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   53189篇
  免费   3691篇
  国内免费   106篇
耳鼻咽喉   397篇
儿科学   1968篇
妇产科学   1866篇
基础医学   6370篇
口腔科学   685篇
临床医学   9123篇
内科学   9604篇
皮肤病学   765篇
神经病学   4935篇
特种医学   953篇
外国民族医学   33篇
外科学   4814篇
综合类   711篇
一般理论   79篇
预防医学   7472篇
眼科学   565篇
药学   2999篇
  1篇
中国医学   91篇
肿瘤学   3555篇
  2023年   313篇
  2022年   441篇
  2021年   1018篇
  2020年   684篇
  2019年   1114篇
  2018年   1268篇
  2017年   884篇
  2016年   995篇
  2015年   1087篇
  2014年   1492篇
  2013年   2490篇
  2012年   3575篇
  2011年   3805篇
  2010年   2027篇
  2009年   1900篇
  2008年   3385篇
  2007年   3866篇
  2006年   3670篇
  2005年   3588篇
  2004年   3450篇
  2003年   3301篇
  2002年   3107篇
  2001年   474篇
  2000年   369篇
  1999年   484篇
  1998年   679篇
  1997年   544篇
  1996年   487篇
  1995年   395篇
  1994年   391篇
  1993年   385篇
  1992年   328篇
  1991年   291篇
  1990年   289篇
  1989年   253篇
  1988年   231篇
  1987年   228篇
  1986年   216篇
  1985年   236篇
  1984年   251篇
  1983年   240篇
  1982年   288篇
  1981年   268篇
  1980年   202篇
  1979年   163篇
  1978年   137篇
  1977年   149篇
  1976年   126篇
  1975年   112篇
  1973年   110篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
Advanced age has been associated with a wide range of defects in both the innate and adaptive immune systems including diminished specific antibody responses that increase the risk of invasive pneumococcal disease (IPD) and limit the effectiveness of vaccines. However, the elderly are a heterogeneous group and measures of overall frailty may be a better indicator of disease susceptibility (or vaccine response) than chronological age alone.  相似文献   
44.
BACKGROUND: Perfusion functional magnetic resonance imaging (fMRI) was used to investigate the effect of genetic variation of the human serotonin transporter (5-HTT) gene (5-HTTLPR, SLC6A4) on resting brain function of healthy individuals. METHODS: Twenty-six healthy subjects, half homozygous for the 5-HTTLPR short allele (s/s group) and half homozygous for the long allele (l/l group), underwent perfusion functional and structural magnetic resonance imaging during a resting state. The two genotype groups had no psychiatric illness and were similar in age, gender, and personality scores. RESULTS: Compared with the l/l group, the s/s group showed significantly increased resting cerebral blood flow (CBF) in the amygdala and decreased CBF in the ventromedial prefrontal cortex. The effect of functional modulation in these regions by 5-HTTLPR genotype cannot be accounted for by variations in brain anatomy, personality, or self-reported mood. CONCLUSIONS: The 5-HTTLPR genotype alters resting brain function in emotion-related regions in healthy individuals, including the amygdala and ventromedial prefrontal cortex. Such alterations suggest a broad role of the 5-HTT gene in brain function that may be associated with the genetic susceptibility for mood disorders such as depression.  相似文献   
45.
46.
Esophageal perforation is associated with a significant risk of morbidity and mortality. We report herein a case of lye-induced esophageal perforation managed successfully by employing endoscopic T-tube placement with a successful outcome.  相似文献   
47.
This article reports the results of semi-structured interviews with substance abuse treatment (SAT) program directors (PDs) regarding the ways SAT is being influenced by managed care (MC), plans for future SAT, and strategies for decreasing costs of care. It compares findings to an earlier survey of 50 SAT PDs.

Interviews were conducted in 20 SAT programs to gather information about treatment delivery since the advent of MC, including PD responsibilities, funding source, treatment intensity, location, duration, and methods of treatment. Open-ended responses were used to gather information about current and future plans in providing SAT, and awareness of new types of treatment being planned by organizations impacted by MC.

PDs reported changes in SAT secondary to MC such as decreased treatment length, limiting of inpatient and outpatient services, and delayed treatment secondary to benefit determination. Political and economic constraints were seen as barriers to providing adequate and effective services. SAT being subsumed by mental health was viewed as problematic along with an emerging split between alcohol abuse and drug treatment. A positive emerging treatment trend was the development of targeted programs for special need groups.

