全文获取类型
收费全文 | 2980篇 |
免费 | 188篇 |
国内免费 | 12篇 |
专业分类
耳鼻咽喉 | 17篇 |
儿科学 | 200篇 |
妇产科学 | 61篇 |
基础医学 | 473篇 |
口腔科学 | 117篇 |
临床医学 | 258篇 |
内科学 | 534篇 |
皮肤病学 | 165篇 |
神经病学 | 295篇 |
特种医学 | 84篇 |
外科学 | 303篇 |
综合类 | 16篇 |
一般理论 | 2篇 |
预防医学 | 240篇 |
眼科学 | 28篇 |
药学 | 214篇 |
中国医学 | 4篇 |
肿瘤学 | 169篇 |
出版年
2023年 | 12篇 |
2022年 | 31篇 |
2021年 | 53篇 |
2020年 | 46篇 |
2019年 | 60篇 |
2018年 | 69篇 |
2017年 | 59篇 |
2016年 | 73篇 |
2015年 | 65篇 |
2014年 | 109篇 |
2013年 | 151篇 |
2012年 | 195篇 |
2011年 | 205篇 |
2010年 | 108篇 |
2009年 | 98篇 |
2008年 | 189篇 |
2007年 | 208篇 |
2006年 | 192篇 |
2005年 | 163篇 |
2004年 | 181篇 |
2003年 | 143篇 |
2002年 | 161篇 |
2001年 | 53篇 |
2000年 | 44篇 |
1999年 | 43篇 |
1998年 | 32篇 |
1997年 | 48篇 |
1996年 | 30篇 |
1995年 | 42篇 |
1994年 | 23篇 |
1993年 | 26篇 |
1992年 | 40篇 |
1991年 | 31篇 |
1990年 | 18篇 |
1989年 | 16篇 |
1988年 | 19篇 |
1987年 | 9篇 |
1986年 | 13篇 |
1985年 | 8篇 |
1984年 | 23篇 |
1983年 | 14篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1963年 | 4篇 |
排序方式: 共有3180条查询结果,搜索用时 31 毫秒
41.
Markus Mattila Leena Hakola Sari Niinist Heli Tapanainen Hanna-Mari Takkinen Suvi Ahonen Jorma Ilonen Jorma Toppari Riitta Veijola Mikael Knip Suvi M. Virtanen 《Nutrients》2021,13(3)
Our aim was to study the associations between maternal vitamin C and iron intake during pregnancy and the offspring’s risk of developing islet autoimmunity and type 1 diabetes. The study was a part of the Finnish Type 1 Diabetes Prediction and Prevention (DIPP) prospective birth cohort including children genetically at risk of type 1 diabetes born between 1997–2004. The diets of 4879 mothers in late pregnancy were assessed with a validated food frequency questionnaire. The outcomes were islet autoimmunity and type 1 diabetes. Cox proportional hazards regression analysis adjusted for energy, family history of diabetes, human leukocyte antigen (HLA) genotype and sex was used for statistical analyses. Total intake of vitamin C or iron from food and supplements was not associated with the risk of islet autoimmunity (vitamin C: HR 0.91: 95% CI (0.80, 1.03), iron: 0.98 (0.87, 1.10)) or type 1 diabetes (vitamin C: 1.01 (0.87, 1.17), iron: 0.92 (0.78, 1.08)), neither was the use of vitamin C or iron supplements associated with the outcomes. In conclusion, no association was found between maternal vitamin C or iron intake during pregnancy and the risk of islet autoimmunity or type 1 diabetes in the offspring. 相似文献
42.
43.
Effects of chronic treatment with valproate on serotonin-1A receptor binding and function 总被引:1,自引:0,他引:1
Valproate is effective in treating bipolar disorder characterized by rapid cycling or acute mania, although the mechanism of action is unclear. In contrast to other treatments for depression, 21 days of treatment in rats with valproate (100, 200 or 400 mg/kg) did not significantly alter the hypothermia induced by 8-hydroxy-2-(di-n-propyl)aminotetralin (8-OH-DPAT), an agonist at serotonin-1A receptors. Treatment with valproate also had no effect on radioligand binding to serotonin-1A, serotonin-2 or -adrenergic receptors. Based on these animal studies in frontal cortex and hippocampus, the therapeutic benefit of valproate in mood disorders does not appear to involve adaptive changes in serotonin-1A, serotonin-2 or -adrenergic receptor number. 相似文献
44.
