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   42717篇
  免费   2909篇
  国内免费   755篇
耳鼻咽喉   238篇
儿科学   1762篇
妇产科学   1162篇
基础医学   5924篇
口腔科学   1227篇
临床医学   2943篇
内科学   8830篇
皮肤病学   692篇
神经病学   3257篇
特种医学   1977篇
外国民族医学   4篇
外科学   5871篇
综合类   2667篇
现状与发展   3篇
预防医学   2949篇
眼科学   423篇
药学   3519篇
  27篇
中国医学   812篇
肿瘤学   2094篇
  2024年   85篇
  2023年   604篇
  2022年   1403篇
  2021年   1855篇
  2020年   1494篇
  2019年   2518篇
  2018年   2443篇
  2017年   1613篇
  2016年   1198篇
  2015年   1231篇
  2014年   2079篇
  2013年   2077篇
  2012年   1439篇
  2011年   1569篇
  2010年   1264篇
  2009年   1382篇
  2008年   1235篇
  2007年   1121篇
  2006年   1055篇
  2005年   859篇
  2004年   776篇
  2003年   782篇
  2002年   567篇
  2001年   525篇
  2000年   500篇
  1999年   463篇
  1998年   354篇
  1997年   321篇
  1996年   278篇
  1995年   204篇
  1994年   184篇
  1993年   132篇
  1992年   111篇
  1991年   120篇
  1990年   98篇
  1989年   99篇
  1988年   92篇
  1985年   1006篇
  1984年   1790篇
  1983年   1099篇
  1982年   1226篇
  1981年   1191篇
  1980年   984篇
  1979年   880篇
  1978年   800篇
  1977年   684篇
  1976年   789篇
  1975年   558篇
  1974年   496篇
  1973年   552篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
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   
52.
53.
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   
54.
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   
55.
Summary We have studied the hypoalgesic effect of codeine (100 mg) after blocking the hepatic O-demethylation of codeine to morphine via the sparteine oxygenase (CYP2D6) by quinidine (200 mg). The study was performed in 16 extensive metabolizers of sparteine, using a double-blind, randomized, four-way, cross-over design. The treatments given at 3 h intervals during the four sessions were placebo/placebo, quinidine/placebo, placebo/codeine, and quinidine/codeine. We measured pin-prick pain and pain tolerance thresholds to high energy argon laser stimuli before and 1, 2, and 3 h after codeine or placebo.After codeine and placebo, the peak plasma concentration of morphine was 6–62 (median 18) nmol·.l–1. When quinidine pre-treatment was given, no morphine could be detected (<4 nmol·l–1) after codeine. The pin-prick pain thresholds were significantly increased after placebo/codeine, but not after quinidine/codeine compared with placebo/placebo. Both placebo/codeine and quinidine/codeine increased pain tolerance thresholds significantly. Quinidine/codeine and quinidine/placebo did not differ significantly for either pin-prick or tolerance pain thresholds.These results are compatible with local CYP2D6 mediated formation of morphine in the brain, not being blocked by quinidine. Alternatively, a hypoalgesic effect of quinidine might have confounded the results.  相似文献   
56.
A Batak Indonesian from North Sumatra with hemoglobin (Hb) D Punjab (alpha 2 beta 2 121----Gln) and hemoglobin Constant Spring (Hb CoSp) is described. The 24-year-old man did not have clinical symptoms, and his hematological indices were normal. However, he had a persistent slight elevation of fetal hemoglobin level. His mother and his brother were heterozygous for Hb D Punjab; his father had Hb CoSp trait. A sister did not have any abnormal hemoglobin. To show the exact molecular defect leading to the synthesis of Hb CoSp in this family, genomic DNA from the father was analyzed by hybridization with synthetic oligonucleotides. Genomic DNA was digested with Sst I and Hind III producing a 1.05-kb fragment from the 3' end segment of the alpha 2-globin gene, including the termination codon. Two nonadecamers were synthesized to serve as probes: one, entirely homologous to the normal 3' end of alpha 2A-globin gene sequence, including the termination codon TAA, the other different from it by a replacement of the T in the termination codon TAA with C, changing it to CAA, the codon for the amino acid glutamine. DNA from normal controls gave a positive signal with the normal alpha 2TAA oligonucleotide probe but negative with the alpha 2 CAA probe. The father of propositus who had Hb CoSp trait gave a positive signal with the normal alpha 2TAA oligonucleotide probe as well as with the alpha 2CAA oligonucleotide probe, showing him to be heterozygous for the alpha 2CAA-globin gene. This result shows that the Hb CoSp in the Batak family is indeed due to a replacement of T by C in the TAA termination codon of the alpha 2-globin gene changing it to CAA the condon for glutamine. This explains the resulting readthrough of the untranslated sequence of the mRNA.  相似文献   
57.
