全文获取类型
收费全文 | 1490篇 |
免费 | 161篇 |
国内免费 | 24篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 82篇 |
妇产科学 | 30篇 |
基础医学 | 284篇 |
口腔科学 | 18篇 |
临床医学 | 184篇 |
内科学 | 266篇 |
皮肤病学 | 19篇 |
神经病学 | 76篇 |
特种医学 | 171篇 |
外科学 | 159篇 |
综合类 | 29篇 |
预防医学 | 151篇 |
眼科学 | 7篇 |
药学 | 91篇 |
中国医学 | 2篇 |
肿瘤学 | 103篇 |
出版年
2021年 | 16篇 |
2020年 | 13篇 |
2019年 | 16篇 |
2018年 | 20篇 |
2017年 | 14篇 |
2016年 | 14篇 |
2015年 | 23篇 |
2014年 | 43篇 |
2013年 | 51篇 |
2012年 | 62篇 |
2011年 | 65篇 |
2010年 | 59篇 |
2009年 | 41篇 |
2008年 | 45篇 |
2007年 | 60篇 |
2006年 | 57篇 |
2005年 | 54篇 |
2004年 | 47篇 |
2003年 | 41篇 |
2002年 | 40篇 |
2001年 | 38篇 |
2000年 | 31篇 |
1999年 | 50篇 |
1998年 | 64篇 |
1997年 | 51篇 |
1996年 | 45篇 |
1995年 | 26篇 |
1994年 | 30篇 |
1993年 | 19篇 |
1992年 | 34篇 |
1991年 | 42篇 |
1990年 | 46篇 |
1989年 | 34篇 |
1988年 | 48篇 |
1987年 | 54篇 |
1986年 | 25篇 |
1985年 | 21篇 |
1984年 | 38篇 |
1983年 | 18篇 |
1982年 | 20篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1974年 | 10篇 |
1973年 | 12篇 |
1971年 | 9篇 |
1969年 | 8篇 |
排序方式: 共有1675条查询结果,搜索用时 0 毫秒
71.
Swanson KS Grieshop CM Flickinger EA Bauer LL Healy HP Dawson KA Merchen NR Fahey GC 《The Journal of nutrition》2002,132(5):980-989
The goal of this study was to examine whether supplemental fructooligosaccharides (FOS) and (or) mannanoligosaccharides (MOS) influenced indices of gut health of dogs. Adult female dogs (n = 4) surgically fitted with ileal cannulas were fed a dry, extruded, kibble diet twice daily. At each feeding, the following treatments were administered: 1) Control (no FOS or MOS); 2) 1 g FOS; 3) 1 g MOS; or 4) 1 g FOS + 1 g MOS. Fecal, ileal and blood samples were collected during the last 4 d of each 14-d period to measure protein catabolite concentrations, microbial populations, immune characteristics and nutrient digestibilities. Treatment means were compared using preplanned orthogonal contrasts. Dogs supplemented with MOS had lower (P = 0.05) fecal total aerobes and tended to have greater (P = 0.13) Lactobacillus populations. Ileal immunoglobulin (Ig) A concentrations were greater (P = 0.05) in dogs supplemented with FOS + MOS vs. control. Lymphocytes (% of total white blood cells) were greater (P < 0.05) in dogs supplemented with MOS. Serum IgA concentrations also tended (P = 0.13) to be greater in dogs supplemented with MOS. Dogs supplemented with FOS and FOS + MOS had lower (P < 0.05) fecal total indole and phenol concentrations. Dogs supplemented with MOS tended to have lower ileal DM (P = 0.149) and OM (P = 0.146) digestibilities vs. control. Results of this study suggest that dietary supplementation of FOS and MOS may have beneficial effects on colonic health and immune status of dogs. 相似文献
72.
73.
Fahey JW Haristoy X Dolan PM Kensler TW Scholtus I Stephenson KK Talalay P Lozniewski A 《Proceedings of the National Academy of Sciences of the United States of America》2002,99(11):7610-7615
Gastric infection with Helicobacter pylori is a cosmopolitan problem, and is especially common in developing regions where there is also a high prevalence of gastric cancer. These infections are known to cause gastritis and peptic ulcers, and dramatically enhance the risk of gastric cancer. Eradication of this organism is an important medical goal that is complicated by the development of resistance to conventional antimicrobial agents and by the persistence of a low level reservoir of H. pylori within gastric epithelial cells. Moreover, economic and practical problems preclude widespread and intensive use of antibiotics in most developing regions. We have found that sulforaphane [(-)-1-isothiocyanato-(4R)-(methylsulfinyl)butane], an isothiocyanate abundant as its glucosinolate precursor in certain varieties of broccoli and broccoli sprouts, is a potent bacteriostatic agent against 3 reference strains and 45 clinical isolates of H. pylori [minimal inhibitory concentration (MIC) for 90% of the strains is 相似文献
74.
