全文获取类型
收费全文 | 1664篇 |
免费 | 103篇 |
国内免费 | 11篇 |
专业分类
耳鼻咽喉 | 9篇 |
儿科学 | 56篇 |
妇产科学 | 16篇 |
基础医学 | 208篇 |
口腔科学 | 79篇 |
临床医学 | 143篇 |
内科学 | 385篇 |
皮肤病学 | 70篇 |
神经病学 | 92篇 |
特种医学 | 262篇 |
外科学 | 209篇 |
综合类 | 38篇 |
预防医学 | 48篇 |
眼科学 | 32篇 |
药学 | 48篇 |
肿瘤学 | 83篇 |
出版年
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 16篇 |
2017年 | 11篇 |
2016年 | 14篇 |
2015年 | 19篇 |
2014年 | 32篇 |
2013年 | 39篇 |
2012年 | 39篇 |
2011年 | 56篇 |
2010年 | 56篇 |
2009年 | 57篇 |
2008年 | 52篇 |
2007年 | 51篇 |
2006年 | 47篇 |
2005年 | 46篇 |
2004年 | 26篇 |
2003年 | 28篇 |
2002年 | 35篇 |
2001年 | 52篇 |
2000年 | 50篇 |
1999年 | 29篇 |
1998年 | 56篇 |
1997年 | 69篇 |
1996年 | 62篇 |
1995年 | 50篇 |
1994年 | 54篇 |
1993年 | 38篇 |
1992年 | 30篇 |
1991年 | 26篇 |
1990年 | 29篇 |
1989年 | 39篇 |
1988年 | 47篇 |
1987年 | 29篇 |
1986年 | 43篇 |
1985年 | 46篇 |
1984年 | 26篇 |
1983年 | 35篇 |
1982年 | 31篇 |
1981年 | 20篇 |
1980年 | 17篇 |
1979年 | 21篇 |
1978年 | 25篇 |
1977年 | 21篇 |
1976年 | 25篇 |
1975年 | 10篇 |
1973年 | 13篇 |
1972年 | 10篇 |
1969年 | 10篇 |
1967年 | 12篇 |
排序方式: 共有1778条查询结果,搜索用时 140 毫秒
71.
72.
Intra-aortic balloon pumping in infants and children 总被引:1,自引:0,他引:1
From November 1981 to November 1982, intra-aortic balloon pumping (IABP) was used after surgery in eight patients who were from 6 weeks to 6 years old and who weighed from 4.2 to 16.2 kg. In seven patients, specially constructed intra-aortic balloons with 2.5 and 5.0 ml volumes mounted on No. 5F catheters were used. In the largest and oldest patient, a two-chamber 10 ml balloon was used. The pumping module used was the Datascope System 82. Effective diastolic augmentation of arterial pressure was accomplished in seven of the eight patients and suprasystolic diastolic augmentation was accomplished in four. The two youngest and smallest patients are the only long-term survivors. There were two short-term survivors who died 5 and 10 days after successful IABP. In only one patient was there no appreciable effect of IABP. Miniaturization of the equipment has permitted IABP to be used effectively in pediatric patients. 相似文献
73.
The effects of recombinant-DNA-derived interferons on the growth of myeloid progenitor cells 总被引:5,自引:0,他引:5
Interferons (IFNs) have been shown to have significant effects on hematopoietic cell growth. Previous studies defining these effects have utilized mouse and human alpha-, beta-, and gamma-IFN isolated from supernatants of stimulated cells. Despite purification, the possible presence of other lymphokines and soluble factors remains a concern. In this study, the effects of gene-cloned alpha- and gamma-IFN on colony- forming units of granulocyte/macrophage (CFU-GM) progenitors cultured from the peripheral blood of normal volunteers were examined. In addition, blast cell colonies from one patient with acute myelogenous leukemia (AML) were studied. The growth of normal CFU-GM and AML blast cell colonies was inhibited in a dose-dependent manner by gamma- and alpha-IFN. gamma-IFN was ten to 100 times more potent than alpha-IFN in that this species of IFN reduced colony formation by greater than 50% at concentrations of less than 15 antiviral U/mL. The effects of gamma- IFN were neutralized by a monoclonal antibody specific for gamma-IFN. These in vitro studies indicate that human gamma-IFN may be an important modulator of myelopoiesis. Although these data indicate a possible efficacy of gamma-IFN in the treatment of AML, the in vitro results should be considered for their in vivo significance. 相似文献
74.
