首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4706篇
  免费   146篇
各国政治   150篇
工人农民   213篇
世界政治   311篇
外交国际关系   177篇
法律   3134篇
中国政治   24篇
政治理论   820篇
综合类   23篇
  2023年   37篇
  2021年   26篇
  2020年   57篇
  2019年   76篇
  2018年   103篇
  2017年   97篇
  2016年   115篇
  2015年   68篇
  2014年   89篇
  2013年   411篇
  2012年   114篇
  2011年   135篇
  2010年   94篇
  2009年   120篇
  2008年   117篇
  2007年   116篇
  2006年   122篇
  2005年   82篇
  2004年   102篇
  2003年   108篇
  2002年   85篇
  2001年   208篇
  2000年   207篇
  1999年   149篇
  1998年   61篇
  1997年   60篇
  1996年   54篇
  1995年   52篇
  1994年   59篇
  1993年   52篇
  1992年   118篇
  1991年   106篇
  1990年   132篇
  1989年   121篇
  1988年   136篇
  1987年   129篇
  1986年   100篇
  1985年   106篇
  1984年   80篇
  1983年   71篇
  1982年   52篇
  1981年   47篇
  1980年   40篇
  1979年   50篇
  1978年   36篇
  1976年   30篇
  1975年   28篇
  1974年   39篇
  1973年   28篇
  1970年   27篇
排序方式: 共有4852条查询结果,搜索用时 15 毫秒
301.
An ingestion of an unknown quantity of Harmomed (dothiepin and diazepam) capsules in a suicide is described. The authors report a new and fast method of analysing and determining the dothiepin concentration in postmortem specimens. Quantitation of dothiepin, and its metabolite desmethyldothiepin was performed by ethyl acetate extraction from alkalinized body fluids before GC-MS analysis. The analyses were performed without any complex sample clean-up steps and with little sample material. Postmortem concentrations of dothiepin, desmethyldothiepin, diazepam and desmethyldiazepam in body fluids are given. The proposed method is a rapid procedure for analysis in cases of deliberate poisoning with the antidepressant drug dothiepin.  相似文献   
302.
Empirical studies have found that policies aimed at reducing youth access to tobacco have been successful at increasing retail compliance, but their effects on actual tobacco use are mixed. This article presents a model of youth access policies that helps explain the apparently conflicting results in the extant literature, provides a framework for future empirical studies, and suggests implications for public policy. Our model highlights the interaction of components in a well-designed policy, including sufficient compliance checks, penalties, and community involvement. It also illustrates why it will be difficult to eliminate all of youth supply. Nonretail sources, such as borrowing or stealing from parents and siblings and purchasing from older peers through black markets, are an important component of youth supply and become more important as retail access is reduced. The analysis is limited to policies that affect the retail supply of cigarettes but suggests the need for other policies that affect the demand for cigarettes, such as taxes and cessation policies, in order to further reduce youth smoking rates.  相似文献   
303.
Toluene, an abused substance in Japan, is a neurotoxic chemical that has been shown to have neurobehavioral and electrophysiological effects. In previous work, both acute and chronic effects of toluene on cells have been studied extensively. However, although glial cells are thought to play an important role in the survival of neurons in the brain, the effect of toluene on glial cell function has not yet been characterized. To elucidate this, the effect of toluene inhalation on astrocytes in rat brain was examined. Toluene exposure (1500 ppm for 4 h on 4-10 days) augmented glial fibrillary acidic protein (GFAP) immunoreactivity, particularly in the hippocampus and cerebellum. Quantitative analysis showed that toluene inhalation markedly enhanced GFAP expression in the hippocampus and cerebellum. In both regions, proliferating cell nuclear antigen (PCNA) showed no obvious changes, but glutamine synthetase (GS)-immunoreactive cells were markedly increased by toluene exposure. Thus, the elevation of GFAP expression was induced by astrocyte activation rather than by cell proliferation. If toluene exposure activates astrocytes, astrocytes may play a role in the neurophysiological changes observed in toluene intoxication. A neurotrophic factor, basic fibroblast growth factor (b-FGF) was observed immunohistochemically in the capillary vessel walls in the hippocampus and the cerebellum of toluene-intoxicated rats. Basic-FGF may have induced GFAP expression both in the hippocampus and the cerebellum. So, other neurotrophic factors may affect the difference of GFAP elevation between the hippocampus and the cerebellum. These differences may relate to neurobehavioral function of each brain part after toluene exposure.  相似文献   
304.
