexes span the periplasmic space at the longitudinal sides of the cell. By the end of the exponential growth phase, Dictyoglomus strains form multicellular aggregates ("rotund bodies") inside a compartment surrounded by a single, continuous outer envelope. The formation of these rotund bodies which are also found in some other deeply branching thermophilic phyla (Thermotoga, Thermus) was studied in detail. The transition between unicellular and multicellular lifestyle can be explained by the partial detachment of a protoplast from the outer envelope during cell division. When the outer envelope is partially detached from the protoplast, mechanical forces generated by protoplast elongation may drive cell rearrangement of daughter cells inside the compartment. During the following rounds of cell division, the overall shape of the compartment changes from spindle-like to globular geometry. Analysis of subcellular fractions of Dictyoglomus cells shows that glucan hydrolases are associated with the compartment. This feature is discussed in view of the multicellular life style of Dictyoglomus. 相似文献
55.
Wayllace NZ Valdez HA Merás A Ugalde RA Busi MV Gomez-Casati DF 《Molecular biology reports》2012,39(1):585-591
The metabolic pathways leading to the synthesis of bacterial glycogen involve the action of several enzymes, among which glycogen
synthase (GS) catalyzes the elongation of the α-1,4-glucan. GS from Agrobacterium tumefaciens uses preferentially ADPGlc, although UDPGlc can also be used as glycosyl donor with less efficiency. We present here a continuous
spectrophotometric assay for the determination of GS activity using ADP- or UDPGlc. When ADPGlc was used as the substrate,
the production of ADP is coupled to NADH oxidation via pyruvate kinase (PK) and lactate dehydrogenase (LDH). With UDPGlc as
substrate, UDP was converted to ADP via adenylate kinase and subsequent coupling to PK and LDH reactions. Using this assay,
we determined the kinetic parameters of GS and compared them with those obtained with the classical radiochemical method.
For this purpose, we improved the expression procedure of A. tumefaciens GS using Escherichia coli BL21(DE3)-RIL cells. This assay allows the continuous monitoring of glycosyltransferase activity using ADPGlc or UDPGlc as
sugar-nucleotide donors. 相似文献
56.
María PifarréRicardo Valdez Carlos González-RebelesCarlos Vázquez Marta RomanoFrancisco Galindo 《Applied animal behaviour science》2012,136(1):57-62
The effect of zoo visitors on the behaviour and physiological responses of the Mexican wolf has not been documented but is worthy of investigation since it is a critically endangered native species and most of the population live in zoos. The effect of the number of visitors was assessed in 12 wolves (five males and seven females) in three zoos of central Mexico. Each wolf was observed for a total of 72 h on Saturdays, Sundays, Mondays and Tuesdays (6 h/day) during a three-week period. Scan sampling was used to obtain individual time budgets. A faecal sample was collected on the following morning of each observation day from 10 wolves to determine cortisol level (RIA). A repeated measures analysis of variance revealed that there was an effect of day on the proportion of time lying (P < 0.01), eating (P < 0.01) and in locomotion (P < 0.01). Wolves spent less time lying on Saturdays and Sundays (0.2980 ± 0.012 and 0.3266 ± 0.012, respectively) than on Mondays and Tuesdays (0.3821 ± 0.012 and 0.4075 ± 0.012, respectively), as well as less time eating on weekend days (Saturdays 0.1214 ± 0.015, Sundays 0.0556 ± 0.015) than in the other 2 days (Mondays 0.816 ± 0.015 and Tuesdays 0.0915 ± 0.015). Mean faecal cortisol was 203.7 ng/g of DM and ranged from 113.10 to 314.48 ng/g. There was an effect of day on the faecal cortisol response (P < 0.01) with wolves having higher cortisol response on Sundays (242.50 ng/g ± 8.48) compared to the other 3 days (Saturdays 192.71 ± 8.48, Mondays 170.73 ng/g ± 7.80, Tuesdays 183.82 ng/g ± 8.48). This is the first study that measures faecal cortisol of Mexican wolves. These results indicate that the amount of visitors in zoos influence the behaviour and adrenal activity of these animals which could be undesirable for ex situ conservation efforts of this endangered species. 相似文献
57.
