全文获取类型
收费全文 | 2534篇 |
免费 | 349篇 |
出版年
2022年 | 18篇 |
2021年 | 37篇 |
2020年 | 27篇 |
2019年 | 28篇 |
2018年 | 42篇 |
2017年 | 35篇 |
2016年 | 65篇 |
2015年 | 108篇 |
2014年 | 114篇 |
2013年 | 135篇 |
2012年 | 165篇 |
2011年 | 141篇 |
2010年 | 85篇 |
2009年 | 90篇 |
2008年 | 133篇 |
2007年 | 108篇 |
2006年 | 127篇 |
2005年 | 144篇 |
2004年 | 125篇 |
2003年 | 110篇 |
2002年 | 109篇 |
2001年 | 44篇 |
2000年 | 34篇 |
1999年 | 51篇 |
1998年 | 32篇 |
1997年 | 35篇 |
1996年 | 48篇 |
1995年 | 45篇 |
1994年 | 33篇 |
1993年 | 33篇 |
1992年 | 40篇 |
1991年 | 31篇 |
1990年 | 35篇 |
1989年 | 43篇 |
1988年 | 26篇 |
1987年 | 24篇 |
1986年 | 24篇 |
1985年 | 25篇 |
1984年 | 25篇 |
1983年 | 15篇 |
1982年 | 25篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1977年 | 17篇 |
1976年 | 13篇 |
1975年 | 16篇 |
1974年 | 20篇 |
1973年 | 15篇 |
1968年 | 11篇 |
1966年 | 14篇 |
排序方式: 共有2883条查询结果,搜索用时 15 毫秒
891.
Martin Knapp Anita Patel Claire Curran Eric Latimer Jocelyn Catty Thomas Becker Robert E. Drake Angelo Fioritti Reinhold Kilian Christoph Lauber Wulf Rössler Toma Tomov Jooske van Busschbach Adelina Comas‐Herrera Sarah White Durk Wiersma Tom Burns 《World psychiatry》2013,12(1):60-68
A high proportion of people with severe mental health problems are unemployed but would like to work. Individual Placement and Support (IPS) offers a promising approach to establishing people in paid employment. In a randomized controlled trial across six European countries, we investigated the economic case for IPS for people with severe mental health problems compared to standard vocational rehabilitation. Individuals (n=312) were randomized to receive either IPS or standard vocational services and followed for 18 months. Service use and outcome data were collected. Cost‐effectiveness analysis was conducted with two primary outcomes: additional days worked in competitive settings and additional percentage of individuals who worked at least 1 day. Analyses distinguished country effects. A partial cost‐benefit analysis was also conducted. IPS produced better outcomes than alternative vocational services at lower cost overall to the health and social care systems. This pattern also held in disaggregated analyses for five of the six European sites. The inclusion of imputed values for missing cost data supported these findings. IPS would be viewed as more cost‐effective than standard vocational services. Further analysis demonstrated cost‐benefit arguments for IPS. Compared to standard vocational rehabilitation services, IPS is, therefore, probably cost‐saving and almost certainly more cost‐effective as a way to help people with severe mental health problems into competitive employment. 相似文献
892.
Lorena Itatí Iba?ez Kenny Roose Marina De Filette Michael Schotsaert Jessica De Sloovere Stefan Roels Charlotte Pollard Bert Schepens Johan Grooten Walter Fiers Xavier Saelens 《PloS one》2013,8(3)
The ectodomain of influenza A matrix protein 2 (M2e) is a candidate for a universal influenza A vaccine. We used recombinant Hepatitis B core antigen to produce virus-like particles presenting M2e (M2e-VLPs). We produced the VLPs with and without entrapped nucleic acids and compared their immunogenicity and protective efficacy. Immunization of BALB/c mice with M2e-VLPs containing nucleic acids induced a stronger, Th1-biased antibody response compared to particles lacking nucleic acids. The former also induced a stronger M2e-specific CD4+ T cell response, as determined by ELISPOT. Mice vaccinated with alum-adjuvanted M2e-VLPs containing the nucleic acid-binding domain were better protected against influenza A virus challenge than mice vaccinated with similar particles lacking this domain, as deduced from the loss in body weight following challenge with X47 (H3N2) or PR/8 virus. Challenge of mice that had been immunized with M2e-VLPs with or without nucleic acids displayed significantly lower mortality, morbidity and lung virus titers than control-immunized groups. We conclude that nucleic acids present in M2e-VLPs correlate with improved immune protection. 相似文献
893.
