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   29298篇
  免费   2118篇
  国内免费   188篇
耳鼻咽喉   465篇
儿科学   546篇
妇产科学   632篇
基础医学   4112篇
口腔科学   651篇
临床医学   2651篇
内科学   6223篇
皮肤病学   701篇
神经病学   2132篇
特种医学   1394篇
外科学   3951篇
综合类   885篇
现状与发展   2篇
一般理论   28篇
预防医学   1779篇
眼科学   941篇
药学   2086篇
中国医学   178篇
肿瘤学   2247篇
  2023年   298篇
  2022年   612篇
  2021年   1059篇
  2020年   609篇
  2019年   836篇
  2018年   1006篇
  2017年   691篇
  2016年   818篇
  2015年   1064篇
  2014年   1304篇
  2013年   1499篇
  2012年   2252篇
  2011年   2260篇
  2010年   1207篇
  2009年   1133篇
  2008年   1626篇
  2007年   1665篇
  2006年   1551篇
  2005年   1516篇
  2004年   1311篇
  2003年   1107篇
  2002年   970篇
  2001年   598篇
  2000年   570篇
  1999年   474篇
  1998年   210篇
  1997年   179篇
  1996年   132篇
  1995年   146篇
  1994年   137篇
  1993年   116篇
  1992年   194篇
  1991年   202篇
  1990年   172篇
  1989年   175篇
  1988年   156篇
  1987年   181篇
  1986年   135篇
  1985年   122篇
  1984年   110篇
  1983年   103篇
  1982年   69篇
  1979年   82篇
  1977年   64篇
  1975年   59篇
  1974年   65篇
  1973年   65篇
  1972年   60篇
  1971年   57篇
  1969年   62篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
OBJECTIVE: Many patients with haemorrhoids are investigated because of the fear of missing colorectal cancer (CRC). The aim of this study was to determine whether a primarily clinical approach regarding the need for investigation was safe and did not miss patients with CRC. PATIENTS AND METHODS: Data was collected prospectively on 589 consecutive patients with the principle diagnosis of haemorrhoids at first clinic visit. All had clinical assessment including rigid sigmoidoscopy and were treated by phenol injection or banding. They were categorized for (1) no review unless symptoms persisted -'One Stop SOS' (2) outpatient review or (3) investigation. To check for the development of CRC they were contacted by postal questionnaire or telephone interview with a minimum of one year from diagnosis and treatment. All 589 patients were cross-referenced with the Pathology database and the Hospital Information Services System. RESULTS: Four hundred and sixty-nine (80%) answered the questionnaire; 352 patients (60% of the total group) fell in the 'one stop SOS' outpatient category; 95 (16%) patients were followed up to review response to treatment for large haemorrhoids; 105 (18%) were investigated with barium enema (12%), flexible sigmoidoscopy (4%), colonoscopy (1%) and miscellaneous (1%); 37 (6%) patients were either given a haemorrhoidectomy date or referred on with a different diagnosis. No patients selected for 'one-stop' treatment developed CRC. Five (0.8%) patients were diagnosed with CRC after appropriate investigation was instituted for suspicious symptoms. One patient with distal transverse colon cancer had a delayed diagnosis as she was investigated initially by flexible sigmoidoscopy. CONCLUSION: Most patients with the primary diagnosis of symptomatic haemorrhoids do not need investigation.  相似文献   
42.
43.
