全文获取类型
收费全文 | 1526篇 |
免费 | 73篇 |
国内免费 | 4篇 |
专业分类
儿科学 | 90篇 |
妇产科学 | 142篇 |
基础医学 | 130篇 |
口腔科学 | 31篇 |
临床医学 | 143篇 |
内科学 | 301篇 |
皮肤病学 | 41篇 |
神经病学 | 80篇 |
特种医学 | 259篇 |
外科学 | 105篇 |
综合类 | 33篇 |
预防医学 | 121篇 |
眼科学 | 11篇 |
药学 | 71篇 |
中国医学 | 2篇 |
肿瘤学 | 43篇 |
出版年
2019年 | 6篇 |
2018年 | 14篇 |
2017年 | 16篇 |
2016年 | 10篇 |
2015年 | 13篇 |
2014年 | 25篇 |
2013年 | 24篇 |
2012年 | 35篇 |
2011年 | 26篇 |
2010年 | 49篇 |
2009年 | 53篇 |
2008年 | 49篇 |
2007年 | 50篇 |
2006年 | 44篇 |
2005年 | 36篇 |
2004年 | 46篇 |
2003年 | 45篇 |
2002年 | 37篇 |
2001年 | 36篇 |
2000年 | 35篇 |
1999年 | 38篇 |
1998年 | 55篇 |
1997年 | 70篇 |
1996年 | 54篇 |
1995年 | 54篇 |
1994年 | 59篇 |
1993年 | 56篇 |
1992年 | 21篇 |
1991年 | 24篇 |
1990年 | 26篇 |
1989年 | 52篇 |
1988年 | 52篇 |
1987年 | 39篇 |
1986年 | 33篇 |
1985年 | 32篇 |
1984年 | 17篇 |
1983年 | 29篇 |
1982年 | 19篇 |
1981年 | 21篇 |
1980年 | 23篇 |
1979年 | 14篇 |
1978年 | 15篇 |
1977年 | 17篇 |
1976年 | 12篇 |
1975年 | 23篇 |
1974年 | 8篇 |
1973年 | 10篇 |
1970年 | 10篇 |
1966年 | 5篇 |
1922年 | 7篇 |
排序方式: 共有1603条查询结果,搜索用时 15 毫秒
1.
2.
3.
A. T. Fisk M. Holst K. A. Hobson J. Duffe J. Moisey R. J. Norstrom 《Archives of environmental contamination and toxicology》2002,42(1):118-126
To examine the influence of diet and age on organochlorine contaminant (OC) concentrations in two closely related ringed seal
(Phoca hispida) populations enantiomeric fractions (EFs) of chiral contaminants and stable isotopes of nitrogen (δ15N) and carbon (δ13C) were measured along with OCs in ringed seals collected from the east and west side of the Northwater Polynya. Seals from
these two locations were feeding at the same trophic level based on δ15N values in muscle but had slightly different sources of carbon based on δ13C measurements in muscle. After removing the influence of age, sex, and blubber thickness, OC concentrations did not vary
between ringed seals from the east and west side of the polynya. ΣPCB, ΣDDT, and Σchlordane were found to increase with age
for both male and female seals. The inclusion of older (>20 years) female seals, which may have a reduced reproductive effort,
may influence the relationships in females. Stable isotopes failed to describe OC concentrations in ringed seals suggesting
that diet was not a major factor in variation of OC concentrations within this ringed seal population. Cis- and trans-chlordane, oxychlordane, and heptachlor epoxide were all nonracemic in the ringed seal blubber but did not vary with age,
sex, or collection site. α-HCH appeared racemic (enantiomeric fraction = 0.50 ± 0.01) in the seals, although this EF is different
than those previously observed in their prey species, and was found to vary significantly with age. EF values in the ringed
seals varied considerably from other Arctic marine mammals and seabirds, providing addition evidence that the type(s) and
characteristic(s) of the enzymes involved in biotransformation of chiral OCs vary between these organisms.
Received: 11 April 2001/Accepted: 27 June 2001 相似文献
4.
Hodgkin disease: CT of the thymus 总被引:2,自引:0,他引:2
The computed tomography (CT) scans in two groups of patients with Hodgkin disease were reviewed to determine the frequency of thymic enlargement. In 50 CT scans from 50 patients with evidence of thoracic disease on CT scans who were examined for primary staging, the thymus was enlarged in 15 of 50 (30%). Fifty CT scans were obtained from 44 patients at the time of 50 separate episodes of known or suspected relapse. Relapse occurred in the mediastinum in 12 episodes, lung parenchyma in five, and both sites in one. Thymic enlargement thought to be due to involvement by disease was present in seven of 18 (38%). Mediastinal disease was associated with thymic enlargement in all but one patient in whom a thymic cyst developed after radiation therapy. Differentiation of thymic enlargement from enlarged superior mediastinal lymph nodes was easily made in all but two patients. Thymic enlargement in the absence of lymph node enlargement may indicate a different disease, since isolated Hodgkin disease of the thymus is uncommon. Primary thymic tumor should be considered initially, whereas after treatment, rebound hyperplasia of the thymus may be the cause of enlargement. 相似文献
5.
