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   411篇
  免费   10篇
  国内免费   2篇
儿科学   52篇
妇产科学   1篇
基础医学   16篇
口腔科学   4篇
临床医学   26篇
内科学   105篇
皮肤病学   21篇
神经病学   47篇
特种医学   1篇
外科学   73篇
综合类   4篇
预防医学   8篇
药学   27篇
中国医学   6篇
肿瘤学   32篇
  2020年   3篇
  2017年   2篇
  2015年   5篇
  2014年   2篇
  2013年   2篇
  2012年   4篇
  2011年   5篇
  2010年   8篇
  2009年   15篇
  2008年   6篇
  2007年   10篇
  2006年   30篇
  2005年   11篇
  2004年   13篇
  2003年   9篇
  2002年   8篇
  2001年   4篇
  2000年   3篇
  1999年   9篇
  1998年   28篇
  1997年   20篇
  1996年   28篇
  1995年   31篇
  1994年   25篇
  1993年   25篇
  1992年   10篇
  1991年   10篇
  1990年   5篇
  1989年   4篇
  1987年   6篇
  1986年   13篇
  1985年   14篇
  1984年   6篇
  1983年   4篇
  1981年   2篇
  1980年   4篇
  1979年   6篇
  1978年   1篇
  1977年   1篇
  1972年   2篇
  1971年   3篇
  1970年   1篇
  1969年   1篇
  1966年   1篇
  1958年   2篇
  1957年   7篇
  1956年   4篇
  1955年   3篇
  1954年   2篇
  1949年   2篇
排序方式: 共有423条查询结果,搜索用时 15 毫秒
1.
2.
目的了解医科大学生口腔状况及卫生保健行为,分析相关影响因素。方法采用唾液隐血试验及问卷调查方式对192名医科大学生进行调查。结果卡方分析显示唾液隐血阳性率在性别间差异无显著性,但在不同学科专业间有显著性差异。且与牙龈病、牙列不齐显著相关。结论医科大学生的口腔卫生令人堪忧,口腔卫生实施效率较低,尤其特殊清洁工具应用较少,口腔卫生习惯、牙列状态、饮食、就医行为等是主要相关影响因素。  相似文献   
3.
Abstract:   Familial cases of interstitial pneumonia (FIP) have been reported to be linked to mutations of the surfactant protein C (SP-C) gene. Based on this knowledge, we evaluated the characteristics of patients with adult-onset FIP in the Tokyo area using clinical and radiopathological findings, and further evaluated the genetic background of patients with FIP compared with sporadic IP patients using genetic sequencing of the SP-C gene. A total of 22 patients with FIP from 13 families were identified, and the mean age at first diagnosis of these patients was 50 ± 2.7 years (range: 20–66 years). Based on the specimen histology, UIP and non-specific interstitial pneumonia accounted for 64 and 36%, respectively. Distribution of the interstitial pattern in HRCT imaging resulted in 36% upper lung dominant, 5% whole lung and 59% lower lung dominant. Two missense mutations in exon 4 (N138T) and exon 5 (N186S) were identified in the SP-C gene from 11 cases with FIP. Each exonic mutation consisted of DNA polymorphism. The frequencies of these DNA polymorphisms were evaluated among 11 subjects with FIP, 30 subjects with sporadic IP, and 43 healthy volunteers as controls. Interestingly, the genotype and allele frequencies in exon 5 were statistically different among these groups. In particular, the N186S substitution of exon 5 in the SP-C gene was shown in patients with FIP or sporadic IP, with a statistically higher frequency. While pathophysiological mechanisms remain to be elucidated, the N186S missense variant may have potential susceptibility in the development of IP. The gene or genes that prove to be important in the development of FIP may provide insights into the pathogenesis of other forms of interstitial lung diseases.  相似文献   
4.
Diastolic mitral regurgitation has been observed in patients with DDD pacemakers when the atrioventricular (AV) delay was prolonged. However, diastolic mitral regurgitation associated with first-degree AV block has not been fully studied. We examined transmitral blood flow in 24 patients with first-degree AV block and normal cardiac function (ages 35.3 ± 17.4 years), and in nine patients with DDD pacemakers and normal cardiac function (ages 73.1 ± 8.1 years), using pulsed Doppler echocardiography. Diastolic mitral regurgitation was observed in 19 of 24 patients with first-degree AV block. Although PQ interval was shortened from 0.32 ± 0.06 to 0.20 ± 0.05 seconds (P < 0.01) after 1 mg atropine sulfate IV, the interval between P wave (ECG) and the beginning of diastolic mitral regurgitation did not change, while the duration of diastolic mitral regurgitation was shortened from 0.15 ± 0.03 to 0.05 ± 0.03 seconds (P < 0.01). There was a significant correlation between changes in PQ interval and changes in the duration of diastolic mitral regurgifation (r = 0.92, P < 0.001). Although cardiac output (3.9 ± 0.05 L/min) and pulmonary capillary wedge pressure (5.1 ± 1.5 mmHg) were normal in all patients with pacemakers, diastolic mitral regurgitation was observed when the AV delay was prolonged. The critical PQ interval for the appearance of diastolic mitral regurgitation was 0.23 ± 0.01 seconds. In patients with prolonged PQ intervals, delayed ventricular contraction following atrial contraction may be associated with mitral regurgitation in the presence of a reversed AV pressure gradient. The results of this study suggest that diastolic mitral regurgitation occurs not only in patients with DDD pacemakers, but also with AAIR pacemakers when the PQ interval is prolonged. The occurrence of diastolic mitral regurgitation is associated with the pacing mode or the setting of AV delay.  相似文献   
5.
