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   820篇
  免费   38篇
  国内免费   2篇
耳鼻咽喉   8篇
儿科学   6篇
妇产科学   3篇
基础医学   65篇
口腔科学   40篇
临床医学   49篇
内科学   199篇
神经病学   135篇
特种医学   17篇
外科学   211篇
综合类   3篇
预防医学   7篇
眼科学   3篇
药学   79篇
肿瘤学   35篇
  2023年   9篇
  2022年   10篇
  2021年   31篇
  2020年   13篇
  2019年   23篇
  2018年   17篇
  2017年   16篇
  2016年   18篇
  2015年   16篇
  2014年   17篇
  2013年   26篇
  2012年   43篇
  2011年   72篇
  2010年   37篇
  2009年   36篇
  2008年   60篇
  2007年   59篇
  2006年   63篇
  2005年   70篇
  2004年   50篇
  2003年   43篇
  2002年   38篇
  2001年   10篇
  2000年   5篇
  1999年   11篇
  1998年   8篇
  1997年   12篇
  1996年   6篇
  1995年   3篇
  1994年   5篇
  1993年   4篇
  1992年   2篇
  1991年   4篇
  1990年   1篇
  1989年   2篇
  1988年   1篇
  1987年   2篇
  1986年   1篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1982年   2篇
  1981年   3篇
  1980年   1篇
  1978年   2篇
  1975年   1篇
  1968年   1篇
  1963年   1篇
  1962年   1篇
排序方式: 共有860条查询结果,搜索用时 390 毫秒
91.
92.
Oestrogen producing adrenocortical tumours are extremely rare. We report a 65-year-old woman who presented with abnormal vaginal bleeding, with no significant abnormalities in her uterus or ovaries, who was found to have a right adrenal mass by radiological examination. Excessive secretion of oestrogens from the tumour was demonstrated by adrenal venous sampling. Basal levels of corticosteroids were within normal limits. Adrenalectomy was performed and pathological examination revealed an adrenocortical adenoma measuring 5.5 cm in its greatest dimension, in which both clear and compact tumour cells were observed. Oestrogen levels normalized following the removal of the adrenal mass. Tissue concentrations of oestrone and oestradiol in the tumour were 6.9 (69.5 pmol/g wet tissue weight) and 34.6 (93.6 pmol/g wet tissue weight)-fold greater respectively than those of adjacent non-neoplastic adrenal cortex. Aromatase activity in the tumour tissue determined by the 3H-water method was 118.6 pmol/h/mg protein, equivalent to that of a full-term human placenta. Immunohistochemical analysis of aromatase demonstrated immunoreactivity in the tumour cells, especially in compact cells, but not in adjacent non-neoplastic adrenal cells. This is the first reported case of an oestrogen producing adrenocortical adenoma in which aromatase in the tumour cells was documented.  相似文献   
93.
Effects of the bilateral electrolytic lesioning of the basal forebrain (BF), including the ventral globus pallidus, on passive or active avoidance tasks, were studied in male Wistar rats. A severe deficit in acquisition of passive avoidance response was produced by the lesioning in the posterior level of BF. The retention of the passive avoidance response was markedly disrupted with post-training lesioning. Time-dependent but only slight recovery from the memory impairments was observed in the passive avoidance task given 4,8 or 16 weeks after BF lesions. The acquisition of active avoidance response using a two-way shuttle ☐ was also disturbed by BF lesioning. Retention of active avoidance response was clearly impaired by post-training lesions of the BF. The BF lesioned rats gradually acquired the passive avoidance performance when trained repeatedly at 24- or 48-h intervals, by giving a foot shock in case of avoidance failure. Extinction of the acquired passive avoidance response rapidly occurred in the BF lesioned rats. Furthermore, neurotoxic lesions of BF with kainic acid produced a significant impairment in acquisition of passive avoidance response.These results suggest that bilateral BF lesions impair the acquisition and retention of passive or active avoidance response, and that these impaired rats may be useful as an experimental model for Alzheimer's disease and senile dementia.  相似文献   
94.
We have conducted aortic valve replacement (AVR) using a stentless bioprosthesis (Medtronic Freestyle valve) on 10 patients with calcified aortic stenosis since March 2004. There were 64-84 years of age and 75 ± 5.5 years old on average, and included 4 males. Implantation was conducted by a modified subcoronary method in all the patients. The preoperative New York Heart Association class was class II in 80% of the patients. The preoperative left ventricular mass and the left ventricular mass index (LVMI) were 193.1-524.1 g and 144.1-299.5 g/m2 and, on average 328.4 ± 104.7 g and 217.3 ± 55.7 g/m2, respectively. The annulus dimension was 18-24 mm and, on average, 20.3 ± 1.7 mm. The size of implanted valve was 19-25 mm and, on average, 21 ± 2.2 mm. The maximum pressure gradient of the aortic valve remained at 14.2-46.5 mmHg, 25.2 ± 10.2 mmHg on average, 1 or 2 months after surgery, but the LVMI significantly improved to 153.2 ± 33.9 g/m2 (p = 0.018). The hospitalization period were 24.7 ± 16.9 days for all the patients and 19.3 ± 5.1 days for patients undergoing the AVR alone. These results show that LVMI is significantly reduced by using a stentless bioprosthesis in the early phase after surgery, and early discharge from hospital can be expected by concurrently using minimally invasive cardiac surgery.  相似文献   
95.
