全文获取类型
收费全文 | 19613篇 |
免费 | 1430篇 |
专业分类
各国政治 | 971篇 |
工人农民 | 704篇 |
世界政治 | 1516篇 |
外交国际关系 | 647篇 |
法律 | 13294篇 |
中国共产党 | 3篇 |
中国政治 | 206篇 |
政治理论 | 3541篇 |
综合类 | 161篇 |
出版年
2020年 | 430篇 |
2019年 | 452篇 |
2018年 | 547篇 |
2017年 | 635篇 |
2016年 | 647篇 |
2015年 | 577篇 |
2014年 | 580篇 |
2013年 | 2177篇 |
2012年 | 479篇 |
2011年 | 638篇 |
2010年 | 705篇 |
2009年 | 669篇 |
2008年 | 498篇 |
2007年 | 455篇 |
2006年 | 551篇 |
2005年 | 417篇 |
2004年 | 426篇 |
2003年 | 447篇 |
2002年 | 358篇 |
2001年 | 739篇 |
2000年 | 636篇 |
1999年 | 539篇 |
1998年 | 271篇 |
1997年 | 223篇 |
1996年 | 206篇 |
1995年 | 223篇 |
1994年 | 240篇 |
1993年 | 210篇 |
1992年 | 352篇 |
1991年 | 359篇 |
1990年 | 337篇 |
1989年 | 351篇 |
1988年 | 348篇 |
1987年 | 322篇 |
1986年 | 351篇 |
1985年 | 352篇 |
1984年 | 347篇 |
1983年 | 326篇 |
1982年 | 234篇 |
1981年 | 187篇 |
1980年 | 200篇 |
1979年 | 232篇 |
1978年 | 159篇 |
1977年 | 137篇 |
1976年 | 127篇 |
1975年 | 121篇 |
1974年 | 124篇 |
1973年 | 107篇 |
1972年 | 104篇 |
1971年 | 102篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
This article looks at the newly-issued JCAHO standards and their increased focus on patient safety in performance standards for healthcare organizations. As part of these standards, hospitals are required to inform patients of outcomes of care, including unanticipated outcomes. This article examines this requirement and suggests varying interpretations of it. After looking at the current legal and ethical standards requiring disclosure of errors or negligent acts, the article suggests that hospitals are faced with many difficulties in implementing the standard. Specifically, the article argues that more details are necessary regarding what events must be reported and what hospitals are required to do when members of the medical staff refuse to inform patients of medical error. 相似文献
992.
We show that temporal, spatial, and dyadic dependencies amongobservations complicate the estimation of covariance structuresin panel databases. Ignoring these dependencies results in covarianceestimates that are often too small and inferences that may bemore confident about empirical patterns than is justified bythe data. In this article, we detail the development of a nonparametricapproach, window subseries empirical variance estimators (WSEV),that can more fully capture the impact of these dependencieson the covariance structure. We illustrate this approach ina simulation as well as with a statistical model of internationalconflict similar to many applications in the international relationsliterature. 相似文献
993.
994.
With increasing frequency, relatively small, fragmentary evidence thought to be osseous or dental tissue of human origin is submitted to the forensic laboratory for DNA analysis with the request for positive identification. Prior to performing DNA analysis, however, it is prudent to first perform a presumptive test or "screen" to determine whether the questioned material may be eliminated from further consideration. When material is shown not to be consistent with bone/teeth, DNA testing is not performed. When such determinations cannot be made from gross morphological features, elemental analysis can be indicative. This presumptive test is made possible by applying scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) in conjunction with an X-ray spectral database recently developed by the FBI laboratory. This database includes spectra for many different materials including known examples of bone and tooth from many different contexts and representing the full range of taphonomic conditions. Results of SEM/EDS analysis of evidence can be compared to these standards to determine if they are consistent with bone and/or tooth and, if not, then what the material might represent. Analysis suggests that although the proportions and amounts of calcium and phosphorus are particularly important in differentiating bone and tooth from other materials, other minor differences in spectral profile can also provide significant discrimination. Analysis enables bone and tooth to be successfully distinguished from other materials in most cases. Exceptions appear to be ivory, mineral apatite, and perhaps some types of corals. 相似文献
995.
