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   3219篇
  免费   147篇
  国内免费   20篇
耳鼻咽喉   15篇
儿科学   63篇
妇产科学   18篇
基础医学   322篇
口腔科学   106篇
临床医学   281篇
内科学   897篇
皮肤病学   25篇
神经病学   363篇
特种医学   97篇
外科学   471篇
综合类   13篇
预防医学   117篇
眼科学   31篇
药学   335篇
中国医学   8篇
肿瘤学   224篇
  2022年   29篇
  2021年   48篇
  2020年   34篇
  2019年   26篇
  2018年   44篇
  2017年   33篇
  2016年   40篇
  2015年   43篇
  2014年   57篇
  2013年   76篇
  2012年   130篇
  2011年   181篇
  2010年   91篇
  2009年   77篇
  2008年   122篇
  2007年   130篇
  2006年   132篇
  2005年   136篇
  2004年   145篇
  2003年   170篇
  2002年   146篇
  2001年   123篇
  2000年   91篇
  1999年   102篇
  1998年   27篇
  1997年   25篇
  1996年   35篇
  1995年   30篇
  1993年   25篇
  1992年   80篇
  1991年   75篇
  1990年   98篇
  1989年   85篇
  1988年   78篇
  1987年   70篇
  1986年   75篇
  1985年   62篇
  1984年   37篇
  1983年   36篇
  1982年   23篇
  1979年   20篇
  1977年   22篇
  1973年   19篇
  1972年   19篇
  1971年   21篇
  1970年   26篇
  1969年   22篇
  1968年   22篇
  1967年   21篇
  1966年   19篇
排序方式: 共有3386条查询结果,搜索用时 15 毫秒
1.
This cross-sectional study was conducted to examine whether the obstructive sleep apnea syndrome (OSAS) is associated with elevation of the pulse wave velocity (PWV) and increase in the plasma levels of C-reactive protein (CRP), both of which are known markers of cardiovascular risk, and also to determine if the concurrent presence of the metabolic syndrome might exacerbate this elevation in the levels of these cardiovascular risk markers in subjects with OSAS. With these objectives, the PWV and serum CRP were measured in 184 subjects attending a sleep clinic. It was found that the PWV and CRP were higher in the subjects with OSAS (n=94) than in those without OSAS (n=90). Furthermore, among the subjects with OSAS, the PWV and CRP were higher in those with the concurrent presence of the metabolic syndrome (n= 41; PWV=1,562+/-19 cm/s; CRP=1.8+/-0.2 mg/l) than in those without metabolic syndrome (n=53; PWV=1,432+/-21 cm/s; CRP=1.2+/-0.1 mg/l) (p<0.05). A general linear model analysis demonstrated that OSAS and metabolic syndrome were independently associated with elevated PWV and increase of the plasma levels of CRP. OSAS appears to be associated with increased cardiovascular risk, as reflected by both elevated PWV and increase of the plasma CRP. The concurrent presence of metabolic syndrome may exacerbate this increase in cardiovascular risk in subjects with OSAS. Therefore, the concurrent presence of metabolic syndrome may constitute an additive cardiovascular risk factor in subjects with OSAS.  相似文献   
2.
1. The relationship between work-rate and the antihypertensive effect of exercise in hypertensives, and the mechanism of that effect, were investigated by a crossover clinical trial. 2. Ten mild hypertensives were randomly divided into two groups. One group performed low work-rate exercise (LWE) on a cycle ergometer for 10 weeks (blood lactate threshold; ~50% of maximum oxygen consumption [V?O2max]). After a 10 week interval without exercise training, these subjects were then switched to a high work-rate exercise (HWE) regimen (4 mmol/ L of blood lactate; ~75% of V?O2max) for another 10 weeks. In the other group, the order of exercise training was reversed. Since two patients withdrew from the protocol during HWE periods, statistical analysis was performed on the data from the remaining eight patients. There were no order effects observed in any of the data from the two groups. 3. During both LWE and HWE, resting blood pressure (BP) fell significantly after the initiation of exercise therapy (P<0.05). Furthermore, the overall effects of 10 weeks of LWE and HWE on BP were not significantly different. 4. The work-rate at the lactate threshold, which reflects physical fitness, had increased significantly by 16 W (P<0.01) after the LWE period and by 11 W (P<0.01) after the HWE. 5. During the LWE period, changes in haemodynamic and humoral variables were not significant, except for a reduction in plasma norepinephrine at week 10 (P<0.05). In the HWE period, changes in haemodynamic and humoral variables were not significant. 6. Based on these findings, LWE is recommended for mild hypertensives because of its safety.  相似文献   
3.
From 1976 to 1985, 277 cases of carcinoma of the esophagus were resected in the Second Department of Surgery, Tohoku University School of Medicine. Postoperative cardiocirculatory disturbances occurred in 114 cases (41.2%), arrhythmia being the disturbance most frequently observed (86.8%). Low cardiac output syndrome occurred in 8 cases and myocardial infarction occurred in 3 cases. The majority of the cases were treated successfully, but 5 patients died within one month after operation. Causes of death were as follows: myocardial infarction, constrictive pericarditis, cardiac tamponade, non-occlusive mesenteric ischemia and acute cardiac failure. Postoperative arrhythmia occurred mainly up to the third postoperative day. Low cardiac output syndrome occurred just after operation or on the first postoperative day. All cases of myocardial infarction occurred on the first postoperative day. The rate of occurrence of cardiocirculatory disturbances in aged patients (greater than or equal to 70) was significantly higher than other group (less than or equal to 69), (56.7%:38.1%, p less than 0.05). The rate of occurrence of cardiocirculatory disturbances in patients who had a history of hypertension or in patients with abnormal preoperative electrocardiographic findings were relatively higher than those in patients who had no history of hypertension or in patients with no abnormal preoperative electrocardiographic findings. The rate of occurrence of cardiocirculatory disturbances in patients who had undergone total resection of the thoracic esophagus was significantly higher than that in patients who had undergone partial resection of the thoracic esophagus (42.8%:23.8%, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
4.
