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   2448562篇
  免费   186898篇
  国内免费   7869篇
耳鼻咽喉   34919篇
儿科学   73495篇
妇产科学   63894篇
基础医学   342251篇
口腔科学   68479篇
临床医学   223425篇
内科学   478110篇
皮肤病学   48577篇
神经病学   204637篇
特种医学   98208篇
外国民族医学   938篇
外科学   366281篇
综合类   64168篇
现状与发展   19篇
一般理论   980篇
预防医学   194587篇
眼科学   57157篇
药学   183647篇
  134篇
中国医学   7404篇
肿瘤学   132019篇
  2019年   19997篇
  2018年   26371篇
  2017年   20684篇
  2016年   22470篇
  2015年   25864篇
  2014年   36710篇
  2013年   53427篇
  2012年   72815篇
  2011年   76858篇
  2010年   45252篇
  2009年   42958篇
  2008年   71633篇
  2007年   75976篇
  2006年   76864篇
  2005年   74929篇
  2004年   71258篇
  2003年   68888篇
  2002年   67859篇
  2001年   113378篇
  2000年   117559篇
  1999年   99533篇
  1998年   28729篇
  1997年   26355篇
  1996年   26091篇
  1995年   25199篇
  1994年   23640篇
  1993年   21861篇
  1992年   79721篇
  1991年   76673篇
  1990年   73841篇
  1989年   71057篇
  1988年   66064篇
  1987年   64975篇
  1986年   61494篇
  1985年   58535篇
  1984年   44310篇
  1983年   37732篇
  1982年   22922篇
  1981年   20371篇
  1979年   41361篇
  1978年   29020篇
  1977年   24368篇
  1976年   22843篇
  1975年   23997篇
  1974年   29673篇
  1973年   28064篇
  1972年   26248篇
  1971年   24172篇
  1970年   22761篇
  1969年   21100篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
PURPOSE: This study was designed to assess pelvic bone temperature during typical treatment regimens of transurethral ultrasound thermal ablation of the prostate to establish guidelines for limiting bone heating. METHODS: Treatment with transurethral planar, curvilinear, and sectored tubular applicators was simulated using an acoustic and biothermal pelvic model that accommodates applicator sweeping, boundary temperature control, and changes in perfusion and attenuation with thermal dose to more accurately model ultrasound energy penetration. The effects of various parameters including power and frequency (5-10 MHz) on bone heating were assessed for a range of prostate cross-sections (3-5 cm) and bone distances (1-3 cm). RESULTS: All devices can produce significant bone heating (temperatures >50 degrees C, thermal dose >240 EM(43 degrees C)) without optimization of applied frequency or power for bone <3 cm from the prostate boundary. In small glands ( approximately 3 cm) increasing operating frequency of curvilinear and planar devices can increase bone temperatures, whereas the tubular applicator can be used at 10 MHz to avoid likely bone damage. In larger prostates (4-5 cm wide) increasing frequency reduces bone heating but can substantially increase treatment time. Lowering power can reduce bone temperature but may increase thermal dose by increasing treatment duration. All applicators can be used to treat glands 4-5 cm with limited bone heating by selecting appropriate power and frequency. CONCLUSIONS: Pubic bone heating during ultrasound thermal therapy of the prostate can be substantial in certain situations. Successful realization of this therapy will require patient-specific treatment planning to optimally determine power and frequency in order to minimize bone heating.  相似文献   
992.
