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   11241篇
  免费   486篇
  国内免费   77篇
耳鼻咽喉   258篇
儿科学   480篇
妇产科学   385篇
基础医学   1009篇
口腔科学   406篇
临床医学   926篇
内科学   2629篇
皮肤病学   185篇
神经病学   679篇
特种医学   503篇
外科学   2253篇
综合类   253篇
一般理论   3篇
预防医学   451篇
眼科学   245篇
药学   618篇
中国医学   36篇
肿瘤学   485篇
  2024年   7篇
  2023年   107篇
  2022年   230篇
  2021年   390篇
  2020年   202篇
  2019年   274篇
  2018年   322篇
  2017年   236篇
  2016年   366篇
  2015年   423篇
  2014年   528篇
  2013年   609篇
  2012年   774篇
  2011年   779篇
  2010年   467篇
  2009年   409篇
  2008年   768篇
  2007年   868篇
  2006年   849篇
  2005年   779篇
  2004年   663篇
  2003年   538篇
  2002年   476篇
  2001年   86篇
  2000年   79篇
  1999年   66篇
  1998年   60篇
  1997年   41篇
  1996年   51篇
  1995年   29篇
  1994年   21篇
  1993年   22篇
  1992年   23篇
  1991年   20篇
  1990年   24篇
  1989年   31篇
  1988年   20篇
  1987年   19篇
  1986年   18篇
  1985年   18篇
  1984年   8篇
  1983年   11篇
  1982年   6篇
  1980年   6篇
  1979年   7篇
  1978年   8篇
  1974年   5篇
  1973年   9篇
  1972年   7篇
  1971年   8篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Radiolabelled somatostatin analogues are of potential value in the imaging of somatostatin receptor-positive tumours. Recently, somatostatin receptors have been demonstrated in the osteoblast precursor cells. In this preliminary study, we evaluated the uptake characteristics of indium-111 octreotide in two benign and two malignant bone tumours. Tracer accumulation was observed in all four cases, and overall lesion to background ratio (mean±SD) was 2.74±0.84 and 2.98±1.49 at 4 h and 24 h, respectively. There was no clear relationship between I111In-octreotide accumulation and the benign or malignant nature of the tumour. In one patient, tracer uptake was inhibited by unlabelled octreotide administration. These results suggest that111In-octreotide can be taken up by benign and malignant bone tumours. The inhibition of tumour uptake by treatment with cold octreotide supports the concept that specific uptake mechanisms are responsible for111In-octreotide deposition by bone tumours.  相似文献   
82.
Protective effect of quercetin on renal ischemia/reperfusion injury in rats   总被引:5,自引:0,他引:5  
BACKGROUND: There is increasing evidence to suggest that toxic oxygen radicals play a role in the pathogenesis of ischemia/reperfusion (I/R) injury in the kidney. The aim of this study was to evaluate whether quercetin, an oxygen free radical scavenger, protects kidney tissue. METHODS: A renal I/R injury was induced by a left renal pedicle occlusion by ischemia for 45 min, followed by 60 mins of reperfusion with contralateral nephrectomy in rats. The rats were pretreated intraperitoneally with a quercetin suspension (50 mg/kg) 60 min before the ischemia induction. Thiobarbituric acid reactive substances (TBARS), protein carbonyl content, tumor necrosis factor alpha (TNF-alpha), reduced glutathione (GSH) levels, myeloperoxidase (MPO) catalase (CAT) and superoxide dismutase (SOD) activities were determined in renal tissue. RESULTS: There were 3 groups of rats, the control group, the I/R group and the I/R+Q group. Our results indicate that TBARS, TNF-alpha levels, MPO activity and protein carbonyl content were significantly higher in the I/R group than those in the control group (p<0.05, p<0.01, p<0.01 and p<0.01, respectively). Quercetin administration significantly decreased these parameters (p<0.05, p<0.01, p<0.05 and p<0.01, respectively). GSH levels, SOD, and CAT activities significantly decreased after I/R injury when compared to the control group (p<0.01, p<0.05 and p<0.01, respectively). Quercetin treatment significantly increased GSH levels and activities of these enzymes when compared to the I/R group (p<0.05, p<0.01, p<0.05, respectively). CONCLUSIONS: These results suggest that quercetin reduces renal oxidative injury and facilitates repair. Quercetin can have a role in a renoprotective therapeutic regimen.  相似文献   
83.
