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   23004篇
  免费   667篇
各国政治   1103篇
工人农民   907篇
世界政治   1845篇
外交国际关系   859篇
法律   13675篇
中国共产党   6篇
中国政治   116篇
政治理论   4928篇
综合类   232篇
  2020年   286篇
  2019年   337篇
  2018年   428篇
  2017年   531篇
  2016年   553篇
  2015年   392篇
  2014年   457篇
  2013年   2357篇
  2012年   538篇
  2011年   571篇
  2010年   490篇
  2009年   499篇
  2008年   594篇
  2007年   618篇
  2006年   598篇
  2005年   512篇
  2004年   518篇
  2003年   552篇
  2002年   488篇
  2001年   872篇
  2000年   786篇
  1999年   664篇
  1998年   366篇
  1997年   305篇
  1996年   266篇
  1995年   260篇
  1994年   306篇
  1993年   278篇
  1992年   426篇
  1991年   488篇
  1990年   442篇
  1989年   454篇
  1988年   433篇
  1987年   466篇
  1986年   456篇
  1985年   442篇
  1984年   391篇
  1983年   413篇
  1982年   325篇
  1981年   310篇
  1980年   233篇
  1979年   351篇
  1978年   232篇
  1977年   198篇
  1976年   181篇
  1975年   190篇
  1974年   204篇
  1973年   188篇
  1972年   154篇
  1971年   139篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
741.
As the emergence of nongovernmental conservation efforts generates conflict among various stakeholders, the causal story that each party articulates regarding conservation and the causes of land degradation reflects their unique interests. This study uses existing literature to evaluate causal stories surrounding a contemporary conservation effort: Montana's American Prairie Reserve. Through qualitative review of web‐based documents and newspaper articles, it generates a preliminary account of key stakeholders' causal stories. The case study suggests that parties who might be disadvantaged by ascribing responsibility for environmental harms in an adversarial fashion may instead elect to articulate causal stories that are more neutral than existing approaches might forecast. The study concludes by suggesting that further development of causal story literature may enable it to better address contemporary conservation efforts.  相似文献   
742.
The U.S. electric power sector has experienced a substantial shift of the generation mix since the turn of the century, moving from heavy reliance on coal‐powered generation to one drawing more from natural gas and, more recently, renewables. This transition has been forged by a mix of macroeconomic factors (recession and recovery); technological breakthroughs (horizontal drilling coupled with hydraulic fracturing; improvements in natural gas plant efficiency); clean energy policies at federal, state, and local levels of government; and private sector demands for carbon‐free energy sources. These factors have combined to reduce carbon emissions from electric power generation substantially this century. In this article we examine the extent of this transition, its causes, as well as the distinct American institutional factors steering it, including energy and environmental federalism, electoral politics, and the political economy of clean energy policy enactment and resistance.  相似文献   
743.
744.
Journal of Youth and Adolescence - Parent–adolescent conflict can be intense, yet parents and adolescents do not always agree on the intensity of conflict. Conflict intensity tends to change...  相似文献   
745.
The Journal of Technology Transfer - University technology transfer is often associated with formal transmission of science-based inventions, for instance through the licensing of patented...  相似文献   
746.
The Journal of Technology Transfer - This paper explores current trends in knowledge spillover research using scientometric analysis of all papers published in journals indexed in the Web of...  相似文献   
747.
748.
Postmortem computed tomography (PMCT) is integrated into the evaluation of decedents in several American medical examiner offices and medicolegal death investigative centers in many other countries. We retrospectively investigated the value of PMCT in a series of firearm homicide cases from a statewide centralized medical examiner’s office that occurred during 2016. Autopsies were performed or supervised by board-certified forensic pathologists who reviewed the PMCT scans prior to autopsy. PMCT scans were re-evaluated by a forensic radiologist blinded to the autopsy findings and scored by body region (head–neck, thoracoabdominal, and extremities). Injury discrepancies were scored using a modified Goldman classification and analyzed with McNemar’s test. We included 60 males and 20 females (median age 31 years, range 3–73). Based on PMCT, 56 (79.1%) cases had injuries relevant to the cause of death in a single body region (24 head–neck region, 32 thoracoabdominal region). Out of these 56 cases, 9 had a missed major diagnosis by PMCT outside that region, including 6 extremity injuries visible during standard external examination. Yet all had evident lethal firearm injury. We showed that PMCT identifies major firearm injuries in homicide victims and excludes injuries related to the cause of death in other regions when a single body region is injured. Although PMCT has a known limited sensitivity for soft tissue and vascular pathology, it can be combined with external examination to potentially reduce or focus dissections in some of these cases depending on the circumstances and medicolegal needs.  相似文献   
749.
This paper examines the reliability of Structure from Motion (SfM) photogrammetry as a tool in the capture of forensic footwear marks. This is applicable to photogrammetry freeware DigTrace but is equally relevant to other SfM solutions. SfM simply requires a digital camera, a scale bar, and a selection of oblique photographs of the trace in question taken at the scene. The output is a digital three-dimensional point cloud of the surface and any plastic trace thereon. The first section of this paper examines the reliability of photogrammetry to capture the same data when repeatedly used on one impression, while the second part assesses the impact of varying cameras. Using cloud to cloud comparisons that measure the distance between two-point clouds, we assess the variability between models. The results highlight how little variability is evident and therefore speak to the accuracy and consistency of such techniques in the capture of three-dimensional traces. Using this method, 3D footwear impressions can, in many substrates, be collected with a repeatability of 97% with any variation between models less than ~0.5 mm.  相似文献   
750.
When a bullet punctures a surface, it leaves behind a bullet impact, which can be analyzed in order to determine the origin and trajectory path from which a bullet was discharged using many different scientific methods to reconstruct a shooting scene. The purpose of the research was to test the accuracy and repeatability of reconstructing the impact angle of single bullet impacts using the ellipse method. The research was conducted by firing various calibers of ammunition into drywall panels positioned at varying angles of incidence from 88° until ricochet occurred. This was done in order to determine which caliber type and angle of incidence are most accurate and precise for reconstructing a shooting scene. The study examined four caliber types fired into drywall panels, with 5 repeated shots for each of the 11 angles of incidence (n = 220). Furthermore, 31 participants partook in the study to estimate a bullet impact angle of incidence utilizing the ellipse method. The results show that the best performance (accuracy and repeatability) is seen with the measurements of the 0.45 caliber ammunition. When angle of incidences is low (<64°), the performance (accuracy and repeatability) was seen to be better in all caliber ammunitions. Overall, the data provided for single bullet impacts deposited in drywall show that the ellipse method is useful in providing measurements for most crime scene reconstruction purposes and has also demonstrated that results vary depending on the type of ammunition, firearm, and angle of incidence being examined.  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