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   1318篇
  免费   109篇
  国内免费   78篇
耳鼻咽喉   6篇
儿科学   47篇
妇产科学   92篇
基础医学   237篇
口腔科学   17篇
临床医学   210篇
内科学   231篇
皮肤病学   28篇
神经病学   21篇
特种医学   294篇
外科学   58篇
综合类   24篇
预防医学   66篇
眼科学   2篇
药学   90篇
肿瘤学   82篇
  2023年   4篇
  2021年   4篇
  2020年   3篇
  2019年   11篇
  2018年   25篇
  2017年   9篇
  2016年   19篇
  2015年   27篇
  2014年   36篇
  2013年   36篇
  2012年   46篇
  2011年   26篇
  2010年   38篇
  2009年   44篇
  2008年   25篇
  2007年   77篇
  2006年   22篇
  2005年   35篇
  2004年   25篇
  2003年   30篇
  2002年   30篇
  2001年   33篇
  2000年   48篇
  1999年   33篇
  1998年   76篇
  1997年   86篇
  1996年   55篇
  1995年   71篇
  1994年   45篇
  1993年   39篇
  1992年   32篇
  1991年   32篇
  1990年   20篇
  1989年   40篇
  1988年   38篇
  1987年   34篇
  1986年   36篇
  1985年   50篇
  1984年   20篇
  1983年   16篇
  1982年   30篇
  1981年   16篇
  1980年   25篇
  1979年   6篇
  1978年   8篇
  1977年   14篇
  1976年   15篇
  1975年   9篇
  1970年   3篇
  1928年   1篇
排序方式: 共有1505条查询结果,搜索用时 15 毫秒
31.
32.
目的:检测转化生长因子β1在腹膜透析大鼠腹膜内表达,并探讨其在腹膜纤维化中的意义。方法:实验于2005-06/2006-03在中南大学湘雅二医院肾内科实验室完成。①实验材料:雄性SD大鼠,体质量180~240g,由中南大学湘雅二医院动物实验中心提供。②实验方法:将28只大鼠按随机数字表随机分为4组,每组7只。正常对照组不予任何干预;生理盐水组腹腔注射20mL生理盐水;低糖透析液组腹腔注射20mL1.5%葡萄糖透析液;高糖透析液组腹腔注射20mL4.25%葡萄糖透析液,均为1次/d。4周后,向大鼠腹腔注射4.25%葡萄糖腹膜透析液20mL,4h后于大鼠右下腹缓慢插入带有多个侧孔的10号静脉留置针,缓慢低位引流腹透液,量取引流液。③实验评估:取大鼠壁层腹膜组织,以苏木素-伊红染色,镜下测量腹膜厚度,采用免疫组织化学方法检测大鼠腹膜中转化生长因子β1及纤连蛋白。结果:28只大鼠均进入结果分析。①高糖透析液组、低糖透析液组超滤量均明显低于正常对照组与生理盐水组,并且高糖透析液组超滤量明显少于低糖透析液组(P均<0.05)。②高糖透析液组腹膜明显增厚,表面粗糙,间皮细胞肿胀,脱落,间皮下有大量血管生成以及胶原纤维沉积,还可见单核细胞等炎症细胞浸润,与其他组比较,腹膜厚度明显增加(P<0.05)。③高糖透析液组转化生长因子β1、纤连蛋白表达量均明显高于其他组;低糖透析液组转化生长因子β1、纤连蛋白表达量均明显高于正常对照组与生理盐水组(P<0.05)。④大鼠腹膜组织转化生长因子β1蛋白与纤连蛋白表达量、腹膜厚度之间呈明显的正相关(r=0.86,0.83,P<0.05)。结论:葡萄糖透析液可诱导腹膜组织转化生长因子β1明显上调,腹膜转化生长因子β1高表达与腹膜透析腹膜纤维化密切相关。  相似文献   
33.
A 75-year-old native Dutch farmer presented with a painless swelling of his right hand extending into his forearm, accompanied by general malaise and low grade fever. His medical history revealed coxitis tuberculosa in 1954 and injury of the same hand in 1978. His present swelling appeared to be caused by Mycobacterium bovis, probably due to endogenous reactivation. Whether the mycobacteria reached the hand hematogenously or were directly inoculated at the time of injury of his hand in 1978 remains unclear.  相似文献   
34.
35.