BACKGROUND: Electron beam tomography coronary calcium imaging is an evolving technique for the early detection of coronary atherosclerosis, and recent studies have established its prognostic value in asymptomatic individuals. The relationship of coronary artery calcium scores (CAC) to obstructive coronary artery disease (CAD) has been poorly studied but is clinically relevant because it determines which individuals are likely to benefit from revascularization procedures. Hence, we prospectively evaluated the prevalence of myocardial ischemia in asymptomatic patients with cardiovascular risk factors and subclinical atherosclerosis. METHODS AND RESULTS: We studied 864 asymptomatic patients with no previous CAD but with cardiovascular risk factors, referred for electron beam tomography coronary calcium imaging to our institution over an 18-month period. From this group, 220 consecutive patients (85% men; mean age, 61 +/- 9 years; age range, 31-84 years) with moderate to severe atherosclerotic disease (coronary calcium score > or =100 Agatston units) were prospectively evaluated by technetium 99m sestamibi single photon emission computed tomography (SPECT). Patients were followed up (mean follow-up, 14 months) and data regarding their subsequent clinical management recorded. Of the 220 patients, 119 had moderate atherosclerosis (CAC score of 100-400 Agatston units) and 101 had severe atherosclerosis (CAC score > or =400 Agatston units). Abnormal SPECT findings were seen in 18% of patients with moderate atherosclerosis (n = 21) and 45% of patients with severe atherosclerosis (n = 45). Increasing severity of atherosclerosis was related to increasing ischemic burden (summed difference score = 1 +/- 0.2 for CAC score of 100-400 Agatston units and 3.2 +/- 0.5 for CAC score > or =400 Agatston units). In a multivariate linear regression model incorporating risk factors, CAC was the only predictor of silent ischemia. CONCLUSION: In comparison to previously published data, we detected a higher prevalence of silent ischemia even in patients with moderate coronary atherosclerosis (18%). This may reflect the differing risk factor profile of our patient population. When coronary calcium screening is used to preselect asymptomatic patients with cardiovascular risk factors for myocardial perfusion imaging, the optimum coronary calcium score threshold will depend on the population prevalence of risk factors and asymptomatic obstructive CAD.  相似文献   
44.
45.
46.
47.
This review presents objective data, as far as possible, about the current understanding of the biomechanics of the patellofemoral joint as it pertains to the management of patellofemoral problems. When faced with a patellofemoral malfunction, it is important to check all the soft-tissue and articular geometry factors relating to the patella locally and not to neglect the overall lower limb alignment and function. It is important to remember that small alterations in alignment can result in significant alterations in patellofemoral joint stresses and that changes in the mechanics of the patellofemoral joint can also result in changes in the tibiofemoral compartments. Surgical intervention for patellofemoral problems needs to be planned carefully and take into account an individual’s anatomy.  相似文献   
48.
The FIGNL1 gene was proven to be a new subfamily member of ATPases associated with diverse cellular activities (AAA proteins). In this in vitro study, the AAA proteins inhibited osteoblast proliferation and stimulated osteoblast differentiation. We showed that FIGNL1 may play some regulatory role in osteoblastogenesis. INTRODUCTION: The fidgetin-like 1 (FIGNL1) gene encodes a new subfamily member of ATPases associated with diverse cellular activities (AAA proteins). Although the FIGNL1 protein localizes to both the nucleus and cytoplasm, the function of FIGNL1 remains unknown. In a previous study, we identified several genes that mediate the anabolic effects of basic fibroblast growth factor (bFGF) on bone by using microarray data. FIGNL1 was one of the genes that downregulated >2-fold in MC3T3-E1 cells after treatment with bFGF. Therefore, this study was aimed to identify and confirm the function of FIGNL1 on osteoblastogenesis. MATERIALS AND METHODS: We examined the effect of the FIGNL1 gene on proliferation, differentiation, and apoptosis in mouse osteoblast cells (MC3T3-E1 and mouse primary calvarial cells) using flow cytometry, RT-PCR, cell proliferation assay, and cell death assay. MC3T3-E1 cells and mouse calvarial cells were transfected with small interfering RNA (siRNA) directed against the FIGNL1 or nontargeting control siRNA and examined by cell proliferation and cell death assays. Also, FIGNL1 was fused to enhance green fluorescent protein (EGFP), and the EGFP-fused protein was transiently expressed in MC3T3-E1 cells. RESULTS: Reduced expression of FIGNL1 by bFGF and TGF-beta1 treatment was verified by RT-PCR analysis. Overexpression of FIGNL1 reduced the proliferation of MC3T3-E1 and calvarial cells, more than the mock transfected control cells did. In contrast, siFIGNL1 transfection significantly increased the proliferation of osteoblasts, whereas overexpression of FIGNL1 did not seem to alter apoptosis in osteoblasts. Meanwhile, overexpression of FIGNL1 enhanced the mRNA expression of alkaline phosphatase (ALP) and osteocalcin (OCN) in osteoblasts. In contrast, siFIGNL1 decreased the expression of ALP and OCN. A pEGFP-FIGNL1 transfected into MCT3-E1 cells had an initially ubiquitous distribution and rapidly translocated to the nucleus 1 h after bFGF treatment. CONCLUSIONS: From these results, we proposed that FIGNL1, a subfamily member of the AAA family of proteins, might play some regulatory role in osteoblast proliferation and differentiation. Further analyses of FIGNL1 will be needed to better delineate the mechanisms contributing to the inhibition of proliferation and stimulation of osteoblast differentiation.  相似文献   
49.
