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   1329篇
  免费   124篇
  国内免费   4篇
耳鼻咽喉   6篇
儿科学   69篇
妇产科学   21篇
基础医学   217篇
口腔科学   29篇
临床医学   90篇
内科学   345篇
皮肤病学   78篇
神经病学   74篇
特种医学   45篇
外科学   144篇
综合类   24篇
预防医学   94篇
眼科学   14篇
药学   115篇
中国医学   14篇
肿瘤学   78篇
  2022年   14篇
  2021年   27篇
  2020年   23篇
  2019年   29篇
  2018年   43篇
  2017年   25篇
  2016年   26篇
  2015年   28篇
  2014年   41篇
  2013年   71篇
  2012年   72篇
  2011年   80篇
  2010年   43篇
  2009年   43篇
  2008年   75篇
  2007年   77篇
  2006年   62篇
  2005年   49篇
  2004年   41篇
  2003年   40篇
  2002年   24篇
  2001年   31篇
  2000年   26篇
  1999年   28篇
  1998年   21篇
  1997年   15篇
  1996年   18篇
  1995年   17篇
  1993年   11篇
  1992年   30篇
  1991年   32篇
  1990年   22篇
  1989年   21篇
  1988年   18篇
  1987年   11篇
  1986年   11篇
  1985年   18篇
  1984年   15篇
  1983年   10篇
  1982年   9篇
  1981年   16篇
  1979年   10篇
  1978年   12篇
  1977年   17篇
  1976年   15篇
  1975年   8篇
  1974年   12篇
  1973年   9篇
  1969年   8篇
  1967年   7篇
排序方式: 共有1457条查询结果,搜索用时 0 毫秒
71.
72.
The present study has been carried out in the slum areas of Gorakhpur city, covering a population of 10,187 in the four colleges of Gorakhpur. Five hundred and eighty children and adolescents in urban slums, and 750 college students between 10–18 years were studied by means of a questionnaire card for detection of prevalence rate and various others co-relates of abuse of psychoactive substances. Overall, prevalence of abuse of psychoactive substances was 25% in slum areas, and 18% in college students. Abuse of tobacco was most frequent (50.3% & 72.5%) followed by that of alcohol (11.7% & 16.2%) in both the groups respectively. Cannabis was also used by some children (0.6%). More abusers were from Hindu families with low educational status and low family income. Surprisingly no one was found to be abusing tablets and street drugs.  相似文献   
73.
The clinical and light and electron microscopic features of five cases of primary vaginal leiomyosarcoma, representing 2.9% of all vaginal malignancies registered at the Swedish Cancer Registry, are presented. The ages of the patients ranged from 31 to 69 years. The most common clinical presentation was an increasing mass and/or local tenderness. The tumor was located in the anterior wall in three cases and in the lateral wall in two. The size of the tumors ranged from 2 to over 10 cm. Four patients had tumors of high histologic malignancy grade and were all dead within 36 months. One patient had a tumor of low grade and is still alive 10 years after the initial excision. The ultrastructural observations of abundant myofilaments with focal elongated densities in primary paraffin-embedded material conform with the light microscopic diagnoses in all cases and indicate the usefulness and value of such material for electron microscopy in order to arrive at the diagnosis of leiomyosarcoma. The therapeutic and diagnostic aspects are discussed.  相似文献   
74.
DNA minor groove binder hybrid molecules, netropsin derivatives such as N-[2-(dimethylamino)ethyl]-1-methyl-4-aminopyrrolo-2-carboxamide (MePy) or its derivatives containing two units of N-methylpyrrolecarboxamide (diMePy) and bisbenzimidazole (Ho33258), were linked to the NH(2) function of AHMA or to the CH(2)OH group of AHMA-ethylcarbamate to form AHMA-N-netropsins (13-16) and AHMA-ethylcarbamate-O-netropsins (19-22), and AHMA-bisbenzimidazole (AHMA-Ho33258, 25), respectively. These conjugates' in vitro antitumor activity, inhibition of a variety of human tumor cell growth, revealed that AHMA-ethylcarbamate-O-netropsin derivatives were more cytotoxic than AHMA-N-netropsin compounds. In the same studies, all compounds bearing MePy were more potent than those compounds linked with diMePy. Moreover, AHMA-netropsin derivatives bearing a succinyl chain as the linking spacer were more potent than those compounds having a glutaryl bridge. Among these hybrid molecules, AHMA-ethylcarbamate-O-succinyl-MePy (19) was 2- to 6-fold more cytotoxic than the parent compound AHMA (5) in various cell lines, whereas compound 25 had very poor solubility and was inactive. Studies on the inhibitory effect against topoisomerase II (Topo II) and DNA interaction of these conjugates showed no correlation between the potency of DNA binding and inhibitory activity against Topo II.  相似文献   
75.