Andrew E Springer BJ Selwyn Steven H Kelder 《BMC international health and human rights》2006,6(1):3-11
Background
Adolescence is an important stage of life for establishing healthy behaviors, attitudes, and lifestyles that contribute to current and future health. Health risk behavior is one indicator of health of young people that may serve both as a measure of health over time as well as a target for health policies and programs. This study examined the prevalence and distribution of youth health risk behaviors from five risk behavior domains–aggression, victimization, depression and suicidal ideation, substance use, and sexual behaviors–among public secondary school students in central El Salvador. 相似文献75.
76.
Perkins SN; Hursting SD; Haines DC; James SJ; Miller BJ; Phang JM 《Carcinogenesis》1997,18(5):989-994
Transgenic mice with both alleles of the p53 tumor suppressor gene product
'knocked out' by gene targeting are susceptible to early development of
tumors, chiefly lymphomas and sarcomas. Compared with the control group,
administration of dehydroepiandrosterone (DHEA) at 0.3% of the diet to male
p53-deficient mice extended their lifespan by delaying death due to
neoplasms (from 105 to 166 days on study, P = 0.002), primarily by
suppressing lymphoblastic lymphoma (from 45 to 6% of neoplastic deaths, P =
0.010). Treatment with a synthetic DHEA analog,
16alpha-fluoro-5-androsten-17-one (compound 8354), at 0.15% of the diet
also increased lifespan, to 140 days for mice that developed tumors (P =
0.037). The effects of these steroids on lifespan and tumor development did
not appear to be strongly related to inhibition of food consumption and
weight gain, in that a group pair-fed with control diet to the reduced food
consumption of the DHEA-treated group developed and died of the same types
of neoplasms at the same rate as the controls fed ad libitum. The
chemopreventive effect of these steroids has been proposed to be due to
suppression of DNA synthesis by inhibition of glucose 6-phosphate
dehydrogenase, the rate-limiting enzyme of the pentose phosphate pathway.
Although DHEA and its analog are strong non- competitive inhibitors of this
enzyme in vitro, treatment with DHEA did not deplete cellular nucleotide
pools in the liver, as would have been predicted. The chemopreventive
effect of DHEA in this model may be due to steroid-induced thymic atrophy
and suppression of T cell lymphoma, permitting these mice to survive long
enough to develop tumors with longer latency.
相似文献
77.
Child Behaviour Checklist classification of behaviour disorder 总被引:1,自引:0,他引:1
TM NOLAN L BOND R ADLER L LITTLEFIELD P BIRLESON K MARRIAGE A MAWDSLEY R SALO BJ TONGE 《Journal of paediatrics and child health》1996,32(5):405-411
Objective : The aim of this study was to determine the applicability of the published clinical cut-off scores of the Child Behaviour Checklist (CBCL) for the classification of behaviour disorders.
Methodology : Child Behaviour Checklists were obtained for 1342 subjects newly referred to the six major mental health centres in Melbourne. The normative community sample of 1002 7-, 12- and 15-year-olds was drawn from a school-based asthma prevalence study.
Results : The mean total problem T-score for the children referred to mental health centres was 67 and was above the clinical range for all age groups. Using referral to psychiatric services as the gold standard, the sensitivity and specificity of the CBCL using a cut-off of ≥ 60, was 77.4 and 83.2%, respectively. This compares favourably with the sensitivity of 68% and specificity of 82% for the American sample. Using a cut-off score of ≥ 63, the sensitivity was 70.5% and the specificity was 88.6%. The referred and community samples differed with respect to socio-economic status, family structure and mothers' level of education. Fifty-two per cent of the clinically referred children lived with both parents, compared with 89% of the community sample.
Conclusions : While there are some limitations to this study in terms of both the clinic and community sample, support is provided for the usefulness and applicability of the recommended CBCL cut-off scores in an Australian population. 相似文献
Methodology : Child Behaviour Checklists were obtained for 1342 subjects newly referred to the six major mental health centres in Melbourne. The normative community sample of 1002 7-, 12- and 15-year-olds was drawn from a school-based asthma prevalence study.
Results : The mean total problem T-score for the children referred to mental health centres was 67 and was above the clinical range for all age groups. Using referral to psychiatric services as the gold standard, the sensitivity and specificity of the CBCL using a cut-off of ≥ 60, was 77.4 and 83.2%, respectively. This compares favourably with the sensitivity of 68% and specificity of 82% for the American sample. Using a cut-off score of ≥ 63, the sensitivity was 70.5% and the specificity was 88.6%. The referred and community samples differed with respect to socio-economic status, family structure and mothers' level of education. Fifty-two per cent of the clinically referred children lived with both parents, compared with 89% of the community sample.
