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   7564篇
  免费   886篇
  国内免费   226篇
耳鼻咽喉   19篇
儿科学   140篇
妇产科学   43篇
基础医学   2023篇
口腔科学   1569篇
临床医学   412篇
内科学   1037篇
皮肤病学   72篇
神经病学   309篇
特种医学   166篇
外国民族医学   1篇
外科学   464篇
综合类   888篇
预防医学   228篇
眼科学   45篇
药学   716篇
  3篇
中国医学   132篇
肿瘤学   409篇
  2024年   20篇
  2023年   163篇
  2022年   276篇
  2021年   395篇
  2020年   338篇
  2019年   304篇
  2018年   268篇
  2017年   264篇
  2016年   311篇
  2015年   332篇
  2014年   428篇
  2013年   562篇
  2012年   364篇
  2011年   353篇
  2010年   283篇
  2009年   295篇
  2008年   319篇
  2007年   288篇
  2006年   285篇
  2005年   245篇
  2004年   243篇
  2003年   188篇
  2002年   222篇
  2001年   158篇
  2000年   156篇
  1999年   146篇
  1998年   127篇
  1997年   136篇
  1996年   140篇
  1995年   108篇
  1994年   91篇
  1993年   98篇
  1992年   102篇
  1991年   85篇
  1990年   83篇
  1989年   71篇
  1988年   57篇
  1987年   57篇
  1986年   39篇
  1985年   63篇
  1984年   49篇
  1983年   30篇
  1982年   31篇
  1981年   19篇
  1980年   21篇
  1979年   18篇
  1978年   11篇
  1977年   11篇
  1976年   12篇
  1975年   5篇
排序方式: 共有8676条查询结果,搜索用时 171 毫秒
1.
ABSTRACT

