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   47312篇
  免费   3324篇
  国内免费   184篇
耳鼻咽喉   606篇
儿科学   1116篇
妇产科学   906篇
基础医学   5652篇
口腔科学   1145篇
临床医学   5189篇
内科学   9814篇
皮肤病学   468篇
神经病学   3815篇
特种医学   1535篇
外国民族医学   3篇
外科学   7878篇
综合类   740篇
一般理论   31篇
预防医学   4143篇
眼科学   1475篇
药学   3238篇
中国医学   46篇
肿瘤学   3020篇
  2023年   236篇
  2022年   379篇
  2021年   865篇
  2020年   524篇
  2019年   804篇
  2018年   927篇
  2017年   675篇
  2016年   791篇
  2015年   926篇
  2014年   1348篇
  2013年   2004篇
  2012年   2907篇
  2011年   2993篇
  2010年   1720篇
  2009年   1558篇
  2008年   2664篇
  2007年   2791篇
  2006年   2765篇
  2005年   2925篇
  2004年   2788篇
  2003年   2581篇
  2002年   2449篇
  2001年   561篇
  2000年   509篇
  1999年   618篇
  1998年   603篇
  1997年   512篇
  1996年   439篇
  1995年   421篇
  1994年   349篇
  1993年   327篇
  1992年   427篇
  1991年   440篇
  1990年   344篇
  1989年   313篇
  1988年   285篇
  1987年   305篇
  1986年   298篇
  1985年   338篇
  1984年   373篇
  1983年   353篇
  1982年   415篇
  1981年   390篇
  1980年   355篇
  1979年   253篇
  1978年   260篇
  1977年   244篇
  1976年   257篇
  1975年   197篇
  1973年   217篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
There are few data concerning the complications and technical difficulties encountered when cardiac catheterization is performed using peripheral bypass grafts for vascular access. All cardiac catheterizations performed at our institution from January 1, 1984 to April 1, 1991 were retrospectively reviewed to assess the in-hospital clinical outcomes in patients who had arterial access for catheterization achieved via prosthetic graft puncture. Seventeen procedures had percutaneous puncture of a vascular graft from a total of 2,929 arterial catheterizations performed. The interval from graft placement to catheterization was 7.5 ± 1.1 years. Arterial sheaths were employed in all cases and corresponded to the catheter size, with 5F systems used in 53% and 7F or larger systems used in the remaining patients. No intraprocedural or postprocedural complications were recognized. Technical difficulties were limited to the inability to selectively cannulate a nondominant right coronary artery in 1 patient. We conclude that percutaneous introduction of an arterial sheath and left heart catheterization via remotely implanted vascular bypass grafts is not associated with an increased risk of procedural complications or technical difficulties. © 1993 Wiley-Liss, Inc.  相似文献   
992.
Since April 1976, nine infants less than 1 month of age underwent a Mustard intraatrial baffle procedure. All had transposition of the great arteries and were persistently symptomatic or hypoxic after the Rashkind balloon atrioseptostomy. Two had an associated large ventricular septal defect patched at the time of physiologic correction. The average age of the infants was 11.6 days (range 36 hours to 28 days). Weight averaged 3.4 kg (range 2.5 to 4.2). In all the Mustard procedure was performed using deep hypothermie circulatory arrest, averaging 71 minutes (range 48 to 88) at a mean core temperature of 13 °C. An average of 2.8 days of postoperative ventilatory assistance was required. One death occurred in a 28 day old male infant with an associated ventricular septal defect who, the morning after operation, had a sudden unresponsive cardiac standstill. The postoperative hospitalization period averaged 15 days (range 10 to 23). Follow-up evaluation has extended from 4 to 63 months (average 31). Six patients were restudied 2 to 21 months postoperatively. One had obstruction of the superior limb of the baffle, which had separated from the right atrial wall permitting a modest right to left shunt. She has had uneventful repair employing a unique modification of Senning's operation. Another child has asymptomatic partial obstruction of the superior limb of the baffle demonstrated angiographically. None has pulmonary venous obstruction and all have prevailing normal sinus rhythm. Significant right ventricular dysfunction has been demonstrated in one. Early correction in these persistently symptomatic or hypoxic neonates with transposition of the great arteries with or without a ventricular septal defect has obviated the need for palliative operations and produced gratifying early and late results.  相似文献   
993.
