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   4069篇
  免费   364篇
  国内免费   41篇
耳鼻咽喉   15篇
儿科学   62篇
妇产科学   42篇
基础医学   391篇
口腔科学   59篇
临床医学   498篇
内科学   459篇
皮肤病学   35篇
神经病学   389篇
特种医学   60篇
外科学   112篇
综合类   392篇
一般理论   1篇
预防医学   1369篇
眼科学   8篇
药学   427篇
  1篇
中国医学   78篇
肿瘤学   76篇
  2024年   17篇
  2023年   55篇
  2022年   171篇
  2021年   228篇
  2020年   210篇
  2019年   145篇
  2018年   162篇
  2017年   153篇
  2016年   155篇
  2015年   167篇
  2014年   280篇
  2013年   429篇
  2012年   251篇
  2011年   296篇
  2010年   216篇
  2009年   206篇
  2008年   185篇
  2007年   181篇
  2006年   150篇
  2005年   116篇
  2004年   115篇
  2003年   79篇
  2002年   81篇
  2001年   70篇
  2000年   49篇
  1999年   46篇
  1998年   42篇
  1997年   27篇
  1996年   23篇
  1995年   16篇
  1994年   25篇
  1993年   14篇
  1992年   11篇
  1991年   12篇
  1990年   8篇
  1989年   11篇
  1988年   8篇
  1987年   7篇
  1986年   2篇
  1985年   4篇
  1984年   8篇
  1983年   4篇
  1982年   10篇
  1981年   5篇
  1980年   6篇
  1979年   5篇
  1978年   2篇
  1977年   3篇
  1976年   4篇
  1971年   1篇
排序方式: 共有4474条查询结果,搜索用时 15 毫秒
21.
流感病毒感染引起免疫损伤的同时可以激发机体产生免疫应答,在病毒的清除与疾病的恢复及再次感染过程中发挥着有效的防御作用.尽管流感病毒经常发生变异,但自然感染诱导的免疫防御机制仍可提供一定程度的交叉保护作用.这一系列免疫应答的激发及形成包括多种分子及细胞的参与,其发生、发展及转归直接决定着疾病的严重程度及免疫预防的有效性.了解天然免疫应答、粘膜免疫应答及获得性免疫应答的激发与维持可为流感病毒的防治及疫苗的研制提供思路.  相似文献   
22.
Sunbathing and sunscreen use, as well as related intentions, attitudes, beliefs, and knowledge, were assessed in 90 Southern Appalachian undergraduates. A large majority (75%) reported sunbathing, with more than half reporting sun lamp use. A slight majority (56.7%) reported some use of sunscreen. Subjects reporting an intention to tan spent more time sunbathing, both outside and under a sun lamp. Individuals reporting a sun protection intention had lighter tans and spent less time sunbathing. Sunbathing was predicted by perceptions of sunbathing as relaxing, while sun lamp use was predicted by more positive views of suntatns. Sunscreen use was predicted by more positive sun protection attitudes and less negative sunscreen attitudes.  相似文献   
23.
Our knowledge about the kinetics and dynamics of complex pathogen-specific CD8(+) T cell responses and the in vivo development of CD8(+) memory T cells has increased substantially over the past years; in comparison, relatively little is known about the CD4(+) T cell compartment. We monitored and directly compared the phenotypical changes of pathogen (Listeria monocytogenes)-specific CD8(+) and CD4(+) T cell responses under conditions leading to effective and long-lasting protective immunity. We found that the general kinetics of bacteria-specific CD8(+) and CD4(+) T cells during the effector and post-effector phases are synchronized. However, later during the memory phase, CD8(+) and CD4(+) T cell populations differ substantially. Whereas CD8(+) memory T cell populations with immediate effector function are readily detectable in lymphoid and non-lymphoid tissues and remain remarkably stable in size, antigen-specific CD4(+) effector-memory T cells decline continuously in frequency over time. These findings have important implications for the better understanding of the in vivo development of protective immunity towards intracellular pathogens.  相似文献   
24.
