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   5310篇
  免费   402篇
  国内免费   186篇
耳鼻咽喉   86篇
儿科学   124篇
妇产科学   52篇
基础医学   522篇
口腔科学   257篇
临床医学   501篇
内科学   674篇
皮肤病学   125篇
神经病学   313篇
特种医学   230篇
外科学   731篇
综合类   744篇
现状与发展   1篇
预防医学   473篇
眼科学   60篇
药学   504篇
  1篇
中国医学   217篇
肿瘤学   283篇
  2024年   16篇
  2023年   51篇
  2022年   133篇
  2021年   152篇
  2020年   131篇
  2019年   83篇
  2018年   93篇
  2017年   115篇
  2016年   88篇
  2015年   141篇
  2014年   196篇
  2013年   226篇
  2012年   347篇
  2011年   350篇
  2010年   306篇
  2009年   289篇
  2008年   302篇
  2007年   358篇
  2006年   280篇
  2005年   280篇
  2004年   260篇
  2003年   181篇
  2002年   158篇
  2001年   157篇
  2000年   169篇
  1999年   122篇
  1998年   41篇
  1997年   22篇
  1996年   40篇
  1995年   34篇
  1994年   19篇
  1993年   19篇
  1992年   61篇
  1991年   59篇
  1990年   51篇
  1989年   44篇
  1988年   38篇
  1987年   46篇
  1986年   35篇
  1985年   42篇
  1984年   24篇
  1979年   17篇
  1977年   20篇
  1973年   16篇
  1972年   16篇
  1971年   19篇
  1970年   15篇
  1969年   21篇
  1967年   20篇
  1966年   15篇
排序方式: 共有5898条查询结果,搜索用时 0 毫秒
21.
Complementary, or alternative, medicine has increased in popularity among patients during the past 20 years. The purpose of this study was to determine whether general practitioners met their patients' expectations with regard to complementary medicine. In a postal survey all 71 accredited general practitioners in the district of Kassel, Germany, received a structured questionnaire about their experience with complementary medicine. Forty (56%) replied. In 10 of these practices 310 patients were interviewed about their attitudes towards and expectations of such treatment. Of the responding doctors 95% used, at least occasionally, some form of complementary medicine (most commonly herbal medicine, neural therapy or homeopathy). All but three patients accepted the value of complementary medicine, 58% of them (especially younger, more highly educated patients and those from rural practices) preferred it to orthodox medicine and 40% of the patients had received some form of complementary therapy. Nearly 70% of the patients requested that complementary medicine be practised by their general practitioner more frequently than at present. There was no significant link between patient satisfaction with the doctor and patients' view of, or demand for, complementary medicine. Although both patients and practitioners were interested in complementary therapy, there was a gap between the willingness, or the ability, of general practitioners to use complementary medicine and the patients' demand for these alternative forms of treatment.  相似文献   
22.
低强度脉冲电磁场对大鼠骨质疏松的影响   总被引:1,自引:0,他引:1  
目的:观察低强度脉冲电磁场(pulsed electromagnetic fields,PEMFs)对去卵巢诱导骨质疏松症的大鼠生化指标和骨应力的影响。方法:雌性SD大鼠30只,随机等分为3组(n=10),分别为假手术组(Sham)、骨质疏松模型组(Model)、脉冲电磁场照射组(PEMFs)。经适应4wk后,在25mg·Kg^-1戊巴比妥钠腹腔麻醉下,Model组和PEMFs组摘除双侧卵巢.Sham组找到但不切除卵巢。各实验组均在相同环境下饲养,模型制备4wk后开始治疗,由GZY型低强度低频率脉冲电磁场发生仪产生低频脉冲磁场,根据实验要求,我们使用亥姆霍兹线圈形成均匀磁场,PEMFs组经照射刺激治疗,频率14.3Hz,场强2Gs.日照8h。Model组和Sham组正常饲养。治疗8wk后,对各组大鼠血清、尿液中ALP和Ca以及骨应力进行检测。结果:(1)ALP、Ca检测结果:与Model组相比,PEMFs组ALP值、Ca值差异均有统计学意义(P〈0.05)。其中,血清中ALP值,Model组为(275.16±228,57),PEMFs组为(179.30±87.68);Ca值,Model组为(2,66±0,13),PEMFs组为(2.52±0.05)。(2)骨应力检测结果:Model组为(923.60±34.15Pa),PEMFs组为(1152.85±118,20Pa),组间差异有统计学意义(P〈0.05)。结论:研究发现,PEMFs对于促进骨重建、提高Ca吸收和骨应力恢复具有积极作用。  相似文献   
23.