Summary.  Thrombopoietin (TPO) is an essential hematopoietic cytokine for megakaryopoiesis. In 2002, we demonstrated that pegylated-recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) increased platelet counts in patients with chronic immune thrombocytopenic purpura (ITP) in a Phase I/II clinical trial. After the cessation of clinical trials of PEG-rHuMGDF because of severe thrombocytopenia or pancytopenia due to the development of the neutralizing antibody cross-reacting with endogenous TPO, second generation non-immunogenic TPO receptor agonists have been developed. A small molecule eltrombopag and Romiplostim were approved for clinical use by FDA in 2008 to treat patients with chronic ITP who are refractory to the prior therapy. Although the efficacy of both TPO receptor agonists is convincing for the refractory ITP, further investigation is necessary to assess the potential long-term side effects and clinical applications of these therapies for other thrombocytopenic conditions.  相似文献   
6.
INTRODUCTION: Although it is desirable to know drug efficacy before initiating antiarrhythmic therapy, there have been no methods for this evaluation. P wave signal-averaged ECG (P-SAECG) is useful to detect subtle changes in disturbance of atrial conduction. The purpose of this present study was to test whether P-SAECG mapping system would give any information on the efficacy of disopyramide on the prevention of paroxysmal atrial fibrillation (PAF). METHODS AND RESULTS: P-SAECG was performed before disopyramide treatment, at 3 hours after a single dose of oral disopyramide (200 mg), and after 4 weeks of disopyramide treatment (300 mg/day). After measuring the filtered P wave duration by the vector magnitude and mapping methods, we calculated filtered P wave duration dispersion, difference between the maximal and minimal filtered P wave duration within 16 chest leads at these three time points. Filtered P wave duration and filtered P wave duration dispersion before treatment were longer in 32 patients with symptomatic PAF than in 31 healthy volunteers. Disopyramide was effective for suppression of PAF in 17 patients and ineffective in 15 patients after 4 weeks of treatment. Filtered P wave duration was similarly prolonged at 3 hours in the two groups, whereas filtered P wave duration dispersion at 3 hours after the disopyramide administration behaved differently; it decreased in all of the effective group and increased in all of the ineffective group. The effective patients were prospectively followed with the same treatment for 6 months. In 16 (94%) of these 17 effective patients, no PAF was documented and they remained to be asymptomatic. CONCLUSIONS: Thus, measuring filtered P wave duration dispersion with the P-SAECG mapping method after a single administration may predict the long-term efficacy of disopyramide in patients with PAF.  相似文献   
7.
Epidemiological surveys and animal experiments have shown that 2-bromopropane induces oligozoospermia in exposed workers and inhibits spermatogensis in laboratory animals. However, the mechanism by which 2-bromopropane exerts its effects is unknown. To this end, we examined the formation of testosterone by the Leydig cells and their survival of these cells in the presence of different concentrations of 2-bromopropane in vitro. Leydig cells were isolated following vascular perfusion, enzymatic dissociation and Percoll gradient centrifugation techniques. The cells were cultured in culture dishes. After 8 h, different cultures were exposed to 2-bromopropane at concentrations of 0.01 mmol/L, 0.10 mmol/L and 1.00 mmol/L. In order to stimulate Leydig cells to secrete testosterone, human chorionic gonadotropin (hCG) was also added. Cell viability was determined using the trypan blue dye exclusion test and cell numbers were counted by hemocytometer. Testosterone secretion was detected by radioimmunoassay. The cell viability decreased after exposure to 2-bromopropane in a dose-dependent way, but no morphological change was observed. The cell number decreased in the 2-bromopropane-treated cultures. The secretion of testosterone did not manifest detectable changes in the culture treated with 0.10 mmol/L and 0.01 mmol/L of 2-bromopropane; however, it decreased significantly (P<0.02) in the presence of 1.00 mmol/L. Therefore, our results strongly suggest that 2-bromopropane may exert its cytotoxic effects on Leydig cells in vitro. We speculate that the decrease in the numbers of Leydig cells caused by 2-bromopropane was mediated by a feedback mechanism resulting from a lower testosterone concentration.  相似文献   
8.
A 60‐year‐old man underwent routine colonoscopy, and was noted to have a pedunculated polyp in the sigmoid colon. The pathologic diagnosis was adenoma, and due to patient’s personal circumstances, the lesion was left untreated. The colonoscopic examination was repeated 4 years and 11 months later, to find that the polyp had transformed into an elevated lesion with irregularly depressed surface. The patient was diagnosed as having early sigmoid cancer, and underwent sigmoidectomy. The histologic examination of the excised specimen revealed well‐differentiated adenocarcinoma with invasion into the submucosal layer. Through studying the natural course of colon cancer, it has become known that the advanced cancers commonly develop from polyps with short pedicles (sessile polyps). This case represents an early sigmoid cancer developed from a pedunculated polyp, which differs from the current mainstream concept of ‘polyp‐cancer sequence of colon cancer.’  相似文献   
9.
10.
Abstract True incidence of this malformation is probably greater than that reported since the definitive diagnosis has been made at autopsy in most cases. Various hypotheses on the pathogenesis of tracheal agenesis have been proposed but they are still controversial.
In this report, we present a case of tracheal agenesis with a broncho-esophageal fistula and discuss the formal genesis.  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