Neural transection of the dorsal extrahypothalamic descending afferents by means of an L-shaped Halász knife at the anterior commissure (anterior roof deafferentation. ARD) markedly potentiated the display of lordosis and soliciting behaviors. Bilateral lesions of the ventromedial hypothalamus (VMH) attenuated lordotic activity in the ARD sham females but not in the ARD females. In contrast, the lesions in the pontine central gray concurrently with ARD effectively inhibited the display of lordosis but not soliciting behaviors. These results suggest that the VMH may not be a primary focus of the dorsal extrahypothalamic inhibitory influence on lordosis. The influence of this inhibitory system seems to be dominant in regulating the expression of lordosis behavior, compared to that of the hypothalamic lordosis facilitating system. Furthermore, the dorsal extrahypothalamic inhibitors influence which could be removed by ARD must be modified by the neural mechanism in the lower brain stem in which the pontine central gray may be actively involved.  相似文献   
25.
HCV高变区合成多肽的抗原性研究   总被引:3,自引:0,他引:3  
目的:通过计算机同源模建,寻找丙型肝炎病毒高变区(HCV HVR1)中保护性多肽抗原表位。方法:计算机同源模建,预测多肽的抗原性,然后用淋巴细胞转化的方法验证其抗原性,结果:同源模建与实验结果一致,多肽抗原性有待进一步的提高。结论:同源模建是一种高效寻找具有保护性抗原多肽的经济快速方法。  相似文献   
26.
It is important to develop the HCV vaccines in China, be cause 11% 14% of patients with acute and choric hepati tis in this country are infected by HCV, and most of themare infected with Ⅱ/1b and Ⅲ/2a[1]. There are evi dences to indicate that a high variable region 1 (HVR1)exists in the terminal of E2 protein and contains some lin ear epitopes of B cells. Anti HCV antibodies can protectthe sensitive cells from infection by HCV[2 4]. We in tended to get some evidences for designing so…  相似文献   
27.
Thyroxine levels within chick embryos (Gallus domesticus) and incubation temperature were manipulated late in development in order to determine those events most proximal to the time of hatching that are both necessary and sufficient for the appearance of the hatched state. Events recorded include the time of breathing initiation, changes in breathing rate, time of puncture of the chorioallantoic membrane and changes in rate of loss of yolk sac material. It was found that a certain level of thyroxine is necessary for an animal to hatch, that breathing and puncture of the chorioallantoic membrane are necessary but not sufficient to predict the occurrence of hatching, and that a change in rate of loss of yolk sac material during the last 18 hr prior to hatching is sufficient to predict the occurrence of hatching. The explanatory hypothesis offered is that the endogenous increase in thyroxine levels acting via increased metabolic rates is necessary and sufficient for the animals to hatch.  相似文献   
28.