A glomus tumor of the stomach was found in a 79-year-old white man who had episodes of upper gastrointestinal bleeding. Clinically, this uncommon gastric tumor mimics most of the benign and malignant lesions of the stomach. The most important aspect of this tumor, therefore, is its histologic identification and differentiation from the more common gastric lesions, most especially malignant tumors. This is of paramount importance because the glomus tumor is essentially benign and does not warrant a radical surgical procedure. The histologic and ultrastructural features of this particular gastric neoplasm are presented and discussed.  相似文献   
24.
Pre-mRNA splicing is a fundamental process required for the expression of most metazoan genes. It is carried out by the spliceosome that catalyzes the removal of non-coding intron sequences to ligate exons into mature mRNA prior to transport and translation. The purpose of our study is to explore whether the in vitro unlabeled pre-mRNA splicing assay could be performed as an alternative method of splicing reaction other than the radiolabeled one. Two different splicing methods in vitro , P labeled and unlabeled pre-mRNA as the substrates in the reaction, were investigated. The radiolabeled products were visualized by autoradiography while the unlabeled products were observed by Ethidium Bromide (EB) staining. As a result, although there are more unspecific bands in the EB staining assay than 32P labeled one, the RNA products of in vitro splicing could be observed clearly. This suggests that the unlabeled pre-mRNA splicing assay can be an optional substitution for the isotope-labeled assay.  相似文献   
25.
随着乳腺癌治疗方案的不断改进和发展,临床医师对乳腺癌病理诊断报告的内容和标准有了更多和更高的要求.  相似文献   
26.
This study explored the relationship between ecologic risk factors and infant birthweight. A stratified analysis was performed on all African-American, Mexican-American, and white infants born in Chicago in 1990. One half of African-American mothers (n = 26,799) resided in communities with multiple ecologic risk factors, yet their very low birthweight rates were unaffected by the number of these factors. By contrast, only 5% of Mexican-American mothers (n = 9913) and 5% of white mothers (n = 13,596) lived in communities with multiple ecologic risk factors. Their very low birthweights were twice that of infants born to mothers who resided in communities with no ecologic risk factors. These results indicate that ecologic risk factors affect the very low birthweight rates of Mexican Americans and whites but not African Americans.  相似文献   
27.
IFN-γ在沙眼衣原体呼吸道感染中免疫防御机制的探讨   总被引:1,自引:0,他引:1  
目的:检测与IFN-γ作用相关的酶吲哚胺2,3二氧化酶(IDO)、诱导性一氧化氮合成酶(iNOS)和NADPH氧化酶(ox)gp91在沙眼衣原体呼吸道感染中的表达及与机体防御的关系,探讨衣原体感染中IFN-γ免疫防御作用的机制.方法:用沙眼衣原体小鼠肺炎株(MoPn)通过鼻腔感染C57BL/6(H-2b)小鼠,用过氧化物酶连接的鼠抗衣原体脂多糖单抗染色HeLa 229细胞,检测衣原体在肺组织的生长;用RT-PCR检测衣原体感染后第7及14天小鼠肺组织IFN-γ、IDO、iNOS和gp91NADPH ox mRNA表达.结果:MoPn呼吸道感染后小鼠肺组织匀浆衣原体活性测定,于感染后第2天,HeLa 229细胞内可见有衣原体包涵体生长,IFU值增高,于感染后第7天IFU达最高水平,以后逐渐下降,至感染后21天基本恢复到基线水平.与未感染的对照组比较,Th1细胞因子IFN-γ于感染后第7天表达显著增高,感染后14天有所降低,但仍维持较高水平;同时衣原体感染可显著诱导与IFN-γ作用相关的三种酶IDO、iNOS和gp91 NADPH ox在小鼠肺组织的表达,感染后第7及14天,IDO,iNOS及gp91 NADPH ox的表达与对照组比较均有显著差异,其中IDO和gp91 NADPH ox于感染后第7天mRNA表达增高显著(P<0.01),14天略有下降(P<0.05).结论:衣原体呼吸道感染诱导Th1细胞因子IFN-γ mRNA高表达,参与宿主对衣原体的清除及机体免疫防御,此作用可能与其相应的酶IDO、iNOS和gp91 NADPH ox表达增高有关.  相似文献   
28.
