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   1128篇
  免费   71篇
  国内免费   8篇
耳鼻咽喉   7篇
儿科学   24篇
妇产科学   18篇
基础医学   255篇
口腔科学   16篇
临床医学   113篇
内科学   353篇
皮肤病学   20篇
神经病学   63篇
特种医学   13篇
外科学   110篇
综合类   5篇
预防医学   38篇
眼科学   4篇
药学   95篇
中国医学   3篇
肿瘤学   70篇
  2023年   5篇
  2022年   33篇
  2021年   34篇
  2020年   24篇
  2019年   21篇
  2018年   28篇
  2017年   20篇
  2016年   25篇
  2015年   28篇
  2014年   39篇
  2013年   55篇
  2012年   83篇
  2011年   96篇
  2010年   66篇
  2009年   48篇
  2008年   75篇
  2007年   90篇
  2006年   81篇
  2005年   64篇
  2004年   69篇
  2003年   57篇
  2002年   54篇
  2001年   7篇
  2000年   7篇
  1999年   6篇
  1998年   8篇
  1997年   8篇
  1996年   5篇
  1995年   11篇
  1994年   9篇
  1993年   8篇
  1992年   4篇
  1988年   3篇
  1986年   1篇
  1984年   1篇
  1983年   3篇
  1982年   6篇
  1981年   3篇
  1980年   4篇
  1979年   3篇
  1977年   3篇
  1975年   2篇
  1974年   1篇
  1971年   1篇
  1968年   1篇
  1967年   1篇
  1966年   2篇
  1965年   1篇
  1963年   1篇
  1942年   1篇
排序方式: 共有1207条查询结果,搜索用时 15 毫秒
41.
The water-filled tree hole fauna of biting midges (Diptera: Ceratopogonidae) in Slovakia is documented for the first time. Three Culicoides Latreille and two Dasyhelea Kieffer species were reared from these habitats. Epidemiological significance of C. obsoletus (Meigen, 1818) is briefly discussed.  相似文献   
42.
This paper describes the enhancement of the existing predictive system of quality management in the processes of metallurgic manufacturing. Specifically, it addresses steel-strip manufacturing. The main quality management innovation is the transition from the current methodological process of a single-step defect evaluation to a two-step evaluation. A two-step defect check of the strip’s surface involves checking for defects during the hot-rolling process first, and double-checking it during the process of pickling. These defects are detected in a well-established process of camera imaging in the production process. The recorded image is then processed mathematically to find the degree of defect correlation in those processes. The two-step evaluation enables a more detailed focus on a particular defect and its position on the strip. Decisions concerning further processing are based on defect evaluation, for instance, whether a rework is necessary to maximize the product utilization and minimize the eventual negative impact of the defect on production equipment. A crucial aspect is also the reduced probability of failures in the manufacturing process.  相似文献   
43.
OBJECTIVES: The purpose of this work was to establish the normal range of maximal renal hyperemic response in humans and to identify the ideal renal vasodilatory stimuli. BACKGROUND: Stenotic renovascular atherosclerosis is increasingly treated by percutaneous transluminal renal intervention but with an unpredictable outcome. This may be due to hemodynamically non-significant stenosis or the presence of irreversible damage to the glomerular circulation. We propose that the renovascular hyperemic response may help identify appropriate patients. METHODS: In 28 normotensive patients, quantitative angiographic measurements of the renal artery were obtained, and renal artery pressure and flow velocity were continuously recorded after various hyperemic agents. RESULTS: In a first group of 11 patients, a significant increase in renal artery average peak velocity (APV) was observed after intrarenal (IR) bolus injection of 600 microg isosorbide dinitrate (41 +/- 19%), 30 mg papaverine (50 +/- 34%), 50 microg dopamine (94 +/- 54%), 0.8 microg x kg(-1) fenoldopam (80 +/- 25%), and during IR infusion of 1 microg x kg(-1) x min(-1) fenoldopam (86 +/- 28%). A second group of 17 patients received intravenous infusion of dopamine (3, 5, 10, 20, 30, and 40 microg x kg(-1) x min(-1)). The 3 and 5 microg x kg(-1) x min(-1) of dopamine modestly reduced renal resistance index (RI) (-13 +/- 15% and -25 +/- 20%, respectively). At higher dosages, no further decline in RI was observed. No significant change in vessel diameter was observed before and after the administration of the pharmacological stimuli suggesting that changes in APV corresponded with changes in absolute renal blood flow. CONCLUSIONS: The normal renal flow reserve averages approximately 2 in humans with normal renal function. An IR bolus injection of 50 microg x kg(-1) of dopamine is the most convenient means to elicit maximal renal hyperemia.  相似文献   
44.
