全文获取类型
收费全文 | 538篇 |
免费 | 23篇 |
国内免费 | 2篇 |
专业分类
耳鼻咽喉 | 2篇 |
儿科学 | 55篇 |
妇产科学 | 3篇 |
基础医学 | 64篇 |
口腔科学 | 11篇 |
临床医学 | 71篇 |
内科学 | 133篇 |
皮肤病学 | 21篇 |
神经病学 | 2篇 |
特种医学 | 139篇 |
外科学 | 14篇 |
综合类 | 9篇 |
预防医学 | 6篇 |
眼科学 | 4篇 |
药学 | 13篇 |
肿瘤学 | 16篇 |
出版年
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 6篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 14篇 |
2012年 | 6篇 |
2011年 | 10篇 |
2010年 | 23篇 |
2009年 | 19篇 |
2008年 | 8篇 |
2007年 | 5篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 4篇 |
2003年 | 8篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 35篇 |
1997年 | 46篇 |
1996年 | 45篇 |
1995年 | 36篇 |
1994年 | 19篇 |
1993年 | 22篇 |
1992年 | 6篇 |
1991年 | 11篇 |
1990年 | 6篇 |
1989年 | 17篇 |
1988年 | 27篇 |
1987年 | 21篇 |
1986年 | 23篇 |
1985年 | 13篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 14篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1975年 | 9篇 |
1974年 | 1篇 |
排序方式: 共有563条查询结果,搜索用时 0 毫秒
91.
92.
93.
94.
Detecting pre-ovulatory luteinizing hormone surges in urine 总被引:2,自引:1,他引:2
Kesner JS; Knecht EA; Krieg EF Jr; Wilcox AJ; O'Connor JF 《Human reproduction (Oxford, England)》1998,13(1):15-21
The study objectives were to determine (i) if pre-ovulatory luteinizing
hormone (LH) surges, undetected in urine by two immunoradiometric assays
(IRMA), were detectable by an ultrasensitive immunofluorometric assay
(IFMA) and (ii) the influence of creatinine adjustment on the detection and
timing of the urinary LH surges. Daily urine specimens were contributed by
healthy 25-36 year old volunteers during 14 ovulatory menstrual cycles for
an epidemiological study conducted in 1983-1985. Specimens were selected as
having been previously assayed by two IRMA without consistently detecting
LH surges. These urine specimens were remeasured using an IFMA and adjusted
for creatinine concentration. IFMA measurements revealed unambiguous LH
surges in all cycles. Adjusting IRMA urinary LH values for creatinine
concentrations revealed previously undetected LH surges in four of eight
cycles. Creatinine adjustment also altered the timing of IRMA and IFMA LH
surges by 1-5 days. These results demonstrate an IFMA that detects pre-
ovulatory LH surges in unpreserved, frozen urine from cycles where such
surges were previously undetectable. Further, creatinine adjustment can
markedly affect detection and timing of the onset and peak of the urinary
LH surge. While our analysis suggests that this adjustment improves the
validity of the LH measure, this requires further investigation.
相似文献
95.
HPM Smedts JH de Vries M Rakhshandehroo MF Wildhagen AC Verkleij-Hagoort EA Steegers RPM Steegers-Theunissen 《BJOG : an international journal of obstetrics and gynaecology》2009,116(3):416-423
Objective To study associations between maternal dietary and supplement intake of antioxidants vitamin E, retinol and congenital heart defects (CHDs).
Design Case–control study.
Setting Erasmus MC, University Medical Center Rotterdam, the Netherlands.
Population Participants were 276 case mothers of a child with CHD and 324 control mothers with their children.
Methods Food frequency questionnaires covering the intake of the previous 4 weeks were filled out at 16 months after the index pregnancy. Data were compared between cases and controls using the Mann–Whitney U test. Risk estimates for the association between CHD and dietary intake of vitamin E and retinol were estimated in a multivariable logistic regression model.
Main outcome measures Medians (5–95th percentile) and odds ratios with 95% CI.
