全文获取类型
收费全文 | 12534篇 |
免费 | 133篇 |
专业分类
各国政治 | 564篇 |
工人农民 | 436篇 |
世界政治 | 998篇 |
外交国际关系 | 550篇 |
法律 | 7334篇 |
中国政治 | 87篇 |
政治理论 | 2617篇 |
综合类 | 81篇 |
出版年
2020年 | 147篇 |
2019年 | 211篇 |
2018年 | 275篇 |
2017年 | 249篇 |
2016年 | 252篇 |
2015年 | 175篇 |
2014年 | 235篇 |
2013年 | 1294篇 |
2012年 | 279篇 |
2011年 | 314篇 |
2010年 | 275篇 |
2009年 | 289篇 |
2008年 | 325篇 |
2007年 | 314篇 |
2006年 | 312篇 |
2005年 | 272篇 |
2004年 | 295篇 |
2003年 | 282篇 |
2002年 | 250篇 |
2001年 | 502篇 |
2000年 | 438篇 |
1999年 | 346篇 |
1998年 | 174篇 |
1997年 | 174篇 |
1996年 | 125篇 |
1995年 | 128篇 |
1994年 | 119篇 |
1993年 | 126篇 |
1992年 | 232篇 |
1991年 | 283篇 |
1990年 | 251篇 |
1989年 | 262篇 |
1988年 | 237篇 |
1987年 | 263篇 |
1986年 | 237篇 |
1985年 | 242篇 |
1984年 | 228篇 |
1983年 | 216篇 |
1982年 | 157篇 |
1981年 | 159篇 |
1980年 | 121篇 |
1979年 | 162篇 |
1978年 | 116篇 |
1977年 | 88篇 |
1976年 | 91篇 |
1975年 | 97篇 |
1974年 | 115篇 |
1973年 | 121篇 |
1972年 | 93篇 |
1971年 | 79篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
192.
Through a comparison of fingermark sweat corrosion of α phase brass in both the U.K. and Iraq, we show how samples from Iraq have improved fingermark corrosion over U.K. samples that require no additional enhancement prior to visualization. Over 50% of Iraqi samples produced fingermark corrosion with full ridge detail compared with 0% from the U.K. X-ray photoelectron spectroscopy analysis of the fingermark corrosion products showed that Iraqi samples exhibit more dezincification with the Zn:Cu ratio averaging 1:1.82 compared with 1:3.07 for U.K. samples. Auger spectroscopy showed the presence of both zinc oxide and copper (I) oxide. No copper (II) was observed on the surface of the corroded brass. Opportunities to exploit the optical properties of these thin film oxides to enhance the visualization of fingermark corrosion are considered, and the potential to use fingermark corrosion of metal as a means of visualizing fingerprints in war zones is discussed. 相似文献
193.
Previous research has shown that as crime scene location deprivation increases (lower socioeconomic status), the recovery of forensic material, principally DNA and fingerprints, also increases. However, this increase does not result in more crimes being solved by forensic means. In this study, we analyze stolen vehicle data and find a statistically significant positive association between deprivation and the amount of forensic material that matched either the victim or an associate of the victim on a criminal database. The nature of this association was investigated further by inspecting recovered stolen vehicles to establish whether the condition of a stolen vehicle and the tidiness of its interior influenced the recovery of forensic material that was attributed to the victim or an associate. Contradictory results suggest that other factors may contribute to understanding the association between the recovery of victim- or associate-attributable forensic material and crime scene location deprivation. 相似文献
194.
Recent headlines comparing the health risks of nanotechnology to those of asbestos have appeared in newspapers throughout the country and on the Internet. Governmental agencies and standard-setting organizations have begun considering and actually adopting requirements to protect against such purported risks. The plaintiffs’ bar and potential plaintiffs have surely taken note. There is every reason to believe that the era of mass tort and class actions related to nanotechnology—“nanotorts” for short—is rapidly approaching. This article examines what nanotort claims might look like, the role that regulations and industry practices may play in such lawsuits, potential defenses to those claims, and what nanotech companies can do now to guard against future nanotort liabilities. 相似文献
195.
