全文获取类型
收费全文 | 19176篇 |
免费 | 454篇 |
国内免费 | 1篇 |
专业分类
管理学 | 2541篇 |
民族学 | 83篇 |
人才学 | 1篇 |
人口学 | 1767篇 |
丛书文集 | 102篇 |
教育普及 | 2篇 |
理论方法论 | 1756篇 |
综合类 | 410篇 |
社会学 | 9499篇 |
统计学 | 3470篇 |
出版年
2021年 | 98篇 |
2020年 | 277篇 |
2019年 | 350篇 |
2018年 | 400篇 |
2017年 | 589篇 |
2016年 | 445篇 |
2015年 | 335篇 |
2014年 | 401篇 |
2013年 | 3215篇 |
2012年 | 590篇 |
2011年 | 507篇 |
2010年 | 348篇 |
2009年 | 354篇 |
2008年 | 399篇 |
2007年 | 401篇 |
2006年 | 378篇 |
2005年 | 490篇 |
2004年 | 433篇 |
2003年 | 387篇 |
2002年 | 410篇 |
2001年 | 457篇 |
2000年 | 445篇 |
1999年 | 458篇 |
1998年 | 333篇 |
1997年 | 316篇 |
1996年 | 323篇 |
1995年 | 289篇 |
1994年 | 300篇 |
1993年 | 271篇 |
1992年 | 336篇 |
1991年 | 345篇 |
1990年 | 323篇 |
1989年 | 338篇 |
1988年 | 268篇 |
1987年 | 276篇 |
1986年 | 268篇 |
1985年 | 274篇 |
1984年 | 288篇 |
1983年 | 290篇 |
1982年 | 228篇 |
1981年 | 209篇 |
1980年 | 202篇 |
1979年 | 237篇 |
1978年 | 205篇 |
1977年 | 173篇 |
1976年 | 162篇 |
1975年 | 153篇 |
1974年 | 140篇 |
1973年 | 134篇 |
1971年 | 95篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
The mean density of bacteria in a water body is commonly monitored using quantal assay. This paper describes the use of local scoring in estimating the spatial distribution of mean density from quantal assay results at a set of point locations. An application to estimating the mean density of fecal conform bacteria in a coastal pond is presented. Model diagnostics based on a parametric bootstrap are also presented. 相似文献
182.
The 1995 wave of the Add Health study is used to investigate the relative influence of parent gender and residence on patterns of parental involvement with adolescents. Adolescent reports (N =17,330) of shared activities, shared communication, and relationship quality with both biological parents are utilized. A multidimensional scaling analysis reveals that parent gender explains most of the variance in parent‐adolescent involvement, with residential status playing a secondary yet a fundamental role in accounting for these patterns. Resident mothers who do not live with adolescents’ biological fathers engage in the broadest range of activities with their children. Unpartnered resident fathers display patterns of parenting that are as similar to mothers as they are to other fathers. 相似文献
183.
184.
Are the decisions of American policymakers informed by generaltrends in the publics ideology or by the publicspolicy-specific preferences? In this article we discuss twoexplanations for the types of public opinion information thatpoliticians collect and use. Using a unique data set of privatepolls from the White House of Richard Nixon, we find that whenopinion data on specific policies were available, the presidentrelied on them and not on general ideology data. On less importantissues, however, we find that the president often chose notto collect policy-specific data and instead relied on generalideology data. The differential collection and use of informationby policymakers reflect varying strategic calculations. Theyalso have profound implications for representative democracyand the demands placed on citizens and governors. 相似文献
185.
In this article we posit that racial discrimination is not uniform across the U.S. labor market. While it is likely that patterns of racial discrimination occur in some types of jobs more than others, little empirical research has examined the effect of race across segmented labor markets. Incorporating two decades of comparable General Social Survey data, this article revisits William J. Wilson's hypothesis that the significance of race in determining labor market outcomes is declining. We examine the effect of race within two dissimilar labor segments over time, dividing the labor market into technique‐versus social‐skills‐oriented segments. Using this theoretically useful dichotomy, we examine if the net effect of race (African American and white men) on occupational prestige has declined from the 1970s to the 1990s. Our multivariate analysis shows that the net effect of race is different in each labor market. This suggests that racial discrimination against African Americans is not uniform across the entire labor market, but instead is differentiately manifested within various labor market segments. Overall, our findings partially support Wilson's thesis indicating that while the effect of race is no longer a significant indicator of occupational prestige by the 1990s in a technique‐oriented job segment, it remains a significant predictive variable within a social‐skills‐oriented job segment, even when controlling for a range of social class and structural variables. 相似文献
186.
