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   4515篇
  免费   342篇
  国内免费   11篇
耳鼻咽喉   51篇
儿科学   145篇
妇产科学   115篇
基础医学   702篇
口腔科学   160篇
临床医学   400篇
内科学   1117篇
皮肤病学   99篇
神经病学   332篇
特种医学   104篇
外科学   429篇
综合类   36篇
预防医学   440篇
眼科学   51篇
药学   243篇
中国医学   18篇
肿瘤学   426篇
  2023年   31篇
  2022年   70篇
  2021年   113篇
  2020年   64篇
  2019年   133篇
  2018年   114篇
  2017年   99篇
  2016年   112篇
  2015年   131篇
  2014年   191篇
  2013年   169篇
  2012年   278篇
  2011年   284篇
  2010年   158篇
  2009年   148篇
  2008年   218篇
  2007年   233篇
  2006年   239篇
  2005年   223篇
  2004年   199篇
  2003年   216篇
  2002年   185篇
  2001年   122篇
  2000年   152篇
  1999年   106篇
  1998年   46篇
  1997年   42篇
  1996年   30篇
  1995年   38篇
  1994年   22篇
  1993年   26篇
  1992年   84篇
  1991年   68篇
  1990年   54篇
  1989年   56篇
  1988年   46篇
  1987年   36篇
  1986年   47篇
  1985年   38篇
  1984年   27篇
  1983年   21篇
  1982年   17篇
  1979年   15篇
  1978年   12篇
  1976年   13篇
  1975年   10篇
  1971年   11篇
  1970年   16篇
  1967年   12篇
  1966年   13篇
排序方式: 共有4868条查询结果,搜索用时 0 毫秒
1.
2.
BACKGROUND: Oral hairy leukoplakia (OHL) may be an indicator of the progression of Human Immunodeficiency Virus (HIV)-induced immuno-depression, and the evaluation of risk factors leading to OHL is important in the management of these HIV-infected patients. However, there are few studies that analyze risk factors leading to OHL in the Brazilian population. The aim of this case-control study is to present data about prevalence rates and risk factors leading to OHL in a sample of HIV-infected adults in Brazil. METHODS: This case-control study included 111 HIV-infected patients treated at a clinic for sexually transmitted diseases and HIV. In the initial examinations with dentists, variables were collected from all patients. Diagnosis of OHL was performed in accordance with the International Classification System and cytological features. The Fisher and the chi-squared tests were used for statistical analysis. The proportional prevalence and odds ratio were estimated. RESULTS: Outcome presented a positive, statistically significant association among the presence of OHL and viral load of 3000 copies/mul or greater (P = 0.0001; odds ratio (OR) = 5.8), presence of oral candidiasis (P = 0.0000; OR = 11.1), previous use of fluconazole (P = 0.0000; OR = 24.6), and use of systemic acyclovir (P = 0.032; OR = 4.3). Antiretroviral medication presented a negative, statistically significant association with the presence of OHL (P = 0.002; OR = 8.4). CONCLUSIONS: Prevalence of OHL was 28.8%. Viral load, oral candidiasis, previous use of fluconazole, and systemic acyclovir were determined to be risk factors for OHL. Antiretroviral medication proved to be protective against the development of OHL.  相似文献   
3.
4.
Microbiology of adult cellulitis   总被引:1,自引:0,他引:1  
Needle aspiration of cellulitis sites is commonly advocated to assist in the identification of causative organisms. Twenty-five nondiabetic, adult patients with a clinical diagnosis of cellulitis had site aspirations and blood cultures obtained before antibiotic therapy was initiated. Site cultures were positive in 6 of 25 patients. Blood cultures were positive in 4 of 25 patients. All organisms except one (Enterobacter agglomerans) were staphylococci or streptococci. The gram-negative bacilli were not believed to be a pathogen based on the patient's prompt response to nafcillin. In adult patients who do not have complications, the use of needle aspiration was not supported. Empiric treatment of cellulitis aimed at gram-positive cocci appears to be sufficient.  相似文献   
5.
