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   74583篇
  免费   41226篇
  国内免费   2篇
耳鼻咽喉   1478篇
儿科学   4184篇
妇产科学   497篇
基础医学   15232篇
口腔科学   5028篇
临床医学   12161篇
内科学   22469篇
皮肤病学   7429篇
神经病学   13105篇
特种医学   2132篇
外科学   13492篇
综合类   7篇
一般理论   22篇
预防医学   4050篇
眼科学   1216篇
药学   5410篇
中国医学   1007篇
肿瘤学   6892篇
  2023年   22篇
  2022年   29篇
  2021年   1226篇
  2020年   5022篇
  2019年   10783篇
  2018年   10030篇
  2017年   11404篇
  2016年   12045篇
  2015年   11874篇
  2014年   11747篇
  2013年   12204篇
  2012年   3926篇
  2011年   3850篇
  2010年   8814篇
  2009年   5185篇
  2008年   1887篇
  2007年   731篇
  2006年   775篇
  2005年   562篇
  2004年   586篇
  2003年   587篇
  2002年   687篇
  2001年   743篇
  2000年   668篇
  1999年   239篇
  1998年   20篇
  1997年   11篇
  1996年   16篇
  1995年   16篇
  1994年   12篇
  1993年   11篇
  1992年   12篇
  1991年   8篇
  1990年   7篇
  1989年   5篇
  1988年   2篇
  1987年   9篇
  1986年   2篇
  1985年   5篇
  1983年   4篇
  1982年   3篇
  1981年   3篇
  1978年   2篇
  1977年   8篇
  1976年   4篇
  1974年   3篇
  1973年   2篇
  1972年   2篇
  1970年   2篇
  1966年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
To address knowledge gaps about Turner syndrome (TS) associated disease mechanisms, the Turner Syndrome Society of the United States created the Turner Syndrome Research Registry (TSRR), a patient‐powered registry for girls and women with TS. More than 600 participants, parents or guardians completed a 33‐item foundational survey that included questions about demographics, medical conditions, psychological conditions, sexuality, hormonal therapy, patient and provider knowledge about TS, and patient satisfaction. The TSRR platform is engineered to allow individuals living with rare conditions and investigators to work side‐by‐side. The purpose of this article is to introduce the concept, architecture, and currently available content of the TSRR, in anticipation of inviting proposals to utilize registry resources.  相似文献   
102.
Summary: The latent thermal cationic initiators, benzyl‐2,5‐dimethylpyrazinium hexafluoroantimonate (BDPH) and benzyl‐2‐ethylpyrazinium hexafluoroantimonate (BEPH), were synthesized to investigate the effect of substituted alkyl groups on cure and dynamic mechanical behaviors of difunctional epoxy system. The cure temperature and activation energy of the diglycidyl ether of bisphenol A (DGEBA)/BDPH were higher than those of the DGEBA/BEPH, resulting from the steric hindrance of the substituted groups. The cross‐linking density of the DGEBA/BDPH was higher than that of the DGEBA/BEPH, whereas the Tg's of both specimens are similar. This may be explained by the free volume and the intermolecular hydrogen bonding induced by the hydrogen of the substituted methyl groups. Consequently, the position and number of the substituted groups of the latent thermal initiator were very important in the control of the latent thermal and dynamic mechanical behaviors of the epoxy resin.

Dynamic DSC curves of DGEBA cured by each initiator.  相似文献   

103.
This study develops an explanatory framework for fear of neighborhood crime based on respondents' social context and local rates of assault injuries. Rates of assault injuries within zip codes are based on hospital discharge records. We find that only four variables have a significant unique contribution to fear of crime: respondent's sex, perceptions of neighborhood social capital, and the rates of struck by/against assault injuries for the 10–24 and 50+ age groups. We also find that the perception of neighborhood social capital moderates the impact of assault injury rates on fear of crime; those who perceive a high level of neighborhood social capital exhibit less sensitivity to assault injury rates. We include a map of assault injury rates and fear of crime by ZIP Code and describe the community context related to our results. © 2007 Wiley Periodicals, Inc. J Comm Psychol 35: 483–498, 2007.  相似文献   
104.
Chickens have two major regions encoding major histocompatibility complex (MHC) class Iα genes and MHC class IIß genes, the serological and functional B‐system and the Rfp‐Y‐system. Recently, they have been shown to assort in a genetically independent way although still located on the same microchromosome. Moreover, the monomorphic MHC class IIα gene maps at a third locus located 5 c m from the nearest class IIß genes, located in the B‐system ( Kaufman et al., 1995 ). A pedigree family was studied in three generations in order to assign MHC class IIß restriction fragments observed in Southern blot analyses to either the B‐system, the Rfp‐Y‐system or the B‐Lα locus. In this study, we demonstrate by classical genetic testing of chickens within this fully pedigreed family the existence of an MHC class II‐like polymorphic restriction fragment that segregates independently of the B‐system, the Rfp‐Y‐system and of the B‐Lα locus.  相似文献   
105.
106.
Summary: In the present contribution, the electrostatic spinning or electrospinning technique was used to produce ultra‐fine polyamide‐6 (PA‐6) fibers. The effects of solution conditions on the morphological appearance and the average diameter of as‐spun fibers were investigated by optical scanning (OS) and scanning electron microscopy (SEM) techniques. It was shown that the solution properties (i.e. viscosity, surface tension and conductivity) were important factors characterizing the morphology of the fibers obtained. Among these three properties, solution viscosity was found to have the greatest effect. Solutions with high enough viscosities (viz. solutions at high concentrations) were necessary to produce fibers without beads. At a given concentration, fibers obtained from PA‐6 of higher molecular weights appeared to be larger in diameter, but it was observed that the average diameters of the fibers from PA‐6 of different molecular weights had a common relationship with the solution viscosities which could be approximated by an exponential growth equation. Raising the temperature of the solution during spinning resulted in the reduction of the fiber diameters with higher deposition rate, while mixing m‐cresol with formic acid to serve as a mixed solvent for PA‐6 caused the solutions to have higher viscosities which resulted in larger fiber diameters. Lastly, the addition of some inorganic salts resulted in an increase in the solution conductivity, which caused the fiber diameters to increase due to the large increase in the mass flow.

