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   46347篇
  免费   3217篇
  国内免费   860篇
耳鼻咽喉   259篇
儿科学   1981篇
妇产科学   1260篇
基础医学   6196篇
口腔科学   1254篇
临床医学   3190篇
内科学   9299篇
皮肤病学   719篇
神经病学   3502篇
特种医学   2023篇
外国民族医学   5篇
外科学   6172篇
综合类   3215篇
现状与发展   3篇
预防医学   3453篇
眼科学   462篇
药学   4337篇
  27篇
中国医学   894篇
肿瘤学   2173篇
  2023年   589篇
  2022年   1291篇
  2021年   1933篇
  2020年   1576篇
  2019年   2570篇
  2018年   2533篇
  2017年   1695篇
  2016年   1296篇
  2015年   1325篇
  2014年   2296篇
  2013年   2321篇
  2012年   1657篇
  2011年   1786篇
  2010年   1469篇
  2009年   1608篇
  2008年   1429篇
  2007年   1359篇
  2006年   1262篇
  2005年   1045篇
  2004年   934篇
  2003年   896篇
  2002年   678篇
  2001年   644篇
  2000年   576篇
  1999年   539篇
  1998年   442篇
  1997年   385篇
  1996年   323篇
  1995年   275篇
  1994年   235篇
  1993年   179篇
  1992年   160篇
  1991年   166篇
  1990年   137篇
  1989年   126篇
  1988年   126篇
  1987年   92篇
  1985年   1034篇
  1984年   1827篇
  1983年   1117篇
  1982年   1248篇
  1981年   1207篇
  1980年   994篇
  1979年   900篇
  1978年   805篇
  1977年   689篇
  1976年   792篇
  1975年   560篇
  1974年   496篇
  1973年   562篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Bone disorders following gastrectomy were studied by measuring absolute and relative bone mineral density of the Wards triangle, serum 1,25-(OH)2-D, alkaline phosphatase, and total serum calcium. The subjects were 20 males who had undergone total gastrectomy not more than three months previously (group A1). Seventeen of these patients were reviewed three years later (group A2). Absolute and relative bone density were significantly lower in group A2 than in A1 (0.52 ± 0.011 g/cm2 versus 0.6 ± 0.014 g/cm2,P<0.01 and 85.5 ± 1.4% age-matched control versus 95 ± 1.3%,P<0.01). 1,25-(OH)2-D was significantly lower in group A2 than in group A1 (14.3 ± 0.97 pg/ml versus 20.6 ± 1.02 pg/ml,P<0.01). There was no difference in alkaline phosphatase and calcium serum concentration. The mean weight loss was 6.26 ± 0.57% over the follow-up period, and weight loss correlated with absolute and relative bone density (r=–0.74,P<0.01). There was a positive correlation between 1,25-(OH)2-D and absolute or relative bone density (r=0.67,r=0.62 andP<0.01). These data suggest that bone density decrease has already occurred three years after total gastrectomy and is positively correlated to 1,25-(OH)2-D deficiency. As no differences in serum alkaline phosphatase and serum calcium concentration were found, these factors are of little value for the early detection of postgastrectomy bone disorders, whereas weight loss is a valuable screening parameter.  相似文献   
132.
新生大鼠反复惊厥对NMDA受体表达的长期影响   总被引:6,自引:0,他引:6  
目的:研究反复惊厥对大鼠脑内N-甲基-D-天门冬氨酸(NMDA)受体表达,以及成年期认知功能和惊厥阈的长期影响。方法:生后6d(用P6表示,下同)的Wistar大鼠随机分成两组,每组6只,惊厥组每日吸入三氟乙醚诱导惊厥发作1次,每次持续30min,连续6d;对照组同样操作但不吸入三氟乙醚。两组大鼠于P60-P65行Morris水迷宫实验,检测大鼠的学习记忆功能。于P75时给予大鼠腹腔注射戊四唑(PTZ)测定大鼠的惊厥阈。随即断头处死大鼠,分离大脑皮质和海马,匀浆提取细胞膜蛋白,应用免疫印记法测定NMDA受体亚基l(NRl)和NR2A-2D表达的变化。结果:从P6l至P65,两组大鼠寻找平台时间均逐渐缩短,惊厥组大鼠在P65的平均寻找平台时间较对照组显著延长。惊厥组大鼠注射PTZ后发生惊厥的潜伏期与对照组比较差异无显著性。在大脑皮层,惊厥组大鼠较对照组NRl和NR2B表达水平明显下调,在海马这两种亚基表达水平无明显改变,在大脑皮层和海马区,惊厥组较对照组NR2A表达水平明显下调,NR2C表达水平明显上调。两组在皮层和海马均无NR2D表达。结论;新生大鼠反复惊厥可导致远期认知障碍,同时伴有NMDA受体的数量和结构上的长期改变,NMDA受体表达的这种改变可能在发育期惊厥导致的脑长期认知功能损害中起重要作用。  相似文献   
133.
Macran  S.  Kind  P.  Collingwood  J.  Hull  R.  McDonald  I.  Parkinson  L. 《Quality of life research》2003,12(2):177-188
This study reports on the preliminary testing of a new measure designed for use alongside EQ-5D in evaluating outcomes in podiatry: the Podiatry Health Questionnaire (PHQ). Individuals aged 18 years or more, receiving podiatry services in clinic or domicilliary locations across four NHS Trusts in Yorkshire and Humberside UK took part in a questionnaire survey. Respondents reported high levels of problems on all six PHQ dimensions. Correlations suggested that the PHQ and EQ-5D were measuring distinct constructs. The levels on each dimension were well defined in terms of self-rated morbidity on the PHQ visual analogue scale (PHQvas) and the EQ-5Dvas, although PHQvas appeared to be slightly more sensitive to changes in health on the dimensions. There was a strong relationship between clinicians' Podiatry Clinical Score rating and reported symptoms for four out of six PHQ dimensions and PHQvas. The PHQ was able to distinguish respondents in terms of their self-reported morbidity in EQ-5D and in terms of their morbidity as assessed by clinicians. It is suggested that the respondent completed PHQ appears to be a useful new measure for assessing foot-related health. However, further investigation of the psychometric properties of the measure is required.  相似文献   
134.