PDs revealed a variety of strategies that have promoted necessary adaptations to economic and political influences within the structure of managed behavioral care. Strategies such as varying treatment length, modality, and subspecialty care reflected necessary adaptations to diverse market needs.

Managed care continues to have a tremendous impact on the delivery of SAT services. While MC has helped to contain costs, negative outcomes are decreased availability of appropriate care and overtaxing of units that have survived MC cut backs. However, special need programs have allowed SAT programs to specialize, expand, and even flourish in today's competitive SAT market. Interviews with PDs reinforced the need for maintaining quality and diversified SAT services in today's MC environment.  相似文献   
48.
Background contextLumbar discectomy is the most common type of back surgery performed in the United States. Outcomes after this procedure can be variable and it appears that Workers' Compensation patients might be at increased risk for poor outcomes.PurposeTo examine long-term multidimensional outcomes of lumbar discectomy within a cohort of Workers' Compensation patients from Utah and identify presurgical biopsychosocial factors related to poor outcomes.Study design/settingA retrospective cohort study consisting of a review of presurgical medical records and assessment of patient outcomes via a telephone survey. Outcomes were assessed at least 2 years postsurgery.Patient sampleA consecutive sample of 271 workers from Utah who underwent lumbar discectomy from 1994 to 1999. A total of 134 patients were surveyed at the time of follow-up.Outcome measuresPatient satisfaction, Roland-Morris Disability Questionnaire, SF-36v2, and Stauffer-Coventry Index.MethodsA retrospective review of presurgical biopsychosocial variables and outcome assessment via telephone survey was conducted.ResultsWork disability rate for the cohort was 12.7% (17/134). Analysis of patient satisfaction, back pain-related dysfunction, and the Short-Form Health Survey-36 subscales indicated approximately 25% of patients experienced poor outcomes. Older age, number of comorbid health conditions, assigned case manager, litigation, and time delay from injury to surgery were consistently statistically significant predictors (p<.05) of poor outcomes.ConclusionsResults of this study suggest that compensated back surgery patients are at greater risk for poor lumbar discectomy outcomes than noncompensation patients. Presurgery correlates of poor outcomes may be useful in identifying high-risk compensation patients.  相似文献   
49.
Immunization with amyloid-β (Aβ) peptide reduces amyloid load in animal studies and in humans; however clinical trials resulted in the development of a pro-inflammatory cellular response to Aβ. Apoptosis has been employed to stimulate humoral and Th2-biased cellular immune responses. Thus, we sought to investigate whether immunization using a DNA vaccine encoding Aβ in conjunction with an attenuated caspase generates therapeutically effective antibodies. Plasmids encoding Aβ and an attenuated caspase were less effective in reducing amyloid pathology than those encoding Aβ alone. Moreover, use of Aβ with an Arctic mutation (E22G) as an immunogen was less effective than wild-type Aβ in terms of improvements in pathology. Low levels of IgG and IgM were generated in response to immunization with a plasmid encoding wild-type Aβ. These antibodies decreased plaque load by as much as 36 ± 8% and insoluble Aβ42 levels by 56 ± 3%. Clearance of Aβ was most effective when antibodies were directed against N-terminal epitopes of Aβ. Moreover, immunization reduced CAA by as much as 69 ± 12% in TgCRND8 mice. Finally, high-molecular-weight oligomers and Aβ trimers were significantly reduced with immunization. Thus, immunization with a plasmid encoding Aβ alone drives an attenuated immune response that is sufficient to clear amyloid pathology in a mouse model of Alzheimer's disease.  相似文献   
50.
OBJECTIVE: The objective of this study was to radiographically quantify bone density and bone height preservation in tooth extraction alveolus filled with xenograft. STUDY DESIGN: The maxillary and mandibular fourth deciduous molars and fourth premolars of 6 minipigs were removed. Randomly, in 3 animals the right side was used as the test side and in the other 3 animals the left side was the test side. Intraoral radiographs were performed to compare the condition at the initial time and 3 months later. Measurements of bone height and bone density were performed using KS300 (Zeiss) software. RESULTS: After 3 months, there was a statistically significant smaller bone height loss for the test group. The test group presented a statistically greater bone density immediately after tooth extraction. However, after 3 months there was no statistically significant difference between the groups. CONCLUSIONS: The results suggest that treatment of postextraction alveolus with xenograft can preserve bone height initially but differences in bone density compared to when no xenograft is used are not sustained.  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