全文获取类型
收费全文 | 1440025篇 |
免费 | 107142篇 |
国内免费 | 4656篇 |
专业分类
耳鼻咽喉 | 18183篇 |
儿科学 | 46315篇 |
妇产科学 | 38051篇 |
基础医学 | 210844篇 |
口腔科学 | 37984篇 |
临床医学 | 140903篇 |
内科学 | 279934篇 |
皮肤病学 | 28007篇 |
神经病学 | 121992篇 |
特种医学 | 51704篇 |
外国民族医学 | 370篇 |
外科学 | 199171篇 |
综合类 | 30422篇 |
现状与发展 | 2篇 |
一般理论 | 615篇 |
预防医学 | 123902篇 |
眼科学 | 31504篇 |
药学 | 106057篇 |
7篇 | |
中国医学 | 3320篇 |
肿瘤学 | 82536篇 |
出版年
2021年 | 12647篇 |
2019年 | 13306篇 |
2018年 | 18382篇 |
2017年 | 13865篇 |
2016年 | 14998篇 |
2015年 | 17292篇 |
2014年 | 23830篇 |
2013年 | 36716篇 |
2012年 | 50568篇 |
2011年 | 53651篇 |
2010年 | 31054篇 |
2009年 | 28843篇 |
2008年 | 49220篇 |
2007年 | 52145篇 |
2006年 | 52123篇 |
2005年 | 50767篇 |
2004年 | 48340篇 |
2003年 | 46097篇 |
2002年 | 44513篇 |
2001年 | 61876篇 |
2000年 | 63354篇 |
1999年 | 53325篇 |
1998年 | 16038篇 |
1997年 | 14468篇 |
1996年 | 14088篇 |
1995年 | 13433篇 |
1994年 | 12428篇 |
1993年 | 11689篇 |
1992年 | 42201篇 |
1991年 | 41337篇 |
1990年 | 39978篇 |
1989年 | 37867篇 |
1988年 | 35072篇 |
1987年 | 34157篇 |
1986年 | 32610篇 |
1985年 | 31207篇 |
1984年 | 23728篇 |
1983年 | 20263篇 |
1982年 | 12682篇 |
1981年 | 11145篇 |
1979年 | 21179篇 |
1978年 | 15305篇 |
1977年 | 12515篇 |
1976年 | 12233篇 |
1975年 | 12454篇 |
1974年 | 15116篇 |
1973年 | 14716篇 |
1972年 | 13537篇 |
1971年 | 12535篇 |
1970年 | 11605篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
To evaluate use of a digital photostimulable phosphor imaging system in the neonatal nursery, 150 newborns were divided into three groups of 50. In the first two groups, screen-film and computed radiographs of the chest were obtained at the same radiation exposure; in the third group, computed radiographs were obtained with a 50% dose reduction (half-exposure computed radiographs). All images were blindly evaluated by three readers who scored the quality of visualization of the mediastinum, lung, bone, soft tissues, and endotracheal and nasogastric tubes, and also image density. No statistical differences in visualization of tubes existed among the three groups. Visualization of the mediastinum, lung, bones, and soft tissues was statistically significantly better on computed radiographs than on half-exposure computed radiographs; visualization of the lungs, bones, and soft tissues was statistically significantly better on screen-film radiographs than half-exposure computed radiographs. Image density was statistically better on computed and half-exposure computed radiographs than on screen-film radiographs. 相似文献
992.
Sheela R Geraghty Barbara S Davidson Barbara B Warner Amy L Sapsford Jeanne L Ballard Betsy A List Rachel Akers Ardythe L Morrow 《Journal of human lactation》2005,21(1):59-66
Although there are well-established clinical human milk banks in the United States, there are no milk banks specifically intended to foster research on human milk. The authors' goal was to establish a milk bank with a core data set to support exploratory and hypothesis-driven studies on human milk. Donations to the Cincinnati Children's Research Human Milk Bank are accepted within the context of ongoing, hypothesis-driven research or on an ad hoc basis. Donors must give informed consent, and scientists wishing to use the samples must have Institutional review board approval for their use. Development of more research human milk banks can potentially provide resources for multidisciplinary collaboration and advance the study of human milk and lactation. 相似文献
993.
Frank Buntinx Richard Wachana Stefaan Bartholomeeusen Kathleen Sweldens Helena Geys 《The British journal of general practice》2005,55(511):102-107
BACKGROUND: It has been suggested that herpes zoster may be a marker for occult malignancy. AIM: To examine the emergence of a subsequent cancer diagnosis in patients with and without herpes zoster. DESIGN OF STUDY: Retrospective cohort study. SETTING: Results were based on the database of Intego, an ongoing Belgian general practice-based morbidity registry, covering 37 general practitioners and including about 311 000 patient years between the years 1994 and 2000. METHOD: Survival analysis comparing the emergence of malignancy in patients with and without herpes zoster. RESULTS: The number of patients below the age of 65 years with herpes zoster, cancer or both was too low to draw any sensible conclusions. Above the age of 65 years we identified a significant increase of cancer emergence in the whole group and in females (hazard ratio = 2.65, 95% confidence interval = 1.43 to 4.90), but not in males. No difference could be identified in the first year after the herpes zoster infection. CONCLUSION: Our results do not justify extensive testing for cancer in herpes zoster patients. The association we identified, however, leaves open a number of questions with respect to the physiopathology behind it. 相似文献
994.
