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101.
Informal urban settlements determine the wellbeing of a large section of global humanity. Yet there has been little research on their role in facilitating social mobility. In theory such settlements may foster human progress by linking rural–urban migrants to the services, contacts and livelihoods concentrated in cities. The article uses longitudinal data for South Africa to explore the magnitude of social progression among people living within informal settlements compared with rural areas and formal urban areas. It finds that there may be some advantage from living in an informal settlement compared with a rural area, but the effect is not strong. The impact may be larger in the more prosperous Gauteng city‐region than in other urban regions. 相似文献
102.
Much previous work on the relationship between respondent's reported frequency of discussion with spouse about family planning and correctness of reporting spouse's approval of family planning has led to the conclusion that discussion promotes approval. In this paper, data from the 1998 Kenya Demographic and Health Surveys are used to show that a focus on the relationship between frequency of discussion and correctness of reporting partner's disapproval of family planning leads to sceptical conclusions about the effects of discussion in improving knowledge of partner's attitude or in promoting approval. 相似文献
103.
104.
模糊车辆路径问题的一种混合遗传算法 总被引:9,自引:1,他引:9
在对模糊车辆路径问题进行简单描述的基础上,通过引入决策者主观偏好值的概念,给出了解决该问题的基本思路,建立了具有模糊特征的车辆路径问题的模糊机会规划模型,提出了求解该问题的一种基于模糊模拟的混合遗传算法。同时,在最小化总行驶距离的目标下,通过随机模拟方法研究了决策者主观偏好值的选择对最终决策目标的影响作用,并给出了其最佳取值范围。 相似文献
105.
106.
107.
108.
证券市场流动性与交易者群体变动的混沌研究 总被引:1,自引:2,他引:1
从证券市场微观结构角度,利用交易者群体可变的动态模型,分别在确定与不确定性金
融环境下,研究离散交易状态下市场的形成过程,并分析了交易者群体变动的混沌条件. 结果
表明,市场流动性的最低标准是买卖双方的交易者群体要有一个恰当的比例,市场达到稳定流
动性的时间与描述离开股市交易者的参数有关,通过交易制度对交易者群体参数的影响,可实
现对市场过程的控制,最后给出仿真计算. 相似文献
109.
Mlonte Carlo Techniques for Quantitative Uncertainty Analysis in Public Health Risk Assessments 总被引:2,自引:0,他引:2
Most public health risk assessments assume and combine a series of average, conservative, and worst-case values to derive a conservative point estimate of risk. This procedure has major limitations. This paper demonstrates a new methodology for extended uncertainty analyses in public health risk assessments using Monte Carlo techniques. The extended method begins as do some conventional methods--with the preparation of a spreadsheet to estimate exposure and risk. This method, however, continues by modeling key inputs as random variables described by probability density functions (PDFs). Overall, the technique provides a quantitative way to estimate the probability distributions for exposure and health risks within the validity of the model used. As an example, this paper presents a simplified case study for children playing in soils contaminated with benzene and benzo(a)pyrene (BaP). 相似文献
110.
Health Risk Assessment of a Modern Municipal Waste Incinerator 总被引:2,自引:0,他引:2
Boudet Céline Zmirou Denis Laffond Mauricette Balducci Franck Benoit-Guyod Jean-Louis 《Risk analysis》1999,19(6):1215-1222
During the modernization of the municipal waste incinerator (MWI, maximum capacity of 180,000 tons per year) of Metropolitan Grenoble (405,000 inhabitants), in France, a risk assessment was conducted, based on four tracer pollutants: two volatile organic compounds (benzene and 1, 1, 1 trichloroethane) and two heavy metals (nickel and cadmium, measured in particles). A Gaussian plume dispersion model, applied to maximum emissions measured at the MWI stacks, was used to estimate the distribution of these pollutants in the atmosphere throughout the metropolitan area. A random sample telephone survey (570 subjects) gathered data on time-activity patterns, according to demographic characteristics of the population. Life-long exposure was assessed as a time-weighted average of ambient air concentrations. Inhalation alone was considered because, in the Grenoble urban setting, other routes of exposure are not likely. A Monte Carlo simulation was used to describe probability distributions of exposures and risks. The median of the life-long personal exposures distribution to MWI benzene was 3.2·10–5 g/m3 (20th and 80th percentiles = 1.5·10–5 and 6.5·10–5 g/m3), yielding a 2.6·10–10 carcinogenic risk (1.2·10–10–5.4·10–10). For nickel, the corresponding life-time exposure and cancer risk were 1.8·10–4 g/m3 (0.9.10–4 – 3.6·10–4 g/m3) and 8.6·10–8 (4.3·10–8–17.3·10–8); for cadmium they were respectively 8.3·10–6 g/m3 (4.0·10–6–17.6·10–6) and 1.5·10–8 (7.2·10–9–3.1·10–8). Inhalation exposure to cadmium emitted by the MWI represented less than 1% of the WHO Air Quality Guideline (5 ng/m3), while there was a margin of exposure of more than 109 between the NOAEL (150 ppm) and exposure estimates to trichloroethane. Neither dioxins nor mercury, a volatile metal, were measured. This could lessen the attributable life-long risks estimated. The minute (VOCs and cadmium) to moderate (nickel) exposure and risk estimates are in accord with other studies on modern MWIs meeting recent emission regulations, however. 相似文献