A 67-year-old man underwent laparoscopic surgery for rectal cancer in the lithotomy position. After surgery he complained of bilateral lower limb pain, swollen legs, and sensory disturbance. The serum creatine kinase value was 46 662 U/l. Venography demonstrated compression from outside without any obstruction. The T2 image of magnetic resonance imaging (MRI) showed a massive swollen muscle and a partial high-intensity area in the bilateral lower limbs. The posterior compartment pressures of lower legs were high (gastrocnemius muscle: 30 mmHg [right] and 44 mmHg [left]). Compartment syndrome (superficial posterior compartment) was thus diagnosed. He underwent a fasciotomy using the single dorsal approach and the administration of a large amount of fluid. He recovered well without any motor or sensory deficits. Compartment syndrome is rare, occurring only once in every 3500 cases, but it is a severe complication of surgery in the lithotomy position. Several risk factors have been pointed out: including prolonged operation, hardness of the operating table, obesity, dehydration, and hypothermia. To prevent compartment syndrome, appropriate positioning during surgery is therefore essential. To make a timely diagnosis and identify the precise location of muscle edema, the T2 image of MRI is useful.  相似文献   
96.
Vascular endothelial growth factor (VEGF) is an important survival factor for endothelial cells in hypoxic environments. High glucose regulates certain aspects of VEGF expression in various cell types, including proximal tubular cells. Thus, ambient glucose levels may modulate the progression of chronic kidney disease, especially diabetic nephropathy. Immortalized rat proximal tubular cells (IRPTC) were cultured for 24 h under hypoxic conditions (1% O(2)), with or without high d-glucose (25 mM), or with or without high l-glucose (25 mM). Controls included culture in normoxic conditions and normal d-glucose (5.5 mM). VEGF mRNA expression was assessed by real-time quantitative PCR, and VEGF protein in the supernatant was assessed by ELISA. Hypoxia increased VEGF expression. This response was significantly blunted by high d-glucose (1.98 +/- 0.11- versus 2.65 +/- 0.27-fold increase for VEGF mRNA expression, 252.8 +/- 14.7 versus 324.0 +/- 11.5 pg/10(5) cells for VEGF protein; P < 0.05 both) but not by high l-glucose. It is interesting that hydrogen peroxide also blunted this response, whereas alpha-tocopherol restored the VEGF response to hypoxia in the presence of high d-glucose. For determination of involvement of the hypoxia-inducible factor (HIF)/hypoxia-responsible element (HRE) pathway, IRPTC that were stably transfected with HRE-luciferase were cultured under the previous conditions. High d-glucose also reduced luciferase activity under hypoxia, whereas alpha-tocopherol restored activity. In vivo experiments using streptozotocin-induced diabetic rats confirmed that hyperglycemia blunted HIF-HRE pathway activation. Insulin treatment restored activation of the HIF-HRE pathway in streptozotocin-induced diabetic rats. In conclusion, high glucose blunts VEGF response to hypoxia in IRPTC. This effect is mediated by the oxidative stress-regulated HIF-HRE pathway.  相似文献   
97.
98.
Abstract: The speed of recognition of Japanese Kana (phonetic) and Kanji (ideographic) symbols tachistoscopically presented either to the left or the right visual field in 20 normal right-handed Japanese subjects (10 males and 10 females) was investigated. A significant right visual field superiority for the recognition of both meaningful and nonsense Kana words was obtained, while there was a lack of laterality differences in recognition of meaningful Kanji words. The results indicated that Kanji processing is somewhat different from Kana processing. Sex did not influence visual field preferences regardless of the kind of verbal stimuli.  相似文献   
99.
A regional lymphatic system is composed of the first, second, third and even fourth or much more intercalated nodes along the lymptatic route from the periphery to the venous angle or the thoracic duct. The third or fourth node is usually termed the last-intercalated node or end node along the route. Similarly, one of the supraclavicular nodes is known to correspond to the end node along the thoracic duct. It is generally called 'Virchow's node', in which the famous 'Virchow's metastasis' of advanced gastric cancer occurs. The histology of this node has not been investigated, although region-specific differences in histology are evident in human lymph nodes. We found macroscopically the end node in five of 30 donated cadavers. Serial sections were prepared for these five nodes and sections stained with hematoxylin and eosin. Histological investigation revealed that, on the inferior or distal side of the end node, the thoracic duct divided into three to 10 collateral ducts and these ducts surrounded the node. The node communicated with the thoracic duct and its collaterals at multiple sites in two to three hilus-like portions, as well as along the subcapsular sinus. Thus, the end node was aligned parallel to the thoracic duct. Moreover, the superficial and deep cortex areas of the end node were fragmented to make an island-like arrangement, which may cause the short-cut intranodal shunt. Consequenly, the filtration function of most of Virchow's node seemed to be quite limited.  相似文献   
100.
Shear bond strengths of indirect resin composites to hybrid ceramic   总被引:1,自引:0,他引:1  
A hybrid ceramic, Estenia, is a highly-filled composite for indrect use. The purpose of this study was to measure the shear bond strength between Estenia and six incremental materials: Estenia, Cesead II, Epricord, Gradia, Prossimo, and Solidex. Five specimens were prepared for each group, and all specimens were subjected to shear bond strength testing at a cross-head speed of 1 mm/min. Data were analyzed using two-way ANOVA and Dunnett's T3 test at 95% confidence level. The results indicated that the shear bond strength of Estenia to Estenia was significantly lower than that of any other combinations. Apart from storage condition that was found to influence shear bond strength statistically, thermal cycling of the specimens also tended to decrease the bond strength between Estenia and the incremental materials. It was concluded that regularly-filled composites are suitable to be used as an incremental material facing Estenia in combination technique.  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