全文获取类型
收费全文 | 3608篇 |
免费 | 235篇 |
专业分类
3843篇 |
出版年
2023年 | 23篇 |
2022年 | 41篇 |
2021年 | 76篇 |
2020年 | 53篇 |
2019年 | 56篇 |
2018年 | 94篇 |
2017年 | 75篇 |
2016年 | 136篇 |
2015年 | 186篇 |
2014年 | 199篇 |
2013年 | 260篇 |
2012年 | 296篇 |
2011年 | 296篇 |
2010年 | 179篇 |
2009年 | 178篇 |
2008年 | 212篇 |
2007年 | 205篇 |
2006年 | 173篇 |
2005年 | 183篇 |
2004年 | 163篇 |
2003年 | 155篇 |
2002年 | 146篇 |
2001年 | 28篇 |
2000年 | 31篇 |
1999年 | 39篇 |
1998年 | 25篇 |
1997年 | 35篇 |
1996年 | 33篇 |
1995年 | 24篇 |
1994年 | 30篇 |
1993年 | 25篇 |
1992年 | 16篇 |
1991年 | 17篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1973年 | 7篇 |
1971年 | 4篇 |
1946年 | 5篇 |
排序方式: 共有3843条查询结果,搜索用时 15 毫秒
91.
92.
Incoronata Galasso Angela Rosa Piergiovanni Lucia Lioi Bruno Campion Roberto Bollini Francesca Sparvoli 《Molecular breeding : new strategies in plant improvement》2009,23(4):617-624
A BAC library from common bean has been used in order to isolate the entire multigene Bowman–Birk serine protease inhibitor
family and to study its genome organization. Using a previously isolated trypsin/chymotrypsin inhibitor nucleotide sequence
as probe, two positive BAC clones were identified. The P2B8 BAC clone, of about 135 kbp and containing the complete BBI family,
was chosen and partially sequenced. Our results confirm that a small multigene family codes for three double-headed inhibitors
named: tc-BBI-1, tc-BBI-2 and et-BBI. They contain the binding loop trypsin/chymotrypsin (tc-BBI-1 and tc-BBI-2) and the elastase/trypsin
one (et-BBI), respectively. Genes coding for tc-BBI-1 and et-BBI, were found to be very close to each other and arranged in
a head to head fashion. Southern blot hybridisation on genomic DNA digested with PstI enzyme suggests that all three genes are present in a fragment of 19 kbp. Northern blot analyses on RNA isolated from various
common bean organs showed that the expression of tc-BBI-1 and et-BBI was restricted to the developing cotyledons.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
93.
Elena I. Oprita Lucia Moldovan Oana Craciunescu Wanda Buzgariu Christu Tardei Otilia Zarnescu 《Central European Journal of Biology》2006,1(1):61-72
Collagen-phosphate composites (COL/β-TCP) are novel materials that have the potential to be used as bone analogues. The aim of our study was to develop a porous
bioactive material composed of type I collagen, the main bone protein and tricalcium phosphate, the mineral phase of natural
bone, and investigate their in vitro biocompatibility in a human dermal fibroblast culture system. In order to obtain the
bioactive materials, type I collagen was isolated from bovine tendon and characterized by physicochemical methods. β-TCP was obtained from calcium carbonate by thermal decomposition at 900 °C temperature. The powder was examined with X-ray
diffraction. Two variants of COL/β-TCP scaffolds (P1 and P2) were prepared and examined by scanning electron microscopy. Our results revealed a microporous
structure with small white aggregates of β-TCP, non-homogenous scattered in the collagen framework without any preferential orientation. The biocompatibility of the
obtained scaffolds was tested by biochemical and histological methods on human fibroblast cultures. Both materials acted as
good subtrates for human dermal fibroblast proliferation and migration. 相似文献
94.
This paper studied the effect on UV-B ocular damage of 10µm hydrocaffeic acid (HCAF) alone and as a mixture (MIX) (5µm HCAF+5µm p-coumaric acid). Since ocular UV-B damage is mediated by reactive oxygen species, the aim was to test if HCAF and MIX could reduce oxidation damage in human conjunctival cells (WKD) in vitro and in cornea and sclera of rabbits in vivo. After UVB irradiation (44 J/m2) of WKD cells, 8-oxodG levels in DNA were markedly increased and this effect was attenuated by HCAF and MIX. Rabbit eyes were treated by application of HCAF and MIX drops before UV-B exposure (79 J/m2). Corneal and scleral DNA oxidation damage, xanthine-oxidase (XO) activity and malondialdehyde levels (MDA) in corneal tissue and prostaglandin E2 (PGE2) in the aqueous humour were reduced by HCAF alone and in combination with p-coumaric acid, showing their potential as a topical treatment against UV-B damage. 相似文献
95.