人λ-干扰素在BHK-21中的表达及生物学活性的研究   总被引:1,自引:0,他引:1  
目的:研究HuIFN-λ1和HuIFN-λ2真核细胞重组表达及其生物学活性.方法:用水疱性口炎病毒(VSV)刺激人宫颈癌HeLa细胞, 用RT-PCR克隆HuIFN-λ1和HuIFN-λ2基因, 与PCAGG-EGFP真核表达载体连接, 构建重组体PCAGG-HuIFN-λ1和PCAGG-HuIFN-λ2并进行鉴定, 后在BHK-21细胞进行表达, 采用VSV*GFP于人肺腺癌A549上进行表达产物抗病毒活性测定;并通过已构建的MDBK-Mxp-Luc细胞系对HuIFN-λ1和HuIFN-λ2诱导MxA抗病毒蛋白产生的特性进行研究.结果:HuIFN-λ1-PMD18-T Vector和HuIFN-λ2-PMD18-T Vector的SacⅠ、XhoⅠ和SacⅠ和SalⅠ双酶切鉴定, 均出现610 bp大小的带, 测序示与GenBank上报道的序列完全一致.PCAGG-HuIFN-λ1活性104 IU/mL, PCAGG-HuIFN-λ2活性为102 IU/mL, 且PCAGG-HuIFN-λ1诱导Mx抗病毒蛋白的表达一定时间内随时间延长表达不断增强, 9~12 h达高峰, 24 h后消失(P<0.05).结论:成功构建了PCAGG-HuIFN-λ1PCAGG-HuIFN-λ2 的真核表达载体并在BHK-21细胞中得到表达, 其抗病毒活性与诱导Mx抗病毒蛋白密切相关.  相似文献   
29.
Numerous mitochondria ranging from slightly larger than normal to several micrometers in diameter (giant) were found in about one-half the serous secretory cells in the surface epithelium of the normal gerbil trachea and proximal bronchi. Tracheal serous cells of mice also were found to contain numerous giant mitochondria. Clara cells of gerbil bronchioles contained abundant giant mitochondria in addition to normal tubular mitochondria and the second population of enlarged spherical mitochondria that have been described in Clara cells of several genera. In contrast, mouse Clara cells revealed the normal tubular and the enlarged spherical mitochondria but no giant mitochondria. A survey of a number of cell types in gerbils failed to disclose hypertrophied mitochondria outside tracheobronchial surface epithelium and bronchioles. The mitochondrial enlargement resulted from an increase of matrix but not cristae. The expansion of matrix displaced the relatively sparse cristae into small collections compressed against the outer membrane. The prevalence of giant mitochondria and of granular endoplasmic reticulum is similar among cells, and these two organelles are codistributed within cells. The megamitochondria and granular reticulum occupy a central stratum, whereas normal mitochondria occur in the apical and basal regions. The giant mitochondria are considered related to a normal biologic activity that is characteristic of respiratory tract epithelium of mice and gerbils selectively and is more prominent in secretory cells than in ciliated cells.  相似文献   
30.
High frequency jet ventilation (HFJV) was used in 68 patients which were treated with extracorporal shock wave lithotripsy (ESWL) because of stone diseases in the upper urinary tract. The question was whether HFJV in combination with a semiclosed conventional circle system offered a practicable and safe technique to minimize the oscillations which are proportional to the applied tidal volume and to the diaphragmatic movements. With IPPV the mean distance of the stone movement was 32 mm, whereas with the application of HFJV the stones oscillated around their resting position within limits of 2 to 3 mm (ventilation frequency: 200-300/min, driving pressure: 0.6-1.1 bar, tidal volume: 3-8 1/min). The effectiveness of HFJV was monitored by the end-tidal carbon dioxide tension (PeCO2) during intermittently conventional ventilation with "adequate" tidal volumes (TV 15 ml/kg bw). The correlation between PeCO2 and simultaneous measured PaCO2 was r = 0,91. The application of HFJV enhances the efficiency of ESWL. So the treatment of stones of the upper urinary tract can be varied by more subtle dosage of the incoming shock wave energy and by stabilisation of the stones in the underlying ellipsoid of the energy focus.  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