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   20168篇
  免费   662篇
  国内免费   5篇
各国政治   791篇
工人农民   880篇
世界政治   1359篇
外交国际关系   701篇
法律   13006篇
中国共产党   6篇
中国政治   174篇
政治理论   3729篇
综合类   189篇
  2020年   264篇
  2019年   332篇
  2018年   420篇
  2017年   473篇
  2016年   492篇
  2015年   342篇
  2014年   372篇
  2013年   1835篇
  2012年   532篇
  2011年   579篇
  2010年   469篇
  2009年   512篇
  2008年   581篇
  2007年   627篇
  2006年   614篇
  2005年   535篇
  2004年   537篇
  2003年   569篇
  2002年   486篇
  2001年   811篇
  2000年   703篇
  1999年   588篇
  1998年   294篇
  1997年   221篇
  1996年   250篇
  1995年   216篇
  1994年   251篇
  1993年   237篇
  1992年   407篇
  1991年   435篇
  1990年   447篇
  1989年   382篇
  1988年   433篇
  1987年   380篇
  1986年   406篇
  1985年   365篇
  1984年   293篇
  1983年   283篇
  1982年   221篇
  1981年   233篇
  1980年   166篇
  1979年   217篇
  1978年   155篇
  1977年   125篇
  1976年   125篇
  1975年   149篇
  1974年   166篇
  1973年   126篇
  1972年   118篇
  1970年   115篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
771.
Psychological empowerment encompasses several key aspects of youth civic and sociopolitical development. Most research has focused on psychological empowerment’s emotional component, which entails learned hopefulness about one’s own ability to participate in and lead community change efforts. Fewer studies have assessed critical awareness of how social power operates—psychological empowerment’s cognitive component. The confluence of these two components has been termed critical hopefulness. A complex relationship exists between these two components, and previous research has found relatively small proportions of participants reporting both high levels of critical awareness and simultaneously high levels of hopefulness about their ability to exert influence in the sociopolitical domain. The current study of urban high school students in the Northeastern U.S. (n?=?389; 53.5% female) investigates heterogeneity according to these two components of psychological empowerment. Latent class cluster analyses were conducted and seven distinct groups of participants emerged. Students identifying as Hispanic/Latinx were more likely to be classified into a profile group exhibiting critical hopefulness. Differences were observed between psychological empowerment profile groups on self-reported levels of psychological sense of community, civic engagement, and social justice orientation. Furthermore, a larger proportion of this overall sample was classified into groups that exhibited critical hopefulness than in a previous study of adults. These findings provide useful insights for efforts to engage young people in civic life and to promote sociopolitical development.  相似文献   
772.
The performance of the polymorphic marker systems group-specific component (GC), phosphoglucomutase-1 (PGM), alpha-2-HS-glycoprotein (A2HS), haptoglobin (Hp), and erythrocyte acid phosphatase (EAP) was evaluated on control bloodstains. The major factors considered were: sensitivity of the test system; stability of the marker; laboratory economics of each test; and distinguishing power (Dp) of the system. GC was considered to be the most suitable marker for routine screening because of its high stability and Dp, and the sensitivity of the immunoblotting detection method. PGM and A2HS were the next most valuable markers followed by Hp. EAP could only be considered useful when large amounts of relatively fresh bloodstain were available.  相似文献   
773.
This report describes a collaborative study on typing group-specific component (GC), conducted between the Central Research and Support Establishment and the forensic science laboratories of England, Wales and Northern Ireland. A population study (n=114) was performed. Fifty blood donors were selected to provide a distribution, slightly biased from normal, in favour of the GC 1F-1F and GC 1F-1S phenotypes. A protocol was devised for preparing large bloodstains. The strongest GC bands were obtained from the edge of a stain after the blood had been treated with K+/EDTA. Each laboratory received a representative portion of the large bloodstains for GC typing. Five of the eight laboratories correctly grouped all the bloodstains. No errors directly attitributable to the system were recorded in over 800 tests, indicating that GC in bloodstains can be typed reliably using the combination of isoelectric focusing in ultrathin narrow pH interval gels followed by immunofixation and silver staining.  相似文献   
774.
The microscopic pathology of the liver in fatal cocaine intoxication was studied. Data from cases of cocaine intoxication during the years 1981-1986 were collected and analysed. Thirty cases with a negative past history for intravenous drug abuse, and in which the terminal drug testing revealed solely cocaine or its metabolites, were compared with a control group of nineteen people who had died in motor vehicle accidents, with a terminal negative blood alcohol, negative drug screen and no history of drug abuse. A comparison of liver histology was made along with gross anatomical liver weight. These findings are compared to other studies of hepatotoxicity in drug abuse.  相似文献   
775.
