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   7871篇
  免费   431篇
  国内免费   48篇
耳鼻咽喉   81篇
儿科学   188篇
妇产科学   198篇
基础医学   1237篇
口腔科学   164篇
临床医学   804篇
内科学   1593篇
皮肤病学   85篇
神经病学   567篇
特种医学   762篇
外国民族医学   2篇
外科学   894篇
综合类   38篇
一般理论   1篇
预防医学   442篇
眼科学   80篇
药学   520篇
中国医学   8篇
肿瘤学   686篇
  2022年   56篇
  2021年   135篇
  2020年   70篇
  2019年   105篇
  2018年   120篇
  2017年   90篇
  2016年   120篇
  2015年   132篇
  2014年   194篇
  2013年   234篇
  2012年   386篇
  2011年   323篇
  2010年   190篇
  2009年   203篇
  2008年   326篇
  2007年   363篇
  2006年   371篇
  2005年   344篇
  2004年   332篇
  2003年   315篇
  2002年   324篇
  2001年   355篇
  2000年   336篇
  1999年   244篇
  1998年   108篇
  1997年   102篇
  1996年   67篇
  1995年   57篇
  1994年   43篇
  1993年   50篇
  1992年   133篇
  1991年   152篇
  1990年   129篇
  1989年   152篇
  1988年   125篇
  1987年   119篇
  1986年   98篇
  1985年   107篇
  1984年   76篇
  1983年   64篇
  1982年   45篇
  1979年   91篇
  1978年   50篇
  1977年   48篇
  1976年   51篇
  1975年   47篇
  1974年   67篇
  1973年   62篇
  1972年   57篇
  1970年   55篇
排序方式: 共有8350条查询结果,搜索用时 15 毫秒
11.
The aim of the study was to investigate changes in the micromorphologyl and microhardness of the enamel surface after bleaching with two different concentrations of hydrogen peroxide (HP) and carbamide peroxide (CP). Bovine enamel samples were embedded in resin blocks, and polished. Specimens in the experimental groups (n = 10) were treated with bleaching gels containing 10% CP, 35% CP, 3.6% HP, and 10% HP, respectively, for 2 h every second day over a period of 2 weeks. The gels had the identical composition and pH and differed only in their HP or CP content. The roughness and morphology of the enamel surface were analyzed using laser profilometry and SEM. Microhardness was measured using a Knoop hardness tester. The data were evaluated statistically. Specimens in the 10% HP group showed significantly higher roughness after bleaching compared to the control group (ΔRa, p = 0.01). Bleaching with 35% CP showed only a tendency to increase roughness (ΔRa, p = 0.06). Application of 10% CP or 3.6% HP had no significant influence on Ra. Enamel microhardness was significantly higher after application of 10% HP compared to the control (ΔMic = 8 KHN, p = 0.0002) and 35% CP (ΔMic = 20KHN, p = 0.01) groups. In summary, application of CP and HP showed only small quantitative and qualitative differences. In addition, the influence of bleaching procedure on the morphology and hardness of the enamel surface depended on the concentration of the active ingredients.  相似文献   
12.
PURPOSE: Although the efficacy of PepGen P-15 particulate has been conclusively demonstrated in two multicenter clinical studies, the effect of a new hydrogel formulation containing PepGen P-15 on bone repair has not been previously demonstrated. MATERIALS AND METHODS: PepGen P-15 Flow contains PepGen P-15 particulate in a biocompatible hydrogel, which provides spacing between the particles. In this case study, bone repair of both PepGen P-15 particles and PepGen P-15 Flow was compared to natural bone in same-mouth extraction sockets. RESULTS: The radiographic, histologic, and histomorphometric evaluations showed enhanced bone formation and faster particle resorption with PepGen P-15 Flow compared to the PepGen P-15 particulate. CONCLUSION: The accelerated bone formation by PepGen P-15 Flow may provide faster implant placement.  相似文献   
13.