OBJECTIVE: Bone metastasis is a major cause of morbidity in prostatic cancer. Therefore, detecting and monitoring bone lesions are crucial for treatment of prostatic carcinoma. We aimed to evaluate total body bone mineral density and regional bone mineral density in patients with prostate cancer with and without metastases, and to compare them with bone scintigraphy. METHODS: Fifty-four patients with prostatic carcinoma and 20 healthy subjects were investigated with bone scintigraphy and dual-energy X-ray absorptiometry. The bone scintigraphic findings were classified as normal (score 0: n = 22), abnormal but not typical for metastases (score 1: n = 18), and typical pattern of metastases (score 2: n = 14). RESULTS: The patients with bone metastases prostate cancer had significantly higher total bone mineral density and regional bone mineral density of trunk and pelvis than healthy controls and prostate cancer patients without bone metastases. There was a significant positive correlation between bone scan score and total bone mineral density and regional bone mineral density of trunk and pelvis (r = 0.328, P < 0.05, r = 0.60, P < 0.001, r = 0.480, P < 0.001, respectively). CONCLUSION: Our results show that patients of prostate cancer with bone metastases have increased bone mineral density (BMD) in the pelvis and trunk, possibly because of a predominance of osteoblastic over osteolytic metastases demonstrated by Tc-99m MDP bone scan.  相似文献   
84.
Background Pneumoperitoneum causes intracranial pressure elevation and blood stasis at lower extremities. This study investigates cerebral oxygen saturation changes during laparoscopy and the effects of intermittent sequential compression (ISC) of the lower extremities in patients during elective laparoscopic cholecystectomy. Patients and method Sixty patients were randomly divided into two groups according to the application of ISC to the lower extremities. Group I served as control group whereas ISC was applied to group II. Cerebral oxygen saturation, peripheral blood oxygen saturation, heart rate, mean blood pressure, and associated changes have been recorded during the operation. Results Peripheral blood oxygen saturation and mean blood pressure values did not change significantly after pneumoperitoneum. Cerebral oxygen saturation levels of the group II patients were higher in than the group I patients and the difference between the groups was statistically significant (p = 0.0001). The difference became more prominent following the 35th minute of the operation. Mean heart rate of the patients in group II was lower than the patients in group I and the difference was also statistically significant (p = 0.0001). Conclusion In this study, it was found that the decrease in cerebral oxygen saturation was recovered with ISC application. This simple and reliable technique helps to restore cerebral oxygen saturation levels while increasing blood return from the lower extremities.  相似文献   
85.
Background: Postoperative vomiting (POV) is a common complication after tonsillectomy. Dexamethasone is known to decrease postsurgical vomiting. In this study, we compared the effects of dexamethasone alone to dexamethasone plus propofol on postoperative vomiting in children undergoing tonsillectomy. Methods: In a randomized double‐blinded study, we evaluated 80 healthy children, aged 4–12 years, who underwent tonsillectomy with or without adenoidectomy. After anesthesia was induced by inhalation of sevoflurane, 0.15 mg·kg?1 dexamethasone and 2 μg·kg?1 fentanyl was administered i.v. to all patients. The patients in the dexamethasone plus propofol group received 1 mg·kg?1 propofol before intubation and continuously after intubation at a rate of 20 μg·kg?1·min?1 until the surgery was completed. Data for postoperative vomiting were grouped into the following time periods: 0–4 and 4–24 h. Data were analyzed using a Student’s t‐test and chi‐squared analysis. Results: The percentage of patients exhibiting a complete response (defined as no retching or vomiting for 24 h) increased from 37.5% in the dexamethasone‐alone group to 75% in the dexamethasone plus propofol group (P = 0.001). Twenty‐two patients (55%) in the dexamethasone‐alone and nine patients (22.5%) in the dexamethasone plus propofol groups experienced vomited during 0–4 h (P = 0.003). Eight patients in the dexamethasone‐alone group and three patients in the dexamethasone plus propofol group received ondansetron as a rescue antiemetic during the postoperative period. Conclusion: For children undergoing tonsillectomy, intraoperative subhypnotic propofol infusion combined with dexamethasone treatment provides a better prophylaxis against postoperative vomiting than does dexamethasone alone.  相似文献   
86.

