全文获取类型
收费全文 | 1947篇 |
免费 | 145篇 |
国内免费 | 39篇 |
专业分类
耳鼻咽喉 | 7篇 |
儿科学 | 86篇 |
妇产科学 | 64篇 |
基础医学 | 211篇 |
口腔科学 | 24篇 |
临床医学 | 220篇 |
内科学 | 381篇 |
皮肤病学 | 17篇 |
神经病学 | 108篇 |
特种医学 | 220篇 |
外科学 | 263篇 |
综合类 | 27篇 |
一般理论 | 2篇 |
预防医学 | 159篇 |
眼科学 | 21篇 |
药学 | 163篇 |
肿瘤学 | 158篇 |
出版年
2021年 | 31篇 |
2019年 | 24篇 |
2018年 | 35篇 |
2017年 | 23篇 |
2016年 | 26篇 |
2015年 | 33篇 |
2014年 | 37篇 |
2013年 | 57篇 |
2012年 | 74篇 |
2011年 | 87篇 |
2010年 | 71篇 |
2009年 | 75篇 |
2008年 | 76篇 |
2007年 | 89篇 |
2006年 | 68篇 |
2005年 | 69篇 |
2004年 | 44篇 |
2003年 | 68篇 |
2002年 | 56篇 |
2001年 | 67篇 |
2000年 | 49篇 |
1999年 | 51篇 |
1998年 | 65篇 |
1997年 | 58篇 |
1996年 | 56篇 |
1995年 | 57篇 |
1994年 | 45篇 |
1993年 | 40篇 |
1992年 | 37篇 |
1991年 | 34篇 |
1990年 | 38篇 |
1989年 | 42篇 |
1988年 | 47篇 |
1987年 | 33篇 |
1986年 | 44篇 |
1985年 | 33篇 |
1984年 | 22篇 |
1983年 | 15篇 |
1982年 | 17篇 |
1981年 | 13篇 |
1980年 | 18篇 |
1979年 | 16篇 |
1978年 | 15篇 |
1977年 | 20篇 |
1976年 | 19篇 |
1975年 | 13篇 |
1973年 | 11篇 |
1972年 | 10篇 |
1971年 | 13篇 |
1967年 | 10篇 |
排序方式: 共有2131条查询结果,搜索用时 15 毫秒
1.
Cynthia J. Hines Thomas J. Lentz Lauralynn McKernan Pranav Rane Christine Whittaker 《Journal of occupational and environmental hygiene》2019,16(2):120-128
Bisphenol A is a commercially important chemical used to make polycarbonate plastic, epoxy resins, and other specialty products. Despite an extensive body of in vitro, animal and human observational studies on the effects of exposure to bisphenol A, no authoritative bodies in the U.S. have adopted or recommended occupational exposure limits for bisphenol A. In 2017, the National Institute for Occupational Safety and Health published a Draft process for assigning health-protective occupational exposure bands, i.e., an airborne concentration range, to chemicals lacking an occupational exposure limit. Occupational exposure banding is a systematic process that uses both quantitative and qualitative toxicity information on selected health effect endpoints to assign an occupational exposure band for a chemical. The Draft process proposes three methodological tiers of increasing complexity for assigning an occupational exposure band. We applied Tier 1 (based on the Globally Harmonized System of Classification and Labelling) and Tier 2 (based on authoritative sources/reviews) to assign an occupational exposure band to bisphenol A. Under both Tier 1 and 2, the occupational exposure band for bisphenol A was “E” (<0.01?mg/m3), an assignment based on eye damage. “E” is the lowest exposure concentration range, reserved for chemicals with high potential toxicity. If eye damage was excluded in assigning an air concentration exposure range, then bisphenol A would band as “D” (>0.01 to 0.1?mg/m3) under Tier 1 (based on reproductive toxicity and respiratory/skin sensitization) and under Tier 2 (based on specific target organ toxicity-repeated exposure). In summary, Tiers 1 and 2 gave the same occupational exposure band for bisphenol A when eye damage was included (“E”) or excluded (“D”) as an endpoint. 相似文献
2.
