全文获取类型
收费全文 | 2529篇 |
免费 | 152篇 |
国内免费 | 11篇 |
专业分类
耳鼻咽喉 | 30篇 |
儿科学 | 32篇 |
妇产科学 | 66篇 |
基础医学 | 384篇 |
口腔科学 | 56篇 |
临床医学 | 284篇 |
内科学 | 455篇 |
皮肤病学 | 35篇 |
神经病学 | 401篇 |
特种医学 | 92篇 |
外科学 | 380篇 |
综合类 | 7篇 |
一般理论 | 2篇 |
预防医学 | 154篇 |
眼科学 | 54篇 |
药学 | 174篇 |
肿瘤学 | 86篇 |
出版年
2023年 | 19篇 |
2022年 | 32篇 |
2021年 | 49篇 |
2020年 | 48篇 |
2019年 | 55篇 |
2018年 | 49篇 |
2017年 | 68篇 |
2016年 | 69篇 |
2015年 | 57篇 |
2014年 | 84篇 |
2013年 | 135篇 |
2012年 | 190篇 |
2011年 | 181篇 |
2010年 | 110篇 |
2009年 | 93篇 |
2008年 | 157篇 |
2007年 | 176篇 |
2006年 | 143篇 |
2005年 | 153篇 |
2004年 | 150篇 |
2003年 | 164篇 |
2002年 | 151篇 |
2001年 | 41篇 |
2000年 | 34篇 |
1999年 | 28篇 |
1998年 | 33篇 |
1997年 | 38篇 |
1996年 | 15篇 |
1995年 | 25篇 |
1994年 | 9篇 |
1993年 | 18篇 |
1992年 | 15篇 |
1991年 | 7篇 |
1990年 | 11篇 |
1989年 | 11篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 3篇 |
排序方式: 共有2692条查询结果,搜索用时 15 毫秒
91.
Post-neonatal hospitalization and health care costs among IVF children: a 7-year follow-up study 总被引:1,自引:0,他引:1
Koivurova S Hartikainen AL Gissler M Hemminki E Järvelin MR 《Human reproduction (Oxford, England)》2007,22(8):2136-2141
BACKGROUND: The objective of this study was to evaluate whether the post-neonatal hospitalization and resulting health care costs are increased among in vitro fertilization (IVF) children up to 7 years of age. METHODS: We conducted a population-based cohort study with linkage to a national hospital discharge register including 303 IVF children, born from 1990 to 1995, and 567 control children (1:2) randomly chosen from the Finnish Medical Birth Register and matched for sex, year of birth, area of residence, parity, maternal age and socioeconomic status. The cost calculations were stratified for singleton (n = 152 vs. n = 285) and twin (n = 103 vs. n = 103) status. Main outcome measures were hospitalizations and societal health care costs. RESULTS: The full-sample and singleton analyses showed that IVF children were significantly more frequently admitted to hospital (mean 1.76 vs. 1.07, P < 0.0001; 1.61 vs. 1.07, P = 0.0004, respectively) and spent significantly more days in the hospital (mean 4.31 vs. 2.61, P < 0.0001; 3.47 vs. 2.56, P = 0.0014, respectively) than control children. No differences were detected between IVF and control twins. The costs of post-neonatal hospital care per child were 2.6-fold for IVF singletons, but 0.7-fold for IVF twins when compared with controls. Cost estimation showed 2.6-fold costs for total IVF population in comparison to general population based controls. CONCLUSIONS: The incidence of multiple births increases the utilization of post-neonatal health care services and costs among IVF children in comparison to naturally conceived children. Increased hospitalization and costs were also seen among IVF singletons. 相似文献
92.
Qu CJ Rieppo J Hyttinen MM Lammi MJ Kiviranta I Kurkijärvi J Jurvelin JS Töyräs J 《Connective tissue research》2007,48(1):27-33
Chondroitin sulfate is the major constituent of cartilage. Inadequate sulfate availability results in the production of undersulfated proteoglycans. In osteoarthritis, there is a net loss of articular cartilage proteoglycans. Theoretically, it is possible that during the progress of disease undersulfated glycosaminoglycans are synthesized producing proteoglycans with poorer biological properties. In this study, we tested whether in early human osteoarthritic articular cartilage (Mankin's score of 2 and 3) or more advanced disease (Mankin's score over 3), there are proteoglycans that contain a higher relative amount of nonsulfated chondroitin disaccharide isomer in their chondroitin sulfate chains by analyzing the molar ratios of chondroitin sulfate disaccharide isoforms with fluorophore-assisted carbohydrate electrophoresis. Our results indicated that the nonsulfated disaccharide of chondroitin sulfate formed in average only 1-2% of the total chondroitin sulfate. More important, the molar ratio of nonsulfated disaccharide did not appear to be increased in the osteoarthritic articular cartilage. We conclude that undersulfation of articular cartilage proteoglycans is not present in the human osteoarthritic joint. 相似文献
93.
