首页 | 官方网站   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   1018篇
  免费   63篇
  国内免费   6篇
医药卫生   1087篇
  2021年   24篇
  2020年   12篇
  2019年   17篇
  2018年   18篇
  2017年   18篇
  2016年   21篇
  2015年   21篇
  2014年   27篇
  2013年   31篇
  2012年   53篇
  2011年   47篇
  2010年   21篇
  2009年   28篇
  2008年   45篇
  2007年   47篇
  2006年   55篇
  2005年   41篇
  2004年   60篇
  2003年   75篇
  2002年   55篇
  2001年   14篇
  2000年   19篇
  1999年   14篇
  1998年   14篇
  1997年   11篇
  1996年   8篇
  1995年   11篇
  1994年   14篇
  1993年   13篇
  1992年   16篇
  1991年   15篇
  1990年   19篇
  1989年   21篇
  1988年   13篇
  1987年   14篇
  1986年   13篇
  1985年   20篇
  1984年   13篇
  1983年   10篇
  1982年   6篇
  1980年   7篇
  1979年   7篇
  1978年   6篇
  1974年   5篇
  1973年   7篇
  1972年   6篇
  1971年   7篇
  1969年   6篇
  1967年   6篇
  1966年   5篇
排序方式: 共有1087条查询结果,搜索用时 15 毫秒
1.
Sixteen cohorts of men aged 40–59 years at entry were examined with the measurement of some risk factors and then followed-up for mortality and causes of death for 25 years. These cohorts were located in the USA (1 cohort), Finland (2), the Netherlands (1), Italy (3), the former Yugoslavia (5), Greece (2), and Japan (2), and included a total of 12,763 subjects.Large differences in age-adjusted coronary heart disease (CHD) death rates were found, with extremes of 45 per 1000 in 25 years in Tanushimaru, Japan, to 288 per 1000 in 25 years in East Finland. In general, higher rates were found in the US and Northern European cohorts as compared to the Southern European and Japanese cohorts. However, during the last 10 years of follow-up large increases of CHD death rates were found in some Yugoslavian areas. Out of 5 measured entry characteristics treated as age-adjusted levels (serum cholesterol, systolic blood pressure, cigarette smoking, body mass index and physical activity at work), only serum cholesterol was significant in explaining cohort differences in CHD death rates.Over 50% of the variance in CHD death rates in 25 years was accounted for by the difference in mean serum cholesterol. This association tended to decline with increasing length of follow-up, but this was due to the great changes in mean serum cholesterol in the two Jugoslavian cohorts of Velika Krsna and Zrenjanin. When these two cohorts were excluded the association increased with time.Changes in mean serum cholesterol between year 0 and 10 helped in explaining differences in CHD death rates from year 10 onward.It can be concluded that this study suggests that mean serum cholesterol is the major risk factor in explaining cross-cultural differences in CHD.  相似文献   
2.
Retrograde administration of cardioplegic solution via the right atrium with continuous cooling of the right ventricular cavity (right atrial perfusion cooling) was assessed for its protective effect in 12 dogs with occlusion of the right coronary artery subjected to global ischemia for 60 minutes. After an initial administration of 4 degrees C crystalloid cardioplegic solution by antegrade aortic perfusion, myocardial protection was established either by right atrial perfusion cooling (group I; n = 6) or by antegrade aortic perfusion alone (group II; n = 6). The right ventricular temperature was approximately 15 degrees C in group I and 20 degrees C in group II. After ischemia for 60 minutes, the adenosine triphosphate content of the right ventricular free wall was significantly higher in group I than in group II (24.4 +/- 1.45 versus 13.8 +/- 2.34 mumol/gm dry weight, p less than 0.05). The percent recovery of right ventricular contractility, which was evaluated by end-systolic pressure-volume relationships, was significantly better in group I at each reperfusion period (30 minutes: 130.0% +/- 9.6% versus 86.1% +/- 11.8%, p less than 0.05; 60 minutes: 159.6% +/- 12.9% versus 96.5% +/- 20.1%, p less than 0.05). Postischemic right ventricular stiffness (reciprocal value of compliance) increased in group II compared with group I, although the difference was not statistically significant. There were no major differences in percent recovery of the left ventricular end-systolic pressure-volume relationships between the two groups. The evidence suggests that the right atrial perfusion cooling method produces excellent right ventricular protection.  相似文献   
3.
As a design for a biodegradable functional polymer, compositionally homogeneous poly[(sodium acrylate)-co-(vinyl alcohol)] [P(SA-co-VA)], containing varying amounts of vinyl alcohol groups as biodegradable segments were prepared and their biodegradability and builder performance in detergent formulations were analyzed with respect to the successive vinyl alcohol length. It was found that the acrylate copolymers having more than 80 mol-% vinyl alcohol content showed biodegradability. That is, P(SA-co-VA) having a vinyl alcohol chain length of more than about 5–6 is cleaved by PVA-degrading microbes. This indicates that the vinyl alcohol blocks, which act as biodegradable segments, should be incorporated into the polymer chain in such a manner that they are accepted as substrates by the PVA-degrading enzymes.  相似文献   
4.
