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   1294篇
  免费   55篇
  国内免费   11篇
耳鼻咽喉   10篇
儿科学   35篇
妇产科学   42篇
基础医学   110篇
口腔科学   21篇
临床医学   203篇
内科学   94篇
皮肤病学   21篇
神经病学   108篇
特种医学   35篇
外科学   431篇
综合类   41篇
预防医学   114篇
眼科学   2篇
药学   47篇
中国医学   4篇
肿瘤学   42篇
  2021年   23篇
  2020年   7篇
  2019年   12篇
  2018年   17篇
  2017年   9篇
  2016年   12篇
  2015年   18篇
  2014年   44篇
  2013年   36篇
  2012年   59篇
  2011年   65篇
  2010年   35篇
  2009年   32篇
  2008年   75篇
  2007年   83篇
  2006年   78篇
  2005年   68篇
  2004年   55篇
  2003年   44篇
  2002年   52篇
  2001年   51篇
  2000年   39篇
  1999年   35篇
  1998年   17篇
  1997年   15篇
  1996年   18篇
  1994年   11篇
  1993年   13篇
  1992年   9篇
  1991年   13篇
  1990年   15篇
  1989年   18篇
  1988年   22篇
  1987年   16篇
  1986年   18篇
  1985年   20篇
  1984年   19篇
  1983年   7篇
  1982年   10篇
  1981年   13篇
  1980年   12篇
  1979年   18篇
  1978年   19篇
  1977年   9篇
  1974年   7篇
  1973年   10篇
  1972年   12篇
  1971年   7篇
  1968年   9篇
  1959年   6篇
排序方式: 共有1360条查询结果,搜索用时 0 毫秒
31.
Older adults frequently report use of vitamin and mineral (VM) supplements, although the impact of supplements on dietary adequacy remains largely unknown. The purpose of the current study was to evaluate micronutrient intakes of older adults with emphasis on identifying nutrients most improved by VM supplements, nutrients most likely to remain inadequate, and nutrients most likely consumed in excess. Community-based volunteers were recruited from senior centers and completed a questionnaire querying demographic data, current health status, and VM supplement use. Participants (n = 263) were then contacted by telephone to complete two 24-hour diet recalls and confirm VM supplement use. Dietary adequacy was determined by comparing the ratio of mean dietary intake to the Dietary Reference Intakes (DRI). Dietary consumption was lowest for vitamins D and E, calcium, and magnesium. VM supplementation most improved intakes of vitamins E, D, B6, folic acid, and calcium. Participants were most likely to exceed the Tolerable Upper Limit with supplementation of niacin, folic acid, and vitamin A.  相似文献   
32.
Collaborative efforts among community members, health care professionals, and faith-based institutions can prove valuable in efforts to improve community health. This study used data obtained from before and after health risk assessment surveys to assess participant's knowledge of risk factors leading to chronic diseases among African Americans in an underserved community of Alabama. Data obtained from activity logs and health screening sessions was used to assess effect of knowledge gained on lifestyle practices. The study findings support the need for ongoing population-specific education program development in religious institutions located inside underserved communities.  相似文献   
33.
The aim of this trial was to compare the efficacy of combinationantithrombotic therapy with a prostacyclin-sparing aspirin plusanticoagulation versus conventional aspirin plus anticoagulation,when added to antianginal therapy, in patients with unstableangina or non-Q wave myocardial infarction already being treatedwith aspirin. In a double-blind (for the aspirin) study, 144prior aspirin users were randomized; 72 patients received controiled-release,prostacyclin-sparing aspirin 75 mg daily plus anticoagulation(intravenous heparin followed by warfarin to maintain the internationalnormalized ratio at 2–3), and 72 patients received conventionalaspirin 75 mg daily plus the same anticoagulation. Controlled-releaseaspirin was formulated to preserve endothelial cell prostacyclinsynthesis. Trial therapy was begun by 13.2 ± 12.3 h ofqualifying pain, and continued for 12 weeks. The frequency of recurrent angina with electrocardiographicchanges, myocardial infarction, or death, was analysed by intentionto treat. At 12 weeks, events were  相似文献   
34.
During a multiple-casualty incident, a large casualty caseload adversely affects the quality of trauma care given to individual patients. From a trauma care perspective, the goal of the hospital emergency plan is to provide severely injured patients with a level of care that approximates the care given to similar patients under normal conditions. Therefore, the realistic admitting capacity of the hospital is determined primarily by the number of trauma teams that the hospital can recruit. Effective triage of these casualties is often not straightforward, with high overtriage rates. Simplified triage algorithms may be a practical alternative to more elaborate schemes. The concept of minimal acceptable care is the key to a staged management approach during a mass-casualty incident. Discrete-event computer simulation and war game tabletop exercises for key personnel are 2 new modalities that are supplementing the traditional mock disaster drill as effective planning and training tools.  相似文献   
35.
