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   2603篇
  免费   44篇
各国政治   126篇
工人农民   62篇
世界政治   152篇
外交国际关系   66篇
法律   1917篇
中国政治   21篇
政治理论   286篇
综合类   17篇
  2020年   30篇
  2019年   22篇
  2018年   22篇
  2017年   33篇
  2016年   40篇
  2015年   23篇
  2014年   38篇
  2013年   187篇
  2012年   60篇
  2011年   68篇
  2010年   36篇
  2009年   35篇
  2008年   56篇
  2007年   71篇
  2006年   71篇
  2005年   74篇
  2004年   72篇
  2003年   70篇
  2002年   70篇
  2001年   156篇
  2000年   123篇
  1999年   76篇
  1998年   26篇
  1995年   18篇
  1994年   22篇
  1993年   21篇
  1992年   63篇
  1991年   69篇
  1990年   61篇
  1989年   84篇
  1988年   83篇
  1987年   72篇
  1986年   76篇
  1985年   65篇
  1984年   35篇
  1983年   41篇
  1982年   19篇
  1981年   30篇
  1979年   28篇
  1978年   21篇
  1977年   27篇
  1976年   19篇
  1975年   31篇
  1974年   30篇
  1973年   31篇
  1972年   32篇
  1971年   24篇
  1970年   20篇
  1969年   24篇
  1968年   20篇
排序方式: 共有2647条查询结果,搜索用时 31 毫秒
931.
932.
Studies on ballistic trauma to the ribs and thorax, cranium, and long bones demonstrate the potential of obtaining a bullet caliber from an entrance wound. In order to validate prior research on caliber estimation in bone tissue and assess the viability of bullet type determination based on the macroscopic evidence at the entrance wound, thirty fleshed pork (Sus scrofa) shoulders (humeri) were shot with either lead or copper jacketed bullets in one of three calibers; 0.22, 9 mm, or 0.38. Overall, our findings are consistent with previous research indicating that calibers can be grouped into “small” and “large” categories. Bullet type, lead or copper jacket, can be ascertained based on cortical flaking and the analysis of materials deposited around the entry wound. The addition of this evidence holds value in cases where no firearm or ballistic evidence is recovered from a crime scene.  相似文献   
933.
Forensic taphonomy is an essential research field; however, the decomposition of human cadavers at forensic science facilities may lead to nutrient loading and the introduction of unique biological compounds to adjacent areas. The infrastructure of a water retention system may provide a mechanism for the biogeochemical processing and retention of nutrients and compounds, ensuring the control of runoff from forensic facilities. This work provides a proof of concept for a hydrologic retention system and an autonomous water quality monitoring program designed to mitigate runoff from The Southeast Texas Applied Forensic Science (STAFS) Facility. Water samples collected along a sample transect were analyzed for total phosphorous, total nitrogen, , , NH4, F?, and Cl?. Preliminary water quality analyses confirm the overall effectiveness of the water retention system. These results are discussed with relation to how this infrastructure can be expanded upon to monitor additional, more novel, byproducts of forensic science research facilities.  相似文献   
934.
This study examined the effects of fire on the features associated with saw marks in bone. Both class and individual characteristics were examined using stereomicroscopy and scanning electron microscopy (SEM). Twenty-four semifleshed Sus scrofa L. tibiae were sawed into three sections with the middle section having deep and shallow false starts. Twelve saw blades of varying age and type were each used to cut two tibiae. In each case, the first tibia was burned in an outdoor open fire to the point of partial calcination. The second tibia, our control, was macerated using a heated enzyme solution. Controls and burned specimens were examined for the following characteristics: breakaway spur, tooth hop, false start, exit chipping, tooth imprint, breakaway notch, pull out striae, kerf flare, and blade drift. In general, there was parity in the observed characteristics in the burned samples using the SEM and the stereomicroscope. SEM observation, however, provided enhanced images, with the addition of observing individual tooth imprints, previously not visible. Therefore, this study recommends using an SEM for the examination of saw cuts in burnt bone.  相似文献   
935.
In recent years, a large number of designer drugs sold as “Bath Salts” have appeared on the market. In July of 2011, Raving Dragon Novelty Bath Salts was obtained over the Internet. This product became unavailable in October of that year coinciding with the DEA issuing a temporarily schedule of mephedrone, methylone, and MDPV. Four months later in February of 2012, a new product was released from the same company under the new name Raving Dragon Voodoo Dust. The contents of both products were identified using spectroscopy methods: nuclear magnetic resonance, infrared, UV–visible, tandem mass spectrometry, and high-resolution time-of-flight mass spectrometry. It was determined that Raving Dragon Novelty Bath Salts contained methylone. The replacement product Raving Dragon Voodoo Dust contained the unscheduled drug pentedrone. The Raving Dragon brand of products illustrates the rapid change of ingredients in these products to circumvent laws restricting availability, distribution, and use.  相似文献   
936.
937.
The current evidence base for in-home services in child welfare is limited, with insufficient research on the use of in-home services among ethnically diverse populations. This article describes a case study examining the use of a community-defined practice and evidence approach to develop tribally based in-home service models with Alaska Native communities. The models were co-created by tribal elders, community members, and service providers, with technical assistance provided by the Western and Pacific Child Welfare Implementation Center (WPIC). Research findings suggest that this is an effective approach to developing culturally appropriate child welfare practices while also building local support and ownership.  相似文献   
938.
The isoelectric focusing of keratins in hair followed by silver staining   总被引:1,自引:0,他引:1  
An isoelectric focusing method followed by silver staining has been developed for the study of keratins which is as effective as two-dimensional electrophoresis and fluorography for hair species identification. Hair from dogs, rabbits, horses, cows, guinea-pigs, donkeys, sheep and cats were successfully identified. Narrow pH ranges were used to observe heterogeneity in human hair. Although this heterogeneity may be affected by environmental conditions, it may be of use in criminalistics.  相似文献   
939.
940.
Authentic black-powder muzzle-loader weapons and replicas are used today primarily for hunting game such as deer and hogs. The following is a case presentation of accidental death from cerebral trauma caused by a .45-caliber black-powder-rifle breech plug implanting in the victim's brain.  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