The left ventricular assist device (LVAD) is usually used in patients with end-stage heart failure as a bridge to transplantation. Recently, some studies have reported functional recovery with the use of an LVAD, although the mechanisms responsible for recovery are not fully understood. We investigated the functional recovery of the infarcted, failing rat heart in response to mechanical unloading after heterotopic transplantation. Heart failure was induced in Lewis rats by ligating the left anterior descending artery. After 4 weeks, the infarcted hearts were harvested and heterotopically transplanted. The transplanted infarcted heart was removed after 2 weeks of unloading and examined for hypertrophy and fibrosis, as well as for mRNA levels encoding for brain natriuretic peptide, sarco(endo)plasmic reticulum Ca(2+)-ATPase2a (SERCA2a), and beta1- and beta2-adrenergic receptors. Normal and infarcted rats without transplantation served as control animals. The infarcted heart was hypertrophied as evidenced by an increase in heart weight and myocyte diameter. After unloading the infarcted heart for 2 weeks, there was a decrease in heart weight and myocyte diameter. However, the percentage of myocardial fibrosis increased after unloading. The mRNA expression of brain natriuretic peptide and the beta2-adrenergic receptor significantly improved after mechanical unloading. The levels of SERCA2a mRNA tended to increase after unloading. In conclusion, unloading the failing, infarcted heart can help normalize left ventricular hypertrophy and cardiac gene expression. This unloading model appears to partially mimic the conditions of hemodynamic support with an LVAD in heart failure patients and potentially offers insights into the mechanisms of functional recovery.  相似文献   
5.
The incidence of peripheral arteriosclerosis is on the increase in chronic hemodialysis patients. Recently, the intervention (IV) treatment is conducted to deal with this problem. IV was performed in 4 dialysis patients against the complication of arteriosclerosis obliterans (ASO) but the result was unsuccessful in 3 of them. These 3 failure cases were investigated to find the problems associated with percutaneous transluminal angioplasty (PTA). Cases 1, 2 and 3 had intermittent claudication while case 4 had gangrenous toes as the major complaint. The symptoms in these cases were attributable to 90-100% stenosis and occlusion of superficial femoral artery, bilateral iliac arteries, bilateral superficial femoral-popliteal artery, branch of right iliac artery and left iliac artery region, respectively. IV was successful in case 1 but failed in cases 2 and 4 because the catheter itself did not go through due to the severe stenosis of vessel or the procedure of forcefully dilating the vessel caused dispersion of minute thrombi. In case 3, acute myocardial infarction occurred at 10 h after successful IV, resulting in sudden death. In view of the extent of invasion, IV is a treatment method selected against ASO in dialysis patients. However, the method has a high risk of causing thrombus formation, vessel rupture and organ failure. In this regard, it is advisable to evaluate the systemic condition and conduct IV if the extent of stenosis is mild.  相似文献   
6.
The immunoreactivity of albumin (ALB) was observed in the hepatocytes of fetal rats on day 18 of gestation, and was especially observable in immature rough endoplasmic reticulum (rER) and Golgi apparatus (GA); by then, a small amount of silver grains of ALB mRNA could already be detected. Just after birth, immunoreactivity of ALB could be observed in fine granules or diffusely in all hepatocytes, and was present in rER and GA. One week after birth immunoreactivity of ALB was observed in all hepatocytes and was visible in developed rER and GA; the grains of ALB mRNA were present in all hepatocytes.  相似文献   
7.
Among cases that had multiple renal arteries on one side, an inferior supernumerary renal artery was found in 24/270 cases (ca. 9%) on the right and in 19/270 cases (ca. 7%) on the left, together with the usual renal artery. We have noticed that there are correlations between their levels of origin from the aorta and their positional relation to the ureter and the inferior vena cava (IVC). An inferior supernumerary renal artery (InfRA) of lower origin passes in front of the IVC and behind the ureter. An InfRA of middle origin passes in front of both the IVC and the ureter. An InfRA of upper origin passes behind the IVC and in front of the ureter or renal pelvis. In addition there was a tendency for the lower origin type to have an ureteric branch, while the middle and upper origin types had a gonadal branch. These findings suggest that different derivations lead to the inferior supernumerary renal arteries.  相似文献   
8.
9.
BackgroundPortal vein embolization before liver resection is considered the therapy of choice for patients with inadequate future liver remnants. The concept of radioembolization with Yttrium-90 to achieve the same goal has limited data.MethodsWe retrospectively compared patients who underwent portal vein embolization and Yttrium-90 lobectomy before resection of hepatocellular carcinoma in patients with chronic liver disease.ResultsSeventy-three patients underwent portal vein embolization and 22 patients underwent Yttrium-90. Forty-seven percent of patients before portal vein embolization required additional procedures for tumor control, and 27% of patients after Yttrium-90 required additional procedure to mainly induce further hypertrophy. Both therapies achieved the goal of future liver remnants >40%, but the degree of hypertrophy was significantly higher in Yttrium-90 patients (63% for Yttrium-90, 36% for portal vein embolization, P < .01). Tumor response was significantly better with Yttrium-90, achieving complete response in 50% of patients. Resectability rate was higher after portal vein embolization (85% for portal vein embolization, 64% for Yttrium-90, P = .03). Tumor progression was the most common reason precluding surgery. Complete tumor control was the reason not to pursue surgery in 18% of patients after Yttrium-90.ConclusionBoth preoperative portal vein embolization and Yttrium-90, increases liver resectability rates by inducing hypertrophy of future liver remnants in patients with hepatocellular carcinoma and chronic liver disease. Yttrium-90 lobectomy achieved better tumor control and provided more time to assess therapy response, optimizing the indication for surgery.  相似文献   
10.
Clinical and Experimental Nephrology - Arteriovenous fistula (AVF) is the most preferred vascular access for hemodialysis patients, and early failure of AVF is one of the most avoidable...  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-23

京公网安备 11010802026262号