全文获取类型
收费全文 | 12565篇 |
免费 | 332篇 |
专业分类
管理学 | 1801篇 |
民族学 | 73篇 |
人才学 | 1篇 |
人口学 | 1295篇 |
丛书文集 | 72篇 |
教育普及 | 1篇 |
理论方法论 | 1084篇 |
现状及发展 | 2篇 |
综合类 | 146篇 |
社会学 | 6052篇 |
统计学 | 2370篇 |
出版年
2023年 | 86篇 |
2021年 | 75篇 |
2020年 | 196篇 |
2019年 | 257篇 |
2018年 | 307篇 |
2017年 | 407篇 |
2016年 | 326篇 |
2015年 | 218篇 |
2014年 | 275篇 |
2013年 | 2185篇 |
2012年 | 432篇 |
2011年 | 372篇 |
2010年 | 296篇 |
2009年 | 281篇 |
2008年 | 334篇 |
2007年 | 305篇 |
2006年 | 280篇 |
2005年 | 287篇 |
2004年 | 270篇 |
2003年 | 242篇 |
2002年 | 281篇 |
2001年 | 311篇 |
2000年 | 312篇 |
1999年 | 289篇 |
1998年 | 197篇 |
1997年 | 182篇 |
1996年 | 181篇 |
1995年 | 184篇 |
1994年 | 150篇 |
1993年 | 160篇 |
1992年 | 179篇 |
1991年 | 163篇 |
1990年 | 175篇 |
1989年 | 196篇 |
1988年 | 161篇 |
1987年 | 148篇 |
1986年 | 155篇 |
1985年 | 186篇 |
1984年 | 176篇 |
1983年 | 169篇 |
1982年 | 137篇 |
1981年 | 118篇 |
1980年 | 114篇 |
1979年 | 149篇 |
1978年 | 97篇 |
1977年 | 91篇 |
1976年 | 98篇 |
1975年 | 89篇 |
1974年 | 86篇 |
1973年 | 73篇 |
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
981.
Evaluation of a family-based substance abuse prevention program targeted for the middle school years
A family-based substance abuse prevention program was evaluated which emphasizes family cohesion, school and peer attachment, self-esteem, and attitudes about adolescent use of alcohol and tobacco. The program was implemented in rural communities and targeted families with students entering middle or junior high school. Baseline surveys were conducted with students and parents in four schools and were readministered one year later. Because the program was voluntary, a quasi-experimental design was used to compare participants (29 students and 28 parents) and nonparticipants (268 students and 134 parents). Analyses of covariance indicated that student participants, as compared to nonparticipants, had higher family cohesion, less family fighting, greater school attachment, higher self-esteem, and believed that alcohol should be consumed at an older age at the one year follow-up. There were fewer significant results for parent participants. Strategies for involving parents in prevention programs are discussed. 相似文献
982.
The primary goal of this study is to examine the association between marijuana use and adult depressive symptomatology. The key independent variables examined are age of marijuana initiation, frequency of current marijuana use, the use of other licit and illicit drugs, and whether marijuana was used to cope with problems. The relationships among these variables are assessed using data from the Young Men and Drugs Survey (n = 1,941), a nationally representative sample of men from the 1944-1954 birth cohort. Results show that early marijuana initiation appears to be weakly associated with increased depression in adulthood. This effect, however, is mediated by educational attainment, employment status, marital status, and other drug use, notably alcohol and tobacco use. Adult frequency of marijuana use is not significantly associated with increased depression in adulthood. Finally, marijuana users who use the drug to cope with problems are more depressed than those who do not use to cope with problems. 相似文献
983.
Coohey C 《Child welfare》2000,79(4):373-402
Thirty-five physically abusive fathers were matched with a comparison sample to test multiple systemic explanations for child physical abuse, using an ecological perspective, and to show the relationship between the structure of social ties and the function of those ties. The physically abusive fathers were found to have received significantly fewer emotional and instrumental supports from their friends, in-laws, and other kin than the comparison fathers, and were only weakly linked to members of their social networks--members who might have discouraged the fathers' aggressive impulses or provided additional support to them and to their families. 相似文献
984.
