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   4551篇
  免费   304篇
  国内免费   43篇
耳鼻咽喉   39篇
儿科学   197篇
妇产科学   118篇
基础医学   591篇
口腔科学   163篇
临床医学   336篇
内科学   978篇
皮肤病学   76篇
神经病学   383篇
特种医学   104篇
外国民族医学   1篇
外科学   661篇
综合类   105篇
一般理论   2篇
预防医学   348篇
眼科学   137篇
药学   357篇
中国医学   61篇
肿瘤学   241篇
  2024年   5篇
  2023年   74篇
  2022年   67篇
  2021年   222篇
  2020年   172篇
  2019年   217篇
  2018年   234篇
  2017年   185篇
  2016年   210篇
  2015年   214篇
  2014年   275篇
  2013年   323篇
  2012年   481篇
  2011年   436篇
  2010年   258篇
  2009年   203篇
  2008年   247篇
  2007年   245篇
  2006年   215篇
  2005年   139篇
  2004年   123篇
  2003年   104篇
  2002年   92篇
  2001年   18篇
  2000年   14篇
  1999年   26篇
  1998年   15篇
  1997年   8篇
  1996年   11篇
  1995年   7篇
  1994年   7篇
  1993年   5篇
  1992年   6篇
  1991年   5篇
  1990年   3篇
  1989年   4篇
  1988年   4篇
  1987年   2篇
  1986年   3篇
  1985年   4篇
  1984年   2篇
  1983年   1篇
  1982年   1篇
  1981年   2篇
  1979年   1篇
  1976年   1篇
  1973年   1篇
  1971年   2篇
  1969年   3篇
  1968年   1篇
排序方式: 共有4898条查询结果,搜索用时 15 毫秒
1.
2.
3.
Magnetic field generated by neuronal activity could alter magnetic resonance imaging (MRI) signals but detection of such signal is under debate. Previous researches proposed that magnitude signal change is below current detectable level, but phase signal change (PSC) may be measurable with current MRI systems. Optimal imaging parameters like echo time, voxel size and external field direction, could increase the probability of detection of this small signal change. We simulate a voxel of cortical column to determine effect of such parameters on PSC signal. We extended a laminar network model for somatosensory cortex to find neuronal current in each segment of pyramidal neurons (PN). 60,000 PNs of simulated network were positioned randomly in a voxel. Biot–savart law applied to calculate neuronal magnetic field and additional phase. The procedure repeated for eleven neuronal arrangements in the voxel. PSC signal variation with the echo time and voxel size was assessed. The simulated results show that PSC signal increases with echo time, especially 100/80 ms after stimulus for gradient echo/spin echo sequence. It can be up to 0.1 mrad for echo time = 175 ms and voxel size = 1.48 × 1.48 × 2.18 mm3. With echo time less than 25 ms after stimulus, it was just acquired effects of physiological noise on PSC signal. The absolute value of the signal increased with decrease of voxel size, but its components had complex variation. External field orthogonal to local surface of cortex maximizes the signal. Expected PSC signal for tactile detection in the somatosensory cortex increase with echo time and have no oscillation.  相似文献   
4.
5.
Background: There are some unique epidemiological characteristics of esophageal cancer in Iran. The objective of this study was finding the association between tobacco, substance and alcohol using with the risk of esophageal cancer in North Khorasan, Iran.

Methods: This Case-Control study was carried out on 96 patients with esophageal cancer and 187 controls. Controls were matched to cases by age and sex. Data were collected through structured interview. Data were analyzed by using chi-square test, T-test and logistic regression, in Stata software version 12.

Results: Our findings show Hookah smoking [OR = 6.1(CI95%:1.2–13.1)] and opium consumption [OR = 2.1(CI95%:1.2–3.5)] were associated with esophageal cancer. Cigarette and pipe smoking, age of onset of smoking, duration of smoking, number of smoking per day, leaving history of smoking, years of leaving smoking, drug withdrawal, number of times of drug withdrawal, a history of drug relapse, alcohol consumption and alcohol dose–response were not related to esophageal cancer.