Aims
Alterations in properties of the bladder with maturation are relevant physiologically and pathophysiologically. The aim of this study was to investigate alterations in bladder properties with maturation in juvenile vs. adult pig, focussing on differences between layers of the bladder wall (mucosa vs. detrusor) and the presence and functional contribution of interstitial cells (ICs).Methods
Basal and cholinergic-induced phasic contractions (PCs) in mucosal and denuded-detrusor strips from juvenile and adult pigs were assessed. Expression of c-kit, a marker of ICs, was investigated in the mucosa and the detrusor layers of the pig bladder. The functional role of ICs in mediating PCs was examined using imatinib.Results
Mucosal strips from juvenile and adult pig bladders demonstrated basal PCs whilst denuded-detrusor strips did not. PCs of mucosal strips from juvenile pigs were significantly greater than those from adult bladders. Immunoreactivity for c-kit was detected in mucosa and detrusor layers of pig bladder. Histological studies demonstrated a distinct layer of smooth muscle between the urothelium and bladder detrusor, termed the muscularis mucosa. Imatinib was only effective in inhibiting PCs in mucosal strips from juvenile pigs. Imatinib inhibited the carbachol-induced PCs of both juvenile and adult denuded-detrusor strips, although strips from juvenile bladders demonstrated a trend towards being more sensitive to this inhibition.Conclusions
We confirm the presence of c-kit positive ICs in pig urinary bladder. The enhanced PCs of mucosal strips from juvenile animals could be due to altered properties of ICs or the muscularis mucosa in the bladders of these animals. 相似文献894.
895.
Karel-Jan D. F. Lensen Alexandre E. Voskuyl Conny J. van der Laken Emile F. I. Comans Dirkjan van Schaardenburg Alex B. Arntzenius Ton Zwijnenburg Frank Stam Michelle Gompelman Friso M. v.d. Zant Anneke Q. A. van Paassen Bert J. Voerman Frits Smit Sander Anten Carl E. Siegert Arjen Binnerts Yvo M. Smulders 《PloS one》2013,8(3)
Patients with an elevated erythrocyte sedimentation rate (ESR) and non-specific symptoms often pose a diagnostic dilemma. PET/CT visualises infection, inflammation and malignancy, all of which may cause elevated ESR. The objective of this study was to determine the contribution of 18F-fluorodeoxglucose positron emission tomography (PET/CT) in the diagnostic work-up of referred patients with an elevated ESR, in whom initial routine evaluation did not reveal a diagnosis. We conducted a combined retrospective (A) and prospective (B) study in elderly (>50 years) patients with a significantly elevated ESR of≥50 mm/h and non-specific complaints. In study A, 30 patients were included. Malignancy (8 patients), auto-inflammatory disease (8 patients, including 5 with large-vessel vasculitis) and infection (3 patients) were suggested by PET/CT. Two scans showed non-specific abnormalities and 9 scans were normal. Of the 21 abnormal PET/CT results, 12 diagnoses were independently confirmed and two alternative diagnosis were made. Two diagnoses were established in patients with a normal scan. In study B, 58 patients in whom a prior protocolised work-up was non-diagnostic, were included. Of these, 25 PET/CT-scans showed suspected auto-inflammatory disease, particularly large-vessel vasculitis (14 cases). Infection and malignancy was suspected in 5 and 3 cases, respectively. Seven scans demonstrated non-specific abnormalities, 20 were normal. Of the 40 abnormal PET/CT results, 22 diagnoses were confirmed, 3 alternative diagnoses were established. Only one diagnosis was established in the 20 patients with a normal scan. In both studies, the final diagnosis was based on histology, clinical follow-up, response to therapy or additional imaging. In conclusion, PET/CT may be of potential value in the diagnostic work-up of patients with elevated ESR if routine evaluation reveals no diagnosis. In particular, large-vessel vasculitis appears to be a common finding. A normal PET/CT scan in these patients suggests that it is safe to follow a wait-and-see policy. 相似文献
896.
