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   19943篇
  免费   759篇
各国政治   1111篇
工人农民   730篇
世界政治   1368篇
外交国际关系   774篇
法律   12698篇
中国共产党   7篇
中国政治   126篇
政治理论   3781篇
综合类   107篇
  2020年   300篇
  2019年   362篇
  2018年   494篇
  2017年   521篇
  2016年   542篇
  2015年   429篇
  2014年   447篇
  2013年   2086篇
  2012年   465篇
  2011年   497篇
  2010年   501篇
  2009年   544篇
  2008年   549篇
  2007年   578篇
  2006年   585篇
  2005年   452篇
  2004年   492篇
  2003年   450篇
  2002年   404篇
  2001年   823篇
  2000年   698篇
  1999年   584篇
  1998年   272篇
  1997年   216篇
  1996年   189篇
  1995年   191篇
  1994年   207篇
  1993年   182篇
  1992年   362篇
  1991年   410篇
  1990年   378篇
  1989年   376篇
  1988年   355篇
  1987年   397篇
  1986年   354篇
  1985年   339篇
  1984年   301篇
  1983年   297篇
  1982年   214篇
  1981年   222篇
  1980年   150篇
  1979年   286篇
  1978年   188篇
  1977年   146篇
  1976年   128篇
  1975年   154篇
  1974年   169篇
  1973年   182篇
  1972年   133篇
  1971年   123篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
An unusual case of driving under the influence of the volatile anaesthetic enflurane is reported. A markedly affected anaesthetist was sniffing at an enflurane-moistened handkerchief before he crashed into a lorry at a red traffic light. In the blood sample enflurane (2.92 mg/l) as well as diclofenac (0.28 mg/l) and 4-aminophenazone (24.4 mg/l) were found. The way of driving and the accident and the deficiency symptoms could be explained by the central suppressing effects of enflurane. The physician was considered as impaired and not suitable to drive at the time of the incidence.  相似文献   
992.
Time-of-flight mass spectrometry (TOF-MS) offers new perspectives for forensic toxicology. Qualitative and quantitative analyses of a mixture of three selected benzodiazepines (diazepam, nordazepam and bromazepam) were used to compare gas chromatography (GC-TOF-MS, quadrupole GC-MS, GC-ECD) and liquid chromatography (HPLC-DAD) data. Method validation parameters like LOD, LOQ, S/N-ratios reflect the capabilities of GC-TOF-MS. Five-point calibrations for bromazepam in human peripheral blood (50, 100, 160, 200, 300 ng/ml) using medazepam as internal standard (1000 ng/ml) were performed. The calibrations using GC-TOF-MS (using the fragments of m/z 236 and 288), GC-ECD (dual system) and HPLC-DAD (at 235 nm) all showed correlation coefficients close or superior to 0.99. Quadrupole GC-MS data was not used in the comparison of extracted samples due to the low sensitivity in the full scan mode. Two analyses of real cases concerning bromazepam are presented. In the first case, the presence or absence of bromazepam could not be established with both HPLC-DAD and GC-ECD due to background signals. The extracted ion chromatograms and spectrum traces after the analysis with the GC-TOF-MS could clearly excluded the presence of bromazepam. The second case illustrates the quantitation of bromazepam, where both HPLC-DAD and GC-ECD were unable to give satisfactory results, again due to interfering background signals. The analyses performed on the GC-TOF-MS-system demonstrated high sensitivity and also high selectivity due to the high quality of mass spectra obtained. The advantages of GC-TOF-MS make it a promising analytical technique for forensic toxicology.  相似文献   
993.