T. Saarne L. Kaiser H. Grönlund O. Rasool G. Gafvelin M. van Hage-Hamsten 《Clinical and experimental allergy》2005,35(5):657-663
BACKGROUND: Allergen-specific immunotherapy is the only treatment for allergic disease providing long-lasting symptom relief. Currently, it is mainly based on the use of crude allergen extracts. The treatment may be improved by the use of genetically engineered allergens, hypoallergens, aiming at a more effective and safer therapy. OBJECTIVE: The aim of this study was to provide a rational design of hypoallergen candidates for immunotherapy by using structural information and knowledge of B and T cell epitopes of an allergen. METHODS: The three-dimensional structure of the major cat allergen Fel d 1 was systematically altered by duplication of selected T cell epitopes and disruption of disulphide bonds. Seven Fel d 1 derivatives were generated and screened for allergenic reactivity in comparison with recombinant Fel d 1 in competition-ELISA. The allergenicity was further evaluated in basophil activation experiments and T cell reactivity was assessed in a lymphoproliferation assay. RESULTS: Three out of seven Fel d 1 derivatives, with two duplicated T cell epitopes and one or two disulphide bonds disrupted, were carefully evaluated. The three derivatives displayed a strong reduction in allergenicity with 400-900 times lower IgE-binding capacity than recombinant Fel d 1. In addition, they induced a lower degree of basophil activation and similar or stronger T cell proliferation than recombinant Fel d 1. CONCLUSION: By a rational approach, we have constructed three Fel d 1 hypoallergens with reduced IgE-binding capacities and retained T cell reactivities. This strategy may be applied to any well-characterized allergen to improve immunotherapy for allergic patients. 相似文献
995.
A serotonin (5-HT)-mediated phosphoinositide hydrolysis response was characterized in fibroblasts cultured from rabbit choroid plexus. 5-HT elicited a maximum 8-fold increase in [3H]inositol-phosphate ([3H]IP) formation, while the partial agonists, (+)-lysergic acid diethylamide and (−)-1-(4-bromo-2,5-dimethyoxyphenyl)-2-aminopropane caused 2- and 5-fold increases, respectively. Mianserin, ketanserin, and spiperone were equipotent at blocking the 5-HT-mediated response. Thus, agonist and antagonist profiles indicate interactions with 5-HT2 receptors. 相似文献
996.
Short latency auditory nerve and brainstem evoked responses (BAERs) and long latency cortical auditory evoked responses (CAERs) in 75 long-term traumatic brain injury (TBI) cases were compared. CAERs were found to be significantly correlated with clinical disability as measured by the Disability Rating Scale, while BAERs were not. Also, BAER patterns were consistently and significantly less abnormal and less sensitive to overall dysfunction than CAER patterns. Findings support previous observations that BAERs have relatively little utility for evaluating in surviving TBI patients the degree of overall brain impairment. In general, long latency AEP patterns are better able to reflect the extent and severity of brain dysfunction and overall clinical condition than are short latency AEP patterns in long-term severe TBI patients, and these patterns should be obtained routinely in the evaluation of such patients. 相似文献
997.
998.
When blood flow through the internal and external carotid arteries is completely interrupted by ipsilateral common carotid artery occlusion, the arterial orbital circulation may be more compromised than the brain supply. We studied a pure and extreme example of this situation in a patient who presented with acute orbital infarction, but no cerebral ischemia on clinical, CT and single-photon emission computerized tomography (SPECT) grounds. Ipsilateral blindness corresponded to retinal, choroidal and optic nerve infarction. The pattern of ophthalmoplegia, with relative sparing of adduction, was more compatible with a muscle than a nerve dysfunction, but a reactive dilated pupil, corneal anesthesia, and orbital pain suggested that the intraorbital branches of the ocular motor nerves and ophthalmic division of the trigeminal nerve were not spared. In addition, signs of widespread ocular ischemia were present. Sequential examinations documented the evolution pattern over 1 year. The absence of an orbital collateral supply from the contralateral external carotid and muscular cervical arteries systems, which contrasted with an adequate middle cerebral artery supply via the contralateral internal carotid artery, may explain this isolated and complete form of orbital ischemia due to common carotid artery occlusion. 相似文献
999.
1000.