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   25338篇
  免费   1198篇
  国内免费   139篇
耳鼻咽喉   174篇
儿科学   384篇
妇产科学   200篇
基础医学   3223篇
口腔科学   667篇
临床医学   1790篇
内科学   6557篇
皮肤病学   361篇
神经病学   1735篇
特种医学   893篇
外科学   4837篇
综合类   96篇
预防医学   620篇
眼科学   393篇
药学   1565篇
中国医学   61篇
肿瘤学   3119篇
  2023年   140篇
  2022年   308篇
  2021年   516篇
  2020年   275篇
  2019年   386篇
  2018年   466篇
  2017年   385篇
  2016年   484篇
  2015年   455篇
  2014年   620篇
  2013年   746篇
  2012年   1242篇
  2011年   1294篇
  2010年   792篇
  2009年   648篇
  2008年   1256篇
  2007年   1300篇
  2006年   1322篇
  2005年   1370篇
  2004年   1312篇
  2003年   1244篇
  2002年   1300篇
  2001年   715篇
  2000年   732篇
  1999年   679篇
  1998年   399篇
  1997年   301篇
  1996年   244篇
  1995年   234篇
  1994年   205篇
  1993年   216篇
  1992年   573篇
  1991年   546篇
  1990年   485篇
  1989年   469篇
  1988年   389篇
  1987年   356篇
  1986年   319篇
  1985年   273篇
  1984年   192篇
  1983年   175篇
  1982年   75篇
  1979年   143篇
  1978年   106篇
  1977年   90篇
  1974年   89篇
  1973年   78篇
  1972年   85篇
  1971年   76篇
  1969年   68篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We investigated the detection of non-specific reactions in the measurement of plasma (1-->3)-beta-D-glucan (beta-glucan) and countermeasures against them using alkaline treatment, chromogenic automated kinetic assay (alkaline-kinetic assay). In this study, we reexamined the values of beta-glucan using the alkaline-kinetic assay with and without laminaran oligosaccharides (LO) as a kind of beta-glucan that blocks the Limulus reaction. The materials for this study were 584 plasma samples in which beta-glucan had been measured. These were taken from 232 patients in Kawasaki Medical School Hospital between January 2002 and March 2002. Non-specific reactions were judged by a calculated value under a LO additive condition. Determination as to whether or not the each time course of the Limulus reaction was influenced by a non-specific reaction was also studied by applying a non-specific reaction index set up independently. Non-specific reactions were recognized in 51.9% of the samples (81/156). The amount of non-specific reaction was 9.9 pg/ml or less in major samples. On the other hand, when the cut off value of the index for detection of non-specific reactions was set at 0.5, the sensitivity was 88.9% and specificity was 73.7%. The positive and negative predictive values were 93.5% and 60.9% respectively. Non-specific reactions can be approximately distinguished by applying the non-specific reaction index. By so doing, unnecessary initiation of anti fugal therapy in response to non-specific reactions can be avoided. Further prospective and radical studies of non-specific reactions in the alkaline-kinetic assay are necessary.  相似文献   
992.

Background

Published results for carotid endarterectomy (CEA) in symptomatic and asymptomatic severe carotid stenosis with diabetes mellitus (DM) are contradictory. To evaluate perioperative and long-term results of CEA in patients with DM, we retrospectively analyzed data of patients with or without DM who underwent CEA in our institute.

Methods

Between January 2005 and December 2010, 281 consecutive CEAs were performed in 268 patients under general anesthesia. All patients were subject to cardiac work-ups before surgery, and coronary revascularization was performed prior to CEA if patients were diagnosed with significant coronary artery stenosis. Lesion characteristics were assessed by a duplex ultrasound scan, computed tomography angiography (CTA), and plaque imaging on magnetic resonance imaging (MRI) before surgery, and patients were followed-up by a duplex ultrasound scan at three, six, and 12 months, then yearly, after surgery.

Results

Of 281 cases, 136 had DM (48 %). Diabetic patients more frequently had a history of coronary artery disease than non-diabetic patients (48.5 % vs. 36.6 %, P?=?0.042). Coronary intervention prior to CEA was more frequently performed in diabetic patients than in non-diabetic patients (22.1 % vs. 11.0 %, P?=?0.013). The incidence of perioperative (30 day) stroke (P?=?1.000), death (P?=?1.000), and cardiac complications (P?=?0.484) did not differ among groups. Follow-up was available in 77.2 % of patients, with a median duration of 50 months (interquartile range, 32.1-67.2 months). The incidence of ipsilateral stroke (P?=?0.720), death (P?=?0.351), and severe restenosis (peak systolic velocity?>?230 cm/sec) (P?=?0.905) were not different between groups.

