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   1598篇
  免费   161篇
  国内免费   53篇
耳鼻咽喉   11篇
儿科学   101篇
妇产科学   27篇
基础医学   137篇
口腔科学   56篇
临床医学   149篇
内科学   473篇
皮肤病学   35篇
神经病学   37篇
特种医学   209篇
外科学   170篇
综合类   102篇
预防医学   102篇
眼科学   12篇
药学   102篇
中国医学   3篇
肿瘤学   86篇
  2023年   21篇
  2022年   14篇
  2021年   32篇
  2020年   26篇
  2019年   19篇
  2018年   33篇
  2017年   50篇
  2016年   46篇
  2015年   34篇
  2014年   87篇
  2013年   85篇
  2012年   49篇
  2011年   48篇
  2010年   80篇
  2009年   77篇
  2008年   37篇
  2007年   79篇
  2006年   55篇
  2005年   38篇
  2004年   30篇
  2003年   15篇
  2002年   20篇
  2001年   40篇
  2000年   20篇
  1999年   20篇
  1998年   80篇
  1997年   70篇
  1996年   63篇
  1995年   53篇
  1994年   53篇
  1993年   46篇
  1992年   17篇
  1991年   14篇
  1990年   22篇
  1989年   36篇
  1988年   33篇
  1987年   26篇
  1986年   36篇
  1985年   29篇
  1984年   18篇
  1983年   20篇
  1982年   12篇
  1980年   11篇
  1979年   15篇
  1978年   13篇
  1977年   11篇
  1976年   19篇
  1975年   14篇
  1974年   9篇
  1973年   11篇
排序方式: 共有1812条查询结果,搜索用时 328 毫秒
141.
142.
In five newborn patients with spermatic cord torsion, sonography demonstrated an enlarged and globular testis, hydrocele, and skin thickening. In four of these patients the testicular parenchyma was heterogeneous. Peripheral hypoechoic areas were seen in two of the four patients; the other two had a central hypoechoic region and a peripheral echogenic rim. The testis in the fifth patient was diffusely hyperechoic. Duplex Doppler sonography performed in two patients failed to demonstrate any signal in the spermatic cord in either the abnormal or contralateral hemiscrotum. Scintigraphic findings were positive for testicular torsion in two patients and equivocal in three patients. Surgery was performed 2-12 days after sonography and established the diagnosis of spermatic cord torsion. Pathologic examination demonstrated hemorrhagic infarction of the entire testis as well as scattered calcifications. The authors conclude that a solid globular testicular mass seen during the neonatal period is suggestive of intrauterine spermatic cord torsion.  相似文献   
143.
144.
145.
146.
Continuous intraarterial blood gas (IABG) monitoring is in clinical use both in the operating room and intensive care unit. This technology uses miniature, optically-based sensors that can be placed into a patient's artery. The arterial blood gas values are transduced into an optical signal that is measured by a bedside monitor on which the values are displayed. In this paper, we describe the operating principles of the PB3300 Intra-Arterial Blood Gas Monitoring System (Puritan-Bennett Corporation, FOxS Division, Carlsbad, CA). Topics include the principles of fluorescent determinations of pH,PCo 2, andPO 2; the optical path of the PB3300; system calibration; dye layer geometry; and clinical operation. The accuracy, precision, and drift of the system measuring tonometered aqueous standards are reported. The following values were noted for eight sensors sending data to eight monitors: system bias and precisions of 0.00±0.02 pH at a pH of 7.40, –2.5±1.5 mm HgPCo 2 at aPCo 2 of 40 mm Hg, and 3.3±1.3 mm HgPO 2 at aPO 2 of 80 mm Hg.
Abstrakt Die kontinuierliche intraarterielle Blutgasüberwachung (IABG) wird klinisch sowohl im OP als auch auf der Intensivstation eingesetzt. Hierbei werden miniaturisierte, optische Sensoren angewandt, die sich direkt in der Arterie des Patienten plazieren lassen. Die Blutgaswerte werden in optische Signale umgesetzt und von einem bettseitigen Monitor gemessen und angezeigt. In dieser Arbeit beschreiben wir das Funktionsprinzip des Intra-Arteriellen Blutgasanalysesystems PB3300 (Puritan-Bennett Corporation, FOxS Division, Carlsbad, CA). Themen sind die Grundlagen der Bestimmung von pH, PCO2 und PO2 mittels Fluoreszenz; die optische Übertragung des PB3300; die Kalibrierung des Systems; die Geometrie der Farbschichten und der Einsatz in der Klinik. Die Genauigkeit, Auflösung und Drift des Systems bei der Messung von tonometrischen wässrigen Standards wird beschrieben. Die folgenden Werte ergaben sich aus einer Meßreihe mit 8 Sensoren, die an 8 Monitore angeschlossen waren (jeweils Bias, Streuung und Sollwert): 0.00±0.02 pH bei 7.40 pH, –2.5±1.5 mmHg PCO2 bei 40 mmHg PCO2 und 3.3±1.3 mmHg PO2 bei 80 mmHg PO2.

