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   22855篇
  免费   2410篇
  国内免费   735篇
耳鼻咽喉   177篇
儿科学   256篇
妇产科学   208篇
基础医学   977篇
口腔科学   640篇
临床医学   3806篇
内科学   1724篇
皮肤病学   172篇
神经病学   796篇
特种医学   580篇
外国民族医学   7篇
外科学   1400篇
综合类   3425篇
现状与发展   1篇
一般理论   1篇
预防医学   5576篇
眼科学   121篇
药学   3350篇
  77篇
中国医学   2116篇
肿瘤学   590篇
  2024年   105篇
  2023年   557篇
  2022年   820篇
  2021年   1130篇
  2020年   1195篇
  2019年   929篇
  2018年   893篇
  2017年   938篇
  2016年   1012篇
  2015年   976篇
  2014年   1806篇
  2013年   1973篇
  2012年   1613篇
  2011年   1649篇
  2010年   1264篇
  2009年   1174篇
  2008年   1094篇
  2007年   1046篇
  2006年   921篇
  2005年   730篇
  2004年   624篇
  2003年   527篇
  2002年   403篇
  2001年   367篇
  2000年   304篇
  1999年   298篇
  1998年   240篇
  1997年   187篇
  1996年   171篇
  1995年   134篇
  1994年   136篇
  1993年   98篇
  1992年   102篇
  1991年   84篇
  1990年   69篇
  1989年   58篇
  1988年   57篇
  1987年   37篇
  1986年   49篇
  1985年   51篇
  1984年   42篇
  1983年   19篇
  1982年   19篇
  1981年   19篇
  1980年   28篇
  1979年   9篇
  1978年   16篇
  1977年   11篇
  1975年   7篇
  1974年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
We assessed the feasibility and psychometric properties of two commonly used health status questionnaires in Parkinson's disease (PD): the generic Nottingham Health Profile (NHP) and the disease-specific 39-item Parkinson's disease Questionnaire (PDQ-39), from a cross-sectional postal survey of PD patients (N = 81), using traditional and Rasch measurement methodologies. Overall response rate was 88%. Both questionnaires were found feasible, although the NHP performed less well. The PDQ-39 had fewer floor effects and was better able to separate respondents into distinct groups than the NHP, whereas the latter exhibited less ambiguous dimensionality and better targeting of respondents with non-extreme scores. Reliability and validity indices were similar, and potential differential item functioning by age and gender groups was found for both questionnaires. PDQ-39 response alternatives indicated ambiguity. With few exceptions, questionnaire scales were unable to meet recommended standards fully. While preliminary, this study illustrates the need for thorough evaluation of outcome measures and has implications beyond the questionnaires used here. Although promising, both questionnaires warrant further developmental work and stronger support of measurement validity before they could be considered fully suitable for valid use in PD, in particular in earlier stages of the disease.  相似文献   
102.
<正> 花粉在古代就曾作为强身保健食品。美、英两国的科学家曾分析了花粉的成分,发现花粉由96种元素组成,其中有维生素、矿物质、酶、蛋白质和某些其它物质。美国明尼苏达大学曾做过花粉对动物的增重实验。当41~150日龄小猪饲料中添加2~3%的玉米花粉时,体重增长明显快于对照组,  相似文献   
103.
Most clinical procedures using the laser are based on thermal laser-tissue interactions. The treatment often consists of inducing damage of given degree and extent by heating the tissue. The aim of this study was to develop a model called HELIOS. The ability of HELIOS to predict thermal coagulation was evaluated by comparison with in vivo experimental results. Conversion of laser light in tissue was studied using the beam-broadening model. Temperature was described by the heat conduction equation solved using the finite difference method. The tissue dena-turation was modeled by the Henriques equation leading to the determination of the damage coefficient ω. For a given set of laser and tissue parameters, HELIOS makes a graphic representation of coagulation necrosis and temperature evolution in tissue. HELIOS was validated by experimental studies in vivo on rat liver using a CW Nd:YAG laser, a CO2 laser, and an argon laser. For given sets of laser parameters, temperature measurements were performed using an infrared camera. Histological examinations were carried out on samples to quantify the depth of coagulation necrosis. Experimental data obtained in vivo were compared with those calculated using HELIOS and similar sets of parameters. The difference between the predicted temperature evolution on tissue surface and that measured by the infrared camera was < 5°C in all cases. The difference between the predicted coagulation necrosis depth and the corresponding experimental one was < 10%. In conclusion, HELIOS allows good prediction of tissue temperature and coagulation necrosis. © 1994 Wiley-Liss, inc.  相似文献   
104.
高等教育大众化对质量的关注是必然的.高等教育评估制度的建设是当前我国深化高等教育管理体制改革、保证高等教育健康发展的需要.我们要建立既符合中国国情又体现高等教育评估普遍规律的具中国特色的高等教育评估制度.  相似文献   
105.