The aim of the present investigation was to reconstruct the chronological age based on the dental developmental stages of third molars evaluated on orthopantomograms. A total of 1175 orthopantomograms were assembled from patients of Caucasian origin between 16 and 22 years of age. Each third molar present was scored by two observers according to a 10-stage developmental scale. The kappa statistics measured the intra- and inter-observer reliability. The general statistical analysis was based on multiple regression analysis in order to obtain multiple regression formulas for dental age estimation based on the number of third molars present on the evaluated orthopantomogram. No regression models were statistically significant when there was only one-third molar present because of the relatively small number of orthopantomograms that fitted this criterion. A strong agreement was found between the intra- and inter-observer measurements. The statistical analysis revealed both for males and females high Pearson correlation coefficients between contralateral third molars and smaller coefficients between antimeres. The obtained multiple regression formulas are only applicable in certain specified conditions, for instance when four third molars are present the following formulas should be used in a Caucasian male "age=10.2000+0.5122UL+0.5273LL" (developmental stage of upper and lower left third molars) or in case of a female "age=13.6206+0.1933UR+0.5080LR" (developmental stage of upper and lower right third molars). This investigation revealed that the chronological age of a Caucasian individual may be estimated based on regression formulas with a S.D. of 1.52 or 1.56 years for males and females, respectively, when all four third molars are present.  相似文献   
994.
Polymorphism at 15 microsatellite loci was studied in four predominant, endogamous populations of Maharashtra state in India. The studied population included Marathas, Desasth Brahmins, Chitpavan Brahmins and Dhangars; all of whom belong to Marathi speaking linguistic group of India. The distribution of the allele pattern at 13 tetranucleotide repeat and two pentanucleotide repeat of Powerplex 16 System portrays that these markers are highly polymorphic and thus, informative in human identification and understanding diversity in the addressed populations.  相似文献   
995.
Although microsatellite diversity in autosomal chromosomes has been extensively described for many of the Indian populations, there is still a lacuna left on information about the genetic diversity of tribal populations. This paper reports the genetic data on the three tribal populations belonging to the Austroloid ethnic group from Orissa (Juang, Paroja and Saora). The 15 STR (D3S1358, THO1, D21S11, D18S51, PentaE, D5S818, D13S317, D7S820, D16S539, CSF1PO, PentaD, vWA, D8S1179, TPOX, FGA) polymorphism would help to accentuate the STR database for better understanding of population genetics and forensic applications. The microsatellites included in the system are found to be highly polymorphic, with the combined power of exclusion being greater than 0.999, in all the three investigated populations.  相似文献   
996.
The purpose of this research was to examine gender and body mass, as factors linked to perceived experiences within the peer appearance culture. The sample included 215 girls and 200 boys who were either in 7th grade or 10th grade. Students provided self-reports on experiences in three domains: appearance culture among friends (appearance conversations and diet/muscle talk), peer evaluations (peer appearance pressure, appearance teasing, and vicarious peer teasing), and peer acceptance concerns (appearance-based acceptance, peer appearance comparison). The results indicated that although girls reported more appearance conversations, boys perceived more appearance pressure and teasing. Boys also admitted that they talked with friends about muscle building at a rate greater than girls talked about dieting. BMI showed distinct gender patterns. BMI was a key attribute that unified the experiences within the appearance culture for overweight girls. Among the boys, BMI was associated with differentiated experiences for underweight and overweight participants.Associate Professor in Educational Psychology at the University of Washington. She is a developmental psychologist specializing in the contributions of peers to body image and social-emotional well-being during adolescence. Research interests include body image during adolescence and gender differences.Doctoral student at the University of Washington in Human Development and Cognition. Her research focuses on the social-emotional development of adolescents, academic and appearance social comparisons, and issues related to gender and science. Research interests include body image during adolescence, gender differences, social comparison, and academic competence.  相似文献   
997.
This study examined the ability of future certainty—an individual's perception of future stability, operationalized as the likelihood of certain life outcomes–to explain variance in delinquency and school adjustment, while controlling for economic, neighborhood, and family factors, among a cross-sectional sample of 1422 male and 1562 female African American adolescents drawn from the National Longitudinal Study of Adolescent Health (Add Health). Three kinds of future certainty were examined: future life certainty (e.g., life expectancy), marriage certainty, and college certainty. In hierarchical multiple regression analyses, future certainty and family functioning were stronger predictors than economic and neighborhood variables: neighborhood disorganization and family socioeconomic status. Future life certainty and expectations of attending college were stronger predictors of delinquency among males than females. Marriage certainty was the weakest predictor of the three certainty variables.  相似文献   
998.