Several lectins were used to study the localization of glycoconjugates in brain of elderly people and patients with Alzheimer type dementia (ATD) and Down's syndrome (DS). Five kinds of degenerated or deposited materials stained clearly by lectins specific to GalNAC, Gal, Fuc, and/or Man were recognized much in ATD and DS, less in elderly peoples, in addition to the binding of the lectins to neurons. (i) Round shape deposits called corpora amylacea (CA) which consisted of various sizes of round material, existed mainly on the surface of cerebral cortex and some in white matter of the brain. They were colored by Alcian blue (AB), Aldehyde fucsin (AF) and periodic acid shiff (PAS) and weakly by Hematoxylin (H), but not by Eosin (B). They showed clear reactivity with lectins specific to GalNAC, Gal, Fuc and Gal-GalNAC. (ii) Amorphous and variform amyloid deposits existed around blood vessels in the white matter were stained by thioflavin and lectins specific to GalNAC, Gal and Fuc, but not with Man specific lectins and PAS, AB, AF and HE. (iii) Another kind of amyloid deposits which showed a similar characteristic to the previous one and were recognized mainly in white matter and independent blood vessels. These deposits were stained by thioflavin but not by PAS, AB, AF and HE and showed good reactivity with lectins specific to GalNAC, Gal, Fuc, Gal-GalNAC, Gal-GIcNAc and Man. The reactivity with lectins specific to Gal, Fuc, and Man was seen in senile plaques (iv) and neurofibrillary tangles (v). Although at present we are unable to explain the origin of these deposits, it is clear from this study that the glycoconjugates form an integral part of the degeneration in the brain. The lectin staining with GS-I is useful in the forensic pathology to diagnose brain disorders at postmortem examination, since these lectin were able to detect five types of degeneration changes and/or deposits.  相似文献   
305.
Forensic wound examination   总被引:15,自引:0,他引:15  
  相似文献   
306.
Papillary fibroelastoma is a rare benign tumor, occasionally causing angina or sudden death. We report an autopsy case of an aortic valve papillary fibroelastoma with coronary artery embolism. The patient was a 68-year-old Japanese man who had collapsed suddenly in his house. He was a heavy drinker and had a history of liver disease but no notable cardiac event. The autopsy revealed extensive transmural infarction of the inferior wall of the left and right cardiac ventricles. The distal portion of the right coronary artery (segment 4, NYHA) was completely occluded by tumor emboli of the fibroelastoma. At the site of closure of the aortic non-coronary cusp, there was a typical papillary fibroelastoma, which was considered to have originated the coronary embolization.  相似文献   
307.
3,4-methylenedioxyamphetamine (MDA) derivatives are increasingly abused central nervous system stimulants with neurotoxic properties. In recent years a number of controlled substance analogs (designer drugs) with high structural variety reached the illegal market making their identification an arduous task. The underivatized compounds give very similar or even virtually identical electron impact mass spectra containing mainly intense C(n)H(2n+2)N(+) immonium ions. Using tandem mass spectrometry (MS-MS) the additional structural information contained in the collision induced dissoziation (CID) mass spectra of molecular ions using electron impact (EI) and especially chemical ionization (CI) allowed an unequivocal differentiation of 18 studied regioisomeric 1-(methylenedioxyphenyl)-2-propanamines and 1-(methylenedioxyphenyl)-2-butanamines.Further synthetic methods are presented for 1-(3,4-methylenedioxyphenyl)-N-propyl-2-butanamine, N-isopropyl-1-(3,4-methylenedioxyphenyl)-2-butanamine and four 1-(2, 3-methylenedioxyphenyl)-2-butanamines. N-alkylated 1-(3, 4-methylenedioxyphenyl)-2-butanamine compounds (e.g. MBDB) are also known to be abused psychoactive agents (entactogenes) without the sympatomimetic effects of the 3,4-methylenedioxyamphetamines.  相似文献   
308.
309.
310.
Empirical definitions of identity formation, and five variants, were constructed using a technique for studying multiple self-images. The method was then applied to a sample of black and white lower socioeconomic class boys. These boys were tested with this technique and given in-depth interviews twice a year, from the start to the finish of high school. The results of these longitudinal studies disclose that the black and white adolescents have emphatically differentpatterns of identity formation. The blacks are characterized by unchanging configurations of self-images. Both the content of their self-definitions and the interrelations for these self-definitions remain strikingly stable over the years. The whites, on the other hand, display a progressive integration of different self-images and stabilization of the content of these images. The more qualitative interview data corroborate these quantitative findings. The patterns displayed by the blacks are consistent with the definition of identity foreclosure, a disruption in ego identity development. The whites' patterns, however, are consistent with progressive identity formation. In addition to discussing these results, the paper goes on to consider ways to understand the findings. Sociocultural as well as cognitive aspects of the racial differences in identity development are explored.This is a revised version of a presentation to the Fall Meeting of the American Psychoanalytical Association, December 16, 1970. The earlier version was also the recipient of the Harry C. Solomon Essay Prize at the Massachusetts Mental Health Center, June 1970.Received M.A. (Social Anthropology) from Harvard University and M.D. from Yale University. Currently studying self-image and cognitive development in populations of normal and psychiatrically impaired adolescents.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号