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   127910篇
  免费   12570篇
  国内免费   4400篇
耳鼻咽喉   821篇
儿科学   1949篇
妇产科学   1445篇
基础医学   23198篇
口腔科学   3072篇
临床医学   7948篇
内科学   19880篇
皮肤病学   2262篇
神经病学   13387篇
特种医学   3154篇
外国民族医学   35篇
外科学   9859篇
综合类   13212篇
现状与发展   23篇
预防医学   4800篇
眼科学   1355篇
药学   20700篇
  39篇
中国医学   4635篇
肿瘤学   13106篇
  2024年   347篇
  2023年   2243篇
  2022年   4920篇
  2021年   5670篇
  2020年   4813篇
  2019年   5004篇
  2018年   4840篇
  2017年   4873篇
  2016年   4656篇
  2015年   5313篇
  2014年   7728篇
  2013年   8302篇
  2012年   7155篇
  2011年   8460篇
  2010年   6810篇
  2009年   6874篇
  2008年   6832篇
  2007年   5899篇
  2006年   5106篇
  2005年   4625篇
  2004年   3976篇
  2003年   3501篇
  2002年   2702篇
  2001年   2220篇
  2000年   1889篇
  1999年   1721篇
  1998年   1681篇
  1997年   1619篇
  1996年   1426篇
  1995年   1325篇
  1994年   1202篇
  1993年   1131篇
  1992年   882篇
  1991年   790篇
  1990年   676篇
  1989年   586篇
  1988年   547篇
  1987年   517篇
  1986年   620篇
  1985年   868篇
  1984年   801篇
  1983年   622篇
  1982年   621篇
  1981年   524篇
  1980年   483篇
  1979年   391篇
  1978年   243篇
  1977年   206篇
  1976年   214篇
  1975年   133篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
71.
目的探讨16层螺旋CT(16层SCT)及其三维重建(3-D)与多平面重组(MPR)在胫骨平台骨折诊断中的应用价值。方法39例胫骨平台骨折病例经膝关节常规X线平片检查后,采用16层SCT进行膝关节的多层面螺旋CT扫描,在工作站上作3D及MPR影像后处理,就胫骨平台骨折的平片与16层SCT影像进行比较及综合分析。结果39例胫骨平台骨折中,X线平片漏诊1例髁间隆突骨折、1例内髁骨折及1例双髁骨折,此3例(7.69%)平片漏诊的骨折均为16层SCT予以诊断。16层SCT的3-D影像可清晰显示胫骨平台骨折的立体形态;MPR影像则可明确显示胫骨平台内部的骨质损伤情况如骨折的具体部位、关节面碎裂及塌陷程度、骨折移位距离。结论16层SCT能够显示X线平片难于诊断的胫骨平台隐匿性骨折;3-D及MPR成像技术十分有利于全面观察胫骨平台骨折的形态变化,是16层SCT横轴位扫描的重要补充。  相似文献   
72.
Abstract Myotonic dystrophy type 1 (DM1) is an autosomal dominant disease caused by a trinucleotide repeatexpansion, cytosine-thymine-guanine (CTG)n, in the 3′ untranslated region of a gene encoding the myotonic dystrophy protein kinase (DMPK). To correlate CTG expansion and protein expression, we studied muscle specimens from 16 adult DM1 patients using three anti-DMPK antibodies for immunoblotting. We estimated the amount of the full-length DMPK (85 kDa) in muscle biopsies from normal controls and from DM1 patients carrying different (CTG)n expansions. We found that DMPK concentration was decreased to about 50% in DM patients’ muscles; the protein decrease did not seem correlated with the CTG repeat length. However, the fibre type composition in skeletal muscle seemed somehow to affect DMPK decrease, as the lowest level of the enzyme was found in patients with the lowest content of type 1 fibre.  相似文献   
73.
对不同来源的脂肪酶进行了系统的筛选,并根据位置专一性的差别将脂肪酶分为1,3 特异的、1,3 选择性和非选择性的3类.采用LipozymeRMIM在无溶剂系统中催化甘油、脂肪酸合成1,3 sn 甘油二酯.研究表明脂肪酸、底物醇种类、温度、水分活度对LipozymeRMIM的活力有明显的影响.  相似文献   
74.