Peer and media influences have been identified as important conveyors of socio-cultural ideals in adolescent and preadolescent samples. This study aims to explore peer and media influences in the body image concerns and dieting awareness of younger girls, aged 5–8 years. A sample of 128 girls was recruited from the first 4 years of formal schooling. Individual interviews were conducted to assess the aspects of body image, as well as dieting awareness by means of a brief scenario. A number of sources of peer and media influence were examined. It was found that by 6 years of age, a large number of girls desired a thinner ideal figure. Both peer and media influences emerged as significant predictors of body image and dieting awareness. Specifically, girls’ perceptions of their peers’ body dissatisfaction predicted their own level of body dissatisfaction and dieting awareness. Watching music television shows and reading appearance-focused magazines predicted dieting awareness. In particular, girls who looked at magazines aimed at adult women had greater dissatisfaction with their appearance. Thus, the present study highlights that girls aged 5–8 years of age are already living in an appearance culture in which both peers and the media influence body image and dieting awareness.Hayley Dohnt, B. Psych. (Hons.), is completing her Ph.D. in Clinical Psychology at Flinders University. Her major research interests are in the area of child psychology and the development of body image.Marika Tiggemann’s Professor of Psychology at Flinders University. Her major research interest is in media influences on body image. She is Associate Editor for the journal Body Image.  相似文献   
999.
The role of interpersonal sensitivity in the relation between romantic stress and depression was examined in 55 adolescent girls from an inner-city high school. Depression, interpersonal sensitivity, and chronic and episodic romantic stress were measured at two time points, 6 months apart. Interpersonal sensitivity was found to moderate the longitudinal relation between romantic stress (both chronic and episodic) and depression. In contrast, interpersonal sensitivity did not potentiate depressive responses to non-romantic interpersonal stress, suggesting particular importance of stress in the romantic domain for adolescent girls. Results indicate that girls' sensitivities to romantic relationship stress should be specifically addressed in depression prevention and intervention programs.Received her PhD from the University of Southern California. Research interests include the influence of romantic relationship factors, such as romantic stress and dating violence, on the development of depression during adolescence.Received her PhD from the University of California, Los Angeles. Research interests include the interplay between adolescent depression, personality disorder symptoms, and interpersonal variables including adjustment in friendships and romantic relationships.Research interests include cognitive and interpersonal factors in adolescent depression.  相似文献   
1000.
This study examined the factors associated with resistance to peer pressure toward antisocial behaviors among a sample of Mexican-origin adolescents (n=564) living in a large Southwestern city in the U.S. A model examining the influence of generational status, emotional autonomy from parents, and self-esteem on resistance to peer pressure was tested independently for boys and girls. Gender differences emerged in the factors that influenced resistance to peer pressure. Results indicated that resistance to peer pressure was influenced by generational status and emotional autonomy from parents for both boys and girls. However, self-esteem was found to influence resistance to peer pressure only for boys.Mayra Y. Bámaca is a graduate student in Family and Human Development at Arizona State University. Her research interests include adolescent development among ethnically diverse populations, the influence of contextual factors in development, parenting adolescents, and resiliency among Latino adolescents and their families. This work was based on the master’s thesis of the first author.Adriana J. Uma?a-Taylor received her Ph.D. from the University of Missouri-Columbia and is currently an Assistant Professor of Family and Human Development at Arizona State University. Her research interests include ethnic identity formation during adolescence and resilience among Latino adolescents and their families.This study was supported, in part, by a grant to the second author from the Fahs Beck Fund for Research and Experimentation of the New York Community Trust.  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