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   30783篇
  免费   1625篇
  国内免费   183篇
耳鼻咽喉   218篇
儿科学   738篇
妇产科学   460篇
基础医学   3775篇
口腔科学   752篇
临床医学   2109篇
内科学   7745篇
皮肤病学   530篇
神经病学   2623篇
特种医学   1095篇
外科学   5369篇
综合类   158篇
现状与发展   1篇
一般理论   1篇
预防医学   752篇
眼科学   457篇
药学   2181篇
中国医学   35篇
肿瘤学   3592篇
  2023年   193篇
  2022年   372篇
  2021年   592篇
  2020年   340篇
  2019年   453篇
  2018年   616篇
  2017年   469篇
  2016年   578篇
  2015年   639篇
  2014年   787篇
  2013年   961篇
  2012年   1454篇
  2011年   1602篇
  2010年   965篇
  2009年   815篇
  2008年   1419篇
  2007年   1615篇
  2006年   1545篇
  2005年   1569篇
  2004年   1542篇
  2003年   1416篇
  2002年   1427篇
  2001年   1001篇
  2000年   969篇
  1999年   925篇
  1998年   402篇
  1997年   320篇
  1996年   356篇
  1995年   232篇
  1994年   225篇
  1993年   201篇
  1992年   585篇
  1991年   524篇
  1990年   544篇
  1989年   482篇
  1988年   457篇
  1987年   446篇
  1986年   390篇
  1985年   406篇
  1984年   292篇
  1983年   201篇
  1979年   219篇
  1978年   154篇
  1977年   140篇
  1974年   129篇
  1971年   137篇
  1970年   132篇
  1969年   129篇
  1968年   140篇
  1967年   141篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.

Background

Photosensitizers used for photodynamic therapy (PDT) to treat dermatologic disease are metabolized into mainly protoporphyrin IX (PpIX), which has five absorption wavelength peaks: 410?nm, 510?nm, 545?nm, 580?nm, and 630?nm. Although only red light around 635?nm and blue light around 400?nm are used as light sources for PDT, the efficiency of PDT might be improved by using multiple wavelengths, including those that correspond to the other absorption peaks of PpIX. Furthermore, because the target disease often occurs on the face, a flexible-type light-source unit that can be fitted to the lesion without unnecessarily exposing the mucous membranes, e.g., the eyes, nostrils, and mouth, is preferred.

Objective

We investigated the efficacy of a flexible light-emitting diode (LED) unit that emits multiple wavelengths to improve PDT effects.

Methods

HaCaT cells were incubated with 5-ALA and subsequently irradiated with either a single wavelength or sequentially with two wavelengths. Cell viability and reactive oxygen species were analyzed. Nude mice were implanted with COLO679 cells by subcutaneous injection into the flank. 5-ALA was subcutaneously injected into the tumor. The tumor was irradiated with 50?J/cm2 (day 0) and assessed daily until day 21.

Results

The synergistic PDT effects of dual-wavelength irradiation and reactive oxygen species production were highest with the 405-nm and 505-nm wavelength combination. This dual wavelength combination was also the most effective in vivo.

