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   4142篇
  免费   336篇
各国政治   69篇
工人农民   73篇
世界政治   105篇
外交国际关系   291篇
法律   2169篇
中国共产党   42篇
中国政治   426篇
政治理论   416篇
综合类   887篇
  2024年   11篇
  2023年   81篇
  2022年   67篇
  2021年   73篇
  2020年   152篇
  2019年   118篇
  2018年   136篇
  2017年   180篇
  2016年   172篇
  2015年   107篇
  2014年   238篇
  2013年   379篇
  2012年   288篇
  2011年   285篇
  2010年   207篇
  2009年   257篇
  2008年   254篇
  2007年   275篇
  2006年   231篇
  2005年   222篇
  2004年   192篇
  2003年   141篇
  2002年   108篇
  2001年   90篇
  2000年   54篇
  1999年   33篇
  1998年   15篇
  1997年   8篇
  1996年   8篇
  1995年   22篇
  1994年   6篇
  1993年   5篇
  1992年   12篇
  1991年   5篇
  1990年   6篇
  1989年   4篇
  1988年   4篇
  1987年   11篇
  1986年   8篇
  1985年   3篇
  1984年   5篇
  1983年   5篇
排序方式: 共有4478条查询结果,搜索用时 593 毫秒
831.
《Local Government Studies》2012,38(6):977-1000
ABSTRACT

In the public context, the efficient and effective management of procurement activities has a crucial impact on the achievement of operational and broader government objectives. In particular, the potential contribution of procurement within local governments has been broadly recognized, and organisational procurement choices represent a strategic aspect that must be managed to contribute to these objectives. Through the analysis of data on 371 Italian municipalities, this paper discusses how to design procurement organisation variables for local governments. Three possible organisational models are identified (i.e., authoritative procurement, silo procurement, and local procurement) and discussed from the perspective of internal and external contingencies that may affect organisational decisions.  相似文献   
832.
Research has suggested that affective polarization (AP)—the extent to which partisans view each other as a disliked out-group—has increased, especially in two-party political systems such as in the US. The understanding of AP in multiparty systems remains limited. We study AP in Finland, characterized by a strong multiparty system and a low level of ideological polarization, between 2007 and 2019. We find that AP has increased, driven mainly by voters evaluating their least favorite party more negatively. We also propose an approach that goes beyond earlier literature, which has mostly used a single aggregate metric to measure AP. Using latent profile analysis, we find that voters are grouped into blocs that view some parties positively and others negatively. This suggests that the complex dynamics of AP in multiparty democracies involve relationships between not just individual parties but between what we call affective blocs that span across party lines.  相似文献   
833.
Job Corps is the nation's largest and most comprehensive career technical training and education program for at‐risk youth ages 16 to 24. Using the sample from a large‐scale experiment of the program from the mid‐1990s, this article uses tax data through 2015 (20 years later) to examine long‐term labor market impacts. The study finds some long‐term beneficial effects for the older students, with employment gains of 4 percentage points, 40 percent reductions in disability benefit receipt, and 10 percent increases in tax filing rates in 2015. For these students, program benefits exceeded program costs from the social perspective. This study is the first to establish that a national program for disconnected youth can produce long‐term labor market gains, and can be a positive investment made for society. The results suggest that intensive, comprehensive services that focus on developing both cognitive and noncognitive skills are important for improving labor market prospects for this population.  相似文献   
834.
Abstract:  Denaturing high-performance liquid chromatography (DHPLC) was evaluated as a sequencing-independent means of detecting the presence of sequence differences in pair-wise mixtures of nonconcordant amplicons of human mitochondrial DNA (mtDNA). A total of 920 pair-wise combinations of HV1 and HV2 mtDNA amplicons from 95 individuals were assayed by DHPLC for sequence concordance/nonconcordance. For the 72 combinations of amplicons from different individuals who shared identical DNA sequences, DHPLC assays consistently indicated sequence concordance between the samples. This was in 100% agreement with sequencing data. For the 849 combinations of amplicons which differed in sequence, DHPLC detected the presence of sequence nonconcordance in all but 13 assays to yield 98.5% concordance with sequencing. Thus, DHPLC can be used to detect a diversity of sequence differences (transitions, transversions, insertions, and deletions) in the mtDNA D-loop. Accordingly, DHPLC may have utility as a presumptive indicator of mtDNA sequence concordance samples, as a screen for heteroplasmy/situational mixtures, and as a means for the physical fractionation of the individual contributors to an mtDNA mixture prior to sequencing.  相似文献   
835.