Eun J. Lee Ph.D. In K. Hwang M.S. Nam Y. Kim M.D. Kyung L. Lee Ph.D. Myun S. Han Ph.D. Yang H. Lee Ph.D. Mu Y. Kim Ph.D. Moon S. Yang Ph.D. 《Journal of forensic sciences》2010,55(5):1202-1208
Abstract: The proper identification of illicit plants such as Papaver somniferum L (opium poppy) is important for law enforcement agencies. The identification of opium poppy was presently tested using 10 genetic markers that are universal for all plants or specific to a few poppy plants. The genetic distances of universal markers such as nuclear internal transcribed spacer (ITS), 18S rRNA, plastid rbcL, and trnL‐trnF intergenic spacer (IGS) of 14 species included in the Papaveraceae and Fumariaceae family were acquired by sequence comparisons. Both the ITS region and trnL‐trnF IGS showed high levels of interspecific divergence. Six Papaver genera‐specific markers were developed from coding regions involved in morphine biosynthesis. Three markers (TYDC, NCS, and BBE) produced amplicons only in opium poppy, providing a presence/absence test for opium poppy, while three additional markers (CYP80B1, SAT, and COR) were genus specific. These 10 markers might be useful for the forensic DNA analysis of opium poppy. 相似文献
196.
Victoria A. Smith M.N.S. Angi M. Christensen Ph.D. Sarah W. Myers B.S. 《Journal of forensic sciences》2010,55(6):1413-1415
Abstract: Several studies have investigated frontal sinus comparison for personal identification. One study addressed the statistical reliability of correct identification using automated digital methods and resulted in a 96% accuracy rate. Missed matches with the digital methods generally involved small, less featured sinuses. This study investigates the hypothesis that human examiners may be able to more accurately identify correct matches than digital methods, even when the comparisons involve small frontal sinuses. Participants were provided two sets of 28 radiographs and were instructed to identify matching radiographs and list the radiographs that did not have a corresponding match. Overall, error rates were low, with correct associations identified at a rate of 0.983. No incorrect associations (“false positives”) were made. Correct association rates were highest among participants “experienced” examining radiographs. Results support previous assertions that frontal sinus radiographs are a reliable means of personal identification even when the frontal sinuses are small. 相似文献
197.
Karen M. Kester Ph.D. Mary H. Toothman M.S. Bonnie L. Brown Ph.D. W. Scott Street IV Ph.D. Tracey D. Cruz Ph.D. 《Journal of forensic sciences》2010,55(6):1543-1551
Abstract: We tested the hypotheses that foraging insects can acquire human DNA from the environment and that insect‐delivered human DNA is of sufficient quantity and quality to permit standard forensic analyses. Houseflies, German cockroaches, and camel crickets were exposed to dusty surfaces and then assayed for human mitochondrial and nuclear loci by conventional and qPCR, and multiplex STR amplification. Over two experiments, 100% of insect groups and 94% of dust controls tested positive for human DNA. Of 177 individuals, 33–67% tested positive and 13 yielded quantifiable human DNA (mean = 0.022 ± 0.006 ng; mean dust control = 2.448 ± 0.960 ng); four had at least one positive allele call for one or more locus; eight others showed multiple peaks at some loci. Results imply that application to routine forensic casework is limited given current detection methodology yet demonstrate the potential use of insects as environmental samplers for human DNA. 相似文献
198.
199.
G K Murphy 《The American journal of forensic medicine and pathology》1991,12(2):98-101
Although gunshot is by far the most common means of homicide in the United States, significant numbers of homicides are also perpetrated by other means. Blunt-force injuries are produced by a variety of objects, including hands and feet and many different weapons. Some of these objects produce distinctive patterns of injury of potential evidentiary value. This paper presents a series of 20 consecutive blunt-force homicides in adults. Seventy percent (14 cases) of the victims were men. Thirty percent (six cases) followed an argument or altercation. A number of the weapons used were "weapons of opportunity" seized in the course of the incidents. Sixty-nine percent (nine cases) of known assailants were acquainted with their victims. Few characteristic patterned injuries were seen. Not surprisingly, craniocerebral trauma was the most common cause of death. One half (10 cases) the victims survived their assaults for varying periods of time. Homicides due to blunt-force injury still pose a significant challenge for the forensic pathologist, who must obtain a complete and accurate history of the fatal incident, interpret patterns of injury and other findings at autopsy, and correlate all of the findings to make an accurate ruling of the cause and manner of death. 相似文献
200.
The rare event of a corpse immersed in glacier ice becoming exposed on a glacier surface is closely connected with the glaciological conditions at the scene and the site of the accident. Provided that the time since death is known, certain questions relative to the circumstances of a mountain accident can only be answered by considering glaciological aspects. How the scene of an accident can be reconstructed by inference from the site of discovery is discussed by means of three exemplary cases that occurred on Tyrolean glaciers (Austria) during the past 40 years: (1) Two corpses were discovered close above the equilibrium line in the accumulation area after 25 years. The two victims had fallen down a rock face after the breaking off of a cornice and had come to rest in the uppermost part of the accumulation area. (2) A victim was discovered in the lower ablation area 8 years after falling down a crevasse in the middle part of the ablation area. (3) A female alpinist was discovered at the very end of the glacier after 29 years; it was concluded that the accident must have happened in the accumulation area. 相似文献