Average diameter of as‐spun fibers plotted as a function of the viscosity of the solutions.  相似文献   

107.
Tumor growths, migraine headaches, and other health‐related complications reported in patients with neurofibromatosis type 1 (NF1) are often associated with pain. Thus, this study sought to describe and quantify the pain experience in children and young adults with NF1. Surveys were administered to 49 participants (28 children and 21 adults), ages 8 through 40 years. The survey included the Numeric Rating Scale 11 (NRS11) to assess pain intensity and the Patient Reported Outcomes Measurement Information System (PROMIS) to assess pain interference. A supplemental survey was created to measure pain frequency, chronicity, quality, and location. Results suggest pain is not only present in 55% of the cohort, but that it can begin at early ages. Pain was chronic in 35% of participants, with 41% reporting the use of medication to manage pain symptoms. Common sources of pain included migraine headaches and NF‐related tumors. Pain was described as having neuropathic features (i.e., burning, tingling, numbness, or itching), and was localized to the head, back, and extremities. Further, subsets of participants reported moderate‐to‐severe pain intensity, high frequency of pain, and interference of pain in daily activities. Continued investigation of the pain experience in a multisystem disorder, such as NF1, remains essential to providing guidance in the setting of complex pain management.  相似文献   
108.
109.
Summary: The nature of the pH dependent collapse of poly(methacrylic acid) (PMAA) hydrogels is investigated using recent 1H solid‐state NMR methods. In aqueous solution, PMAA changes from an expanded conformation at high pHs to a compact contracted form at low pHs, where hydrogen bonds play a central role. In solid‐state 1H NMR spectra, recorded under fast magic angle spinning (MAS), dried PMAA samples previously collapsed at low pHs show characteristic signals in the spectral region of the carboxylic acid protons. With the aid of 2D 1H‐1H double‐quantum (DQ) MAS NMR spectra, three signals can be distinguished at 8, 10.5 and 12.5 ppm, which are attributed to free carboxylic groups and two different types of hydrogen bonded forms, respectively. The 12.5 ppm signal arises from the hydrogen bond with the shortest H? H distance, corresponding to the form that is most stable with respect to increasing temperature and pH. The weaker hydrogen‐bonded form (with a signal at 10.5 ppm) requires a slightly lower pH, while the free acid signal (at 8 ppm) emerges under the most acidic medium. Moreover, the stabilities of the hydrogen‐bonded carboxylic acid dimers can be inferred from the proton‐proton distances within the dimers, i.e. (275 ± 5) pm and (295 ± 15) pm for the protons at 12.5 and 10.5 ppm, respectively, which are determined by means of DQ MAS sideband patterns. Both the stability of the hydrogen bonds and the acidity of the protons may be related to the stereochemistry and the conformation of the PMAA chains.

  相似文献   

110.
There have been contradictory findings in the fragile X (fraX) literature about possible neurocognitive and psychological symptoms due to the fraX premutation (pM). The purpose of the present study was to investigate the relationship between CGG repeat length and neurobehavioral functioning in carriers of the fraX pM. Eighty‐five female carriers of the pM with allele sizes ranging from 59–166 were administered a comprehensive IQ test (WAIS‐III) and completed a questionnaire designed to measure psychopathology (Symptom Checklist (SCL)‐90‐R). No relationship between allele size and cognition was identified. A significant negative relationship between allele size and age was found, as well as a positive relationship between allele size and depression. Follow‐up analyses separating small and large allele sizes (below and above 100 CGG repeats) indicated that individuals with larger allele sizes scored significantly higher on the Interpersonal Sensitivity and Depression subscales of the SCL‐90‐R. Despite the limitation of few individuals with high CGG repeat lengths, our findings suggest that females with larger premutated alleles (≥ 100 repeats) display some clinical manifestations of fraX syndrome. © 2001 Wiley‐Liss, Inc.  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