全文获取类型
收费全文 | 17373篇 |
免费 | 1159篇 |
专业分类
各国政治 | 701篇 |
工人农民 | 832篇 |
世界政治 | 1131篇 |
外交国际关系 | 529篇 |
法律 | 12198篇 |
中国共产党 | 2篇 |
中国政治 | 104篇 |
政治理论 | 2946篇 |
综合类 | 89篇 |
出版年
2023年 | 76篇 |
2021年 | 87篇 |
2020年 | 429篇 |
2019年 | 444篇 |
2018年 | 563篇 |
2017年 | 578篇 |
2016年 | 656篇 |
2015年 | 504篇 |
2014年 | 533篇 |
2013年 | 1792篇 |
2012年 | 481篇 |
2011年 | 500篇 |
2010年 | 532篇 |
2009年 | 557篇 |
2008年 | 506篇 |
2007年 | 502篇 |
2006年 | 520篇 |
2005年 | 432篇 |
2004年 | 430篇 |
2003年 | 352篇 |
2002年 | 403篇 |
2001年 | 671篇 |
2000年 | 602篇 |
1999年 | 480篇 |
1998年 | 238篇 |
1997年 | 171篇 |
1996年 | 191篇 |
1995年 | 189篇 |
1994年 | 169篇 |
1993年 | 175篇 |
1992年 | 304篇 |
1991年 | 311篇 |
1990年 | 294篇 |
1989年 | 275篇 |
1988年 | 304篇 |
1987年 | 262篇 |
1986年 | 321篇 |
1985年 | 317篇 |
1984年 | 246篇 |
1983年 | 226篇 |
1982年 | 177篇 |
1981年 | 154篇 |
1980年 | 143篇 |
1979年 | 219篇 |
1978年 | 116篇 |
1977年 | 91篇 |
1975年 | 94篇 |
1974年 | 124篇 |
1973年 | 79篇 |
1972年 | 79篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
831.
832.
ElSohly MA Ross SA Mehmedic Z Arafat R Yi B Banahan BF 《Journal of forensic sciences》2000,45(1):24-30
The analysis of 35,312 cannabis preparations confiscated in the USA over a period of 18 years for delta-9-tetrahydrocannabinol (delta9-THC) and other major cannabinoids is reported. Samples were identified as cannabis, hashish, or hash oil. Cannabis samples were further subdivided into marijuana (loose material, kilobricks and buds), sinsemilla, Thai sticks and ditchweed. The data showed that more than 82% of all confiscated samples were in the marijuana category for every year except 1980 (61%) and 1981 (75%). The potency (concentration of delta9-THC) of marijuana samples rose from less than 1.5% in 1980 to approximately 3.3% in 1983 and 1984, then fluctuated around 3% till 1992. Since 1992, the potency of confiscated marijuana samples has continuously risen, going from 3.1% in 1992 to 4.2% in 1997. The average concentration of delta9-THC in all cannabis samples showed a gradual rise from 3% in 1991 to 4.47% in 1997. Hashish and hash oil, on the other hand, showed no specific potency trends. Other major cannabinoids [cannabidiol (CBD), cannabinol (CBN), and cannabichromene (CBC)] showed no significant change in their concentration over the years. 相似文献
833.
We have demonstrated that skin viability decreases at a measurable rate following death in an animal model. The decreased skin viability was measured by fluorescein diacetate and ethidium bromide using fluorescence emission spectroscopy. There is significant decrease of the fluorescence intensity of the fluorescein diacetate assay between the 1-4 h, the 6-24 h, and the >40 h time points postmortem. For times between 6-24 h and >40 h postmortem the ethidium bromide assay showed consistent and significant increases in signal. The fluorescence measurements in this study showed that under the experimental conditions the time of death could be determined for <4, 6-24, and >40 hapotmotrem. The application of these assays in the field will require further study of the environmental factors. 相似文献
834.
835.
Sidorov VL Maiatskaia MV Liubimov IuA Babakhanian RV 《Sudebno-meditsinskaia ekspertiza》2000,43(4):29-30
Russian and foreign methods used in forensic medicine for detection of the semen in stains on material evidences are compared. The potentialities of quantitative immunofluorescence test for detection of the semen in stains on material evidences, developed at Bureau for Forensic Medical Expert Evaluations of the Leningrad region, are described. Unlike other methods used in Russia, this method detects the semen in stains in the absence of spermatozoa and in stains with very low amount of the semen. Our modification allows objective recording of the results with computer processing. The method is cheaper than its foreign analogs and its sensitivity is similar to them. 相似文献
836.
837.
838.
Knoppers BM 《McGill law journal. Revue de droit de McGill》2000,45(2):559-566
Rapid developments in the area of biotechnology within the next decade are likely to have a significant impact on Canadian society. This article outlines the practical and ethical issues that will need to be addressed in the face of scientific advances, and contemplates the development of an appropriate policy framework in this regard. Surveying the approaches to policy development taken thus far, the author notes the underlying need for greater transparency and public participation. Rational and effective policies will only result from additional basic scientific data being made available to a more informed and engaged Canadian public. 相似文献
839.
Simonov EA Sorokin VI Drozdov MA Kimstach TB Liubetskiĭ GV Vershtskaia GV 《Sudebno-meditsinskaia ekspertiza》2000,43(3):23-28
A protocol for comparative analysis of heroin making use of chromatographic methods and infra-red spectroscopy is presented. 相似文献
840.