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   324646篇
  免费   17491篇
  国内免费   9495篇
耳鼻咽喉   3756篇
儿科学   9219篇
妇产科学   7232篇
基础医学   37224篇
口腔科学   8279篇
临床医学   33681篇
内科学   50363篇
皮肤病学   6094篇
神经病学   16098篇
特种医学   15083篇
外国民族医学   141篇
外科学   39095篇
综合类   30300篇
现状与发展   40篇
一般理论   9篇
预防医学   28480篇
眼科学   7895篇
药学   28704篇
  234篇
中国医学   10856篇
肿瘤学   18849篇
  2023年   1969篇
  2022年   5170篇
  2021年   6558篇
  2020年   5403篇
  2019年   3987篇
  2018年   7436篇
  2017年   8278篇
  2016年   6838篇
  2015年   11044篇
  2014年   11900篇
  2013年   11190篇
  2012年   21498篇
  2011年   17052篇
  2010年   11730篇
  2009年   11774篇
  2008年   10694篇
  2007年   11108篇
  2006年   10350篇
  2005年   17630篇
  2004年   16902篇
  2003年   12158篇
  2002年   6650篇
  2001年   6901篇
  2000年   3840篇
  1999年   7471篇
  1998年   1462篇
  1992年   7174篇
  1991年   7392篇
  1990年   7601篇
  1989年   7144篇
  1988年   6663篇
  1987年   6404篇
  1986年   6058篇
  1985年   5325篇
  1984年   3630篇
  1983年   2949篇
  1979年   3841篇
  1978年   2363篇
  1977年   1782篇
  1976年   1560篇
  1975年   2477篇
  1974年   3108篇
  1973年   2743篇
  1972年   2756篇
  1971年   2742篇
  1970年   2555篇
  1969年   2465篇
  1968年   2238篇
  1967年   2163篇
  1966年   1898篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
目的观察拜唐苹治疗Ⅱ糖尿病的临床效果。方法30例病人,通过口服拜唐苹治疗一个月和一年后,记录血浆葡萄糖和血红蛋白,根据比较了解拜唐苹降糖效果。结果拜唐苹使患者的空腹血糖下降10.19%,非空腹血糖下降17.44%,血红蛋白治疗前有16人控制差,治疗后无一人控制差。结论拜唐苹治疗Ⅱ型糖尿病中空腹血糖轻中度增高,餐后血糖增高显著的病例,效果满意,副作用少。  相似文献   
102.
103.
研究了谷氨酰胺转移酶(TGase)对大豆蛋白膜特性的影响。研究表明:在成膜溶液中加入TGase(4U/g)可以使膜的抗拉强度增加16.79,6,表面疏水性增加39.2%,同时也明显降低了膜的断裂伸长率、水分含量、总可溶性物质量及透光率,但是对水蒸气转移速率几无影响。扫描电镜(SEM)显示,酶法交联膜的表面比对照膜略为粗糙,断面却更为均匀致密。SDS-PAGE分析表明,TGase催化SPI产生了共价交联。  相似文献   
104.
徐燕 《中国卒中杂志》2006,1(2):114-116
随着诊断技术水平的提高,愈来愈多的证据表明心源性栓子是缺血性脑卒中患者发病的重要原因,据估计,约15%~20%的脑梗死患者是由心源性栓塞引起。因缺乏金标准,临床常推测诊断,如果患者有全身性栓塞的病史和表现,又有心脏  相似文献   
105.
