全文获取类型
收费全文 | 5407篇 |
免费 | 1056篇 |
专业分类
世界政治 | 2篇 |
外交国际关系 | 1篇 |
法律 | 6390篇 |
中国政治 | 25篇 |
政治理论 | 8篇 |
综合类 | 37篇 |
出版年
2024年 | 22篇 |
2023年 | 81篇 |
2022年 | 69篇 |
2021年 | 86篇 |
2020年 | 279篇 |
2019年 | 276篇 |
2018年 | 291篇 |
2017年 | 404篇 |
2016年 | 517篇 |
2015年 | 369篇 |
2014年 | 484篇 |
2013年 | 497篇 |
2012年 | 426篇 |
2011年 | 573篇 |
2010年 | 458篇 |
2009年 | 457篇 |
2008年 | 362篇 |
2007年 | 327篇 |
2006年 | 293篇 |
2005年 | 54篇 |
2004年 | 32篇 |
2003年 | 34篇 |
2002年 | 26篇 |
2001年 | 16篇 |
2000年 | 7篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 11篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有6463条查询结果,搜索用时 15 毫秒
891.
Collins M Heagney A Cordaro F Odgers D Tarrant G Stewart S 《Journal of forensic sciences》2007,52(4):898-903
Five 44 gallon drums labeled as glycidyl methacrylate were seized by the Australian Customs Service and the Australian Federal Police at Port Botany, Sydney, Australia, in December 2004. Each drum contained a white, semisolid substance that was initially suspected to be 3,4-methylenedioxymethylamphetamine (MDMA). Gas chromatography-mass spectroscopy (GC/MS) analysis demonstrated that the material was neither glycidyl methacrylate nor MDMA. Because intelligence sources employed by federal agents indicated that this material was in some way connected to MDMA production, suspicion fell on the various MDMA precursor chemicals. Using a number of techniques including proton nuclear magnetic resonance spectroscopy ((1)H NMR), carbon nuclear magnetic resonance spectroscopy ((13)C NMR), GC/MS, infrared spectroscopy, and total synthesis, the unknown substance was eventually identified as methyl 3-[3',4'(methylenedioxy)phenyl]-2-methyl glycidate. The substance was also subjected to a published hydrolysis and decarboxylation procedure and gave a high yield of the MDMA precursor chemical, 3,4-methylenedioxyphenyl-2-propanone, thereby establishing this material as a "precursor to a precursor." 相似文献
892.
Methods to estimate adult age from observations of skeletal elements are not very accurate and motivate the development of better methods. In this article, we test recently published method based on the acetabulum and Bayesian inference, developed using Coimbra collection (Portugal). In this study, to evaluate its utility in other populations, this methodology was applied to 394 specimens from four different documented Western European collections. Four strategies of analysis to estimate age were outlined: (a) each series separately; (b) on Lisbon collection, taken as a reference Coimbra collection; (c) on Barcelona collection, taken as a reference both Portuguese collections; and (d) on London collection taken as reference the three Iberian collections combined. Results indicate that estimates are accurate (83-100%). As might be expected, the least accurate estimates were obtained when the most distant collection was used as a reference. Observations of the fused acetabulum can be used to make accurate estimates of age for adults of any age, with less accurate estimates when a more distant reference collection is used. 相似文献
893.
