全文获取类型
收费全文 | 2062篇 |
免费 | 151篇 |
国内免费 | 16篇 |
专业分类
耳鼻咽喉 | 15篇 |
儿科学 | 32篇 |
妇产科学 | 20篇 |
基础医学 | 313篇 |
口腔科学 | 14篇 |
临床医学 | 194篇 |
内科学 | 615篇 |
皮肤病学 | 39篇 |
神经病学 | 182篇 |
特种医学 | 53篇 |
外科学 | 374篇 |
综合类 | 15篇 |
预防医学 | 94篇 |
眼科学 | 5篇 |
药学 | 108篇 |
中国医学 | 4篇 |
肿瘤学 | 152篇 |
出版年
2024年 | 2篇 |
2023年 | 22篇 |
2022年 | 36篇 |
2021年 | 93篇 |
2020年 | 40篇 |
2019年 | 91篇 |
2018年 | 80篇 |
2017年 | 75篇 |
2016年 | 60篇 |
2015年 | 55篇 |
2014年 | 84篇 |
2013年 | 117篇 |
2012年 | 173篇 |
2011年 | 192篇 |
2010年 | 91篇 |
2009年 | 93篇 |
2008年 | 126篇 |
2007年 | 118篇 |
2006年 | 116篇 |
2005年 | 108篇 |
2004年 | 87篇 |
2003年 | 112篇 |
2002年 | 85篇 |
2001年 | 15篇 |
2000年 | 19篇 |
1999年 | 19篇 |
1998年 | 13篇 |
1997年 | 10篇 |
1996年 | 14篇 |
1995年 | 13篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有2229条查询结果,搜索用时 15 毫秒
1.
2.
Differential mortality: some comparisons between England and Wales, Finland and France, based on inequality measures 总被引:4,自引:0,他引:4
Inequalities in mortality between social classes or socioeconomic groups were compared in three European countries, using similar sources of data from large national cohort studies. People registered at a census in 1971 (1975 for France) or a sample of them, were followed until 1980 or 1981. The Gini coefficient, a measure widely used in economics, allowed the comparison of various situations involving different numbers and group sizes. It was applied to age groups 35-44, and 45-54 for men only. According to this measure, inequalities were of the same order in England and Wales and Finland, and greater in France. Differences between the three countries concerning the principal causes of death leading to inequalities were cardiovascular diseases in England and Wales, accidents and cardiovascular diseases in Finland, and cancer and cirrhosis in France. 相似文献
3.
Biocompatibility studies of the Anaconda stent-graft and observations of nitinol corrosion resistance. 总被引:3,自引:0,他引:3
Robert Guidoin Yvan Douville Michel F Baslé Martin King Georgi R Marinov Amidou Traoré Ze Zhang Fabien Guillemot Guy Dionne Ruwan Sumanasinghe André-Pierre Legrand Marie-France Guidoin Marie-Christine Porté-Durrieu Charles Baquey 《Journal of endovascular therapy》2004,11(4):385-403
PURPOSE: To validate the deployment, in vivo performance, biostability, and healing capacity of the Anaconda self-expanding endoprosthesis in a canine aortic aneurysm model. METHODS: Aneurysms were surgically created in 12 dogs by sewing a woven polyester patch onto the anterior side of the thoracic or abdominal aorta. Anaconda prostheses were implanted transfemorally for prescheduled periods (1 or 3 months). Aneurysm exclusion and stent-graft patency were monitored angiographically. Healing was assessed with histological analysis and scanning electron microscopy (SEM). Textile analysis determined the physical and chemical stability of the woven polyester material, while the biostability of the nitinol wires was evaluated with SEM and spectroscopy. RESULTS: All prostheses were intact at explantation. After 1 month, endothelial-like cells were migrating in a discontinuous manner both proximally and distally over the internal collagenous pannus at the device-host boundary. After 3 months, endothelialization had reached the midsections of the devices, with a thicker collagenous internal capsule. Patches of endothelial-like cells were sharing the luminal surface with thrombotic deposits. However, the wall of the device at the level of the aneurysm was generally poorly healed, with multiple thrombi scattered irregularly over the luminal surface. The polyester fabric was intact except for some filaments that were ruptured adjacent to the sutures and some abrasion caused by the nitinol wires. No evidence of corrosion was found on the nitinol stents. CONCLUSIONS: This Anaconda stent-graft has demonstrated its ability to exclude arterial aneurysms. The device used in this study was an experimental prototype, and the manufacturer has incorporated new immobilization features into the model for clinical use. The constituent materials appear to be suitable in terms of biocompatibility, biofunctionality, and short-term durability. 相似文献
4.