Purpose

To investigate the expression of IL-11 and its receptor IL-11Rα and to quantify density of CD163+ M2 macrophages in proliferative diabetic retinopathy (PDR).  相似文献   
2.
In a biological microenvironment, free fatty acids (FFA) as ubiquitous biological molecules might interact with nanoparticles (NPs) and consequently change the toxicological responses. However, whether the chemical structures of FFA could influence their interactions with NPs remain unknown. This study investigated the interactions between ZnO NPs and saturated or unsaturated FFA (complexed to BSA), namely stearic acid (SA, C18:0), oleic acid (OA, C18:1), and α-linolenic acid (ALA, C18:3). It was shown that BSA, SA, OA, and ALA increased the atomic force microscope (AFM) heights as well the polydispersity index (PDI) of ZnO NPs. BSA modestly protected THP-1 macrophages from ZnO NP exposure, whereas OA and ALA led to relatively less cyto-protective effects of BSA. Moreover, only co-exposure to ZnO NPs and SA significantly promoted the release of interleukin-8. BSA, SA, OA, and ALA equally changed intracellular ROS and Zn ions associated with ZnO exposure, but co-exposure to ZnO NPs and OA/ALA particularly activated the expression of endoplasmic reticulum stress-apoptosis genes. In combination, these results showed that FFA could influence the colloidal aspects and toxicological signaling pathway of ZnO NPs, which is dependent on the number of unsaturated bonds of FFA.  相似文献   
3.
??Objective    To investigate the effect of tooth movement at different time after the repair of alveolar bone defects. Methods    Defective alveolar bone model was established on one side in forty white rabbits??which were filled with bone meal and attached with Bio-Gide membrane as experiment sides. The other side was performed routine tooth extraction as control. Track the mandibular second molar in both sides respectively in 1 week??1 month??2 months and 3 months after operation. One month later??the distance between the mandibular second molar and third molar was measured with electronic vernier caliper in the experiment side and control side. The mandibular tissue was made paraffin section and hematoxylin eosin staining. Three views of the periodontal ligament in a third place of the mesial roots of the second molar was randomly chosen to count the total number of osteoclasts. Paired-t test analysis was made to evaluate the displacement of the mandibular second molar in experiment and control side??and to evaluate the number of osteoclasts in two side. Results    In Group 1w and Group 1 m??the displacement of the mandibular second molar in experiment group was smaller than that in the control side??P??0.05??. There was no statistical significance in Group 2 m and Group 3 m. The number of osteoclasts in the experiment side was less than the control group in Group 1 w and Group1 m??P??0.05??. No statistical significance in Group 2 m and Group 3 m was found. Conclusion    Orthodontic treatment can be performed two months after the repair of alveolar bone defects.  相似文献   
4.
徐慧  陈敏  孙永峰  程星  王琦  靳蓉 《广东医学》2020,41(23):2394-2397
目的分析贵阳地区儿童重症社区获得性肺炎支气管肺泡灌洗液(BALF)病原学分布及耐药特点。方法收集989例重症社区获得性肺炎患儿临床资料,将支气管肺泡灌液采用支气管镜取出进行细菌培养、病毒以及肺炎支原体(MP)检测。结果(1)989例重症社区获得性肺炎患儿病原检出阳性716例,阳性率72.40%,细菌、病毒、支原体检出率分别33.27% (329例)、22.45%(222例)、31.45%(311例)。(2)细菌感染中的肺炎链球菌、金黄色葡萄球菌为最为常见的革兰阳性菌株(G+);而肺炎克雷伯菌、大肠埃希菌为最为常见的革兰阴性菌株(G-)。培养菌株对青霉素类、红霉素、第1、2、3代头孢类抗生素有较高的耐药性,对头孢吡肟、拉氧头孢、哌拉西林、左氧氟沙星有较高的敏感性,对亚胺培南、万古霉素、利奈唑烷均无耐药发生。(3)病毒感染检出222例,其中呼吸道合胞病毒131例,腺病毒检测49例,流感病毒6例(A型2例,B型4例),副流感病毒36例(1型3例、2型4例、3型29例),病毒检出率以0~12月龄组最高,RSV、ADV感染主要集中在冬春季节。(4)肺炎支原体检出阳性率31.45%(311例),肺炎支原体检出率以3~5岁组最高。结论贵阳地区重症肺炎中肺炎克雷伯杆菌、肺炎链球菌、大肠埃希菌、金黄色葡萄球菌为重要的细菌病原。重要病毒为腺病毒和呼吸道病毒为主,1~12月龄组的病毒感染检出率比较高。  相似文献   
5.
Arsenic pollution has become increasingly severe. It occurs as the result of geological processes and different human activities. Arsenic toxicity at the respiratory level occurs mainly by inhalation of products of coal combustion. The aim of this study was to evaluate sodium arsenite (As3+) toxicity in murine alveolar macrophages (AMs) in vitro and its association with the alterations in cell metabolism.

No changes in viability, apoptosis or cell area were detected in AMs treated with As3+ concentrations up to 2 μM for 24–96 h. A marked decrease in these end-points was observed for As3+ concentrations ranging from 2.5 μM to 10 μM.

Regarding the dynamics of the endo-exocytic process triggered by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell incorporation, no variations were detected for As3+ concentrations lower than 2 μM while higher concentrations markedly modified this response.

MTT specific activity, as a measure of cell metabolic activity, was not modified irrespective of the As3+ concentration assayed. However, nitroblue tetrazolium (NBT) specific activity, as a measure of superoxide anion generation, is responsive but only to low As3+ doses.

Although this study focuses on lung macrophages, the effects of As3+ described herein may also apply to the response of macrophages residing in other organs.

Arsenite modifies the metabolic and the oxidative status of AMs in vitro. When macrophages are in an As3+ rich medium, they exhibit a reduction in respiratory burst levels and lose their intrinsic capacity to respond to toxicants.  相似文献   