Cameriere R Ferrante L Belcastro MG Bonfiglioli B Rastelli E Cingolani M 《Journal of forensic sciences》2007,52(5):1151-1155
Changes in the size of the pulp canal, caused by apposition of secondary dentine, are the best morphometric parameters for estimating age by X-rays. The apposition of secondary dentine is the most frequently used method for age estimation in adult subjects. In two previous papers, we studied the application of the pulp/tooth area ratio by peri-apical X-rays as an indicator of age at death. The aim of the present study was to test the accuracy of age evaluation by combined analysis of labio-lingual and mesial peri-apical X-rays of lower and upper canines. A total of 200 such X-rays were assembled from 57 male and 43 female skeletons of Caucasian origin, aged between 20 and 79 years. For each skeleton, dental maturity was evaluated by measuring the pulp/tooth area ratio according to labio-lingual and mesial X-rays on upper (x(1), x(2)) and lower (x(3), x(4)) canines. Very good agreement was found between intra-observer measurements. Statistical analysis showed that all variables x(1), x(2), x(3), and x(4) and the first-order interaction between x(1) and x(3) contributed significantly to the fit, so that they were included in the regression model, yielding the following regression formula: Age = 120.737 - 337.112x(1) - 79.709x(2) - 364.534x(3) - 65.655x(4) + 1531.918x(1)x(3) . The residual standard error of estimated ages was 3.62 years, with 94 degrees of freedom, and the median of the residuals was -0.155 years, with an interquartile range of 4.96 years. The accuracy of the method was ME = 2.8 years, where ME is the mean prediction error. The model also explained 94% of total variance (R(2) = 0.94). 相似文献
894.
Simic M Draskovic D Stojiljkovic G Vukovic R Budimlija ZM 《Journal of forensic sciences》2007,52(5):1182-1185
The "humane killer" or captive-bolt gun, is the tool/weapon widely used in meat industry and private farmer households for slaughtering animal stock. Out of 17,250 autopsies performed at the Institute of Forensic Medicine in Novi Sad during the 15-year period (1991-2005), 29 cases of suicides and two homicides were committed by captive-bolt pistols. Wounds inflicted by captive-bolt guns have specific morphological features, distinctive from wounds made by other kinds of hand firearms. Selected features of the captive-bolt wounds (punched round entrance and a double pattern of smoke soiling) depend on distance and angle of instrument at the time of firing. Autopsy findings were compared with an experimental model consisting of 20 domestic pigs. Obtained results confirmed that the appearance of the entrance hole and soot deposits, along with differences in shape, location, extent, and density of soot blackening, could be useful in identification of weapon, direction of discharge, shooting distance, and angle of the muzzle to the frontal and sagittal planes of the head at the moment of fire. 相似文献
895.
Traditional forensic soil comparisons are performed via physical and/or chemical examinations of color, texture, and mineral content, leaving any organic- or water-soluble fractions unexamined. This study uses high-performance liquid chromatography (HPLC) and ion chromatography (IC) to assess the qualitative and quantitative variation in these fractions of soil. Soil samples (n=120) were collected over the course of 3 weeks from urban, suburban, and rural locations in and around Lansing, MI. Additional samples from six of these locations (two urban, two suburban, and two rural) were collected once a week for 10 weeks for temporal analysis. Nine additional samples, equally spaced over a 1 m(2) grid, from these same six locations were collected for spatial analyses. Qualitative and quantitative analysis of the resultant chromatograms separated the 120 samples into 10 groups by HPLC and 23 groups by IC. This study shows that using HPLC and IC to analyze the organic- and water-soluble fractions of soil can successfully discriminate samples. Quantitative analysis of the results eliminates some false inclusions by providing further differentiation of samples. The results of this study indicate that adding HPLC and IC analyses to traditional forensic soil analysis schemes can improve overall sample differentiation. The methods used in this study were also able to detect both qualitative and quantitative variations in soil over a relatively small geographic area. This demonstration of soil heterogeneity underscores the importance of the collection of a representative known sample population when assessing a forensic soil comparison. Significant temporal variation was also demonstrated over the course of 10 weeks of sampling; however, samples were found to be consistent over shorter periods of time. Baseline levels of inorganic anions were determined via IC; these levels may be useful in assessing the significance of anions detected in soil from cases involving low explosives. 相似文献
896.
Carol K. Lee M.D. F.R.C.P.C. Sarah L. Lathrop D.V.M. Ph.D. 《Journal of forensic sciences》2010,55(1):100-103
Abstract: We retrospectively reviewed autopsy records at a statewide medical examiner's office in order to identify and characterize deaths due to child abuse. In a 6-year period in New Mexico, the medical examiner investigated 45 deaths determined to be child abuse-related. Decedents were predominantly male (68.9%), Hispanic White (53.3%), and all were 5 years of age or younger, with a median age of 1 year. Head injuries were the most common cause of death (44.4%), followed by battered baby syndrome (15.6%). Relatives were involved as alleged perpetrators in 80% of the cases, with the father most often implicated (36.1% of cases), and 88.9% of child abuse injuries resulting in death occurred in the family's residence. Toxicology was positive in 26.7% of cases, but only two cases had substances of abuse present. Information on risk factors such as prematurity, parental age, and history of abuse was also collected. 相似文献
897.