Special evolution of neurohypophysial hormones in cartilaginous fishes: asvatocin and phasvatocin, two oxytocin-like peptides isolated from the spotted dogfish (Scyliorhinus caniculus). 下载免费PDF全文
J Chauvet Y Rouille C Chauveau M T Chauvet R Acher 《Proceedings of the National Academy of Sciences of the United States of America》1994,91(23):11266-11270
In contrast to most vertebrate species that possess one oxytocin-like hormone and one vasopressin-like hormone, a few groups, such as marsupials or cartilaginous fishes, are endowed with two peptides of either or both types, suggesting possible gene duplications. We have now isolated two oxytocin-like hormones from the pituitary of the spotted dogfish Scyliorhinus caniculus (suborder Galeoidei). Microsequencing as well as chromatographic and pharmacological comparisons with synthetic peptides show that these peptides are [Asn4,Val8]oxytocin (asvatocin) and [Phe3,Asn4,Val8]-oxytocin (phasvatocin). Asvatocin and phasvatocin display oxytocic activity on rat uterus, about 80 and 5 milliunits per nmol, respectively, and virtually no pressor activity on anesthetized rats. They occur in roughly equal molar amounts in the gland; vasotocin is also present in a proportional amount that is lower by about a factor of 20. In addition to the duality, conservative amino acid substitutions are observed in the two oxytocic peptides in positions 4 (Gln-4-->Asn) and 8 (Leu-8-->Val), when compared with oxytocin. Furthermore, replacement of the isoleucine residue found in position 3 of all other oxytocin-like hormones by phenylalanine in phasvatocin is exceptional; it determines a dramatic decrease of the oxytocic activity. Preservation of the C-terminal-amidated nonapeptide pattern in the 12 vertebrate neurohypophysial hormones known to date suggests that both precursors and processing enzymes have coevolved tightly. On the other hand, whereas the great evolutionary stability of the mature hormones (generally observed in vertebrates) suggests a strict messenger-receptor coevolution, the exceptional diversity found in cartilaginous fishes (six oxytocin-like peptides identified out of eight known) might be due to a looseness of selective constraints, perhaps in relationship with their specific urea osmoregulation. 相似文献
5.
Philippe Chauveau Benot Vendrely Wael El Haggan Nicole Barthe Vincent Rigalleau Christian Combe Michel Aparicio 《Journal of renal nutrition》2003,13(4):282-287
BACKGROUND: It has been reported that patients on a very-low-protein diet (VLPD) maintain a satisfactory nutritional status because of a conserved adaptive metabolic response. However, only few studies have examined the course of nutritional status and body composition in the long term (2 years). METHODS: Thirteen stable patients (8 men; age, 55 +/- 12 years; glomerular filtration rate (GFR), 15 +/- 5 mL/min) receiving a VLPD (0.3 g/kg/day protein) supplemented with amino acids and ketoanalogues (SVLPD) were studied for 2 years. A joint visit with a physician and a dietitian and routine blood and urine analyses were performed every month. Dual-energy x-ray absorptiometry (DEXA), which was used to assess modification of body composition, and GFR (urinary 51Cr-EDTA) and urinary urea and creatinine excretion, which were used to assess nutritional status and compliance to the diet, were assessed every 3 months. RESULTS: GFR, albumin, and prealbumin levels remained stable. Urea urinary excretion decreased at 3 months and then slightly increased at 2 years, but the calculated protein intake remained low at 0.38 +/- 0.1 g/kg/day. Energy intake remained close to 30 kcal/kg/day. No significant change was observed for total fat mass or percent fat mass. After an initial decrease, lean body mass stabilized at 6 months and then increased significantly from 6 to 24 months (P =.02, paired t-test); the mean increase during this period was of 2 kg, that is, 4.6%. Urinary creatinine excretion showed the same profile. Total bone mass, lumbar or hip site bone mass, and Z-score significantly decreased from T0 to 1 and 2 years (P <.05). CONCLUSION: This study confirms that a supplemented VLPD is nutritionally safe for a long period, but attention must be paid to bone mass. 相似文献
6.