Conclusions : While there are some limitations to this study in terms of both the clinic and community sample, support is provided for the usefulness and applicability of the recommended CBCL cut-off scores in an Australian population. 相似文献
78.
Cocaine use in pregnancy in Amsterdam 总被引:1,自引:0,他引:1
BJ Smit K Boer AM van Huis ISE Lie-A-Ling SC Schmidt 《Acta paediatrica (Oslo, Norway : 1992)》1994,83(S404):32-35
To study the effects of cocaine use in pregnancy in Amsterdam, clinical data on cocaine-using pregnant women ( n = 21) and their offspring ( n = 23) were obtained retrospectively (1987–1994) at the Academic Medical Center, Amsterdam. Infants exposed to cocaine had a median gestational age of 39 weeks and a median birth weight of 3090 g. There were six preterm infants, two small-for-gestational-age infants and five infants with a small head circumference. Three infants had a congenital malformation. One infant (Potter's syndrome) died shortly before birth. One infant had congenital syphilis, four had intracerebral abnormalities on ultrasound and four had abnormal neurologic symptoms in the neonatal period. One infant died after 21 days of life. At follow-up four infants showed abnormal development. In 12 of the 23 infants (52%), one or more possible effects of cocaine were found. 相似文献
79.
Substance use in pregnancy: do we care? 总被引:3,自引:0,他引:3
Two cohorts of substance-using women were compared retrospectively. From 1969 to 1979 a very high perinatal mortality rate (PMR 9.8%) was found among 92 polydrug-using women (1 twin excluded). Preterm delivery occurred in 25% of all pregnancies and in 30% of the children birth weight was below the 10th percentile. Nineteen women using heroin only had a worse fetal outcome (PMR 32%, preterm delivery in 47%, birth weight < 10th percentile in 42%). These results led to a strict surveillance system. In the period 1980–1989, 240 women (4 twins excluded) delivered after 16 weeks. Total fetal loss decreased to 2.1% and PMR to 0.4%, which was similar to results in controls. However, 22% of the women still delivered before 37 weeks and 27% delivered a child < 10th percentile. Methadone-using women were able to halve their dosage during pregnancy and 16 were detoxified. Multivariate analysis within the substance users of the second cohort showed that the neonatal abstinence syndrome, but not the (registered) amount of opiates used, was related to a lower birth weight. Not coping with prenatal care was related to a shorter pregnancy length. Multivariate analysis, including the controls, showed a significant relation of birth weight (345 g lower) with substance use. Also, head circumference was 0.8 cm smaller. Length of pregnancy however was related to smoking. This study shows that it is difficult to make substance users attend prenatal care, but also that women coping with prenatal care reduce substance intake. Opiate use might be responsible for lower birth weight, although not in a clear dose–response relationship, whereas lifestyle, as represented by not coping with prenatal care and the quantity of cigarette smoking, shortens the length of pregnancy. 相似文献
80.
Ethnic differences in serum pepsinogen levels among Japanese and non-Japanese Brazilian gastric cancer patients and controls 总被引:5,自引:0,他引:5
Fahey MT Hamada GS Nishimoto IN Kowalski LP Iriya K Gama-Rodrigues JJ Tsugane S 《Cancer Detection and Prevention》2000,24(6):564-571
A low level of serum pepsinogen I (Pg I) is a risk factor for gastric cancer (GC); low levels of Pg I and the pepsinogen ratio (Pg I:Pg II) are correlated with chronic atrophic gastritis. We report serum Pg levels and compare the degree of association with GC among Japanese and non-Japanese Brazilians. Sera were cross-sectionally ascertained from 93 Japanese Brazilian patients category matched by age and sex with 110 controls, and 228 non-Japanese Brazilian patients individually matched by age and sex with one control. Among non-Japanese Brazilians, GC was associated with a Pg I level <30 ng/ml (odds ratio [OR], 2.5; 95% confidence interval [CI], 1.7-3.8) and a Pg I:Pg II ratio < 3.0 (OR, 3.4; 95% CI, 2.2-5.3). However, among Japanese Brazilians, the association was present with a level of Pg I < 30 ng/ml (OR, 3.5; 95% CI, 1.9-6.3), and was weak with a Pg I:Pg II ratio < 3.0 (OR, 1.3; 95% CI, 0.73-2.4). Serum Pg I may be preferred to the Pg I:Pg II ratio to study the association between Pg and GC among Japanese Brazilians. 相似文献