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1. Plant quality (bottom‐up effects) and natural enemies (top‐down effects) affect herbivore performance. Furthermore, plant quality can also influence the impact of natural enemies. 2. Lower plant quality through reduced irrigation increased the abundance of the cryptic species from the Bemisia tabaci complex [hereafter B. tabaci Middle East Asia Minor 1 (MEAM1)], but not its natural enemies on cotton. It was therefore predicted that lower plant quality would diminish the impact of natural enemies in regulating this herbivore. 3. Over three cotton seasons, plant quality was manipulated via differential irrigation and natural enemy abundance with insecticides. Life tables were used to evaluate the impact of these factors on mortality of immature B. tabaci (MEAM1) over nine generations. 4. Mortality of B. tabaci (MEAM1) was consistently affected by natural enemies but not by plant quality. This pattern was driven by high levels of sucking predation, which was the primary (key) factor associated with changes in immature mortality across all irrigation and natural enemy treatments. Dislodgement (chewing predation and weather) and parasitism contributed as key factors in some cases. Analyses also showed that elimination of sucking predation and dislodgement would have the greatest effect on overall mortality. 5. The top‐down effects of natural enemies had dominant effects on populations of B. tabaci (MEAM1) relative to the bottom‐up effects of plant quality. Effects were primarily due to native generalist arthropod predators and not more host‐specific aphelinid parasitoids. The findings of this study demonstrate the important role of arthropod predators in population suppression and validate the importance of conservation biological control in this system for effective pest control.  相似文献   
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Bonferroni adjusted F-tables are given for α=0.10 and α = 0.001 with degrees of freedom following classical tables of Fisher and Yates. The tables may be used in simultaneous analysis of variances or in evaluating binomial tests by means of F-tables in configural frequency testing.  相似文献   
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Age-specific life tables of two important pests of cowpea, Vigna unguiculata (L.) Walp., the pod sucking bugs Clavigralla tomentosicollis Stål and C. shadabi Dolling (Heteroptera: Coreidae), were obtained from observations carried out at different temperatures. A biophysical model was found satisfactory to describe the temperature-response of developmental and mortality rates of egg and nymphal stages, with a peak developmental rate around 34°C in both species. The variability in development times was small and the experimental data did not permit any conclusion with regard to the Erlang probability density function. Survival of eggs and nymphs remained high between 20° and 30°C for both species. At temperatures above 34°C, C. tomentosicollis survivorship and fecundity was higher than that of C. shadabi, which in turn laid more eggs at temperatures between 20° and 30°C. Maximum fecundity is estimated to be at 29°C for C. tomentosicollis (99 eggs/female) and 26°C for C. shadabi (261 eggs/female). At 30°C, the intrinsic rate of increase reached a maximum in both species, 0.152 per day for C. tomentosicollis and 0.145 per day for C. shadabi, and remained high for C. tomentosicollis until 36°C. C. tomentosicollis performed significantly better on pigeonpea, Cajanus cajan Millsp., than on cowpea at higher temperatures.  相似文献   
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We discuss Bayesian log-linear models for incomplete contingency tables with both missing and interval censored cells, with the aim of obtaining reliable population size estimates. We also discuss use of external information on the censoring probability, which may substantially reduce uncertainty. We show in simulation that information on lower bounds and external information can each improve the mean squared error of population size estimates, even when the external information is not completely accurate. We conclude with an original example on estimation of prevalence of multiple sclerosis in the metropolitan area of Rome, where five out of six lists have interval censored counts. External information comes from mortality rates of multiple sclerosis patients.  相似文献   
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Factors affecting the distribution and numbers of the neotropical mud-wasps Zeta abdominale (Drury) in Jamaica and Z. canaliculatum (Oliv.) in Trinidad are discussed. Rainfall was a limiting factor in both aspects of the ecology of the two species. In Jamaica, Z. abdominale was virtually absent from rainfall zones >2540 mm m.a.p. (mean annual precipitation), whereas in Trinidad, Z. canaliculatum hardly inhabited those localities of > 2250 mm m.a.p. Furthermore, the local populations were progressively smaller and more scattered in wetter areas, because consistent rainfall and overcast conditions may result in reduced nesting activity. However, in a favourable locality, numbers may be temporarily increased after rainfall which boosts food supply (caterpillars).
Developmental mortality, at 57.68% and 57.2896 respectively was remarkably similar in Z. abdominale and Z. canaliculatum . The important predators within the cells were Melittobia sp. ( hawaiiensis complex) (Eulophidae) and Amobia fioridensis Townsend (Miltogramminae). In Zeta abdominale total developmental mortality was positively correlated with log,0 (no. of cells) at different sites; averaging only 33.3% for small populations, but 77.4% for large ones.
Regulation at low numbers ( Z. abdominale ) was probably achieved by harsh physical factors, causing low fecundity, but great survival in the cells and high emigration rate. Where Z. abdominale was numerous, the physical environment was favourable, but developmental mortality was so high, that it is necessary to postulate the immigration of many nesting females.  相似文献   
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Staniswalis JG 《Biometrics》2008,64(4):1054-1061
SUMMARY: Nonparametric regression models are proposed in the framework of ecological inference for exploratory modeling of disease prevalence rates adjusted for variables, such as age, ethnicity/race, and socio-economic status. Ecological inference is needed when a response variable and covariate are not available at the subject level because only summary statistics are available for the reporting unit, for example, in the form of R x C tables. In this article, only the marginal counts are assumed available in the sample of R x C contingency tables for modeling the joint distribution of counts. A general form for the ecological regression model is proposed, whereby certain covariates are included as a varying coefficient regression model, whereas others are included as a functional linear model. The nonparametric regression curves are modeled as splines fit by penalized weighted least squares. A data-driven selection of the smoothing parameter is proposed using the pointwise maximum squared bias computed from averaging kernels (explained by O'Sullivan, 1986, Statistical Science 1, 502-517). Analytic expressions for bias and variance are provided that could be used to study the rates of convergence of the estimators. Instead, this article focuses on demonstrating the utility of the estimators in a study of disparity in health outcomes by ethnicity/race.  相似文献   
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In this paper the analysis of several proportions in a comparative study setting is discussed. The case of ordinal grouping variates is considered. F statistics are formulated to test for trend in the proportions over the scored values of the determinant variate. The null chi-square or F (t square) functions are presented separately for the unstratified and stratified analysis, and in either situation the corresponding functions with angular transformed proportions are also expressed. Generalizations to deal with the parameters in the nonnull range are outlined. Throughout, the intimate relation between the presented statistics and standard methods is pointed out.  相似文献   
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