全文获取类型
收费全文 | 3064篇 |
免费 | 275篇 |
国内免费 | 9篇 |
专业分类
耳鼻咽喉 | 23篇 |
儿科学 | 173篇 |
妇产科学 | 87篇 |
基础医学 | 382篇 |
口腔科学 | 59篇 |
临床医学 | 367篇 |
内科学 | 501篇 |
皮肤病学 | 59篇 |
神经病学 | 227篇 |
特种医学 | 496篇 |
外科学 | 289篇 |
综合类 | 109篇 |
一般理论 | 1篇 |
预防医学 | 284篇 |
眼科学 | 12篇 |
药学 | 152篇 |
1篇 | |
中国医学 | 1篇 |
肿瘤学 | 125篇 |
出版年
2021年 | 46篇 |
2020年 | 38篇 |
2019年 | 49篇 |
2018年 | 54篇 |
2017年 | 48篇 |
2016年 | 46篇 |
2015年 | 53篇 |
2014年 | 86篇 |
2013年 | 104篇 |
2012年 | 96篇 |
2011年 | 108篇 |
2010年 | 79篇 |
2009年 | 97篇 |
2008年 | 94篇 |
2007年 | 110篇 |
2006年 | 93篇 |
2005年 | 100篇 |
2004年 | 82篇 |
2003年 | 69篇 |
2002年 | 64篇 |
2001年 | 68篇 |
2000年 | 71篇 |
1999年 | 69篇 |
1998年 | 105篇 |
1997年 | 93篇 |
1996年 | 90篇 |
1995年 | 79篇 |
1994年 | 44篇 |
1993年 | 70篇 |
1992年 | 43篇 |
1991年 | 38篇 |
1990年 | 47篇 |
1989年 | 83篇 |
1988年 | 65篇 |
1987年 | 59篇 |
1986年 | 73篇 |
1985年 | 106篇 |
1984年 | 65篇 |
1983年 | 39篇 |
1982年 | 40篇 |
1981年 | 44篇 |
1980年 | 46篇 |
1979年 | 20篇 |
1978年 | 27篇 |
1977年 | 39篇 |
1976年 | 30篇 |
1975年 | 29篇 |
1970年 | 21篇 |
1968年 | 19篇 |
1965年 | 21篇 |
排序方式: 共有3348条查询结果,搜索用时 15 毫秒
61.
Christina D Cota Pooneh Bagher Piotr Pelc C Owen Smith Christina R Bodner Teresa M Gunn 《Developmental dynamics》2006,235(12):3438-3447
Mahogunin Ring Finger 1 (Mgrn1) encodes a RING-containing protein with ubiquitin ligase activity that has been implicated in pigment-type switching. In addition to having dark fur, mice lacking MGRN1 develop adult-onset spongy degeneration of the central nervous system and have reduced embryonic viability. Observation of complete situs inversus in a small proportion of adult Mgrn1 mutant mice suggested that embryonic lethality resulted from congenital heart defects due to defective establishment and/or maintenance of the left-right (LR) axis. Here we report that Mgrn1 is expressed in a pattern consistent with a role in LR patterning during early development and that many Mgrn1 mutant embryos show abnormal expression of asymmetrically expressed genes involved in LR patterning. A range of complex heart defects was observed in 20-25% of mid-to-late gestation Mgrn1 mutant embryos and another 20% were dead. This finding was consistent with 46-60% mortality of mutants by weaning age. Our results indicate that Mgrn1 acts early in the LR signaling cascade and is likely to provide new insight into this developmental process as Nodal expression was uncoupled from expression of other Nodal-responsive genes in Mgrn1 mutant embryos. Our work identifies a novel role for MGRN1 in embryonic patterning and suggests that the ubiquitination of MGRN1 target genes is essential for the proper establishment and/or maintenance of the LR axis. 相似文献
62.
63.
Dadi Helgason Solveig Helgadottir Anders Ahlsson Jarmo Gunn Vibeke Hjortdal Emma C. Hansson Anders Jeppsson Ari Mennander Shahab Nozohoor Igor Zindovic Christian Olsson Stefan Orri Ragnarsson Martin I. Sigurdsson Arnar Geirsson Tomas Gudbjartsson 《The Annals of thoracic surgery》2021,111(4):1292-1298
64.
Partner acceptance of health department notification of HIV exposure, South Carolina 总被引:3,自引:0,他引:3
To determine the acceptability of health department notification of sex and needle-sharing partners of persons infected with human immunodeficiency virus (HIV), we administered an anonymous questionnaire to partners notified of their exposure to HIV during the previous 2 years. Of the 202 partners notified, 132 (65%) were locatable and completed the questionnaire. Only 12 (9%) thought they may have been exposed to HIV before health department notification. When the 132 partners were asked if they thought the health department did the right thing in telling them about their exposure, 87% responded "yes;" when asked if the health department should keep notifying persons exposed to HIV, 92% responded "yes." Responses were similar for homosexual-bisexual men, heterosexuals, and intravenous drug users; men and women; and whites and blacks. We conclude that health department notification is acceptable to persons exposed to HIV in this rural South Carolina district. 相似文献
65.
Gunn TW 《Michigan hospitals》1990,26(3):14-6, 18, 20-2
66.