Resumen La monitorizaciòn continua de gases intraarteriales tiene uso clinico, tanto en el pabellòn de operaciones como en la unidad de cuidados intensivos. Esta tecnologia utiliza sensores miniatura de tipo òptico que pueden ser introducidos en una arteria del paciente. Los valores de gases arteriales son transducidos en forma de señal òptica que es medida al lado de la cama del paciente por un monitor que presenta los valores numéricos. En este trabajo, describimos los principios de operaciòn del PB3300 Intra-Arterial Blood Gas Monitoring System (Puritan-Bennett Corporation, FOxS Division, Carlsbad, CA). Los temas incluyen los principios de determinaciones fluorescentes de pH, PCO2, and PO2; la via òptica del PB3300; calibraciòn del sistema; geometria de la capa de colorante; y la operaciòn clinica. Se presentan la exactitud, precisiòn, y deriva (drift) del sistema, midiendo soluciones acuosas de tonometrìa estàndar. Los siguientes valores fueron registrados para ocho sensores enviando informaciòn a ocho monitores: los sesgos del sistema y las precisiones fueron de 0.00±0.02 pH a pH 7.40, –2.5±1.5 mmHg PCO2 a PCO2 40 mmHg, y 3.3±1.3 mmHg PO2 a PO2 80 mmHg.
  相似文献   
147.
A group of unique Epstein-Barr virus-containing cell lines was derived from the bone marrow of three patients with X-linked agammaglobulinemia. Efforts to obtain cell lines from the peripheral blood of these patients were uniformly unsuccessful. Immunofluorescence analyses as well as biosynthetic studies with [(35)S]methionine indicated unusual patterns of Ig synthesis in many of these bone marrow derived lines. Seven of the lines were of particular interest in that two produced no Ig of any type; two others showed no Ig by fluorescence but small amounts by [(35)S]methionine labeling; one expressed only cytoplasmic μ chains without any evidence of light chain synthesis, and two produced primarily μ chains with only slight amounts of light chains. One of the lines without membrane or cytoplasmic Ig studied in detail grew like a typical lymphoid line and was carried in intermittent culture over a period of 2 yr without Ig expression. One line grew quite differently and resembled the round cell type described previously, which has been obtained from a variety of sources. The cell line with cytoplasmic μ chains and no light-chain expression had the characteristic properties of pre-B cells. Three normal type Ig-producing cell lines also were obtained from the patients. The accumulated evidence obtained in the present study indicates that these unusual cell lines represent normal precursor cells of the B-cell lineage; these grew out in these cases because of the virtual absence of mature B cells that ordinarily overgrow the culture system. However, the possibility that in certain instances they reflect abnormal Ig synthesis characteristic of the disease has not been ruled out.  相似文献   
148.
Radiation-induced red cell damage: role of reactive oxygen species   总被引:1,自引:1,他引:1  
BACKGROUND: Cellular blood components are irradiated to prevent graft- versus-host disease in transfusion recipients at risk for this syndrome. Because gamma radiation can result in the production of reactive oxygen species, the role of reactive oxygen species was investigated in radiation-induced red cell damage. STUDY DESIGN AND METHODS: Whole blood from normal donors was exposed to various doses of t-butyl hydroperoxide (0-1 mM) and/or to gamma-radiation (0-50 Gy). Oxidative damage was assessed by the extent of lipid peroxidation (measured by thiobarbituric acid-reactive substances [TBARS]) and hemoglobin oxidation. Fresh blood was divided into three parts-one initially irradiated and stored, another stored with portions irradiated weekly, and a third stored without irradiation. TBARS and hemoglobin oxidation were measured weekly. RESULTS: As expected, t- butyl hydroperoxide induced TBARS formation and hemoglobin oxidation in a dose-dependent fashion. The gamma-radiation not only increased hemoglobin oxidation and TBARS formation, but also enhanced the t-butyl hydroperoxide effect on red cells. Red cell storage increased TBARS generation and hemoglobin oxidation in a time-dependent fashion. When radiation was administered either initially or after weekly storage, TBARS production and hemoglobin oxidation were increased over that measured in unirradiated paired controls. CONCLUSION: Gamma radiation at clinically used doses increases lipid peroxidation and hemoglobin oxidation in human red cells. The effect of gamma-radiation is accentuated by blood storage and induces damage independent of time of storage.  相似文献   
149.
150.
上海市0~6岁小儿佝偻病的现状调查   总被引:14,自引:0,他引:14  
目的:了解上海市小儿佝偻病的现状及影响因素。方法:2005年春季以整群和分层随机抽样法抽取上海市部分城区0~6岁小儿821名,采取问卷调查方法了解小儿的生活环境、饮食习惯、户外活动、营养状况、既往疾病史及母亲的妊娠情况等。佝偻病的诊断以1996年国家卫生部颁布的"婴幼儿佝偻病防治方案"为诊断标准。结果:取得完整有效资料769名,其中男童396名,女童373名;集居儿童456名,散居儿童313名。①小儿佝偻病患病率为17.3%(133/769),其中男童患病率为17.4%、女童为17.2%。②佝偻病与喂养方式(母乳喂养的患病率为13.0%、混合喂养的患病率为17.5%、人工喂养的患病率为25.2%)、鱼肝油添加(按时添加维生素D的患病率为13.5%、偶加或未加维生素D的患病率为32.5%)、居住环境(居住在市区的患病率为23.6%、居住在郊区的患病率为10.6%;集居儿童患病率为13.8%、散居儿童患病率为22.4%)、户外活动时间(经常户外活动的患病率为12.9%、偶尔户外活动的患病率为31.8%)、反复呼吸道感染(小儿有反复呼吸道感染的患病率为26.9%、无反复呼吸道感染的患病率为12.9%)、母孕期缺钙(母孕期有缺钙的患病率为33.2%、无缺钙的患病率为12.0%)等因素有关(P<0.01)。结论:上海市小儿佝偻病患病率有上升趋势。影响因素与城市环境污染、母乳喂养减少、年轻父母科学育儿知识缺乏等有关。  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