doi: 10.1111/j.1741‐2358.2011.00573.x Effect of long‐term water immersion on the fracture toughness of denture base and reline resins purpose: This study evaluated the fracture toughness (FT) of one denture base (Lucitone 550 – L) and four hard reline resins [Ufi Gel Hard (UH), Tokuyama Rebase II (TR), New Truliner (NT) and Kooliner (K)], and the effect of long‐term water storage on this property. Materials and methods: Forty specimens (40 × 8 × 4 mm) of each material were made, and FT was assessed after polymerisation (control of reliners), after 48 ± 2 h in water at 37°C (control of denture base resin) and after storage in water at 37°C for 7, 90 or 180 days (all materials). Data (MPa.m1/2) were analysed by two‐way anova and Games–Howell test (p = 0.05). Results: Resin L exhibited the highest FT mean values. After 180 days of storage, FT mean values of L (3.37), UH (1.53) and K (1.20) were higher than those of the other periods. FT mean values of NT decreased from control (1.63) to 7 days (1.30) and then remained constant. FT mean values of TR (1.13) were similar in all periods of analysis. Conclusion: The denture base resin L showed higher FT mean values than the reline resins. Long‐term water storage increased the FT of L, UH and K, reduced the FT of NT and did not influence the FT of TR. 相似文献
96.
Batista MN Cuppari L de Fátima Campos Pedrosa L Almeida Md de Almeida JB de Medeiros AC Canziani ME 《Biological trace element research》2006,112(1):1-12
The aim of this study was to compare the nutritional status of zinc and copper in patients with and without diabetes submitted
to chronic hemodialysis. Thirty-three patients with type 2 diabetes (DM group), 30 nondiabetic patients (NDM group), and 20
healthy individuals (control group) were studied. Plasma, erythrocyte, and urinary zinc and plasma copper were obtained from
atomic absorption spectrophotometry and ceruloplasmin by immunonephelometry. The anthropometric parameters were similar among
the groups. Plasma zinc was lower and erythrocyte zinc was higher in the DM and NDM groups in relation to the control group.
No difference in urinary zinc was observed comparing the groups. Plasma copper was higher in the DM group when compared to
the NDM and control groups. Ceruloplasmin was similar in the three groups. Serum urea was a positive independent determinant
of plasma zinc concentrations. The determinants of erythrocyte zinc were MAMC midarm nuscle circumference and Kt/V dialysis
adequacy. The determinants of plasma copper concentration were serum creatinine and serum glucose. The results of this study
demonstrate an alteration in the distribution of zinc of patients with chronic kidney disease (CKD) independently of the presence
of DM. Also, the status of copper seems not to be influenced by CKD, but only by the metabolic derangements associated with
diabetes. 相似文献
97.
Fibrin gel-immobilized VEGF and bFGF efficiently stimulate angiogenesis in the AV loop model 总被引:5,自引:0,他引:5
Arkudas A Tjiawi J Bleiziffer O Grabinger L Polykandriotis E Beier JP Stürzl M Horch RE Kneser U 《Molecular medicine (Cambridge, Mass.)》2007,13(9-10):480-487
The modulation of angiogenic processes in matrices is of great interest in tissue engineering. We assessed the angiogenic effects of fibrin-immobilized VEGF and bFGF in an arteriovenous loop (AVL) model in 22 AVLs created between the femoral artery and vein in rats. The loops were placed in isolation chambers and were embedded in 500 microL fibrin gel (FG) (group A) or in 500 microL FG loaded with 0.1 ng/microL VEGF and 0.1 ng/microL bFGF (group B). After two and four weeks specimens were explanted and investigated using histological, morphometrical, and ultramorphological [scanning electron microscope (SEM) of vascular corrosion replicas] techniques. In both groups, the AVL induced formation of densely vascularized connective tissue with differentiated and functional vessels inside the fibrin matrix. VEGF and bFGF induced significantly higher absolute and relative vascular density and a faster resorption of the fibrin matrix. SEM analysis in both groups revealed characteristics of an immature vascular bed, with a higher vascular density in group B. VEGF and bFGF efficiently stimulated sprouting of blood vessels in the AVL model. The implantation of vascular carriers into given growth factor-loaded matrix volumes may eventually allow efficient generation of axially vascularized, tissue-engineered composites. 相似文献
98.