SK&F 86466, 6-chloro-3-methyl-2,3,4,5-tetrahydro-1-H-3-benzazepine, is a potent and selective antagonist of the α2-adrenoceptor in vitro. This compound produced a small pressor response accompanied by a marked bradycardia when administered i.v. to the pithed normotensive rat. The pressor response was not affected by reserpine treatment, pretreatment with α- or β-adrenoceptor antagonists, atropine, or hexamethonium. The bradycardia was markedly reduced by bilateral vagotomy and pretreatment with atropine and attenuated by hexamethonium. The negative chronotropic action of SK&F 86466 was abolished by a combination of vagotomy and atropine. Mediation of the bradycardia by a baroreceptor reflex was ruled out by the observations that a lack of change in heart rate was associated with the vasopressor response to phenylephrine in the pithed rat pretreated with propranolol. It is concluded that the negative chronotropic action of SK&F 86466 in the pithed rat is mediated indirectly by activation of the cholinergic innervation of the heart.  相似文献   
75.
越来越多的研究表明,维生素D除具有经典的调节钙磷平衡和维持骨骼健康的作用外,还具有其他更为广泛的骨外生物学效应,如调节免疫、抗肿瘤、保护中枢神经系统和防治代谢综合征等作用.本文就相关方面的研究进展进行综述.  相似文献   
76.
77.
BACKGROUND: The observation of photo-exposed skin under ultraviolet light reveals a mosaic pattern of varying intensity in epidermal melanization. Several patterns of mosaic subclinical melanoderma (MSM) have been described using a specially designed CCD camera and the ultraviolet light-enhanced visualization (ULEV) method. Vitamin D(3) and its analogues influence the biology of keratinocytes and melanocytes. OBJECTIVE: To assess the effect of calcipotriol on MSM. METHODS: This randomized split-face study was conducted in 27 men to compare the effect of once daily applications of 5% calcipotriol cream or a moisturizing cream on the heterogeneity of facial MSM. Computerized image analysis of video images was used at 1-month intervals before and during a 2-month treatment, as well as during a 3-month follow-up. RESULTS: At both sites, the average melanin content of the epidermis showed no significant change over time. However, the mottled appearance was smoothened at the calcipotriol site, whereas it was increased at the site receiving the moisturizer. CONCLUSION: The decreased heterogeneity in MSM after calcipotriol applications suggests a control of the epidermal melanocyte unit by the vitamin D(3) derivative.  相似文献   
78.
Poly (3-phenylthiophene) (P3PhT) films have been electrochemically synthesized by direct oxidation of 3-phenylthiophene in the electrolyte of pure boron trifluoride diethyl etherate (BFEE). The oxidation potential of the monomer was measured to be 1.29 V (vs. SCE), and about 0.15 V lower than that measured in a neutral medium of acetonitrile. Free-standing P3PhT film with tensile strength of 32–40 MPa has been obtained for the first time. The morphology and the structure of the polymer film have been studied by scanning electron microscopy, infrared and Raman spectroscopies. Raman spectral results demonstrated that the doping level of the P3PhT film increased with film thickness during electrochemical growth process.  相似文献   
79.
80.
AIMS: Diabetic ketoacidosis (DKA), a life-threatening acute complication of Type 1 diabetes, may be preventable with frequent monitoring of glycaemia and ketosis along with timely supplemental insulin. This prospective, two-centre study assessed sick day management using blood 3-hydroxybutyrate (3-OHB) monitoring compared with traditional urine ketone testing, aimed at averting emergency assessment and hospitalization. METHODS: One hundred and twenty-three children, adolescents and young adults, aged 3-22 years, and their families received sick day education. Participants were randomized to receive either a blood glucose monitor that also measures blood 3-OHB (blood ketone group, n = 62) or a monitor plus urine ketone strips (urine ketone group, n = 61). All were encouraged to check glucose levels > or = 3 times daily and to check ketones during acute illness or stress, when glucose levels were consistently elevated (> or = 13.9 mmol/l on two consecutive readings), or when symptoms of DKA were present. Frequency of sick days, hyperglycaemia, ketosis, and hospitalization/emergency assessment were ascertained prospectively for 6 months. RESULTS: There were 578 sick days during 21,548 days of follow-up. Participants in the blood ketone group checked ketones significantly more during sick days (276 of 304 episodes, 90.8%) than participants in the urine ketone group (168 of 274 episodes, 61.3%) (P < 0.001). The incidence of hospitalization/emergency assessment was significantly lower in the blood ketone group (38/100 patient-years) compared with the urine ketone group (75/100 patient-years) (P = 0.05). CONCLUSIONS: Blood ketone monitoring during sick days appears acceptable to and preferred by young people with Type 1 diabetes. Routine implementation of blood 3-OHB monitoring for the management of sick days and impending DKA can potentially reduce hospitalization/emergency assessment compared with urine ketone testing and offers potential cost savings.  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