Esther M. John Amanda I. Phipps Lisa M. Hines Jocelyn Koo Sue A. Ingles Kathy B. Baumgartner Martha L. Slattery Anna H. Wu 《International journal of cancer. Journal international du cancer》2020,147(7):1808-1822
We pooled multiethnic data from four population-based studies and examined associations of menstrual and reproductive characteristics with breast cancer (BC) risk by tumor hormone receptor (HR) status [defined by estrogen receptor (ER) and progesterone receptor (PR)]. We estimated odds ratios and 95% confidence intervals using multivariable logistic regression, stratified by age (<50, ≥50 years) and ethnicity, for 5,186 HR+ (ER+ or PR+) cases, 1,365 HR− (ER− and PR−) cases and 7,480 controls. For HR+ BC, later menarche and earlier menopause were associated with lower risk in non-Hispanic whites (NHWs) and Hispanics, and higher parity and longer breast-feeding were associated with lower risk in Hispanics and Asian Americans, and suggestively in NHWs. Positive associations with later first full-term pregnancy (FTP), longer interval between menarche and first FTP and shorter time since last FTP were limited to younger Hispanics and Asian Americans. Except for nulliparity, reproductive characteristics were not associated with risk in African Americans. For HR− BC, lower risk was associated with later menarche, except in African Americans and older Asian Americans and with longer breast-feeding in Hispanics and Asian Americans only. In younger African Americans, HR− BC risk associated with higher parity (≥3 vs. 1 FTP) was increased fourfold in women who never breast-fed, but not in those with a breast-feeding history, suggesting that breast-feeding may mitigate the adverse effect of higher parity in younger African American women. Further work needs to evaluate why menstrual and reproductive risk factors vary in importance according to age and ethnicity. 相似文献
3.
Tessa Timmers Rik Ossenkoppele Denise Visser Hayel Tuncel Emma E Wolters Sander CJ Verfaillie Wiesje M van der Flier Ronald Boellaard Sandeep SV Golla Bart NM van Berckel 《Journal of cerebral blood flow and metabolism》2020,40(12):2464
The aim of this study was to investigate the test–retest (TRT) repeatability of various parametric quantification methods for [18F]Flortaucipir positron emission tomography (PET). We included eight subjects with dementia or mild cognitive impairment due to Alzheimer’s disease and six cognitively normal subjects. All underwent two 130-min dynamic [18F]Flortaucipir PET scans within 3 ± 1 weeks. Data were analyzed using reference region models receptor parametric mapping (RPM), simplified reference tissue method 2 (SRTM2) and reference logan (RLogan), as well as standardized uptake value ratios (SUVr, time intervals 40–60, 80–100 and 110–130 min post-injection) with cerebellar gray matter as reference region. We obtained distribution volume ratio or SUVr, first for all brain regions and then in three tau-specific regions-of-interest (ROIs). TRT repeatability (%) was defined as |retest–test|/(average (test + retest)) × 100. For all methods and across ROIs, TRT repeatability ranged from (median (IQR)) 0.84% (0.68–2.15) to 6.84% (2.99–11.50). TRT repeatability was good for all reference methods used, although semi-quantitative models (i.e. SUVr) performed marginally worse than quantitative models, for instance TRT repeatability of RPM: 1.98% (0.78–3.58) vs. SUVr80–100: 3.05% (1.28–5.52), p < 0.001. Furthermore, for SUVr80–100 and SUVr110–130, with higher average SUVr, more variation was observed. In conclusion, while TRT repeatability was good for all models used, quantitative methods performed slightly better than semi-quantitative methods. 相似文献
4.
5.
6.
Gender differences in play behavior and physical aggression have been consistently reported. Theoretical perspectives concerning evolutionary, social, and social-cognitive mechanisms suggest that male-typical play behavior during childhood increases subsequent physical aggression. The evidence supporting these connections is limited, however. The present study investigated the association between gender-typed play behavior in early childhood and physical aggression in early adolescence using a sample drawn from a longitudinal, population study, the Avon Longitudinal Study of Parents and Children. Based on gender-typed play behavior as measured by the Pre-School Activities Inventory at age 3.5 years, samples of masculine (64 boys, 60 girls), feminine (80 boys, 66 girls), and randomly selected control children (55 boys, 67 girls) were recruited at age 13 years and administered the Reinisch Aggression Inventory. After controlling for a range of sociodemographic variables, maternal characteristics, and behavioral problems, including hyperactivity and conduct problems at age 3.5, significant group differences in physical aggression at age 13 were found among children classified as masculine, control, and feminine at age 3.5. Masculine children exhibited significantly more physical aggression than control children or feminine children, and control children exhibited significantly more physical aggression than feminine children. The association between gender-typed play behavior and physical aggression was not moderated by sex. These results suggest that the degree of childhood gender-typed play behavior independently predicts the degree of physical aggression at adolescence in boys and in girls. 相似文献
7.