BACKGROUND: Heart failure (HF) occurs more frequently and is a significant cause of mortality in diabetic patients. The purpose of the current study is to ascertain risk factors that are predictive of HF hospitalizations in type 2 diabetic patients. METHODS: Longitudinal observational study of type 2 diabetic patients with baseline diastolic blood pressures > or =80 mm Hg and no history of New York Heart Association class III-IV HF or a serum creatinine > or =2.5 mg/dL nested within a randomized clinical trial. The outcome measure of this study was the first occurrence of HF hospitalization over a 5-year follow-up period. RESULTS: Patients with overt albuminuria at baseline had a higher and earlier occurrence of HF hospitalizations than those with micro- or normoalbuminuria (13.6% versus 3.3%, odds ratio [OR]=3.1, 95% confidence interval [CI]=2.15-4.60, P<.0001). In the multiple logistic regression analyses, the presence of overt albuminuria (OR 5.4, 95% CI=2.3-12.5, P<.001), history of myocardial infarction (OR 4.6, 95% CI=1.6-13.1, P=.004) and a history of New York Heart Association Class I or II HF (OR 8.0, 95% CI=2.2-28.6, P=.0014) at baseline were independently associated with HF hospitalizations. CONCLUSIONS: Overt albuminuria predicts the occurrence of HF hospitalizations in type 2 diabetic patients. Thus early aggressive treatment of diabetic nephropathy should be investigated as a means of preventing of HF.  相似文献   
994.
Radiofrequency catheter ablation (RCA) of septal accessory pathways may be technically challenging in children due to the risk of inadvertent atrioventricular (AV) block in the setting of small cardiac dimensions. Outcomes were reviewed for all patients aged < or =19 years with manifest and concealed septal accessory pathways undergoing RCA since 1990 at a single institution. One hundred forty-five procedures were performed in 127 patients (mean age 11.6 years). The number of studies according to accessory pathway location were: anteroseptal (n = 36), midseptal (n = 20), mouth of coronary sinus (n = 40), middle cardiac vein (n = 6), right posteroseptal (n = 21), and left posteroseptal (n = 22). Ablation was deferred for 9 patients (6 anteroseptal and 3 midseptal) in favor of additional pharmacologic trials. Acute success rates for targeted accessory pathways were: anteroseptal (96%), midseptal (94%), mouth of coronary sinus (88%), middle cardiac vein (100%), right posteroseptal (100%), and left posteroseptal (96%). Recurrence rates during follow-up were: anteroseptal (14%), midseptal (12%), mouth of coronary sinus (3%), right posteroseptal (4%), and left posteroseptal (4%). Permanent second or third degree AV block occurred in 4 of 136 RCA attempts (3%), involving 2 anteroseptal and 2 midseptal pathways. In 3 of these 4 cases, a high probability of block was anticipated from prior ablation efforts, prompting pacemaker insertion before or in conjunction with RCA. Thus, in the pediatric age group, acute RCA success rates for septal accessory pathways can exceed 90%. The risks of AV block and accessory pathway recurrence are most relevant to anteroseptal and midseptal pathways. These data may be factored into patient selection and the decision whether to ablate.  相似文献   
995.
996.
To investigate the relationships between serum concentrations of soluble adhesion molecules and hyperglycemia, insulin resistance, or other conventional risk factors in type 2 diabetes, we measured soluble intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), E-selectin (sE-selectin), insulin sensitivity, and conventional risk factors in 150 Japanese type 2 diabetic patients without apparent diabetic macroangiopathy. High serum concentrations of sVCAM-1 and sE-selectin were observed in patients with type 2 diabetes. Serum concentrations of soluble adhesion molecules were not significantly influenced by sex, hypertension, dyslipidemia, or microangiopathy. Spearman correlation showed that sVCAM-1 concentrations correlated significantly with fasting plasma glucose (FPG), fasting C-peptide, and insulin sensitivity [K index of the insulin tolerance test (K(ITT))] (rho=0.19,0.23, and -0.23, respectively). Soluble E-selectin concentrations correlated significantly with body mass index (BMI), FPG, fasting C-peptide, insulin sensitivity, and triglyceride (rho=0.33,0.42,0.26,-0.48, and 0.29, respectively). Multiple regression analysis showed that FPG, fasting C-peptide, and total cholesterol were independent factors that correlated with sVCAM-1 levels. BMI, FPG, and insulin sensitivity were independent factors that correlated with sE-selectin levels. Serum concentrations of sE-selectin significantly increased associated with clustering of conventional risk factors those obesity, hypertension, dyslipidemia, and current smoking (P<0.01). Thus, sVCAM-1 and sE-selectin levels are related to both hyperglycemia and insulin resistance. Soluble E-selectin levels may be related to obesity, hyperglycemia, and insulin resistance and may reflect the presence of a multiple risk factor clustering syndrome.  相似文献   
997.
