全文获取类型
收费全文 | 407篇 |
免费 | 41篇 |
国内免费 | 1篇 |
出版年
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 11篇 |
2016年 | 11篇 |
2015年 | 12篇 |
2014年 | 10篇 |
2013年 | 18篇 |
2012年 | 19篇 |
2011年 | 31篇 |
2010年 | 8篇 |
2009年 | 12篇 |
2008年 | 21篇 |
2007年 | 21篇 |
2006年 | 12篇 |
2005年 | 13篇 |
2004年 | 11篇 |
2003年 | 15篇 |
2002年 | 15篇 |
2001年 | 14篇 |
2000年 | 7篇 |
1999年 | 14篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 12篇 |
1988年 | 4篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1982年 | 5篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1967年 | 3篇 |
1965年 | 3篇 |
1962年 | 2篇 |
1959年 | 3篇 |
1951年 | 2篇 |
排序方式: 共有449条查询结果,搜索用时 187 毫秒
61.
Raised fasting blood lactate levels were observed in diabetic patients on phenformin in therapeutic dosage. After an intravenous glucose load this effect was exaggerated and the lactate/pyruvate ratio increased. Withdrawal of the drug led to normal blood lactate levels and a fall in the lactate/pyruvate ratio. 相似文献
62.
63.
Lyle G. Whyte Luc Bourbonni re Claude Bellerose Charles W. Greer 《Bioremediation Journal》1999,3(1):69-80
The bioremediation potential of hydrocarbon-contaminated soils from the most northerly inhabited station in the world, Canadian Forces Station - Alert, was assessed. Microbial enumeration, by both viable plate counts and direct counts, combined with molecular analysis (polymerase chain reaction and colony hybridization) for hydrocarbon catabolic genes (alkB, ndoB, xylE), demonstrated the presence of significant numbers of cold-adapted hydrocarbon-degrading microorganisms. The degradative activity of these populations was assessed by mineralization of 14Clabeled hexadecane (C16) at 5°C in untreated and treated soils. Although very low rates of C16 mineralization were observed in the untreated soils, nutrient supplementation with a fertilizer markedly increased C16 mineralization. Highly active cold-adapted hydrocarbon-degrading consortia were prepared from soil slurries, and their degradative potentials were monitored by biomass measurements and mineralization activity. Bio augmentation of the contaminated soils with consortia containing the greatest percentages of degradative bacteria resulted in the shortest C16 mineralization acclimation period. However, treatment with the consortia plus fertilizer did not appreciably increase C16 mineralization or reduce total petroleum hydrocarbon concentrations to a greater extent than did the fertilizer treatment alone. These results indicate that the soils possessed sufficient numbers of cold-adapted degradative bacteria, and that fertilizer application alone was sufficient to obtain elevated levels of degradative activity at low ambient summer temperatures. 相似文献
64.
Monitoring on the Lowveld reaches of the Olifants River, Limpopo River System, and its Steelpoort, Blyde, Klaserie and Selati tributaries was initiated in 2009. Analysis of the 2009–2015 data from four Olifants River sites showed deterioration in the river’s ecological condition between where it enters the Lowveld and where it enters the Kruger National Park, with a slight recovery within the Kruger National Park. Physico-chemical, aquatic macroinvertebrate and fish data collected in 2009–2015 at six sites on the Steelpoort, Blyde, Klaserie and Selati tributaries of the Olifants River corroborated the ecological condition of these tributaries. The Selati was the most polluted and was in a critically modified condition, whereas the Klaserie and Steelpoort were in fair condition and the Blyde was in good condition. The Selati appeared to have a significant negative impact on the water quality, macroinvertebrates and fish of the Olifants River within the Kruger National Park. 相似文献
65.
JR Sara SM Marr WJ Smit LJC Erasmus WJ Luus-Powell 《African Journal of Aquatic Science》2017,42(3):287-291
Muscle tissue from 63 Synodontis zambezensis collected bimonthly in 2013 at Flag Boshielo Dam were analysed for metals and metalloids in a desktop human health risk assessment. The Hazard Quotient, based on a weekly meal of 67 g of fish muscle, exceeded the maximum acceptable level of one for lead, cobalt, cadmium, mercury, arsenic and selenium. The concentrations of these elements were higher in 2013 than those recorded in 2009 and 2012 in other fish species from Flag Boshielo Dam and these may pose a long-term health risk if consumed regularly by impoverished rural communities reliant on fish as a source of protein. 相似文献
66.
A combination of allozyme and mitochondrial DNA markers were used to determine the contribution of recent and ancient causes
of patterns of genetic variation within and among 46 populations of the endangered golden sun moth, Synemon plana. Allozyme analysis grouped the 46 populations into 5 major genetic clusters that corresponded closely with geographic location
following a classic isolation-by-distance model. Phylogenetic analysis of 14 mtDNA haplotypes revealed two reciprocally monophyletic
groups. One of these groups (containing 4 geographically distant populations) was clearly identified by allozyme analysis
and represents a distinct evolutionary unit. The remaining 4 allozyme groups were not distinguishable by mtDNA analysis. The
evidence suggests that the populations within these groups derived from a small founding population that underwent rapid demographic
expansion in ancient times. This was followed by more recent population bottlenecks resulting from habitat fragmentation associated
with the widespread introduction of agriculture into the region. The generally low levels of allozyme and nucleotide diversity
within these populations support this hypothesis.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
67.
