全文获取类型
收费全文 | 842篇 |
免费 | 41篇 |
出版年
2024年 | 2篇 |
2022年 | 3篇 |
2021年 | 13篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 16篇 |
2017年 | 6篇 |
2016年 | 19篇 |
2015年 | 25篇 |
2014年 | 46篇 |
2013年 | 59篇 |
2012年 | 73篇 |
2011年 | 75篇 |
2010年 | 46篇 |
2009年 | 34篇 |
2008年 | 55篇 |
2007年 | 49篇 |
2006年 | 46篇 |
2005年 | 40篇 |
2004年 | 48篇 |
2003年 | 38篇 |
2002年 | 40篇 |
2001年 | 12篇 |
2000年 | 5篇 |
1999年 | 11篇 |
1998年 | 10篇 |
1997年 | 2篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 8篇 |
1985年 | 2篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1973年 | 4篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有883条查询结果,搜索用时 31 毫秒
161.
Assessing uncertainties in crop and pasture ensemble model simulations of productivity and N2O emissions
下载免费PDF全文
![点击此处可从《Global Change Biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Fiona Ehrhardt Jean‐François Soussana Gianni Bellocchi Peter Grace Russel McAuliffe Sylvie Recous Renáta Sándor Pete Smith Val Snow Massimiliano de Antoni Migliorati Bruno Basso Arti Bhatia Lorenzo Brilli Jordi Doltra Christopher D. Dorich Luca Doro Nuala Fitton Sandro J. Giacomini Brian Grant Matthew T. Harrison Stephanie K. Jones Miko U. F. Kirschbaum Katja Klumpp Patricia Laville Joël Léonard Mark Liebig Mark Lieffering Raphaël Martin Raia S. Massad Elizabeth Meier Lutz Merbold Andrew D. Moore Vasileios Myrgiotis Paul Newton Elizabeth Pattey Susanne Rolinski Joanna Sharp Ward N. Smith Lianhai Wu Qing Zhang 《Global Change Biology》2018,24(2):e603-e616
Simulation models are extensively used to predict agricultural productivity and greenhouse gas emissions. However, the uncertainties of (reduced) model ensemble simulations have not been assessed systematically for variables affecting food security and climate change mitigation, within multi‐species agricultural contexts. We report an international model comparison and benchmarking exercise, showing the potential of multi‐model ensembles to predict productivity and nitrous oxide (N2O) emissions for wheat, maize, rice and temperate grasslands. Using a multi‐stage modelling protocol, from blind simulations (stage 1) to partial (stages 2–4) and full calibration (stage 5), 24 process‐based biogeochemical models were assessed individually or as an ensemble against long‐term experimental data from four temperate grassland and five arable crop rotation sites spanning four continents. Comparisons were performed by reference to the experimental uncertainties of observed yields and N2O emissions. Results showed that across sites and crop/grassland types, 23%–40% of the uncalibrated individual models were within two standard deviations (SD) of observed yields, while 42 (rice) to 96% (grasslands) of the models were within 1 SD of observed N2O emissions. At stage 1, ensembles formed by the three lowest prediction model errors predicted both yields and N2O emissions within experimental uncertainties for 44% and 33% of the crop and grassland growth cycles, respectively. Partial model calibration (stages 2–4) markedly reduced prediction errors of the full model ensemble E‐median for crop grain yields (from 36% at stage 1 down to 4% on average) and grassland productivity (from 44% to 27%) and to a lesser and more variable extent for N2O emissions. Yield‐scaled N2O emissions (N2O emissions divided by crop yields) were ranked accurately by three‐model ensembles across crop species and field sites. The potential of using process‐based model ensembles to predict jointly productivity and N2O emissions at field scale is discussed. 相似文献
162.