Calcium absorption and kinetics are similar in 7- and 8-year-old Mexican-American and Caucasian girls despite hormonal differences 总被引:3,自引:0,他引:3
Abrams SA Copeland KC Gunn SK Stuff JE Clarke LL Ellis KJ 《The Journal of nutrition》1999,129(3):666-671
To assess the possibility of ethnic differences in mineral metabolism in prepubertal children, we compared measures of calcium metabolism in 7- and 8-y-old Mexican-American (MA) and non-Hispanic Caucasian (CAU) girls (n = 38) living in southeastern Texas. We found similar fractional calcium absorption, urinary calcium excretion, calcium kinetic values and total-body bone mineral content in the MA and CAU girls. In contrast, parathyroid hormone (PTH) concentrations were greater in MA girls (4.01 +/- 0.47 vs. 1. 96 +/- 0.50 pmol/L, P = 0.005) than in CAU girls. Serum 25-hydroxyvitamin D concentrations were lower in MA girls (68.9 +/- 7.7 vs. 109.4 +/- 8.4 nmol/L, P = 0.001) than in CAU girls, but 1, 25-dihydroxyvitamin D concentrations did not differ between groups. Seasonal variability was seen for 25-hydroxyvitamin D concentrations in girls of both ethnic groups, but values in all of the girls were >30 nmol/L (12 ng/mL). We conclude the following: 1) greater PTH levels in MA girls than CAU girls are present without evidence of vitamin D deficiency; and 2) differences in 25-hydroxyvitamin D and PTH concentrations between MA and CAU girls do not have a large effect on calcium absorption, excretion or bone calcium kinetics. These data do not provide evidence for adjusting dietary recommendations for mineral or vitamin D intake by MA girls. 相似文献
67.
68.
Objective: To identify factors that influence a woman's decision to breast-feed.
Methodology: Five hundred and fifty-six women were recruited from the maternity wards of two Perth hospitals. Data were collected from a self-administered questionnaire completed by participants prior to discharge. Logistic regression analysis was used to determine factors influencing the initiation of breast-feeding.
Results: At discharge from hospital 83.8% of women were breast-feeding, including 6% who were giving complementary formula feeds. After controlling for potentially confounding demographic and biomedical factors, the father's reported preference for breast-feeding was found to be the most important factor influencing a woman's decision to breast-feed (OR 10.18).
Conclusion: Fathers participate in and influence the choice of infant feeding method and should be included in breast-feeding discussions. 相似文献
Methodology: Five hundred and fifty-six women were recruited from the maternity wards of two Perth hospitals. Data were collected from a self-administered questionnaire completed by participants prior to discharge. Logistic regression analysis was used to determine factors influencing the initiation of breast-feeding.
Results: At discharge from hospital 83.8% of women were breast-feeding, including 6% who were giving complementary formula feeds. After controlling for potentially confounding demographic and biomedical factors, the father's reported preference for breast-feeding was found to be the most important factor influencing a woman's decision to breast-feed (OR 10.18).
Conclusion: Fathers participate in and influence the choice of infant feeding method and should be included in breast-feeding discussions. 相似文献
69.
OBJECTIVE: Most neonatologists include an apnea-free period in the criteria for the discharge of preterm infants. However, the length of time one should wait after the cessation of apnea before sending an infant home without a monitor is debated. We undertook this study in an attempt to define a minimal and safe observation period between the time of the last apnea episode and discharge. METHODS: We reasoned that in infants with idiopathic apnea of prematurity, the intervals between days on which apnea occurs gradually increase until some point at which clinically significant apnea ceases. Therefore, knowledge about the intervals between days on which apnea occurred just before the last apnea would provide a reasonable estimate of the minimal safe observation interval between the last apnea and discharge. We reviewed the charts of 266 infants born in 1993 and 1994 at =32 weeks' gestational age or weighing =1500 g at birth from two institutions to determine the intervals between the day on which the last apnea occurred and the previous two days on which apnea occurred. One hundred seventy-five infants were excluded because they never experienced apnea, or data about the last apnea was missing, or they were on xanthines during the period encompassing the last 3 apnea days, or they weighed <1500 g or were <34 weeks' postmenstrual age at the time of the last apnea. Of the 91 remaining infants, gestational age at birth, birth weight, 1- and 5-minute Apgar scores, and discharge weight were not different between the two institutions. For each infant we determined the longest of the intervals between the 2 days on which apnea occurred previous to the day of the last apnea (MAXINT for maximum interval). The infants were then ordered by MAXINT and, starting at the longest MAXINT, the medical records of each infant were carefully examined for other conditions known to be associated with apnea (eg, recovering from anesthesia, sepsis, chronic lung disease, and so forth). The minimal safe observation period was then defined as the longest MAXINT in which there was at least 1 infant with no other explanation for the apnea other than prematurity. RESULTS: The median duration of the intervals between the 2 days on which apnea occurred previous to the day on which the last apnea occurred were 3. 0 and 2.0 days and the median duration of the MAXINT was 4.0 days. On careful examination of the charts, it was determined that each of 13 infants with a MAXINT preceding the day on which the last apnea occurred of greater than 8 days had some other condition that might result in apnea, including residual lung disease, sepsis, surgery, and so forth. In contrast, among the group of infants with a MAXINT of =8 days, at least 1 infant at each MAXINT (eg, 1 to 8) had significant apnea with no other explanation other than prematurity. CONCLUSIONS: We conclude that otherwise healthy preterm infants continue to have apneas separated by as many as 8 days before the last apnea before discharge. Conversely, infants with longer apnea intervals often have identifiable risk factors other than apnea of prematurity. 相似文献
70.