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   4762篇
  免费   305篇
  国内免费   2篇
耳鼻咽喉   113篇
儿科学   74篇
妇产科学   70篇
基础医学   615篇
口腔科学   60篇
临床医学   475篇
内科学   1084篇
皮肤病学   181篇
神经病学   514篇
特种医学   163篇
外科学   505篇
综合类   22篇
一般理论   1篇
预防医学   359篇
眼科学   76篇
药学   339篇
中国医学   3篇
肿瘤学   415篇
  2023年   33篇
  2022年   42篇
  2021年   141篇
  2020年   102篇
  2019年   146篇
  2018年   137篇
  2017年   103篇
  2016年   116篇
  2015年   120篇
  2014年   189篇
  2013年   243篇
  2012年   347篇
  2011年   344篇
  2010年   192篇
  2009年   151篇
  2008年   269篇
  2007年   270篇
  2006年   270篇
  2005年   253篇
  2004年   220篇
  2003年   175篇
  2002年   159篇
  2001年   78篇
  2000年   74篇
  1999年   68篇
  1998年   33篇
  1997年   33篇
  1996年   36篇
  1995年   48篇
  1994年   24篇
  1993年   27篇
  1992年   49篇
  1991年   52篇
  1990年   40篇
  1989年   43篇
  1988年   46篇
  1987年   33篇
  1986年   22篇
  1985年   27篇
  1984年   33篇
  1983年   28篇
  1982年   34篇
  1981年   20篇
  1979年   24篇
  1978年   15篇
  1977年   16篇
  1975年   15篇
  1974年   20篇
  1972年   18篇
  1970年   12篇
排序方式: 共有5069条查询结果,搜索用时 15 毫秒
991.
992.
Chronic urticaria is an itching skin disease which persists for more than 6 weeks. Chronic urticaria has great impact on the daily life of the patient, and the fluctuating nature of the symptoms complicates the monitoring and treatment of the disease. Currently, there are no reliable biomarkers to identify and measure disease activity in chronic spontaneous urticaria. Consequently, use of patient‐reported outcomes (PROs) is crucial when evaluating and monitoring different aspects of chronic urticaria such as disease activity/severity, disease control, and quality of life. We present an overview of seven different PROs used in chronic urticaria and highlight their strengths, limitations, and use in clinical practice and research.  相似文献   
993.
994.
995.
996.
Background and PurposeAnterior cruciate ligament injuries are prevalent among the athletic population, imposing a heavy economic burden, and the risk of re-injury. Most current biomechanical screening tasks are performed in the sagittal plane, and there is a need for more screening tools that assess sports specific movements in the frontal plane. The purpose of this study was to determine the reliability of and examine differences between sexes in the performance of the Lateral Bound Test (LBT).Materials/MethodsEach subject performed three trials of a LBT which included jumping laterally from one leg over a hurdle and landing on the opposite leg. Two cameras were placed six feet from the landing marker. Maximum dynamic knee valgus using the frontal plane projection angle and knee flexion angle at initial contact and maximal knee flexion were measured upon landing leg using 2D video analysis software. Additionally, video of 10 individuals’ trials were analyzed twice with one week between the analyses to obtain intra-rater reliability while 12 participants were retested one week later to determine test-retest reliability.ResultsThirty healthy subjects, 16 males, 14 females participated. Intra-rater reliability was determined to be excellent for all variables (ICC>0.96). In contrast, the test-retest reliability had greater disparity. Test-retest reliability ranged from poor (ICC = 0.47) to excellent (ICC > 0.90). Significant differences existed between the sexes, including males being significantly taller, weighing more, and demonstrating greater bilateral dynamic knee valgus (p < 0.05). No significant differences existed between sexes for knee flexion angles.ConclusionThe new LBT had excellent intra-rater reliability for assessing dynamic knee valgus and initial and maximum knee flexion angle when performing a functional movement in the frontal plane. Furthermore, males landed with more dynamic knee valgus than females which is contradictory to what has been observed with functional screening tools performed in the sagittal plane.Level of Evidence3b (reliability study)  相似文献   
997.
ObjectivesSwelling, pain and trismus after the surgical removal of the mandibular third molars are the most common and expected postoperative complications. The aim of this cross-sectional study was to assess the association of those postoperative complications and BMI after surgical removal of the mandibular third molars.Material and methods84 patients who required the surgical removal of their lower third molar were enrolled in this study and were divided into 4 groups dependent on their BMI. Data were tested by one-way analysis of variance (Welch''s ANOVA). The differences were tested by the intragroup using the Games-Howell test.ResultsThe effect of BMI on pain had a statistically significant difference within the first 24 postoperative hours: 4 hours (p=0.014), 6 hours (p=0.034, p=0.049), 12 hours (p= 0.00.P=0.023), and 24 hours (p=0.010). For swelling and trismus in the exception on first postoperative day between underweight and normal weight groups (p=0.026), and underweight and overweight groups (p=0.014) no statistically significant correlation was foundConclusionBMI has an impact on a patient’s early postoperative recovery  相似文献   
998.