A 13-year-old girl who had severe brain damage due to unknown prenatal cause presented rhabdomyolysis triggered by a mild viral infection. Her muscle biopsy revealed mild variation in fiber size and type 2 fiber atrophy without excess lipid storage. Biochemical analysis of the biopsied material showed decreased carnitine palmitoyltransferase (CPT) activity (15% of the control). Serum and urinary carnitine levels were normal. Skeletal muscle CT scanning showed multiple low density spots. The patient was diagnosed as having CPT deficiency. She recovered from rhabdomyolysis without renal failure after a month with conservative therapy. CPT deficiency is usually found in young healthy persons. This is the first case report of CPT deficiency which presented severe psychomotor retardation since neonatal period.  相似文献   
5.
Human tumor–infiltrating lymphocytes (TILs) derived from pleural or ascitic fluid were incubated with recombinant interleukin 2 and transfected with human tumor necrosis factor (TNF) a gene by the lipofection procedure. The resulting TILs secreted significant amounts of TNF in the culture supernatant and exhibited cytotoxicity against established cell lines, such as K562 and Daudi, and autologous tumor cells. The TNF gene–transfected TILs exhibited an augmented killing of autologous tumor cells.  相似文献   
6.
7.
Non-progressive juvenile spinal muscular atrophy of the distal upper limb (Hirayama's disease) occurs predominantly in men in the second decade with unilateral weakness of the fingers and hand, and atrophy of the hand and forearm. The symptoms generally progress for 3-4 years after onset and then stop. Since the second decade is a very important period starting one's career, early stopping of the progression and possibly the improvement are essential. On the bases of the neuroradiological studies, a forward displacement of the posterior wall of the dural canal at the lower cervical level on neck flexion is presumed to be the main pathogenetic mechanism in this disease. On neck flexion, the spinal cord is compressed anteroposteriorly at C7 and C8 segmental levels. Pathological studies suggested that chronic microcirculatory disturbances in the spinal cord as the result of repeated flexion of the neck might produce necrosis of the anterior horns. We used a cervical collar for the prevention of neck flexion in 14 patients in the early stage and compared the results with those of 18 patients who had natural courses. In the therapy group, muscle weakness of the affected hand improved in 5 patients and the progression of the disease was stopped in 8 patients with the duration of 1.8 +/- 1.2 years, whereas the duration of progression of the natural course group was 2.9 +/- 1.6 years. Only one patient who could not tolerate the use of collar showed a slight progression. These results suggest that the cervical collar is a useful therapeutic tool in this disease.  相似文献   
8.
OBJECTIVES: Graft failure has been reported when the arterial conduit, such as the internal thoracic artery (ITA) or the right gastroepiploic artery (GEA), is grafted to a lower grade coronary artery stenosis. The shear stress as a significant factor affecting graft patency was compared between the arterial conduit and the saphenous vein graft (SVG) after surgery. METHODS: In 101 patients, 40 ITAs, 27 GEAs and 34 SVGs were examined using a Doppler-tipped guide wire during postoperative angiography. The graft flow volume and shear stress were calculated from velocity and diameter data. The study grafts were classified according to the grade of native coronary artery stenosis: group L had more than 50 up to 75% stenosis, and group H had more than 75% stenosis. Group H consisted of 25 ITAs, 17 GEAs and 21 SVGs, while group L consisted of 15 ITAs, 10 GEAs and 13 SVGs. RESULTS: In group H, graft flow volume did not significantly differ among the ITA (34+/-11 ml/min), GEA (36+/-16 ml/min) and SVG (41+/-15 ml/min), and graft shear stress significantly (ITA vs. GEA P<0.0001; GEA vs. SVG P<0.01) differed among the ITA (16.0+/-4.8dyn/cm(2)), GEA (9.1+/-3.2dyn/cm(2)) and SVG (4.8+/-1.6dyn/cm(2)). In group L, flow volume was lower (P<0.001) in the ITA (18+/-6 ml/min) and GEA (13+/-8 ml/min) than in the SVG (35+/-16 ml/min), and shear stress was significantly (P<0.001) greater in the ITA (13.7+/-4.9dyn/cm(2)) than the GEA (5.6+/-2.0dyn/cm(2)) or SVG (4.6+/-2.0dyn/cm(2)). CONCLUSIONS: These data suggest that shear stress of the ITA is superior and maintained despite the flow volume being reduced by flow competition. Lower shear stress of the GEA for intermediate stenosis may be associated with the development of conduit failure.  相似文献   
9.
10.
The nonimprovement group was characterized by the following: ① a high incidence of diabetes (4 of 6 patients) ,② a high incidence of preexisting cardiac dysfunction documented prior to or at the time of induction of  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