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   2707篇
  免费   70篇
  国内免费   22篇
耳鼻咽喉   169篇
儿科学   104篇
妇产科学   115篇
基础医学   172篇
口腔科学   62篇
临床医学   217篇
内科学   649篇
皮肤病学   30篇
神经病学   173篇
特种医学   166篇
外科学   622篇
综合类   23篇
预防医学   58篇
眼科学   81篇
药学   98篇
中国医学   3篇
肿瘤学   57篇
  2023年   13篇
  2022年   23篇
  2021年   47篇
  2020年   33篇
  2019年   46篇
  2018年   58篇
  2017年   56篇
  2016年   74篇
  2015年   77篇
  2014年   118篇
  2013年   154篇
  2012年   215篇
  2011年   181篇
  2010年   127篇
  2009年   126篇
  2008年   203篇
  2007年   226篇
  2006年   222篇
  2005年   239篇
  2004年   191篇
  2003年   142篇
  2002年   102篇
  2001年   23篇
  2000年   24篇
  1999年   5篇
  1998年   12篇
  1997年   15篇
  1996年   11篇
  1995年   5篇
  1994年   8篇
  1993年   7篇
  1992年   3篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
  1988年   2篇
  1987年   2篇
  1985年   3篇
  1983年   1篇
排序方式: 共有2799条查询结果,搜索用时 31 毫秒
21.
OBJECTIVE: We hypothesized that the use of N-acetylcysteine would ameliorate the lung reperfusion injury observed after deep hypothermia and total circulatory arrest (DHTSA). METHODS: Experiments were carried out on 12 adult mongrel dogs of either sex weighing 25 to 30 kg. The animals were randomly divided into two groups of six animals each. All animals were cooled to an esophageal temperature of 15 degrees C during 30 minutes and underwent 60 minutes of DHTSA, followed by the reinstitution of cardiopulmonary bypass (CPB) and rewarming. Before rewarming, while 100 mL physiologic saline solution was added into the pump in group I, 50 mg/kg N-acetylcysteine(NAC) was given in group II. Heart rate, mean arterial pressure, pulmonary arterial pressure, left atrial pressure, central venous pressure, and cardiac output were recorded. To measure lung tissue malondialdehyde (MDA), water content and polymorphonuclear leukocytes (PMNs) count, lung tissue samples were taken before CPB and after weaning CPB. In addition, alveolar-arterial oxygen difference (AaDO(2))()for tissue oxygenation was calculated by obtaining arterial blood gas samples. Dynamic lung compliance (DLC) was measured before CPB and after CPB. RESULTS: MDA levels before CPB of 44.2 +/- 3.9 nmol/g tissue rose to 76.6 +/- 5.6 nmol/g tissue after weaning CPB in group I (p = 0.004). In group II also, the MDA levels increased from 43.5 +/- 4.2 to 57.4 +/- 5.6 nmol MDA/g tissue after weaning CPB (p = 0.006). The MDA increase in group II after CPB was found to be significantly lower than in group I (p = 0.006). The wet-to-dry lung weight ratio in the NAC group was 5.1 +/- 0.2, significantly less than in the control group (5.9 +/- 0.3), (p = 0.004). AaDO(2) significantly increased in the group I and II (p = 0.002 and p = 0.002, respectively); this elevation in group I was significant than in group II (p = 0.044). In histopathological examination, it was observed that neutrophil counts in the lung parenchyma rose significantly after CPB in both groups (p < 0.001). The increase in group I was significantly larger than group II (p < 0.001). CONCLUSIONS: Results represented in our study indicate that addition of NAC into the pump after DHTSA can reduce lung reperfusion injury.  相似文献   
22.
23.
Does sodium nitroprusside reduce lung injury under cardiopulmonary bypass?   总被引:4,自引:0,他引:4  
