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   7460篇
  免费   322篇
  国内免费   52篇
耳鼻咽喉   42篇
儿科学   186篇
妇产科学   29篇
基础医学   1263篇
口腔科学   93篇
临床医学   513篇
内科学   1545篇
皮肤病学   395篇
神经病学   719篇
特种医学   350篇
外科学   1003篇
综合类   31篇
一般理论   4篇
预防医学   302篇
眼科学   146篇
药学   598篇
中国医学   33篇
肿瘤学   582篇
  2022年   36篇
  2021年   50篇
  2020年   46篇
  2019年   76篇
  2018年   100篇
  2017年   81篇
  2016年   93篇
  2015年   130篇
  2014年   174篇
  2013年   244篇
  2012年   363篇
  2011年   387篇
  2010年   233篇
  2009年   261篇
  2008年   439篇
  2007年   532篇
  2006年   489篇
  2005年   497篇
  2004年   454篇
  2003年   487篇
  2002年   454篇
  2001年   95篇
  2000年   87篇
  1999年   129篇
  1998年   130篇
  1997年   127篇
  1996年   127篇
  1995年   81篇
  1994年   91篇
  1993年   83篇
  1992年   60篇
  1991年   48篇
  1990年   47篇
  1989年   37篇
  1988年   52篇
  1987年   42篇
  1986年   28篇
  1985年   26篇
  1984年   46篇
  1983年   38篇
  1982年   53篇
  1981年   37篇
  1980年   39篇
  1979年   32篇
  1978年   33篇
  1977年   29篇
  1976年   35篇
  1974年   32篇
  1973年   26篇
  1954年   28篇
排序方式: 共有7834条查询结果,搜索用时 15 毫秒
81.
PURPOSE: The purpose of this study was to evaluate the ability of rotated paddlewheel reformations for the detection of central and peripheral pulmonary embolism (PE) compared to standard axial multi detector CT (MDCT) images. MATERIAL AND METHODS: CT scans of 35 patients with PE were reviewed by three independent readers for the detection of pulmonary emboli using standard axial CT scans and reformatted paddlewheel technique. All images were evaluated in random order. MDCT examinations were performed with a collimation of 1.25 mm, a pitch of six and a reconstruction interval of 0.8mm. For each patient MIP were reformatted by using a paddlewheel arrangement with 5mm slab thickness and 5 degrees rotation. Standard of reference for PE was a consensus reading of the axial images by all three readers. RESULTS: The overall sensitivity for the axial images for the three readers ranged between 91% and 96%; for paddlewheel reformations from 78% to 83%; the specificity for both methods was 98-99%. Inter- and intraobserver agreement was also higher for axial images than for paddlewheel reformations. CONCLUSION: Comparing standard axial MDCT scans and reformatted paddlewheel images no significant difference for the detection of central PE was found, whereas for the detection of peripheral emboli standard axial images showed a significant higher percentage of detecting PE than paddlewheel reformations.  相似文献   
82.
Peptide-based probes for cancer imaging   总被引:1,自引:0,他引:1  
Receptors for regulatory peptides are overexpressed in a variety of human cancers. They represent the molecular basis for in vivo imaging with radiolabeled peptide probes. Somatostatin-derived tracers, designed to image the sst2-overexpressing neuroendocrine tumors, have enjoyed almost 2 decades of successful development and extensive clinical applications. More recent developments include second- and third-generation somatostatin analogs, with a broader receptor subtype profile or with antagonistic properties. Emerging tracers for other peptide receptors, including cholecystokinin/gastrin and GLP-1 analogs for neuroendocrine tumors, bombesin and neuropeptide-Y analogs for prostate or breast cancers, or Arg-Gly-Asp peptides for neoangiogenesis labeling, are also in current development. Application fields include both SPECT/CT and PET/CT.  相似文献   
83.
目的 研究正常胰腺、慢性胰腺炎与胰腺癌组织中软骨寡聚基质蛋白(cartilage oligomeric matrix protein,COMP)mRNA和蛋白表达水平的差异,揭示COMP在慢性胰腺炎样损伤中的意义。方法 采用Northern印迹法、Western印迹法、原位杂交法与免疫组化方法对14例慢性胰腺炎、14例胰腺癌及15例正常胰腺组织进行分析。结果 在慢性胰腺炎组织中和胰腺癌组织中类似慢性胰腺炎损伤的退变腺泡细胞胞浆内,存在高水平的COMP mRNA信号与免疫反应;而在胰腺癌细胞、正常胰腺组织的导管细胞与胰岛细胞的胞浆内,COMP mRNA信号与免疫反应微弱或缺如。结论 COMP在慢性胰腺炎及胰腺癌中类似慢性胰腺炎损伤的退变腺泡细胞内高表达,可能与慢性胰腺炎中腺泡细胞功能异常有关。  相似文献   
84.
Background: Auricular acupuncture at the relaxation point has been previously shown to be an effective treatment for anxiety in the preoperative setting. The purpose of this prospective, randomized, blinded study was to determine whether auricular acupressure can reduce stress and anxiety during ambulance transport.

