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   8736篇
  免费   406篇
  国内免费   35篇
耳鼻咽喉   179篇
儿科学   713篇
妇产科学   133篇
基础医学   987篇
口腔科学   170篇
临床医学   619篇
内科学   1633篇
皮肤病学   226篇
神经病学   474篇
特种医学   201篇
外科学   1177篇
综合类   212篇
一般理论   2篇
预防医学   620篇
眼科学   296篇
药学   834篇
中国医学   48篇
肿瘤学   653篇
  2022年   145篇
  2021年   246篇
  2020年   157篇
  2019年   197篇
  2018年   205篇
  2017年   156篇
  2016年   218篇
  2015年   202篇
  2014年   333篇
  2013年   398篇
  2012年   566篇
  2011年   571篇
  2010年   376篇
  2009年   255篇
  2008年   445篇
  2007年   441篇
  2006年   438篇
  2005年   392篇
  2004年   315篇
  2003年   304篇
  2002年   253篇
  2001年   173篇
  2000年   151篇
  1999年   160篇
  1998年   79篇
  1997年   50篇
  1996年   64篇
  1995年   47篇
  1992年   107篇
  1991年   101篇
  1990年   88篇
  1989年   100篇
  1988年   81篇
  1987年   71篇
  1986年   81篇
  1985年   60篇
  1984年   56篇
  1983年   40篇
  1982年   44篇
  1981年   45篇
  1980年   48篇
  1979年   66篇
  1978年   41篇
  1977年   46篇
  1976年   48篇
  1975年   58篇
  1974年   74篇
  1973年   53篇
  1971年   47篇
  1970年   53篇
排序方式: 共有9177条查询结果,搜索用时 15 毫秒
111.
The efficacy of supravital staining in the detection of malignancies in oro and oropharyngeal lesions and its role in the detection of malignant changes in premalignant lesions were studied. This prospective study comprises 90 cases of clinically suspicious lesions and it was done over a period of 3 years. Most of the patients had multiple risk factors for the development of malignancy. All underwent staining with a modified solution of 1% toluidine blue (TB). In our study the overall sensitivity was 97.29% and the specificity was 62.5%.  相似文献   
112.
BACKGROUND: The incidence of gastric neoplasm is increasing in the elderly population. Therefore, a rational method of treatment for gastric cancer in the elderly should be constituted to improve the survival. The purpose of the present study was to clarify whether the patient's age is an independent prognostic factor and to determine clinicopathological characteristics in the elderly. METHODS: Curative resection of gastric cancer was carried out on 601 patients who were 40 years or older. They were divided into the following two groups: younger patients (between 40 and 79 years old) and elderly patients (80 years or older). The clinicopathologic features of these patients were reviewed retrospectively and multivariate analysis was carried out. RESULTS: The distinguishing features of gastric cancer in the elderly patients were intestinal and mixed types of cancer, distal third stomach dominance in the tumour location, advanced stage of disease, and a low rate of extensive lymph node dissection (D3 or more). Regarding the recurrence site, the liver was the dominant site in the elderly group (25.3% in the younger group vs 54.5% in the elderly group). The 10-year disease-free survival rate of the elderly group was 53.2%, which was significantly worse than that (79.9%) of the younger patients (P = 0.0004). In multivariate analysis, an age of > or = 80 years is an independent prognostic factor, as well as stage, depth of tumour invasion, lymph node metastasis, scirrhous carcinoma, and blood transfusion. CONCLUSIONS: Results indicate that gastric cancer in elderly patients has a poorer prognosis than that in younger patients.  相似文献   
113.
PURPOSE: To monitor tumor blood flow noninvasively during photodynamic therapy (PDT) and to correlate flow responses with therapeutic efficacy. EXPERIMENTAL DESIGN: Diffuse correlation spectroscopy (DCS) was used to measure blood flow continuously in radiation-induced fibrosarcoma murine tumors during Photofrin (5 mg/kg)/PDT (75 mW/cm2, 135 J/cm2). Relative blood flow (rBF; i.e., normalized to preillumination values) was compared with tumor perfusion as determined by power Doppler ultrasound and was correlated with treatment durability, defined as the time of tumor growth to a volume of 400 mm3. Broadband diffuse reflectance spectroscopy concurrently quantified tumor hemoglobin oxygen saturation (SO2). RESULTS: DCS and power Doppler ultrasound measured similar flow decreases in animals treated with identical protocols. DCS measurement of rBF during PDT revealed a series of PDT-induced peaks and declines dominated by an initial steep increase (average +/- SE: 168.1 +/- 39.5%) and subsequent decrease (59.2 +/- 29.1%). The duration (interval time; range, 2.2-15.6 minutes) and slope (flow reduction rate; range, 4.4 -45.8% minute(-1)) of the decrease correlated significantly (P = 0.0001 and 0.0002, r2= 0.79 and 0.67, respectively) with treatment durability. A positive, significant (P = 0.016, r2= 0.50) association between interval time and time-to-400 mm3 was also detected in animals with depressed pre-PDT blood flow due to hydralazine administration. At 3 hours after PDT, rBF and SO2 were predictive (P < or = 0.015) of treatment durability. CONCLUSION: These data suggest a role for DCS in real-time monitoring of PDT vascular response as an indicator of treatment efficacy.  相似文献   
114.
