全文获取类型
收费全文 | 634篇 |
免费 | 25篇 |
专业分类
各国政治 | 35篇 |
工人农民 | 46篇 |
世界政治 | 64篇 |
外交国际关系 | 16篇 |
法律 | 288篇 |
中国政治 | 17篇 |
政治理论 | 190篇 |
综合类 | 3篇 |
出版年
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 17篇 |
2018年 | 16篇 |
2017年 | 15篇 |
2016年 | 19篇 |
2015年 | 12篇 |
2014年 | 19篇 |
2013年 | 105篇 |
2012年 | 18篇 |
2011年 | 30篇 |
2010年 | 13篇 |
2009年 | 10篇 |
2008年 | 22篇 |
2007年 | 16篇 |
2006年 | 25篇 |
2005年 | 25篇 |
2004年 | 23篇 |
2003年 | 16篇 |
2002年 | 18篇 |
2001年 | 16篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1998年 | 7篇 |
1997年 | 11篇 |
1996年 | 11篇 |
1995年 | 10篇 |
1994年 | 10篇 |
1993年 | 12篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1979年 | 10篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1971年 | 3篇 |
1969年 | 3篇 |
1968年 | 4篇 |
1967年 | 5篇 |
1943年 | 2篇 |
排序方式: 共有659条查询结果,搜索用时 15 毫秒
31.
Lewis RJ Huffine EF Chaturvedi AK Canfield DV Mattson J 《Journal of forensic sciences》2000,45(4):898-901
During fatal aviation accident investigations, biosamples from the victims are submitted to the FAA Civil Aeromedical Institute (CAMI) for drug analysis. In the process of one such analysis by CAMI, an unknown substance was found in a urine sample. Simultaneous screening by thin layer chromatography (TLC) and gas chromatography/FID (GC/FID) suggested the presence of pseudoephedrine. A subsequent routine confirmation analysis of a separate urine aliquot by GC Fourier transform infrared (GC/FTIR) and GC mass spectrometry (GC/MS) indicated that the retention times of the unknown substance matched with those of pseudoephedrine. However, its infrared and mass spectra were different--the -OH and -NH groups were missing, a C-O-C group was present, and the molar mass was 12 atomic mass units (amu) more than that of pseudoephedrine. A subsequent literature search suggested that ephedrine-like amines react with aldehydes to form oxazolidines. Therefore, the 12-amu increase could be accounted for by condensation of pseudoephedrine with formaldehyde. Since this aldehyde is present in various grades of methanol and ethyl acetate, and these solvents were used during the solid-phase extraction, 3,4-dimethyl-5-phenyl-1,3-oxazolidine was synthesized by using (+)-pseudoephedrine HCl and formaldehyde. The analytical findings of the synthesized compound were consistent with those of the unknown interfering substance, confirming that it was the oxazolidine. Aldehyde contaminants in solvents or specimens can transform drugs of interest and may result in misidentification of a compound originally present in specimens. Therefore, chemicals used in analyses should be of the highest available purity, and a multi-analytical approach should be adopted to maintain a high degree of quality assurance. 相似文献
32.
Morphine-3-D glucuronide stability in postmortem specimens exposed to bacterial enzymatic hydrolysis
Carroll FT Marraccini JV Lewis S Wright W 《The American journal of forensic medicine and pathology》2000,21(4):323-329
Medical examiners frequently rely on the finding of free morphine present in postmortem specimens to assist in certifying deaths associated with narcotics. In vitro hydrolysis of morphine-3-D glucuronide (M3DG) to free morphine was studied using variable specimen pH, initial degree of specimen putrefaction, storage temperature and time, and the effectiveness of sodium fluoride (NaF) preservation. Reagent M3DG was added to opiate-free fresh blood and urine and to autopsy-derived blood specimens. Reagent bovine glucuronidase was also added to certain specimens. Freshly collected and refrigerated NaF-preserved blood produced minimal free morphine, whereas four of five autopsy blood specimens produced free morphine from M3DG. Increased storage time, temperature, and initial degree of putrefaction resulted in greater free morphine generation despite the absence of viable bacteria. Hydrolysis occurring during specimen storage can generate free morphine from M3DG and may result in erroneous conclusions in certifying narcotic deaths. 相似文献
33.