6.
Ganoderma sinensis has been used widely in Oriental countries for the prevention and treatment of various diseases including cancer. Previous studies have shown that the lipid extract from Ganoderma exhibits direct cytotoxicity against tumor cells. Here, it is reported that the lipid extract from germinating G. sinensis spores, at lower concentrations that have no direct tumoricidal activity, induce potent antitumor immune responses in human monocytes/macrophages. Upon stimulation with the lipid extract, monocytes/macrophages exhibited markedly increased production of proinflammatory cytokines and surface expression of costimulatory molecules. Conditioned medium from stimulated cells effectively suppressed the growth of tumor cells. Apparently, the lipid extract triggered macrophage activation via a mechanism different from that associated with LPS. Moreover, it was observed that the lipid extract could partially re‐establish the antitumor activity of the immunosuppressive tumor‐associated macrophages. These results indicated that in addition to its direct tumoricidal activity, the lipid extract from G. sinensis spores could exert antitumor activity by stimulating the activation of human monocytes/macrophages. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
7.
The purpose of this study is to show the spectrum of adjacent organ invasion and to make a brief review of hepatic alveolar hydatid disease (AHD), using CT and MR imaging. We retrospectively reviewed CT and MR images of three patients with various adjacent organ invasions surgically and histologically proven to be AHD. Local invasion to right kidney and adrenal, right hemidiaphragm and lung were detected in one patient, right adrenal in another patient and gall bladder, duodenum, gastric wall and pancreas invasion in the other. AHD may rarely extend to the gall bladder, stomach, duodenum, pancreas, right adrenal and kidney, diaphragm, pleura and lung. The extension of the disease outside the liver is usually encountered in patients with large, peripherally located masses in the advanced stage of the disease.  相似文献   
8.
目的:探讨腹腔内注射沙培林增强人腹腔抗癌免疫功能的机制。方法:72例早中期胃肠道肿瘤患者术前48h和24h腹腔内分别注射生理盐水和5KE的沙培林,术中采集腹腔内巨噬细胞,计数并测定乳酸脱氢酶(LDH)和酸性磷酸酶(ACP)的活性,巨噬细胞吞噬活力,一氧化氮(NO)的分泌以及对人胃癌MKN1细胞的细胞毒性进行分析。同时采集大网膜,对大网膜乳斑的数量和面积进行观察。结果:沙培林显著增加腹腔巨噬细胞(PMΦ)的数量和NO的分泌,增强LDH和ACP的活性,吞噬活力,以及抗癌细胞毒性,也显著增加了大网膜乳斑的数量和面积。结论:腹腔内注射沙培林可显著增加人大网膜乳斑的数量和面积,并因此增加PMΦ的数量,增强PMΦ的活性。因而增强了腹腔巨噬细胞的免疫功能。  相似文献   
9.
肺泡蛋白沉积症的X线与CT诊断(附4例报告并文献复习)   总被引:1,自引:1,他引:0  
目的分析肺泡蛋白沉积症的X线与CT表现,提高对本病的认识。方法回顾性分析4例经X线与CT检查并经病理证实的肺泡蛋白沉积症,分析其X线与CT征象。结果4例病变中皆见到弥漫性斑片影与磨玻璃影,CT扫描病灶呈地图样分布。结论CT对肺泡蛋白沉积症的范围、程度及病变轮廓的显示较X线平片准确,根据CT和HRCT表现的典型特征,可以作出可靠的诊断。  相似文献   
10.
目的:研究松果体和褪黑激素(Mel)是否通过下丘脑影响腹腔巨噬细胞功能.方法:松果体切除术;腹腔巨噬细胞化学发光测定;下丘脑地诺前列酮放射免疫测定;下丘脑注射Mel.结果:松果体切除后腹腔巨噬细胞化学发光值降低,下丘脑地诺前列酮含量升高,16:00 ip Mel(10 μg kg~(-1)d~(-1)×7d)可使其恢复,并升高正常大鼠腹腔巨噬细胞化学发光值,降低其下丘脑地诺前列酮含量.腹腔巨噬细胞化学发光值与下丘脑地诺前列酮含量的变化存在负相关(相关系数,r=-0.78,P<0.01).于下丘脑注射Mel 2μg,能提高正常大鼠和松果体切除大鼠腹腔巨噬细胞化学发光值.结论:下丘脑是松果体Mel影响腹腔巨噬细胞功能的主要作用部位之一.  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