Customer exposure to MTBE, TAME, C6 alkyl methyl ethers, and benzene during gasoline refueling. 总被引:2,自引:1,他引:1
下载免费PDF全文
![点击此处可从《Environmental health perspectives》网站下载免费的PDF全文](/ch/ext_images/free.gif)
S Vainiotalo Y Peltonen A Ruonakangas P Pfffli 《Environmental health perspectives》1999,107(2):133-140
We studied customer exposure during refueling by collecting air samples from customers' breathing zone. The measurements were carried out during 4 days in summer 1996 at two Finnish self-service gasoline stations with "stage I" vapor recovery systems. The 95-RON (research octane number) gasoline contained approximately 2.7% methyl tert-butyl ether (MTBE), approximately 8.5% tert-amyl methyl ether (TAME), approximately 3.2% C6 alkyl methyl ethers (C6 AMEs), and 0.75% benzene. The individual exposure concentrations showed a wide log-normal distribution, with low exposures being the most frequent. In over 90% of the samples, the concentration of MTBE was higher (range <0.02-51 mg/m3) than that of TAME. The MTBE values were well below the short-term (15 min) threshold limits set for occupational exposure (250-360 mg/m3). At station A, the geometric mean concentrations in individual samples were 3.9 mg/m3 MTBE and 2. 2 mg/m3 TAME. The corresponding values at station B were 2.4 and 1.7 mg/m3, respectively. The average refueling (sampling) time was 63 sec at station A and 74 sec at station B. No statistically significant difference was observed in customer exposures between the two service stations. The overall geometric means (n = 167) for an adjusted 1-min refueling time were 3.3 mg/m3 MTBE and 1.9 mg/m3 TAME. Each day an integrated breathing zone sample was also collected, corresponding to an arithmetic mean of 20-21 refuelings. The overall arithmetic mean concentrations in the integrated samples (n = 8) were 0.90 mg/m3 for benzene and 0.56 mg/m3 for C6 AMEs calculated as a group. Mean MTBE concentrations in ambient air (a stationary point in the middle of the pump island) were 0.16 mg/m3 for station A and 0.07 mg/m3 for station B. The mean ambient concentrations of TAME, C6 AMEs, and benzene were 0.031 mg/m3, approximately 0.005 mg/m3, and approximately 0.01 mg/m3, respectively, at both stations. The mean wind speed was 1.4 m/sec and mean air temperature was 21 degreesC. Of the gasoline refueled during the study, 75% was 95 grade and 25% was 98/99 grade, with an oxygenate (MTBE) content of 12.2%. 相似文献
45.
FLFQPQRF-NH2 (F8Famide; morphine-modulating peptide), isolated from bovine brain, is an FMRFamide-like peptide with opioid analgesia modulating effects. In the rat brain, F8Famide is immunohistochemically localized in neurons of the medial hypothalamus and medulla oblongata. Neuropeptide Y (NPY) is structurally related to F8Famide and the mammalian FMRFamide-like immunoreactivity (LI) was once thought to be due to an NPY-like peptide. We compared the anatomical distribution of F8Famide-LI with the localization of enkephalin- and NPY-LI-containing structures in the rat brain to find out if NPY or enkephalins coexist with F8Famide-LI. Cryostat sections of colchicine-treated Wistar rat brains were incubated with specific antisera against F8Famide, NPY, YGGFMRGL (Met-enkephalin-Arg-Gly-Leu), or YGGFMRF (Met-enkephalin-Arg-Phe) raised in rabbits. The immunoreactivity was visualized by the peroxidase - antiperoxidase or immunofluorescence method. The light microscopic mirror method was applied to study the colocalization of F8Famide and NPY. The F8Famide-immunoreactivity was concentrated in smaller areas of medial hypothalamus and nucleus of the solitary tract than that of enkephalins and NPY. In all brain areas, the distributions of F8Famide-, enkephalin- and NPY-immunoreactive neurons were distinct. F8Famide-, NPY- and enkephalin-LI-containing nerve terminals were seen in the nucleus of the solitary tract and in the lateral parabrachial nucleus. These results show that the neuronal systems containing F8Famide-, enkephalin- or NPY-LI are anatomically separate in all brain regions. However, there are terminal areas in which more than one type of these immunoreactivities are detected. These results have anatomical correlation with pharmacological reports, suggesting modulatory functions for these peptides on regulation of blood pressure, feeding behaviour and endocrine functions. 相似文献
46.
In this cross-sectional study, we evaluated the cervical spine in patients with diastrophic dysplasia (DD) by using magnetic resonance imaging (MRI). From 90 (57 female, 33 male) patients of different ages (0.3-56.0 years), T1- and T2-weighted images were obtained. The craniocervical junction and status of the medulla were examined, and the transverse areas of dural tube and medulla were measured. Alignment of the cervical spine, vertebral abnormalities, and disc changes also were evaluated. The cervical spinal canal was moderately narrowed, particularly in adults. The transverse areas of the medulla and especially of the dural tube were smaller compared with a normal population (p < 0.0001). There was no stenosis of the foramen magnum in patients with DD, but the spinal canal was narrowed. Degenerative changes were common. In all age groups, intervertebral discs were dark and disc heights were narrowed. Three (3%) patients (two children, one adult) had cervical kyphosis. Compression of the medulla was noted in association with severe cervical kyphosis in one child and one adult. Typical findings of the cervical spine in DD were exceptionally wide foramen magnum, narrowed spinal canal and early degenerative changes, and in older age groups, especially midcervically narrowed spinal canal. Severe cervical kyphosis caused medullar compression. The intervertebral discs developed abnormally. Abnormal disc structure may be one etiologic factor in the development of cervical kyphosis. Early and rapid progression of the degenerative changes is a normal finding in patients with DD, regardless of their age, and this also explains the stiffness of the cervical spine in clinical examination. 相似文献
47.
