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   35991篇
  免费   1724篇
  国内免费   295篇
耳鼻咽喉   266篇
儿科学   682篇
妇产科学   413篇
基础医学   4786篇
口腔科学   1002篇
临床医学   2109篇
内科学   8972篇
皮肤病学   855篇
神经病学   2455篇
特种医学   1253篇
外科学   6478篇
综合类   139篇
一般理论   1篇
预防医学   988篇
眼科学   630篇
药学   2085篇
中国医学   123篇
肿瘤学   4773篇
  2024年   24篇
  2023年   202篇
  2022年   531篇
  2021年   881篇
  2020年   451篇
  2019年   648篇
  2018年   849篇
  2017年   662篇
  2016年   779篇
  2015年   811篇
  2014年   1081篇
  2013年   1372篇
  2012年   2238篇
  2011年   2621篇
  2010年   1475篇
  2009年   1215篇
  2008年   2232篇
  2007年   2468篇
  2006年   2309篇
  2005年   2483篇
  2004年   2397篇
  2003年   2396篇
  2002年   2401篇
  2001年   361篇
  2000年   304篇
  1999年   432篇
  1998年   575篇
  1997年   454篇
  1996年   431篇
  1995年   371篇
  1994年   325篇
  1993年   297篇
  1992年   214篇
  1991年   187篇
  1990年   183篇
  1989年   165篇
  1988年   148篇
  1987年   108篇
  1986年   100篇
  1985年   88篇
  1984年   104篇
  1983年   85篇
  1982年   71篇
  1981年   87篇
  1980年   82篇
  1979年   59篇
  1978年   41篇
  1977年   29篇
  1976年   24篇
  1975年   23篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
侵袭性脑膜瘤的影像学特征与手术策略   总被引:2,自引:0,他引:2  
目的探讨侵袭性脑膜瘤的影像特征和手术治疗方法。方法回顾性分析56例侵袭性脑膜瘤患者的临床表现、影像学检查、病理结果及手术治疗情况等资料。结果56例侵袭性脑膜瘤在影像学上表现有颅骨的局部增生(18例),肿瘤侵蚀破坏颅骨(11例),硬脑膜“尾”征(27例),瘤-脑界面部分或完全消失(29例),肿瘤边界毛糙模糊、结节状或指状突出、伪足征(24例)。肿瘤粘附或侵入静脉窦或海绵窦(9例),包绕大血管4例,瘤周明显水肿(39饼)等。手术切除按Simpson标准分级,其中0级21例,Ⅰ级19例;Ⅱ级9例,Ⅲ级7例。术后随访0.5—8年,痊愈49例,轻度功能障碍7例。无死亡病例,复发4例。结论侵袭性脑膜瘤有较特殊的影像学特征,可为临床诊断和手术治疗提供参考。尽可能地行病灶根治性切除能有效地减少肿瘤的复发。  相似文献   
142.
Prostaglandin E1 (PGE1) has several potential therapeutic effects, including cytoprotection, vasodilation, and inhibition of platelet aggregation. This study investigates the protective action of PGE1 against hepatic ischemia/reperfusion injury in vivo using a complementary DNA microarray. PGE1 or saline was continuously administered intravenously to mice in which the left lobe of the liver was made ischemic for 30 minutes and then reperfused. Livers were harvested 0, 10, and 30 minutes postreperfusion. Messenger RNA was extracted, and the samples were labeled with two different fluorescent dyes and hybridized to the RIKEN set of 18,816 full-length enriched mouse complementary DNA microarrays. Serum alanine aminotransferase and aspartate aminotransferase levels at 180 minutes postreperfusion were significantly lower in the PGE1-treated group than in the saline-treated group. The cDNA microarray analysis revealed that the genes encoding heat-shock protein (HSP) 70, glucose-regulated protein 78, HSP86, and glutathione S-transferase were upregulated at the end of the ischemic period (0 minutes postreperfusion) in the PGE1 group. Our results suggested that PGE1 induces HSPs immediately after ischemia reperfusion. HSPs might therefore play an important role in the protective effects of PGE1 against ischemia/reperfusion injury of the liver.  相似文献   
143.
PURPOSE: We assessed the feasibility of utilizing three-dimensional (3D) phase sensitive inversion recovery (IR) images for preoperatively determining deep brain stimulator position. METHODS: We measured geometric distortion with a grid phantom and evaluated images of 3 volunteers to determine optimum imaging parameters for 3D phase sensitive IR. RESULTS: Geometric distortion measured less than 1.0%. Respective inversion and recovery times, which provided high T(1) contrast between the subthalamic nucleus and adjacent tissue, were 200 and 4000 ms. In studies of 3 volunteers and 2 patients, the subthalamic nucleus was clearly depicted in 3D phase sensitive IR images. The measured coordinates of the subthalamic nucleus agreed well with those calculated by conventional estimation from midpoint of the anterior and posterior commissure. CONCLUSION: Three-dimensional phase sensitive inversion recovery was useful in visualizing the subthalamic nucleus for effective deep brain stimulation.  相似文献   
144.
