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   19516篇
  免费   1806篇
  国内免费   34篇
耳鼻咽喉   247篇
儿科学   621篇
妇产科学   494篇
基础医学   2319篇
口腔科学   390篇
临床医学   2568篇
内科学   3771篇
皮肤病学   248篇
神经病学   1411篇
特种医学   859篇
外国民族医学   3篇
外科学   2512篇
综合类   602篇
一般理论   9篇
预防医学   2068篇
眼科学   605篇
药学   1576篇
  1篇
中国医学   87篇
肿瘤学   965篇
  2021年   328篇
  2020年   215篇
  2019年   293篇
  2018年   333篇
  2017年   221篇
  2016年   296篇
  2015年   330篇
  2014年   442篇
  2013年   613篇
  2012年   844篇
  2011年   908篇
  2010年   524篇
  2009年   442篇
  2008年   770篇
  2007年   852篇
  2006年   876篇
  2005年   785篇
  2004年   777篇
  2003年   700篇
  2002年   656篇
  2001年   588篇
  2000年   607篇
  1999年   544篇
  1998年   254篇
  1997年   242篇
  1996年   233篇
  1995年   227篇
  1994年   216篇
  1993年   183篇
  1992年   423篇
  1991年   427篇
  1990年   395篇
  1989年   425篇
  1988年   371篇
  1987年   358篇
  1986年   354篇
  1985年   330篇
  1984年   278篇
  1983年   239篇
  1982年   163篇
  1981年   141篇
  1980年   119篇
  1979年   198篇
  1978年   173篇
  1977年   150篇
  1976年   134篇
  1974年   163篇
  1973年   146篇
  1972年   130篇
  1971年   119篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
162.
In patients with phenylketonuria (PKU), treated by diet therapy only, evidence suggests that areal bone mineral density (BMDa) is within the normal clinical reference range but is below the population norm. Aims: To study longitudinal bone density, mass, and geometry over 36 months in children with PKU taking either amino acid (L-AA) or casein glycomacropeptide substitutes (CGMP-AA) as their main protein source. Methodology: A total of 48 subjects completed the study, 19 subjects in the L-AA group (median age 11.1, range 5–16 years) and 29 subjects in the CGMP-AA group (median age 8.3, range 5–16 years). The CGMP-AA was further divided into two groups, CGMP100 (median age 9.2, range 5–16 years) (n = 13), children taking CGMP-AA only and CGMP50 (median age 7.3, range 5–15 years) (n = 16), children taking a combination of CGMP-AA and L-AA. Dual X-ray absorptiometry (DXA) was measured at enrolment and 36 months, peripheral quantitative computer tomography (pQCT) at 36 months only, and serum blood and urine bone turnover markers (BTM) and blood bone biochemistry at enrolment, 6, 12, and 36 months. Results: No statistically significant differences were found between the three groups for DXA outcome parameters, i.e., BMDa (L2–L4 BMDa g/cm2), bone mineral apparent density (L2–L4 BMAD g/cm3) and total body less head BMDa (TBLH g/cm2). All blood biochemistry markers were within the reference ranges, and BTM showed active bone turnover with a trend for BTM to decrease with increasing age. Conclusions: Bone density was clinically normal, although the median z scores were below the population mean. BTM showed active bone turnover and blood biochemistry was within the reference ranges. There appeared to be no advantage to bone density, mass, or geometry from taking a macropeptide-based protein substitute as compared with L-AAs.  相似文献   
163.
Police stops are the most common form of criminal justice exposure in the USA, and are particularly common among urban youth, with 23% of them reporting a stop by the age of 15. While recent work has begun to illuminate the health impacts of police stops for these youth, little is known about the health consequences of youth police contact for the mothers of youth stopped by the police. The current study employs data from the Fragile Families and Child Wellbeing Study (FFCWS), a sample of urban, at-risk youth and their families. Multivariate logistic regression models are conducted to examine the link between youth police stops and sleep difficulties among mothers. Additional analyses examine whether the features and consequences of police stops are associated with sleep difficulties among mothers. The findings indicate that mothers with youth who have experienced police stops are more than twice as likely to report both depression- and anxiety-related sleep difficulties compared to their counterparts. Furthermore, stops with certain features—including those characterized by intrusiveness, high trauma, and high stigma—emerged as consistently significant predictors of maternal sleep difficulties. The findings suggest that mothers who are vicariously exposed to police contact via their children are a vulnerable group. Given the non-random distribution of police contact across the population of youth, with police contact concentrated among children of color, the findings suggest that police contact may exacerbate racial inequalities in sleep, which may itself contribute to racial disparities in broader mental and physical health outcomes.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11524-021-00518-1.  相似文献   
164.
