全文获取类型
收费全文 | 20289篇 |
免费 | 2064篇 |
国内免费 | 31篇 |
专业分类
耳鼻咽喉 | 129篇 |
儿科学 | 674篇 |
妇产科学 | 742篇 |
基础医学 | 2988篇 |
口腔科学 | 535篇 |
临床医学 | 2384篇 |
内科学 | 4022篇 |
皮肤病学 | 302篇 |
神经病学 | 1829篇 |
特种医学 | 617篇 |
外科学 | 2519篇 |
综合类 | 553篇 |
一般理论 | 17篇 |
预防医学 | 2075篇 |
眼科学 | 229篇 |
药学 | 1713篇 |
中国医学 | 32篇 |
肿瘤学 | 1024篇 |
出版年
2021年 | 235篇 |
2020年 | 162篇 |
2019年 | 257篇 |
2018年 | 309篇 |
2017年 | 210篇 |
2016年 | 256篇 |
2015年 | 318篇 |
2014年 | 407篇 |
2013年 | 624篇 |
2012年 | 911篇 |
2011年 | 947篇 |
2010年 | 544篇 |
2009年 | 517篇 |
2008年 | 810篇 |
2007年 | 976篇 |
2006年 | 897篇 |
2005年 | 788篇 |
2004年 | 852篇 |
2003年 | 788篇 |
2002年 | 762篇 |
2001年 | 705篇 |
2000年 | 691篇 |
1999年 | 633篇 |
1998年 | 262篇 |
1997年 | 254篇 |
1996年 | 217篇 |
1995年 | 221篇 |
1994年 | 174篇 |
1993年 | 180篇 |
1992年 | 515篇 |
1991年 | 495篇 |
1990年 | 436篇 |
1989年 | 541篇 |
1988年 | 437篇 |
1987年 | 405篇 |
1986年 | 447篇 |
1985年 | 356篇 |
1984年 | 304篇 |
1983年 | 322篇 |
1982年 | 176篇 |
1981年 | 166篇 |
1979年 | 242篇 |
1978年 | 183篇 |
1977年 | 159篇 |
1976年 | 159篇 |
1974年 | 153篇 |
1973年 | 181篇 |
1972年 | 152篇 |
1971年 | 160篇 |
1970年 | 139篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
23.
24.
B Walker 《Toxicology and industrial health》1989,5(4):31-4; discussion 79-84
25.
Phyllis W Sharps Ayman A E El-Mohandes M Nabil El-Khorazaty Michele Kiely Tessa Walker 《Journal of perinatology》2003,23(5):414-419
OBJECTIVE: To describe breastfeeding initiation among 210 urban African-American mothers with inadequate prenatal care. METHODS: This study is a case-control study of postpartum mothers recruited from four large urban hospitals. RESULTS: Mothers who chose to breastfeed were more educated, employed before birth, married, and using contraception postnatally. Regression model analysis controlling for demographic differences revealed that breastfeeding was significantly associated with a higher perception of severity of illness and higher confidence in the ability of health care to prevent illness. Breastfeeding mothers were less likely to reverse parent-child roles and had a lower perception of hassle from their infant's behavior. When comparing mothers who breastfed longer than 8 weeks to those who did not breastfeed, breastfeeding mothers had high scores related to empathy toward infants on the Adult-Adolescent Parenting Inventory as well as a low perception of hassle on the Parenting Daily Hassle. The perception of existing formal or informal social support did not influence breastfeeding behavior. CONCLUSION: Personal attributes of low-income urban mothers such as health beliefs and parental attitudes may play a role in the initiation and duration of breastfeeding. Low-income African-American mothers may be influenced in their choice to breastfeed by supportive messages from physicians and nurses delivering care to mothers and their newborns. Emphasis should be placed on the role breastfeeding can play in preventing childhood illnesses. 相似文献
26.
27.
J F Walker L M Archibald S R Cherniak V G Fish 《Journal of speech and hearing research》1992,35(1):4-13
The major purposes of this study were to provide normative data on articulation rate in preschool children and to examine the influence on articulation rate of age, gender, context, and utterance length. The subjects were twenty 3-year-old children and twenty 5-year-old children, equally balanced for gender. Durational measures of utterances were analyzed in syllables and phones per second in both spontaneous and imitated speech contexts. The articulation rate of the 5-year-old subjects was significantly faster than that of the 3-year-olds. Spontaneous speech was significantly faster and more variable than imitated speech. Some gender differences were found. Measures in syllables per second and phones per second, although not always yielding identical results, were found to be highly correlated. 相似文献
28.
29.
G W Blunn A B Joshi P A Lilley E Engelbrecht L Ryd L Lidgren K Hardinge E Nieder P S Walker 《Acta orthopaedica Scandinavica》1992,63(3):247-255
106 unicondylar knee replacement tibial components were retrieved and analyzed for the amount and type of polyethylene wear. Three different designs were retrieved which had essentially the same femorotibial conformity. Each design showed a characteristic failure pattern. The polyethylene of PCA tibial components showed serious delamination after only short durations, as a result of heat pressing. St Georg sledge prostheses showed some delamination after 4 years' duration due to sub-surface cracks which were initiated by fusion defects in the polyethylene; metal backing of the components did not affect delamination of this prosthesis. The Marmor designs showed the least wear, with shiny depressions and surface pitting; no delamination was observed in the Marmor prosthesis. Molecular weight determination by gel permeation chromatography and analysis of crystallinity using Fourier transformation infra-red spectroscopy demonstrated that St George polyethylene had higher molecular weight and crystallinity than Marmor polyethylene. In some of the components investigated, crystallinity and molecular weight of the polyethylene were reduced under the wear track when compared with the unworn polyethylene. Since fusion defects may cause delamination of polyethylene we urge manufacturers to reduce the number of such defects. 相似文献
30.
The incidence of transient hypogammaglobulinaemia of infancy (THI) detected in a major paediatric centre over a 10 year period was examined. A total of 2468 subjects less than 2 years of age had an IgG measurement taken between July 1979 and March 1990. Subjects with known immunodeficiencies were excluded. Fifteen patients were classified as having THI with an initial IgG level less than the fifth centile followed by a second measurement within the normal range. A further 24 patients were identified as having possible THI with a single low IgG concentration. There were 60,174 live births each year in Victoria in the years 1979-88. This gives an incidence of proved THI of 23 per 10(6) births, and including proved and probable THI an incidence of 61 per 10(6) live births. Of those patients with proved THI 12/15 had symptoms of either atopic disease or food allergy/intolerance and three had gastrointestinal symptoms without any evidence of atopic disease. At presentation 12/15 (80%) were IgA deficient and 9/15 had IgM concentrations less than the 20th centile for age. It is suggested that in view of the preponderance of atopic and food intolerant patients that subclinical protein loss from the bowel due to allergic inflammation may be a contributing factor to the development of THI in some patients. 相似文献