全文获取类型
收费全文 | 477篇 |
免费 | 12篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 8篇 |
妇产科学 | 16篇 |
基础医学 | 36篇 |
口腔科学 | 2篇 |
临床医学 | 85篇 |
内科学 | 124篇 |
皮肤病学 | 23篇 |
神经病学 | 21篇 |
特种医学 | 6篇 |
外科学 | 45篇 |
综合类 | 11篇 |
预防医学 | 81篇 |
药学 | 25篇 |
肿瘤学 | 5篇 |
出版年
2023年 | 3篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 9篇 |
2013年 | 14篇 |
2012年 | 7篇 |
2011年 | 8篇 |
2010年 | 16篇 |
2009年 | 14篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 6篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 10篇 |
1998年 | 8篇 |
1997年 | 16篇 |
1996年 | 24篇 |
1995年 | 14篇 |
1994年 | 10篇 |
1993年 | 16篇 |
1992年 | 4篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 16篇 |
1985年 | 10篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1976年 | 3篇 |
1965年 | 3篇 |
1959年 | 14篇 |
1958年 | 31篇 |
1957年 | 24篇 |
1956年 | 21篇 |
1955年 | 22篇 |
1954年 | 23篇 |
1949年 | 2篇 |
1948年 | 15篇 |
1947年 | 2篇 |
1946年 | 3篇 |
排序方式: 共有489条查询结果,搜索用时 501 毫秒
1.
2.
JENNIFER ORLET FISHER PhD DIANE C. MITCHELL MS RD HELEN SMICIKLAS- WRIGHT PhD LEANN LIPPS BIRCH PhD 《Journal of the American Dietetic Association》2002,102(1)
Objective To evaluate parents’ fruit and vegetable intake and their use of pressure to eat in child feeding as predictors of their 5-year-old daughters’ fruit and vegetable, micronutrient, and fat intakes.Subjects Data were obtained from 191 non-Hispanic white families with 5-year-old girls.Design Parent data included reports of pressure in child feeding and their own fruit and vegetable intake. Girls’ intakes of fruits and vegetables, selected micronutrients, and fat were the main outcomes of interest.Statistical analysis Structural equation modeling was used to test a model describing relationships among parents’ fruit and vegetable intake, parents’ use of pressure in child feeding, and daughters’ fruit and vegetable, micronutrient, and fat intakes.Results The model provided a good fit to the data, revealing that girls’ fruit and vegetable intake was positively related to their parents’ reported fruit and vegetable intake. Parents who consumed fewer fruits and vegetables tended to report greater pressure in child feeding and had daughters who consumed fewer fruits and vegetables. Girls’ reported fruit and vegetable intakes were positively related to their micronutrient intakes and negatively associated with fat intake.Applications/conclusions This research demonstrates that parents’ own fruit and vegetable intake may encourage fruit and vegetable intake in their daughters, leading to higher micronutrient intakes and lower dietary fat intakes. Conversely, pressure to eat may discourage fruit and vegetable intake among young girls. J Am Diet Assoc. 2002;102:58–64. 相似文献
3.
4.
5.
Discrepancies Between Perceived Dietary Changes and 4-Day Food Records in Older Adults with Diabetes
6.
C. N. BERNSTEIN L. L. SEEGER P. A. ANTON L. ARTINIAN S. GEFFREY W. GOODMAN T. R. BELIN & F. SHANAHAN 《Alimentary pharmacology & therapeutics》1996,10(5):777-786
Background: Patients with inflammatory bowel disease (IBD) have a high prevalence of osteoporosis. A number of studies have found that corticosteroid use is associated with the development of osteoporosis in these patients. Calcium supplementation may be of benefit in corticosteroid-induced osteoporosis and calcium may be a nutrient that patients with IBD lack. Aim: To test the benefit of calcium supplementation on bone density in a pilot study over a 1-year period, in a group of corticosteroid-using patients with IBD, in a randomized, double-blind, placebo-controlled treatment study. Methods: Corticosteroid-using patients with IBD including males over the age of 18 years and premenopausal females, were randomized to receive either calcium carbonate 1000 mg plus vitamin D 250 IU (Oscal) or an identically matched placebo. Dual energy X-ray absorptiometry measurements of bone density were obtained at entry and at 1 year. At entry, and every 3 months thereafter, serum was collected for the measurement of haemoglobin, biochemistry and bone hormones. Simultaneously a 24-h urine collection was analysed for calcium excretion and creatinine clearance, and a 4-day food record was collected to document dietary calcium and vitamin D ingestion. Results: We found a high prevalence of moderately severe decreased bone density in corticosteroid-using patients with IBD. The dose of prednisone in the year prior to study entry was inversely correlated with bone density at the hip (R=-0.67, P=0.004). At study entry serum osteocalcin was inversely correlated with corticosteroid dose in the year prior to the study (R=-0.64, P=0.02) and at study end, directly correlated with the percentage change in spine bone density (R=0.59, P=0.01). The dietary calcium intake of these patients was close to the current RDA (recommended daily intake) for premenopausal, post-adolescent adults. Calcium supplementation with small extra doses of vitamin D conferred no obvious benefit to bone density at the end of 1 year. There was no correlation between oral calcium ingestion and bone mass measurements. Both the treatment and placebo groups' bone density remained relatively stable at 1 year, suggesting that bone loss in corticosteroid-using patients may peak early into the use of the corticosteroids. Conclusions: Calcium supplementation (1000 mg/day) conferred no significant benefit to bone density at 1 year in patients with corticosteroid-using IBD patients with osteoporosis. Future investigations should explore other therapeutic avenues that may have greater effects on increasing bone density in patients who already have considerable osteoporosis. 相似文献
7.