OBJECTIVE: Spinal reflexes from hand to wrist muscles were investigated in writer's cramp. METHODS: Stimulus-triggered rectified EMG averages after ulnar nerve and cutaneous stimulation, in wrist flexors and extensors during tonic contraction, were compared in 18 controls and 19 patients. RESULTS: On the patient dystonic side, ulnar-induced EMG suppression was decreased in wrist extensors, and facilitation in wrist flexors modified dependent on the dystonic wrist posture during writing. No change was found on the patient non-dystonic side. Cutaneous stimulation increased wrist flexor EMG on both sides of the patients with normal wrist posture during writing, but had no effect in controls and patients with abnormal wrist posture. CONCLUSIONS: Comparison between cutaneous and mixed nerve stimuli suggests that spindle afferents from intrinsic hand muscles may mediate patients' ulnar-induced EMG modulations. Abnormal proprioceptive control was only observed on dystonic side, while bilateral unusual cutaneous control was found in patients. Changes in spinal transmission were partly related to the dystonic wrist posture, suggesting that systems involved in sensory processing can be differentially altered in writer's cramp. SIGNIFICANCE: Changes in spinal transmission, probably related to peripheral and/or cortical inputs, might either take part in primary or adaptive mechanisms underlying writer's cramp.  相似文献   
106.
The histologic distinction between peritoneal epithelioid mesotheliomas and serous carcinomas diffusely involving the peritoneum may be difficult, but it can be facilitated by the use of immunohistochemistry and electron microscopy. D2-40 and podoplanin are two recently recognized lymphatic endothelial markers that can be expressed in normal mesothelial cells and mesotheliomas. The purpose of this study is to compare the value of these new mesothelial markers with those that are commonly used for discriminating between mesotheliomas and serous carcinomas, and also to determine the current role of electron microscopy in distinguishing between these malignancies. A total of 40 peritoneal epithelioid mesotheliomas and 45 serous carcinomas of the ovary (15 primary, 30 metastatic to the peritoneum) were investigated for the expression of the following markers: D2-40, podoplanin, calretinin, keratin 5/6, thrombomodulin, MOC-31, Ber-EP4, B72.3 (TAG-72), BG-8 (Lewis(Y)), CA19-9, and leu-M1 (CD15). All 40 (100%) of the mesotheliomas reacted for calretinin, 93% for D2-40, 93% for podoplanin, 93% for keratin 5/6, 73% for thrombomodulin, 13% for Ber-EP4, 5% for MOC-31, 3% for BG-8, and none for B72.3, CA19-9, or leu-M1. All 45 (100%) serous carcinomas were positive for Ber-EP4, 98% for MOC-31, 73% for B72.3, 73% for BG-8, 67% for CA19-9, 58% for leu-M1, 31% for keratin 5/6, 31% for calretinin, 13% for D2-40, 13% for podoplanin, and 4% for thrombomodulin. After analyzing the results, it is concluded that Ber-EP4 and MOC-31 are the best negative mesothelioma markers for differentiating between epithelioid mesotheliomas and serous carcinomas. The best discriminators among the positive markers for mesotheliomas are D2-40, podoplanin, and calretinin. From a practical point of view, Ber-EP4 and MOC-31, in combination with calretinin, and/or D2-40 or podoplanin allow the differential diagnosis to be established between mesothelioma and serous carcinoma in nearly all instances. As a clear distinction could be made between these two malignancies in all of the cases in which electron microscopy was performed, this technique can be very useful in establishing the correct diagnosis when the immunohistochemical results are equivocal or further support of a diagnosis of either mesothelioma or serous carcinoma is needed.  相似文献   
107.
目的 观察妊娠对大鼠吸人性全麻药血,气分配系数及组织,气分配系数的影响。方法 健康成年(3月龄)雌性妊娠(妊娠18—22d)和非妊娠SD大鼠各10只,分别为妊娠组和非妊娠组。腹腔注射戊巴比妥钠40mg/kg麻醉,经腹主动脉抽血用于测血,气分配系数,放血处死后,分别取心、肝、肾及脑组织并制成匀浆,采用注射器顶空二次平衡法经气相色谱仪测定七氟醚、异氟醚和氟烷的血,气分配系数及组织,气分配系数。结果与非妊娠组相比,妊娠组氟烷的血,气分配系数和脑,气分配系数降低(P〈0.05),七氟醚、异氟醚的血,气分配系数、肝,气分配系数、肾,气分配系数、心,气分配系数差异无统计学意义(P〉0.05)。结论 妊娠降低大鼠氟烷的血,气配系数和脑,气分配系数,但不影响七氟醚和异氟醚的血,气分配系数和组织,气分配系数。  相似文献   
108.