Rodríguez C Rimaux T Fornaguera MJ Vrancken G de Valdez GF De Vuyst L Mozzi F 《Applied microbiology and biotechnology》2012,93(6):2519-2527
Certain lactic acid bacteria, especially heterofermentative strains, are capable to produce mannitol under adequate culture
conditions. In this study, mannitol production by Lactobacillus reuteri CRL 1101 and Lactobacillus fermentum CRL 573 in modified MRS medium containing a mixture of fructose and glucose in a 6.5:1.0 ratio was investigated during batch
fermentations with free pH and constant pH 6.0 and 5.0. Mannitol production and yields were higher under constant pH conditions
compared with fermentations with free pH, the increase being more pronounced in the case of the L. fermentum strain. Maximum mannitol production and yields from fructose for L. reuteri CRL 1101 (122 mM and 75.7 mol%, respectively) and L. fermentum CRL 573 (312 mM and 93.5 mol%, respectively) were found at pH 5.0. Interestingly, depending on the pH conditions, fructose
was used only as an alternative external electron acceptor or as both electron acceptor and energy source in the case of the
L. reuteri strain. In contrast, L. fermentum CRL 573 used fructose both as electron acceptor and carbon source simultaneously, independently of the pH value, which strongly
affected mannitol production by this strain. Studies on the metabolism of these relevant mannitol-producing lactobacilli provide
important knowledge to either produce mannitol to be used as food additive or to produce it in situ during fermented food
production. 相似文献
58.
Hebert EM Saavedra L Taranto MP Mozzi F Magni C Nader ME Font de Valdez G Sesma F Vignolo G Raya RR 《Journal of bacteriology》2012,194(2):538-539
Lactobacillus curvatus is one of the most prevalent lactic acid bacteria found in fermented meat products. Here, we present the draft genome sequence of Lactobacillus curvatus CRL705, a bacteriocin producer strain isolated from an Argentinean artisanal fermented sausage, which consists of 1,833,251 bp (GC content, 41.9%) and two circular plasmids of 12,342 bp (pRC12; GC, 43.9%) and 18,664 bp (pRC18; GC, 34.4%). 相似文献
59.
Normal aging and neurodegenerative diseases both lead to structural and functional alterations in synapses. Comparison of synapses that are generally similar but respond differently to insults could provide the basis for discovering mechanisms that underlie susceptibility or resistance to damage. Here, we analyzed skeletal neuromuscular junctions (NMJs) in 16 mouse muscles to seek such differences. We find that muscles respond in one of three ways to aging. In some, including most limb and trunk muscles, age-related alterations to NMJs are progressive and extensive during the second postnatal year. NMJs in other muscles, such as extraocular muscles, are strikingly resistant to change. A third set of muscles, including several muscles of facial expression and the external anal sphinter, succumb to aging but not until the third postnatal year. We asked whether susceptible and resistant muscles differed in rostrocaudal or proximodistal position, source of innervation, motor unit size, or fiber type composition. Of these factors, muscle innervation by brainstem motor neurons correlated best with resistance to age-related decline. Finally, we compared synaptic alterations in normally aging muscles to those in a mouse model of amyotrophic lateral sclerosis (ALS). Patterns of resistance and susceptibility were strikingly correlated in the two conditions. Moreover, damage to NMJs in aged muscles correlated with altered expression and distribution of CRMP4a and TDP-43, which are both altered in motor neurons affected by ALS. Together, these results reveal novel structural, regional and molecular parallels between aging and ALS. 相似文献
60.
Martínez-Ibarra JA Nogueda-Torres B Meda-Lara RM Monta?ez-Valdez OD Rocha-Chávez G 《Journal of vector ecology》2012,37(1):241-244
A study of the effect of educating four- to six-year-old children in mosquito control was recently conducted in a city in the state of Jalisco, western Mexico. Four neighborhood districts were selected. Children attending one kindergarten in each of two experimental districts were taught mosquito control with a video from the American Mosquito Control Association (AMCA), joined to the use of the AMCA Touch Table Technique. The entomological indices monitored in the study decreased significantly (P<0.05) in houses in the experimental districts, apparently because parents acted on the comments and suggestions of the children and eliminated or monitored containers used as oviposition sites by mosquitoes. Based on these results, combining both techniques for teaching children mosquito control is a potentially useful tool for control efforts in Mexico and other places in Latin America. 相似文献