AIM: To evaluate the impact of chemoradiation admi- nistered pre- or postoperatively on prognosis in females following R0 extended resection with sphincter- preserving total mesorectal excision (TME) for locally advanced rectal cancer and to assess the association between chemoradiation and intra- and postoperative variables. METHODS: Twenty-one females were treated for locally advanced but preoperatively assessed as primarily resectable rectal cancer involving reproductive organs. Anterior resection with TME and excision of internal genitalia was combined with neo- or adjuvant chemoradiation. Two-year disease-free survival analysis was performed with the Kaplan-Meier method and log- rank test. The association between chemoradiation and other variables was evaluated with the Fisher’s exact test and Mann-Whitney test. RESULTS: Survival rate decreased in anaemic females (51.5% vs 57.4%), in patients older than 60 years (41.8% vs 66.7%) with poorly differentiated cancers (50.0% vs 55.6%) and tumors located ≤ 7 cm from the anal verge (42.9% vs 68.1%) but with the lack of importance. Patients with negative lymph nodes and women chemoradiated preoperatively had significantly favourable prognosis (85.7% vs 35.7%; P= 0.03 and 80.0% vs 27.3%; P = 0.01, respectively). Preoperative chemoradiation compared to adjuvant radiochemotherapy was not significantly associated with the duration of surgery, incidence of intraoperative bowel perforation and blood loss ≥ 1 L, rate of postoperative bladder and anorectal dysfunction, and minimal distal resection margin. It significantly influenced minimal radial margin (mean 4.2 mm vs 1.1 mm; P < 0.01). CONCLUSION: Despite involving internal genitalia, long-term disease-free survival and sphincter preservation may be achieved with combined-modality therapy for females with T4 locally advanced rectal carcinoma. Neoadjuvant chemoradiation does not compromise functional results and may significantly improve oncological outcomes probably due to enhanced radial clearance.  相似文献   
45.
46.
To validate echocardiographic left atrial volume measurements, 25 patients with mitral stenosis were studied before and after mitral balloon valvuloplasty. Seven normals served as controls. The modified Simpson's rule was used for echocardiographic and angiographic left atrial volume determination from two orthogonal planes. Left atrial antero-posterior diameter was measured from parasternal long axis view and supero-inferior and medio-lateral diameters from apical four-chamber view. Transthoracic echocardiographic left atrial volume correlated well, but systematically underestimated angiographic left atrial volume (y=0.4x+27, r=0.92). Monoplane transesophageal echocardiography did not improve correlation, nor the underestimation. Out of the several left atrial diameters, antero-posterior dimension showed the closest correlation with angiographic volume (r=0.91), which persisted after exclusion of patients with atria >400 ml (r=0.84). Futhermore, relative changes of antero-posterior diameter after mitral valvuloplasty were closely related to the relative changes observed in left atrial volume (r=0.82). Our results suggest that, in spite of a consistent underestimation, bidimensional, transthoracic echocardiographic and angiographic left atrial assessment correlate closely. Moreover, it is suggested that the mere antero-posterior diameter from transthoracic two-dimensional image is sufficient in clinical practice for routine follow-op of left atrial volume.  相似文献   
47.