Results Dietary vitamin E intake was higher in case mothers than in controls, 13.3 (8.1–20.4) and 12.6 (8.5–19.8) mg/day ( P = 0.05). CHD risk increased with rising dietary vitamin E intakes ( P -trend = 0.01). Periconception use of vitamin E supplements in addition to a high dietary vitamin E intake above 14.9 mg/day up to nine-fold increased CHD risk. Retinol intakes were not significantly different between the groups and not associated with CHD risk.
Conclusions High maternal vitamin E by diet and supplements is associated with an increased risk of CHD offspring. 相似文献
Design Case–control study.
Setting Erasmus MC, University Medical Center Rotterdam, the Netherlands.
Population Participants were 276 case mothers of a child with CHD and 324 control mothers with their children.
Methods Food frequency questionnaires covering the intake of the previous 4 weeks were filled out at 16 months after the index pregnancy. Data were compared between cases and controls using the Mann–Whitney U test. Risk estimates for the association between CHD and dietary intake of vitamin E and retinol were estimated in a multivariable logistic regression model.
Main outcome measures Medians (5–95th percentile) and odds ratios with 95% CI.
Results Dietary vitamin E intake was higher in case mothers than in controls, 13.3 (8.1–20.4) and 12.6 (8.5–19.8) mg/day ( P = 0.05). CHD risk increased with rising dietary vitamin E intakes ( P -trend = 0.01). Periconception use of vitamin E supplements in addition to a high dietary vitamin E intake above 14.9 mg/day up to nine-fold increased CHD risk. Retinol intakes were not significantly different between the groups and not associated with CHD risk.
Conclusions High maternal vitamin E by diet and supplements is associated with an increased risk of CHD offspring. 相似文献
96.
97.
BACKGROUND: Hospitals and blood centers throughout the United States use a variety of reagents and methods to perform pretransfusion testing. A survey was developed to determine the reagents and methods in use and their relative prevalence in different work settings. STUDY DESIGN AND METHODS: A national survey on pretransfusion testing was conducted. Surveys were distributed to state and regional blood bank associations, which then distributed them to hospitals and blood centers within their region. In most instances, the blood centers distributed the survey to the local hospitals. Completed surveys were returned to the authors for review, and all information was entered into a database for analysis. RESULTS: Analysis of the data shows that the majority of blood banks use monoclonal reagents for ABO testing and monoclonal-polyclonal blended reagents for Rh testing. The data show that anti-IgG and polyclonal antihuman globulin reagents are used almost equally for antibody screening (detection) tests and that most blood banks use a three-cell antibody-screening test. Slightly more than 50 percent of hospitals use an immediate-spin crossmatch in the absence of unexpected antibodies. CONCLUSION: A number of approved reagents and methods are used by blood bank laboratories for pretransfusion testing. Facility size (number of beds) and type tend to influence the choice of methods and reagents employed. This survey provides an opportunity for blood bank laboratories to compare their current practices with those of their peers. 相似文献
98.
MP Busch ; EA Operskalski ; JW Mosley ; CE Stevens ; ER Schiff ; SH Kleinman ; H Lee ; M Lee ; M Harris 《Transfusion》1994,34(10):858-864
BACKGROUND: The long-term course of human immunodeficiency virus type 1 (HIV-1)-related disease among seropositive blood donors has not been described. The enrollment and epidemiologic background of HIV-1- infected donors in the Transfusion Safety Study and their immunologic and clinical progression are described. STUDY DESIGN AND METHODS: Through the testing of approximately 200,000 sera from donations made in late 1984 and early 1985, 146 anti-HIV-1-positive donors and 151 uninfected matched donors were enrolled. These two cohorts were followed with 6-month interval histories and laboratory testing. RESULTS: Seropositive donors detected before the institution of routine anti-HIV-1 screening disproportionately were first-time donors and men with exclusively male sexual contacts. The actuarial probability of a person's developing AIDS within 7 years after donation was 40 percent; the probability of a person's dying of AIDS was 28 percent. AIDS developed more often when the donor was p24 antigen-positive at donation. Over a 3-year period, significant decreases occurred in CD4+, CD2+CD26+, CD4+CD29+, and CD20+CD21+ counts, but not in CD8+ subsets, CD20+, or CD14+. CONCLUSION: The high proportions of first-time donations and exclusively homosexual men among seropositive donors suggest that test-seeking may have contributed to the high HIV-1 prevalence in the repository. Implementation of alternative test sites when routine donor screening began in 1985 may have averted many high- risk donations. The disease course in HIV-1-infected donors had the same wide spectrum of immunologic and clinical manifestations as were reported for other cohorts. 相似文献
99.