目的:应用微乳液反应法制备磺胺嘧啶银均匀微晶,均匀制得的微晶的粒径大小约为2~4um,均匀微晶的结晶性好,纯度高。用均匀设计方法优化条件,制备的均匀的微晶平均粒径大小为2.09um,实验结果达到预测结果要求。结论:用微乳液反应法能获得磺胺嘧啶银均匀微晶。  相似文献   
165.
166.
167.
Plasma samples derived from 33 Alzheimer's disease (AD) and 42 control participants were subjected to several steps to purify specific anti-(amyloid)Abeta IgGs. Affinity-purified IgGs binding the peptide Abeta1-42, a neurotoxic sequence derived from the trans-membrane amyloid precursor protein, exhibited nearly four-fold higher titers in AD patients compared with their control non-AD cohort. Affinity-purified IgGs binding a fragment of the receptor for advanced glycation end products (RAGE) likewise were increased nearly three-fold in AD individuals. Abeta and RAGE IgG titers were negatively correlated with cognitive status, i.e. the more cognitively impaired individuals tended to exhibit higher IgG titers. Abeta IgG titers were negatively correlated with age in the control group, but not with the AD group. Levels of circulating AB- and RAGE-like proteins were not different between AD and control participants, nor was there a relationship between individual IgG titers and the respective Abeta- and RAGE-like proteins. Freshly prepared leukocyte preparations were subjected to flow cytometric analysis. AD individuals exhibited significantly increased populations of cells expressing binding sites for monoclonal antibodies directed against Abeta (5.5-fold), betaAPP (3.5-fold), and RAGE (2.6-fold) relative to the control group. These findings confirm the presence of circulating IgGs specifically directed at proteins implicated in immunological processes linked to AD. The close relationship between titers for Abeta and RAGE IgGs suggests the possibility that the antibodies are being produced in response to a common mechanism or protein complex (with the respective epitopes) linked to the disease.  相似文献   
168.
Structure and receptor binding   总被引:42,自引:0,他引:42  
  相似文献   
169.
The miniresidency program in geriatrics begun in 1985 at the University of California, San Diego, School of Medicine acquaints practicing health professionals with a multidisciplinary team approach to the care of geriatric patients. The two-week program features participation in a multidisciplinary outpatient clinic, home visits, social work and nutrition consultations, and conferences with patients and families. Miniresidency members also participate in neurologic and neuropsychological evaluations and attend day care for demented adults. The 71 health professionals who completed the program during its first 20 months showed significant improvement on their scores between the pre- and posttests: the mean of all scores in the pretest was 51 out of a possible 80 (SD 15); the mean of all scores in the posttest was 75 out of a possible 80 (SD 4); p less than .001. The 77% who returned post-program evaluation questionnaires found the program "useful" or "very useful."  相似文献   
170.
1. The repeatability of a computerised psychomotor test battery on a day-to-day and week-to-week basis was assessed by determining its test-retest reliability and variations in group-means and intraindividual psychomotor performance scores of elderly people. 2. Psychomotor performance was assessed in 50 well-screened elderly subjects (21 males, 29 females; mean age 70.4 +/- 5.0 (s.d.) years) on 5 consecutive days and over 4 weeks in standardised test conditions. 3. The psychomotor test battery consisted of computerised versions of symbol digit substitution test (SDST), continuous attention test (CAT), choice reaction time (CRT), critical flicker fusion test (CFFT), cognitive flexibility test (FLEX), paired word association test (PWAT) and inspection time (INSP). 4. Main outcome measures were test-retest reliability, group variability and intraindividual variability. 5. There was no significant variation in group-means for all components of the test battery over 5 days or 4 weeks on two way analysis of variance. The intraindividual coefficient of variation was low for SDST, CRT, CFFT, FLEX, PWAT and INSP during the period of assessment. Test retest reliability was greater than 0.8 for SDST, CAT, CRT and PWAT. 6. Tests in the Automated Psychomotor Test Battery are reliable and repeatable measures of psychomotor performance on a day-to-day and week-to-week basis.  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