全文获取类型
收费全文 | 3017篇 |
免费 | 260篇 |
国内免费 | 8篇 |
专业分类
耳鼻咽喉 | 26篇 |
儿科学 | 91篇 |
妇产科学 | 57篇 |
基础医学 | 463篇 |
口腔科学 | 33篇 |
临床医学 | 339篇 |
内科学 | 562篇 |
皮肤病学 | 58篇 |
神经病学 | 163篇 |
特种医学 | 340篇 |
外科学 | 312篇 |
综合类 | 126篇 |
一般理论 | 2篇 |
预防医学 | 396篇 |
眼科学 | 27篇 |
药学 | 146篇 |
1篇 | |
中国医学 | 8篇 |
肿瘤学 | 135篇 |
出版年
2021年 | 45篇 |
2019年 | 28篇 |
2018年 | 41篇 |
2017年 | 27篇 |
2016年 | 32篇 |
2015年 | 45篇 |
2014年 | 59篇 |
2013年 | 89篇 |
2012年 | 115篇 |
2011年 | 108篇 |
2010年 | 67篇 |
2009年 | 78篇 |
2008年 | 119篇 |
2007年 | 109篇 |
2006年 | 102篇 |
2005年 | 100篇 |
2004年 | 89篇 |
2003年 | 105篇 |
2002年 | 96篇 |
2001年 | 87篇 |
2000年 | 107篇 |
1999年 | 83篇 |
1998年 | 64篇 |
1997年 | 65篇 |
1996年 | 77篇 |
1995年 | 65篇 |
1994年 | 70篇 |
1993年 | 48篇 |
1992年 | 66篇 |
1991年 | 65篇 |
1990年 | 63篇 |
1989年 | 90篇 |
1988年 | 67篇 |
1987年 | 81篇 |
1986年 | 74篇 |
1985年 | 57篇 |
1984年 | 41篇 |
1983年 | 37篇 |
1982年 | 28篇 |
1981年 | 37篇 |
1980年 | 35篇 |
1979年 | 41篇 |
1978年 | 33篇 |
1977年 | 40篇 |
1976年 | 33篇 |
1975年 | 35篇 |
1972年 | 22篇 |
1971年 | 24篇 |
1970年 | 21篇 |
1969年 | 21篇 |
排序方式: 共有3285条查询结果,搜索用时 15 毫秒
51.
52.
Metal ions and human sperm mannose receptors 总被引:5,自引:0,他引:5
Zinc and lead concentrations were measured in seminal plasma from fertile donors, infertile men with varicocoele and men undergoing work-ups for in vitro fertilization. Ejaculated spermatozoa from these subjects were incubated in vitro with various metal ions and/or dibromoethane and dibromochloropropane. Mannose receptor expression was correlated with metal and toxicant levels. Sperm distributions of potassium channels were compared with lead ions and calcium channels with zinc ions. Mannose receptor expression by capacitated spermatozoa increased linearly with seminal plasma zinc levels, and correlated inversely with lead levels. Cobalt had no effect on mannose receptor expression, but nickel had a concentration-dependent biphasic effect. Mannose receptor expression was not affected by dibromoethane and dibromochloropropane if the cholesterol content of the sperm membrane was high, but mannose receptor expression was decreased in low cholesterol spermatozoa by exposures below estimated permissive exposure limits. Potassium channels and lead ions co-localized over the entire head of human spermatozoa, while both calcium channels and zinc ions were confined to the equatorial segment of the head. Mannose receptor expression on the external surface of the human sperm plasma membrane is a biomarker for the effects of transition and heavy metals and organic toxicants on sperm fertility potential. 相似文献
53.
54.
OBJECTIVES: To investigate maternal knowledge and attitudes about otitis media (OM) risk, to estimate the prevalence of risk factors in the first year of life, and to identify barriers to the reduction of risk factors (eg, formula feeding, day care attendance, and exposure to passive smoke). METHODS: Questionnaires mailed to a systematic sample of 504 Minnesota women >/=18 years old identified through 1994 birth certificates. RESULTS: Eighty percent returned a completed survey. According to maternal report, 29% of infants (age 8 to 13 months) had recurrent OM (>/=3 episodes) and 2% had tympanostomy tubes. Forty-six percent attended day care, 29% had >/=1 smoking parent, and 49% breastfed for =2 months. Women were more knowledgeable about OM signs and symptoms than about risk factors. Mean OM knowledge score (the sum of correct true-false responses) was 7.0 (standard deviation = 1.6). Using multiple linear regression, knowledge score was significantly related to marital status, education, age, area of residence, breastfeeding (months), and number of cigarettes smoked per day by the mother, but not to infant or sibling OM history or day care attendance (R = .23). Infant history of OM (odds ratio, 1.9; 95% confidence interval, 1.1 to 3.2) and white race (odds ratio, 0.3; 95% confidence interval, 0. 1 to 0.8), but not the presence of risk factors, were significantly related to having received clinicians' advice about OM prevention advice. CONCLUSION: OM education and prevention programs should target pregnant women and new mothers with OM risk factors, and those who are young, single, and less educated. 相似文献
55.
Hansen LA; Malarkey DE; Wilkinson JE; Rosenberg M; Woychik RE; Tennant RW 《Carcinogenesis》1998,19(10):1837-1845
We previously reported that papillomas can arise from the follicular
epithelium of v-Ha-ras transgenic TGxAC mice. Since the viable-yellow
mutation (A(vy)) of the mouse agouti gene which regulates coat color
pigmentation by acting within the micro-environment of the hair follicle
has been shown to function as a tumor promoter in the liver, we
hypothesized that it may also play a role in TGxAC skin tumorigenesis.