Potent enzyme inhibitors have long been recognized as powerful tools for assessing the physiological roles of enzymes and have led to the therapeutic drugs able to modulate their activities in vivo. However, to be valuable tools such inhibitors should be selective so that they do not interfere with other members of the particular enzyme family. Combinatorial chemistry has proven to be a novel approach for the identification of molecules with a desired selectivity profile from the libraries of several million compounds. In recent years it has been extensively used in conjunction with computational methods for the development of potent inhibitors of therapeutically interesting targets. This review describes the various structurally diverse enzyme inhibitors identified by screening combinatorial libraries of peptides and small organic molecules.  相似文献   
76.
Neuroanatomical distribution of FMRFamide-like immunoreactivity was investigated in the brain and olfactory system of the viviparous skink, Chalcides chalcides. In the adult brain FMRFamide immunoreactive (ir) perikarya were observed in the diagonal band of Broca, medial septal nucleus, accumbens nucleus, bed nucleus of the anterior commissure, periventricular hypothalamic nucleus, lateral forebrain bundle, and lateral preoptic, subcommissural, suprachiasmatic and lateral hypothalamic areas. This pattern was seen in both male and female brains. Though all major brain areas showed FMRFamide-ir innervation, the densest ir fiber network was observed in the hypothalamus. During development, ir elements were observed for the first time in embryos at mid-pregnancy. FMRFamide perikarya were located along the ventral surface of the vomeronasal nerve, in the olfactory peduncle mediobasally, as well as in the anterior olfactory nucleus and olfactory tubercle. Furthermore, some ir neurons were observed in the rhombencephalic reticular substance; however, the ir fiber network was poorly developed. Later in development FMRFamide-ir neurons appeared also in the bed nucleus of the anterior commissure as well as the rhombencephalic nucleus of solitary tract and the dorsal motor nucleus of vagus nerve. In juveniles, the distribution profile of FMRFamide immunoreactivity was substantially similar to that of the adults, with a less widespread neuronal distribution and a more developed fiber network. Ontogenetic presence of FMRFamide immunoreactivity in the nasal area has been linked to the presence of a nervus terminalis in this reptile.  相似文献   
77.
Summary The clinical spectrum of infective endocarditis (IE) in infants is examined in four infants between 3 and 9 months of age. None of the patients had signs of IE; all four had an anatomically normal heart. Echocardiograms showed echodense vegetations in the left side of heart in three cases and in the right side in one. Three of the four patients recovered after the episode of endocarditis. Three of the four patients had necrotizing enterocolitis in the neonatal period. The important predisposing factor was the presence of indwelling central catheter for intravenous nutrition. Unlike previously reported cases, coagulase-negativeStaphylococci andEnterococci were important causative organisms in this high-risk nursery population.Presented in part at the APS/SPR Meeting in Anaheim, California, May 8, 1990.  相似文献   
78.
79.
Hypertension is a complex, heterogeneous disorder of which the exact etiology is unknown. The difficulty in ascribing an independent role to a single dietary constituent in blood pressure regulation may be due to interactions among nutrients which influence blood pressure. The effect of any one nutrient, particularly magnesium, on hypertension should be considered within the context of overall nutrition in each patient. Clinical, experimental and epidemiologic studies support the role of magnesium in hypertension, whereas a few studies negate this role. Magnesium ions are important in arterial smooth muscle contraction. Since magnesium is found mainly at the inner surface of the cell membranes, it could play a role in cell membrane permeability for sodium and calcium which is important in the etiopathogenesis of hypertension. Magnesium deficiency can predispose to increased contractility of the arteries and its excess can modulate smooth muscle contractility caused by bradykinin, angiotensin II, serotonin, prostaglandins and catecholamines. Magnesium therapy can prevent the development of resistant hypertension and arrhythmias in hypertensives with diuretic-induced hypomagnesemia. It might also reduce blood pressure at least up to 10/5 mm Hg provided adequate magnesium salts are given for an adequate period of time. In view of the still ill defined role of magnesium in hypertension, magnesium supplementation is advised only to those hypertensives who are receiving diuretics and develop resistant hypertension or who have frank magnesium deficiency. A diet rich in magnesium may be used for prevention of hypertension in predisposed communities because of the other advantages of such a diet in prevention.  相似文献   
80.
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