The series of vasicine (1) analogues, an alkaloid from Adhatoda vasica Nees., were synthesized with changes in A, B or C rings. Compounds 13-19 were evaluated for in vitro bronchodilatory activity using isolated guinea pig tracheal chain. Compounds 3-8 were also synthesized in good yields using microwave-mediated synthesis under solvent free conditions. Compounds 5 and 8 with seven-member C ring were more active than etofylline and caused 100% relaxation of both the histamine and acetycholine pre-contracted guinea pig tracheal chain. The structure-activity relationship studies showed that the quinazoline and oxo functionalities were essential for activity. The compounds without C ring and instead having aliphatic and phenyl substitutions in B ring showed relaxation against histamine pre-contracted tracheal chain only, 2-methyl substituted analogues, 12 and 13, being most active with 100% relaxation effect.  相似文献   
115.
Candida biofilm resistance.   总被引:2,自引:0,他引:2  
Device-related infections in most nosocomial diseases can be traced to the formation of biofilms (microbial communities encased within polysaccharide-rich extracellular matrix) by pathogens on surfaces of these devices. Candida species are the most common fungi isolated from these infections, and biofilms formed by these fungal organisms are associated with drastically enhanced resistance against most antimicrobial agents. This enhanced resistance contributes to the persistence of this fungus despite antifungal therapy. Candida biofilms exhibit enhanced resistance against most antifungal agents, except echinocandins and lipid formulations of AmB. The expression of drug efflux pumps during the early phase of biofilm formation and alterations in membrane sterol composition contribute to resistance of these biofilms against azoles. Metabolic dormancy and ECM do not appear to contribute to resistance, although in a mixed-species biofilm, ECM does retard the diffusion of drugs across biofilm. These multifactorial mechanisms of resistance in fungal biofilms constitute a broad-spectrum defense that is effective against many types of antifungal agents, and represent a common theme present across microbial biofilms.  相似文献   
116.
117.
BACKGROUND: Detection of gastric cancer in an early stage is important to improve the prognosis of patients with gastric cancer. This study compared the clinicopathologic characteristics and surgical results in patients with asymptomatic gastric cancer detected by a screening program with those of patients with symptomatic cancer. The efficacy of 2 screening methods (barium meal and endoscopy) was also compared. METHODS: The subjects included 196 patients with asymptomatic gastric cancer detected by screening (screening group) and 612 patients with symptomatic gastric cancer (nonscreening group) treated from 1979 to 1997. The screening group was subdivided into the barium meal study group (n = 150) and the endoscopic study group (n = 46). RESULTS: The incidences of early gastric cancer and 5-year survival rates between the screening and nonscreening groups were 77% versus 29% (P <.0001) and 81% versus 44% (P <.0001), respectively. The endoscopic study appeared to be able to detect smaller gastric cancer in an earlier stage compared with the barium meal study, although no statistical differences in survival rate were noted between these 2 screening methods. CONCLUSIONS: Screening plays an important role in detecting gastric cancer in an early stage and in potentially reducing death attributable to gastric cancer. Endoscopic screening is recommended as the best screening method.  相似文献   
118.
This article aims to characterise and localise the glycosyl moieties of teliospore wall of Tilletia indica a quarantined fungal pathogens by biochemical and immunological approaches. Chemical enzyme modifier studies, followed by determination of structural configuration using phase contrast and SEM after periodate treatment, showed antigenic entities are glycoprotein in nature. Further characterisation using sodium dodecyl sulphate-polyacrylamide gel electrophroesis (SDS-PAGE) glycoprotein staining and western blotting using anti-teliospore antibodies showed two common proteins of molecular weight 28 and 40 kDa, which is also suggestive of glycoprotein nature of antigenic entities of teliospore wall. To study the binding patterns and localisation of glycosyl moieties on the teliospore walls, fluorescein isothiocyanate (FITC) labelled lectins [Wheat Germ Agglutinin (WGA) and Concanavilin A (Con A)] and anti-teliospore antibodies were used. The patterns of WGA and anti-teliospore antibodies binding with teliospore wall are almost similar and hence it is quite reasonable to suggest that immunodominant glycosyl entities of teliospore wall are acetylglucosamine in nature.  相似文献   
119.
In the context of infections in the body, those that occur in the gynaecological tract are less common and perhaps less clinically significant compared with other body sites. However, a few infections are important in view of their association with pathological sequelae such as tumour formation or pelvic inflammatory disease complex.This review will discuss some of the most relevant infections, first under histology, which will be further subdivided into locations in the genital tract and then under cytology, which focuses mainly on the infections seen in cervical cytology samples. There will be only brief mention of the less common infections or those that do not produce diagnostic challenges or lead to significant complications.  相似文献   
120.
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