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   168篇
  免费   7篇
各国政治   10篇
工人农民   14篇
世界政治   47篇
外交国际关系   4篇
法律   64篇
政治理论   36篇
  2024年   2篇
  2023年   3篇
  2022年   3篇
  2020年   6篇
  2019年   6篇
  2018年   3篇
  2017年   2篇
  2016年   7篇
  2015年   4篇
  2014年   4篇
  2013年   21篇
  2012年   5篇
  2011年   4篇
  2010年   3篇
  2009年   1篇
  2008年   12篇
  2007年   14篇
  2006年   13篇
  2005年   10篇
  2004年   6篇
  2003年   6篇
  2002年   1篇
  2001年   3篇
  2000年   3篇
  1999年   3篇
  1998年   5篇
  1997年   2篇
  1996年   2篇
  1995年   2篇
  1994年   1篇
  1992年   1篇
  1991年   1篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1981年   4篇
  1979年   1篇
  1977年   1篇
  1973年   1篇
  1967年   1篇
  1966年   1篇
排序方式: 共有175条查询结果,搜索用时 31 毫秒
21.
The U.S. electricity market, like electricity markets in most countries, is heavily dependent on fossil-fuel generation from centralized power applications. This paper reviews the factors that led to the sector??s reliance on fossil fuels and presents a future vision of the U.S. electricity sector based on a varied spectrum of sustainable energy resources ranging in scale from large, centralized facilities to small, localized energy systems. This spectrum includes low-emissions energy and energy efficiency, as well as macro-generation, micro-grids, distributed generation, micro-generation and end-user conservation. We discuss the evidence that each element of this spectrum is a viable and proven technology, the balanced integration of which could shape an electricity sector that adheres to sustainability principles. This paper concludes with a discussion of the institutional barriers that need to be addressed to successfully achieve a transition toward a more future sustainable electricity sector based on the variations in scale.  相似文献   
22.
Phenazepam is a long-acting benzodiazepine that, unlike other benzodiazepines, is currently not scheduled as a narcotic in Finland, most other European countries or the USA. It is used as an anxiolytic, sedative-hypnotic and anti-epileptic, mainly in Russia. In Finland, as well as in some other countries, an increase in the unauthorized use of phenazepam has been observed in recent years. In the one year period between July 1, 2010 and June 30, 2011 the prevalence of phenazepam in Finland was assessed among drivers apprehended for driving under the influence of drugs (DUID), in medico-legal autopsy cases and in police confiscations of illicit drugs. In DUID cases an LC-MS/MS method preceded by solid phase extraction was used for the determination of phenazepam. In the post-mortem investigations the sample preparation consisted of liquid-liquid extraction followed by derivatization and the determination was carried out by GC-MS. The police confiscations were analysed by GC-MS. There were 141 positive phenazepam cases among apprehended drivers, representing approximately 3.5% of all confirmed drug cases (n=4007) in this time period. The median (range) phenazepam blood concentration in DUID cases was 0.061 mg/L (0.004-3.600 mg/L). The median phenazepam concentration in cases with no concomitant stimulant use was significantly higher than the overall median concentration. Phenazepam was found in 17 medico-legal autopsy cases and the median (range) blood concentration was 0.048 mg/L (0.007-1.600 mg/L). Phenazepam was not considered by the medico-legal team to be the sole cause of death in any of the cases, the majority of them being accidental opiod overdoses. There were 26 seizures of phenazepam by the Police in the time period studied, some of the batches consisted of a mixture of phenazepam and stimulant designer drugs. The data show that phenazepam abuse is a widespread phenomenon in Finland. A typical user was a male multi-drug user in his 30s. The concentration range of phenazepam among apprehended drivers and medico-legal autopsy cases was wide and the drug was usually found along with other psychoactive drugs. Therefore, although it seems likely that phenazepam contributed to impairment of driving in some DUID cases, the extent of its effect remains unclear and further studies are needed to define the concentrations causing impairment and toxicity.  相似文献   
23.
A physical fit is an important observation that can result from the forensic analysis of trace evidence as it conveys a high degree of association between two items. However, physical fit examinations can be time-consuming, and potential bias from analysts may affect judgment. To overcome these shortcomings, a data analysis algorithm using mutual information and a decision tree has been developed to support practitioners in interpreting the evidence. We created these tools using data obtained from physical fit examinations of duct tape and textiles analyzed in previous studies, along with the reasoning behind the analysts' decisions. The relative feature importance is described by material type, enhancing the knowledge base in this field. Compared with the human analysis, the algorithms provided accuracies above 90%, with an improved rate of true positives for most duct tape subsets. Conversely, false positives were observed in high-quality scissor cut (HQ-HT-S) duct tape and textiles. As such, it is advised to use these algorithms in tandem with human analysis. Furthermore, the study evaluated the accuracy of physical fits when only partial sample lengths are available. The results of this investigation indicated that acceptable accuracies for correctly identifying true fits and non-fits occurred when at least 35% of a sample length was present. However, lower accuracies were observed for samples prone to stretching or distortion. Therefore, the models described here can provide a valuable supplementary tool but should not be the sole means of evaluating samples.  相似文献   
24.
25.