The concentrations of antimony, copper, tin, arsenic, silver, bismuth, and cadmium in lead alloys produced by two smelters and one ammunition manufacturer were determined using inductively coupled plasma-atomic emission spectrometry. These element concentrations were used to measure the variations in composition of lead products that result from various processes involved in the manufacture of lead projectiles. In general, when a pot containing molten lead is used to cast a number of objects, these objects are similar, although not necessarily analytically indistinguishable in their elemental compositions. In each subsequent step in the processing of lead at the smelter and at the ammunition manufacturer, the size of an individual homogeneous melt of lead decreases as more distinct compositions are formed as a result of remelting and mixing of sources, including lead scrap. The ammunition manufacturer in this study produced at least 10 compositionally distinguishable groups of bullet wire in a 19.7-h period. The largest group could potentially be used to produce a maximum of 1.3 million compositionally indistinguishable 40 grain bullets. 相似文献
996.
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
997.
Mitochondrial DNA analysis of a maggot crop can identify the corpse a maggot has been feeding on. Analysis of the crop could be useful in a criminal investigation if maggots are found at a suspected crime scene in the absence of a body, or if there is a question of whether a maggot used in postmortem interval estimations moved onto the corpse from another food source. Such analysis can also resolve a chain of custody dispute if it has been suggested that larval samples have been switched. When recovering DNA from a maggot crop, the analyst must be careful to avoid external contamination. We investigated the effects of three simple wash methods developed to reduce external contamination. Maggots raised on pig liver and intentionally contaminated with cow blood were washed using water, 20% bleach, or a solution containing the enzyme DNase. Only washing the maggots in 20% bleach reduced the amount of vertebrate DNA amplified from the maggots' exteriors. No wash method affected the ability to recover DNA from the maggot crops. 相似文献
998.
999.
Torres MC Osuna E Pérez-Cárceles MD Gómez-Zapata M Luna A 《The American journal of forensic medicine and pathology》2002,23(2):155-158
The authors evaluated the usefulness of the postmortem biochemical analysis of ionic ratios in different parts of the heart and their relation to cardiac damage caused by chest trauma, as observed by anatomopathologic study. Fifty-nine 59 cases were studied, selected from routine necropsies, and samples were taken from different sites of cardiac tissue. The cause of death was trauma in 40 cases and nontraumatic causes in 19 cases. The object of this study was to analyze the levels of Na+, K+, Ca+2, Mg+2, and Zn+2 in different zones of the heart, and the relationship between intracellular and extracellular ion ratios and the different causes of death and any anatomopathologic alterations observed. The biochemical tests revealed a possible relation between the ionic values and cause of death. Alterations in cell membrane permeability and corresponding modification of the ionic ratios were produced earlier than histologic alterations, which need longer to establish themselves whether or not they follow a traumatic process. 相似文献
1000.
Soares-Vieira JA Billerbeck AE Pinto EM Iwamura ES Bilharinho de Mendonça B Otto PA 《The American journal of forensic medicine and pathology》2002,23(2):186-190
Gene and genotype frequencies in relation to the D3S1358, vWA, FGA, TH01, TPOX, CSF1PO, D5S818, D13S317, and D7S820 loci were determined in a sample of 290 unrelated individuals (204 Caucasians and 86 mulattoes) living in the city of S?o Paulo, Brazil. The sex test Amelogenin was also performed in all subjects from our sample, revealing the expected sex in all instances. Allele frequency data obtained from the analysis of these samples were in the usual range of other population groups with similar racial background. In the sample of Caucasian individuals, panmictic proportions were ruled out in relation to TPOX and CSF1PO loci, but only in the latter was the overall frequency of heterozygotes significantly less than expected. In the sample of mulattoes, Hardy-Weinberg proportions were rejected in relation to FGA and CSF1PO loci, but in no instance were the overall numbers of heterozygotes different from the corresponding expected ones under panmixia. Taking into account all this and also the number of tests performed, the degree of genetic heterogeneity of Brazilian populations, and the critical level reached by the significant results (1% < alpha<5%), the departures from panmixia here observed can be considered to be negligible in altering significantly biologic relationship odds calculated under the assumption of random matings. 相似文献