The present paper describes a method for the identification of intact high molecular weight glutenin subunits (HMW-GS), the quality determining proteins from the wheat storage proteome. The method includes isolation of HMW-GS from wheat flour, further separation of HMW-GS by reversed-phase high-performance liquid chromatography (RP-HPLC), and their subsequent molecular identification with electrospray ionization mass spectrometry using a quadrupole-time-of-flight mass analyzer. For HMW-GS isolation, wheat proteins were reduced and extracted from flour with 50% 1-propanol containing 1% dithiothreitol. HMW-GS were then selectively precipitated from the protein mixture by adjusting the 1-propanol concentration to 60%. The composition of the precipitated proteins was first evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis with Coomassie staining and RP-HPLC with ultraviolet detection. Besides HMW-GS (≥65%), the isolated proteins mainly contained ω5-gliadins. Secondly, the isolated protein fraction was analyzed by liquid chromatography-mass spectrometry. Optimal chromatographic separation of HMW-GS from the other proteins in the isolated fraction was obtained when the mobile phase contained 0.1% trifluoroacetic acid as ion-pairing agent. Individual HMW-GS were then identified by determining their molecular masses from the high-resolution mass spectra and comparing these with theoretical masses calculated from amino acid sequences. Using formic acid instead of trifluoroacetic acid in the mobile phase increased protein peak intensities in the base peak mass chromatogram. This allowed the detection of even traces of other wheat proteins than HMW-GS in the isolated fraction, but the chromatographic separation was inferior with a major overlap between the elution ranges of HMW-GS and ω-gliadins. Overall, the described method allows a rapid assessment of wheat quality through the direct determination of the HMW-GS composition and offers a basis for further top-down proteomics of individual HMW-GS and the entire wheat glutenin fraction. 相似文献
897.
Giedre Gefenaite Margot Tacken Jens Bos Irina Stirbu-Wagner Joke C. Korevaar Ronald P. Stolk Bert Wolters Marc Bijl Maarten J. Postma Jan Wilschut Kristin L. Nichol Eelko Hak 《PloS one》2013,8(6)
Introduction
Because of variability in published A(H1N1)pdm09 influenza vaccine effectiveness estimates, we conducted a study in the adults belonging to the risk groups to assess the A(H1N1)pdm09 MF59-adjuvanted influenza vaccine effectiveness.Methods
VE against influenza and/or pneumonia was assessed in the cohort study (n>25000), and vaccine effectiveness against laboratory-confirmed A(H1N1)pdm09 influenza was assessed in a matched case-control study (16 pairs). Odds ratios (OR) and their 95% confidence intervals (95% CI) were calculated by using multivariate logistic regression; vaccine effectiveness was estimated as (1-odds ratio)*100%.Results
Vaccine effectiveness against laboratory-confirmed A(H1N1)pdm09 influenza and influenza and/or pneumonia was 98% (84–100%) and 33% (2–54%) respectively. The vaccine did not prevent influenza and/or pneumonia in 18–59 years old subjects, and was 49% (16–69%) effective in 60 years and older subjects.Conclusions
Even though we cannot entirely rule out that selection bias, residual confounding and/or cross-protection has played a role, the present results indicate that the MF59-adjuvanted A(H1N1)pdm09 influenza vaccine has been effective in preventing laboratory-confirmed A(H1N1)pdm09 influenza and influenza and/or pneumonia, the latter notably in 60 years and older subjects. 相似文献898.
