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   3847篇
  免费   228篇
  国内免费   23篇
耳鼻咽喉   52篇
儿科学   109篇
妇产科学   53篇
基础医学   503篇
口腔科学   333篇
临床医学   304篇
内科学   786篇
皮肤病学   69篇
神经病学   211篇
特种医学   296篇
外科学   347篇
综合类   47篇
一般理论   1篇
预防医学   490篇
眼科学   124篇
药学   237篇
中国医学   35篇
肿瘤学   101篇
  2023年   24篇
  2022年   66篇
  2021年   147篇
  2020年   84篇
  2019年   98篇
  2018年   127篇
  2017年   87篇
  2016年   81篇
  2015年   113篇
  2014年   129篇
  2013年   176篇
  2012年   268篇
  2011年   254篇
  2010年   165篇
  2009年   134篇
  2008年   179篇
  2007年   217篇
  2006年   163篇
  2005年   163篇
  2004年   133篇
  2003年   133篇
  2002年   102篇
  2001年   76篇
  2000年   71篇
  1999年   71篇
  1998年   65篇
  1997年   61篇
  1996年   54篇
  1995年   30篇
  1994年   47篇
  1993年   38篇
  1992年   34篇
  1991年   40篇
  1990年   25篇
  1989年   63篇
  1988年   46篇
  1987年   44篇
  1986年   42篇
  1985年   41篇
  1984年   30篇
  1983年   18篇
  1982年   15篇
  1981年   26篇
  1980年   12篇
  1978年   13篇
  1977年   13篇
  1976年   14篇
  1975年   11篇
  1973年   8篇
  1967年   7篇
排序方式: 共有4098条查询结果,搜索用时 15 毫秒
91.
92.
Macrophagic myofasciitis (MMF) is an inflammatory myopathy related to aluminum-containing vaccines. Described in 1998, most cases were reported in adults, with only 22 cases being reported in children. Three children aged between 13 months and 3½ years were investigated in our institution for neuromuscular symptoms. They underwent thorough clinical, familial, and laboratory investigations, electroneuromyography, muscle biopsy with transmission electron microscopy, scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and, in one case, brain magnetic resonance imaging. They had received regular immunizations. Two patients were hypotonic and one presented with myotonia. Muscle biopsy of all patients presented macrophagic infiltrates with intracytoplasmic aluminum content as revealed by SEM/EDS analysis. Their diverse clinical picture does not support a direct relationship between local morphologic findings and systemic symptoms. The atypical clinical presentation of these children may not result from the superposition of MMF upon a background systemic neuromyopathy, suggesting instead that they are two coincident and independent conditions. Although the finding of macrophage infiltrates in muscle tissue is not new, the identification of aluminum content is recent. The use of tissue sections for aluminum detection and mapping by SEM/EDS is conclusive for, diagnosis; it has not been reported previously in a pathology journal, to the authors' knowledge.  相似文献   
93.
Purpose

Regular physical activity is a good strategy to maintain the health of athletes, and prevent pain and decreased joint flexibility during the pandemic. On the other hand, higher sedentary time during the pandemic period can have deleterious effects. The objective of this study was to compare physical activity levels, sedentary time, and sleep parameters during the pre-COVID period and the COVID-19 pandemic period in young badminton athletes.

Methods

Fifteen young badminton athletes were evaluated during a pre-COVID period (July 2019) and during the COVID-19 period (July 2020). Sleep parameters, physical activity level, and sedentary time were measured using a tri-axial accelerometer. Participants wore the accelerometer on their dominant wrist for 7 days consecutively. In addition, the average of each sleep parameter [time in bed and total sleep time in hours per day, sleep efficiency (%), wake after sleep onset (WASO, total per day), and sleep latency (minutes per day)] was reported over the 7-day period.

Results

Athletes presented increased sedentary time (pre-COVID?=?7.0?±?1.1 vs.COVID-19?=?8.9?±?1.9 h/day, p?=?0.004, d?=?1.30) and significant decreases in the total PA observed in counts per day (pre-COVID?=?2,967,064.4?±?671,544.1 vs. COVID-19?=?1,868,210.2?±?449,768.4 counts/day, p?=?0.001, d?=?1.99), time in vigorous PA (pre-COVID?=?7.7?±?0.9 vs. COVID-19?=?6.1?±?1.2 h/day, p?=?0.001, d?=?1.56), and time in moderate-to-vigorous PA (pre-COVID?=?8.1?±?0.9 vs. COVID-19?=?6.5?±?1.3 h/day, p?=?0.001, d?=?1.48). There were no significant differences for time in light and moderate PA or in sleep parameters (p?>?0.05).

Conclusion

Young badminton athletes presented increased sedentary time, and decreased total physical activity, time in MVPA, and time in vigorous activities during the COVID-19 pandemic compared to the pre-COVID period, however, there were no significant differences in sleep parameters.