Marlene H. van Knobelsdorff Nikki G. van Bergen John van der Kamp Ludovic Seifert Dominic Orth 《Scandinavian journal of medicine & science in sports》2020,30(12):2485-2497
The capability to adapt to changing conditions is crucial for safe and successful performance in physical activities and sports. According to the affordance-based control perspective, individuals act in such a way as to take into account the limits of their capability to act. However, it is not clear how strength interacts with skill in shaping performer-environment interactions. We, therefore, determined whether fingertip strength influences patterns of gaze and climbing behavior on new routes of ever-increasing difficulty. We expected that comparatively weaker climbers would show less complex behavior because of an inability to perceive and act. Stronger climbers would show more complex visuo-motor behavior because more opportunities for action remain, even as route difficulty increases. For very strong climbers the route would not be challenging enough, and less complex patterns suffice. Twenty climbers, ranging from lower grade to elite level participated. Maximum fingertip strength was obtained. Participants previewed and then climbed two separate 3 m long traverses, gradually decreasing in edge depth. Gaze and hip positions were collected for subsequent computation of gaze transition entropy (during preview) and hip displacement entropy (during climbing). Data revealed statistically significant curvilinear relationships between both fingertip strength and gaze transition entropy, and fingertip strength, and hip displacement entropy. Visuo-motor complexity is scaled by how close the individual must act relative to boundaries of what the environment affords and does not afford for action given the individual constraints. Future research should examine in greater detail relationships between action capabilities and functional movement variability. 相似文献
75.
76.
77.
Arianne C Lim Kitty WM Bloemenkamp Kees Boer Johannes J Duvekot Jan Jaap HM Erwich Tom HM Hasaart Pieter Hummel Ben WJ Mol Jos PM Offermans Charlotte M van Oirschot Job G Santema Hubertina CJ Scheepers Willem A Schöls Frank PHA Vandenbussche Maurice GAJ Wouters Hein W Bruinse 《BMC pregnancy and childbirth》2007,7(1):1-6
Background
Adequate vitamin D concentrations during pregnancy are necessary to neonatal calcium homeostasis, bone maturation and mineralization. The aim of study is to evaluate serum vitamin D concentrations in mothers and their newborns and effect of vitamin D deficiency on pregnancy outcomes.Methods
552 pregnant women were recruited from Tehran University educating hospitals in the winter of 2002. Maternal and cord blood samples were taken at delivery. The serum was assayed for 25-hydroxyvitamin D3, calcium, phosphorus and parathyroid hormone.Results
The prevalence of vitamin D deficiency in maternal and cord blood samples were 66.8% and 93.3%, respectively (<35 nmol/l). There was significant correlation between maternal and cord blood serum concentrations of vitamin D. In mothers with vitamin D deficiency, cord blood vitamin D concentrations was lower than those from normal mothers (P = .001). Also, a significant direct correlation was seen between maternal vitamin D intake and weight gain during pregnancy.Conclusion
Consideration to adequate calcium and vitamin D intake during pregnancy is essential. Furthermore, we think it is necessary to reconsider the recommendation for vitamin D supplementation for women during pregnancy. 相似文献78.
Nicolas Kaulen Ravichandran Rajkumar Cludia Rgio Brambilla Jrg Mauler Shukti Ramkiran Linda Orth Hasan Sbaihat Markus Lang Christine Wyss Elena Rota Kops Jürgen Scheins Bernd Neumaier Johannes Ermert Hans Herzog KarlJoseph Langen Christoph Lerche N. Jon Shah Tanja Veselinovi Irene Neuner 《Human brain mapping》2022,43(7):2148
The glutamate and γ‐aminobutyric acid neuroreceptor subtypes mGluR5 and GABAA are hypothesized to be involved in the development of a variety of psychiatric diseases. However, detailed information relating to their in vivo distribution is generally unavailable. Maps of such distributions could potentially aid clinical studies by providing a reference for the normal distribution of neuroreceptors and may also be useful as covariates in advanced functional magnetic resonance imaging (MR) studies. In this study, we propose a comprehensive processing pipeline for the construction of standard space, in vivo distributions of non‐displaceable binding potential (BP ND), and total distribution volume (V T) based on simultaneously acquired bolus‐infusion positron emission tomography (PET) and MR data. The pipeline was applied to [11C]ABP688‐PET/MR (13 healthy male non‐smokers, 26.6 ± 7.0 years) and [11C]Flumazenil‐PET/MR (10 healthy males, 25.8 ± 3.0 years) data. Activity concentration templates, as well as V T and BP ND atlases of mGluR5 and GABAA, were generated from these data. The maps were validated by assessing the percent error δ from warped space to native space in a selection of brain regions. We verified that the average δABP = 3.0 ± 1.0% and δFMZ = 3.8 ± 1.4% were lower than the expected variabilities σ of the tracers (σABP = 4.0%–16.0%, σFMZ = 3.9%–9.5%). An evaluation of PET‐to‐PET registrations based on the new maps showed higher registration accuracy compared to registrations based on the commonly used [15O]H2O‐template distributed with SPM12. Thus, we conclude that the resulting maps can be used for further research and the proposed pipeline is a viable tool for the construction of standardized PET data distributions. 相似文献
79.