OBJECTIVES: To determine maternal responses to detection of a minor structural variant, the choroid plexus cyst (CPC), in their fetus on prenatal ultrasound. STUDY DESIGN: We interviewed 34 pregnant women with an isolated CPC detected on mid-pregnancy ultrasound about their objective experience at diagnosis, emotional response and subsequent reactions. Audiotaped, transcribed responses were evaluated by two independent raters and analyzed qualitatively and quantitatively. RESULTS: All women reported negative emotional responses including shock, distress, fear and decreased attachment, despite counseling by 82% of providers that the CPC was probably benign. Three women underwent amniocentesis purely for reassurance after CPC detection. Most (79%) sought information beyond what their physician provided, frequently on the internet. One half of women reported that intense negative responses were temporary. However, weeks after diagnosis, 62% continued to believe that the CPC presented some danger to their baby. CONCLUSIONS: Detection of CPC prenatally can evoke profound, negative maternal emotional responses despite accurate provider counseling. Practitioners should consider these responses when counseling parents about these and other structural variants of unclear functional significance.  相似文献   
993.
994.
AIM: To undertake a systematic review of the diagnostic performance of clinical examination, sample acquisition and sample analysis in infected foot ulcers in diabetes. METHODS: Nineteen electronic databases plus other sources were searched. To be included, studies had to fulfil the following criteria: (i) compare a method of clinical assessment, sample collection or sample analysis with a reference standard; (ii) recruit diabetic individuals with foot ulcers; (ii) present 2 x 2 diagnostic data. Studies were critically appraised using a 12-item checklist. RESULTS: Three eligible studies were identified, one each on clinical examination, sample collection and sample analysis. For all three, study groups were heterogeneous with respect to wound type and a small proportion of participants had foot ulcers due to diabetes. No studies identified an optimum reference standard. Other methodological problems included non-blind interpretation of tests and the time lag between index and reference tests. Individual signs or symptoms of infection did not prove to be useful tests when assessed against punch biopsy as the reference standard. The wound swab did not perform well when assessed against tissue biopsy. Semiquantitative analysis of wound swab might be a useful alternative to quantitative analysis. The limitations of these findings and their impact on recommendations from relevant clinical guidelines are discussed. CONCLUSION: Given the importance of this topic, it is surprising that only three eligible studies were identified. It was not possible to describe the optimal methods of diagnosing infection in diabetic patients with foot ulceration from the evidence identified in this systematic review.  相似文献   
995.
Early defibrillation along with well performed basic life support (BLS) after cardiac arrest, due to ventricular fibrillation is the gold standard for increasing patients survival. Within Germany there are two standardized schemes for the training of first responders as well as of paramedics, emergency medical technicians etc.; however, the use of public access defibrillation (PAD) is highly variable between localities. Results from the USA as well as from Germany indicate approaches to life-saving issues which need addressing. The paper by Caffrey reveals high regional efficiency for PAD along with BLS, while two German studies show the value of lay individuals in BLS. Zipes (USA) study shows that death due to cardiac arrest occurs at the patient’s home in more than 70%. Two recent, standardized US trials cast doubt on the efficacy of broadly deployed BLS-training programs for lay persons, preferring PAD and BLS training carried out strictly in accordance with the risk-ratio, for instance, of the people near to the first responders. Taking this into account, social insurance for occupational accidents offer qualified first responder training for more than 43 million employees (about half of the Germany population) in more than 3 million companies. It is necessary to find a synthesis between socio-economic demands on the one hand and ethical principles on the other for the emergency medicine network.  相似文献   
996.
997.
998.
AIM: The purpose of this pilot study was to identify the subsurface enamel demineralising potential of two possible acidogenic lactose-based powders and their corresponding generic pump inhalers. METHODS: Ten healthy non-asthmatic adults participated in a 5- leg randomised crossover study including a 10% sucrose control. A twice-daily 400 microg dose of inhaler was applied in vitro to a demineralised enamel slab on the buccal flange of a mandibular removable appliance before in situ placement for 14 days each. Lesion parameters were determined using transverse microradiography and digitised image analysis. RESULTS: Minimal demineralisation occurred with sucrose, both pump and one powder inhaler. The remaining powder was associated with remineralisation (p = 0.29). Overall, mean lesion depth increased (p = 0.12). CONCLUSION: Asthma inhalers failed to demonstrate a significant acidogenic/cariogenic effect.  相似文献   
999.
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