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   30221篇
  免费   2787篇
  国内免费   50篇
耳鼻咽喉   285篇
儿科学   967篇
妇产科学   926篇
基础医学   3993篇
口腔科学   529篇
临床医学   3526篇
内科学   6245篇
皮肤病学   312篇
神经病学   2400篇
特种医学   997篇
外国民族医学   1篇
外科学   4590篇
综合类   680篇
一般理论   54篇
预防医学   3293篇
眼科学   503篇
药学   1953篇
中国医学   24篇
肿瘤学   1780篇
  2023年   213篇
  2022年   360篇
  2021年   858篇
  2020年   473篇
  2019年   694篇
  2018年   782篇
  2017年   598篇
  2016年   589篇
  2015年   712篇
  2014年   1003篇
  2013年   1249篇
  2012年   1856篇
  2011年   2008篇
  2010年   1030篇
  2009年   871篇
  2008年   1527篇
  2007年   1520篇
  2006年   1446篇
  2005年   1410篇
  2004年   1215篇
  2003年   1182篇
  2002年   1081篇
  2001年   654篇
  2000年   674篇
  1999年   594篇
  1998年   302篇
  1997年   253篇
  1996年   263篇
  1995年   231篇
  1994年   192篇
  1993年   201篇
  1992年   471篇
  1991年   510篇
  1990年   469篇
  1989年   436篇
  1988年   372篇
  1987年   396篇
  1986年   363篇
  1985年   353篇
  1984年   309篇
  1983年   255篇
  1982年   172篇
  1981年   159篇
  1979年   202篇
  1978年   159篇
  1977年   165篇
  1974年   195篇
  1973年   175篇
  1972年   139篇
  1970年   140篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
To better understand the potential environmental health risk presented by West Nile virus (WNV)-contaminated feces, we quantified the amount of WNV present in the feces of experimentally infected American crows (Corvus brachyrhynchos) and fish crows (Corvus ossifragus). Peak fecal titers ranged from 10(3.5) to 10(8.8) plaque-forming units (PFU)/g for 10 American crows and from 10(2.3) to 10(6.4) PFU/g for 10 fish crows. The presence of infectious WNV in bird feces indicates a potential for direct transmission of WNV. Thus, handlers of sick or dead birds should take appropriate precautions to avoid exposure to fecal material.  相似文献   
12.
13.
14.
15.
The use of low levels of visible or near infrared light for reducing pain, inflammation and edema, promoting healing of wounds, deeper tissues and nerves, and preventing cell death and tissue damage has been known for over forty years since the invention of lasers. Despite many reports of positive findings from experiments conducted in vitro, in animal models and in randomized controlled clinical trials, LLLT remains controversial in mainstream medicine. The biochemical mechanisms underlying the positive effects are incompletely understood, and the complexity of rationally choosing amongst a large number of illumination parameters such as wavelength, fluence, power density, pulse structure and treatment timing has led to the publication of a number of negative studies as well as many positive ones. A biphasic dose response has been frequently observed where low levels of light have a much better effect on stimulating and repairing tissues than higher levels of light. The so-called Arndt-Schulz curve is frequently used to describe this biphasic dose response. This review will cover the molecular and cellular mechanisms in LLLT, and describe some of our recent results in vitro and in vivo that provide scientific explanations for this biphasic dose response.  相似文献   
16.
Hip fractures among elderly people frequently result in permanent disabilities, nursing home placement, and death. The bulk of hip fracture research focuses on elderly women. Within the Veterans Health Administration (VHA), the majority of patients are men. There are no published national reports on hip fractures with large male samples, or on related inpatient mortality among veterans. This retrospective study of 13,546 veterans with hip fracture discharges from 1998-2002 found unadjusted mortality rates are higher in the VHA, compared with the general population. VHA patients tend to be older men in poor health who stay in the hospital longer Increased knowledge about the risks and outcomes associated with hip fractures in men could lead to improved primary and secondary injury-prevention programs. Rehabilitation nurses in acute care can be catalysts in proactively incorporating protective devices, screening for osteoporosis, and initiating lifestyle changes in their plans of care to optimize outcomes for hip fracture patients.  相似文献   
17.
We conducted a retrospective study of 411 women to determine whether a significant relationship existed between method of infant feeding (breast vs bottle) and postpartum weight loss at 6 weeks and 12 months. In addition to method of infant feeding, the variables parity, gravidity, mode of delivery, maternal age, maternal prepregnancy weight, infant sex, and payment status (whether receiving assistance from the Aid to Dependent Children [ADC] program) were studied in terms of their association with weight loss. In general, no consistent relationship was found between method of infant feeding and postpartum weight loss. However, in the ADC group at 6 weeks and in the non-ADC group at 12 months, nonlactating women had lost more weight than had their lactating counterparts, in spite of the theoretical energy deficiency of breast-feeding women. Women who gained more weight during pregnancy consistently lost more weight following delivery, regardless of their prepregnancy weight. These results indicate that infant feeding method was not related to differences in postpartum weight loss between lactating and nonlactating counterparts.  相似文献   
18.
Smooth muscle cells are one of the most important, if not the most important component of atheromatous plaque. Smooth muscle cells from developing and regenerating arteries, as well as atheromatous plaques, show similar morphological and biochemical characteristics which differ from adult tissue. During primary culture, adult smooth muscle cells alter their morphology to resemble those of the developing, regenerating and atheromatous material. We propose that primary cell culture of smooth muscle cells provides a model for the study of smooth muscle cell changes during atheroma formation.  相似文献   
19.
Morphologic study of the spinal cord of a patient with generalized motor deficits revealed changes in the anterior horns characterized by the selective loss of large motor neurons, gliosis and the abnormal accumulation of 10 nm filaments which appeared as argyrophilic spheroids in the perikarya and axons of motor neurons. The ventral roots were predominantly affected and showed a variable loss of axons. The remaining axons displayed prominent onion-bulb formations, frequent axonal sprouting and occasionally evidence of active demyelination. The coexistence of a demyelinating motor radiculopathy and anterior horn changes simulating those of amyotrophic lateral sclerosis (ALS) may contribute to our understanding of the unresolved question of whether the neuronal perikaryon or its axon is the primary target in the pathogenesis of ALS. These observations also indicate that a rigid separation of pathogenetic mechanisms into neuronopathy, axonopathy and myelinopathy may not be always possible.  相似文献   
20.
A representative sample of emergency food relief (EFR) programs was selected on the basis of a census of 1,488 EFR programs in New York State. The census was a two-stage telephone survey. EFR was provided in every county although there was considerable variation in the amount of EFR per county. The soup kitchen and food pantry components of EFR had to be differentiated. The surveillance system was operational one year after the census began.  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