This article examines the evolution of transnational Zapatista solidarity networks. Although scholars have described an emerging "mutuality" between the Zapatista movement and its allies at the level of international framing, this article considers how the Zapatistas forged this mutuality on the ground, through active redefinition of alliances with Northern supporters. It argues that the Zapatistas delimited who was included in their solidarity networks, set new terms for partnerships, and redefined legitimacy in their transnational alliances. In so doing, they asserted their autonomy from donors. They also fostered discourses and practices of mutual solidarity and Southern leadership, shifting the balance of power between North and South. The case both illuminates the possibilities for Southern movements to challenge Northern control from within and suggests potential pitfalls of doing so; by defying Northern NGOs' influence, the Zapatistas may have risked their long-term viability.  相似文献   
26.
Children living on ‘the edge-of-care’ are typically known to local safeguarding authorities and are considered likely to face risks to their safety. Many are subject to a child protection plan and/or involved in ‘pre-proceedings’ processes. A growing number of their parents face (un)diagnosed mental health difficulties as well as economic and social precarity. This article draws on a mixed methods evaluation of a pilot service in the East of England offering a therapeutically led attachment-based intervention for families. The service cross-cuts health and social care, allowing psychologists and psychotherapists to work alongside social workers and other practitioners. The evaluation examined psychological and safeguarding outcomes and explored practitioner perspectives. A key outcome was that 85.4% of families were enabled to remain, or reunite with their child, compared with an estimated 50% of ‘edge-of-care’ cases nationally. This supports the need for similarly oriented interventions that could help lower the incidence of child removals.  相似文献   
27.
The degree to which different social groups get along is a key indicator of the cohesiveness of a society. This study examines perceptions of social cohesion among Europeans and explains variations in those perceptions by considering the separate and combined effects of economic strain and institutional trust. Analyses were conducted with the 27 member countries of the EU based on the Eurobarometer 74.1 on poverty and social exclusion conducted in 2010. Results show that individuals living in households experiencing economic strain perceive social cohesion to be weaker than their less economically hard‐pressed counterparts. By contrast, individuals trusting their political institutions perceived there to be higher levels of cohesion. Furthermore, institutional trust substantially moderates the negative relationship between economic strain and perceptions of cohesion. These results are robust to various model specifications. Moreover, extending the analysis revealed that this moderating effect held when considering social relations between the poor and rich and between different racial and ethnic groups. Theoretical and practical implications of the results are discussed.  相似文献   
28.
A fast and simple method to detect some commonly abused illicit drugs, amphetamine, methamphetamine, 3,4-methylendioxy-amphetamine (MDA), 3,4-methylendioxy-methamphetamine (MDMA), 3,4-methylendioxy-N-ethylamphetamine (MDEA) and phencyclidine (PCP) in urine using solvent microextraction (SME) combined with gas chromatography (GC) analysis has been developed. The extraction is conducted by suspending a 2 microl drop of chloroform in a 2 ml urine sample. Following 8 min of extraction, the organic solvent is withdrawn into the syringe and injected into a GC with a pulsed discharge helium ionization detector (PDHID). The effects of different extraction solvents and times, pH and sample preparation were studied. The optimized method was capable of detecting drugs in urine at concentrations below Substance Abuse and Mental Health Services Administration (SAMHSA) established cut-off values for preliminary testing. Good linearity and reproducibility of extraction were obtained. The limits of detection were 0.5 microg/ml for amphetamine, 0.1 microg/ml for methamphetamine and MDA, 0.05 microg/ml for MDMA, 0.025 microg/ml for MDEA and 0.015 microg/ml for PCP. Relative standard deviation (R.S.D.) values ranged between 5 and 20% for the studied drugs.  相似文献   
29.
Five experiments tested the idea that instructing a witness to close their eyes during retrieval might increase retrieval success. In Experiment 1 participants watched a video, before a cued-recall test for which they were either instructed to close their eyes, or received no-instructions. Eye-closure led to an increase in correct cued-recall, with no increase in incorrect responses. Experiments 2-5 sought to test the generality of this effect over variations in study material (video or live interaction), test format (cued- or free-recall) and information modality (visual or auditory details recalled). Overall, eye-closure increased recall of both visual detail and auditory details, with no accompanying increase in recall of false details. Collectively, these data convincingly demonstrate the benefits of eye-closure as an aid to retrieval, and offer insight into why hypnosis, which usually involves eye-closure, may facilitate eyewitness recall.  相似文献   
30.
Population differences in dental development between Black and White ethnic groups have been debated but not previously studied in the UK. Using inappropriate data for dental age estimation (DAE) could lead to erroneous results and injustice. Data were collected from dental panoramic radiographs of 5590 subjects aged 6–24 years in a teaching hospital archive. Demirjian stages were determined for left-sided teeth and third molars and data collected regarding hypodontia and third molar agenesis. Third molar development in self-assigned Black British, including other self-assigned Black ethnicity, was compared with that of self-assigned White British subjects. Data were compared for males and females in the two ethnic groups using T-tests for Demirjian Stages A–G of third molar development and Mann-Whitney tests for Stage H once a cut-off age at the maximum age for Stage G had been imposed. Third molar development occurred earlier in subjects of Black ancestry compared to those of White ancestry. While both ethnic groups showed large age ranges for every third molar stage, in female subjects these generally occurred at least 1.5 years earlier, and in males at least one year earlier. Hypodontia and third molar agenesis were more prevalent in White British, but the ethnic difference in third molar development persisted in subjects with complete dentitions. This is a large study that confirms ethnic differences in a London population, emphasises the difficulties of establishing the 18-year-old threshold using DAE, and confirms the risk of overestimating the age of individuals of Black ethnicity using White ethnic reference data.  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