全文获取类型
收费全文 | 20995篇 |
免费 | 583篇 |
专业分类
各国政治 | 916篇 |
工人农民 | 812篇 |
世界政治 | 1717篇 |
外交国际关系 | 698篇 |
法律 | 12577篇 |
中国共产党 | 3篇 |
中国政治 | 101篇 |
政治理论 | 4552篇 |
综合类 | 202篇 |
出版年
2020年 | 260篇 |
2019年 | 305篇 |
2018年 | 399篇 |
2017年 | 476篇 |
2016年 | 498篇 |
2015年 | 368篇 |
2014年 | 407篇 |
2013年 | 2101篇 |
2012年 | 513篇 |
2011年 | 525篇 |
2010年 | 429篇 |
2009年 | 460篇 |
2008年 | 551篇 |
2007年 | 568篇 |
2006年 | 548篇 |
2005年 | 490篇 |
2004年 | 499篇 |
2003年 | 510篇 |
2002年 | 471篇 |
2001年 | 791篇 |
2000年 | 739篇 |
1999年 | 603篇 |
1998年 | 341篇 |
1997年 | 287篇 |
1996年 | 238篇 |
1995年 | 250篇 |
1994年 | 287篇 |
1993年 | 259篇 |
1992年 | 413篇 |
1991年 | 435篇 |
1990年 | 410篇 |
1989年 | 417篇 |
1988年 | 384篇 |
1987年 | 403篇 |
1986年 | 418篇 |
1985年 | 423篇 |
1984年 | 353篇 |
1983年 | 383篇 |
1982年 | 299篇 |
1981年 | 277篇 |
1980年 | 218篇 |
1979年 | 288篇 |
1978年 | 205篇 |
1977年 | 170篇 |
1976年 | 161篇 |
1975年 | 155篇 |
1974年 | 185篇 |
1973年 | 166篇 |
1972年 | 145篇 |
1970年 | 121篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
961.
Comparing skeletal structures between antemortem and postmortem chest radiographs is widely used by forensic specialists from many disciplines to positively identify unknown decedents. However, validity assessments of this method have been fairly limited. This study had three objectives: 1) to quantify the reliability of ante- and postmortem chest radiograph comparison for decedent identification; 2) to identify useful radiologic features supporting decedent identification; and 3) to recognize sources of error in decedent identification related to use of comparative radiographs. A forensic pathologist, a forensic anthropologist, and two radiologists participated in the study. Our results showed that chest radiograph comparisons proved reliable, if basic decedent information was provided, and antemortem and postmortem radiographs were adequately positioned and exposed. A "morphological approach" using normal anatomical structures for comparison may provide the most efficient method for accurate identification. 相似文献
962.
Validation of a 16-locus fluorescent multiplex system 总被引:24,自引:0,他引:24
Krenke BE Tereba A Anderson SJ Buel E Culhane S Finis CJ Tomsey CS Zachetti JM Masibay A Rabbach DR Amiott EA Sprecher CJ 《Journal of forensic sciences》2002,47(4):773-785
STR multiplexes have been indispensable for the efficient genotyping of forensic samples. The PowerPlex 16 System contains the coreCODIS loci, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D21S11, CSF1PO, FGA, THOI, TPOX, vWA, the sex determinant locus, amelogenin, and two pentanucleotide STR loci, Penta D and Penta E. This multiplex satisfies the locus requirements for most national databases and is the most efficient currently available system due to its single PCR amplification. To provide the groundwork for judicial acceptance, including the publication of primer sequences, and to evaluate laboratory-to-laboratory variation, a developmental validation for casework on this commercially available system was performed in 24 laboratories and produced the following conclusions. Amplification was reliable on a variety of thermal cyclers and product could be analyzed on either an ABI PRISM 310 Genetic Analyzer or an ABI PRISM 377 DNA Sequencer. Genotyping using single source samples was consistent between 0.25 and 2 ng of input DNA template with a few laboratories obtaining complete genotypes at 0.0625 ng. However, heterozygote allele imbalance (<60% peak height balance) caused by stochastic effects was observed at a rate of 13% with 0.125 ng DNA and 22% at 0.0625 ng DNA. Mixture analyses were done using a total of 1 ng of DNA template. Most alleles were detected in mixtures of 4 to 1 and some minor alleles were detected in mixtures of 19 to 1. Optimum amplification cycle number was dependent on the sensitivity of the detection instrument used and could also be adjusted to accommodate larger amounts of DNA on solid supports such as FTA paper. Reaction conditions including volume, annealing temperature, and concentrations of primer, AmpliTaq Gold, and magnesium were shown to be optimal yet robust enough to withstand moderate variations without affecting genotype analysis. Environmental, matrix and standard source analyses revealed an ability to obtain complete genotypes in all sample types except those exposed to 80 degrees C for 12-48 days. Finally, comparison of genotype results from the PowerPlex 16 System with other commercially available systems on non-probative reference and forensic samples showed consistent results. 相似文献
963.