Abstract: In 1992, Tzidony and Ravreby presented a confidence interval for the total weight of a seizure of illicit drugs present in a population. Their approach has subsequently been applied by several researchers in the field. The formula on which their approach is based does, however, not fully take into account the proportion of drug units found in the sample. In this paper, a modification is presented that consistently uses the correct sample size in all terms of the confidence interval, based on the proportion of drug units found in the sample. The effective sample size is smaller than the original sample size, and this should consequently be accounted for in the estimation of the standard error and in the corresponding t -distribution. The new confidence interval is again based on the assumption that the proportion of drug units in the population is known after sampling. 相似文献
898.
Eila Repo‐Tiihonen M.D. Ph.D. Jari Tiihonen M.D. Ph.D. Nina Lindberg M.D. Ph.D. Ghitta Weizmann‐Henelius Ph.D. Hanna Putkonen M.D. Ph.D. Helinä Häkkänen Ph.D. 《Journal of forensic sciences》2010,55(1):116-120
Abstract: Preventive interventions early in life are likely to lower the risk of intergenerational transmission of criminal behavior. We investigated if psychopathy among homicidal offenders is associated with criminal offending among the offenders’ offspring. The basic sample consisted of consecutive Finnish homicide offenders (during 1995–2004) who had been subjected to a forensic psychiatric examination and rated for a file‐based PCL‐R, and their offspring. Criminal behavior among both genders of the offspring was more common than in the general population. In general, the offspring’s crimes against others (e.g., threat, intimidation, deprivation of freedom, breach of domicile) were associated with their parent’s psychopathy. A grandfather’s major mental disorder was associated with a high rate of crime committed by the offspring. Especially, the sons of male psychopathic homicidal offenders had the highest rate of committing crimes, which was often expressed as vandalism. However, both genders of offspring seem to require special preventive programs to ameliorate these problems. 相似文献
899.
Arzu Akcay Turan M.D. ; Ferah Anik Karayel M.D. ; Elif Akyildiz M.D. ; Isil Pakis M.D. ; Ibrahim Uzun M.D. ; Kagan Gurpinar M.D. ; Umit Atlms M.D. ; Ziya Kir M.D. 《Journal of forensic sciences》2010,55(1):82-84
Abstract: Nonpenetrating chest trauma with injury to the heart and aorta has become increasingly common, particularly as a result of rapid deceleration in high-speed vehicular accidents, over the past 2–3 decades. The high mortality rate of cardiac injuries and possible late onset complications make blunt cardiac injuries an important challenging point for legal medicine. One hundred and ninety cases with blunt cardiac injuries in a period of 3 years were analyzed retrospectively in terms of patterns of cardiac injury, survival times, and demographic profiles of the cases in this study. 相似文献
900.
Alex J. Goddard M.Chem. ; A. Robert Hillman D.Phil. ; John W. Bond D.Phil. 《Journal of forensic sciences》2010,55(1):58-65
Abstract: The Atomic Force Microscope (AFM) is capable of imaging fingerprint ridges on polished brass substrates at an unprecedented level of detail. While exposure to elevated humidity at ambient or slightly raised temperatures does not change the image appreciably, subsequent brief heating in a flame results in complete loss of the sweat deposit and the appearance of pits and trenches. Localized elemental analysis (using EDAX, coupled with SEM imaging) shows the presence of the constituents of salt in the initial deposits. Together with water and atmospheric oxygen—and with thermal enhancement—these are capable of driving a surface corrosion process. This process is sufficiently localized that it has the potential to generate a durable negative topographical image of the fingerprint. AFM examination of surface regions between ridges revealed small deposits (probably microscopic "spatter" of sweat components or transferred particulates) that may ultimately limit the level of ridge detail analysis. 相似文献