去骨瓣减压术治疗大面积脑梗死的短期疗效评价   总被引:7,自引:1,他引:6  
目的:评价去骨瓣减压术治疗大面积脑梗死的效果。方法:制定入选和排除标准,统一术式,比较术前、术后不同时期的神经功能变化,并对存活病例进行随访(6个月),评价术后3和6个月时的预后评分(GOS)和BarthelIndex(BI)的变化。结果:按入选标准行去骨瓣减压术26例,术后死亡率为30.8%。术前昏迷评分GCS对决定手术时机有指导作用。共随访14例患者,术后3和6个月GOS分别为3.6±0.8和4.0±0.8,与出院时GOS评分比差异有统计学意义。术后3和6个月BI分别为68.9±29.4和77.5±28.3,其中术后6个月BI>60者占85.7%。结论:对保守治疗无效的大面积脑梗死患者,去骨瓣减压术不仅可作为一种“救命”手术,而且多数存活病例恢复较好。合理选择手术适应证、及时把握手术时机以及充分手术减压可能是影响预后的重要因素。  相似文献   
106.
主成份分析与因子分析用于多指标综合评价   总被引:9,自引:0,他引:9  
本文从应用角度阐明了主成份分析与因子分析用于多指标综合评价的异同点,并用实例加以说明。提出了主成份分析和因子分析用于多指标综合评价时,应在能明确主成份或因子的意义和方向情况下加权,否则会得到错误的结果。  相似文献   
107.
Summary: Some of the properties of 4–bromobenzalde-hyde semicarbazone (compound IV), a prototype molecule of a new class of anticonvulsants, aryl semicarbazones, are described. Compound IV demonstrated activity in the maximal electroshock (MES) and subcutaneous pentylenetetrazol (scPTZ) tests in mice, with low neurotoxicity. When given orally to rats, it displayed high potency in the MES test and very low neurotoxicity, resulting in a high protective index (PI). Compound IV displayed no proconvulsant properties, and development of rapid tolerance was not noted. When administered intraperitoneally (i.p.) at doses of 100, 300, or 600 mg/kg to rats, compound IV had no effect on levels of γ-aminobu-tyric acid (GABA) or on GABA-T activity in whole brain. When tested in vitro, compound IV had no effect on rat brain GABA-T at a drug concentration of 100 μM. Although the activities of certain drug-metabolizing enzymes were increased after oral administration of compound IV to rats, these effects were less prominent than those of phenytoin (PHT) and carbamazepine (CBZ). The principal mode of action of compound IV does not appear to be an interaction with the GABAA receptor complex, and other mechanisms, involving excitatory amino acid neurotransmission, will have to be considered in future investigations of the anticonvulsant activity of this compound.  相似文献   
108.
The present trial was designed to evaluate clinical scores (single observer) of sodium lauryl sulphate (SLS)-induced skin irritation in a group of subjects (n = 10) over a 10-day period along with various skin function parameters. In order to avoid significant variations due to secondary phenomena, the following parameters were recorded with non-invasive instruments in this order: skin capacitance (C1; arbitrary units; CM420 Corneometer), transepidermal water loss (TEWL; g/m2.h; Evaporimeter) and laser Doppler flowmetry (CBFV: cutaneous blood flow values; Periflux). All examinations were performed during winter on reclined relaxed subjects present for at least 10 min in a test room with controlled temperature and relative humidity (t degrees: 19.5-20.7 degrees C and RH: 47.3-60.3%). The analysis of differential data (delta = value at tx-value before test; 2-way ANOVA) was made on single parameters as a function of site (volar forearm versus neck) and time (from 24 h after 48-h occlusion with 5% SLS up to 10 days later). The profile of erythema scores over time differed between neck and forearm, but the delta CBFV readings with the laser Doppler instrument did not detect significant site-time interactions. Roughness (blind evaluation with palpating finger) and capacitance readings (delta C1) showed significant differences between sites, but the profile over time was similar in both locations. delta TEWL did not differ according to anatomical location. The reason for different erythema scores on neck and forearm might be related to inherent regional variation of optical properties of the skin or to a substantial contribution of SLS-induced roughness to the readings of erythema.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
109.
抗衰老药物家蚕寿命测定法的研究   总被引:3,自引:0,他引:3  
陈传盈  胡斌 《中成药》1994,16(2):32-34
本实验表明,多种中药材,如香附子、花粉、党参、菟丝子、蛇床子等的提取液涂在桑叶上喂蚕,能显著延长蚕蛾寿命,但对家蚕幼虫龄期无明显影响。这种实验方法重演性好,如能进一步完善试验方法,将可用于筛选抗衰老药物的研究。  相似文献   
110.
三种虾蛄肌肉营养成分分析及评价   总被引:6,自引:1,他引:5  
蒋霞敏  钱云霞  王春琳 《营养学报》2003,25(2):175-177,180
虾蛄俗称“虾爬子”,“螳螂虾”,“琵琶虾”、“小龙虾”等 ,隶属节肢动物门 ,甲壳纲 ,口足目 ,虾蛄科的经济海产动物 ,主要生活在近海浅滩泥质海底巢穴中 ,全国各地的沿海都有分布。近年来随着人们膳食结构的转变 ,虾蛄是深受人们喜爱的佳肴 ,也是出口创汇的水产品之一。对虾蛄 ,国内外均有研究 [1~ 6 ]。但对营养成分分析报道较少[7,8] 。本研究分别对三种虾蛄的基本营养成分、氨基酸、脂肪酸的组成和含量进行比较研究 ,为虾蛄的人工养殖和综合利用提供基础数据。1 材 料 与 方 法1 .1 材料  实验所用口虾蛄 ( Oratosquilla ora…  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