Simple, low-cost PCR/PCR-restriction fragment length polymorphism (RFLP) assays targeting cyp51A promoter and codon 98 regions were developed for the detection of triazole-resistant Aspergillus fumigatus strains carrying TR34/L98H mutations. The assays were evaluated using 40 itraconazole-susceptible isolates and 35 itraconazole-resistant isolates. The prevalence of TR34/L98H mutations in clinical/environmental A. fumigatus isolates may now be determined easily from resource-poor settings.  相似文献   
36.
Trichosporon species have been reported as emerging pathogens and usually occur in severely immunocompromised patients. In the present work, 27 clinical isolates of Trichosporon species were recovered from 27 patients. The patients were not immunocompromised, except for one with acute myeloid leukemia. Sequence analysis revealed the isolation of Trichosporon dohaense Taj-Aldeen, Meis & Boekhout sp. nov., with CBS 10761T as the holotype strain, belonging to the Ovoides clade. In the D1-D2 large-subunit rRNA gene analysis, T. dohaense is a sister species to T. coremiiforme, and in the internal transcribed spacer analysis, the species is basal to the other species of this clade. Molecular identification of the strains yielded 17 T. asahii, 3 T. inkin, 2 T. japonicum, 2 T. faecale, and 3 T. dohaense isolates. The former four species exhibited low MICs for five antifungal azoles but showed high MICs for amphotericin B. T. dohaense demonstrated the lowest amphotericin B MIC (1 mg/liter). For the majority of T. asahii isolates, amphotericin B MICs were high (MIC at which 90% of isolates were inhibited [MIC90], ≥16 mg/liter), and except for fluconazole (MIC90, 8 mg/liter), the azole MICs were low: MIC90s were 0.5 mg/liter for itraconazole, 0.25 mg/liter for voriconazole, 0.25 mg/liter for posaconazole, and 0.125 mg/liter for isavuconazole. The echinocandins, caspofungin and anidulafungin, demonstrated no activity against Trichosporon species.Trichosporon species are yeast-like fungi, widely distributed in nature and commonly isolated from soil and other environmental sources, which have been involved in a variety of opportunistic infections and have been recognized as emerging fungal pathogens in immunocompromised hosts (19, 79, 80). Disseminated Trichosporon infections are potentially life-threatening and are often fatal in neutropenic patients (7, 22). Although uncommon, pathogenic species of this genus have been reported increasingly, mostly in patients with malignant diseases (3, 6, 9, 10, 11, 20, 32, 44, 47, 48, 63, 77), neonates (18, 56, 84), a bone marrow transplant recipient (22), a solid organ transplant recipient (50), and patients with human immunodeficiency virus (34, 35, 46). Trichosporon has also been reported to cause fungemia (5, 9, 25, 29, 30, 33, 53, 62). Members of the genus Trichosporon have occasionally been implicated as nail pathogens (16, 28, 74) and in subcutaneous infections (66). Trichosporon is considered an opportunistic agent, and therefore, recovery of Trichosporon species capable of growing at 37°C, especially from immunocompromised patients, should be regarded as potentially significant. Several reports have addressed the difficulty of identifying Trichosporon to the species level by physiological and biochemical characteristics (2, 64); therefore, molecular methods based on the sequencing of the internal transcribed spacer (ITS) have been developed (15, 69, 71, 72).In the present paper, we report the isolation of Trichosporon species from clinical specimens over a 4-year period in Qatar, the poor performance of biochemical identification methods, the significance of molecular identification, and the antifungal susceptibility data for the isolates. While investigating the molecular identification of Trichosporon species, we found three strains that do not match any of the published strains in the literature. We describe this organism as Trichosporon dohaense Taj-Aldeen, Meis & Boekhout, sp. nov., the name proposed for this species.  相似文献   
37.
Abstract

In this case report, we describe the outcomes of two heterotopic transplantations of cryopreserved ovarian tissue performed in a patient with HL, after 11 and 15?years of storage. At the age of 30, the patient underwent laparoscopy to collect ovarian tissue for cryopreservation before chemotherapy and radiotherapy. Eleven years later she experienced premature ovarian failure (POF). As the patient was only interested in endocrine function recovery, two heterotopic ovarian tissue transplantations were performed in the abdominal wall above the rectus muscle respectively 11 and 15?years after cryopreservation. Before transplantation, ovarian samples were analyzed to assess neoplastic contamination and tissue quality. The analysis on thawed ovarian tissue did not reveal micrometastasis and it showed well-preserved follicles and stroma. After both ovarian tissue grafting, menopausal symptoms ceased. The patient had periods approximately every 30-days and hormonal levels were within the premenopausal range. The endocrine function lasted 3-years after the first heterotopic transplantation and is still ongoing after second transplantation. Cryopreservation of ovarian tissue should be proposed to HL patients, as the incidence of POF as a long-term complication is not negligible. In these patients heterotopic transplantation is a useful tool to eliminate menopausal symptoms, preventing osteoporosis and reducing cardiovascular risks.  相似文献   
38.
