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901.
DDT, DDE, and DDD have been detected at elevated concentrations in sediments and fish of the Yakima River, its tributaries and drainages. An assessment was conducted to evaluate the public health significance of eating fish from the river. This was accomplished by establishing a daily intake level of DDT for the population of greatest concern, and comparing this level to a tolerable daily intake. The most sensitive and highly exposed group was determined to be breastfeeding infants. Infant daily intakes of DDT, based on estimated mother's DDT-breast milk levels, were compared to a recommended tolerable daily intake. Results indicate that mothers who frequently consume Yakima River bottom-feeding fish could have breast milk DDT concentrations sufficiently high to expose their infants to levels above the tolerable daily intake. 相似文献
902.
Received: August 14, 2000; revised version: April 23, 2001 相似文献
903.
904.
Objective. Smoking and obesity are associated with significant wage penalties when considered separately. We assess the combined effects of those behaviors. Methods. We estimate the effects of smoking and obesity on wages using multivariate regression analysis with 1979 National Longitudinal Survey of Youth data. Results. The raw data indicate that obese smokers experience large earnings penalties. However, these penalties are not found to be interactive or directly causal for most of the demographic subgroups we examine. One exception is the wage penalty associated with obesity for females, which remains significant throughout the analysis. Conclusions. In the absence of a demonstrable direct causal effect of those behaviors on wages, associated individual‐specific socioeconomic factors appear to be the driving forces behind the obese smoker wage penalty. Not included, but potentially significant, are the effects of employer and customer discrimination against obese smokers and the possible labor policy implications of such discrimination. 相似文献
905.
A Markov Chain Monte Carlo version of the genetic algorithm Differential Evolution: easy Bayesian computing for real parameter spaces 总被引:2,自引:0,他引:2
Cajo J. F. Ter Braak 《Statistics and Computing》2006,16(3):239-249
Differential Evolution (DE) is a simple genetic algorithm for numerical optimization in real parameter spaces. In a statistical
context one would not just want the optimum but also its uncertainty. The uncertainty distribution can be obtained by a Bayesian
analysis (after specifying prior and likelihood) using Markov Chain Monte Carlo (MCMC) simulation. This paper integrates the
essential ideas of DE and MCMC, resulting in Differential Evolution Markov Chain (DE-MC). DE-MC is a population MCMC algorithm,
in which multiple chains are run in parallel. DE-MC solves an important problem in MCMC, namely that of choosing an appropriate
scale and orientation for the jumping distribution. In DE-MC the jumps are simply a fixed multiple of the differences of two
random parameter vectors that are currently in the population. The selection process of DE-MC works via the usual Metropolis
ratio which defines the probability with which a proposal is accepted. In tests with known uncertainty distributions, the
efficiency of DE-MC with respect to random walk Metropolis with optimal multivariate Normal jumps ranged from 68% for small
population sizes to 100% for large population sizes and even to 500% for the 97.5% point of a variable from a 50-dimensional
Student distribution. Two Bayesian examples illustrate the potential of DE-MC in practice. DE-MC is shown to facilitate multidimensional
updates in a multi-chain “Metropolis-within-Gibbs” sampling approach. The advantage of DE-MC over conventional MCMC are simplicity,
speed of calculation and convergence, even for nearly collinear parameters and multimodal densities. 相似文献
906.
Jorge Olguín & Tom Fearn 《Journal of the Royal Statistical Society. Series C, Applied statistics》1997,46(4):449-462
The visual inspection of a half-normal plot is a popular procedure for interpreting data from unreplicated factorial experiments. As this technique is somewhat subjective, the plot should preferably be supplemented with a more formal procedure. However, despite the improvements proposed by Zahn, the formal method using the half-normal plot suggested by Daniel seems to be rarely used. We investigate this procedure by using simulations and real data and suggest a modification to improve its acceptability. We also present corrected critical values for a procedure proposed by Lenth which was found to be miscalibrated. 相似文献
907.
Emerging trends in US retailing 总被引:4,自引:0,他引:4
This article examines the trends shaping the retail environment as we enter the next century. A modified delphi approach was used to access managerial perceptions of the changing retail landscape. Changes in consumer markets, price and branding strategy, store formats, retail institutions and applications of technology were derived from the analysis. From this, a series of managerial considerations are proposed to focus retail managers on developing new strategies to position themselves effectively in the new global marketplace. 相似文献
908.
909.
James F. Hamill 《Symbolic Interaction》1985,8(1):85-102
Because thought processes underlie all human action and can distinguish one culture from another, the social sciences must face the problem of determining how people think. Reasoning can be viewed as abstract and not connected to any particular human activity, as it is in philosophical logic, or it can be seen as a process in a particular linguistic, social and cultural setting, as it is in ethno-logic. Recently anthropologists, developmental psychologists and other scholars working under the general rubric of cognitive science have studied issues in ethno-logic but these studies are flawed because the researchers accepted philosophical logic as the norm under which they judged the actions of their subjects. Good theory in ethno-logic can only come from study which describes thought processes from the natives point of view. One such theory states that conclusions are logically established on the semantic structure of the argument. This theory accounts for both universal and culture specific aspects of reasoning, is testable, opens new areas of research and provides researchers with a firmly grounded method for using meaning to account for behavior. 相似文献
910.
C. Haydee Mas James F. Alexander Cole Barton 《Journal of marital and family therapy》1985,11(4):411-415
Twenty-two two-parent families with a referred adolescent were seen by 11 male and 11 female trainees in family therapy. Mothers, fathers, adolescents, and therapists were rated for verbal expression in affective, behavioral, and cognitive! attributional modes during the first session. Results clearly point to role and content difference in modes of expression. Of particular importance are differences by role which occured as a function of therapist gender. These differences suggest that therapist gender has an impact on family therapists' and family members' verbalizations in first sessions of family therapy. 相似文献