Shelby Lewis 《Women's studies international forum》1985,8(2):117-120
Thirty Black women activists within different age categories, from varied educational and occupational backgrounds, and representing Black women's organizations from different regions of the U.S. were interviewed to determine their views on the meaning and effect of the UN Decade for Women on the lives of Black American women. Their responses to questions about the Decade indicate that the masses of Black women are poorly informed or totally uninformed about the UN Decade for Women. And, among that segment of the Black female population which is well informed about the Decade, positive views on the benefits of the Decade for Black women correlate strongly with employment in a national women's organization or governmental agency dealing with women's issues, and personal involvement in UN Conferences. Many Black women feel that the opportunity to network with third-world women is the major benefit that Black American women gained from the Decade. They also feel that American racism and class bias effectively prevent equitable implementation of a national plan of action to improve the status of women in the United States. 相似文献
34.
35.
36.
37.
38.
Johnson RD Lewis RJ Canfield DV Dubowski KM Blank CL 《Journal of forensic sciences》2005,50(3):670-675
Specimens from fatal aviation accident victims are submitted to the FAA Civil Aerospace Medical Institute for toxicological analysis. During toxicological evaluations, ethanol analysis is performed on all cases. Care must be taken when interpreting a positive ethanol result due to the potential for postmortem ethanol formation. Several indicators of postmortem ethanol formation exist; however, none are completely reliable. The consumption of ethanol has been shown to alter the concentration of two major serotonin metabolites, 5-hydroxytryptophol (5-HTOL) and 5-hydroxyindole-3-acetic acid (5-HIAA). While the 5-HTOL/5-HIAA ratio is normally very low, previous studies using living subjects have demonstrated that the urinary 5-HTOL/5-HIAA ratio is significantly elevated for 11-19 h after acute ethanol ingestion. Recently, our laboratory developed and validated an analytical method for the simultaneous determination of both 5-HTOL and 5-HIAA in forensic urine samples using a simple liquid/liquid extraction and LC/MS/MS and LC/MS/MS/MS. In this previous work a 15 pmol/nmol serotonin metabolite ratio cutoff was established in postmortem urine, below which it could be conclusively determined that no recent antemortem ethanol consumption had occurred. In the current study this newly validated analytical method was applied to five ethanol-positive aviation fatalities where the origin of the ethanol present could not previously be conclusively determined. In four of the five cases examined the detected ethanol was demonstrated to be present due to postmortem microbial formation, and not consumption, even though some indication of ethanol consumption may have been present. 相似文献
39.
40.
Sharma AN Nelson LS Hoffman RS 《The American journal of forensic medicine and pathology》2004,25(2):156-158
The neurologic manifestations of thallium poisoning include a severely painful ascending peripheral neuropathy, autonomic dysfunction, cranial nerve abnormalities, and a toxic encephalopathy. Although thallium has a short half-life, these neurologic manifestations commonly progress, even as the blood concentration of thallium decreases. This suggests either that thallium persists in neuronal tissues or that it initiates an injury cascade that takes time to fully manifest. As the latter mechanism is consistent with many toxin exposures, the concept of a central nervous system reservoir for thallium is often discounted. A recent case provided a unique opportunity to evaluate this possibility. A 48-year-old man was acutely and chronically thallium poisoned by his common-law wife. During his initial exposures, only gastrointestinal symptoms manifested. Following an acute ingestion, hospitalization was required. Over 3 days, his symptoms rapidly progressed from a severely painful neuropathy to slurred speech, ptosis, confusion, coma, respiratory insufficiency, and death. Because of considerations of alternative diagnoses, 2 lumbar punctures were performed, one on admission and another on the day of his death. Serum thallium concentrations obtained from stored blood samples were paired with spinal fluid concentrations from the same days. On day 1, serum and spinal fluid concentrations were 8700 mu/L and 1200 mu/L, respectively. On day 3, although the serum concentration had fallen to 7200 mu/L, the spinal fluid concentration had increased to 2100 mu/L. This case provides evidence to support the hypothesis that thallium distributes into the central nervous system more slowly than the blood compartment, and this may in part account for the progression of neurologic findings in the setting of decreasing serum concentrations. 相似文献