Postmortem examinations of the hypothalamus of patients with autosomal dominant neurohypophyseal diabetes insipidus (adNDI), which have been reported only on persons dying between the ages of 37-87 yr, reveal the presence of the arginine vasopressin (AVP)-producing parvocellular neurons but the absence of 95% of the expected AVP-producing magnocellular neurons. To determine whether the clinical course of adNDI is compatible with the hypothesis that the neuropathologic findings are attributable to a progressive loss of magnocellular neurons beginning in early life, we performed posterior pituitary magnetic resonance imaging and water deprivation tests, including plasma ACTH measurements, on 17 affected members of a kindred with the deltaE47 neurophysin mutation whose ages ranged from 3 months to 54 yr. Nine adult nonaffected members (ages, 20-56 yr) underwent these tests as controls. All six children undergoing magnetic resonance imaging demonstrated a posterior pituitary hyperintense signal (PPHS). Eight of nine affected adults showed an absent or barely visible PPHS, whereas eight of nine age-matched nonaffected adults produced a normal size PPHS. During water deprivation tests, infants concentrated their urine normally, and a 3-month-old infant produced a high plasma AVP level of 15.7 pmol/liter. By school age, affected children were no longer able to concentrate their urine or prevent hypernatremia. Affected adults became dehydrated; their median plasma AVP level was less than 1.0 pmol/liter, but their median fasting plasma ACTH was 2-fold greater than the level of nonaffected adults (10.0 vs. 5.0 pmol/liter; P = 0.008). These results suggest that adNDI is a progressive disease associated with chronic loss of the magnocellular neurons that supply AVP to the posterior pituitary but preservation of the parvocellular neurons that supply AVP and CRH to the median eminence and stimulate ACTH production during hypernatremia.  相似文献   
998.
PURPOSE: To evaluate the effectiveness of endovenous treatment of symptomatic varicose veins using the endovenous laser (EVL) or radiofrequency (RF) energy over a >3-year follow-up. METHODS: From February 2002 to August 2005, 981 consecutive patients (770 women; mean age 51 years, range 15-90) with symptomatic varicose veins in 1250 lower limbs underwent endovenous ablation of 1149 great saphenous veins (GSV) and 101 small saphenous veins (SSV) under tumescent anesthesia without intravenous sedation or regional anesthesia. There were 990 GSV and 101 SSV procedures using EVL; 159 GSVs were treated with RF energy. An ultrasound evaluation was performed within 2 weeks of the procedure to evaluate occlusion of the vein, wall thickness, and clot extension into the deep venous system. Follow-up from the first 200 procedures in the series included clinical evaluation and duplex ultrasound scanning at 6 and 12 months and annually thereafter. RESULTS: Of the 1149 GSVs treated, 39 (3.4%) recanalizations were seen in 33 of the EVL and 6 of the RF procedures for inadequate treatment as judged by ultrasound. There were 9 (9.0%) failures among the 101 SSVs treated with EVL. Overall, both EVL and RF procedures were well tolerated, with only minor complications. One obese patient with ulcer developed pulmonary embolus on the fourth postoperative day. There were no differences between EVL and RF in efficacy or complications. Follow-up at a mean 3 years (range 30- 42 months) in 143 treated limbs showed no neovascularization in the groin. CONCLUSION: Outcomes with EVL and RF were good, with low complication rates that may be related to the use of local tumescent anesthesia without intravenous sedation.  相似文献   
999.
A male infant presented at birth with severe coarctation of the aorta and marginal left ventricular and mitral valve dimensions associated with a large secundum atrial septal defect. Following successful arch repair, the left ventricle remained small with preferential left‐to‐right atrial shunting and a dilated right ventricle. Clinically, the infant continued with tachypnea, poor feeding, and failure to thrive. At 4 months of age, the defect was closed with an Amplatzer Atrial Septal Occluder which resulted in immediate left ventricular cavity enlargement and clinical improvement.  相似文献   
1000.
Medications that act on the serotonergic system have been found to be of benefit in the treatment of alcohol-dependent individuals. In a randomized, placebo-controlled study, the efficacy of 6 weeks of ondansetron, a 5-HT3 antagonist (0.25 mg bid or 2.0 mg bid), in the treatment of 71 nonseverely alcohol-dependent males was tested. The results showed reduction of drinking differences were steadily increasing toward the end of the treatment period approached significance at week 7 in the 0.25 mg group ( p = 0.06). Twice as many patients in this group showed >2 standard deviations decrease in drinking compared with the other groups. When patients drinking >10 drinks/drinking day at baseline ( n = 11) were excluded from the analysis, significant group differences were found at both treatment and follow-up, with the lower ondansetron dose producing the greatest reduction from baseline (i.e., 2.8 standard drinks; –35% compared with baseline and –21% compared with placebo; p < 0.02–0.001). Within this group, there was an almost 4-fold greater number of patients showing a clinically meaningful decrease in drinking. Lower baseline drinking and higher level of education were significant and strong predictors of drinking reduction during treatment. Ondansetron was very well tolerated; hence, further long-term studies with 5-HT3 antagonists alone or in combination with other treatment components may offer promise for treatment of alcoholism.  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