目的:探讨肺隔离症的手术治疗方法和效果。方法回顾性分析该院在2003年3月-2014年3月间收治的17例肺隔离症患者的临床资料。结果①该组17例患者中,术前确诊者13例;术中确诊4例;②采用肺叶切除术对患者进行治疗,全部痊愈,无1例死亡;③术后并发症的发生率为17.64豫(3/17),经对症处理后均缓解;④术后随访6个月~10年,复查X线胸片和CT,结果显示均正常。结论肺隔离症是临床中比较少见的肺先天性畸形,临床表现无特异性,易发生误诊和漏诊,临床中以肺叶切除术治疗为主,效果良好,值得临床推广。  相似文献   
36.
Repetitive head impact (RHI) exposure in collision sports may contribute to adverse neurological outcomes in former players. In contrast to a concussion, or mild traumatic brain injury, “subconcussive” RHIs represent a more frequent and asymptomatic form of exposure. The neural network‐level signatures characterizing subconcussive RHIs in youth collision‐sport cohorts such as American Football are not known. Here, we used resting‐state functional MRI to examine default mode network (DMN) functional connectivity (FC) following a single football season in youth players (n = 50, ages 8–14) without concussion. Football players demonstrated reduced FC across widespread DMN regions compared with non‐collision sport controls at postseason but not preseason. In a subsample from the original cohort (n = 17), players revealed a negative change in FC between preseason and postseason and a positive and compensatory change in FC during the offseason across the majority of DMN regions. Lastly, significant FC changes, including between preseason and postseason and between in‐ and off‐season, were specific to players at the upper end of the head impact frequency distribution. These findings represent initial evidence of network‐level FC abnormalities following repetitive, non‐concussive RHIs in youth football. Furthermore, the number of subconcussive RHIs proved to be a key factor influencing DMN FC.  相似文献   
37.
38.
Summary The levels of insulin antagonism exhibited by human plasma albumin samples extracted by the alcoholic-trichloroacetic acid (TCA) method were found to vary over a wide range. Similar variations were found in the chlorine contents of these albumin samples, thus indicating a variation in TCA content. Chlorine content correlated with the levels of antagnonism exhibited by the various samples. Both chlorine levels and antagonistic activity were reduced appreciably by chromatography with Dowex 50W ion exchange resin. When Dowex treated (nonantagonistic) albumin was dissolved in water and re-extracted by the TCA-ethanol method, the resulting albumin preparations were high in chlorine content and highly antagonistic toward insulin. Nonantagonistic albumin was rendered antagonistic by the addition of TCA. The levels of antagonism exhibited by the TCA treated albumin preparations correlated with their chlorine contents. It is concluded that at least a portion of the insulin inhibitory effects exhibited by albumin preparations isolated by the TCA-ethanol method is due to TCA which is bound to the protein.  相似文献   
39.
An age‐related “anterior shift” in the distribution of the P3b is often reported. Temporospatial principal component analysis (PCA) was used to investigate the basis of this observation. ERPs were measured in young and old adults during a visual oddball task. PCA revealed two spatially distinct factors in both age groups, identified as the posterior P3b and anterior P3a. Young subjects generated a smaller P3a than P3b, while old subjects generated a P3a that did not differ in amplitude from their P3b. Rather than having a more anteriorly distributed P3b, old subjects produced a large, temporally overlapping P3a. The pattern of the age‐related “anterior shift” in the P3 was similar for target and standard stimuli. The increase in the P3a in elderly adults may not represent a failure to habituate the novelty response, but may reflect greater reliance on executive control operations (P3a) to carry out the categorization/updating process (P3b).  相似文献   
40.
Background: Alcohol consumption is an established risk factor for breast cancer. Yet, the mechanism by which alcohol affects breast cancer development remains unresolved. The transition from the premenopausal to the postmenopausal phase is associated with a drastic reduction in systemic estrogen levels. It is not clear whether the risk of breast cancer attributable to alcohol consumption is modified by the different levels of estrogen found in pre‐ and postmenopausal women. The objective of this study is to determine whether the effects of alcohol on mammary tumor development are dependent on the presence of ovarian estrogen. Methods: As a model of breast cancer, we used mouse mammary tumor virus (MMTV)‐neu transgenic mice that overexpress the human epidermal growth factor receptor 2 (HER2/neu) in the mammary epithelium, resulting in the development of estrogen receptor alpha (ERα)‐negative mammary tumors. The mammary tumorigenesis process in these mice is similar to that of patients with HER2 breast cancer. Nonovariectomized (NOVX) and ovariectomized (OVX) MMTV‐neu mice were exposed to 0, 5, and 20% ethanol in the drinking water. Breast cancer development and progression were determined alongside the effects of alcohol on estrogen availability and signaling. Results: Our data show that 20% alcohol consumption promoted tumor development in MMTV‐neu mice only in the presence of ovarian hormones. Tumor promotion was associated with increased systemic estrogen levels, increased expression of aromatase (the rate‐limiting enzyme in estrogen synthesis), and increased expression of ERα in the tumors of 20% alcohol‐consuming MMTV‐neu mice. Additionally, we show that ovariectomy (removal of the ovaries and ovarian hormone production) blocked the effects of 20% alcohol on tumor development. Conclusions: Our results support the notion that alcohol consumption promotes HER2 breast cancer development via the estrogen signaling pathway. Additionally, they suggest that the effects of alcohol on breast cancer may be prevented by blocking estrogen signaling.  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