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981.
Summary MultiGaussian models have the intrinsic property of imposing very little continuity to extreme values. If the variable that
is being modeled is hydraulic conductivity and the processes being studied are groundwater flow and mass transport, the absence
of continuous paths of extreme values will have a retardation effect in the computed travel times. In the case of radionuclide
release of nuclear waste from a deep geological repository, underestimation of travel times may lead to unsafe decision making.
To demonstrate the impact of the low continuity of extreme value implicit to multiGaussian modes, travel times are computed
in a site similar to Finnsj?n-one of the sites in crystaline rock studied in Sweden-using two stochastic models with the same
histogram and covariance, one of them is multiGaussian, and the other is not and displays high connectivity of extreme high
values. The results show that the multiGaussian model leads to less conservative results than the non-multiGaussian one. Invoking
the parisimony principle to select a multiGaussian model as the simplest model that can be fully described by a mean value
and a covariance function should not be justification enough for such selection. If there is not enough data to characterize
the connectivity of the extreme values and therefore distriminate whether a multiGaussian model is appropriate or not, less
parismonious models must also be considered. 相似文献
982.
A limiting constraint of many management science techniques is that inputs from the decision maker based upon his experiences, opinions and intuition are not considered. For those models that do allow this type of input, it is assumed that they can be accurately and precisely defined in a subjective probability distribution. Little attention, however, has been directed towards evaluating the techniques to define these distributions in a management setting. This study investigates the relative merits of four of the most commonly used techniques for the quantification of subjective assessments. When these techniques were used with professionals whose jobs entail evaluation of uncertainty, a clear preference was shown. Additionally, some concluding observations concerning the selection and the application of assessment techniques are presented. 相似文献
983.
984.
The relationship between the infestation rate of carambola fruits byBactrocera carambolae Drew and Hancock was investigated in a carambola orchard. Phenology of the fruits was found to influence percentage infestation
of fruits byB. carambolae. The proportion of unbagged or susceptible fruits infested varied with time of year and tended to decrease with the increase
of unbagged fruits available on the tree. The number of ovipunctures per fruit varied with fruit size and was also found to
be indicative of the number of adult insects (B. carambolae and parasitoids) that will emerge from each fruit. Higher number of susceptible fruits available on each tree also decreased
both the number of ovipunctures per fruit and the number of eggs laid per fruit, which could possibly be due to the strategy
of spreading the risk adopted by the femaleB. carambolae or a result of random selection with more hosts available. The main parasitoids recorded wereBiosteres vandenboschi (Fullaway) andB. arisanus (Sonan). The mean percentage of parasitism was 38.3% and it followed roughly that of infestation of fruits. 相似文献
985.
This article provides an introduction to the use of Confirmatory Factor Analysis to test measurement invariance and stability in longitudinal research. The approach is illustrated through examples representing: (a) one construct, two measurement waves; (b) one construct, three waves; (c) two constructs, two waves; and (d) comparison of treatment and control groups in pre-post designs. Basic issues in establishing measurement invariance over time, across treatment groups, and within measurement waves are discussed. Estimates of the stability coefficients that are corrected for measurement error and method variance associated with each specific measured variable are provided. Establishing measurement invariance is a critical requirement for making inferences about treatment effects and changes in constructs over time. 相似文献
986.
A. G. Watts 《The Career development quarterly》1996,45(1):41-53
A revolution in the structures of work is taking place in most advanced industrialized countries. This article suggests that giving new meanings to the concept of “career” is one of the keys to economic success and social harmony in the new postindustrial society. It argues that a number of new social ligatures are needed to make the new concept of career accessible to all. One of these ligatures is lifelong access to career counseling. This article outlines a strategy developed in the United Kingdom for achieving such access and analyzes its cautious application of market and quasi-market principles to career counseling provision. 相似文献
987.
988.
The literature on professional development suggests that the process of segmentation or specialization within a profession logically accompanies the aggregation, dissemination and application of new and expanding bodies of knowledge. The present study empirically examines the extent and dimensions of this process of segmentation within the family therapy movement by comparing the belief and action systems of 1000 experienced family therapists oriented to one of three major models of family therapy. Two theses are suggested which may explain the findings depicting a unique patterning of similarities and differences among the three models; each implying different directives and implications for the continued growth of the interdisciplinary practice of family therapy. 相似文献
989.
A study is made of the effects of associated causes of death, and of dependency among causes of death, by observing the relative importance of one cause of death when another is eliminated under various competing risk models. Two disease pairs, cancer and infectious disease and stroke and ischemic heart disease, are selected for analysis because they represent different types of disease dependence. Crude probabilities of death for each disease are calculated for the U.S. white male population in 1969. Next, the effects of the complementary disease in a pair are hypothetically eliminated in one of three ways: (a) a standard competing risk adjustment for cause elimination when deaths are singly caused (Chiang, 1968), (b) lethal defect-pattern of failure computations for multiply caused death when no causal order is inferred (Manton et al., 1976), and (c) relative susceptibility, computations for multiply caused deaths when causes are ordered (Wong, 1977). The paper closes with a discussion of the relative merits of the three types of adjustments. 相似文献
990.