Abstract:  The forkhead box P2 ( FOXP2 ) gene is specifically involved in speech and language development in humans. The sequence is well conserved among many vertebrate species but has accumulated amino acid changes in the human lineage. The aim of this study was to develop a simple method to discriminate between human and nonhuman vertebrate DNA in forensic specimens by amplification of a human-specific genomic region. In the present study, we designed an allele-specific polymerase chain reaction (PCR) using primers to amplify smaller than 70-bp regions of FOXP2 to identify DNA as being of human or nonhuman, including ape, origin. PCR amplification was also successfully performed using fluorescence-labeled primers, and this method allows a single PCR reaction with a genomic DNA sample as small as 0.01 ng. This system also identified the presence of human DNA in two blood stains stored for 20 and 38 years. The results suggested the potential usefulness of FOXP2 as an identifier of human DNA in forensic samples.  相似文献   
836.
Abstract: Human growth hormone (HGH) is a relatively small protein consisting of 191 amino acids and has an average mass of 22,125 amu. The forensic analysis of proteins such as HGH must meet the analytical sufficiency requirements for the laboratory and consists of a binary approach. A suspected sample is analyzed as the whole protein for retention time and mass determination using high performance liquid chromatography equipped with a photodiode array and liquid chromatography mass spectrometry. Further fragmentation of the protein using a proteolytic enzyme adds another dimension to the specificity of the analysis. Porcine trypsin digests proteins in a very predictable manner and yields peptide fragments of the original protein that can be used as a means for fingerprinting the larger biomolecule. In silico, or theoretical, digestion of HGH by trypsin yields 21 peptides ranging in size from 1 to 23 amino acids in length. The larger fragments containing higher numbers of amino acids give more specificity to identifying a protein based on a fragment produced by the digestion of trypsin. Herein, the analysis of HGH using a proteolytic approach is presented that meets the Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG) recommendations for the identification of unknown substances.  相似文献   
837.
Abstract: Guanaco (Lama guanicoe) is a protected and widely distributed ungulate in South America. A poacher, after killing guanacos in Valle Chacabuco, Chilean Patagonia, transported and stored the meat. Samples were retrieved by local police but the suspect argued that the meat was from a horse. Mitochondrial cytochrome b gene (774 pb), 15 loci microsatellites, and SRY gene were used to identify the species, number of animals and their population origin, and the sex of the animals, respectively. Analysis revealed that the samples came from a female (absence of SRY gene) Patagonian guanaco (assignment probability between 0.0075 and 0.0282), and clearly distinguishing it from sympatric ungulates (E‐value = 0). Based on the evidence obtained in the field in addition to forensic data, the suspect was convicted of poaching and illegally carrying fire arms. This is the first report of molecular tools being used in forensic investigations of Chilean wildlife indicating its promising future application in guanaco management and conservation.  相似文献   
838.
Abstract:  This paper presents results of experiments related to individual video camera identification using a correlation coefficient of fixed pattern noise (FPN) in image sensors. Five color charge-coupled device (CCD) modules of the same brand were examined. Images were captured using a 12-bit monochrome video capture board and stored in a personal computer. For each module, 100 frames were captured. They were integrated to obtain FPN. The results show that a specific CCD module was distinguished among the five modules by analyzing the normalized correlation coefficient. The temporal change of the correlation coefficient during several days had only a negligible effect on identifying the modules. Furthermore, a positive relation was found between the correlation coefficient of the same modules and the number of frames that were used for image integration. Consequently, precise individual camera identification is enhanced by acquisition of as many frames as possible.  相似文献   
839.
In this paper, we evaluate the efficiency of prosecutor office efficiency in the United States. Using multiple inputs and multiple outputs to characterize prosecutor office production, technical and scale efficiency are calculated for U.S. counties. Given the complex nature of service provision and potential heterogeneity based on judicial district size, we restrict our sample to those counties with populations between 100 and 500 thousand. Given the efficiency results, we also test whether efficiency is statistically related to median income and the percentage of minority population. The results suggest that prosecutor offices in more socio-economically disadvantages counties are more inefficient.   相似文献   
840.
气相色谱-串联质谱法分析尿和血中除草剂百草枯   总被引:1,自引:1,他引:0  
目的建立尿和血中百草枯的离子交换固相萃取-气相色谱-串联质谱分析方法。方法尿样加内标乙基百草枯,用732阳离子交换树脂提取;血样加内标乙基百草枯,用三氯乙酸凝聚蛋白质后取上清液用732阳离子交换树脂提取。提取物用硼氢化钠在水溶液中碱性条件下还原,还原物用有机溶剂提取进行气相色谱-串联质谱法分析。结果尿和血中百草枯的提取率分别为76%和74%,检测限分别为2ng/mL和10ng/mL,尿添加百草枯100ng/mL和血添加百草枯500ng/mL水平的回收率分别为99.6±5.6%和99.3±7.6%(Mean±CV)。结论本文建立的分析方法灵敏度高,能够满足中毒致死案件检验及临床毒物检验的需要。  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