全文获取类型
收费全文 | 5762篇 |
免费 | 218篇 |
国内免费 | 42篇 |
专业分类
耳鼻咽喉 | 97篇 |
儿科学 | 143篇 |
妇产科学 | 90篇 |
基础医学 | 784篇 |
口腔科学 | 677篇 |
临床医学 | 421篇 |
内科学 | 1106篇 |
皮肤病学 | 140篇 |
神经病学 | 338篇 |
特种医学 | 190篇 |
外科学 | 612篇 |
综合类 | 37篇 |
一般理论 | 2篇 |
预防医学 | 676篇 |
眼科学 | 93篇 |
药学 | 380篇 |
2篇 | |
中国医学 | 58篇 |
肿瘤学 | 176篇 |
出版年
2024年 | 32篇 |
2023年 | 57篇 |
2022年 | 130篇 |
2021年 | 248篇 |
2020年 | 158篇 |
2019年 | 204篇 |
2018年 | 273篇 |
2017年 | 165篇 |
2016年 | 216篇 |
2015年 | 214篇 |
2014年 | 288篇 |
2013年 | 298篇 |
2012年 | 463篇 |
2011年 | 519篇 |
2010年 | 318篇 |
2009年 | 213篇 |
2008年 | 330篇 |
2007年 | 293篇 |
2006年 | 242篇 |
2005年 | 207篇 |
2004年 | 165篇 |
2003年 | 144篇 |
2002年 | 132篇 |
2001年 | 79篇 |
2000年 | 78篇 |
1999年 | 50篇 |
1998年 | 49篇 |
1997年 | 39篇 |
1996年 | 33篇 |
1995年 | 35篇 |
1994年 | 24篇 |
1993年 | 30篇 |
1992年 | 26篇 |
1991年 | 23篇 |
1990年 | 21篇 |
1989年 | 29篇 |
1988年 | 22篇 |
1987年 | 21篇 |
1986年 | 22篇 |
1985年 | 20篇 |
1984年 | 11篇 |
1983年 | 15篇 |
1982年 | 9篇 |
1981年 | 15篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 11篇 |
1976年 | 7篇 |
1969年 | 7篇 |
排序方式: 共有6022条查询结果,搜索用时 15 毫秒
91.
Van de Velde H; De Vos A; Joris H; Nagy ZP; Van Steirteghem AC 《Human reproduction (Oxford, England)》1998,13(11):3160-3164
In human in-vitro fertilization (IVF), the oocytes are surrounded by
cumulus and corona cells at the time of insemination so that their maturity
cannot easily be evaluated. The best IVF results are obtained if the
oocytes are inseminated 2-6 h after retrieval. In the intracytoplasmic
sperm injection (ICSI) procedure, the oocytes are denuded by enzymatic and
mechanical treatment in order to be able to perform the injection. As a
consequence, the nuclear maturity of the oocytes can be evaluated and only
those that have extruded the first polar body are injected. However,
metaphase-II oocytes that have not yet reached cytoplasmic maturity cannot
be recognized. The purpose of this study was to investigate the effect of
different timing of cumulus- corona cell removal and injection on the
outcome of ICSI. For this we allowed the oocytes to complete in-vitro
cytoplasmic maturation in two different culture conditions: (i) surrounded
by their cumulus and corona cells or (ii) totally denuded. We performed
three different studies on sibling oocytes obtained after a standardized
buserelin/human menopausal gonadotrophin (HMG) protocol. We investigated
the effect of early (1-2 h after retrieval) and late (5-6 h after
retrieval) oocyte denudation and injection on the survival and
fertilization of the injected oocytes and on embryo cleavage after
fertilization. We found no statistically significant differences between
early and late injection, indicating that after a standardized
buserelin/HMG protocol the metaphase-II oocytes do not need time for
further cytoplasmic maturation. Furthermore, a different timing of
cumulus-corona cell removal has no effect on the outcome of ICSI,
suggesting that the surrounding cells are not necessary for survival,
fertilization and cleavage after ICSI.
相似文献
92.
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
93.
