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   2920030篇
  免费   239250篇
  国内免费   12899篇
耳鼻咽喉   39909篇
儿科学   92227篇
妇产科学   72725篇
基础医学   481281篇
口腔科学   75846篇
临床医学   265475篇
内科学   497455篇
皮肤病学   83103篇
神经病学   248065篇
特种医学   114905篇
外国民族医学   81篇
外科学   459477篇
综合类   88181篇
现状与发展   23篇
一般理论   2097篇
预防医学   249095篇
眼科学   66098篇
药学   195529篇
  22篇
中国医学   8624篇
肿瘤学   131961篇
  2022年   22817篇
  2021年   54711篇
  2020年   34904篇
  2019年   57894篇
  2018年   70431篇
  2017年   53552篇
  2016年   58722篇
  2015年   73280篇
  2014年   107341篇
  2013年   172477篇
  2012年   77912篇
  2011年   76966篇
  2010年   113543篇
  2009年   118231篇
  2008年   63315篇
  2007年   65197篇
  2006年   75954篇
  2005年   71610篇
  2004年   73690篇
  2003年   65039篇
  2002年   55183篇
  2001年   72498篇
  2000年   63979篇
  1999年   70110篇
  1998年   61814篇
  1997年   60323篇
  1996年   58024篇
  1995年   53514篇
  1994年   47529篇
  1993年   44592篇
  1992年   46834篇
  1991年   46104篇
  1990年   43696篇
  1989年   43913篇
  1988年   40762篇
  1987年   39946篇
  1986年   37787篇
  1985年   38753篇
  1984年   38409篇
  1983年   36025篇
  1982年   37895篇
  1981年   36117篇
  1980年   34203篇
  1979年   30624篇
  1978年   29411篇
  1977年   27254篇
  1976年   25417篇
  1975年   24439篇
  1974年   23800篇
  1973年   22759篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Krishna S. Iyer 《Platelets》2020,31(4):474-482
Abstract

Platelets are small, anucleated effector cells that play an important role in linking the hemostatic and inflammatory processes in the body. Platelet function is known to be altered under various inflammatory conditions including aging. A gain in platelet function during aging can increase the risk of thrombotic events, such as stroke and acute myocardial infarction. Anti-platelet therapy is designed to reduce risk of serious cerebrovascular and cardiovascular events, but the adverse consequences of therapy, such as risk for bleeding increases with aging as well. Age-associated comorbidities such as obesity, diabetes, and hyperlipidemia also contribute to increased platelet activity and thus can enhance the risk of thrombosis. Therefore, identification of unique mechanisms of platelet dysfunction in aging and in age-associated comorbidities is warranted to design novel antiplatelet drugs. This review outlines some of the current areas of research on aging-related mechanisms of platelet hyperactivity and addresses the clinical urgency for designing anti-platelet therapies toward novel molecular targets in the aging population.  相似文献   
82.
83.
The purpose of this investigation was to characterize noise levels in spaces designated as “effective quiet” areas on a U.S. Navy aircraft carrier. Noise dosimetry samples were collected in 15 designated spaces, representing 15 noise measurements, while at-sea during airwing carrier qualifications. Equivalent sound level (Leq) measurements were collected during flight operations (Leq (flt ops)), non-flight operations (Leq (non-flt ops)), and over 24-hr periods (Leq (24-hr)). These data were compared to the 70 dBA American Conference of Governmental Industrial Hygienists (ACGIH®) Threshold Limit Value (TLV®) for “effective quiet” areas intended for temporary threshold shift recovery when personnel live and work in a potentially noise hazardous environment for periods greater than 24?hr. The monitored areas were selected based on personnel occupancy/use during off-duty time periods. Areas were classified by either (1) leisure areas that included mess (eating areas), gyms, lounges, an internet cafe, and the fantail social area or (2) berthing (sleeping) areas. The Leq measurements in decibels “A” weighted (dBA) were compared to determine significant differences between Leq (flt ops), Leq (non-flt ops), and Leq (24-hr) and were compared between leisure area and berthing area. Measured noise levels according to time period ranged as follows: (1) Leq (24-hr): 70.8–105.4 dBA; (2) Leq (flt ops): 70–101.2 dBA; and (3) Leq (non-flt ops): 39.4–104.6 dBA. All area measurements over the 24-hr period and during flight operations and 46.7% of the areas during the non-flight operation time period exceeded the “effective quiet” 70 dBA ACGIH TLV. Mean Leqs were 15 dBA higher during flight operations compared to non-flight operations in “effective quiet” areas (p?=?0.001). The Leqs in leisure areas were significantly higher than berthing areas by approximately 21 dBA during non-flight operation periods (p?=?0.001). Results suggest noise levels in “effective quiet” areas frequented by aircraft carrier personnel during off-duty hours when at-sea may inhibit auditory recovery from occupational noise exposures that occur on-duty.  相似文献   
84.