AIMS: This study evaluates feasibility, safety, and efficacy of magnetic remote-controlled accessory pathway (AP) ablation. METHODS AND RESULTS: The novel magnetic navigation system (MNS) (Niobe, Stereotaxis) creates a steerable magnetic field (0.08 T) controlling the distal magnetic tip of an ablation catheter. In conjunction with a catheter advancer system (Cardiodrive, Stereotaxis) remote catheter ablation is enabled. Conventional electrophysiology study identified AP conduction in 59 patients (37 males, 36+/-14 years, 60 APs). First generation 1-magnet tip (1-M) (group I, n=18), second generation bipolar 3-magnet tip (3-M) (group II, n=27), and third generation quadripolar 3-magnet tip catheters (3-M quad.) (group III, n=14) were used for magnetic remote-controlled ablation. Successful AP ablation was achieved in 67% (group I), 85% (group II), and 92% (group III). A significant decrease of median [IQR: Q1-Q3] fluoroscopy time and dosage was observed: 21.2 [12.1-33.8] min, 1110 [395-3234] microGym2 (group I); 6.5 [4.4-15.4] min, 290 [129-489] microGym2 (group II), and 4.9 [3.4-8.0] min, 129 [74-270] microGym2 (group III). Mean procedure time (217+/-67 min; 182+/-68 min, and 172+/-90 min) significantly decreased in group III. Median number [Q1-Q3] of radiofrequency current applications in groups I, II, and III was 4 [2-9], 4 [2-6], and 2 [2-4], respectively. No complications occurred. CONCLUSION: Remote AP ablation is safe and feasible using the novel MNS. Introduction of the 3-magnet quadripolar ablation catheter significantly improved the efficacy of the procedure.  相似文献   
50.
OBJECTIVE: Hyperlipidemia is a permanent finding in advanced renal failure. It is supposed to be responsible for the accelerated arteriosclerosis and cardiovascular complications observed in patients with that disease. The background is partially determined, however, our knowledge in this matter is not yet satisfactory. METHODS: This study is based on the experimental rat model of chronic renal failure (CRF). Considering white adipose tissue (WAT) lipogenesis upregulation in CRF, along with the determination of acetyl coenzyme A carboxylase (ACC) and fatty acid synthase (FAS) genes expression, we have measured WAT gene expression for sterol regulatory binding protein 1 (SREBP-1) at the level of protein mass and mRNA abundance. Furthermore, we have determined glucose uptake, glucose-to-CO 2 conversion rate, and glucose translocator (GLUT-4) gene expression in WAT. RESULTS: Upregulation of both FAS and ACC gene expression was found in WAT of CRF rats. It was accompanied by WAT SREBP-1 gene overexpression. Moreover, we have observed the increased glucose uptake, glucose to CO 2 conversion rate, and GLUT-4 gene expression in WAT of CRF rats in comparison with controls. CONCLUSION: SREBP-1 gene overexpression may contribute to enhanced lipogenesis upregulation in WAT of CRF rats. It is not excluded that the increased WAT glucose metabolism activity is also induced by this mechanism, although there is no evidence currently to that end. We hypothesize that the increased WAT lipogenesis capacity could be a part of mechanism(s) leading to CRF-induced hyperlipidemia.  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