A primer on cytokines: sources, receptors, effects, and inducers.   总被引:12,自引:0,他引:12       下载免费PDF全文
Protection against pathogens is a prerequisite for survival of most organisms. To cope with this continuous challenge, complex defense mechanisms have evolved. The construction, adaptation, and maintenance of these mechanisms are under control of an extensive network of regulatory proteins called cytokines. A great number of cytokines have been described over the last 2 decades. This review consists of an overview of cytokines that are involved in immune responses and describes some historical and general aspects as well as prospective clinical applications. Major biological effects together with information on cytokine receptors, producers, inducers, and biochemical and molecular characteristics are listed in tables. In addition, some basic information is given on cytokine receptor signal transduction. Finally, the recent discoveries of cytokine receptors functioning as coreceptors in the pathogenesis of human immunodeficiency virus are summarized.  相似文献   
39.
Genomic DNA from 19 Japanese patients with congenital lipoid adrenal hyperplasia (lipoid CAH) representing 16 different families was examined to identify the genetic alterations of steroidogenic acute regulatory protein (StAR). Ten of 19 patients had a 46,XX karyotype and nine had a 46,XY karyotype. Six of the 46,XX patients have experienced spontaneous pubertal changes including breast development and irregular menstruation whereas none of the 46,XY subjects displayed pubertal changes. Eight different mutations were identified. Sixteen patients were either homozygotes or compound heterozygotes for the Q258X mutation. The seven other mutations identified were 189delG, 246insG, 564del13bp, 838delA, Q212X, A218V and M225T. The 189delG, 246insG, 546del13bp and Q212X mutants encode truncated proteins. COS-1 cells transfected with expression vectors encoding cDNAs for the mutant StAR proteins which affect the C-terminus, 838delA, A218V and Q258X, exhibited no steroidogenesis enhancing activity. However, the M225T mutant retained some steroidogenic activity. The patient with the M225T mutation had late onset of this disorder and some capacity to secrete testosterone in response to hCG. These findings suggest: (i) that the Q258X mutation can be used as a genetic marker for the screening of Japanese for lipoid CAH, (ii) that the C-terminus of StAR plays an important role in the protein's activity and (iii) that there are differences in the extent of functional impairment of the testis and ovaries in lipoid CAH.   相似文献   
40.
Superoxide, an agent which attenuates the half-life of nitric oxide, is metabolized and synthesized by superoxide dismutase (SOD) and xanthine oxidase, respectively. Over the last few years much work has focused on the role of nitric oxide in human parturition. The aim of this study was to determine whether the onset of human parturition is associated with a change in the expression of copper/zinc superoxide dismutase (Cu/Zn SOD), manganese superoxide dismutase (Mn SOD) or xanthine oxidase within the uterus. Samples of myometrium, placenta, decidua and fetal membranes were obtained from women before and after the onset of labour at term. Immunocytochemistry was used to localize Cu/Zn SOD, Mn SOD and xanthine oxidase and measure SOD enzyme activity. Cu/Zn and Mn SOD-like immunoreactivity was detected in syncytiotrophoblast cells, villous stromal cells and endothelial cells of blood vessels in the placenta. In the myometrium Cu/Zn and Mn SOD were localized to myocytes and endothelial cells and to some vascular smooth muscle cells. In the fetal membranes we observed staining for Cu/Zn SOD and Mn SOD in the amnion, chorion, extravillous trophoblast and decidua. There was no difference in SOD enzyme activity or staining intensity for SOD between different cell types before and during labour. Xanthine oxidase immunoreactivity was identified in each of the tissues examined and again there was no difference in immunostaining in tissues obtained from women delivered before or after the onset of labour. These results show that the pregnant uterus is capable of both synthesizing and degrading superoxide and suggest that superoxide dismutase and xanthine oxidase may play a role in the maintenance of uterine quiescence during pregnancy, but not in the initiation of parturition.   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