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   1441篇
  免费   70篇
  国内免费   113篇
耳鼻咽喉   1篇
儿科学   68篇
妇产科学   28篇
基础医学   162篇
口腔科学   22篇
临床医学   166篇
内科学   347篇
皮肤病学   50篇
神经病学   42篇
特种医学   410篇
外国民族医学   1篇
外科学   49篇
综合类   40篇
预防医学   62篇
眼科学   17篇
药学   90篇
中国医学   1篇
肿瘤学   68篇
  2022年   5篇
  2021年   9篇
  2020年   7篇
  2019年   13篇
  2018年   18篇
  2017年   6篇
  2016年   24篇
  2015年   22篇
  2014年   23篇
  2013年   42篇
  2012年   16篇
  2011年   33篇
  2010年   50篇
  2009年   51篇
  2008年   25篇
  2007年   67篇
  2006年   34篇
  2005年   55篇
  2004年   15篇
  2003年   18篇
  2002年   17篇
  2001年   15篇
  2000年   25篇
  1999年   26篇
  1998年   92篇
  1997年   96篇
  1996年   106篇
  1995年   67篇
  1994年   63篇
  1993年   64篇
  1992年   15篇
  1991年   29篇
  1990年   29篇
  1989年   55篇
  1988年   40篇
  1987年   55篇
  1986年   33篇
  1985年   45篇
  1984年   27篇
  1983年   17篇
  1982年   28篇
  1981年   21篇
  1980年   31篇
  1979年   8篇
  1978年   11篇
  1977年   16篇
  1976年   26篇
  1975年   17篇
  1970年   4篇
  1969年   3篇
排序方式: 共有1624条查询结果,搜索用时 15 毫秒
21.
Needle biopsy of renal allografts: comparison of two techniques   总被引:2,自引:0,他引:2  
Two techniques for renal allograft biopsy were retrospectively evaluated to compare relative safety and efficacy. After ultrasound (US) localization of the kidney and biopsy with a hand-held 14-gauge cutting needle, an adequate specimen was obtained in 74 of 77 cases (96%). Major complications occurred in six of these 77 cases (8%). One hundred four biopsies were performed by using a smaller 18-gauge cutting needle with a spring-loaded biopsy "gun" and real-time US guidance. With this newer technique, specimens adequate for diagnosis were obtained in 99 biopsies (95%). There was a single major complication with this technique (1%). The 18-gauge needle with real-time US guidance yields comparably adequate specimens with a lower frequency of complications.  相似文献   
22.
易军  戴辉  张聚良 《医学争鸣》2000,21(5):86-86
0 引言 胰腺多房性潴留性囊肿极为罕见,我科收治1例,报道如下.1 病例报告 患者,男,29岁,因发现右上腹包块11d入院,缘于11d前无明显诱因感右上腹痛,仅局限于右上腹部,无肩背部放散痛,伴间歇性发热,体温最高达38.3℃,经抗炎,对症治疗无效.并逐渐可触及右上腹有一肿块,在当地医院行穿刺检查为脓血性液体.镜检发现炎性细胞,B超示:胆囊窝下方及右肾内侧及腹腔动脉,下腔静脉外前方可见异常区,大小约9.1cm×6.6cm×7.6cm,边界清楚,形态不规则,内呈蜂窝状,可见多个大小不等的液性暗区,CT示:右上腹部上腔静脉前方6.0cm×9.0cm肿块和周围组织粘…  相似文献   
23.
A young boy presented with an uncommon finding of impaction of upper right central incisor and transposition of canine and lateral incisor on the same side. Esthetic management of his cosmetic problem which included fixed appliance therapy followed by light cure restorations is discussed.KEY WORDS: Impaction, Transposition  相似文献   
24.
PURPOSE: We investigated 201Tl myocardial uptake with(out) nonuniform attenuation compensation in ischemic myocardiopathy patients. The segmental patterns of the two types of SPECT images were compared with PET [13N]NH3 studies performed in the same patient. PET images were taken as reference and the diagnostic accuracy of SPECT with(out) attenuation correction was evaluated. MATERIAL AND METHODS: During the SPECT study transmission and emission data were simultaneously recorded by a triple head gamma camera equipped with fan beam collimators and a 99mTc transmission line source (740MBq). SPECT and PET images, the former reconstructed with(out) attenuation correction, were corecorded and reoriented along the short axis. The left ventricular wall was divided into 11 segments and segmental activity normalized to maximum in each study. RESULTS: Statistically significant differences were found between PET/(un)corrected SPECT ratios in posterior and septal segments. In these myocardial regions, attenuation correction compensates for attenuation artifacts, by correcting the underestimation of radioactivity concentration caused by radiation absorption. A statistically significant difference was also found in midventricular anterior and apical segments (p < .05). However, in these regions attenuation correction results in a decrease in corrected relative to uncorrected SPECT activity. The agreement rate with PET data is higher for corrected SPECT (mean differences were 3.12 +/- 11.51 and 2.19 +/- 8.63 for uncorrected versus corrected SPET). We had 50% positive and 77% negative predictive value without attenuation correction, versus up to 69% and 90%, respectively, with attenuation correction. CONCLUSIONS: The attenuation correction procedure with simultaneous transmission-emission effectively reduces attenuation artifacts in SPECT myocardial imaging. While diagnostic accuracy increases in posterior and septal myocardial regions, anterior and apical data need careful interpretation because a relative decrease in radioactivity concentration can be observed after attenuation correction.  相似文献   
25.
26.
