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101.
Pinus radiata D. Don (half-sib families 20010 and 20062) and Pinus caribaea var hondurensis (an open-pollinated family) were grown for 49 weeks at seven levels of phosphorus and at CO2 concentrations of either 340 or 660 microliters per liter, to establish if the phosphorus requirements differed between the CO2 concentrations and if mycorrhizal associations were affected. When soil phosphorus availability was low, phosphorus uptake was increased by elevated CO2. This may have been related to changes in mycorrhizal competition. When the phosphorus concentration in the youngest fully expanded needles was above 600 milligrams per kilogram the shoot weight of all pine families was greater at high CO2 due to increases in rates of photosynthesis. More dry weight was partitioned to the stems of P. radiata family 20010 and P. caribaea. At foliar phosphorus concentrations above 1000 milligrams per kilogram (P. radiata) and 700 milligrams per kilogram (P. caribaea), growth did not increase at 340 microliters of CO2 per liter. Soluble sugar levels in the same needles mirrored the growth response, but the starch concentration declined with increasing phosphorus. At 660 microliters of CO2 per liter, shoot weight and soluble sugar concentrations were still increasing up to a foliar P concentration of 1800 milligrams per kilogram for P. radiata and 1600 milligrams per kilogram for P. caribaea. The starch concentrations did not decline. These results indicate that higher foliar phosphorus concentrations are required to realize the maximum growth potential of pines at elevated CO2.  相似文献   
102.
Rogers  G. S.  Payne  L.  Milham  P.  Conroy  J. 《Plant and Soil》1993,155(1):231-234
The influence of increasing atmospheric CO2 on shoot growth, leaf nitrogen and phosphorus concentrations and carbohydrate composition was investigated in cotton and wheat. Shoot dry weight of both species was generally higher at elevated CO2, especially at high rates of available soil N and P. Critical leaf N concentration was reduced but critical P concentration was increased in both species at high CO2.  相似文献   
103.
Background: It is unclear whether mammographic breast density, a strong risk factor for breast cancer, predicts subtypes of breast cancer defined by estrogen receptor (ER) and/or progesterone receptor (PR) expression. Methods: In a nested case–control study, we compared the breast density of 667 controls and 607 breast cancer cases among women of Caucasian, Japanese, and Native Hawaiian ancestry in the Hawaii component of the Multiethnic Cohort Study. A reader blinded to disease status performed computer assisted density assessment on prediagnostic mammograms. Receptor status was obtained from the statewide Hawaii Tumor Registry. Tumors were classified into ER+PR+ (n = 341), ER−PR− (n = 50), ER+PR−/ER−PR+ (n = 64), and unstaged/unknown (n = 152). Mean percent density values were computed for women with more than one mammogram. Polytomous logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) while adjusting for confounders. Results: Mean percent density was significantly greater for ER+PR+ but not for ER−PR− tumors compared to controls after adjusting for age: 37.3%, 28.9% versus 29.4%, respectively. The overall OR per 10% increase in percent density were similar for ER+PR+ and ER+PR−/ER−PR+ tumors: 1.26 (95% CI 1.17–1.36) and 1.23 (95% CI 1.07–1.42), respectively. However, percent density was not found to be a predictor for ER−PR− tumors (OR 1.00, 95% CI 0.84–1.18). The results did not differ by ethnicity, nor by menopausal status, parity, or HRT use. Conclusions: Our findings indicate that within a multiethnic population, women with higher breast density have an increased risk for ER+PR+ but not ER−PR− tumors.  相似文献   
104.
Predation on adult salmon, Salmo salur L., by otters, Lurra lutra (L.), varied seasonally on the R. Dee, Aberdeenshire, Scotland, being highest during the spawning season in winter. Predation is described for some tributaries of the river. Male fish were caught by otters more often than females, and it is suggested that they were most vulnerable during their extensive excursions up and down stream, particularly as they negotiated shallow riffles. Otters appeared to prey upon healthy fish rather than those infested with Saprolegnia sp. but there was no difference in the size, freshwater- or sea-age offish killed by otterscompared with 'kelts' which had died non-violently. At least some of the otters obtained most of their daily food requirements by catching a single salmon per night.
Considerable numbers of adult salmon may be killed by otters during the spawning period but it is suggested that, because most are males, this is unlikely to affect the breeding success of the salmon population. Most predation occurs outside the fishing season and so is unlikely to reduce the numbers of salmon caught by anglers.  相似文献   
105.
106.