Objective: We hypothesized that direct pulmonary arterial infusion of sodium nitroprusside (SNP) would ameliorate lung injury under cardiopulmonary bypass. Methods: Experiments were performed on 12 adult mongrel dogs of both sexes weighing 20–28 kg. The animals were randomly divided into two groups of six animals each. All animals were subjected to total cardiopulmonary bypass (CPB) and moderate hypothermia (28°C core temperature). During total CPB, the aorta was clamped together with the pulmonary artery to prevent any antegrade flow to the lungs. After cardioplegic arrest for 120 min, the animals were rewarmed, weaned from CPB, and their condition stabilized for another 90 min. After the release of the aortic cross-clamp, the dogs received either a 5% glucose solution as a placebo (group I) or SNP (0.5 μg/kg per min) (group II), both infused into the pulmonary arterial line. The infusion was stopped after 60 min. To measure lung tissue malondialdehyde (MDA), water content and polymorphonuclear leukocytes count, lung tissue samples were taken before CPB and after weaning from CPB. In addition, alveolar-arterial oxygen difference (AaDO2) for tissue oxygenation was calculated by obtaining arterial blood gas samples. Results: Values of MDA before CPB of 42.0±5.3 nmol/g of tissue rose to 67.6±5.7 nmol/g of tissue after weaning from CPB in group I (P=0.028). In group II MDA values also increased from 43.1±4.3 to 52.4±5.7 nmol MDA/g of tissue after weaning from CPB (P=0.046). The MDA increase in group II after CPB was found to be significantly lower than that for group I (P=0.004). The wet-to-dry lung weight ratio in the sodium nitroprusside group was 5.1±0.2, significantly lower than in the control group (6.8±0.4), (P=0.01). AaDO2 increased significantly in group I (P=0.028). There was no statistically significant difference (P=0.065) between groups I and II. During histopathological examination it was observed that neutrophil counts in the lung parenchyma rose significantly after CPB in both groups. The increase in group I was significantly larger than that in group II (P<0.001). Conclusions: The results represented in our study indicate that pulmonary arterial infusion of sodium nitroprusside during reperfusion can reduce lung injury under cardiopulmonary bypass.  相似文献   
24.
OBJECTIVE: Hypertrophic nonunions can be managed successfully with distraction. Hypertrophic changes indicate that the tissue at the nonunion site has a biologic healing potential. The missing component is an appropriate mechanical environment to transform a hypertrophic nonunion into solid bone. DESIGN: At our institution, the records of 10 male and 6 female patients treated for stiff hypertrophic nonunion with the Ilizarov distraction method were retrospectively analyzed. The average age of the patients was 42.3 years (range 15-69 years). The nonunion time ranged from 8-48 months. All patients had at least 1 cm shortening, 3 patients had a deformity in one plane, and 13 had a deformity in two planes. The pathology was localized to the upper extremity in 5 patients, to the lower extremity in 11 patients, with a periarticular localization in 11 patients. An Ilizarov-type circular external fixator was applied in all patients to correct shortening, to correct deformity, and to achieve a solid union. RESULTS: All nonunions healed at an average follow-up of 38.1 months (range 24-95 months). The average time spent in the external fixator was 7.1 months (range 5-10 months). The average preoperative length discrepancy was 2.25 cm (range 1-8 cm), which was