首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   93768篇
  免费   1969篇
  国内免费   4篇
管理学   12722篇
民族学   554篇
人才学   25篇
人口学   7333篇
丛书文集   540篇
教育普及   2篇
理论方法论   9559篇
现状及发展   1篇
综合类   2190篇
社会学   43784篇
统计学   19031篇
  2023年   513篇
  2021年   571篇
  2020年   1522篇
  2019年   2208篇
  2018年   2134篇
  2017年   3215篇
  2016年   2432篇
  2015年   2069篇
  2014年   2649篇
  2013年   18950篇
  2012年   2469篇
  2011年   2318篇
  2010年   2024篇
  2009年   2211篇
  2008年   2084篇
  2007年   1916篇
  2006年   2150篇
  2005年   2335篇
  2004年   2205篇
  2003年   1951篇
  2002年   2031篇
  2001年   2106篇
  2000年   1895篇
  1999年   1765篇
  1998年   1532篇
  1997年   1406篇
  1996年   1355篇
  1995年   1369篇
  1994年   1337篇
  1993年   1340篇
  1992年   1336篇
  1991年   1273篇
  1990年   1248篇
  1989年   1095篇
  1988年   1185篇
  1987年   1048篇
  1986年   958篇
  1985年   1119篇
  1984年   1182篇
  1983年   1070篇
  1982年   985篇
  1981年   886篇
  1980年   834篇
  1979年   911篇
  1978年   798篇
  1977年   716篇
  1976年   671篇
  1975年   650篇
  1974年   543篇
  1973年   459篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
851.
Past studies have found equivocal support for the ability of young infants to discriminate infant‐directed (ID) speech information in the presence of auditory‐only versus auditory + visual displays (faces + voices). Generally, younger infants appear to have more difficulty discriminating a change in the vocal properties of ID speech when they are accompanied by faces. Forty 4‐month‐old infants were tested using either an infant‐controlled habituation procedure (Experiment 1) or a fixed‐trial habituation procedure (Experiment 2). The prediction was that the infant‐controlled habituation procedure would be a more sensitive measure of infant attention to complex displays. The results indicated that 4‐month‐old infants discriminated voice changes in dynamic face + voice displays depending on the order in which they were viewed during the infant‐controlled habituation procedure. In contrast, no evidence of discrimination was found in the fixed‐trial procedure. The findings suggest that the selection of experimental methodology plays a significant role in the empirical observations of infant perceptual abilities.  相似文献   
852.
853.
854.
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   
855.
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   
856.
The purpose of the article is to provide an overview of the law regulating combat in order to assist in determining whether casualties inflicted in combat should be classified as victims of war or victims of war crimes. The boundaries and the content of International Humanitarian Law are indicated. A brief statement of the law regulating combat is given. The concepts of military objective and of proportionality are analyzed. The scope of an unlawful attack is addressed as is the relationship between unlawful attack offences and other offences in International Humanitarian Law. The article concludes with a discussion of when combat casualties are war crimes victims.  相似文献   
857.
858.
With the increasing pressure on social and health care resources,professionals have to be more explicit in their decision makingregarding the long-term care of older people. This groundedtheory study used 19 focus groups and nine semi-structured interviews(99 staff in total) to explore professional perspectives onthis decision making. Focus group participants and intervieweescomprised care managers, social workers, consultant geriatricians,general medical practitioners, community nurses, home care managers,occupational therapists and hospital discharge support staff.The emerging themes spanned context, clients, families and services.Decisions were often prompted by a crisis, hindering professionalsseeking to make a measured assessment. Fear of burglary andassault, and the willingness and availability of family to helpwere major factors in decisions about living at home. Serviceavailability in terms of public funding for community care,the availability of home care workers and workload pressureson primary care services influenced decision ‘thresholds’regarding admission to institutional care. Assessment toolsdesigned to assist decision making about the long-term careof older people need to take into account the critical aspectsof individual fears and motivation, family support and the availabilityof publicly funded services as well as functional and medicalneeds.  相似文献   
859.
21世纪各个国家特别是亚洲各国进入了发展的新阶段。亚洲在经济发展中实现了建设性的双边伙伴关系。但是亚洲国家形成“与西方传统不同的亚洲国际关系模式”仍然任重道远。作者认为,亚洲共同的文化认同可以发挥重要作用,理应把亚洲国家特别是两个人口最多的国家中国和印度团结起来,全面实现“亚洲共同体”的战略目标。  相似文献   
860.
This article overviews prevention and early intervention approaches focusing specifically on their relevance to the health of children and young people in Australia. Australian public health has a sound track record although concealed within the aggregate profile are a number of sub-populations with poorer health indicators. Recognition of this has increased efforts to improve the health of children and young people especially in exploring the impact of social environments within the communities where children are raised. This paper examines emerging research in this area drawing out key lessons and learning from Australian experience in the field of early intervention and prevention in community settings.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号