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   8181篇
  免费   647篇
  国内免费   54篇
耳鼻咽喉   116篇
儿科学   308篇
妇产科学   83篇
基础医学   728篇
口腔科学   122篇
临床医学   823篇
内科学   2033篇
皮肤病学   149篇
神经病学   658篇
特种医学   584篇
外科学   1332篇
综合类   129篇
一般理论   4篇
预防医学   317篇
眼科学   283篇
药学   577篇
中国医学   24篇
肿瘤学   612篇
  2024年   12篇
  2023年   100篇
  2022年   138篇
  2021年   273篇
  2020年   211篇
  2019年   221篇
  2018年   314篇
  2017年   245篇
  2016年   270篇
  2015年   248篇
  2014年   406篇
  2013年   477篇
  2012年   593篇
  2011年   644篇
  2010年   391篇
  2009年   399篇
  2008年   440篇
  2007年   478篇
  2006年   415篇
  2005年   367篇
  2004年   314篇
  2003年   335篇
  2002年   241篇
  2001年   96篇
  2000年   56篇
  1999年   72篇
  1998年   126篇
  1997年   130篇
  1996年   102篇
  1995年   92篇
  1994年   71篇
  1993年   68篇
  1992年   50篇
  1991年   33篇
  1990年   46篇
  1989年   73篇
  1988年   45篇
  1987年   38篇
  1986年   28篇
  1985年   23篇
  1984年   21篇
  1983年   11篇
  1982年   16篇
  1981年   17篇
  1980年   17篇
  1979年   11篇
  1978年   11篇
  1977年   14篇
  1976年   14篇
  1971年   10篇
排序方式: 共有8882条查询结果,搜索用时 0 毫秒
991.
Neuroretinitis is one of the atypical presentations of Cat scratch disease (CSD). Fundoscopy showed star pattern macular exudates. CSD should be considered in patients who present with blurry vision and typical fundoscopic findings.  相似文献   
992.

Objective

To describe current clinical quality among the nation''s community health centers and to examine health center characteristics associated with performance excellence.

Data Sources

National data from the 2009 Uniform Data System.

Data Collection/Extraction Methods

Health centers reviewed patient records and reported aggregate data to the Uniform Data System.

Study Design

Six measures were examined: first-trimester prenatal care, childhood immunization completion, Pap tests, low birth weight, controlled hypertension, and controlled diabetes. The top 25 percent performing centers were compared with lower performing (bottom 75 percent) centers on these measures. Logistic regressions were utilized to assess the impact of patient, provider, and institutional characteristics on health center performance.

Principal Findings

Clinical care and outcomes among health centers were generally comparable to national averages. For instance, 67 percent of pregnant patients received timely prenatal care (national = 68 percent), 69 percent of children achieved immunization completion (national = 67 percent), and 63 percent of hypertensive patients had blood pressure under control (national = 48 percent). Depending on the measure, centers with more uninsured patients were less likely to do well, while centers with more physicians and enabling service providers were more likely to do well.