Conclusions

DM does not increase the risk of perioperative complications and does not influence long-term outcomes after CEA if preexisting vascular risk factors and cardiac diseases are appropriately evaluated and treated before surgery.  相似文献   
993.

Objective

Carotid artery stenting (CAS) is a well-accepted treatment for atherosclerotic stenosis of carotid arteries. Since the occurrence of distal embolization with CAS is still a major concern embolus protection devices (EPD) are usually employed during the procedure. We examined two types of embolus protection filters (Angioguard XP (AG); Filterwire EZ (FW)) and evaluated the function. Thus, the filter was examined postoperatively and the cause of intraoperative flow impairment was evaluated.

Materials and methods

CAS was performed for 54 patients with carotid artery stenosis (55 lesions: 25 AG; 27 FW; 3 others). After completing CAS the filter membrane was stained with hematoxylin-eosin (HE) solution and removed from the filter strut. Once mounted on a glass slide the filter was evaluated under a microscope. The area occupied with debris was measured and the relationship to intraoperative flow impairment was evaluated. Furthermore, the relationship between perioperative ischemic complications and intraoperative flow impairment was statistically analyzed.

Results

Microscopic observation of the slide revealed the pore density of the FW was 1.5 times higher than that of the AG and the filter area of the FW was 2.5 times wider than than the AG. HE staining facilitated characterization of the debris composition. The area occupied with debris was significantly more in the AG (0.241?±0.13 cm2) than in the FW (0.129?±0.093 cm2). Thus, fibrin was significantly more precipitated in the AG. Flow impairment occurred in 6 AG cases (24.0 %) and 4 FW cases (14.8 %). It was induced by filter obstruction in the AG and by vasospasms in the FW. Three cases treated with AG (12.0 %) were complicated with cerebral infarction and all of them were related to flow impairment. One FW case (3.7 %) was complicated with cerebral infarction in presence of preserved flow throughout the intervention.

Conclusion

Filter function is different according to each design. The cause of flow impairment was attributable to filter obstruction in the AG group and to vasospasms in the FW group. Filter obstruction tends to result in cerebral infarction.  相似文献   
994.

Background

The current commonly used cardiac ischemic preconditioning (IPC) protocol, involving three 5-min cycles of ischemia–reperfusion (I/R), may not be clinically beneficial because of its acutely deleterious effects on hemodynamics. This study attempted to assess the effects of a novel stepwise IPC scheme on cardiac function, infarct size, and arrhythmogenesis in a rabbit model of prolonged I/R.

Methods

Anesthetized open-chest rabbits were subjected to 60-min occlusion of a proximal branch of the left coronary artery followed by 180-min reperfusion. Animals were divided into five groups (n = 6 each): (1) control group (no IPC); (2) 2-min IPC group (three cycles of 2-min IPC); (3) 5-min IPC group (three cycles of 5-min IPC); (4) 10-min IPC group (three cycles of 10-min IPC); and (5) stepwise IPC group (2-, 5-, and 10-min I/R).

Results

Compared with control group, 2-, 5-, and 10-min IPC decreased arrhythmia score by 16%, 67%, and 33%, respectively. Remarkably, stepwise IPC resulted in a 78% reduction of arrhythmias. Stepwise IPC also produced the least ventricular infarct size when compared with 2-, 5-, and 10-min IPC groups (16.4% versus 39.3%, 28.1%, and 38.5%, P < 0.05).