Daniela Bonetti Francesca Troilo Maurizio Brunori Sonia Longhi Stefano Gianni 《Biophysical journal》2018,114(8):1889-1894
The mechanism of interaction of an intrinsically disordered protein (IDP) with its physiological partner is characterized by a disorder-to-order transition in which a recognition and a binding step take place. Even if the mechanism is quite complex, IDPs tend to bind their partner in a cooperative manner such that it is generally possible to detect experimentally only the disordered unbound state and the structured complex. The interaction between the disordered C-terminal domain of the measles virus nucleoprotein (NTAIL) and the X domain (XD) of the viral phosphoprotein allows us to detect and quantify the two distinct steps of the overall reaction. Here, we analyze the robustness of the folding of NTAIL upon binding to XD by measuring the effect on both the folding and binding steps of NTAIL when the structure of XD is modified. Because it has been shown that wild-type XD is structurally heterogeneous, populating an on-pathway intermediate under native conditions, we investigated the binding to 11 different site-directed variants of NTAIL of one particular variant of XD (I504A XD) that populates only the native state. Data reveal that the recognition and the folding steps are both affected by the structure of XD, indicating a highly malleable pathway. The experimental results are briefly discussed in the light of previous experiments on other IDPs. 相似文献
163.
Eva De Mol Elzbieta Szulc Claudio Di Sanza Paula Martínez-Cristóbal Carlos W. Bertoncini R. Bryn Fenwick Marta Frigolé-Vivas Marianela Masín Irene Hunter Víctor Buzón Isabelle Brun-Heath Jesús García Gianni De Fabritiis Eva Estébanez-Perpiñá Iain J. McEwan Ángel R. Nebreda Xavier Salvatella 《Structure (London, England : 1993)》2018,26(1):145-152.e3
164.
Marco R. Oggioni Christopher G. Dowson John Maynard Smith Roberta Provvedi Gianni Pozzi 《Plasmid》1996,35(3):156-163
Tetracycline resistance genes of the M class,tet(M), are typically found on mobile genetic elements as the conjugative transposons of gram-positive bacteria. By comparing the sequences of eight differenttet(M) genes (fromEnterococcus faecalis, Streptococcus pneumoniae, Staphylococcus aureus, Ureaplasma urealyticum,andNeisseria), a mosaic structure was detected which could be traced to two distinct alleles. The two alleles displayed a divergence of 8% and a different G/C content. The block structure of these genes provides evidence for the contribution of homologous recombination to the evolution and the heterogeneity of thetet(M) locus. Unlike described cases of chromosomally located mosaic loci,tet(M) is a relatively recently acquired determinant in the species examined and it would appear that mosaic structure withintet(M) has evolved after acquisition of the gene by the mobile genetic elements upon which it is located. 相似文献
165.
Gianni Galaverna Francesco Pant Arnaldo Dossena Rosangela Marchelli Franca Bigi 《Chirality》1995,7(5):331-336
Copper(II) complexes of (S)-phenylalaninamide have been successfully used for the direct enantiomeric separation of unmodified (R,S)-α-hydroxy acids in reversed phase high-performance liquid chromatography (RP-HPLC). The effect of various parameters (pH, eluent polarity, selector concentration) on enantioselectivity is discussed. Evidence is provided that a mechanism of ligand exchange is actually occurring during the chromatographic separation. The method is very convenient and easy to use, and the chiral selector is commercially available and can be recovered at the end of the analysis. A conventional achiral RP-ODS-2 column is used and no pretreatment of the samples is required. This method allows the accurate determination of the enantiomeric excess of α-hydroxy acids in synthetic and biological samples. © 1995 Wiley-Liss, Inc. 相似文献
166.
Mohit?ParekhEmail author Alessandro?Ruzza Stefano?Ferrari Gianni?Salvalaio Hossein?Elbadawy Diego?Ponzin Eugenio?Lipari 《Cell and tissue banking》2016,17(2):233-239
To investigate the de-orientation effect of DSAEK grafts by observing the cross patterns and polarization power of human donor corneas using a polarizing device (Lumaxis®). Forty human donor corneas were placed in small petri-plates with epithelial side facing up. Polarizing power (arbitrary unit) and crosses were monitored and recorded by the software. The tissue was marked at ‘Superior’ position to ensure that the base and the polarizer are in alignment with each other after the cut. The anterior lamellar cut was performed using microkeratome. The lenticule was placed back in the same position as marked to mimic the alignment. The tissue was further rotated by 45° ensuring that the base of the cornea and the polarizer were in alignment. The polarization power and ‘crosses’ were identified at each step. The average of forty corneas from pre-cut to post-45° angular change showed statistically significant difference (p < 0.05) in terms of polarizing power. The cross-shaped pattern deformed and lost the sharpness towards 45° angle. However, multiple variances in terms of ‘cross-patterns’ were observed throughout the study. Lumaxis® was able to determine the worst quality tissue in terms of polarization (no black zone and crosses). Despite the quality of cross pattern which can be used as an additional objective parameter to evaluate the optical properties of the corneal tissue, this preliminary study needs to be further justified in terms of clinical relevance whether polarization changes with oriented or de-oriented grafts have any effects and consequences on the visual acuity. 相似文献
167.