Enhanced film-forming properties for ethyl cellulose and starch acetate using n-alkenyl succinic anhydrides as novel plasticizers 总被引:4,自引:0,他引:4
Maarit Tarvainen Riitta Sutinen Soili Peltonen Hannu Mikkonen Jaana Maunus Kalle Vh-Heikkil Vesa-Pekka Lehto Petteri Paronen 《European journal of pharmaceutical sciences》2003,19(5):363-371
Purpose: The aim of this study was to investigate the ability of n-alkenyl succinic anhydrides (n-ASAs) to improve the film-forming characteristics of a novel coating polymer, potato starch acetate degree of substitution 2.8 (SA). n-ASAs were also applied to improve the otherwise brittle properties of ethyl cellulose (EC) aqueous dispersion (Aquacoat®) and EC solvent-based films. Methods: The effectiveness of two n-ASAs, 2-octenyl succinic anhydride (OSA) and 2-dodecen-1-ylsuccinic anhydride were evaluated as plasticizers. Mechanical properties, both water vapor and drug permeabilities, and glass transition temperatures of the cast free films were measured. Triethyl citrate and dibutyl sebacate were used as reference plasticizers. Results: The long hydrocarbon chain of n-ASA, with its accessible carbonyl groups, enabled a strong plasticization effect on the tested polymers. Due to the excellent mechanical properties (i.e., a tough film structure with considerable flexibility) and low permeability of the plasticized films, n-ASAs, and especially OSA proved to be an ideal plasticizer particularly for EC based coatings. Also, the EC aqueous dispersion plasticized with n-ASAs resulted in a markedly enhanced coalescence of the colloidal polymer particles, even at low drying temperatures. Conclusions: In applications where a coating with high flexibility is required, n-ASAs can be used as plasticizers at moderately high concentrations (up to 60–70%, w/w) without losing the high tensile strength, excellent toughness and low permeability of EC and SA films. 相似文献
48.
Kristina Virkola Maija Lappalainen Leena Valanne Marjaleena Koskiniemi 《Pediatric radiology》1997,27(2):133-138
A total of 44 181 serum samples from 16 733 pregnant women were analyzed for findings suggesting primary Toxoplasma infection. Thirty-seven newborns exposed to maternal primary Toxoplasma infection in utero were studied prospectively with ultrasound, CT, and MRI for signs of intrauterine infection. Their mothers
had been treated during pregnancy, and all infants were treated. The children were assigned to three groups according to their
mothers' serological status, and the radiological results were compared with the clinical outcome. Although radiological signs
were scarce, ultrasound findings combined with maternal serology were found to be significantly related to clinical outcome.
Received: 19 October 1994 Accepted: 28 April 1996 相似文献
49.
Leena Hilakivi-Clarke 《Breast cancer research and treatment》1997,46(2-3):143-159
The possible role of personality patterns and psychosocial factors in breast cancer has been studied extensively, through both human and animal experiments. The data are conflicting, and the conclusions controversial. This review will serve two purposes. First, we present evidence that behavioral patterns most commonly linked to breast cancer risk are at least partly regulated by estrogens. This section will suggest that some estrogen-regulated behaviors may be markers of increased breast cancer risk. Second, we will briefly review recent findings in animals connecting psychosocial factors to cancer. We also will address the plausible biological mechanisms. The literature suggests that estrogens, particularly when exposure occurs during the critical developmental periods, such as in utero, puberty, pregnancy, and menopause, influence affective behaviors and increase breast cancer risk. The affective behaviors include depression, aggression, and alcohol intake. Thus, psychosocial and personality factors do not necessarily have a direct impact on breast cancer risk; instead, estrogens have a dual effect on behavior and on the breast. 相似文献
50.
The usefulness of botulinum toxin A treatment when planning hand surgery in eight children with spastic hemiplegia was evaluated. The hand function of the children was assessed before and after treatment using a test battery consisting of quantitative and qualitative functional assessment. The results of preoperative botulinum treatment supported surgical intervention in four children and serial botulinum treatment in three children. In one child, the preoperative botulinum treatment provided no additional information. We conclude that preoperative botulinum A treatment in most children with spastic hemiplegia, for whom hand surgery is being considered, identifies the patients who would not benefit from the planned surgery or for whom the functional benefit would probably not outweigh the burden of surgical procedure and postoperative rehabilitation. 相似文献