Administrative databases hold the potential to have a significant impact on the development of effective child welfare programs and policies. This article discusses the strengths and weaknesses of administrative databases, issues with their implementation and data analysis, and effective presentation of their data at different levels in child welfare organizations. 相似文献
985.
986.
A Bayesian approach, implemented using Markov Chain Monte Carlo (MCMC) analysis, was applied with a physiologically‐based pharmacokinetic (PBPK) model of methylmercury (MeHg) to evaluate the variability of MeHg exposure in women of childbearing age in the U.S. population. The analysis made use of the newly available National Health and Nutrition Survey (NHANES) blood and hair mercury concentration data for women of age 16–49 years (sample size, 1,582). Bayesian analysis was performed to estimate the population variability in MeHg exposure (daily ingestion rate) implied by the variation in blood and hair concentrations of mercury in the NHANES database. The measured variability in the NHANES blood and hair data represents the result of a process that includes interindividual variation in exposure to MeHg and interindividual variation in the pharmacokinetics (distribution, clearance) of MeHg. The PBPK model includes a number of pharmacokinetic parameters (e.g., tissue volumes, partition coefficients, rate constants for metabolism and elimination) that can vary from individual to individual within the subpopulation of interest. Using MCMC analysis, it was possible to combine prior distributions of the PBPK model parameters with the NHANES blood and hair data, as well as with kinetic data from controlled human exposures to MeHg, to derive posterior distributions that refine the estimates of both the population exposure distribution and the pharmacokinetic parameters. In general, based on the populations surveyed by NHANES, the results of the MCMC analysis indicate that a small fraction, less than 1%, of the U.S. population of women of childbearing age may have mercury exposures greater than the EPA RfD for MeHg of 0.1 μg/kgg/day, and that there are few, if any, exposures greater than the ATSDR MRL of 0.3 μgg/kgg/day. The analysis also indicates that typical exposures may be greater than previously estimated from food consumption surveys, but that the variability in exposure within the population of U.S. women of childbearing age may be less than previously assumed. 相似文献
987.
In this paper we develop a segmentation scheme for digital images based upon an iterative binary coloring technique that takes into account changing behavior of adjacent pixels. The output is a hierarchical structure of images which allows a better understanding of complex images. In particular, we propose two algorithms that should be considered as image preprocessing techniques. 相似文献
988.
A major step in effectively managing radio resources in a cellular network is to design an appropriate scheme for assigning cells to a location area (LA), serviced by a switch, and allocate resources for individual switches. However, this assignment is already proven in the literature to be an NP-hard problem [Merchant A, Sengupta B. Assignment of cells to switches in PCS networks. IEEE/ACM Transactions on Networking 3(5) (1995) 521–6] that requires efficient heuristic search techniques for obtaining real-time solutions. This work presents a state-space search technique, which is a variant of best first search heuristic technique. The algorithm called the block depth first search (BDFS), allocates cells to switches during switch level resource planning. Under various simulated performance criteria, we compare the performance of the proposed technique with other similar procedures in the literature. Our results indicate that the BDFS outperforms the meta-heuristic procedures in terms of both efficiency and quality of solutions. Hence, we conclude that our proposed technique can be effectively used for switch level planning leading to an efficient management of scarce radio resource in cellular networks. 相似文献
989.
In a series of 2 papers, Kang, Du and Tian solved the existence problem for G-decomposition of λ
K
n
when G is any simple graph with 6 vertices and 7 edges, except when G is the graph T=K
4∪K
2. Notice that a T-decomposition can be considered to be a Pairwise Balanced Design in which each block of size 4 has been matched to a block
of size 2. In this paper we remove this exception for all λ≥2. The case when λ=1 is also addressed.
This paper is written in honor of Frank Hwang on the occasion of his 65th birthday. 相似文献
990.
Joseph A Feigo 《Omega》1975,3(6):758-759