NJ Hoogenraad JD Mitchell NA Don TM Sutherland AC Mc Leay 《Archives of disease in childhood》1980,55(4):292-295
The activity of urea cycle enzymes was assayed in duodenal biopsy specimens obtained from a female infant who presented with neonatal hyperammonaemia. All enzyme levels were normal except N-acetyl glutamate-dependent carbamyl phosphate synthetase 1 (CPS1) which was half the mean activity in normal control specimens. A similar deficiency of CPS1 was also shown in duodenal specimens from the patient's mother who became slightly symptomatic after relatively high protein meals and during pregnancy, and had spontaneously modified her diet to one with protein restriction. The patient is growing normally on a dietary regimen similar to that spontaneously adopted by her mother. Urea cycle enzyme activity in the duodenal biopsy material from the controls was similar to that found in the normal human liver and appears to have distinct advantages as a means of assaying for urea cycle defects in patients with hyperammonaemia and their relatives. 相似文献
94.
This study was designed to investigate: the prevalence of smokers among the UNIFESP nursing undergraduate students; some initial usage features; the smokers' dependence degree on nicotine. In order to compare the ratio of some variables, Pearson's Square Chi test was applied. The number of smokers among the nursing undergraduate students in the sample was 23 (8.2%) and 167 (59.9%) said they had never smoked a cigarette. Smokers' average age was 19.5 years old, and there is a significant difference between genders and only 2 (9.1%) smoking students may show a more severe discomfort while attempting to stop smoking, as showed the Fagerstr?m's Test. 相似文献
95.
Alves H Kessler F Ratto LR 《Revista brasileira de psiquiatria (S?o Paulo, Brazil : 1999)》2004,26(Z1):S51-S53
Alcohol related disorders often coexist with other psychiatric disorders and its incidence is increasing in last decades. Studies show that patients with comorbidity, specially those with severe psychiatric disorders, have higher rates of suicide, relapse, money spent in treatment, homeless and they use more medical service. Their evaluation must be meticulous because the differential diagnosis become complicated without a long period of alcohol withdrawal. These patients have a worse prognostic and their treatment is more difficult. Most of studies in this area have indicated that the integration of psychosocial and pharmacological techniques is more effective. The long term treatment must focus in the reduction of symptoms, improvement of social and familiar functioning, coping skills and relapse prevention. 相似文献
96.
97.
98.
Glucose and glutamine metabolism of two microregions of human infiltrating ductile breast cancer, the center and the periphery, was studied and the results were compared with those of healthy mammary glands. In general, the activities of glycolytic enzymes and of phosphate-dependent glutaminase were as follows: center>periphery>mammary gland. Insulin caused a marked increase of glucose consumption and lactate production by incubated slices of mammary gland but had no effect on both microregions of the tumor. Therefore, human breast cancer presents metabolic microregions. 相似文献
99.
100.
Analgesia and c-Fos expression in the periaqueductal gray induced by electroacupuncture at the Zusanli point in rats 总被引:3,自引:0,他引:3
The need to use anaesthetised or restrained animals in acupuncture research in laboratory animals may represent a confounding variable, since both anaesthesia and stress alter the pain threshold and the activity of pain-related brain areas. In the current study we assessed the participation of the periaqueductal gray (PAG) in electroacupuncture's (EA) analgesic effects applied to the Zusanli point (36S) under carefully controlled stress conditions. Repeated immobilisation protocols (6 days, 1 h/day and 13 days, 2 h/day) were used to diminish the influence of acute immobilisation stress on c-Fos expression and analgesia (tail-flick test) induced by electroacupuncture on the 36S point (EA36S). Animals submitted to immobilisation alone (IMMO) or to electroacupuncture (100 Hz, 2-4 V, faradic wave) on a non-point region (EANP) were compared with animals submitted to electroacupuncture on the 36S point. In animals not previously submitted to repeated immobilisation, electroacupuncture on the 36S point induced analgesia and c-Fos expression in the PAG was not different from that induced by electroacupuncture at a non-acupuncture point. In animals submitted to repeated immobilisation (repeated immobilisation for 6 days or repeated immobilisation for 13 days), however, electroacupuncture on point 36S led to higher levels of analgesia and c-Fos expression, specifically in the ventrolateral PAG (vlPAG), as compared with animal groups subjected only to immobilisation or to electroacupuncture on a non-point. Our findings endorse previous results, and point to a specific part of the PAG involved in the effects of electroacupuncture at the Zusanli point. 相似文献