Conclusions

Health centers provide quality care at rates comparable to national averages. Performance may be improved by increasing insurance coverage among patients and increasing the ratios of physicians and enabling service providers to patients.  相似文献   
993.
Tuberculosis, the infection on the verge of eradication once, is now a great threat to mankind. Emergence of MDR and XDR-TB synergised with HIV and other immune-compressive diseases have increased the life threatening capacities of the disease. A small molecule has been identified here, which showed potent anti-tubercular activity. The identified hit compound has also been proved active against nearly 25 clinical isolates comparable with isoniazid.  相似文献   
994.
The nontarget effects, in terms of biochemical changes induced by p-nitrophenol (PNP) in three soil microalgae, Chlorella sp., Chlorococcum sp., and Heterochlamydomonas sp., and the PNP removal efficiency of these isolates, were determined. On exposure to 20?mg?L(-1) PNP, Chlorella sp. showed greater activity of peroxidase, superoxide dismutase, and glutathione reductase as well as high contents of proline and carotenoids. While Heterochlamydomonas sp. exhibited higher levels of catalase and protein, Chlorococcum sp. produced greater amounts of malondialdehyde, a measure of lipid peroxidation, in the presence of PNP. Chlorella sp. tolerated PNP by producing large quantities of antioxidants coupled with less lipid peroxidation, while Chlorococcum sp. was susceptible, as evidenced by low antioxidant production and high lipid peroxidation. During 7-d exposure, Chlorella sp., Heterochlamydomonas sp., and Chlorococcum sp. were able to remove 39, 18, and 4% of 20?mg?L(-1) PNP, respectively. The present results indicate that proline, carotenoids and malondialdehyde are the potential biomarkers for assessing PNP toxicity toward microalgae, and their response could be considered for differentiating tolerant and susceptible strains. Moreover, there is a clear correlation between PNP removal and antioxidant synthesis in microalgae on exposure to the pollutant. Environ. Toxicol. Chem. 2012; 31: 1980-1988. ? 2012 SETAC.  相似文献   
995.
ObjectiveTo assess whether selenium and carboxymethyl-lysine (CML), two biomarkers of oxidative stress, are independent predictors of anemia in older community-dwelling adults.MethodsPlasma levels of selenium, CML, folate, vitamin B12, and testosterone and markers of iron status and inflammation were measured at baseline in 1036 adults at least 65 y old in the Invecchiare in Chianti Study, a population-based cohort study of aging in Tuscany, Italy, and examined in relation to prevalent anemia and incident anemia over 6 y of follow-up.ResultsAt enrollment, 11.6% of participants were anemic. Of 472 participants who were non-anemic at enrollment, 72 (15.3%) developed anemia within 6 y of follow-up. At enrollment, plasma CML in the highest quartile (>425 ng/mL) and plasma selenium in the lowest quartile (<66.6 μg/L) predicted incident anemia (hazard ratio 1.67, 95% confidence interval 1.07–2.59, P = 0.02; hazard ratio 1.55, 95% confidence interval 1.01–2.38, P = 0.05, respectively) in a multivariate Cox proportional hazards model that adjusted for age, education, body mass index, cognition, inflammation, red blood cell distribution width, ferritin, vitamin B12, testosterone, and chronic diseases.ConclusionElevated plasma CML and low plasma selenium are long-term independent predictors of anemia in older community-dwelling adults. These findings support the idea that oxidative stress contributes to the development of anemia.  相似文献   
996.

Background

Medication-overuse headache (MOH) is caused by the regular use of medications to treat headache. There has been a lack of research into awareness of MOH. We distributed an electronic survey to undergraduate students and their contacts via social networking sites. Analgesic use, awareness of MOH, perceived change in behaviour following educational intervention about the risks of MOH and preferred terminology for MOH was evaluated.

Findings

485 respondents completed the questionnaire (41% having received healthcare training). 77% were unaware of the possibility of MOH resulting from regular analgesic use for headache. Following education about MOH, 80% stated they would reduce analgesic consumption or seek medical advice. 83% indicated that over the counter analgesia should carry a warning of MOH. The preferred terminology for MOH was painkiller-induced headache.

Conclusions

This study highlights the lack of awareness of MOH. Improved education about MOH and informative packaging of analgesics, highlighting the risks in preferred lay terminology (i.e. painkiller-induced headache), may reduce this iatrogenic morbidity and warrants further evaluation.  相似文献   
997.
998.
999.
We evaluated the relationship of S1 recorded by phonocardiography at the mitral area with motion of the mitral, tricuspid, and aortic valves, recorded by simultaneous echocardiography in 20 cardiac patients with a normal PR interval. The first major component of S1 coincided with mitral valve closure in 20 of 20 patients (100%) and also with tricuspid valve closure in 14 of 20 patients (70%). The second major component of S1 coincided with aortic valve opening in 20 of 20 patients and also with tricuspid valve closure in six of 20 patients (30%). We conclude that the first major component of S1 coincides with mitral valve closure in all patients but may also coincide with tricuspid valve closure in many patients, and the second major component of S1 coincides with aortic valve opening in all patients but may also coincide with tricuspid valve closure in some patients.  相似文献   
1000.
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