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   23073篇
  免费   1282篇
各国政治   895篇
工人农民   1000篇
世界政治   1562篇
外交国际关系   727篇
法律   15887篇
中国共产党   2篇
中国政治   143篇
政治理论   4013篇
综合类   126篇
  2021年   115篇
  2020年   480篇
  2019年   521篇
  2018年   660篇
  2017年   699篇
  2016年   786篇
  2015年   576篇
  2014年   647篇
  2013年   2338篇
  2012年   608篇
  2011年   654篇
  2010年   652篇
  2009年   672篇
  2008年   655篇
  2007年   676篇
  2006年   689篇
  2005年   561篇
  2004年   575篇
  2003年   521篇
  2002年   535篇
  2001年   890篇
  2000年   808篇
  1999年   645篇
  1998年   309篇
  1997年   231篇
  1996年   263篇
  1995年   246篇
  1994年   231篇
  1993年   230篇
  1992年   426篇
  1991年   433篇
  1990年   402篇
  1989年   401篇
  1988年   415篇
  1987年   383篇
  1986年   430篇
  1985年   432篇
  1984年   341篇
  1983年   339篇
  1982年   258篇
  1981年   234篇
  1980年   200篇
  1979年   294篇
  1978年   176篇
  1977年   146篇
  1976年   125篇
  1975年   130篇
  1974年   176篇
  1973年   134篇
  1971年   111篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
The stepping-stone theory of progression into drug use is examined, based on the alcohol and other drug use of over 27,000 seventh-through eighth-grade students in New York State. The data show that students do not use illicit drugs unless they also use alcohol. White, black and Hispanic students all tend to initiate the use of drugs in the following order-alcohol, marijuana, pills, and hard drugs. Among blacks and Hispanics, pills are not as important a transition between marijuana and hard drugs as they are among whites. Cigarettes form an important step between alcohol and marijuana use for younger students, particularly for females. Since alcohol serves as the gateway to all other drug use, prevention approaches that control and limit alcohol use among adolescents may be warranted.He received his Ph. D. in Psychology for the State University of New York at Buffalo in 1976. His research interests are the social and psychological correlates of drinking.She received her Ph.D. in Sociology from the State University of New York at Buffalo in 1983.  相似文献   
942.
The premise that effects of maturational timing are mediated by social context is explored by comparing adolescent girls in dance and nondance schools. Because the dance student must maintain a relatively low body weight, being a late maturer (who is often leaner than an on-time maturer) is expected to be more advantageous to the dancer than to the student not required to meet a weight standard. Girls aged 14 to 18 were seen; 276 attended private schools and 69 attended national ballet company schools. AllSs were weighed and measured and asked questions about their secondary sexual development, weight-related concerns, eating concerns, adult sex-role expectancies, body image, emotional functioning, and family relationships. Menarcheal age was used to classify girls as early (before 11.5 years of age), on time (between 11.5 and 14 years), and late maturers (after 14 years). More dance than non-dance school students were late maturers (55% versus 29%). The dance students weighed less and were leaner, had higher eating scores, and had lower family relationship and impulse control scores than the comparison sample. Across groups, late maturing students weighed less, were leaner, and had lower diet and higher oral control scores than on-time maturers, with the differences more pronounced in the dance than nondance students. In addition, the on-time dancers had higher psychopathology, perfection, and bulimia scores and lower body image scores than the late maturing dancers. The findings are discussed in terms of a goodness of fit between the requirements of a social context and a person's physical and behavioral characteristics.This paper was prepared with the support of grants from the W. T. Grant Foundation and the National Institutes of Health.Ph.D. from the University of Pennsylvania. Research Interests: Girls' psychological adaptation to pubertal change, biosocial aspects of female reproductive events, development in at-risk children and adolescents.  相似文献   
943.
This study examined the influence of pubertal timing upon family interactions in normal and psychiatric adolescent samples. An important feature of our approach is its emphasis upon micro-analysis of family behaviors (individual speeches) and family processes (theoretically specified speech pairings). Rather than assume that global family patterns (e.g., power) shift in response to pubertal changes, we follow how types of speeches and speech sequences are associated with different pubertal timing. Using the previously constructed family coding system, the Constrainig and Enabling Coding System, we found that on-time adolescents and their parents differed from both off-time groups (early or late). These results are discussed in terms of current implications and suggestions for future research.An earlier version of this paper was presented at the SRCD Study Group on Timing of Maturation, October, 1983, at the Education Testing Service, Princeton, NJ. This research was supported by NICHD Grant 1 R01 HD18684-01, and an NIMH Research Scientist Award (Dr. Hauser).Received his Ph.D. from Harvard University. Research interest is adolescent development within the family and impact of chronic illness on adolescent development and family interaction.Received her B.A. from Wellesley College. Research interests are in humor and attractiveness.Received his M.A. from Boston University. Research interests are in methodology and statistics.Received Ed.D. from Harvard University. Research interests are in adolescent development within the family, and family coping with stress.Received M.D. from University of Chicago. Research interests are in psychosocial aspects of diabetes.Received Ed.D. from Harvard University. Research interests are in developmental psychopathology, and moral and ego development.Received Ph.D. from Ohio State University. Research interests are in assessment of ego development and family systems.Received Ph.D. from University of Miami. Research interests are in family studies and adolescent development.  相似文献   
944.