用RP-HPLC法(固定相为μBondpak C18柱,流动相为己烷磺酸钠冰醋酸液,紫外检测波长为280nm)同时测定出复合维生素B片中四个组分的含量,方法专属性强,省时;维生素B1、B2、B6和烟酰胺的平均回收率和平均相对标准偏差分别为100.5%,2.0%;98.0%,1.9%;101.8%,1.1%;100.1%,2.1%(n=3)。  相似文献   
135.
目的 了解轻度认知功能损害 (MCI)患者血清维生素E(VitE)、超氧化物歧化酶 (SOD)和丙二醛(MDA)的水平 ,探讨其变化的临床意义。方法 采用 1∶1配对病例对照设计 ,受试者均于晨 7时空腹抽静脉血 ,应用紫外分光光度法测定了 4 5例老年MCI患者和 4 5例健康老年人血清VitE ,SOD和MDA的含量。结果 老年MCI患者血清VitE含量及SOD活性显著低于健康老年人 (P <0 .0 1) ,血清MDA含量显著高于健康老年人 (P <0 .0 1)。结论 以MDA为代表的自由基代谢产物参与了MCI的病理生理过程 ;临床上应给予外源性VitE以进行早期干预治疗。  相似文献   
136.
137.
乳腺癌组织中Cyclin D1及p16蛋白表达的联合检测及其意义   总被引:3,自引:1,他引:2  
目的:探讨乳腺癌中Cyclin D1及p16蛋白表达的相关性及其临床意义。方法:LSAB法检测多种乳腺组织中Cyclin D1及p16蛋白的表达情况,结合有关临床资料,分析Cyclin D1和p16蛋白表达异常与乳腺癌中重要的临床病理因素的关系。结果:62例乳腺癌组织中,Cyclin D1蛋白过度表达占48·4%,其表达与乳腺癌组织学分级呈明显正相关,且Cyclin D1蛋白过度表达更常见于ER、PR阳性的乳腺癌中。乳腺癌旁组织中Cyclin D1蛋白过度表达为20·0%,其他几种乳腺组织很少有CyclinD1蛋白的过度表达。p16蛋白仅在58·1%的乳腺癌组织中有表达,且p16的表达与组织学分级程度有负相关关系。正常乳腺组织中未见p16蛋白的异常。结论:乳腺癌组织中存在着Cyclin D1蛋白的过度表达及p16蛋白的异常,二者对乳腺癌组织的增殖分化有一定的影响。  相似文献   
138.
BACKGROUND: The purpose of this study was to determine bone mineral density (BMD) of lumbar spine in malnourished children without rachitic manifestations, before and after dietary treatment and vitamin D supplementation, and to compare with healthy children of the same community. METHODS: The subjects were 41 children with malnutrition and 21 healthy controls. None of the children had clinical, biochemical and/or radiological rickets features. The patients had moderate 15 and severe 26 malnutrition according to Gomez's criteria. Using the Wellcome Classification, marasmus was diagnosed in 16 children, kwashiorkor in 10 children. The children with malnutrition were given vitamin D supplementation. RESULTS: BMD was lower in children with malnutrition than in controls (P < 0.01). Mineralization significantly effected the severity of malnutrition (P < 0.01). BMD in kwashiorkor was similar to that of marasmus. The mean BMD level of infants receiving 400 IU of vitamin D daily was similar to that of infants receiving 800 IU of vitamin D daily at the beginning of treatment. In two supplementation groups, the BMD gradually increased during the first 3 months of treatment, but this increase in the infants receiving 800 IU of vitamin D daily was significantly higher than that in the infants receiving 400 IU of vitamin D daily. CONCLUSION: Measurements of BMD in children with malnutrition, especially severe malnutrition, are to be recommended in the initial assessment of the severity of osteopenia and in the follow up to monitor the response to therapy. Children with malnutrition should be given 800 IU of vitamin D daily. The loss of BMD must be accepted as a complication of malnutrition.  相似文献   
139.
选用产期接近的3月龄小尾寒羊30只,随机分为二组(试验Ⅰ、试验Ⅱ),每组15只。试验Ⅰ饲喂本场加工的羔羊精饲料,试验Ⅱ饲喂本场加工的羔羊精饲料基础上,每公斤饲料中分别添加钴0.4mg和维生素B120.30mg,试验结果表明:试验Ⅰ与试验Ⅱ日增重相比差异极显著(P<0.01)。  相似文献   
140.
Summary Serum intact parathyroid hormone (PTH), 25 hydroxyvitamin D(25OHD), 1,25 dihydroxyvitamin D (1,25(OH)2D), albumin, and ionized calcium were measured in 61 Chinese female patients with hip fracture and 61 control subjects. Hip fracture patients had low albumin, ionized calcium, and 250HD levels. Serum PTH and 1,25 (OH)2D values were not different between the two groups. We conclude that although 250HD level in hip fracture patients is low, there is no evidence of secondary hyperparathyroidism, suggesting that the low 250HD levels may be a secondary phenomenon in response to the fracture.  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