Jan-Willem E. M. Sels Bert Rutten Thijs C. van Holten Marieke A. K. Hillaert Johannes Waltenberger Nico H. J. Pijls Gerard Pasterkamp Philip G. de Groot Mark Roest 《PloS one》2013,8(12)
Background
The presence of stenoses that significantly impair blood flow and cause myocardial ischemia negatively affects prognosis of patients with stable coronary artery disease. Altered platelet reactivity has been associated with impaired prognosis of stable coronary artery disease. Platelets are activated and form complexes with leukocytes in response to microshear gradients caused by friction forces on the arterial wall or flow separation. We hypothesized that the presence of significantly flow-limiting stenoses is associated with altered platelet reactivity and formation of platelet-leukocyte complexes.Methods
One hundred patients with stable angina were studied. Hemodynamic significance of all coronary stenoses was assessed with Fractional Flow Reserve (FFR). Patients were classified FFR-positive (at least one lesion with FFR≤0.75) or FFR-negative (all lesions FFR>0.80). Whole blood samples were stimulated with increasing concentrations of ADP, TRAP, CRP and Iloprost with substimulatory ADP. Expression of P-selectin as platelet activation marker and platelet–leukocyte complexes were measured by flowcytometry. Patients were stratified on clopidogrel use. FFR positive and negative patient groups were compared on platelet reactivity and platelet-leukocyte complexes.Results
Platelet reactivity between FFR-positive patients and FFR-negative patients did not differ. A significantly lower percentage of circulating platelet-neutrophil complexes in FFR-positive patients and a similar non-significant decrease in percentage of circulating platelet-monocyte complexes in FFR-positive patients was observed.Conclusion
The presence of hemodynamically significant coronary stenoses does not alter platelet reactivity but is associated with reduced platelet-neutrophil complexes in peripheral blood of patients with stable coronary artery disease. 相似文献899.
M. Christien P. Absil Louise J.A. Gerringa Bert Th. Wolterbeek 《Chemical Speciation and Bioavailability》2013,25(4):119-128
AbstractThe radiotracer 64Cu was used to assess the influence of natural organic ligands on the bioavailability of copper. Biological availability of the 64Cu-complexes was measured by accumulation in the bivalve Macoma balthica. The experiments were carried out in April as well as in February with water from the relatively clean Oosterschelde Sea arm and the relatively polluted Westerschelde estuary. Adsorption onto shells, as well as uptake in tissues was assessed at salinities of 10‰ and 30‰. Simultaneously with the exposure experiments, ligand characteristics of the natural waters were assessed. High ligand concentrations, as occurring in the Westerschelde around February, reduced 64Cu (320 nM) uptake by more than 50%, in spite of the much lower salinity in the Westerschelde water. At the low salinity, uptake was increased slightly in Westerschelde water, but considerably in Oosterschelde water. This implies that at low ambient ligand concentrations (during the whole year in Oosterschelde water and in the summer period also in Westerschelde water) the influence of salinity on 64Cu uptake is more pronounced. 相似文献
900.
Pascal M. W. Drake Luisa de Moraes Madeira Tim H. Szeto Julian K-C. Ma 《Transgenic research》2013,22(6):1225-1229
The marshmallow plant (Althaea officinalis L.) has been used for centuries in medicine and other applications. Valuable secondary metabolites have previously been identified in Agrobacterium rhizogenes-generated transgenic ‘hairy’ roots in this species. In the present study, transgenic roots were produced in A. officinalis using A. rhizogenes. In addition to wild-type lines, roots expressing the anti-human immunodeficiency virus microbicide candidate, cyanovirin-N (CV-N), were generated. Wild-type and CV-N root lines were transferred to liquid culture and increased in mass by 49 and 19 % respectively over a 7 day culture period. In the latter, the concentration of CV-N present in the root tissue was 2.4 μg/g fresh weight, with an average secretion rate into the growth medium of 0.02 μg/ml/24 h. A. officinalis transgenic roots may therefore in the future be used not only as a source of therapeutic secondary metabolites, but also as an expression system for the production of recombinant pharmaceuticals. 相似文献