GTA Jombo EM Mbaawuaga AN Gyuse MNO Enenebeaku EE Okwori EJ Peters S Akpan F Odey EA Etukumana JT Akosu 《Asian Pacific journal of tropical medicine》2010,3(5):402-406
ObjectiveTo ascertain the socio-cultural factors influencing the rate of utilization of insecticide treated bed nets (ITNs) in a malaria endemic city of Makurdi, north central Nigeria.MethodsThe study was cross-sectional in nature using systematic sampling method to identify households. Both quantitative and qualitative data was generated from adult women using structured and semi structured questionnaires, and focused group discussions (FGDs) to obtain information on rate and patterns of utilization of ITNs. Information such as age, educational level, marital status, awareness or otherwise of the existence of malaria, and factors influencing rate of ownership and utilization of ITNs were obtained. FGDs were used to obtain qualitative information on rate of utilization of ITNs not captured in the questionnaires. Data obtained was analysed using Epi Info 6 statistical software.ResultsAmong the respondents interviewed, 97.0% (2 013/2 075) were aware of existence of malaria and 87.0% of these (1 751/2 013) would associate it with mosquitoes. The rate of ownership of any bed net, ITNs and untreated bed nets (UTNs) was 25.1%, 17.0% and 8.3%, respectively. Utilization of ITNs among children was 30.0% (112/373) and UTNs 12.9% (48/373). Positive contributors to ITNs utilization were literacy, enhanced economy, experience of marriage, and being gainfully employed (P<0.05); while negative contributors were ignorance, poverty and some cultural beliefs and values.ConclusionsA more synchronized advocacy should be carried out on the potential benefits of ITNs utilization and sustained. Also ITNs should be made available to the people of the community at minimal or no cost. 相似文献
100.
Legendre C; Raphael M; Gras G; Lefevre EA; Feuillard J; Dormont D; Richard Y 《International immunology》1998,10(12):1847-1851
A centrofollicular hyperplasia is present within secondary lymphoid organs
during all the asymptomatic phase of the HIV disease. Although this
hyperplasia has been well characterized by histological studies, the nature
of the phenotypic alterations in B cell populations occurring within HIV+
lymphoid organs remains to be established. By immunohistochemistry, we thus
investigated whether a particular germinal center (GC) B cell population
was increased during HIV-induced hyperplasia and whether any phenotypic
change was specific to HIV-1 infection. As compared to normal tonsils
(three cases) and HIV- hyperplastic lymph nodes (eight patients), we
observed a loss of GC polarization in all HIV+ sections (11 patients), with
no more delineation between dark and light zones, as shown by Ki67, CD10,
CD77, CD95 and CD86 staining. In contrast to CD86 expression which remained
as intensive in HIV+ as in HIV- lymph nodes, CD80 staining was strongly
decreased in GC of HIV+ lymph nodes but not in their extrafollicular zones.
The loss of CD80 expression from CD19+ B cells was also observed by
cytometric analysis of cell suspensions of three HIV+ patients. Although we
found no evidence of an increase in a particular GC B cell subset in
HIV-1-induced hyperplasia, the strong GC disorganization observed may
induce impaired cell-cell interactions and thus participate in the loss of
CD80 antigen. In contrast to HIV- situations where CD80 and CD86 was
similarly expressed on B cells, the lower level of CD80 expression in HIV+
GC may favor Th2 T cell responses through CD86-CD28 interactions.
相似文献