85.
86.
Background: Lay belief systems about the malleability of human attributes have been shown to impact behavior change in multiple domains. Addiction mindset—i.e., beliefs about the permanence (vs. malleability) of addiction — may affect cigarette smokers’ ability to quit, but this has never been examined. Objectives: The aims of the present research were to develop a measure of addiction mindset (study 1) and examine its associations with various psychological aspects of quitting smoking (study 2). Methods: In Study 1, using factor analysis of current smokers’ and nonsmokers’ (n?=?600) responses to 22 items designed to measure addiction mindset, we developed a reliable six-item Addiction Mindset Scale (AMS). In Study 2, adult smokers (n?=?200) completed the AMS, and measures of a number of psychological processes related to smoking. Results: Higher scores on the AMS, indicative of the belief that addiction is malleable (referred to as a growth mindset), were positively and significantly associated with greater motivation to quit, greater commitment to quitting, greater self-efficacy to abstain, less attribution of failure to lack of ability to change addiction, and fewer self-reported barriers to cessation (all p’s < .05). Conclusions: The results of this study show a relationship between the beliefs about the permanence of addiction and psychological processes relevant to quitting smoking. The findings underscore the potential of future research exploring how addiction mindsets relate to successful smoking cessation as well as other types of addictive behavior and how they can be applied to change people’s behavior.  相似文献   
87.
Pharmaceutical Chemistry Journal - An HPLC-MS method for simultaneous quantitative determination of a novel gestagenic pharmaceutical and two of its metabolites in rat and rabbit blood sera was...  相似文献   
88.
89.
90.
To determine percent of patients without malignancy and ≤ 40 years of age with high cumulative radiation doses through recurrent CT exams and assess imaging appropriateness. From the cohort of patients who received cumulative effective dose (CED) of ≥ 100 mSv over a 5-year period, a sub-set was identified with non-malignant disease. The top 50 clinical indications leading to multiple CTs were determined. Clinical decision support (CDS) system scores were analyzed using a widely adopted standard of 1–3 (red) as “not usually appropriate,” 4–6 (yellow) “may or may not be appropriate,” and 7–9 (green) “usually appropriate.” Clinicians reviewed patient records to assess compliance with appropriate use criteria (AUC). 9.6% of patients in our series were with non-malignant conditions and 1.4% with age ≤ 40 years. CDS scores (rounded) were 2% red, 38% yellow, 27% green, and 33% unscored CTs. Clinical society guidelines for CT exams, wherever available, were followed in 87.5 to 100% of cases. AUCs were not available for several clinical indications as also referral guidelines for serial CT imaging. More than half of CT exams were unrelated to follow-up of a primary chronic disease. We are faced with a situation wherein patients in age ≤ 40 years require or are thought to require many CT exams over the course of a few years but the radiation risk creates concern. There is a fair number of conditions for which AUC are not available. Suggested solutions include development of CT scanners with lesser radiation dose and further development of appropriateness criteria.  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