Document examiners sometimes eliminate writers on the basis of differences which are given too much weight. This article is an attempt to explain some conditions whereby differences in the writing of one individual are misinterpreted as significant differences, when they are actually caused by conditions which are unknown to the examiner.  相似文献   
776.
Blood ethanol profiles were determined in experiments with healthy volunteers after they had drunk beer. When 330 ml of light beer (1.8% w/v ethanol) was consumed in 5 min by four men and four women, the average peak blood-alcohol concentration (BAC) reached was 8 mg/100 ml (range 2-11). After nine men had drunk 660 ml of beer (3.0% w/v or 3.6% w/v ethanol) in 25 minutes on an empty stomach, the average peak BAC was 32 mg/100 ml (range 26-44) and 37 mg/100 ml (range 23-54) respectively. When the same two beers were consumed by another nine men together with a meal, the peak BAC was 24 mg/100 ml (range 20-29) and 28 mg/100 ml (range 20-39) respectively. The peak BAC occurred earlier when beer was ingested together with food; mean 32 min (range 30-50) compared with 41 min (range 30-70) with an empty stomach. The rate of disappearance of alcohol from blood (beta-slope) was 12 mg/100 ml/h in the fed state and 15 mg/100 ml/h when subjects were fasted. The apparent volume of distribution of ethanol (Vd) was 0.65 l/kg (SD 0.07) for the empty stomach condition but exceeded unity when beer was ingested together with food. It seems that part of the dose of alcohol when consumed with food never reaches the systemic circulation.  相似文献   
777.
The activity of calcium pumping adenosine triphosphatase (Ca2+-ATPase) in cardiac sarcoplasmic reticulum plays a pivotal role in myocardiac contraction-relaxation. The Ca2+-ATPase activity is controlled by phosphorylation and dephosphorylation of a sarcoplasmic reticulum protein "phospholamban" in response to neurotransmitters and drugs. To clarify the role of Ca2+-ATPase in the development of cardiac rigor mortis, we examined the changes of cardiac rigidity and cardiac sarcoplasmic reticulum Ca2+-ATPase activity up to 5 h after the decapitation of rats. Fifteen minutes after decapitation, the rats showed a cardiac rigidity on left ventricles. After 30 min, rigidity was obvious over the whole heart. After 1 h, the rigidity reached a high degree which was maintained for the rest of the observation period. On the other hand, the Ca2+-ATPase activity controlled by phosphorylation and dephosphorylation of phospholamban did not change for the whole observation period (5 h). Another Ca2+-ATPase activity representing the total amount of Ca2+-ATPase in sarcoplasmic reticulum gradually decreased. The data suggest that no significant phosphorylation or dephosphorylation of phospholamban occurs for a short time, at least for 5 h, after death and that the Ca2+-ATPase tends to relax the myocardium against the development of cardiac rigor mortis.  相似文献   
778.
Postmortem stability of DNA   总被引:11,自引:0,他引:11  
High-molecular-weight DNA was recovered postmortem in sufficient quantities from various human organ tissues as well as from blood, although not all organs were equally well suitable. Good DNA stability was found in brain cortex, lymph nodes and psoas muscle over a period of three weeks postmortem. Spleen and kidney showed good DNA stability up to five days postmortem but after longer periods, rapid degradation was observed. Yields of DNA from blood were not consistent because of the non homogeneity of samples. Blood clots were rich with DNA. Generally, the amount of degraded DNA correlated directly with the duration of the postmortem period. However in some cases, DNA degradation was already prominent after a short period. However in some cases, DNA degradation was already prominent after a short period. Case histories showed that high environmental temperature at the site of death and/or infectious diseases prior to death were the main factors for rapid autolysis. Gradual disappearance to complete loss of the long fragments (15-23 kb) was observed in DNA fingerprinting using the minisatellite probe 33.15. No extra-bands were noted, thus excluding erroneous conclusions. However, evidentiary value of older samples was lower.  相似文献   
779.
A method for the routine profiling of illicit heroin samples received in casework has been developed which depends on simple and straightforward sample pretreatment, followed by gas chromatography on a capillary column using flame-ionization detection. The factors affecting the choice of each aspect of the procedure are discussed, as are the statistical data for sampling and the chromatography. Components of illicit heroin derived from opium and other adulterants have been identified. The significance of data from samples examined in 1986 is discussed.  相似文献   
780.
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