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   971996篇
  免费   69407篇
  国内免费   2531篇
耳鼻咽喉   13345篇
儿科学   30566篇
妇产科学   27208篇
基础医学   136167篇
口腔科学   25848篇
临床医学   82754篇
内科学   198467篇
皮肤病学   20094篇
神经病学   78638篇
特种医学   38902篇
外国民族医学   352篇
外科学   154164篇
综合类   19868篇
一般理论   316篇
预防医学   70366篇
眼科学   21888篇
药学   69077篇
中国医学   1878篇
肿瘤学   54036篇
  2021年   7915篇
  2019年   8319篇
  2018年   11310篇
  2017年   8748篇
  2016年   9365篇
  2015年   10694篇
  2014年   15199篇
  2013年   22801篇
  2012年   31115篇
  2011年   32957篇
  2010年   19654篇
  2009年   18609篇
  2008年   30705篇
  2007年   32429篇
  2006年   32447篇
  2005年   31797篇
  2004年   30248篇
  2003年   29229篇
  2002年   28457篇
  2001年   42291篇
  2000年   43416篇
  1999年   37068篇
  1998年   10723篇
  1997年   9746篇
  1996年   9580篇
  1995年   8891篇
  1994年   8449篇
  1993年   7969篇
  1992年   28747篇
  1991年   27497篇
  1990年   26875篇
  1989年   25799篇
  1988年   23964篇
  1987年   23600篇
  1986年   22627篇
  1985年   21519篇
  1984年   16152篇
  1983年   13793篇
  1982年   8321篇
  1979年   14877篇
  1978年   10440篇
  1977年   8806篇
  1976年   8323篇
  1975年   9115篇
  1974年   10881篇
  1973年   10353篇
  1972年   9820篇
  1971年   9055篇
  1970年   8728篇
  1969年   8124篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
171.
172.
Isotactic polypropylenes (iPP) with different melt flow indexes (MFI) were used to fabricate nanocomposites (NCs) with 10 wt % loadings of multi-wall carbon nanotubes (MWCNTs) using ultrasound-assisted extrusion methods to determine their effect on the morphology, melt flow, and electrical properties of the NCs. Three different types of iPPs were used with MFIs of 2.5, 34 and 1200 g/10 min. Four different NC fabrication methods based on melt extrusion were used. In the first method melt extrusion fabrication without ultrasound assistance was used. In the second and third methods, an ultrasound probe attached to a hot chamber located at the exit of the die was used to subject the sample to fixed frequency and variable frequency, respectively. The fourth method is similar to the first method, with the difference being that the carbon nanotubes were treated in a fluidized air-bed with an ultrasound probe before being used in the fabrication of the NCs with no ultrasound assistance during extrusion. The samples were characterized by MFI, Optical microscopy (OM), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), electrical surface resistivity, and electric charge. MFI decreases in all cases with addition of MWCNTs with the largest decrease observed for samples with the highest MFI. The surface resistivity, which ranged from 1013 to 105 Ω/sq, and electric charge, were observed to depend on the ultrasound-assisted fabrication method as well as on the melt flow index of the iPP. A relationship between agglomerate size and area ratio with electric charge was found. Several trends in the overall data were identified and are discussed in terms of MFI and the different fabrication methods.  相似文献   
173.
174.
175.
176.
177.
Recurrent herpes labialis (RHL) is an incredibly common condition, though the medical literature evaluating pediatric aspects is limited. This paper assesses prevalence and therapeutic studies of pediatric RHL as well as disease complications. A comprehensive literature search of English‐language citations based on PubMed queries of selected terms was performed, with exclusion if methodology was not discussed, or if studies had 10 or fewer patients. RHL prevalence in pediatrics has been assessed by measures of point and periodic prevalence, though methodologic limitations may under‐ or over‐estimate the true prevalence of RHL. Studies have been conducted to evaluate therapeutic safety, tolerability, and efficacy of antivirals in the pediatric population. Pediatric RHL point prevalence ranges from 0.72% to 5.2% depending on the population study and the methodologies used. Pediatric RHL carries a significant public health burden and is often implicated in patients with eczema herpeticum, erythema multiforme, reactive infectious mucositis eruptions, and hypersensitivity reactions. There are few studies that evaluate the rates of occurrence of these sequelae associated with pediatric RHL.  相似文献   
178.
179.
180.
Introduction: This study investigated variables associated with subjective decline in executive function among Veterans of Operations Enduring Freedom, Iraqi Freedom, and New Dawn (OEF/OIF/OND) following a history of blast-related mild traumatic brain injury (mTBI).

Method: Fifty-six male U.S. Veterans (MAge = 35.3 ± 8.8 years) with a history of blast-related mTBI (6.6 ± 3.2 years post injury) completed a battery of self-report questionnaires and neuropsychological measures. Participants rated current and retrospectively estimated pre-mTBI executive function difficulties on the Frontal Systems Behavior Scale (FrSBe). A difference score (post- minus pre-mTBI ratings) was the dependent variable (?FrSBe). Linear regression models examined variables predicting ?FrSBe, including: pre-injury characteristics (education, premorbid intelligence), injury-related characteristics (number of blast exposures, losses of consciousness), post-injury clinical symptoms (PTSD Checklist–Military version; Pittsburgh Sleep Quality Index), and post-injury neuropsychological performances on executive function measures (Trail Making Test Part B; Controlled Oral Word Association Test; Auditory Consonant Trigrams; Wisconsin Card Sorting Test).

Results: While 11% of participants had a clinically elevated pre-injury FrSBe total score, 82% had a clinically elevated post-injury FrSBe total score. Only self-reported PTSD symptom severity independently predicted perceived change in executive function.

Conclusions: Many OEF/OIF/OND Veterans with a history of blast-related mTBI experience subjective decline in executive function following injury. Perceived executive function decline was associated with higher PTSD symptom severity, aligning with previous research associating PTSD with cognitive complaints. Results did not support a correspondence between perceived cognitive change and neuropsychological performances.  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