Ada A. Cole Susan Chubinskaya Lawrence J. Luchene Kim Chlebek Michael W. Orth Robert A. Greenwald Klaus E. Kuettner Thomas M. Schmid 《Arthritis \u0026amp; Rheumatology》1994,37(12):1727-1734
Objective. The effects of doxycycline were tested in an in vitro system in which the cartilages of embryonic avian tibias are completely degraded. Methods. Tibias were cultured with 5, 20, or 40 μg/ml doxycycline. Control tibias were cultured without doxycycline. Conditioned media and tissue sections were examined for enzyme activity and matrix loss. Results. Cartilages were not resorbed in the presence of doxycycline, whereas control cartilages were completely degraded. Collagen degradation was reduced in association with treatment with doxycycline at all doses studied. Higher concentrations of doxycycline reduced collagenase and gelatinase activity and prevented proteoglycan loss, cell death, and deposition of type X collagen in the cartilage matrix; in addition, treatment with doxycycline at higher concentrations caused increases in the length of the hypertrophic region. Conclusion. The effects of doxycycline extend beyond inhibition of the proteolytic enzymes by stimulating cartilage growth and disrupting the terminal differentiation of chondrocytes. 相似文献
80.
Plurality of genital human papillomaviruses: characterization of two new types with distinct biological properties 总被引:11,自引:0,他引:11
S Beaudenon D Kremsdorf S Obalek S Jablonska G Pehau-Arnaudet O Croissant G Orth 《Virology》1987,161(2):374-384
The genomes of two new genital human papillomavirus (HPV) types, tentatively named HPVs 39 and 42, have been cloned from biopsy specimens of penile Bowenoid papules and vulvar papillomas, respectively. Blot hybridization experiments, performed under stringent conditions (Tm -10 degrees), have revealed no cross-hybridization between the DNAs of HPVs 39 and 42, and between these DNAs and those of other genital and cutaneous HPVs. A significant cross-hybridization has been observed between the DNA of HPV42 and that of HPV32, the latter being associated with oral focal epithelial hyperplasia. The fraction of HPV32 and HPV42 hybrid molecules resistant to nuclease S1 treatment after hybridization in liquid phase at saturation has been evaluated to 20%, supporting the view that these HPVs constitute distinct types. In addition to HPV42 DNA, a 6.8-kb BamHI fragment, cross-hybridizing with HPV39 DNA, has been cloned from the vulvar papilloma DNA preparation. The cross-hybridization has been evaluated to 16%, pointing to the existence of an additional HPV39-related type. Electron microscope analysis of heteroduplex molecules formed between HPV32 and HPV42 DNAs showed paired regions over about 60 and 87% of their genome lenghts under stringent (Tm -18 degrees) and nonstringent (Tm -42 degrees) conditions, respectively. The 6.8-kb HPV DNA and HPV39 DNA formed paired regions over about 63 and 95% of the 6.8-kb fragment length at Tm -18 degrees and Tm -26 degrees, respectively. These data point to greater DNA sequence homologies than anticipated from the percentages of nuclease S1 resistance. Heteroduplex mapping has allowed the alignment of the physical maps of HPV39 and 42 DNAs and of the 6.8-kb HPV DNA with the map of the open reading frames of the HPV16 genome. So far, HPV42 has been detected only in benign genital lesions showing usually no cell atypia. HPV39 has been detected in a few cases of intraepithelial neoplasias and invasive carcinomas of the uterine cervix. The viral DNA sequences have been found integrated into the cell genome in all four HPV39-associated cervical cancers of our series. It seems most likely that HPV42 belongs to the low-risk group of genital HPVs, while HPV39 represents a potentially oncogenic genital HPV type. 相似文献