Conclusion: According to our results, hookah smoking and opium consumption enhance the risk of esophageal cancer in North Khorasan of Iran. We suggest appropriate planning to prevent the esophageal cancer in this district.  相似文献   

6.
Purpose: Traffic accidents are one of the major health problems in the world, being the first cause of burden of illness and the second leading cause of death in Iran. The Sistan-Baluchestan province is one of the most accidental provinces of Iran with the highest rate of accidents-caused deaths. This study was conducted to determine the risk factors associated with traffic accidents in Zahedan through 2013 to 2016. Methods: This analytical cross-sectional study was carried out on 223 drivers from Zahedan who were traumatized by traffic accident and sent to Zahedan hospitals. The data were obtained through interviews taken by the trained interviewers via refereeing to the medical records and collected in the researcher-made checklist. Census was obtained from the study subjects. For data analysis, independent t-test, one-way ANOVA, Chi-square and logistic regression were used with the Stata software version 11.0. Results: In this study, 223 male subjects with the mean age of (32.54 ± 12.95) years, 39.8% single and 60.2% married, entered for investigation. Most accidents (38.8%) occurred between 12:00 to 17:59. While driving, 47.1% of the study subjects were using cell phones, 89.1% had manual use of mobile phones, 21.9% had a habit of sending short message service (SMS) and 23.4% had sent SMS within 10 min before the accident. The one way analysis of variance showed that the mean age of individuals with marital status, driving experience, education and accident with motorcycle were significantly different (p < 0.05). Also, the multivariate logistic regression test indicated a significant relationship of smoking, ethnicity, insurance and SMS typing while driving with motorcycle accident (p < 0.05). Conclusion: In this study, SMS and smoking while driving had the highest risk among the variables studied in the motorcycle accidents. Therefore, effective education attempting to enhance people''s awareness about the consequences of using cell phone and smoking during driving to reduce traffic accidents seems necessary.  相似文献   
7.
Cancer Chemotherapy and Pharmacology - Despite all advances in the treatment of ovarian cancer (OC), it remains the most lethal gynecological malignancy worldwide. There are growing amounts of...  相似文献   
8.
The World Health Organization has reported an annual global suicide rate of 14.5 per 100,000 people. On the other hand, it is estimated that approximately one‐third of the global population are infected with Toxoplasma gondii (T. gondii) parasite. It is widely assumed that microbial pathogens, such as T. gondii, are probably associated with affective and behavioural modulation. The present article aimed to assess the proposed role of toxoplasmosis in raising the risk of suicidal ideation (SI) and suicide attempts (SA) using the available epidemiological data. Seven major electronic databases and the Internet search engine Google were searched for all the studies published between the 1st of January 1950 and 31st of October 2019. The heterogeneity and the risk of bias within and across studies were assessed. Following data extraction, pooled odds ratios (ORs) with 95% confidence interval (CI) across studies were calculated using the random‐effects models. A total number of 9,696 articles were screened and 27 studies were regarded as eligible in our systematic review (SI with five papers and 22 papers on SA). A significant association was detected between antibodies against T. gondii with TA (ORs = 1.57; 95% confidence interval [CI] 1.23–2.00, p = .000). Exploration of the association between T. gondii and SA yielded a positive effect of seropositivity for IgG antibodies but not IgM. Despite the limited number of studies, a statistical association was detected between suicidal behaviours and infection with latent T. gondii.  相似文献   
9.
Introduction Hypothalamic hamartomas are congenital malformations. Clinically, they can be asymptomatic, but they cause seizures, mental retardation and precocious puberty in many cases. Case report A 20-day-old boy with hypothalamic hamartoma and bilateral anophthalmia was presented. Except those, no other congenital anomaly was detected. Conclusion This is a rare case of hypothalamic hamartoma with bilateral anophthalmia. The mutations at SOX2 has an important role in the developing brain and eyes.  相似文献   
10.

Background  

Cardiovascular disease remains the leading killer of women in most developed areas of the world. Rates of physical inactivity and poor nutrition, which are two of the most important modifiable risk factors for cardiovascular disease in women, are substantial. This study sought to examine the effectiveness of a community-based lifestyle-modification program on increasing women's physical activity in a randomized trial guided by community-based participatory research (CBPR) methods.  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