Hellquist A Zucchelli M Kivinen K Saarialho-Kere U Koskenmies S Widen E Julkunen H Wong A Karjalainen-Lindsberg ML Skoog T Vendelin J Cunninghame-Graham DS Vyse TJ Kere J Lindgren CM 《Journal of medical genetics》2007,44(5):314-321
Background
Several members of the GIMAP gene family have been suggested as being involved in different aspects of the immune system in different species. Recently, a mutation in the GIMAP5 gene was shown to cause lymphopenia in a rat model of autoimmune insulin‐dependent diabetes. Thus it was hypothesised that genetic variation in GIMAP5 may be involved in susceptibility to other autoimmune disorders where lymphopenia is a key feature, such as systemic lupus erythematosus (SLE).Material and methods
To investigate this, seven single nucleotide polymorphisms in GIMAP5 were analysed in five independent sets of family‐based SLE collections, containing more than 2000 samples.Result
A significant increase in SLE risk associated with the most common GIMAP5 haplotype was found (OR 1.26, 95% CI 1.02 to 1.54, p = 0.0033). In families with probands diagnosed with trombocytopenia, the risk was increased (OR 2.11, 95% CI 1.09 to 4.09, p = 0.0153). The risk haplotype bears a polymorphic polyadenylation signal which alters the 3′ part of GIMAP5 mRNA by producing an inefficient polyadenylation signal. This results in higher proportion of non‐terminated mRNA for homozygous individuals (p<0.005), a mechanism shown to be causal in thalassaemias. To further assess the functional effect of the polymorphic polyadenylation signal in the risk haplotype, monocytes were treated with several cytokines affecting apoptosis. All the apoptotic cytokines induced GIMAP5 expression in two monocyte cell lines (1.5–6 times, p<0.0001 for all tests).Conclusion
Taken together, the data suggest the role of GIMAP5 in the pathogenesis of SLE. 相似文献94.
Abhisek Bhattarai Behdad Pouran Janne T. A. Mäkelä Rubina Shaikh Miitu K. M. Honkanen Mithilesh Prakash Heikki Kröger Mark W. Grinstaff Harrie Weinans Jukka S. Jurvelin Juha Töyräs 《Journal of orthopaedic research》2020,38(10):2230-2238
Cationic computed tomography contrast agents are more sensitive for detecting cartilage degeneration than anionic or non-ionic agents. However, osteoarthritis-related loss of proteoglycans and increase in water content contrarily affect the diffusion of cationic contrast agents, limiting their sensitivity. The quantitative dual-energy computed tomography technique allows the simultaneous determination of the partitions of iodine-based cationic (CA4+) and gadolinium-based non-ionic (gadoteridol) agents in cartilage at diffusion equilibrium. Normalizing the cationic agent partition at diffusion equilibrium with that of the non-ionic agent improves diagnostic sensitivity. We hypothesize that this sensitivity improvement is also prominent during early diffusion time points and that the technique is applicable during contrast agent diffusion. To investigate the validity of this hypothesis, osteochondral plugs (d = 8 mm, N = 33), extracted from human cadaver (n = 4) knee joints, were immersed in a contrast agent bath (a mixture of CA4+ and gadoteridol) and imaged using the technique at multiple time points until diffusion equilibrium. Biomechanical testing and histological analysis were conducted for reference. Quantitative dual-energy computed tomography technique enabled earlier determination of cartilage proteoglycan content over single contrast. The correlation coefficient between human articular cartilage proteoglycan content and CA4+ partition increased with the contrast agent diffusion time. Gadoteridol normalized CA4+ partition correlated significantly (P < .05) with Mankin score at all time points and with proteoglycan content after 4 hours. The technique is applicable during diffusion, and normalization with gadoteridol partition improves the sensitivity of the CA4+ contrast agent. 相似文献
95.