了解小颗粒致密低密度脂蛋白中抗氧化维生素含量、氧化特性 ,探讨其对血管内皮细胞脂质过氧化的影响。采用二次密度梯度超速离心的方法分离制备小颗粒致密低密度脂蛋白 ,高压液相色谱测定其抗氧化物质维生素A、E和 β 胡萝卜素 ;连续监测小颗粒致密低密度脂蛋白在 2 34nm的吸光度以测定其氧化敏感曲线 ;在血管内皮培养液中分别加入不同浓度的小颗粒致密低密度脂蛋白 ,培养后测定培养液丙二醛的浓度。实验成功分离小颗粒致密低密度脂蛋白 ,与大而轻低密度脂蛋白相比 ,维生素A、E和 β 胡萝卜素等抗氧化物质及总抗氧化能力明显减少 ,只有大而轻低密度脂蛋白的 6 5 %、39%和 2 4 % ,故小颗粒致密低密度脂蛋白氧化的延迟时间只有大而轻低密度脂蛋白的 37.5 % ,但硫代巴比妥酸反应物质值及氧化速率分别是大而轻低密度脂蛋白的 1 .7倍和 1 .2 8倍 ;培养液中丙二醛含量随加入脂蛋白的浓度和作用时间而增高 ,2 4h时小颗粒致密低密度脂蛋白 5 0mg组、1 0 0mg组、1 5 0mg组与相同剂量大而轻低密度脂蛋白组比较丙二醛显著增高 (P <0 .0 5 )。上述结果提示 :小颗粒致密低密度脂蛋白中抗氧化物质及抗氧化能力下降 ,氧化敏感性增高 ,并促进内皮细胞过氧化损伤  相似文献   
109.
The New Zealand obese mouse (NZO/Hl) is characterised by hereditary obesity and type-2 diabetes, including insulin resistance, hyperinsulinaemia, and glucose intolerance. In other diabetic models, it has been revealed that the proper functioning of the glucose transporter isoform 2 (GLUT2) is essential for adequate secretion of insulin. The aim of this study was to compare the distribution of islet cells and GLUT2, as well as the expression of GLUT2-mRNA, in the pancreas of NZO mice and metabolically unimpaired NMRI (Naval Medical Research Institute) mice. Pancreas tissue was obtained from different stages of development. For molecular determination of the expression level of GLUT2-mRNA, total-RNA was extracted from the pancreas and analysed by quantitative real-time RT-PCR. All investigated NZO mice displayed increased weight, elevated hyperinsulinaemia, and slightly enhanced blood glucose levels compared with the NMRI control mice. By means of immunofluorescence microscopy drastically reduced insulin levels were detected, which might be compensated by the observed islet cell hyperplasia and hypertrophy. Furthermore, the normally peripheral localisation of the alpha-cells within islets was disturbed. By contrast, there were no changes in somatostatin cell distribution. However, considerable differences appeared with regard to GLUT2: whereas the beta-cells of NMRI mice showed dense immunostaining of the GLUT2 transporter on the cell surface, in all age groups of NZO mice, GLUT2 on the plasma membranes was reduced and dispersed in the cytoplasm. These findings agree with the molecular biological results, which displayed decreased mRNA-expression of GLUT2. In summary, the observed alteration of islet morphology and of GLUT2 expression in diabetic mice complements our previous results from a superfusion protocol and further clarifies the mechanisms of diabetogenesis in NZO mice.  相似文献   
110.
INTRODUCTION The exact cause of Parkinson disease (PD) has not been known yet[1]. The overwhelming progress had been made in the treatment and pathogenesis of PD in recent 30 years, especially 10 years[2]. But it is still no way now to prevent or postpone…  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