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   2389篇
  免费   207篇
  国内免费   8篇
耳鼻咽喉   9篇
儿科学   144篇
妇产科学   25篇
基础医学   298篇
口腔科学   40篇
临床医学   174篇
内科学   507篇
皮肤病学   24篇
神经病学   371篇
特种医学   132篇
外科学   263篇
综合类   86篇
预防医学   167篇
眼科学   66篇
药学   87篇
肿瘤学   211篇
  2021年   25篇
  2020年   27篇
  2019年   25篇
  2018年   33篇
  2017年   19篇
  2016年   33篇
  2015年   35篇
  2014年   37篇
  2013年   63篇
  2012年   64篇
  2011年   83篇
  2010年   46篇
  2009年   63篇
  2008年   72篇
  2007年   92篇
  2006年   120篇
  2005年   91篇
  2004年   89篇
  2003年   74篇
  2002年   80篇
  2001年   83篇
  2000年   57篇
  1999年   69篇
  1998年   65篇
  1997年   51篇
  1996年   63篇
  1995年   46篇
  1994年   37篇
  1993年   40篇
  1992年   46篇
  1991年   44篇
  1990年   38篇
  1989年   46篇
  1988年   66篇
  1987年   41篇
  1986年   58篇
  1985年   42篇
  1984年   32篇
  1983年   31篇
  1982年   21篇
  1981年   27篇
  1980年   25篇
  1979年   28篇
  1978年   28篇
  1977年   24篇
  1975年   21篇
  1974年   20篇
  1971年   19篇
  1969年   19篇
  1967年   19篇
排序方式: 共有2604条查询结果,搜索用时 15 毫秒
51.
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   
52.
53.
Purpose: To evaluate factors associated with the development of high myopia (worse than ?6.00 D) over 7 years of follow-up in the COMET cohort. Methods: COMET enrolled 469 ethnically diverse children (6–11 years) with myopia between ?1.25 and ?4.50 D. They were randomized to either progressive addition lenses (PALs) or single vision lenses (SVLs), and followed for 5 years in their original lens assignment and 2 additional years wearing either spectacles (PALs or SVLs) or contact lenses. Refractive error was measured annually by cycloplegic autorefraction and axial length by A-Scan ultrasonography. Myopia for each child was defined as the mean spherical equivalent refractive error (SER) of the 2 eyes. Analyses were based on 7 years of follow-up. Time to high myopia was analyzed by Cox proportional hazard models and linear regression. Parental refraction data were available from 240 COMET subjects. Results: Younger (6–7 years) versus older (11 years) age at baseline was a significant risk factor (adjusted hazard ratio (HR) = 6.6, 95% CI = 3.4, 12.7) for having high myopia within 7 years. More (SER from ?2.26 to ?4.50 D) vs. less (SER from ?1.25 to ?2.25 D) baseline myopia was also a significant risk factor for high myopia at 7 years (adjusted HR = 7.4, 95% CI = 4.4, 12.4). Gender, ethnicity, and treatment assignment were not associated with the risk of high myopia within 7 years. Increased number of myopic parents was associated with a significant risk of high myopia in the children (p = 0.008). Conclusions: Children who developed high myopia during 7 years of follow-up were younger and had more myopia at baseline. They also were more likely to have two myopic parents. These children may be at greater risk for sight-threatening conditions later in life.  相似文献   
54.
Twenty-five evaluable patients with advanced non-squamous carcinoma of the uterine cervix were treated with mitoxantrone 12 mg/m2 every three weeks. All patients had good performance status and measurable disease and only 11 had received prior chemotherapy. One complete and one partial response were noted among 15 patients with no prior chemotherapy while no responses were seen in 11 previously treated patients. The major toxicity was myelosuppression; other toxicity was mild. The median progression-free interval was 2.1 months and median survival 4.3 months. Mitoxantrone displays minimal activity in patients with advanced non-squamous carcinoma of the cervix.  相似文献   
55.
Following the identification of a synergistic antitumor effect in a murine model, the combination of etoposide and vincristine has been explored in the clinic. Etoposide was given at 4 dose levels (250, 500, 750 or 1,000 mg/m2) with each dose given in 3 equal fractions daily for 3 days. The dose of vincristine was fixed (two 0.75 mg infusions over 22 hours each between doses of etoposide). A total of 26 patients were entered into study and 7, 11, 10 and 5 patients were treated at the 250, 500, 750, and 1,000 mg/m2 dose levels, respectively. Myelosuppressioh was the principle side effect and Grade 4 WBC toxicity (<>3) developed in 14%, 27%, 40% and 40%, respectively, of the patients treated at each of these respective dose levels. Life-threatening infections occurred in 0%, 9%, 30% and 60% of the patients at these levels, respectively. Reversal of marrow toxicity was rapid with repeat courses given at 3-week intervals. Non-hematologic toxicity, including neurotoxicity, nausea, vomiting, and mucositis was generally mild when present. Objective responses were observed in 1 patient each with refractory Hodgkin's disease and immunoblastic lymphoma. Prolonged periods of stable disease occurred in 2 patients with adenocarcinoma of the lung and one patient with Hodgkin's disease. The starting dose of etoposide recommended for further trials of this agent in combination with infusion of vincristine is 500 mg/m2 given in fractionated doses; dose escalation should be possible in many patients.  相似文献   
56.
57.
58.
Studies in smoking cessation have generally failed to adequately control for active treatment effects and have assumed that measures of smoking behaviour (i.e., estimated smoking rate, self-monitoring and chemical analysis) are equally reliable measures. Sixty smokers were randomly assigned to one of four different smoking cessation treatment groups: hypnosis, focussed smoking, attention placebo and a waiting list control. Subjects were asked to estimate and monitor their own smoking behaviour. Blood samples were also taken for thiocyanate analysis before treatment. Smoking rates were similarly measured directly, at 3 months and 6 months after treatment. The results indicate that the three measures of smoking behaviour were all highly correlated. No significant differences were found between treatments, directly after treatment or at the 3- and 6-month follow-ups. These results suggest that active treatment effects may not be responsible for behavioural change in a smoking cessation program. The implications of these findings are discussed.  相似文献   
59.
60.
Long-term exposure to the dust of fiber glass used for insulation causes no demonstrable gross or microscopic pulmonary damage. This conclusion is based on the results of a postmortem study of the lungs of 20 fiber glass workers, who had had exposures to the dust of fibrous glass which ranged from slight to severe and for periods which ranged from 16 to 32 years, and a comparison of this study’s results with those obtained in a similar study of the lungs of 26 urban dwellers of both sexes, who presumably had not been exposed occupationally to fibrous glass dust, which showed that the average total amount of dust, the average total number of fibers per gram of dry lung, and the average dimensions of the fibers found in the lungs were not significantly different.  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