The Dunning H rat prostate tumor (R3327H) is a widely used experimental model of human prostatic adenocarcinoma (CaP). The Dunning H tumor has been characterized as androgen-sensitive, androgen-receptor (AR) positive, prostate-specific antigen and prostatic acid phosphatase (PAP) positive. To date, the tumor has been maintained by serial passage in vivo because of the lack of an in vitro cell line that retains the characteristics of the in vivo tumor. The objective of the present study was to establish a propagable cell line from R3327H adenocarcinoma that maintained androgen sensitivity and expression of AR, PSA and PAP. Tissue harvested from an in vivo R3327H tumor was dissociated with collagenase and placed into Richter's improved media (with supplements). A cytokeratin-positive epithelial cell line (HUNC- E) and a vimentin-positive stromal cell line (HUNC-S) were generated from the primary culture, subcultured continuously for >300 days, and passaged >50 times. Survival of the HUNC-E cell line in vitro depended on several media supplements, including nicotinamide, insulin, transferrin, selenium and epidermal growth factor (EGF). HUNC-E cells expressed AR and produced PSA and PAP throughout the culture period, as confirmed by immunocytochemistry and Western blot analyses. Addition of 14 nM testosterone (T) or dihydrotestosterone (DHT) to HUNC-E cells, stimulated DNA synthesis as well as anchorage-independent growth and PSA production, which demonstrated the androgen-sensitive nature of the cells in vitro. When HUNC-E and HUNC-S cells were combined in a 3:1 ratio and introduced subcutaneously into syngeneic male hosts, tumors formed in 2/3 animals with an average latency of 7 months. RT-PCR and immunocytochemical characterization of the HUNC cell lines revealed that the cells expressed several growth factors and their cognate receptors, including HGF, TGF-alpha and the TGF-betas, indicating the establishment of potential autocrine loops in the neoplastic cells. The HUNC-E and HUNC-S CaP cell lines, which retain the characteristics of the epithelial and stromal components of the in vivo R3327H tumor, will allow a more thorough and informative molecular and biological analysis of prostatic adenocarcinoma.   相似文献   
27.
Fong  LY; Farber  JL; Magee  PN 《Carcinogenesis》1998,19(9):1591-1596
Previous work has shown that sustained increased and decreased cell proliferation, induced by dietary zinc deficiency and caloric restriction respectively, influence the course of N- nitrosomethylbenzylamine (NMBA)-induced esophageal carcinogenesis in rats. The present study considered whether the increased cell proliferation and esophageal tumor incidence induced by zinc deficiency are reversed upon zinc replenishment. Weanling rats were maintained initially on a deficient diet containing 4 p.p.m. zinc. After 5 weeks, carcinogen-treated animals were given six intragastric doses of NMBA (2 mg/kg twice weekly). Controls were untreated. After the second NMBA dose, the rats were divided into three dietary groups. One group was continued on the deficient diet, while the other two groups were switched to diets containing either 75 or 200 p.p.m. zinc, with half of the members in each group fed ad libitum and half pair-fed with deficient rats. NMBA-untreated controls were similarly replenished. At various time points, esophageal cell proliferation was assessed in five animals from each group by immunohistochemical detection of cells in S phase, with in vivo 5-bromo-2'deoxyuridine labeling. At 11 weeks after the first dose, esophageal tumor incidence was greatly reduced, from 100% in the deficient group to 26 and 14% respectively in the replenished groups fed ad libitum 75 and 200 p.p.m. zinc and to 14 and 11% respectively in the replenished groups pair-fed 75 and 200 p.p.m. zinc. In addition, the number of tumors per esophagus was reduced from 9.93 +/- 4.25 in deficient rats, to a range of 0.11 +/- 0.31-0.30 +/- 0.54 in replenished animals. Following zinc replenishment, esophageal cell proliferation, as measured by labeling index (LI), the number of labeled cells and the total number of cells, was markedly decreased in NMBA-untreated and -treated esophagi as compared with those in corresponding deficient esophagi. Thus, the esophageal cell proliferation induced by zinc deficiency is reversed by zinc replenishment and replenished animals have a markedly lower incidence of esophageal tumors.   相似文献   
28.
目的探讨宫颈液基细胞学及阴道镜检查在北京市社区妇女宫颈病变筛查中的临床意义。方法2006年6月至2007年6月对北京市展览路社区的795位20~54岁有性生活的妇女进行筛查。筛查对象接受妇科检查时,留取宫颈超柏氏薄层液基细胞学检测标本,并对宫颈细胞学异常者行阴道镜检查及活组织检查。结果宫颈细胞学阳性[≥ASC-US(不能明确意义的不典型鳞状细胞)]45例,占5.7%(45/795)。其中ASC-US33例,占73.3%(33/45);低度鳞状上皮内病变8例;高度鳞状上皮内病变3例;不典型腺细胞1例。细胞学阴性750例,占94.3%(750/795)。宫颈细胞学阳性的45例中,5例拒绝行阴道镜检查,占11.1%(5/45)。在行阴道镜活组织病理检查的40例中,慢性宫颈炎11例(27.5%);宫颈湿疣14例(35.0%);宫颈上皮内瘤样病变(CIN)1为7例(17.5%);CIN2为3例(7.5%);CIN3为4例(10.0%);早期浸润癌1例(2.5%)。细胞学阴性的750例中,宫颈湿疣2例(0.3%);CIN1为5例(0.7%);宫颈低级别腺上皮内病变1例(0.1%)。宫颈液基细胞学筛查CIN1及以上宫颈病变和宫颈癌的敏感度71.4%,特异度94.2%,阳性预测值37.5%,阴性预测值99.2%;筛查CIN2及以上宫颈病变和宫颈癌的敏感度100.0%,特异度96.0%,阳性预测值20.5%,阴性预测值100.0%。结论应重视并及时进行北京市社区人群宫颈病变的早期筛查,薄层液基细胞学结合阴道镜活组织检查及病理学检查,对提高早期宫颈癌筛查的准确性效果明显。  相似文献   
29.
30.
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