OBJECTIVES: The aims of the present study were to evaluate the frequent clinical complaints of oral submucous fibrosis (OSF) and to develop a scoring system for early detection of the disease by a self-administered questionnaire. METHODS: A total of 296 subjects were recruited, including 123 OSF patients without oral cancer and 173 betel quid chewers without OSF or oral cancer. A self-administered questionnaire was used to collect the symptom profile from study subjects. Their maximal mouth opening (MMO) between upper and lower incisor edges was measured and recorded by well-trained nurses. A binary logistic regression model examining the likelihood of OSF based on the eight symptoms of interest was used to develop the scoring system. RESULTS: Among 79 OSF subjects with an MMO < 35 mm, the most frequent complaint was trismus (87.3%), followed by burning sensation (76.0%) and xerostomia (72.2%). Among 44 OSF subjects with an MMO > or = 35 mm, burning sensation (68.2%) was the most frequent complaint, followed by trismus (54.5%) and xerostomia (54.5%). Six frequent complaints including trismus, burning sensation, xerostomia, sore throat, numbness, and oral ulceration were utilized to develop a scoring system for the early detection of OSF. The scoring system had an area under the receiver operating characteristic curve of 0.90. CONCLUSION: This study suggests a screening questionnaire of frequent complaints for the early detection of OSF.  相似文献   
14.
This in vitro study evaluated the influence of one halogen and two light-emitting diode (LED) curing units on the curing depth of a conventional hybrid and two translucent resin composites by measuring the Knoop microhardness. In the first part of the study, a conventional hybrid resin composite and three curing units (one halogen: 40 s polymerization time, two LEDs: 10 and 20 s) were used. Ten cylindrical resin composite samples were prepared for each curing unit and each polymerization time tested. After polymerization, the soft part of the samples was removed. The samples were embedded in a polyacrylic resin and separated in the middle towards the direction, top–bottom. On the section plane, Knoop microhardness measurements were performed every 1 mm, starting at 0.5 mm under the surface. In the second part of the study, two translucent resin composites and a conventional hybrid composite resin were cured with the three curing units, and the microhardness was measured as mentioned above. The difference between the curing units tested was found statistically significant (p = 0.0009), as well as the difference between the materials concerning curing depth (p = 0.0001). Both translucent materials achieved microhardness values equal to the 80% of the surface values, in depths 3.5–5.5 mm, depending on the curing units used.  相似文献   
15.
16.
17.
18.
Aim: To assess the correlation between the amino-terminal pro-hormone brain natriuretic peptide (NT-proBNP) concentration in blood and urine during a period when actively adjusting the treatment of heart failure (HF). Methods: Plasma and urine analyses of NT-proBNP were compared in 51 patients on admission to and discharge from a nurse-led outpatient clinic where HF treatment was optimized. The median time between the two measurements was 42 days. Correlations were analyzed using linear regression, where R2 is the degree of variability in the plasma NT-proBNP concentration that can be accounted for by the urinary NT-proBNP. Results: There was a statistically significant linear relationship between the urine and plasma concentrations of NT-proBNP on both occasions, but R2 varied greatly depending on how the data were presented. The correlation between the raw data showed an R2 of only 30%, and it almost doubled upon logarithm transformation, which shows that the variability (error) was concentration-dependent. Correction of the urinary NT-proBNP for urinary creatinine further increased R2 for the logarithm-transformed correlation to 68% on admission and 76% on discharge. The highest R2 (77%) was obtained when the relative changes in urinary NT-proBNP/creatinine between admission and discharge were compared with the corresponding relative changes in the plasma concentration. The sensitivity and specificity of the urine in indicating plasma concentration changes?>?10% were 82% and 86%, respectively. Conclusion: Relative changes in plasma NT-proBNP could be reliably estimated from urine samples during a period of optimization of HF treatment.  相似文献   
19.
BACKGROUND: Pneumoperitoneum after cardiopulmonary resuscitation may be due to mediastinal air tracking into the peritoneal cavity via the diaphragmatic hiatus or to gastric perforation. CASE REPORT: A 79-year-old woman received Advanced Cardiac Life Support measures in the intensive care unit. Chest compressions and endotracheal intubation were performed; a stable cardiac rhythm and perfusion were restored. A chest radiograph after resuscitation revealed pneumoperitoneum without pneumomediastinum. The patient underwent laparotomy; a 6-cm perforation of the posterior gastric wall along the lesser curve was detected and repaired. CONCLUSION: Gastric perforation after cardiopulmonary resuscitation should be suspected when chest radiographs obtained after resuscitation show pneumo-peritoneum without pneumomediastinum. Prompt laparotomy allows detection of gastric perforations and decreases the morbidity associated with rupture of a hollow organ. The incidence of gastric perforation after cardiopulmonary resuscitation may be decreased with early endotracheal intubation, avoidance of esophageal intubation, and expeditious placement of an orogastric tube.  相似文献   
20.
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