Conclusion

We could therefore conclude that dual-wavelength PDT is an efficient strategy for improving the therapeutic effects of PDT. Using a flexible LED unit is expected to achieve more uniform irradiation of uneven areas.  相似文献   
2.
3.
4.
5.
6.
A retrospective study of 1058 liver transplant recipients was performed to determine: (i) the incidence, etiology, timing, clinical features and treatment of refractory ascites (RA), (ii) risk factors for RA development, (iii) predictors of RA disappearance, (iv) predictors of survival following RA and (v) the impact of RA on patient survival. Sixty-two patients (5.9%) developed RA and its disappearance occurred in 27/62 cases. Patients having hepatitis C virus (HCV) had a significantly higher hazard rate of developing RA (p < 0.00001). No other baseline characteristic was associated with RA. Cox stepwise regression analysis of the hazard rate of RA disappearance found two significant factors: HCV recurrence as the reason for developing RA implied a poorer outcome (p = 0.006), whereas an unknown reason implied a favorable outcome (p = 0.02). In addition, survival following RA was significantly poorer among patients having bacterial peritonitis or HCV recurrence. Finally, the mortality rate was significantly (nearly 8.6 times) higher in patients following RA development while it was ongoing (p < 0.00001); however, if the RA disappeared, then the additional risk of death also disappeared. This study illustrates the importance of developing an optimal treatment strategy to (i) effectively treat RA if it develops and (ii) prevent hepatitis C recurrence.  相似文献   
7.
BACKGROUND: In patients with chronic kidney disease (CKD), although strong associations have been observed between malnutrition and atherosclerosis, the relationship between serum albumin concentration and angiographic changes of coronary artery disease (CAD) remains poorly explored. The goal of the present study was, in patients with CKD, to clarify the relationship between the angiographic severity of CAD and serum albumin concentration reflecting either inflammation or nutrition or both. METHODS: In this study, 100 end-stage renal disease (ESRD) patients were enrolled, who commenced long-term dialysis therapy at our hospital and underwent coronary angiography within 3 months of the first haemodialysis (HD) session. Mean age was 63+/-11 years, 20% of the subjects were female and 62% had diabetes. Severity of CAD was evaluated in terms of (i) number of vessels exhibiting CAD (>or=75% stenosis) and (ii) Gensini score (GS). Clinical characteristics and laboratory findings were recorded at initiation of long-term HD therapy. We then evaluated a possible association with the presence and degree of CAD. RESULTS: Sixty-four patients exhibited signs of CAD. Forty-one among them (64%) had multivessel disease. On univariate logistic regression analysis, age, diabetes and hypoalbuminaemia were significantly associated with multivessel CAD. Univariate linear regression analysis demonstrated a positive correlation of age and diabetes with GS, and an inverse correlation of BMI and serum albumin level with GS. Stepwise regression analysis showed age and serum albumin level to be independently associated with multivessel CAD and GS. The ROC curves demonstrated best cut-off levels of age and albumin for predicting multivessel CAD to be 70 years and 3.15 g/dl, respectively. CONCLUSION: Hypoalbuminaemia at the initiation of dialysis is an important predictor of advanced CAD, particularly in male and in diabetic patients. It may reflect mainly a state of inflammation. However, malnutrition as a confounding factor cannot be entirely excluded.  相似文献   
8.
Postoperative empyema and aspergillosis were diagnosed in a 66-year-old man. Since non-operative therapy was not effective, we performed surgery. On the 8th postoperative day, a covered Ultraflex expandable stent (Boston Scientific, Galway, Ireland) was implanted to make a one-way airway for blocking a major air leak from a bronchopleural fistula causing respiratory distress. His general condition improved gradually, and he was discharged 30 days after stenting. In conclusion, we used a covered Ultraflex expandable stent to make an airway to block an air leak. This may be a new application for this stent.  相似文献   
9.
Anthocyanins, which are responsible for a variety of bright colors (including red, blue, and purple) in fruits, vegetables, and flowers, are consumed as dietary polyphenols. Anthocyanin-containing fruits are thought to decrease coronary heart disease and are used in anti-diabetic preparations. Diabetes is associated with a variety of cardiovascular complications that may be mediated by endothelial dysfunction, and so this study was designed mainly to characterize the influence of a synthesized anthocyanidin derivative (HK-008) over acetylcholine (ACh)-induced relaxation in mesenteric arterial beds isolated from rats. In a glucose-tolerance test in intact rats, HK-008 (30 mg/kg) reduced the glucose level as effectively as the same dose of glibenclamide. The aortic relaxation induced by pinacidil (an ATP-sensitive potassium channel opener) was greatly inhibited by glibenclamide (10 microM), and also significantly inhibited by HK-008 (10 microM). Interestingly, the ACh-induced relaxation in the perfused, preconstricted mesenteric arterial bed was significantly enhanced by HK-008 (10 microM), and this enhancement was significantly attenuated by indomethacin (10 microM). The ACh-induced mesenteric relaxation was impaired by an increase in oxidative stress, viz. superoxide-generating treatment [xanthine oxidase (XO; 0.1 U/ml) plus hypoxanthine (HX; 10 microM)]. However, this impairment was strongly suppressed by HK-008 (10 microM). These results suggest that HK-008 increases endothelium-induced relaxation by suppressing oxidative stress or modulating prostanoids signaling. This compound may therefore be useful against certain cardiovascular disorders.  相似文献   
10.
Factors associated with levels of physical activity at work and during leisure time were analyzed among 577 subjects who had been selected as population controls for a case-control study by random selection from telephone directories. The intensity of physical activity at work was inversely associated with body mass index, the proportion of professionals & managers, consumption of western style breakfast, coffee, butter/margarine, and whisky; and positively associated with rice intake. Frequency of physical activities during leisure time was positively associated with consumption of vegetables, fruits, mushrooms, milk, cheese and coffee, and moderation in eating; and inversely associated with rice intake and the prevalence of gastrointestinal symptoms and medication. The association of physical activity with these factors should be considered in studying its relationship to disease risk.  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