eliminated in all patients at the time of frame removal. The average coronal plane angulation of 19.7 degrees (range 15-37 degrees) and sagittal plane angulation of 20.8 degrees (range 5-45 degrees), together with translation in one patient, also were corrected to normal anatomic alignment. Complications included minor pin tract infections and hardware problems; recurrence of deformity was observed in one patient who refused to wear a protective brace after frame removal. CONCLUSIONS: Hypertrophic nonunions can be managed successfully with distraction. The Ilizarov device can address every aspect of a stiff hypertrophic nonunion, including shortening and deformity.  相似文献   
25.
We describe a 45-yr-old woman with an intermediate type atrioventricular septal defect associated with a double-orifice left atrioventricular valve (DOLAV). We diagnosed this exceptional anomaly by intraoperative transesophageal echocardiography (TEE) during surgery that was scheduled for only a primum type atrial septal defect (ASD) repair. Preoperative transthoracic echocardiography and angiography revealed the ASD but could not demonstrate the DOLAV. We were able to repair this rare and challenging abnormality successfully under the guidance of TEE imaging during the operation. TEE provides valuable information about both anatomy and functional aspect of the valvular structures. Besides its proven role in cardiac surgery, intraoperative use of TEE also serves as a useful tool for diagnosis of such unexpected and potentially missed abnormalities.  相似文献   
26.
OBJECTIVES: Ischaemia/reperfusion injury of the liver is the major cause of liver dysfunction and cellular death in transplantation and in liver resection with hepatic pedicle clamping. Many agents are used to prevent this phenomenon, which occurs following interaction of different mediators during both ischaemia and reperfusion. In this study, we aimed to assess the effects of allopurinol, a xanthine oxidase inhibitor, and pentoxifilline, on liver ischaemia/reperfusion injury when used together and to compare these with the effects of using these agents singly. METHODS: Thirty-two rats were divided into four groups consisting of eight rats: Group C, control; Group P, pentoxifilline; Group A, allopurinol; and Group PA, pentoxifilline + allopurinol. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) levels were measured before hepatic pedicle clamping, on the 45th minute of ischaemia and 15 and 45 minutes after reperfusion. Group P rats were injected with 50 mg/kg pentoxifilline, Group A rats 50 mg/kg allopurinol and Group PA rats were injected with both agents 15 minutes before hepatic pedicle clamping. RESULTS: Ischaemia/reperfusion injury was produced by hepatic pedicle clamping, as demonstrated by AST, ALT and LDH increase. Injury prevention occurred in Groups P, A and PA. No significantly different (better) prevention was provided by giving allopurinol plus pentoxifilline to the rats. Furthermore, no difference was observed between the allopurinol and pentoxifilline injected groups in terms of preventing ischaemia/reperfusion injury. CONCLUSIONS: Pretreatment with allopurinol or pentoxifilline resulted in significantly lower hepatic enzyme elevation than that in controls in the rat liver ischaemia/reperfusion model. Using both agents does not provide better protection than using either agent alone.  相似文献   
27.