Barry R. Chiswick Yew Liang Lee Paul W. Miller 《The International migration review》2006,40(2):419-450
This article is concerned with the determinants of English language proficiency among immigrants in a longitudinal survey for Australia. It focuses on both visa category and variables derived from an economic model of the determinants of destination‐language proficiency among immigrants. Skills‐tested and economic immigrants have the greatest proficiency shortly after immigration, followed by family‐based visa recipients, with refugees having the lowest proficiency. Other variables the same, these differences disappear by 3.5 years after immigration for speaking skills; and although they diminish, they persist longer for reading and writing skills. The variables generated from the model of destination‐language proficiency (such as schooling and age at migration) are, in part, predictions of visa category, but they are more important statistically for explaining proficiency. 相似文献
187.
Walter R. Allen 《Sociological Forum》1995,10(4):569-592
Since 1965 hundreds of articles and books have been published about African American families. Nevertheless, our understanding of these families continues to be limited. There is a tendency to gloss over important within-group differences; thus, monolithic, stereotypic and inaccurance portrayals of Black family life are common. This paper sets aside debates of Black family pathology or viability, focusing instead on these families' essential character. The paper seeks to understand Black families on their own terms, locating them in relevant social, historical, political and cultural contexts. Key empirical patterns and trends reveal dramatic changes in Black family geographic location, headship, quality of life and socioeconomic status since 1950.A complex picture is revealed. There has been gradual but steady overall improvement alongside persistent, extreme racial disparties and pronounced class disparities among Black families. The proposed Black Family Socio-Ecological Context model specifies and connects institutional, interpersonal, environmental, temporal and cultural facts that shape the essential character of Black family life in such a way as to produce characteristics simultaneously shared and idiosyncratic. The model also provides an organized, systematic accounting of research and public policy issues relevant to the study of African American families.An early version co-authored with Richard A. English was presented during the National Council on Family Relations Meetings in Portland, Oregon, October 1980. 相似文献
188.
袁嘉祖 《北京林业大学学报(社会科学版)》2002,(Z1)
该文从中国人口快速增长、经济建设加快、用水量逐年增大 ,加上气候变暖、少雨干旱将持续到 2 0 15年 ,我国北方水生态环境日趋恶化现状 ,说明在丰水区筑坝截流、调丰补歉势在必行 ,完全符合生态经济学发展原则和国际水法 相似文献
189.
Lesa L. Aylward Robert C. Brunet Thomas B. Starr Gaétan Carrier Elizabeth Delzell Hong Cheng Colleen Beall 《Risk analysis》2005,25(4):945-956
Recent studies demonstrating a concentration dependence of elimination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) suggest that previous estimates of exposure for occupationally exposed cohorts may have underestimated actual exposure, resulting in a potential overestimate of the carcinogenic potency of TCDD in humans based on the mortality data for these cohorts. Using a database on U.S. chemical manufacturing workers potentially exposed to TCDD compiled by the National Institute for Occupational Safety and Health (NIOSH), we evaluated the impact of using a concentration- and age-dependent elimination model (CADM) (Aylward et al., 2005) on estimates of serum lipid area under the curve (AUC) for the NIOSH cohort. These data were used previously by Steenland et al. (2001) in combination with a first-order elimination model with an 8.7-year half-life to estimate cumulative serum lipid concentration (equivalent to AUC) for these workers for use in cancer dose-response assessment. Serum lipid TCDD measurements taken in 1988 for a subset of the cohort were combined with the NIOSH job exposure matrix and work histories to estimate dose rates per unit of exposure score. We evaluated the effect of choices in regression model (regression on untransformed vs. ln-transformed data and inclusion of a nonzero regression intercept) as well as the impact of choices of elimination models and parameters on estimated AUCs for the cohort. Central estimates for dose rate parameters derived from the serum-sampled subcohort were applied with the elimination models to time-specific exposure scores for the entire cohort to generate AUC estimates for all cohort members. Use of the CADM resulted in improved model fits to the serum sampling data compared to the first-order models. Dose rates varied by a factor of 50 among different combinations of elimination model, parameter sets, and regression models. Use of a CADM results in increases of up to five-fold in AUC estimates for the more highly exposed members of the cohort compared to estimates obtained using the first-order model with 8.7-year half-life. This degree of variation in the AUC estimates for this cohort would affect substantially the cancer potency estimates derived from the mortality data from this cohort. Such variability and uncertainty in the reconstructed serum lipid AUC estimates for this cohort, depending on elimination model, parameter set, and regression model, have not been described previously and are critical components in evaluating the dose-response data from the occupationally exposed populations. 相似文献
190.
In this article, we describe a straightforward method for solving the probability of at least one malignant cell by time t, and the associated hazard function, in the general (i.e., nonhomogeneous) two-stage Moolgavkar-Venzon-Knudson (MVK) model of cancer. The method consists of solving four coupled ordinary differential equations derived from the Kolmogorov backward equations for this process. The relationship of this method to previously proposed solutions is discussed. 相似文献