Gallou C Chauveau D Richard S Joly D Giraud S Olschwang S Martin N Saquet C Chrétien Y Méjean A Correas JM Benoît G Colombeau P Grünfeld JP Junien C Béroud C 《Human mutation》2004,24(3):215-224
von Hippel-Lindau (VHL) disease arises from mutations in the VHL gene and predisposes patients to develop a variety of tumors in different organs. In the kidney, single or multiple cysts and renal cell carcinomas (RCC) may occur. Both inter- and intrafamilial heterogeneity in clinical expression are well recognized. To identify VHL-dependent genetic factors, we investigated the renal phenotype in 274 individuals from 126 unrelated VHL families in whom 92 different VHL mutations were characterized. The incidence of renal involvement was increased in families with mutations leading to truncated protein (MLTP) or large rearrangement, as compared to families with missense changes (81 vs. 63%, respectively; P=0.03). In the latter group, we identified two mutation cluster regions (MCRs) associated with a high risk of harboring renal lesions: MCR-1 (codons 74-90) and MCR-2 (codons 130-136). In addition, the incidence of RCC was higher in families with MLTP than in families with missense changes (75 vs. 57%; P=0.04). Furthermore, mutations within MCR-1 but not MCR-2 conferred genetic susceptibility to develop RCC. Overall, our data argued for a substantial contribution of the genetic change in the VHL gene to susceptibility to renal phenotype in VHL patients. 相似文献
7.
Differential expression of extracellular matrix metalloproteinase inducer (CD147) in normal and ulcerated corneas: role in epithelio-stromal interactions and matrix metalloproteinase induction 总被引:12,自引:0,他引:12 下载免费PDF全文
Gabison EE Mourah S Steinfels E Yan L Hoang-Xuan T Watsky MA De Wever B Calvo F Mauviel A Menashi S 《The American journal of pathology》2005,166(1):209-219
Extracellular matrix metalloproteinase inducer (EMMPRIN) was originally identified on the tumor cell surface as an inducer of matrix metalloproteinase (MMP) production in neighboring fibroblasts. Here we demonstrate a role for EMMPRIN in MMP induction during corneal wound healing. MMP and EMMPRIN expression was analyzed in normal and ulcerated human corneas, as well as in corneal epithelial and stromal cells in culture using confocal microscopy, zymography, immunoblots, and real-time polymerase chain reaction. In normal cornea EMMPRIN was predominantly expressed in the epithelium but was markedly induced in the anterior stroma of ulcerated corneas. This coincided with MMP-2 induction that co-localized with EMMPRIN at the epithelio-stromal boundary. The role of epithelial-stromal interaction in MMP induction was investigated in an in vitro co-culture system and demonstrated an induction and co-localization of EMMPRIN and MMP-2 in the fibroblasts at the interface with epithelial cells. Direct contact of fibroblasts with EMMPRIN-containing purified epithelial cell membranes also induced MMP-1, MMP-2, and EMMPRIN and this was inhibited by a blocking anti-EMMPRIN antibody, suggesting that EMMPRIN was primarily responsible for this induction. These findings, and the up-regulation of EMMPRIN by epidermal growth factor and transforming growth factor-beta, demonstrate a role for EMMPRIN in wound healing and suggest that sustained local up-regulation of EMMPRIN and MMPs in chronic situations in which healing is delayed may lead to excessive matrix degradation and corneal melts. 相似文献
8.