Endogenous agouti protein product was detected in the outer root sheath of
anagen hair follicles following plucking of the hair shaft, but not in the
interfollicular epithelium, in TGxAC mice on an FVB/N genetic background.
It was also detected in papillomas from these mice produced by
12-O-tetradecanoylphorbol-13-acetate (TPA) treatment or plucking.
Expression of the A(vy) allele in the v-Ha-ras transgenic TGxAC mouse line
results in an approximately 2-fold increase in papilloma development
compared with controls which did not carry the A(vy) allele following
twice-weekly treatment with 1.25, 2.5 or 5.0 microg TPA. In addition,
TPA-treated, papilloma-bearing F1 mice which carried the A(vy) allele, but
not F1 mice which did not carry the A(vy) allele, exhibited a syndrome of
humoral hypercalcemia mediated by parathyroid hormone-related protein
(PTHrP) that led to weight loss, hypercalcemia and hypophosphatemia. Thus,
we conclude that the A(vy) allele can influence the development of skin
tumors and PTHrP-mediated humoral hypercalcemia in v-Ha-ras transgenic
TGxAC mice.
相似文献
56.
57.
R.P. Kerr T.M. Krunkosky D.J. Hurley B.S. Cummings S.D. Holladay R.M. Gogal 《Toxicology in vitro》2013,27(3):1018-1024
Aberrant major histocompatibility complex class II (MHC-II) surface expression on antigen presenting cells (APCs) is associated with dysregulated immune homeostasis. Lead (Pb) is known to increase MHC-II surface expression on murine peritoneal macrophages ex vivo at concentrations exceeding 25 μM. Little data exist examining this effect at physiologically relevant concentrations. To address this deficit, we examined the effects of Pb on MHC-II surface expression, secondary T-cell activation markers (CD80, CD86, CD40), cell viability, cellular metabolic activity, and β-hexosaminidase activity in RAW 267.4 macrophage cell lines, with changes in cell ultrastructure evaluated by electron and confocal microscopy. Pb induced an increase in MHC-II, CD86, and lysosome-associated LAMP-1 and LAMP-2 surface mean expression during one doubling cycle (17 h), which was mirrored by increased β-hexosaminidase activity. Although cell viability was unaffected, cellular metabolism was inhibited. Electron microscopy revealed evidence of lipid vacuolization, macroautophagy and myelin figure formation in cells cultured with either Pb or LPS. Confocal microscopy with antibodies against LC3B showed a punctate pattern consistent with the presence of mature autophagosomes. Collectively, these data suggest that 2.5–5.0 μM Pb increased MHC-II surface expression by inhibiting metabolic activity, inducing autophagy, and increasing MHC-II trafficking in a macrophage cell line. 相似文献
58.
59.
Thomas M. Atkinson Karen Hurley Carma L. Bylund Alexandra Berk Kimberly Diminni Jamie S. Ostroff 《Journal of cancer education》2013,28(1):33-37
This paper describes the development and initial evaluation of a didactic curriculum to prepare research support staff with the core knowledge and skills required to collect patient-reported outcomes (PROs) via interviews. Research support staff members (N?=?77) were recruited for eight separate workshops, each consisting of a didactic presentation followed by role-play scenarios with trained actors depicting common scenarios they may encounter as part of patient interaction. Trainees were observed and received feedback on their performance from trained facilitators and peers. In comparison to their pre-training assessment, trainees showed significant improvement in their confidence to conduct a research interview, handle a distressed participant, manage a wandering interview, ask participants sensitive questions, and handle irritated patients. Training research support staff in the effective collection of PROs via patient interviews can improve the confidence of these individuals in interacting with patients, which can ultimately lead to increased accuracy of data collection. 相似文献
60.
Estela Trebicka Susan Jacob Waheed Pirzai Bryan P. Hurley Bobby J. Cherayil 《Clinical and Vaccine Immunology : CVI》2013,20(10):1491-1498
Recent observations from Africa have rekindled interest in the role of serum bactericidal antibodies in protecting against systemic infection with Salmonella enterica serovar Typhimurium. To determine whether the findings are applicable to other populations, we analyzed serum samples collected from healthy individuals in the United States. We found that all but 1 of the 49 adult samples tested had robust bactericidal activity against S. Typhimurium in a standard in vitro assay. The activity was dependent on complement and could be reproduced by immunoglobulin G (IgG) purified from the sera. The bactericidal activity was inhibited by competition with soluble lipopolysaccharide (LPS) from S. Typhimurium but not from Escherichia coli, consistent with recognition of a determinant in the O-antigen polysaccharide. Sera from healthy children aged 10 to 48 months also had bactericidal activity, although it was significantly less than in the adults, correlating with lower levels of LPS-specific IgM and IgG. The lone sample in our collection that lacked bactericidal activity was able to inhibit killing of S. Typhimurium by the other sera. The inhibition correlated with the presence of an LPS-specific IgM and was associated with decreased complement deposition on the bacterial surface. Our results indicate that healthy individuals can have circulating antibodies to LPS that either mediate or inhibit killing of S. Typhimurium. The findings contrast with the observations from Africa, which linked bactericidal activity to antibodies against an S. Typhimurium outer membrane protein and correlated the presence of inhibitory anti-LPS antibodies with human immunodeficiency virus infection. 相似文献