Rapid expansion and intensification of agriculture create challenges for the conservation of biodiversity and associated ecosystem services. In Argentina, the total row crop planted area has increased in recent decades with the expansion of soybean cultivation, homogenizing the landscape. In 2003 we started the first long-term, large-scale bird monitoring program in agroecosystems of central Argentina, in portions of the Pampas and Espinal ecoregions. Using data from this program, we evaluated the effect of land use and cover extent on birds between 2003-2012, accounting for imperfect detection probabilities using a Bayesian hierarchical, multi-species and multi-season occupancy model. We tested predictions that species diversity is positively related to habitat heterogeneity, which in intensified agroecosystems is thought to be mediated by food availability; thus the extent of land use and cover is predicted to affect foraging guilds differently. We also infer about ecosystem services provisioning and inform management recommendations for conservation of birds. Overall our results support the predictions. Although many species within each guild responded differently to land use and native forest cover, we identified generalities for most trophic guilds. For example, granivorous gleaners, ground insectivores and omnivores responded negatively to high proportions of soybean, while insectivore gleaners and aerial foragers seemed more tolerant. Habitat heterogeneity would likely benefit most species in an intensified agroecosystem, and can be achieved with a diversity of crops, pastures, and natural areas within the landscape. Although most studied species are insectivores, potentially beneficial for pest control, some guilds such as ground insectivores are poorly represented, suggesting that agricultural intensification reduces ecological functions, which may be recovered through management. Continuation of the bird monitoring program will allow us to continue to inform for conservation of birds in agroecosystems, identify research needed to reduce key uncertainties, and anticipate the effects of changes in agriculture in central Argentina.  相似文献   
107.
Although figures in scientific articles have high information content and concisely communicate many key research findings, they are currently under utilized by literature search and retrieval systems. Many systems ignore figures, and those that do not typically only consider caption text. This study describes and evaluates a fully automated approach for associating figures in the body of a biomedical article with sentences in its abstract. We use supervised methods to learn probabilistic language models, hidden Markov models, and conditional random fields for predicting associations between abstract sentences and figures. Three kinds of evidence are used: text in abstract sentences and figures, relative positions of sentences and figures, and the patterns of sentence/figure associations across an article. Each information source is shown to have predictive value, and models that use all kinds of evidence are more accurate than models that do not. Our most accurate method has an F1-score of 69% on a cross-validation experiment, is competitive with the accuracy of human experts, has significantly better predictive accuracy than state-of-the-art methods and enables users to access figures associated with an abstract sentence with an average of 1.82 fewer mouse clicks. A user evaluation shows that human users find our system beneficial. The system is available at http://FigureItOut.askHERMES.org.  相似文献   
108.
We describe primers and polymerase chain reaction conditions to amplify 21 tetranucleotide microsatellite DNA loci in black bears (Ursus americanus). We tested primers using individuals from two populations, one each in Georgia and Florida. Among individuals from Georgia (n = 29), primer pairs yielded an average of 2.9 alleles (range, one to four) and an average observed heterozygosity (HO) of 0.50 (range, 0.00 to 0.79). Among individuals from Florida (n = 19), primer pairs yielded an average of 5.7 alleles (range, one to 14) and an HO of 0.55 (range, 0.00 to 1.00). A comparison of previously developed markers with individuals from Georgia suggests that bear populations in Georgia and Florida have reduced allelic diversity relative to other populations.  相似文献   
109.
Neuronal nicotinic acetylcholine receptor (AChR) subtypes have been defined pharmacologically, immunologically, and by DNA cloning, but the correlations between these approaches are incomplete. Vertebrate neuronal AChRs that have been isolated are composed of structural subunits and ACh-binding subunits. A single kind of subunit can be used in more than one AChR subtype. Monoclonal antibody (mAb) 35 binds to structural subunits of subtypes of AChRs from both chicken brain and ganglia. By using antisera to a unique sequence of alpha 3 ACh-binding subunits expressed in bacteria, we show that ganglionic AChRs contain alpha 3 ACh-binding subunits, whereas the brain AChR subtype that binds mAb 35 does not. Subunit-specific antisera raised against recombinant proteins should be a valuable approach for identifying the subunit composition of receptors in multigene, multisubunit families.  相似文献   
110.
The brain‐derived neurotrophic factor (BDNF), a neurotrophin fundamental for brain development and function, has previously been implicated in autism. In this study, the levels of BDNF in platelet‐rich plasma were compared between autistic and control children, and the role of two genetic factors that might regulate this neurotrophin and contribute to autism etiology, BDNF and NTRK2, was examined. We found that BDNF levels in autistic children (n = 146) were significantly higher (t = 6.82; P < 0.0001) than in control children (n = 50) and were positively correlated with platelet serotonin distribution (r = 0.22; P = 0.004). Heritability of BDNF was estimated at 30% and therefore candidate genes BDNF and NTRK2 were tested for association with BDNF level distribution in this sample, and with autism in 469 trio families. Genetic association analysis provided no evidence for BDNF or NTRK2 as major determinants of the abnormally increased BDNF levels in autistic children. A significant association with autism was uncovered for six single nucleotide polymorphisms (SNPs) [0.004 (Z(1df) = 2.85) < P < 0.039 (Z(1df) = 2.06)] and multiple haplotypes [5 × 10?4(χ(3df) = 17.77) < P < 0.042 (χ(9df) = 17.450)] in the NTRK2 gene. These results do not withstand correction for multiple comparisons, however, reflect a trend toward association that supports a role of NTRK2 as a susceptibility factor for the disorder. Genetic variation in the BDNF gene had no impact on autism risk. By substantiating the previously observed increase in BDNF levels in autistic children in a larger patient set, and suggesting a genetic association between NTRK2 and autism, this study integrates evidence from multiple levels supporting the hypothesis that alterations in BDNF/tyrosine kinase B (TrkB) signaling contribute to an increased vulnerability to autism.  相似文献   
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