Impulse oscillometry measurement of distal airways obstruction in depleted uranium‐exposed Gulf War veterans 下载免费PDF全文
Stella E. Hines MD MSPH Ashley H. Barnes BS Clayton Brown PhD Patricia Gucer PhD Marc S. Oliver RN MBA MPH Joanna M. Gaitens PhD MPH/MSN Marian Condon MSN Melissa McDiarmid MD MPH 《American journal of industrial medicine》2018,61(4):308-316
Introduction
A cohort of Gulf War I veterans who sustained exposure to depleted uranium undergoes biennial surveillance for potential uranium‐related health effects. We performed impulse oscillometry and hypothesized that veterans with higher uranium body burdens would have more obstructive abnormalities than those with lower burdens.Methods
We compared pulmonary function of veterans in high versus low urine uranium groups by evaluating spirometry and oscillometry values.Results
Overall mean spirometry and oscillometry resistance values fell within the normal ranges. There were no significant differences between the high and low uranium groups for any parameters. However, more veterans were classified as having obstruction by oscillometry (42%) than spirometry (8%).Conclusions
While oscillometry identified more veterans as obstructed, obstruction was not uranium‐related. However, the added sensitivity of this method implies a benefit in wider surveillance of exposed cohorts and holds promise in identifying abnormalities in areas of the lung historically described as silent.8.
Timothy B. Curry Casey N. Hines Jill N. Barnes Madhuri Somaraju Rita Basu John M. Miles Michael J. Joyner Nisha Charkoudian 《Clinical autonomic research》2014,24(2):77-85
Purpose
An association between insulin resistance and activation of the sympathetic nervous system has been reported in previous studies. However, potential interactions between insulin sensitivity and sympathetic neural mechanisms in healthy people remain poorly understood. We conducted a study to determine the relationship between sympathetic activity and insulin resistance in young, healthy humans.Methods
Thirty-seven healthy adults (18–35 years, BMI <28 kg m?2) were studied. Resting muscle sympathetic nerve activity (MSNA) was measured with microneurography and insulin sensitivity of glucose and free fatty acid metabolism was measured during a hyperinsulinemic-euglycemic clamp with two levels of insulin.Results
During lower doses of insulin, we found a small association between lower insulin sensitivity and higher MSNA (P < 0.05) but age was a cofactor in this relationship. Overall, we found no difference in insulin sensitivity between groups of low and high MSNA, but when women were analyzed separately, insulin sensitivity was lower in the high MSNA group compared with the low MSNA group of women.Conclusions
These data suggest that MSNA and insulin sensitivity are only weakly associated with young healthy individuals and that age and sex may be important modifiers of this relationship. 相似文献9.
Hines RN 《Pharmacology & therapeutics》2008,118(2):250-267
Profound changes in drug metabolizing enzyme (DME) expression occurs during development that impacts the risk of adverse drug events in the fetus and child. A review of our current knowledge suggests individual hepatic DME ontogeny can be categorized into one of three groups. Some enzymes, e.g., CYP3A7, are expressed at their highest level during the first trimester and either remain at high concentrations or decrease during gestation, but are silenced or expressed at low levels within one to two years after birth. SULT1A1 is an example of the second group of DME. These enzymes are expressed at relatively constant levels throughout gestation and minimal changes are observed postnatally. ADH1C is typical of the third DME group that are not expressed or are expressed at low levels in the fetus, usually during the second or third trimester. Substantial increases in enzyme levels are observed within the first one to two years after birth. Combined with our knowledge of other physiological factors during early life stages, knowledge regarding DME ontogeny has permitted the development of robust physiological based pharmacokinetic models and an improved capability to predict drug disposition in pediatric patients. This review will provide an overview of DME developmental expression patterns and discuss some implications of the data with regards to drug therapy. Common themes emerging from our current knowledge also will be discussed. Finally, the review will highlight gaps in knowledge that will be important to advance this field. 相似文献
10.
Smith SH 《Death Studies》2002,26(4):309-323
This article examines the ways in which religious beliefs of 30 African American, middle-aged daughters help them cope with the death of their elderly mothers. This qualitative, exploratory study found that daughters use their beliefs to move through states of grief that allow them to prepare, relinquish control, accept death, and maintain a connection to their mothers beyond death. Important themes identified in this study include the belief in an afterlife and the reunification of family members there. Findings suggest that religious beliefs provide a means for adult daughters to cope with the tasks of living in the present yet maintain a tie with their deceased mothers that serves to enhance their religious beliefs and fortitude in daily living. 相似文献