The distribution of cholinergic nerve fibres, as well as the characterization of the muscarinic receptors responsible for the contraction, were determined in the detrusor smooth muscle of the sheep. The results obtained demonstrated a rich presence of acetylcholinesterase (AChE)-positive fibres distributed throughout the bladder body forming dense neuromuscular, subepithelial and perivascular plexuses. Furthermore, intramural ganglia containing AChE-positive cell bodies were identified. However, acetylcholine and carbachol induced a dose-dependent contraction of detrusor smooth muscle. The effect observed with carbachol was competitively antagonized by atropine (pA2: 8.94), pirenzepine (pA2: 7.38), AF-DX 116 (pA2: 7.35), 4-DAMP (pA2: 9.26) and hexahydroxiladifenidol (HHSiD) (pA2: 8.49). The pA2 value for pirenzepine is intermediate between M1- and M2-receptors which suggests that this antagonist does not act on M1- or M2-receptors, but that it does on M3-receptors. The pA2 value for AF-DX 116 is consistent with the presence of M2-receptors in this tissue. Moreover, the pA2 values obtained for both 4-DAMP and HHSiD are in agreement with the presence of M3-receptors, due to the lack of effect of pirenzepine on M1-muscarinic receptors. These results indicate the existence of a rich parasympathetic innervation in the sheep detrusor muscle and suggest that its contraction could be mediated by the stimulation of muscarinic receptors belonging to both M3- and M2-subtypes.  相似文献   
6.
In this article we present the tenth case, according to the literature, of adenocarcinoma occurring at a long standing ileostomy originally performed for ulcerative colitis. Study of this and previous cases demonstrates common factors such as a previous history of ulcerative colitis, a long interval until the appearance of symptoms, together with a similar clinical and pathological characterisation with invasion of neighbouring skin layers close to the ileostomy. Several pathogenic hypotheses are considered. We believe that local excision in oder to obtain the diagnosis is a better option than a sampling biopsy and that surgery should include a wide resection of the abdominal wall and intestine in order to comply with therapeutic criteria in malignant disease.  相似文献   
7.
To determine the therapeutic activity on regional myocardial function of nifedipine intravenous administration (0.16 mg/kg) during short term myocardial induced ischemia, we used 6 mongrel dogs anesthetized and intubated those who we have implanted 3 pairs of ultrasonic crystals in the subendocardial layer. Utilizing an open chest canine model we performed total 1 minute and partial 2 minutes 30 seconds alternative obstructions, controlled with electromagnetic flowmeters in the anterior descending (AD) and circumflex (Cx) coronary arteries before and after drug administration. During the 70-80% obstructions we have shown a significant improvement in segment shortening, reduced by ischemia, in the ischemic and peri-ischemic zone. The ischemic markers, per cent increment of end diastolic length (% IEDL) and per cent increment of end systolic length (% IESL), have shown significant improvement during partial obstructions in the ischemic and peri-ischemic zone. After total obstructions the improvement on regional myocardial function is less marked and limited to ischemic zone.  相似文献   
8.
Primary deficiency of surfactant is responsible for the respiratory distress syndrome and concerns premature neonates born before 33 weeks of gestation. However, newborns may develop respiratory disorders related to a secondary deficiency or dysfunction of surfactant. We report the course of three extremely low birth weight premature infants who experienced clinical respiratory decompensation at two weeks and showed a marked improvement after exogenous natural surfactant administration.  相似文献   
9.
The effects of staphylococci-induced experimental wasting disease on the immune response of 1 month old CD1 mice were investigated. Animals were separated into different subgroups in order to study their cellular immune competence. Malnutrition of wasted mice was associated with anorexia, diarrhea and weakness. Footpad-injected splenic cells produced normal graft vs. host (GvH) reactions in the popliteal lymph nodes of F1 hybrids. In other experiments, the SRBC intragastric feeding of wasted mice did not cause a tolerant anti-erythrocyte humoral immune response. Three weeks after the staphylococci injections, convalescent erythrocyte-fed wasted mice exhibited an anti-SRBC PFC production similar to that observed in non-tolerant immunized control healthy mice. In return, healthy SRBC-fed control mice showed the specific attenuation of antibody response characteristics of oral tolerance. Differences were found between the immune competence of the undernourished staphylococci-treated wasted mice and those shown by other authors in protein-depleted mice.  相似文献   
10.
Chronic bronchitis, as defined by the magnitude and duration of sputum production, is a diagnosis that encompasses a variety of patients with physiological abnormalities ranging from mild to severe. The first element of therapy is the cessation of smoking, the single most frequent cause of chronic bronchitis. In assisting patients to stop cigarette abuse, nicotine-containing gum has been useful. Therapy directed at airway narrowing continues to be the most widely prescribed. The use of metered dose inhalers containing either beta-adrenergic stimulants or, more recently, ipratropium bromide, an atropine-like agent, continues to be the mainstream of therapy. Theophylline remains a widely prescribed bronchodilator. The use of corticosteroids remains controversial in the stable patient, but appears to be indicated clearly in the patient with an acute exacerbation. The usefulness of antibiotics in acute exacerbations is still uncertain; further studies are needed. Augmentation of survival by the use of chronic supplemental O2 is now certain; more efficient ways to administer O2 are now available. Finally, pulmonary rehabilitation provides a means of improving quality of life in severely disabled patients.  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