全文获取类型
收费全文 | 7527篇 |
免费 | 180篇 |
国内免费 | 1篇 |
专业分类
管理学 | 1066篇 |
民族学 | 44篇 |
人口学 | 645篇 |
丛书文集 | 22篇 |
理论方法论 | 633篇 |
综合类 | 70篇 |
社会学 | 3227篇 |
统计学 | 2001篇 |
出版年
2023年 | 44篇 |
2021年 | 49篇 |
2020年 | 108篇 |
2019年 | 172篇 |
2018年 | 187篇 |
2017年 | 275篇 |
2016年 | 193篇 |
2015年 | 126篇 |
2014年 | 200篇 |
2013年 | 1437篇 |
2012年 | 225篇 |
2011年 | 229篇 |
2010年 | 172篇 |
2009年 | 182篇 |
2008年 | 193篇 |
2007年 | 175篇 |
2006年 | 192篇 |
2005年 | 177篇 |
2004年 | 153篇 |
2003年 | 135篇 |
2002年 | 165篇 |
2001年 | 200篇 |
2000年 | 199篇 |
1999年 | 183篇 |
1998年 | 135篇 |
1997年 | 123篇 |
1996年 | 104篇 |
1995年 | 92篇 |
1994年 | 138篇 |
1993年 | 97篇 |
1992年 | 124篇 |
1991年 | 128篇 |
1990年 | 115篇 |
1989年 | 102篇 |
1988年 | 88篇 |
1987年 | 89篇 |
1986年 | 90篇 |
1985年 | 88篇 |
1984年 | 92篇 |
1983年 | 68篇 |
1982年 | 70篇 |
1981年 | 48篇 |
1980年 | 59篇 |
1979年 | 62篇 |
1978年 | 48篇 |
1977年 | 48篇 |
1976年 | 38篇 |
1975年 | 47篇 |
1974年 | 40篇 |
1971年 | 25篇 |
排序方式: 共有7708条查询结果,搜索用时 750 毫秒
891.
Fei-Huang Chang Hong-Bin Chen Frank K. Hwang 《Journal of Combinatorial Optimization》2014,27(3):567-573
A partition of a set of n points in d-dimensional space into p parts is called an (almost) separable partition if the convex hulls formed by the parts are (almost) pairwise disjoint. These two partition classes are the most encountered ones in clustering and other partition problems for high-dimensional points and their usefulness depends critically on the issue whether their numbers are small. The problem of bounding separable partitions has been well studied in the literature (Alon and Onn in Discrete Appl. Math. 91:39–51, 1999; Barnes et al. in Math. Program. 54:69–86, 1992; Harding in Proc. Edinb. Math. Soc. 15:285–289, 1967; Hwang et al. in SIAM J. Optim. 10:70–81, 1999; Hwang and Rothblum in J. Comb. Optim. 21:423–433, 2011a). In this paper, we prove that for d≤2 or p≤2, the maximum number of almost separable partitions is equal to the maximum number of separable partitions. 相似文献
892.
Let k be a positive integer and G=(V,E) be a graph. A vertex subset D of a graph G is called a perfect k-dominating set of G, if every vertex v of G, not in D, is adjacent to exactly k vertices of D. The minimum cardinality of a perfect k-dominating set of G is the perfect k-domination number γ kp (G). In this paper, we give characterizations of graphs for which γ kp (G)=γ(G)+k?2 and prove that the perfect k-domination problem is NP-complete even when restricted to bipartite graphs and chordal graphs. Also, by using dynamic programming techniques, we obtain an algorithm to determine the perfect k-domination number of trees. 相似文献
893.
The need to integrate adaptation efforts into land-use planning policies has been only recently recognized in Ho Chi Minh City. The city's latest planning guidance addresses both flooding resilience and mitigation of urban heat. This paper outlines the development contexts and the current barriers for adapted land-use planning within the city. The key challenge for land-use planning is communicating the important functions and services of open and natural urban spaces and effectively guiding the mainly individual developer-driven development. As the realization of non-structural adaptation measures is in strong contrast to the current market-driven private and short-term developer interests, the main development trajectories are questioned and synergies identified. 相似文献
894.
895.
896.
ABSTRACT The distribution of the cross-correlations of squared residuals from Box-Jenkins models is considered in very general conditions, and the asymptotic distribution is derived. A test for a lagged relationship in volatility for economic time series under instantaneous causality is proposed, and its empirical behaviour is studied. An example involving the international stock market's volatility is studied, and an interesting result is observed. 相似文献
897.
K. A. Froeschl 《Statistics and Computing》1996,6(1):11-29
Concerning the task of integrating census and survey data from different sources as it is carried out by supranational statistical agencies, a formal metadata approach is investigated which supports data integration and table processing simultaneously. To this end, a metadata model is devised such that statistical query processing is accomplished by means of symbolic reasoning on machine-readable, operative metadata. As in databases, statistical queries are stated as formal expressions specifying declaratively what the intended output is; the operations necessary to retrieve appropriate available source data and to aggregate source data into the requested macrodata are derived mechanically. Using simple mathematics, this paper focuses particularly on the metadata model devised to harmonize semantically related data sources as well as the table model providing the principal data structure of the proposed system. Only an outline of the general design of a statistical information system based on the proposed metadata model is given and the state of development is summarized briefly. 相似文献
898.
M. Pithuncharurnlap K.E. Basford W.T. Federer 《Australian & New Zealand Journal of Statistics》1993,35(3):263-270
In field experiments involving a large number of experimental plots, a neighbour analysis can be used to control environmental variation by estimating the trend within blocks. The effect of interplot competition is another important source of variation which has an influence on the estimation of treatment contrasts. To reduce the effect of the variation from these sources and to improve the precision of comparison between treatments, a spatial model is proposed for incorporating both trend effect and interplot competition. It is a modification to the residual maximum likelihood neighbour analysis of Gleeson & Cullis (1987) using the two neighbouring treatment effects to estimate interplot competition. A real example is used to illustrate this methodology. The results indicate that the extended model gives no appreciable difference in standard error of mean differences compared with the model taking into account the trend effect only. However, the rankings of estimated treatment means do differ. More research using both real and simulated data is required before such models that incorporate trend and competition effects can be confidently recommended. 相似文献
899.
900.
Brener Nancy D.; Eaton Danice K.; Kann Laura; Grunbaum Jo Anne; Gross Lori A.; Kyle Tonja M.; Ross James G. 《Public opinion quarterly》2006,70(3):354-374
This study examined whether the prevalence of self-reportedhealth risk behaviors among high school students varied by surveysetting (school versus home) and mode of administration (paperand pencil versus computer). Students in grades 9 and 11 wereassigned randomly to one of four conditionsschool paper-and-pencilinstrument (PAPI), school computer-assisted self-interview (CASI),home PAPI, and home CASI. During the spring of 2004, 4,506 studentscompleted identically worded questionnaires based on the YouthRisk Behavior Survey questionnaire. Logistic regression analysescontrolling for sex, grade, and race/ethnicity revealed thatsetting was associated significantly with the reporting of 30of the 55 risk behaviors examined, and mode was associated significantlywith the reporting of 7 of the 55 behaviors. For all behaviorswith a significant setting main effect, the odds of reportingthe behavior were greater among students who completed questionnairesat school than among students who completed questionnaires athome. For all behaviors with a significant mode main effect,PAPI mode students had lower odds of reporting the behaviorthan CASI mode students. Because social measurement researchassumes that higher prevalence estimates are more valid thanlower estimates, methodological factors shown to increase estimates,such as setting and mode, should be considered when planningsurveys. 相似文献