OBJECTIVE: To study the effect of dietary cholesterol withdrawal on size and composition of LDL-hypercholesterolemia-induced coronary plaques in miniature pigs. METHODS: Pigs were on normal chow (control group), on a cholesterol-rich diet for 37 weeks (hypercholesterolemic group) or on a cholesterol-rich diet followed by normal chow for 26 weeks (cholesterol withdrawal group). Endothelial function was assessed with quantitative angiography after intracoronary infusion of acetylcholine, plaque load with intra-coronary ultrasound and plaque composition with image analysis of cross-sections. The effect of porcine serum on coronary smooth muscle cell (SMC) function was studied in vitro. RESULTS: Cholesterol-rich diet caused LDL-hypercholesterolemia, increased plasma levels of oxidized LDL (ox-LDL) and C-reactive protein (CRP), and induced endothelial dysfunction and coronary atherosclerosis. Dietary cholesterol withdrawal lowered LDL, ox-LDL and CRP. It restored endothelial function, did not affect plaque size but decreased lipid, ox-LDL and macrophage content. Smooth muscle cells and collagen accumulated within the plaque. Increased smoothelin-to-alpha-smooth muscle actin ratio indicated a more differentiated SMC phenotype. Cholesterol lowering reduced proliferation and apoptosis. In vitro, hypercholesterolemic serum increased SMC apoptosis and decreased SMC migration compared to non-hypercholesterolemic serum. CONCLUSIONS: Cholesterol lowering induced coronary plaque stabilization as evidenced by a decrease in lipids, ox-LDL, macrophages, apoptosis and cell proliferation, and an increase in differentiated SMC and collagen. Increased migration and decreased apoptosis of SMC may contribute to the disappearance of the a-cellular core after lipid lowering.  相似文献   
48.
Brain and other natriuretic peptides: molecular aspects   总被引:16,自引:0,他引:16  
Natriuretic peptides have emerged as important candidates for development of diagnostic tools and therapeutic agents in cardiovascular disease. The family contains of three major peptides-ANP, BNP, CNP-that participate in cardiovascular and cardiorenal homeostasis. Each of these natriuretic peptides binds differentially to specific receptors that signal through different mechanisms. They are cleared enzymatically by neutral endopeptidase as well as by receptor-mediated endocytosis. Because of its fast induction and specific expression in overt heart failure, BNP seems the most promising natriuretic peptide. It is predominantly synthesized in the cardiac ventricles, released as pre-proBNP and then enzymatically cleaved to BNP and the N-terminal portion of BNP(NT-proBNP). Blood measurements of BNP and NT-proBNP have been shown to identify patients with LV dysfunction. This review focuses on the physiology of natriuretic peptides as a group and brain natriuretic peptide in more detail, its structure and regulation as well as its effects at the cellular level.  相似文献   
49.
OBJECTIVES: To assess ductus venosus (DV) indices during the first stage of labor and the effect of ruptured membranes, meconium stained liquor and epidural analgesia (EDA). METHODS: Prospective cross-sectional study. Eighty-one women with low-risk singleton term pregnancies participated, 51 had normal labor (Group 1), and 30 experienced ruptured membranes and/or stained liquor (Group 2). Of the latter group 14 received EDA. The effect of various interventions and application of EDA on the ductus venosus index (DVI) and pulsatility index for veins (DV PIV) were tested. RESULTS: The feasibility rate was 94%. A significant increase of DV indices (DVI, DV PIV) was found in group 2 (P<0.001 and P<0.0005, respectively). The A-velocity was also significantly lower in group 2 (P<0.02). A markedly significant increase of DV indices (P<0.0001) among participants receiving EDA was observed in group 2. The mean+/-SD indices were: 0.53+/-0.10 for the DVI and 0.68+/-0.14 for the DV PIV in those women. There was a significant positive correlation of DV indices with the duration of amniorrhea in group 2 (PIV: r=0.66; P<0.002; DVI: r=0.68; P<0.001). CONCLUSIONS: Long-term amniorrhea seems to affect the fetal venous circulation reflected in increased DV waveform indices.  相似文献   
50.
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