Methods: Patients who required ambulance transport secondary to medical conditions were randomized to receive auricular acupressure at the relaxation point (n = 17) or at a sham point (n = 19). A visual analog scale was used to assess state anxiety as well as patient anticipation of hospital medical treatment (estimated waiting period for treatment, anticipated pain during treatment, attitude toward the physicians, and treatment outcomes). These variables were assessed at baseline and on arrival to the hospital.

Results: Patients in the relaxation group reported significantly less anxiety than patients in the sham group on arrival to the hospital (visual analog scale mean +/- SD: 37.6 +/- 20.6 to 12.4 +/- 7.8 mm vs. 42.5 +/- 29.9 to 46.7 +/- 25.9 mm, respectively;P = 0.002). Similarly, patient perception of pain during treatment (mean visual analog scale +/- SD: 32.7 +/- 27.7 to 14.5 +/- 8.1 mm vs. 17.2 +/- 26.1 to 28.8 +/- 21.9 mm, respectively;P = 0.006) and treatment outcomes of their illnesses (mean visual analog scale +/- SD: 46.7 +/- 29.4 to 19.1 +/- 10.4 mm vs. 35.0 +/- 25.7 to 31.5 +/- 20.5 mm, respectively;P = 0.014) were significantly more positive in the relaxation group than in the sham group. No differences were found in the other variables assessed.  相似文献   

85.
目的 了解P物质受体-神经激肽1受体(NK-1R)在正常肠管和溃疡性结肠炎组织中的表达,探讨该受体在溃疡性结肠炎的病理生理过程中所起的作用。方法 21个溃疡性结肠炎标本取自因该病并发症而手术的患。正常肠管组织取自24个器官捐献,应用逆转录聚合酶链反应(RT-PCR)技术检测正常肠管和溃疡性结肠炎组织NK-1R的信使核糖核酸(mRNA)水平,应用Western blot技术检测NK-1R的蛋白水平,应用免疫组织化学方法(免疫组化)进行NK-1R的组织学定位。结果 与正常肠管相比,溃疡性结肠炎组织中NK-1RmRNA和蛋白都过度表达,免疫组化检查显示,NK-1R的表达主要位于溃疡性结肠炎组织的肠黏膜表面,黏膜固有层的单核细胞,黏膜下层的动,静脉和纵形与环形肌层等处。结论 溃疡性结肠炎组织中NK-1R的表达水平明显上调,扰乱了神经激肽的作用环节,加剧肠管的病理改变。  相似文献   
86.
Background The value of re-exploration for pancreatic ductal adenocarcinoma after the initial diagnosis of unresectability is unclear. Methods In this study, we analyzed 33 patients who were re-explored after an initial diagnosis of unresectability. Results At the time of reoperation, a resectable tumor was found in 18 patients: therefore, 15 pancreaticoduodenectomies, two total pancreatectomies and one left resection were performed with three vascular resections. Morbidity and mortality rates for the cohort were 6/33 and 1/33, without significant differences between resectable and nonresectable patients. Length of stay, duration of operation, and blood loss were significantly increased in the resection group. Kaplan–Meier survival analysis demonstrated increased median survival for resected patients (1078 days after the initial operation versus 547 days in the group of unresectable patients; p = 0.018). Analysis of the reasons against initial resection showed that, if the patients had been sent to a tertiary referral center for pancreatic surgery, a different decision in favor of resection would probably have been made in 14 out of 33 patients. A review of 10 published reports on reoperation for pancreatic cancer revealed results comparable to our study in terms of low morbidity and mortality as well as a survival benefit. Conclusions Reoperation for pancreatic ductal adenocarcinoma that is initially deemed unresectable can be safely performed in a selected group of patients by experienced surgeons, supporting the concept of patient centralization in pancreatic surgery. Resection at the second operation may confer a survival benefit even when the initial findings preclude a potentially curative approach.  相似文献   
87.
Background One-half of breast cancer patients with positive sentinel lymph node (SN) have no further metastases in the axillary lymph node basin. The aim of the present study was to identify patients with positive SN who are unlikely to have further metastases in the axillary lymph node basin, using a new classification of SN, namely the S-classification. Methods Specimens of positive SN were subjected to a pathological review according to the previously published S-classification. S-stages of positive SN were correlated with the status of further metastases in the axillary lymph node basin after axillary lymph node dissection (ALND). Results Of 117 patients who underwent sentinel lymph node biopsy, 36 (30.8%) had a positive SN and were subjected to level I and II ALND. The occurrence of positive nonsentinel nodes was significantly related to the S-stage of SN. No patient with stage SI had additional metastases in the nonsentinel lymph nodes, while 14.3% of patients with SII stage disease and 60.9 % of patients with SIII disease had other non-SN that were metastatic. Conclusion S-stages of positive SN are highly predictive for axillary nonsentinel node status. Especially patients with SI sentinel node metastases appear to be at low risk for further nonsentinel node metastases.  相似文献   
88.