Fausto Biancari Juha Saarnio Ari Mennander Linda Hypén Paulina Salminen Kari Kuttila Mikael Victorzon Camilla Böckelman Enrico Tarantino Olivier Tiffet Vesa Koivukangas Jon Arne Søreide Asgaut Viste Luigi Bonavina Halla Vidarsdóttir Tomas Gudbjartsson 《World journal of surgery》2014,38(4):902-909
Background
Recent studies have suggested that stent-grafting may improve the treatment outcome of patients with esophageal perforation, but evidence on this is still lacking.Methods
Data on 194 patients who underwent conservative (43 patients), endoclip (4 patients) stent-grafting (63 patients) or surgical treatment (84 patients) for esophageal perforation were retrieved from nine medical centers.Results
In-hospital/30-day mortality was 17.5 %. Three-year survival was 67.1 %. Age, coronary artery disease, and esophageal malignancy were independent predictors of early mortality. Chi squared automatic interaction detection analysis showed that patients without coronary artery disease, without esophageal malignancy and younger than 70 years had the lowest early mortality (4.1 %). Surgery was associated with slightly lower early mortality (conservative 23.3, endoclips 25.0 %, stent-grafting 19.0 %, surgery 13.1 %; p = 0.499). One center reported a series of more than 20 patients treated with stent-grafting which achieved an early mortality of 7.7 % (2/26 patients). Stent-grafting was associated with better survival with salvaged esophagus (conservative 76.7 %, endoclips 75.0 %, stent-grafting 77.8 %, surgery 56.0 %; p = 0.019). Propensity score adjusted analysis showed that stent-grafting achieved similar early mortality (p = 0.946), but significantly higher survival with salvaged esophagus than with surgical treatment (p = 0.001, OR 0.253, 95 % CI 0.110–0.585). Primary surgical repair was associated with somewhat lower early mortality (14.6 vs. 19.0 %; p = 0.561) and better survival with salvaged esophagus (85.4 vs. 77.8 %; p = 0.337) than stent-grafting.Conclusions
Esophageal perforation was associated with a rather high mortality rate in this all-comers population. Stent-grafting failed to decrease operative mortality, but it improved survival with salvaged esophagus. The results of one of the centers indicate that increasing experience with this less invasive procedure may possibly improve the outcome of these patients. 相似文献96.
97.
98.
99.
Kaisa Nieminen Juha Immanen Marjukka Laxell Leila Kauppinen Petr Tarkowski Karel Dolezal Sari Thtiharju Annakaisa Elo Mlanie Decourteix Karin Ljung Rishikesh Bhalerao Kaija Keinonen Victor A. Albert Yk Helariutta 《Proceedings of the National Academy of Sciences of the United States of America》2008,105(50):20032-20037
Although a substantial proportion of plant biomass originates from the activity of vascular cambium, the molecular basis of radial plant growth is still largely unknown. To address whether cytokinins are required for cambial activity, we studied cytokinin signaling across the cambial zones of 2 tree species, poplar (Populus trichocarpa) and birch (Betula pendula). We observed an expression peak for genes encoding cytokinin receptors in the dividing cambial cells. We reduced cytokinin levels endogenously by engineering transgenic poplar trees (P. tremula × tremuloides) to express a cytokinin catabolic gene, Arabidopsis CYTOKININ OXIDASE 2, under the promoter of a birch CYTOKININ RECEPTOR 1 gene. Transgenic trees showed reduced concentration of a biologically active cytokinin, correlating with impaired cytokinin responsiveness. In these trees, both apical and radial growth was compromised. However, radial growth was more affected, as illustrated by a thinner stem diameter than in WT at same height. To dissect radial from apical growth inhibition, we performed a reciprocal grafting experiment. WT scion outgrew the diameter of transgenic stock, implicating cytokinin activity as a direct determinant of radial growth. The reduced radial growth correlated with a reduced number of cambial cell layers. Moreover, expression of a cytokinin primary response gene was dramatically reduced in the thin-stemmed transgenic trees. Thus, a reduced level of cytokinin signaling is the primary basis for the impaired cambial growth observed. Together, our results show that cytokinins are major hormonal regulators required for cambial development. 相似文献
100.
Kirsten D. Bentsen Thomas Horn Juha Risteli Leila Risteli Anna Engstrm-Laurent Kim Hrslev-Petersen Ib Lorenzen 《Liver international》1987,7(6):339-346
ABSTRACT— Serum concentrations of the aminoterminal propeptide of type III procollagen and of the 7S domain of type IV collagen, presumed to reflect fibrotic activity in liver tissue, and of the glycosamonoglycan hyaluronan, were obtained from 40 alcohol abusers, at the time of liver biopsy. The serological results were related to morphological findings in liver tissue, i.e. no fibrosis, fibrosis without cirrhosis, micronodular cirrhosis and macronodular cirrhosis, and to ultrastructural indications of perisinusoidal fibrosis in the acinar zone 3. All patients with fibrosis and cirrhosis on light microscopy had elevated serum levels of the type III procollagen peptide as well as of the 7S domain of type IV collagen. However, due to a considerable overlap between the groups, no relations could be demonstrated to the severity of the fibrosis, supporting the assumption that these serological markers reflect the current fibrotic activity and not the amount of fibrotic tissue previously deposited. Among patients without fibrosis on light microscopy, a relation between the propeptide levels and ultrastructural perisinusoidal zone 3 fibrosis was observed, suggesting that type III procollagen peptide may be valuable in detecting very early liver fibrosis. A positive correlation was demonstrated between the serum concentrations of type III procollagen peptide and hyaluronan. As hyaluronan is degraded in the liver endothelial cells, it is suggested that the liver is involved, not only in the synthesis, but also in the degradation of the propeptide. 相似文献