  相似文献   
94.
Circulating TFH (cTFH) cells express CXCR5, PD-1, and, when activated, ICOS, and release IL-21. According to the production of IFN-γ, IL-4, and IL-17 and expression of FoxP3, these cells are also classified as cTFH1, cTFH2, cTFH17, and cTFR cells, respectively. This CD4+T-cell subset is pivotal to efficient humoral immunity, and pregnancy appears to favor IgG production. Here, not only pregnancy amplified the in vivo production of anti-HBsAg IgG in HBV immunized women, but the frequency of cTFH cells was directly correlated with estradiol levels. In vitro, pregnancy-related dose of 17-β-estradiol (E2) directly increased the percentage of different cTFH subsets. While E2 and progesterone (P4) increased the proportion of differentiated TFH cells derived from naïve CD4+T-cells, only E2 amplified the release of IL-21 in those cell cultures. In addition, E2 and P4 increased the proportion of memory B cells and plasma cells, respectively. In SEB-activated B/TFH cell co-cultures, E2, in the presence of P4, increased the production of total IgG. Finally, among the hormones, P4 was stronger in upregulating the percentage of IL-10+TFR cells. Collectively, our findings suggested that E2 and P4 cooperate in the humoral immune response by favoring the expansion of different cTFH and B cell subsets.  相似文献   
95.
Background: Facing the coronavirus disease 2019 (COVID-19) challenge on a global level, dental care professionals are encouraged to optimize universal precautions and adopt measures that ensure protection against infection by contaminated aerosols and droplets. Although aerosol transmission is possible, direct contact through large droplets is probably responsible for the vast majority of transmissions. Methods: This paper is the second of a series of 3 on the management of COVID-19 in clinical dental care settings and aims to describe the selection and use of personal protection equipment (PPE) by dental care professionals (DCP), with consideration of the level of risk associated with the planned procedures. PPE selection depends directly on the local epidemiological setting, the patient's characteristics, and the level of risk of the planned procedures. The procedures performed in the office environment are classified as low-, moderate-, or high-risk. Moderate risk includes 2 further sublevels associated with the cleaning, disinfection, and sterilization of materials for clinical procedures that do not generate aerosols. The training of DCP on how to properly don (put on) and doff (remove) PPE is as important as choosing the appropriate PPE because it can be associated with a risk of infection. Discussion: When there is limited availability of PPE, measures should be adjusted to the risk associated with the intervention. Assuming that an effective COVID-19 vaccine will be developed, once it becomes widely available for DCP, PPE requirements will likely be different. Conclusion: The proper use of PPE, together with the adoption of other operational procedures, can provide effective protection against microorganisms being transmitted via body fluids or in the air.  相似文献   
96.
The purpose of this study was to investigate the effects of a 6-week aerobic training period on the time to fatigue (t lim) during exercise performed at the maximal lactate steady state (MLSS). Thirteen untrained male subjects (TG; age 22.5 ± 2.4 years, body mass 72.9 ± 6.7 kg and VO2max 44.9 ± 4.8 mL kg?1 min?1) performed a cycle ergometer test until fatigue at the MLSS power output before and after 6 weeks of aerobic training. A group of eight control subjects (CG; age 25.1 ± 2.4 years, body mass 70.1 ± 9.8 kg and VO2max 45.2 ± 4.1 mL kg?1 min?1) also performed the two tests but did not train during the 6-week period. There were no differences between the groups with respect to the VO2max or MLSS power output (MLSSw) before the treatment period. The VO2max and the MLSSw of the TG increased by 11.2 ± 7.2 % (pre-treatment = 44.9 ± 4.8 vs. post-treatment = 49.8 ± 4.5 mL kg?1 min?1) and 14.7 ± 8.9 % (pre-treatment = 150 ± 27 vs. post-treatment = 171 ± 26 W), respectively, after 6 weeks of training. The results of the CG were unchanged. There were no differences in t lim between the groups or within groups before and after training. Six weeks of aerobic training increases MLSSw and VO2max, but it does not alter the t lim at the MLSS.  相似文献   
97.
98.
99.
Ecotoxicology - In order to evaluate the differential absorption and toxicity of arsenate (AsV) and arsenite (AsIII), Lemna valdiviana plants were grown in a nutrient solution and subjected to 0.0...  相似文献   
100.
Based on a literature search undertaken to determine the impacts of past public health crises, and a systematic review of the effects of past economic crises on alcohol consumption, two main scenarios—with opposite predictions regarding the impact of the current COVID‐19 pandemic on the level and patterns of alcohol consumption—are introduced. The first scenario predicts an increase in consumption for some populations, particularly men, due to distress experienced as a result of the pandemic. A second scenario predicts the opposite outcome, a lowered level of consumption, based on the decreased physical and financial availability of alcohol. With the current restrictions on alcohol availability, it is postulated that, for the immediate future, the predominant scenario will likely be the second, while the distress experienced in the first may become more relevant in the medium‐ and longer‐term future. Monitoring consumption levels both during and after the COVID‐19 pandemic will be necessary to better understand the effects of COVID‐19 on different groups, as well as to distinguish them from those arising from existing alcohol control policies.  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