An eight-channel stimulation system, currently intended for stimulation of lower extremities, was developed and is introduced. The major development goals were easy handling, modularity to make the system easily adaptable for other functional electrical stimulation (FES) applications, and a wide stimulation parameter range for application-specific parameter optimization. For paraplegic stepping, the system worn by the patient consists of 2 four-channel stimulation modules, a central unit holding the battery and circuitry for power management and communication control, a wireless remote control unit, and a palmtop computer as the main control and input device. A software package for Microsoft Windows supports the design and optimization of stimulation sequences in the rehabilitation center. First tests with patients familiar with FES showed smoother movements during stepping and acceptable good handling. In combination with the PC software, the required stimulation sequences could be created in a very short time.  相似文献   
89.
Comparison of Celsior and UW solution in experimental pancreas preservation   总被引:10,自引:0,他引:10  
BACKGROUND: The University of Wisconsin solution (UW) is the gold standard for pancreas preservation. Celsior (CEL) was formulated specifically for heart preservation. Recently, experimental and clinical experience has been reported on the application of CEL to abdominal organs. In this animal study, pancreas preservation with CEL was compared with that in UW solution. PATIENTS AND MATERIALS: Heterotopic, allogeneic pancreaticoduodenal transplantation was performed in female G?ttingen Minipigs (n = 12 donors, n = 12 recipients). The grafts were flushed and stored for 6 h at 4 degrees C in UW or CEL. The recipients were randomized into two groups receiving either UW (n = 6)- or CEL (n = 6)-preserved grafts with a follow-up of 5 days. Blood flow (laser Doppler), partial oxygen tension, histological changes, endothelin-1 (plasma, immunohistochemistry), lipase, amylase, trypsinogen activation peptide, and C-reactive protein (CRP) were measured. RESULTS: Partial oxygen tension was lower in the CEL group (P < 0.05). However, blood flow did not differ between UW- and CEL-preserved organs. The histomorphologic analysis of the pancreatic grafts revealed significantly less edema in the UW-preserved organs. Serum levels of amylase, lipase, CRP, and TAP taken from the central venous blood were comparable in the two groups, except for higher amylase values 36 h after reperfusion in the CEL group compared to the UW group (P < 0.05). Likewise, TAP taken from the portal venous effluent of the graft was found to be higher in the CEL group than in UW (P < 0.05). Endothelin-1 serum levels rose significantly during reperfusion without differences between the two groups. ET-1 immunohistochemistry revealed increased local ET-1 during reperfusion in all grafts. However, the ET-1 immunostaining in the CEL group was more pronounced than that in the UW group (P < 0.05). CONCLUSIONS: Our results suggest that CEL solution is not as effective in preventing pancreatic ischemia/reperfusion damage as the standard UW solution in experimental pancreas transplantation. Increased ET-1 immunostaining and reduced p(ti)O(2) in the CEL group indicate increased microcirculatory damage in the CEL group.  相似文献   
90.
OBJECTIVE: Using the neural stem cell (NSC) clone C17.2, we evaluated the ability of transplanted murine NSCs to attenuate cognitive and neurological motor deficits after traumatic brain injury. METHODS: Nonimmunosuppressed C57BL/6 mice (n = 65) were anesthetized and subjected to lateral controlled cortical impact brain injury (n = 52) or surgery without injury (sham operation group, n = 13). At 3 days postinjury, all brain-injured animals were reanesthetized and randomized to receive stereotactic injection of NSCs or control cells (human embryonic kidney cells) into the cortex-hippocampus interface in either the ipsilateral or the contralateral hemisphere. One group of animals (n = 7) was killed at either 1 or 3 weeks postinjury to assess NSC survival in the acute posttraumatic period. Motor function was evaluated at weekly intervals for 12 weeks in the remaining animals, and cognitive (i.e., learning) deficits were assessed at 3 and 12 weeks after transplantation. RESULTS: Brain-injured animals that received either ipsilateral or contralateral NSC transplants showed significantly improved motor function in selected tests as compared with human embryonic kidney cell-transplanted animals during the 12-week observation period. Cognitive dysfunction was unaffected by transplantation at either 3 or 12 weeks postinjury. Histological analyses showed that NSCs survive for as long as 13 weeks after transplantation and were detected in the hippocampus and/or cortical areas adjacent to the injury cavity. At 13 weeks, the NSCs transplanted ipsilateral to the impact site expressed neuronal (NeuN) or astrocytic (glial fibrillary acidic protein) markers but not markers of oligodendrocytes (2'3'cyclic nucleotide 3'-phosphodiesterase), whereas the contralaterally transplanted NSCs expressed neuronal but not glial markers (double-labeled immunofluorescence and confocal microscopy). CONCLUSION: These data suggest that transplanted NSCs can survive in the traumatically injured brain, differentiate into neurons and/or glia, and attenuate motor dysfunction after traumatic brain injury.  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