Assessment of the role of air bag deployment in injury causation in a crash of any severity requires analysis of occupant, vehicle, and impact data. The potential injurious role of an air bag is independent of crash severity and is more obvious in minor collisions, particularly those involving "out-of-position" occupants. Factors such as occupant height and other constitutional and medical factors, intoxication, age, type, and proper use of other restraint systems, pre-impact braking and multiple impacts can contribute to an occupant being "out-of-position." Two injury mechanisms are described in out-of-position occupants: "punch-out" when the individual covers the air bag module before deployment and "membrane-force" when the occupant contacts a partly deployed air bag. Each mechanism is associated with injury patterns. In adults, "punch-out" can cause thoraco-abdominal trauma and "membrane-force" loading can lead to craniocervical injury. This can also occur in short-statured occupants including children subjected to both types of loading. In more severe collisions, other factors, e.g., intrusion, steering column and seatbelt loading and other occupant compartment contacts, can contribute to trauma. 相似文献
964.
965.
966.
967.
What is the best sample for determining the early postmortem period by on-the-spot flow cytometry analysis? 总被引:8,自引:0,他引:8
Di Nunno N Costantinides F Cina SJ Rizzardi C Di Nunno C Melato M 《The American journal of forensic medicine and pathology》2002,23(2):173-180
The level of degradation of DNA as a means for determining the time of death has been proposed as a valid adjunct to the classic thanatochronologic methods. The twofold aim of this work was to determine which organ might reveal both a correlation between the percentage of degradation of the DNA and the time lapse since death, and would be easiest to sample and yield the most reproducible results even in technically unfavorable situations such as on-the-spot investigations at the scene of death. A comparison of the spleen, blood, and liver showed that hepatic tissue best meets these specific needs because it shows a virtually linear correlation between the time elapsed since death and the level of degradation of the DNA, and it can easily be sampled at the scene of death by use of a common biopsy needle. 相似文献
968.
Childhood sporting deaths 总被引:1,自引:0,他引:1
Byard RW James RA Gilbert JD 《The American journal of forensic medicine and pathology》2002,23(4):364-367
969.
The authors describe three accidental deaths resulting from occupational hazards involving environmental gas alterations. One involved the displacement of oxygen caused by leakage of liquid nitrogen during the installation of a magnetic resonance imaging system. Two involved elevated environmental carbon dioxide concentrations: dry ice sublimation in a walk-in refrigerator in a research laboratory, and activation of a carbon dioxide fire alarm-extinguisher system by a woman locked in a bank vault. The autopsy findings, scene investigations, and certifications of these deaths, as related to the mechanisms of death, are discussed. 相似文献
970.
Personal identification based on radiographic vertebral features 总被引:4,自引:0,他引:4
Personal identification of human remains constitutes about 10% of the normal caseload of any forensic medicine practice. Identification can be achieved by a variety of methods, one of which is the comparison of antemortem and postmortem radiographs. There are numerous accounts of cranial and dental radiographic features useful for identification, whereas the availability of postcranial radiographs and especially plates that depict the vertebral column is less widespread among the forensic community. The authors here review the various vertebral features instrumental in positive identification that can be identified on radiographs of the spine. 相似文献