Purpose

This study aimed to determine the effect of melatonin in preventing ischemia-reperfusion (I-R) injury-induced tissue damage and on spermatogenesis after experimental testicular torsion (TT).

Methods

Forty peripubertal rats were divided into 4 groups each containing 10 rats: control (C), sham (S), torsion plus detorsion (TD), and torsion plus melatonin (M). The left testes were rotated 720° for 6 hours and detorsed for 6 hours thereafter. Serum inhibin B (IB) levels were measured in blood samples taken from all groups. Left orchiectomies were performed to determine the tissue levels of Johnsen's scores (JS) and malondialdehyde (MDA).

Results

Serum IB levels in the S and TD groups were significantly lower compared with that in the C group, whereas they were higher in the M group compared with the TD group. The MDA levels were significantly lower in the C, S, and, M groups compared with the TD group. Johnsen's scores were significantly higher in the C, S, and M groups compared with the TD group.

Conclusions

Our results suggested that melatonin is a potent antioxidant agent in preventing testicular I-R injury, as shown by increased IB levels and JS.  相似文献   
87.
Spontaneous rupture of the Achilles tendons in hemodialysis patients is a rare complication. The majority of these patients have additional predisposing factors, such as previous use of fluoroquinolone antibiotics or corticosteroids. Spontaneous rupture of bilateral Achilles tendons without any of those predisposing factors is exceptional. In this paper, we report a 43-year-old woman who had been undergoing regular hemodialysis for 16 years. She developed bilateral spontaneous and simultaneous rupture of the Achilles tendons. She also developed pathological fracture of right femur neck 3 years later. Based on previous cases of tendon ruptures in uremic patients and the lack of history for the use of corticosteroids or fluoroquinolones, we believe that secondary hyperparathyroidism is the predisposing factor in this patient.  相似文献   
88.
We present the results of prospective evaluation of digital compared to plain radiographic preoperative templating for primary total knee replacement. All consecutive patients undergoing primary knee replacement were eligible. Patients with previous knee replacement or without calibrated digital or plain radiographs were excluded. Plain radiographs were templated against acetate templates. Digital images were templated with the help of commercial software TraumaCad. A 25-mm spherical metal ball placed nearest to the affected knee joint acted as calibration object. The ICC value for intra-rater reliability was 0.846 for tibial templating and 0.840 for femoral templating. PFC sigma cruciate substituting components were implanted in all patients. Twenty-eight consecutive patients between April 2006 and June 2007 were included. Accurate digital templating score was 80% for tibial implant and 40% for femur. Accuracy of analog templating was 55% for tibial implant and 50% for femur. There was no mismatch of over one size. The differences between templated and implanted sizes were plotted against their mean in Bland–Altman plot. The 95% confidence interval of the differences between digital and actual sizes were: 0.78 to −0.75 sizes for tibial implant and 1.15 to −0.93 sizes for femoral implant. The 95% confidence interval of the differences between plain and actual sizes were: 0.38 to −0.99 size for tibial implant and 0.93 to −1.32 size for femoral implant. The two tailed P value for difference between digital and analog templating from a Wilcoxon matched pair signed rank test was 0.021 for tibia and 0.006 for femur. We found preoperative templating by the operating surgeon reliable and accurate but digital templating did not offer any additional advantage.  相似文献   
89.
Aim  In recent years significant progress has been made in identifying and quantitating physico-chemical processes involved in urinary stone formation. The ability of urine to inhibit calcium oxalate crystallization is an important mechanism against stone formation. Dietary factors appear to affect the ability of urine to inhibit calcium oxalate crystallization. These factors encouraged us to study the effects of lemon and orange juices on calcium oxalate crystallization in vitro. Material and methods  The nucleation and aggregation of calcium oxalate monohydrate crystals were studied using turbidimetric 30-min time course measurements of optic density at 620 nm after mixing solutions containing calcium chloride and sodium oxalate at 37°C, pH 5.7. The formation of crystals is induced by the addition of the oxalate and calcium solution. The effects on calcium oxalate crystal growth of trisodium citrate, lemon and orange juices were examined. The effects of lemon and orange juices were evaluated by the addition of 50 ml of juices. The optical density is measured at physiological conditions. The maximum increase of optic density with time, termed SN, reflects maximum rate of formation of new particles. After an equilibrium has been reached, a progressive decrease of optic density with time is observed. Rate of aggregation, SA, is derived from the maximum decrease in optic density. Results  Among the modifiers studied, citrate decreased both SN and SA (P < 0.001). Lemon juice was also found to inhibit the rate of crystal nucleation and aggregation. But orange juice did not have any effect on the calcium oxalate crystallization (P > 0.05). Conclusion  These results show that effective prevention of urinary stone formation should aim at restoring the urine’s ability to inhibit calcium oxalate crystallization and more emphasis should be given to dietary measures.  相似文献   
90.
An inguinal and perianal localization of Fournier's gangrene (FG) in a 15-month-old boy as a complication of the varicella infection is discussed. This is the first presentation of the disease as a complication of the varicella rashes. There were already 57 pediatric FG cases resulting from other causes that had been presented in the medical literature.  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