945.
946.
Sixty-eight college students listed the factors they consider or would consider when making the following commitments: choosing courses, choosing a major, choosing a career, choosing a friend, choosing a romantic partner, and choosing a lifelong partner. In addition, subjects provided their own definition ofcommitment in an unstructured essay. Subjects listed more factors, more distinct types of factors, and more original factors for interpersonal commitments than for academic/vocational commitments. There were few gender differences found in these measures, contradicting the idea that men and women think differently about different commitments. In addition, few gender or class year differences were found in the themes present in the essay definingcommitment. Conceptions of commitment, as described in essays, predicted thinking about specific commitments only slightly.Received Ph.D. in Psychology and M.S.E. in Computer Science from the University of Pennsylvania, and has research interests in the areas of cognitive development and reasoning and decision making.Received Ph.D. in Counseling and Guidance from the University of Wisconsin, Madison, and has research interests in adolescent development and adolescent psychopathology.  相似文献   
947.
In an attempt to delay hatching without affecting their viability, the eggs ofLatheticus oryzae W. were subjected to cold treatment at 5° for varying periods and at different stages of their development. A small dose of 0.5 krad of gamma radiation was also given at each of those temperature treatments. Most of the eggs hatched at 30° following low-temperature exposures of 1 and 2 days. There was a significant decrease in hatch as the exposure period increased further (P<0.05). An egg exposure to 5° also led to an increase in egg period and the increase was nearly equal to the period of cold exposure. Radiation did not alter the situation.
Zusammenfassung Kühllagerung ist eine der gebr?uchlichsten Methoden für die Aufbewahrung von Insekteneiern. Um die optimalen Bedingungen für eine Vorratshaltung zu bestimmen, wurden 0–1 d alte Eier vonL. oryzae Temperaturen von 5° w?hrend 1–7 d ausgesetzt, nachdem sie verschieden lange bei 30° gehalten waren. Eine kleine Dosis von 0.5 krad Gammabestrahlung wurde bei jeder Temperaturbehandlung ebenfalls gegeben. Alle Eiproben wurden nach den verschiedenen K?ltebehandlungen in 30° zurückgebracht und die Wirkung auf Schlüpfprozentsatz und Eidauer bestimmt. Die Eidauer nahm zu, wenn die Eier bei 5° gehalten wurden, was anzeigt, da? die Embryogenese bei 5° unterdrückt wurde. Die Lebensf?higkeit der Eier wurde nicht beeintr?chtigt bei einer 5°-Einwirkungsdauer von 2 d, nahm aber bei weiterer Verl?ngerung der Expositionsdauer ab. Nur etwa 37% der Eier schlüpften (44,1% der Kontrolleier) nach 7-t?giger K?ltebehandlung. Bestrahlung beeinflu?te weder das Schlüpfen noch die Entwicklungsdauer.
  相似文献   
948.
In 1982, disabled workers who came on the social security disability insurance rolls from mid-1980 to mid-1981 had median monthly incomes of less than $500 if they were unmarried and less than $1,300 if they were married. These median monthly income levels, which include the income of a spouse and minor children if present, are roughly half those of the noninstitutionalized population aged 25-64. Social security benefits are the most important source of income for disabled workers and their families: They account for 40 percent of the total family income of married disabled workers and 65 percent of the total income of unmarried disabled workers. Social security benefits provide at least half of all income for more than 80 percent of unmarried disabled-worker beneficiaries and for 50 percent of the married beneficiaries. For married disabled-worker beneficiaries, earnings of the spouse are the second most important income source. Spousal earnings account for 28 percent of total income. Pensions and asset income each account for about 10 percent of total income for these married beneficiaries. Earnings are not an important source of income for unmarried disabled-worker beneficiaries for whom they amount to only about 3 percent of total income. Pensions, asset income, and public transfers each account for about 10 percent of total income of the unmarried beneficiaries.  相似文献   
949.
950.
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