RAO GHANTA N.; PIEGORSCH WALTER W.; CRAWFORD DENISE D.; EDMONDSON JENNIFER; HASEMAN JOSEPH K. 《Toxicological sciences》1989,13(1):156-164
Sendai virus (SV), mouse hepatitis virus (MHV), and pneumoniavirus of mice (PVM) are common viral infections of mice. Influenceof these viral infections on the prevalence of liver tumors,lung tumors, and lymphoma is of concern in chemical carcinogenicitystudies. Body weight, survival, and tumor prevalence of B6C3F1mice with and without viral infections in 33 male and 34 femaleuntreated control groups and 32 male and 32 female low- andhigh-dose groups of 2-year chemical carcinogenicity studieswere evaluated. In male mice, the SV infection was associatedwith significantly (p < 0.05) higher survival of control,low-dose, and high-dose groups, and higher prevalence of livertumors and lymphoma. The increases in tumor prevalence are possiblydue to an increase in the survival of male mice that had SVinfection. However, when interlaboratory variability and time-relatedeffects were taken into account, the number of significant effectswas consistent with the expected false-positive rate inherentto the statistical procedures. The MHV and PVM infections didnot cause consistent changes in body weight, survival, and tumorprevalences in the control and chemical treatment groups ofmale mice. Viral infections did not cause consistent increasesor decreases in body weight, survival, or tumor prevalence inthe control and chemical treatment groups of female B6C3F1 mice. 相似文献
8.
B. AASTED D. BERNSTEIN D. G. KLAPPER A. EL KHOLY R. M. KRAUSE 《Scandinavian journal of immunology》1979,9(1):61-67
The human lymphokine, leucocyte migration-inhibitory factor (LIF), appears to be a serine esterase and protease by virtue of its susceptibility to the irreversible enzyme inhibitor, phenylmethylsulfonyl fluoride (PMSF), and by the ability of arginine esters and amides to protect LIF against PMSF-induced inactivation. In this paper, three methods are described by which putative substrates for LIF may be investigated. Thus, molecules satisfying the substrate specificities of this lymphokine should (1) protect LIF against inactivation by PMSF, (2) reduce LIF activity in vitro on polymorphonuclear leucocytes, and (3) reduce the esterolytic activity of purified LIF-rich supernatants. The first two reactions were tested by means of the leucocyte migration agarose technique; the third reaction was tested by a sensitive enzyme assay using tritiated tosyl arginine methyl ester as substrate. Guanosine 3',5'-cyclic monophosphoric acid, which is capable of protecting LIF against PMSF-induced inhibition, also inhibited the esterolytic activity of the purified LIF preparation. Four synthetic oligopeptide substrates for trypsin, thombin and plasmin were investigated. Only one, the thrombin- and trypsin-specific benzoyl-phenylalanyl-valyl-agarine-p-nitroanilide, possessed high affinity for the LIF molecule and may therefore prove to be a potent substrate for this lymphokine. 相似文献
9.
JENNIFER M. PARRINGTON GILLIAN CRUICKSHANK D. A. HOPKINSON ELIZABETH B. ROBSON HARRY HARRIS 《Annals of human genetics》1968,32(1):27-32
1. Phosphoglucomutase phenotypes have been studied in several generations of the family of an individual heterozygous at each of the three loci, PGM1, PGM2, and PGM3. 2. PGM1 and PGM2 phenotypes were determined using red cells. Fibroblasts grown in tissue culture were used for PGM3 phenotyping. 3. The family results support the genetical hypothesis based on the analysis of dizygotic twin pairs that the PGM3 isozyme patterns found in the placenta are determined by two alleles, PGM13 and PGM23. 4. Locus PGM3 is not closely linked to locus PGM2 5. The data also support the previous findings that locus PGM1 is not closely linked to PGM2 or PGM3. 相似文献
10.
BASILIO CARLOS M.; TORO AMILCAR; BERNSTEIN JAIME; YOJAY LUNA 《Alcohol and alcoholism (Oxford, Oxfordshire)》1987,22(4):395-400
The effect of nicotinic acid (NA) on sleeping time induced bya single dose of ethanol or pentobarbital was studied in rats.It was found that sleeping time was markedly reduced by NA ina dose-dependent manner. The effect was observed when NA wasadministered 10 min before or after ethanol or pentobarbital,but not when given 60 min in advance. NA did not affect therate of ethanol elimination measured up to 5 hr after ethanoladministration. Rats pretreated with NA 60 min before ethanolslept longer than controls. This latter effect was not observedwith pentobarbital. These observations, together with the knownlack of effect of high liver NAD+ levels on ethanol metabolismand the rather stable NAD+ concentration in brain cells, suggestthat the effect of NA on sleeping time is not mediated by anincrease in ethanol metabolism in liver or by NAD+ or NAD+-dependentreactions in brain. Our results are consistent with a directaction of NA, or some rapidly formed derivative, on a structureor process associated with brain cell functions or membranes. 相似文献