Grazia Fazio Carles Gaston‐Massuet Laura Rachele Bettini Federica Graziola Valeria Scagliotti Anna Cereda Luca Ferrari Mara Mazzola Gianni Cazzaniga Antonio Giordano Franco Cotelli Gianfranco Bellipanni Andrea Biondi Angelo Selicorni Anna Pistocchi Valentina Massa 《Journal of cellular physiology》2016,231(3):613-622
168.
Unintentional injuries cause much of the global mortality burden, with the workplace being a common accident setting. Even in high-income economies, occupational injury figures remain remarkably high. Because risk factors for occupational injuries are prone to confounding, the present research takes a comprehensive approach. To better understand the occurrence of occupational injuries, sociodemographic factors and work- and health-related factors are tested simultaneously. Thus, the present analysis aims to develop a comprehensive epidemiological model that facilitates the explanation of varying injury rates in the workplace. The representative phone survey German Health Update 2010 provides information on medically treated occupational injuries sustained in the year prior to the interview. Data were collected on sociodemographics, occupation, working conditions, health-related behaviors, and chronic diseases. For the economically active population (18–70 years, n = 14,041), the 12-month prevalence of occupational injuries was calculated with a 95% confidence interval (CI). Blockwise multiple logistic regression was applied to successively include different groups of variables. Overall, 2.8% (95% CI 2.4–3.2) of the gainfully employed population report at least one occupational injury (women: 0.9%; 95% CI 0.7–1.2; men: 4.3%; 95% CI 3.7–5.0). In the fully adjusted model, male gender (OR 3.16) and age 18–29 (OR 1.54), as well as agricultural (OR 5.40), technical (OR 3.41), skilled service (OR 4.24) or manual (OR 5.12), and unskilled service (OR 3.13) or manual (OR 4.97) occupations are associated with higher chances of occupational injuries. The same holds for frequent stressors such as heavy carrying (OR 1.78), working in awkward postures (OR 1.46), environmental stress (OR 1.48), and working under pressure (OR 1.41). Among health-related variables, physical inactivity (OR 1.47) and obesity (OR 1.73) present a significantly higher chance of occupational injuries. While the odds for most work-related factors were as expected, the associations for health-related factors such as smoking, drinking, and chronic diseases were rather weak. In part, this may be due to context-specific factors such as safety and workplace regulations in high-income countries like Germany. This assumption could guide further research, taking a multi-level approach to international comparisons. 相似文献
169.
Genetic differences in cystic fibrosis patients with and without pancreatic insufficiency 总被引:1,自引:1,他引:0
Maurizio Ferrari Mariano Antonelli Fiorenza Bellini Graziella Borgo Ornella Castiglione Lauretta Curcio Bruno Dallapiccola Marcella Devoto Xavier Estivill Paolo Gasparini Annamaria Giunta Lore Marianelli Gianni Mastella Giuseppe Novelli Pierfranco Pignatti Luca Romano Giovanni Romeo Manuela Seia Robert Williamson 《Human genetics》1990,84(5):435-438
Summary To determine the number and frequency of mutations that occur at the cystic fibrosis locus (CF), we have examined the allele and haplotype frequencies of eight polymorphic DNA markers linked to CF in 163 Italian patients who were sub-divided according to their clinical presentations. The distribution of haplotypes for the tightly linked polymorphisms KM.19 and XV-2c differ significantly between patients with and those without pancreatic insufficiency. The haplotype found most commonly in CF chromosomes occurs much more frequently in pancreatic insufficient than in pancreatic sufficient patients. Among the 19 pancreatic sufficient patients, 6 (31.6%) show at least one copy of the rare KM.19 = 1, XV-2c = 2 haplotype, as against 16 of 138 patients (11.6%) with pancreatic insufficiency. In addition, only 5 pancreatic sufficient patients (26.3%) are homozygous for the common 2,1 haplotype, as compared with 88 patients (63.8%) with pancreatic insufficiency. These findings support the hypothesis of allelic heterogeneity at a single locus in CF and suggest that different mutations underlie the presence or absence of pancreatic insufficiency in this disorders. 相似文献
170.