We present here a rare case of left-side catamenial pneumothorax, in which endometrial tissue pleura was found on the visceral pleura histologically. A chest roentogenogram confirmed the left pneumothorax, but did not reveal bullae or any associated anomalies, in a 41-year-old woman with three documented episodes of left-side pneumothorax occurring every menstruation. Video-assisted thoracoscopic surgery revealed not only tiny holes in the diaphragm, but also a scattered small brown spots on the visceral pleura. Histological examination of the lung sections revealed the existence of endometrial tissue on the visceral pleura with disrupted pleural elastic fibers. Our case suggests that cyclic erosion of the visceral pleura by the implanted endometrial tissue caused air leakage from the lung, in addition to the most accepted concept that air is aspirated into the thoracic cavity via the abdomen through the acquired fenestration of the diaphragm.  相似文献   
145.
We report a rare case of constrictive pericarditis that stimulated a large mediastinal tumor obstructing the right ventricular inflow tract. A 58-year-old woman was referred to our hospital because of a recent increase of dyspnea and facial edema. Computed tomography revealed severely thickened calcification, including a low-density area, presenting as a mediastinal tumor, compressing the right ventricular inflow tract. A complete resection was performed, and her symptoms dramatically improved. Idiopathic constrictive pericarditis was diagnosed pathologically.  相似文献   
146.
147.
We investigated whether topical instillation of an alpha(1)-adrenergic blocker would improve an insufficient blood supply in the optic nerve head (ONH) and visual function, in rabbits. The effect of systemic NOS inhibition on visual-evoked potentials (VEPs) and hemodynamics in ONH were determined. VEPs were recorded before and every 15 min during a 120-min observation period after an intravenous injection of 50 mg/kg N(G)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase (NOS) inhibitor. Capillary blood flow in ONH was evaluated by the laser speckle method throughout the same period. Then, we investigated the effect of topical instillation of a recently developed alpha(1) adrenergic blocker, bunazosin hydrochloride (0.01%), 60 min prior to the intravenous L-NAME (50 mg/kg) on the changes by NOS inhibition. The VEP amplitudes were reduced by L-NAME (10, 20, and 50 mg/kg) in a dose-dependent manner, while the VEP implicit time was unchanged, and no significant changes were detected in the electroretinogram. The reductions in ONH capillary blood flow and VEP amplitudes caused by L-NAME (50 mg/kg) were significantly suppressed by an instillation of bunazosin hydrochloride. These results indicate that blocking alpha(1)-adrenergic receptors may ameliorate the impairments in blood flow and retinal function caused by NOS inhibition. The enhancement of basal vascular tone due to deprivation of continuous NO production may be diminished by this alpha(1)-adrenergic blocker.  相似文献   
148.
Previous studies using primary monolayer cultures of epithelial cells from the involved epidermis of patients with mammary and extramammary Paget's disease investigated whether Paget cells proliferate as other malignant cells do. Although epithelial monolayers from the involved skin were maintained for approximately 45 days, no permanent cell lines were established. The proportion of carcinoembryonic antigen (CEA)-positive cells did not increase in the long-term cultures. Herein, we report studies of whether there is a real reduction of Paget cell numbers or if this is merely a decrease in the expression of CEA by the cells. Furthermore, we investigated whether Paget cells survive longer when cultured free from any potential inhibitory keratinocytes or other epidermal cells. Skin samples were obtained from one patient with mammary Paget's disease and three with extramammary Paget's disease; epidermal cells were cultured in vitro. An enrichment of Paget cells was carried out from the cultured epidermal cells by combining an anti-epithelial membrane antigen monoclonal antibody, binding to immunobeads, and density gradient centrifugation in Nycodenz. The separated cells were re-cultured in Keratinocyte-SFM serum-free media. The proportion of CEA-positive cells did not increase in the cultures, and the purified cells did not show any increase in survival times compared to the non-purified cultured cells. These results suggest that the decrease of CEA-positive cells noted during culture results from a decline in expression of CEA in the Paget cells. Paget cells in the involved epidermis do not proliferate significantly and thus differ from many other malignant cells.  相似文献   
149.
150.
Primary leiomyosarcoma of the thyroid gland   总被引:1,自引:0,他引:1  
Primary leiomyosarcoma of the thyroid gland is extremely rare, and to the best of our knowledge only five well-documented cases have been reported in the world literature. We herein report a 58-year-old female patient with primary leiomyosarcoma of the thyroid who was successfully treated by total thyroidectomy with a modified neck dissection. Immunohistochemically, the tumor cells showed positive reactivity to α-smooth muscle actin and vimentin. Radical surgery was thus considered to be essential in the treatment of this rare but rather aggressive malignancy.  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