N M Fisk D Ronderos-Dumit Y Tannirandorn U Nicolini D Talbert C H Rodeck 《British journal of obstetrics and gynaecology》1992,99(1):18-22
OBJECTIVE: To characterize amniotic pressure (AP) in pregnancies with normal amniotic fluid volume. DESIGN: Observational study, mainly cross-sectional. SETTING: Fetal medicine unit within a tertiary referral hospital. SUBJECTS: Patients undergoing transamniotic invasive procedures in whom amniotic fluid volume was subjectively assessed as normal on ultrasound. Those beyond 16 weeks with a deepest vertical pool on ultrasound less than 3.0 or greater than 8.0 cm were excluded. Overall 194 pregnancies were studied on 232 occasions between 7 and 38 weeks gestation. INTERVENTIONS: Manometry readings referenced to the top of the maternal abdomen were obtained via a fluid-filled line from the needle hub and either connected to a pressure transducer (n = 190) or held vertically against a ruler (n = 42). MAIN OUTCOME MEASURES: AP in mm Hg, AP corrected for gestational age (z scores), semi-quantitative ultrasonic indices of amniotic fluid volume, clinical variables. RESULTS: AP in singleton pregnancies increased with advancing gestation (P less than 0.001), and the sigmoid-shaped regression curve plateaued in the mid-trimester. AP z scores were not influenced by volume-related phenomena such as twin gestation, the deepest vertical pool, or amniotic fluid index, nor by maternal age, parity, gravidity, fetal sex, or subsequent spontaneous preterm delivery. CONCLUSIONS: These findings suggest that AP is not principally determined by intrauterine volume. We speculate that AP, which reflects change in uterine tension as a function of radius, may instead be determined by gestation-specific anatomical and hormonal influences on gravid uterine musculature. A reference range for AP has been constructed for use in amnioinfusion and amnioreduction procedures. 相似文献
6.
M J O Taylor L Y Wee M L Denbow N M Fisk 《Ultrasound in obstetrics & gynecology》2004,24(4):479; author reply 479-479; author reply 481
7.
A randomized controlled trial of electromagnetic therapy in the primary care management of venous leg ulceration 总被引:1,自引:1,他引:0
OBJECTIVE: The aim was to establish the potential efficacy, tolerabilityand side-effect profile of electromagnetic therapy as an adjunctto conventional dressings in the treatment of venous leg ulcers. METHOD: A prospective, randomized, double blind controlled clinicaltrial was carried out in a dedicated leg ulcer clinic basedin one urban general practice. Nineteen patients with leg ulcersof confirmed venous aetiology were assessed. The main outcomemeasures were rate and scale of venous leg ulcer healing, changesin patient-reported pain levels, quality of life, degree ofmobility, side effect profile and acceptability to patientsand staff. RESULTS: Sixty-eight per cent of patients attending this dedicated clinicachieved improvements in the size of their ulcer (4, 21%, healedfully) and in reduced pain levels (P < 0.05) during the trial,despite the chronicity of ulcer histories. Patients treatedwith electromagnetic therapy at 800 Hz were found at day 50to have significantly greater healing (P < 0.05) and paincontrol (P < 0.05) than placebo therapy or treatment with600 Hz. All patients reported improved mobility at the end ofthe study. The electromagnetic therapy was well tolerated bypatients, with no differences between groups in reporting adverseevents, and proved acceptable to staff. CONCLUSION: Despite the small numbers in this pilot study, electromagnetictherapy provided significant gains in the healing of venousleg ulcers and reduction in pain. Keywords. Electromagnetic therapy, RCT, leg ulcers, primary care. 相似文献
8.
9.
Isolation, regulation, and DNA-binding properties of three Drosophila nuclear hormone receptor superfamily members. 总被引:2,自引:0,他引:2 下载免费PDF全文
G J Fisk C S Thummel 《Proceedings of the National Academy of Sciences of the United States of America》1995,92(23):10604-10608
We have designed a rapid cloning and screening strategy to identify new members of the nuclear hormone receptor superfamily that are expressed during the onset of Drosophila metamorphosis. Using this approach, we isolated three Drosophila genes, designated DHR38, DHR78, and DHR96. All three genes are expressed throughout third-instar larval and prepupal development. DHR38 is the Drosophila homolog of NGFI-B and binds specifically to an NGFI-B response element. DHR78 and DHR96 are orphan receptor genes. DHR78 is induced by 20-hydroxyecdysone (20E) in cultured larval organs, and its encoded protein binds to two AGGTCA half-sites arranged as either direct or palindromic repeats. DHR96 is also 20E-inducible, and its encoded protein binds selectively to the hsp27 20E response element. The 20E receptor can bind to each of the sequences recognized by DHR78 and DHR96, indicating that these proteins may compete with the receptor for binding to a common set of target sequences. 相似文献
10.
Hormonal fluctuations associated with the menstrual cycle influence
appetite control and eating behaviour. Energy intake varies during the
reproductive cycle in humans and animals, with a periovulatory nadir and a
luteal phase peak. Patterns of macronutrient selection show less
consistency but a number of studies report carbohydrate cravings in the
premenstrual phase, particularly in women with premenstrual syndrome. The
cyclical nature of food cravings are frequently, but not invariably,
associated with depression. Fluctuations in appetite, cravings and energy
intake during the menstrual cycle may occur in parallel with cyclical
rhythms in serotonin, which can be accompanied by affective symptoms. The
premenstrual phase can be considered as a time when women are especially
vulnerable to overconsumption, food craving and depression; this is often
associated with low serotonin activity.
相似文献