Many researchers have evaluated the motions of the shoulder girdle, especially scapular and humeral motion. However, few reports exist that describe motions of the acromioclavicular joint. The purpose of the present study was to analyze the 3D kinematics of the acromioclavicular joint during arm abduction using 3D MR images obtained by a vertically open MRI. Fourteen shoulders of seven volunteers were examined in seven static positions from 0 degrees to the maximum abduction in a seated position. 3D surface models of the clavicle and scapula were created, and the movements of the acromioclavicular joint from 0 degrees to each position were calculated using the volume-based registration technique. From these calculations, the translations were evaluated and the rotational motions were analyzed using the concept of the screw axis. In the anteroposterior direction, the clavicle translated most posteriorly (-1.9 +/- 1.3 mm) at 90 degrees of abduction and most anteriorly (1.6 +/- 2.7 mm) at maximum abduction. In the superoinferior direction, the clavicle translated slightly superiorly (0.9 +/- 1.9 mm). When analyzing relative motion of the scapula with respect to the clavicle, the scapula generally rotated about a specific screw axis passing through the insertions of both the acromioclavicular and the coracoclavicular ligaments on the coracoid process. The average rotation was 34.9 +/- 8.4 degrees.  相似文献   
58.
Several topical treatments are available for patients with psoriasis. Although individualization of the treatment remains important, there is a need for treatment recommendations to identify the best treatment out of the available treatments and to help with improvement in treatment compliance. In this communication we give our views on the assessment of severity of psoriasis. We provide recommendations for selection of treatments, reconciling the clearance phase and the long‐term management. Finally, we provide recommendations for the treatment of particular localizations: the scalp and psoriasis at sensitive sites.  相似文献   
59.
目的:探讨用长链核酸扩增技术评价病毒灭活效果的可行性.方法:针对伪狂犬病毒(pseudorabies virus,PRV)糖蛋白gD基因前后的保守区设计预计产物长短不一的5对引物,用半巢式PCR技术扩增经低pH法(4.0±0.1)、巴氏消毒法[(60±1.0)℃]和s/D法(有机溶剂/洗涤荆)处理后的PRV核酸,同时以细胞感染法做平行对照.结果:低pH对PRV核酸有破坏作用,处理时间越长,核酸损伤程度越明显,处理60 min时,6.62 lgTCID50的PRV完全被灭活.5条不同长度PCR扩增产物中,只有3.9 kb的长片段检出与细胞培养结果一致.7.25 lgTCID50的PRV经(60±1.0)℃处理20 min后即被完全灭活,7.13 lgTCID50的PRV经s/D法处理1 h后被完全灭活,但各长度核酸片段扩增均为阳性,与细胞感染试验结果不符.结论:低pH对PRV核酸的损伤程度随处理时间的延长而增加;用长链PCR(3.9 kb)技术来评价经低pH法灭活病毒的效果是可行的,而该法不适合评价巴氏消毒法和S/D法灭活病毒的效果.  相似文献   
60.
健身宝对衰老模型小鼠血清SOD和MDA的影响   总被引:2,自引:0,他引:2  
目的 研究健身宝补脾益肾、延缓衰老的作用机制。方法 将 60只小鼠随机分为 6组 ,除正常对照组外均每日注射对D -半乳糖造成衰老模型 ,同时给予不同剂量的健身宝和金匮肾气丸。 6周后检测小鼠血清中SOD活性、MDA含量。结果 衰老模型组与正常对照组比较 ,小鼠血清中SOD活性显著降低 ,MDA含量显著升高 (P <0 .0 1 ) ;而健身宝大、中剂量组与正常对照组相比较 ,小鼠血清中SOD活性显著升高 ,MDA含量显著降低 ,与衰老模型组相比较有显著性差异 (P <0 .0 5 )。结论 健身宝明显提升D -半乳糖拟衰小鼠血清中SOD活性 ,降低MDA含量 ,可从调节自由基代谢和提高抗氧化能力方面发挥延缓衰老的作用。  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