Hfq-dependent regulation of OmpA synthesis is mediated by an antisense RNA 总被引:17,自引:1,他引:17 下载免费PDF全文
Udekwu KI Darfeuille F Vogel J Reimegård J Holmqvist E Wagner EG 《Genes & development》2005,19(19):2355-2366
This paper shows that the small RNA MicA (previously SraD) is an antisense regulator of ompA in Escherichia coli. MicA accumulates upon entry into stationary phase and down-regulates the level of ompA mRNA. Regulation of ompA (outer membrane protein A), previously attributed to Hfq/mRNA binding, is lost upon deletion of the micA gene, whereas overexpression of MicA inhibits the synthesis of OmpA. In vitro, MicA binds to the ompA mRNA leader. Enzymatic and chemical probing was used to map the structures of MicA, the ompA mRNA leader, and the complex formed upon binding. MicA binding generates a footprint across the ompA Shine-Dalgarno sequence, consistent with a 12 + 4 base-pair interaction, which is additionally supported by the effect of mutations in vivo and by bioinformatics analysis of enterobacterial micA/ompA homolog sequences. MicA is conserved in many enterobacteria, as is its ompA target site. In vitro toeprinting confirmed that binding of MicA specifically interferes with ribosome binding. We propose that MicA, when present at high levels, blocks ribosome binding at the ompA translation start site, which-in line with previous work-secondarily facilitates RNase E cleavage and subsequent mRNA decay. MicA requires the presence of the Hfq protein, although the mechanistic basis for this remains unclear. 相似文献
9.
Different hormones (thymulin, thymosin alpha 1, vasopressin), antigenic markers of cortical and subcapsular/medullary thymic areas and tumour associated antigens were studied on paraffin or frozen section and cultures of human epithelial thymic tumours ('thymomas'). Thymulin, thymosin alpha 1 and for the first time vasopressin are found in most tumours. The epithelial cells of five 'thymomas' had markers of both cortical (TE3) and subcapsular/medullary thymic regions (A2B5 and/or TE4 and/or anti-p19). Leu-7, a marker of subcapsular epithelial cells was positive only in two tumours. The histological classification into cortical and medullary tumours does not correspond to our immunofluorescence results. The presence of these markers does not support the theory of different embryologic origin of the cortical and subcapsular/medullary epithelial cells. Transferrin receptors were detected on only some epithelial cells of thymic 'carcinomas'. Adenocarcinoma related antigen and carcino embryonic antigen only stained a few epithelial cells of all the tumours. There is no expected correlation between the presence of epidermal growth factor receptors on cell membranes and the number of proliferative cells stained by the anti-Ki67 antibodies. Immunostainings were heterogeneous according to the epithelial thymic tumours, independent of histological classification and not yet useful for prognosis. 相似文献
10.
Anti-thymosin alpha 1 monoclonal antibodies recognized, on immunoblots, 1 to 2 bands corresponding to molecules of 34 and 35 Kd when using aqueous extracts of thymus, spleen, kidney, liver, brain, pituitary and adrenal glands from rats or mice. Anti-bovine thymopoietin polyclonal antibodies, in the same conditions, labelled analogous 34, 35 and 35.5 Kd molecules in brain and thymus extracts but also a 40 Kd molecules in thymus and a 90 Kd in brain extracts. Anti-synthetic thymulin monoclonal antibodies recognized irregularly and poorly a 52 Kd molecule from thymus and brain extracts. These results suggest that thymopoietin, thymulin and specially Thymosin alpha 1 are first synthesized in large precursors. Finally, other organs seem capable of synthesizing thymosin alpha 1 and probably thymopoietin, but for thymulin, the results are too irregular to conclude. 相似文献