Conclusions

These results suggest that stepwise IPC has better cardioprotective effects against prolonged I/R injury and may serve as an acceptable approach to clinical revascularization procedures on the heart, including catheter-based and surgical approaches.  相似文献   
995.
Granular cell tumor may be located anywhere in the body; however, the gastrointestinal tract is infrequently involved and anal granular cell tumors are extremely rare. We report herein a rare case of granular cell tumor in the anal region. In the current case, a 66-year-old Japanese woman was found to have a polypoid lesion in the anus with hemorrhoids. The mass detected as an anal polypoid lesion with ulceration was resected and diagnosed as granular cell tumor by histologic examination. Granular cell tumor of the anal region is rare, and benign perianal polypoid lesions are relatively uncommon clinical findings. They might present diagnostic challenges to surgeons and pathologists. Awareness of the differential diagnosis of granular cell tumor and careful microscopic examination might allow proper management and diagnosis.Key words: Granular cell tumor, Anal, Polypoid massGranular cell tumor is a relatively rare neoplasm that is firmly identified as a neural lesion due to its close association with nerves and its immunohistochemical characteristics.15 Granular cell tumors may be located anywhere in the body; however, the gastrointestinal tract is infrequently involved and anal granular cell tumors are extremely rare.38 We report herein a rare case of granular cell tumor in the anal region. The concern with anal tumor is differential diagnosis, since benign mesenchymal anal tumors are relatively rare.7,8 Thus, an anal polypoid lesion might present diagnostic challenges to surgeons and pathologists.  相似文献   
996.
The prognosis of esophageal cancer with distant metastasis is dismal. We report a 70-year-old man with esophageal cancer and multiple lung and lymph node metastases. Complete response was achieved following definitive chemoradiotherapy. Twenty-four months after the initial chemoradiotherapy, local recurrence was detected but there was no evidence of distant metastasis. Therefore, the patient underwent salvage esophagectomy. The surgery was well tolerated without any postoperative complications. The patient is still alive 48 months after the salvage surgery. Our experience suggests that salvage esophagectomy is an important component of multimodal therapy for the recurrence of esophageal cancer.Key words: Esophageal cancer, Chemoradiotherapy, Salvage surgeryThe prognosis of esophageal cancer has improved in recent years, but remains poor despite curative resection.1 The prognosis is extremely dismal in patients with distant metastasis. The Radiation Therapy Oncology Group (RTOG) trial 85-01 showed that chemoradiotherapy (CRT) improved outcomes, with a 5-year overall survival rate of 26% compared with 0% following radiotherapy alone. Moreover, residual cancer was less common following CRT (26%) than following radiotherapy alone (37%).2 However, local recurrence occurs in 37% of patients after definitive CRT.3 Salvage esophagectomy is one strategy for residual cancer or local recurrence after definitive CRT. Of note, when R0 resection is achieved, long-term survival can be expected.46 On the other hand, this is an invasive procedure associated with high morbidity and mortality6 and the patient''s prognosis is extremely poor after R1/R2 resection.46 Therefore, salvage esophagectomy should only be performed if complete removal of the tumor is expected.Here, we report a rare case with esophageal cancer and multiple lung metastases, in which complete response (CR) was achieved after definitive CRT and salvage esophagectomy was effective for the local recurrence.  相似文献   
997.
998.
Purinergic signaling via ATP and adenosine produced by astrocytes is one pathway underlying neuron–glia interactions in the central nervous system (CNS). In production of purines, extracellular metabolism of released purines via ecto-enzymes is important. The expression and activities of these enzymes are altered under pathological conditions. Production of fibroblast growth factor 2 (FGF2) is increased under pathological conditions, and this has various effects on astrocytes. Here, we investigated the effects of FGF2 on purine metabolism in cultured rat spinal cord astrocytes. Astrocytes rapidly metabolized purines added to the extracellular solution. FGF2 increased extracellular metabolism of AMP to adenosine and of adenosine to inosine by upregulating ecto-5′-nucleotidase and adenosine deaminase (ADA), respectively. ADA activity and protein were detected both in the cytosol and external solution of astrocytes, and their levels were markedly increased by FGF2. FGF2 also increased metabolism of endogenously released ATP, resulting in a transient increase in adenosine and substantial accumulation of extracellular inosine. Moreover, FGF2 increased ATP release by upregulating the activity of gap junction hemichannels. These data show that FGF2 regulates purine production in astrocytes and suggest that extracellular ADA released by astrocytes plays an important role in extracellular purine metabolism in the CNS.  相似文献   
999.

Purpose

Carbon dioxide (CO2) insufflation reduces abdominal pain and discomfort after endoscopic procedures; however, there is no previous study focusing the safety of CO2 insufflation for patients with obstructive ventilatory disturbance. Here, we investigated the safety of CO2 insufflation during colorectal endoscopic submucosal dissection (ESD) for patients with obstructive disturbance.

Methods

Between January 2010 and January 2013, colorectal ESD was performed using CO2 insufflation for 385 consecutive patients. End-tidal CO2 (EtCO2) and transcutaneous oxygen saturation (SpO2) were consecutively measured from the time before insertion of the colonoscope to the end of ESD. Patients were monitored by two nurses during the procedure and controlled for clinical symptoms of hypercapnia such as apnea or a depressed level of consciousness. According to their respiratory function, patients were stratified into a normal group and an obstructive disturbance group. We retrospectively compared EtCO2 and SpO2 during the procedures and the incidence of symptoms related to CO2 retention between the two groups.

Results

The obstructive disturbance group consisted of 77 patients. There were similar changes of EtCO2 in the obstructive disturbance group and normal group and no significant rise in EtCO2. The maximum EtCO2 level in any patient was <60 mmHg. In the obstructive disturbance group, there were no symptoms associated with CO2 retention. There were no significant differences in the median SpO2 between both groups and no prolonged drop of SpO2.

Conclusions

CO2 insufflation during colorectal ESD is safe for patients with obstructive ventilatory disturbance.  相似文献   
1000.
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