Laminin α1 Chain Synthesis in the Mouse Developing Lung: Requirement for Epithelial–Mesenchymal Contact and Possible Role in Bronchial Smooth muscle Development 下载免费PDF全文
Lucia Schuger Amy P.N. Skubitz Jun Zhang Lydia Sorokin Li He 《The Journal of cell biology》1997,139(2):553-562
Laminins, the main components of basement membranes, are heterotrimers consisting of α, β, and γ polypeptide chains linked together by disulfide bonds. Laminins-1 and -2 are both composed of β1 and γ1 chains and differ from each other on their α chain, which is α1 and α2 for laminin-1 and -2, respectively. The present study shows that whereas laminins-1 and -2 are synthesized in the mouse developing lung and in epithelial–mesenchymal cocultures derived from it, epithelial and mesenchymal monocultures lose their ability to synthesize the laminin α1 chain. Synthesis of laminin α1 chain however returns upon re-establishment of epithelial–mesenchymal contact. Cell–cell contact is critical, since laminin α1 chain is not detected in monocultures exposed to coculture-conditioned medium or in epithelial–mesenchymal cocultures in which heterotypic cell–cell contact is prevented by an interposing filter. Immunohistochemical studies on cocultures treated with brefeldin A, an inhibitor of protein secretion, indicated both epithelial and mesenchymal cells synthesize laminin α1 chain upon heterotypic cell– cell contact. In a set of functional studies, embryonic lung explants were cultured in the presence of monoclonal antibodies to laminin α1, α2, and β/γ chains. Lung explants exposed to monoclonal antibodies to laminin α1 chain exhibited alterations in peribronchial cell shape and decreased smooth muscle development, as indicated by low levels of smooth muscle α actin and desmin. Taken together, our studies suggest that laminin α1 chain synthesis is regulated by epithelial–mesenchymal interaction and may play a role in airway smooth muscle development. 相似文献
99.
Cinzia Scambi Sara Ugolini T. Sakari Jokiranta Lucia De Franceschi Oscar Bortolami Valentina La Verde Patrizia Guarini Paola Caramaschi Viviana Ravagnani Guido Martignoni Chiara Colato Serena Pedron Fabio Benedetti Marco Sorio Fabio Poli Domenico Biasi 《PloS one》2015,10(2)
ObjectiveThe role of complement system in the pathogenesis of systemic sclerosis (SSc) has been debated during the last decade but an evident implication in this disease has never been found. We carried out an explorative study on SSc patients to evaluate the expression of soluble and local C5b-9 complement complex and its relation with a complement regulator, the Membrane Cofactor Protein (MCP, CD46) on skin vascular bed as target distinctive of SSc disease. We also analyzed two polymorphic variants in the complement activation gene cluster involving the MCP region.MethodsC5b-9 plasma levels of SSc patients and healthy subjects were analyzed by ELISA assay. Archival skin biopsies of SSc patients and controls were subjected to immunofluorescence analysis to detect C5b-9 and MCP on vascular endothelial cells. The expression of MCP was validated by immunoblot analysis with specific antibody. Polymorphic variants in the MCP gene promoter were tested by a quantitative PCR technique-based allelic discrimination method.ResultsEven though circulating levels of C5b-9 did not differ between SSc and controls, C5b-9 deposition was detected in skin biopsies of SSc patients but not in healthy subjects. MCP was significantly lower in skin vessels of SSc patients than in healthy controls and was associated with the over-expression of two polymorphic variants in the MCP gene promoter, which has been related to more aggressive phenotypes in other immune-mediated diseases.ConclusionsOur results firsty document the local complement activation with an abnormal expression of MCP in skin vessels of SSc patients, suggesting that a subset of SSc patients might be exposed to more severe organ complications and clinical evolution due to abnormal local complement activation. 相似文献
100.
Francesco Cerritelli Gianfranco Pizzolorusso Cinzia Renzetti Vincenzo Cozzolino Marianna D’Orazio Mariacristina Lupacchini Benedetta Marinelli Alessandro Accorsi Chiara Lucci Jenny Lancellotti Silvia Ballabio Carola Castelli Daniela Molteni Roberto Besana Lucia Tubaldi Francesco Paolo Perri Paola Fusilli Carmine D’Incecco Gina Barlafante 《PloS one》2015,10(5)
BackgroundDespite some preliminary evidence, it is still largely unknown whether osteopathic manipulative treatment improves preterm clinical outcomes.ResultsA total of 695 newborns were randomly assigned to either the study group (n= 352) or the control group (n=343). A statistical significant difference was observed between the two groups for the primary outcome (13.8 and 17.5 days for the study and control group respectively, p<0.001, effect size: 0.31). Multivariate analysis showed a reduction of the length of stay of 3.9 days (95% CI -5.5 to -2.3, p<0.001). Furthermore, there were significant reductions with treatment as compared to usual care in cost (difference between study and control group: 1,586.01€; 95% CI 1,087.18 to 6,277.28; p<0.001) but not in daily weight gain. There were no complications associated to the intervention.ConclusionsOsteopathic treatment reduced significantly the number of days of hospitalization and is cost-effective on a large cohort of preterm infants. 相似文献