Purpose

Toll-like receptors (TLRs) have an important role in the activation of both innate and adaptive immunity in response to pathogens and endogenous danger signals from damaged or dying cells. The aim of this study was to determine the relationship between urothelial carcinoma (UC) and TLR expression.

Basic procedures

Real-time polymerase chain reaction evaluation was made of the messenger RNA expression of TLRs 1–10 in 24 UC samples and 46 nontumoral bladder tissue samples. The levels of proinflammatory cytokines (IL-1β, IL-6, and IL-8) in the urine samples were also determined with enzyme-linked immunosorbent assay.

Main findings

TLR2–7 and TLR10 expressions were significantly higher in UC than in the control group (P<0.05 for all comparisons). No concordance was found between matched tumor tissue and urine samples in terms of TLR expression. IL-1β, IL-6, and IL-8 levels were significantly higher in urine specimens of patients with UC (P = 0.033, P = 0.001, and P = 0.008, respectively).

Principal conclusions

The results of this study demonstrated that the TLR gene expression profiles reflect the heterogeneity within UC. These results might also prompt further investigation to better understand the role of the TLR gene family expression in the tumor progression of UC.  相似文献   
28.
BACKGROUND: Underlying hepatic injury and cirrhosis are leading factors that interfere with the post-operative liver regeneration and function. Hyperbaric oxygenation (HBO) has been reported to ameliorate the ischemia-reperfusion injury of the liver, to induce compensatory hypertrophy of the predicted remnant liver in rats after portal vein ligation and to augment liver regeneration after hepatectomy in non-cirrhotic rats. Our aim was to determine the effect of HBO treatment on liver regeneration after partial hepatectomy in normal and cirrhotic mice in this experimental study. MATERIALS AND METHODS: The effect of HBO on liver regeneration was studied in a mice model combining carbon tetrachloride induced cirrhosis and partial hepatectomy. Mice were divided into four groups: Control, cirrhotic, non-cirrhotic HBO-treated, and cirrhotic HBO-treated. All animals underwent 40% hepatectomy. Liver regeneration was evaluated by the proliferating cell nuclear antigen-labeling index. Serum aspartate aminotransferase and alanine aminotransferase levels were measured to evaluate liver injury. RESULTS: Serum alanine aminotransferase and aspartate aminotransferase levels were significantly decreased in HBO-treated cirrhotic group compared to cirrhosis group after hepatectomy (P = 0.001 and P = 0.014, respectively). The proliferating cell nuclear antigen labeling index was significantly higher in HBO treated cirrhotic group than in cirrhotic group after hepatectomy (P = 0.022). CONCLUSIONS: Our results suggest that HBO treatment improves liver functions and augments hepatocyte regeneration in cirrhotic mice after hepatectomy. Post-operative HBO treatment may have a beneficial effect on post-operative liver function and regeneration in cirrhotic patients.  相似文献   
29.
ObjectiveThe aim of this study was to evaluate the impact of two different home-based daily exercise programs on pulmonary functions in the patients with ankylosing spondylitis (AS).MethodsFifty-one patients with AS were distributed into three groups. Group 1 (n = 19) was given a conventional exercise regimen. Group 2 (n = 19) received exercises based on the Global Posture Reeducation (GPR) method. Group 3 (n = 13) was accepted as the control group. Patients were assessed according to pain, functional capacity (The Bath Ankylosing Spondylitis Functional Index – BASFI), disease activity (The Bath Ankylosing Spondylitis Disease Activity Index – BASDAI), chest expansion, pulmonary function parameters, and 6-min walk distance (6MWD) test.ResultsAlthough there were significant improvements for BASDAI and BASFI scores in all groups, significant improvements in the VAS pain, chest expansion, pulmonary function parameters and 6MWD test were observed in the exercise groups. The improvements in pain, functional capacity, disease activity, chest expansion, pulmonary function parameters and 6MWD test were better in the exercise groups than in the control group. The GPR method resulted in greater improvements than the conventional exercise program in specific pulmonary function parameters like forced vital capacity, forced expiratory volume in 1 s, and peak expiratory flow parameters.ConclusionBoth exercises are efficient in improving pulmonary functions. Since the improvements in pulmonary function tests were greater in the patients who performed the exercise according to GPR method, motivated patients should be encouraged to perform this exercise program.  相似文献   
30.
Nephrotoxicity is a major complication of acetaminophen (APAP), a widely used analgesic and antipyretic drug, and there is no specific treatment for APAP-induced renal damage. It has been reported that reactive oxygen metabolites or free radicals are important mediators of APAP toxicity. In this study, the protective role of melatonin (MLT) on APAP-induced nephrotoxicity was investigated in rats. For this purpose, nephrotoxicity was induced in male Wistar albino rats by intraperitoneal (i.p.) administration of a single dose of 1,000 mg/kg APAP. Some of these rats also received i.p. melatonin (10 mg/kg) 20 min after administration of APAP. The rats were sacrificed 24 h after administration of APAP. Urea and creatinine levels were measured in the blood, and levels of malondialdehyde (MDA) and glutathione (GSH), and glutathione peroxidase (GSH-Px), catalase (CAT), and superoxide dismutase (SOD) activity were determined in renal tissue. Serum urea and creatinine levels increased significantly as a result of APAP nephrotoxicity. A significant increase in MDA and decreases in GSH level and GSH-Px, CAT, and SOD activity indicated that APAP-induced renal damage was mediated through oxidative stress. Significant beneficial changes were noted in serum and tissue oxidative stress indicators in rats treated with MLT. These biochemical observations were supplemented by histopathological examination of kidney sections, which revealed that MLT also reduced the severity of APAP-induced histological alterations in the kidney. These results indicate that administration of APAP causes oxidative stress to renal tissue and that MLT protects against the oxidative damage associated with APAP.  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