ContextResearch exists on energy balances (EBs) and eating disorder (ED) risks in physically active populations and occupations by settings, but the EB and ED risk in athletic trainers (ATs) have not been investigated.ObjectiveTo assess ATs'' energy needs, including the macronutrient profile, and examine ED risk and pathogenic behavioral differences between sexes (men, women) and job statuses (part time or full time) and among settings (college or university, high school, nontraditional).DesignCross-sectional study.SettingFree living in job settings.Patients or Other ParticipantsAthletic trainers (n = 46; male part-time graduate assistant ATs = 12, male full-time ATs = 11, female part-time graduate assistant ATs = 11, female full-time ATs = 12) in the southeastern United States.Main Outcome Measure(s)Anthropometric measures (sex, age, height, weight, body composition), demographic characteristics (job status [full- or part-time AT], job setting [college/university, high school, nontraditional], years of AT experience, exercise background, alcohol use), resting metabolic rate, energy intake (EI), total daily energy expenditure (TDEE), EB, exercise energy expenditure, macronutrients (carbohydrates, protein, fats), the Eating Disorder Inventory-3, and the Eating Disorder Inventory-3 Symptom Checklist.ResultsThe majority of participants (84.8%, n = 39) had an ED risk, with 26.1% (n = 12) engaging in at least 1 pathogenic behavior, 50% (n = 23) in 2 pathogenic behaviors, and 10.8% (n = 5) in >2 pathogenic behaviors. Also, 82.6% of ATs (n = 38) presented in negative EB (EI < TDEE). Differences were found in resting metabolic rate for sex and job status (F1,45 = 16.48, P = .001), EI (F1,45 = 12.01, P = .001), TDEE (F1,45 = 40.36, P < .001), and exercise energy expenditure (F1,38 = 5.353, P = .026). No differences were present in EB for sex and job status (F1,45 = 1.751, P = .193); χ2 analysis revealed no significant relationship between ATs'' sex and EB (= 0.0, P = 1.00) and job status and EB ( = 2.42, P = .120). No significant relationship existed between Daily Reference Intakes recommendations for all macronutrients and sex or job status.ConclusionsThese athletic trainers experienced negative EB, similar to other professionals in high-demand occupations. Regardless of sex or job status, ATs had a high ED risk and participated in unhealthy pathogenic behaviors. The physical and mental concerns associated with these findings indicate a need for interventions targeted at ATs'' health behaviors.  相似文献   
29.
Summary Six healthy men aged 25 to 37 walked on a treadmill at work levels of 21 and 41% of their for 25 to 30 min wearing gas protective clothing (GPC) consisting of an impermeable suit with a self-contained breathing apparatus (total weight 25 kg) or shorts (control tests, CT) in a temperate environment (t a 24.3°C ± 1.0°C, rh 30–50%). When the GPC was worn at 21 and 41% , the most prominent increases, compared with the CT, were noted in the heart rate ( ± SE, 120 ± 5 vs 76 ± 3 beats min–1 and 171 ± 5 vs 103 ± 3 beats min–1), mean skin temperature (36.1 ± 0.2 vs 31.3° C ± 0.1°C and 36.9 ± 0.3 vs 30.9°C ± 0.4°C) and sweat rate (473 ± 51 vs 70 ± 23 g m–2 h–1 and 766 ± 81 vs 135 ± 18 g m–2 h–1) indicating a high cardiovascular and thermoregulatory strain, which was not decreased by ventilating the suit with an air flow of 281 min–1 at 41% . The ventilation, oxygen consumption and production of carbon dioxide increased in relation to the extra weight of the GPC, partly dependent on the dynamic work level. It was concluded that the increase in the physiological load caused by the GPC was so high that the work-rest regimens, workers' level of physical fitness, cardiovascular health and heat tolerance should be considered whenever gas protective clothing is used.  相似文献   
30.
BackgroundMusculoskeletal traumas are on the rise in the United States; however, limited studies are available to help trauma providers assess and treat concerns beyond the physical impact. Little is understood about the psychological, social, and spiritual factors that protect patients from adverse effects after a physical trauma or their experiences with each factor afterward.ObjectiveThis systematic review was conducted to investigate and review advancements in research related to risk and resiliency factors experienced by survivors of traumatic musculoskeletal injuries. The use of biopsychosocial-spiritual (BPS–S) framework and resiliency theory guided the analysis.MethodsResearchers reviewed 1003 articles, but only seven met the search criteria. Due to the complexity and uniqueness of traumatic brain injuries, studies on that target population were excluded.ResultsOf the seven articles reviewed, three identified psychological protective factors that protect against negative health outcomes; three identified negative psychological, social, or spiritual outcomes; and none investigated social or spiritual health.ConclusionsThere are significant gaps in the literature surrounding risk and resiliency factors related to the BPS-S health of musculoskeletal injury survivors.  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