Ana Whyte Luis V. Monteagudo Angel Díaz-Otero M. Eugenia Lebrero M. Teresa Tejedor M. Victoria Falceto Jaime Whyte Margarita Gallego 《Animal reproduction science》2009,115(1-4):328-333
Persistence of the Müllerian duct syndrome (PMDS) is a rare form of pseudohermaphroditism characterized by the presence of uterus and oviducts in otherwise normally differentiated SRY-positive 78 XY canine males. Undescended testicles are also common. We report a case of a male PMDS dog with a uterus and bilateral cryptorchidism. The dog had an incomplete regression of the mesonephric tubules. As a consequence of this an abnormally enlarged head of the epididymis was observed. In addition, an extreme reduction in size of both the body and the tail was found. Microscopic examination of both testicles revealed bilateral hyperplasia of Leydig cells. The progesterone blood level was measured by ELISA and was found to be abnormally high (3.18 ng/ml) compared to that of normal male dogs (lower than 1 ng/ml). Three months after surgical removal of the internal genitalia, the serum progesterone, testosterone and oestradiol levels were normal for a castrated male dog. 相似文献
68.
69.
Wilson M O'Hanlon R Prasad S Deighan A Macmillan P Oxborough D Godfrey R Smith G Maceira A Sharma S George K Whyte G 《Journal of applied physiology (Bethesda, Md. : 1985)》2011,110(6):1622-1626
This study examined the cardiac structure and function of a unique cohort of documented lifelong, competitive endurance veteran athletes (>50 yr). Twelve lifelong veteran male endurance athletes [mean ± SD (range) age: 56 ± 6 yr (50-67)], 20 age-matched veteran controls [60 ± 5 yr; (52-69)], and 17 younger male endurance athletes [31 ± 5 yr (26-40)] without significant comorbidities underwent cardiac magnetic resonance (CMR) imaging to assess cardiac morphology and function, as well as CMR imaging with late gadolinium enhancement (LGE) to assess myocardial fibrosis. Lifelong veteran athletes had smaller left (LV) and right ventricular (RV) end-diastolic and end-systolic volumes (P < 0.05), but maintained LV and RV systolic function compared with young athletes. However, veteran athletes had a significantly larger absolute and indexed LV and RV end-diastolic and systolic volumes, intraventricular septum thickness during diastole, posterior wall thickness during diastole, and LV and RV stroke volumes (P < 0.05), together with significantly reduced LV and RV ejection fractions (P < 0.05), compared with veteran controls. In six (50%) of the veteran athletes, LGE of CMR indicated the presence of myocardial fibrosis (4 veteran athletes with LGE of nonspecific cause, 1 probable previous myocarditis, and 1 probable previous silent myocardial infarction). There was no LGE in the age-matched veteran controls or young athletes. The prevalence of LGE in veteran athletes was not associated with age, height, weight, or body surface area (P > 0.05), but was significantly associated with the number of years spent training (P < 0.001), number of competitive marathons (P < 0.001), and ultraendurance (>50 miles) marathons (P < 0.007) completed. An unexpectedly high prevalence of myocardial fibrosis (50%) was observed in healthy, asymptomatic, lifelong veteran male athletes, compared with zero cases in age-matched veteran controls and young athletes. These data suggest a link between lifelong endurance exercise and myocardial fibrosis that requires further investigation. 相似文献
70.
The soluble hydrolases of the mammalian lysosome are marked for delivery to this organelle by the addition of mannose 6-phosphate to their N-glycans. Two related mannose 6-phosphate receptors (MPRs) recognize this feature in the trans Golgi network (TGN) and deliver the hydrolases to the late endosome. In contrast, the vacuolar hydrolases of the yeast Saccharomyces cerevisiae do not contain 6-phosphate monoesters on their N-glycans, and the only sorting receptor so far identified in this organism is the product of the VPS10 gene. This protein also cycles between the Golgi and the late endosome, but is unrelated to the vertebrate MPRs, and recognizes a specific amino acid sequence of carboxypeptidase Y (CPY). This has led to the notion that although yeast and mammals share many components in Golgi to endosome traffic, they use unrelated receptor systems to sort their abundant soluble hydrolases. In this paper, we report that the yeast genome does in fact contain an uncharacterized ORF (YPR079w) that encodes a membrane protein that is distantly related to mammalian MPRs. The protein encoded by this gene (which we term MRL1) cycles through the late endosome. Moreover, there is a strong synergistic effect on the maturation of proteinases A and B when both MRL1 and VPS10 are deleted, which suggests that Mrl1p may serve as a sorting receptor in the delivery of vacuolar hydrolases. 相似文献