全文获取类型
收费全文 | 17998篇 |
免费 | 305篇 |
专业分类
各国政治 | 486篇 |
工人农民 | 1456篇 |
世界政治 | 763篇 |
外交国际关系 | 578篇 |
法律 | 10975篇 |
中国共产党 | 34篇 |
中国政治 | 128篇 |
政治理论 | 3747篇 |
综合类 | 136篇 |
出版年
2021年 | 62篇 |
2020年 | 148篇 |
2019年 | 131篇 |
2018年 | 1424篇 |
2017年 | 1384篇 |
2016年 | 1242篇 |
2015年 | 283篇 |
2014年 | 236篇 |
2013年 | 848篇 |
2012年 | 414篇 |
2011年 | 1145篇 |
2010年 | 1175篇 |
2009年 | 815篇 |
2008年 | 1024篇 |
2007年 | 995篇 |
2006年 | 335篇 |
2005年 | 359篇 |
2004年 | 459篇 |
2003年 | 376篇 |
2002年 | 263篇 |
2001年 | 353篇 |
2000年 | 329篇 |
1999年 | 258篇 |
1998年 | 164篇 |
1997年 | 123篇 |
1996年 | 158篇 |
1995年 | 142篇 |
1994年 | 149篇 |
1993年 | 127篇 |
1992年 | 198篇 |
1991年 | 249篇 |
1990年 | 212篇 |
1989年 | 198篇 |
1988年 | 221篇 |
1987年 | 201篇 |
1986年 | 220篇 |
1985年 | 192篇 |
1984年 | 172篇 |
1983年 | 165篇 |
1982年 | 106篇 |
1981年 | 122篇 |
1980年 | 101篇 |
1979年 | 106篇 |
1978年 | 96篇 |
1977年 | 86篇 |
1976年 | 64篇 |
1975年 | 64篇 |
1974年 | 65篇 |
1973年 | 77篇 |
1971年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A sensitive method for the detection of anti-A and anti-B hemagglutinins in fresh saliva has been developed. The method utilizes a bromelin treated erythrocyte suspension as indicator cells and includes a simple procedure to concentrate these hemagglutinins. Antiserum directed against immunoglobulin A enhances the hemagglutination assay. We find that these salivary hemagglutinins are present in over 90% of the population and that their titer remains stable over a period of two months. These hemagglutinins can be used to blood type the donor of a saliva sample and can be used in a confirmatory test that complements the commonly used absorption-inhibition test which is used to detect salivary blood group agglutinogens. In preliminary studies we have determined that hemagglutinins can be successfully isolated and analyzed from dried saliva stains. 相似文献
992.
993.
The research reported in this article sought to estimate the feasibility of measuring patterns of forgetting and forward telescoping in victimization survey data. It was suggested that if these two sources of memory bias could be accurately and reliably measured, victimization survey data could be adjusted to produce improved estimates of both the amount of crime and of changes in the crime rate over time. Examination of the data suggests that the likelihood of developing a general model for correcting mnemonic biases is very low. ll?is conclusion follows from: (I) evidence indicating differential victimization survey recall across reported and unreported crime events; (2) the apparent dissimilarities of telescoping/forgetting patterns across samples and seasons; and (3) the lack of a stable comparison estimate of the “true” distribution of incidents with which to calibrate a correction model. 相似文献
994.
In an effort to evaluate the situational determinants of crime, principal components analysis was used to reduce 59 demographic and socioeconomic characteristics of 840 American cities to six independent factors: affluence, stage in life cycle, economic specialization, expenditures policy, poverty, and urbanization. When regressed upon crime rates two of these six factors, urbanization and poverty, were found to be the more important criminogenic forces. The exception to this generalization was the South, where stage in life cycle was more important than poverty in explaining crime. One reason for this exception may be that the South, though having a lower standard of living than other regions of the country, does not have the “culture of poverty” usually associated with lower income. Contrary to the assumption upon which most ecology of crime studies are based, larger cities (over 100,000 in population) are not representative of all cities. Greater association between socioeconomic variables and crime was found in larger than in smaller cities. 相似文献
995.
996.
997.
998.
Ink lines made by porous tip and roller ball pens have been examined by high performance thin layer chromatography (HPTLC) and by transmission microspectrophotometry (VM) in the visible region. Better discrimination between apparently similar coloured inks was obtained with HPTLC but VM has value as an additional technique for ink examination. 相似文献
999.
1000.
Photography of bloodstains visualized by luminol 总被引:1,自引:0,他引:1