OBJECTIVES: The aim of this study was to document the true incidence of post-cesarean surgical site infections (SSI), according to the definition of the US Centers for Disease Control and Prevention (CDC), and to identify independent risk factors for infection. DESIGN: Prospective population-based cohort study in Norway. Setting. Sykehuset Asker og Baerum HF, a secondary community hospital, associated with the University of Oslo (UiO), Norway, accounting for 2,000 deliveries per year. Participants. All cesarean deliveries during a 12-month period from September 2003. Main outcome measures. Rate and risk factors for SSI. RESULTS: The total rate of SSI was 8.9%, with an observation period of 30 days post-operatively, compared to 1.8% registered at hospital discharge. The total response rate was 100%. There was no significant difference in SSI rate in elective or emergency cesarean section (CS), respectively. All SSI were superficial. We found 2 significant independent risk factors: operating time > or =38 min and body mass index (BMI) >30. CONCLUSION: The rate of SSI is underestimated if the observation time is limited to the hospital stay. Operating time exceeding 38 min substantially increases the risk of SSI. The finding of no significant difference in SSI rate between elective and emergency CS should lead to a different approach concerning the use of antibiotics: subgroup at risk (operating time > or =38 min and BMI >30) may benefit from antibiotics in relation to the operation, whether the CS is an emergency or elective operation.  相似文献   
999.
We report on local nowcasting (short-term forecasting) of coronavirus disease (COVID-19) hospitalizations based on syndromic (symptom) data recorded in regular healthcare routines in Östergötland County (population ≈465,000), Sweden, early in the pandemic, when broad laboratory testing was unavailable. Daily nowcasts were supplied to the local healthcare management based on analyses of the time lag between telenursing calls with the chief complaints (cough by adult or fever by adult) and COVID-19 hospitalization. The complaint cough by adult showed satisfactory performance (Pearson correlation coefficient r>0.80; mean absolute percentage error <20%) in nowcasting the incidence of daily COVID-19 hospitalizations 14 days in advance until the incidence decreased to <1.5/100,000 population, whereas the corresponding performance for fever by adult was unsatisfactory. Our results support local nowcasting of hospitalizations on the basis of symptom data recorded in routine healthcare during the initial stage of a pandemic.  相似文献   
1000.
The origin of volatile species such as water in the Earth–Moon system is a subject of intense debate but is obfuscated by the potential for volatile loss during the Giant Impact that resulted in the formation of these bodies. One way to address these topics and place constraints on the temporal evolution of volatile components in planetary bodies is by using the observed decay of 87Rb to 87Sr because Rb is a moderately volatile element, whereas Sr is much more refractory. Here, we show that lunar highland rocks that crystallized ∼4.35 billion years ago exhibit very limited ingrowth of 87Sr, indicating that prior to the Moon-forming impact, the impactor commonly referred to as “Theia” and the proto-Earth both must have already been strongly depleted in volatile elements relative to primitive meteorites. These results imply that 1) the volatile element depletion of the Moon did not arise from the Giant Impact, 2) volatile element distributions on the Moon and Earth were principally inherited from their precursors, 3) both Theia and the proto-Earth probably formed in the inner solar system, and 4) the Giant Impact occurred relatively late in solar system history.

Understanding the formation of the Moon has long been a topic of intense interest, although hard constraints on this event only developed after the Apollo program returned lunar samples to Earth. Based on the thousands of lunar rocks that have been studied to date, arguably one of the most stringent of these constraints is that the Moon is strongly depleted in volatile elements relative to the solar photosphere, primitive meteorites, and Earth. Recognition of such a depletion of volatile elements, combined with the orbital mechanics of the Moon and geochemical evidence that it differentiated from a mostly molten state, led to the now widely accepted “Giant Impact” hypothesis, in which the Moon accreted from a volatile element–depleted debris disk produced by an impact between a Mars-sized body (Theia) and the proto-Earth (1). Yet, the formation of the Moon through such an impact scenario raises questions about the composition of the proto-Earth and Theia and their respective contributions to the makeup and subsequent evolution of the Earth–Moon system. Of particular interest is how and when the Moon and Earth obtained their present allotments of volatile components, including, and most importantly, water. Did the Moon and Earth form with their current allotments of volatile elements, or were these elements lost during the Giant Impact and reintroduced to Earth by later accretion of volatile element–laden materials? Here, we address this issue using the Rb–Sr isotopic systematics of lunar samples to provide time constraints on the history and distribution of volatile elements in the Earth–Moon system.  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