全文获取类型
收费全文 | 3546篇 |
免费 | 257篇 |
出版年
2023年 | 16篇 |
2022年 | 21篇 |
2021年 | 100篇 |
2020年 | 49篇 |
2019年 | 64篇 |
2018年 | 98篇 |
2017年 | 75篇 |
2016年 | 125篇 |
2015年 | 210篇 |
2014年 | 226篇 |
2013年 | 283篇 |
2012年 | 322篇 |
2011年 | 309篇 |
2010年 | 201篇 |
2009年 | 162篇 |
2008年 | 241篇 |
2007年 | 225篇 |
2006年 | 193篇 |
2005年 | 175篇 |
2004年 | 168篇 |
2003年 | 166篇 |
2002年 | 133篇 |
2001年 | 23篇 |
2000年 | 17篇 |
1999年 | 17篇 |
1998年 | 27篇 |
1997年 | 15篇 |
1996年 | 17篇 |
1995年 | 8篇 |
1994年 | 14篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 15篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1970年 | 2篇 |
1966年 | 1篇 |
1964年 | 2篇 |
1909年 | 1篇 |
排序方式: 共有3803条查询结果,搜索用时 125 毫秒
31.
Umberto Nicosia Fabio Massimo Petti Gianluca Perugini Simone D’Orazi Porchetti Eva Sacchi Maria Alessandra Conti 《Ichnos》2013,20(1-2):69-90
A really unexpected finding of sauropod and theropod footprints in southern Latium raises to four the number of the trampled levels recognized in central and southern Italy. After the recent findings in Latest Jurassic and Early, mid and Late Cretaceous carbonate platform deposits of the Periadriatic region, dinosaur footprints seem to provide very important paleogeographic constraints for reconstructing the geodynamic history of the Mediterranean area. The presence of a varied ichnoassociation makes acceptance of the current paleogeographic models concerning the relative and absolute position of the Laziale-Abruzzese-Campano and of Apulian-Dinaric domains during the Late Cretaceous more and more problematic. Dinosaur footprints, combined with other paleontological data, demonstrate that these areas were never completely pulled apart by deep seaways, while frequent or continuous links between them, and to southern and northern mainlands, probably persisted. These data also allowed us to improve our understanding of the timing of the Mesozoic plate motion in this segment of the Western Tethys. 相似文献
32.
Sergio Neri Santo Signorelli Davide Pulvirenti Barbara Mauceri Danila Cilio Fabio Bordonaro 《Free radical research》2013,47(6):615-618
To assess whether pathogenic endothelial dysfunction is involved in acute idiopathic tinnitus we enrolled 44 patients and 25 healthy volunteers. In blood from the internal jugular vein and brachial vein we determined malonaldehyde, 4-hydroxynonenal, mieloperoxidase, glutathione peroxidase, nitric oxide, l-arginine and l-ornitine, thrombomodulin (TM) and von Willebrand factor (vWF) activity during tinnitus and asymptomatic period.Higher plasma concentrations of oxidative markers and l-arginine, and lower nitric oxide and l-ornitine levels were observed in jugular blood of patients with tinnitus, there being a significant difference between brachial and jugular veins. TM and vWF activity were significantly higher in patients' jugular blood than in brachial blood.Our results suggest oxidant, TM, vWF activity production are increased and nitric oxide production reduced in brain circulation reflux blood of patients with acute tinnitus. These conditions are able to cause a general cerebro-vascular endothelial dysfunction, which in turn induce a dysfunction of microcirculation in the inner ear. 相似文献
33.
Angela Maria Amorini Giuseppe Lazzarino Fabio Galvano Giovanna Fazzina Barbara Tavazzi Giacomo Galvano 《Free radical research》2013,47(4):453-460
The cyanidin-3- O - g -glucopyranoside (C-3-G) antioxidant capacity towards reactive oxygen species (ROS)-mediated damages was assessed in tissue and cells submitted to increased oxidative stress. In the isolated ischemic and reperfused rat heart, 10 or 30 w M C-3-G protected from both lipid peroxidation (66.7 and 94% inhibition of malondialdehyde (MDA) generation in 10 and 30 w M C-3-G-reperfused hearts, respectively, in comparison with control reperfused hearts) and energy metabolism impairment (higher ATP concentration in 10 and 30 w M C-3-G-reperfused hearts than in control reperfused hearts). These effects were associated to C-3-G permeation within myocardial cells, as indicated by results obtained in the isolated rat heart perfused for 30 min in the recirculating Langendorff mode under normoxia with 10 and 30 w M C-3-G. Protective effects were exerted, in a dose-dependent manner, by C-3-G also in 2 mM hydrogen peroxide-treated human erythrocytes. With respect to MDA formation, an apparent IC 50 of 5.12 w M was calculated for C-3-G (the polyphenol resveratrol used for comparison showed an apparent IC 50 of 38.43 w M). The general indications are that C-3-G (largely diffused in dietary plants and fruits, such as pigmented oranges very common in the Mediterranean diet) represents a powerful natural antioxidant with beneficial effects in case of increased oxidative stress, and at pharmacological concentrations it is able to decrease tissue damages occurring in myocardial ischemia and reperfusion. 相似文献
34.
Abstract A. Kerner is correctly the author of the name Iris cengialti previously ascribed to Ambrosi, and consequently the type of the species is here selected, as lectotype, among Kerner's original material kept in WU. 相似文献
35.
36.
37.
Abstract In August 2003, dense turfs formed by the filamentous red alga Womersleyella setacea (Hollenberg) R. E. Norris were found in the open part of the Bay of Boka Kotorska, on the shore of Montenegro (southern Adriatic Sea). The habitat and morphology of the alga are described and the impact of the massive development of this species on the structure of the algal communities is discussed. 相似文献
38.
Georgios Ioannis Karras Marco Fumasoni Grzegorz Sienski Fabio Vanoli Dana Branzei Stefan Jentsch 《Molecular cell》2013,49(3):536-546
Highlights? 9-1-1 and Exo1 are components of the error-free RAD6 pathway ? 9-1-1 promotes postreplicative template switching ? Polyubiquitylated PCNA and 9-1-1 cooperate in the error-free RAD6 pathway ? 9-1-1’s role in the error-free RAD6 pathway is uncoupled from checkpoint functions 相似文献
39.
Fabio Casu Rebecca K. Harston Maria A. Chiacchio Giuseppe Gumina 《Nucleosides, nucleotides & nucleic acids》2013,32(3):224-235
2′-Modified inosine analogs have been synthesized from 6-chloropurine riboside via 6-dimethylaminopurine or 6-benzyloxypurine intermediates. The dimethylaminopurine intermediate was obtained via an unusually facile dimethylamine transfer from dimethylformamide. Graphical Abstract: 相似文献
40.
Within an integrated management plan for contaminated site remediation at a given territorial scale, the performance of treatability tests could be useful and/or expressly requested by the control authority on a site-specific basis to evaluate the overall feasibility of a given remedial option. The thermal desorption process appears to be a favorable treatment technology for organic contaminants. In this context, a particular lab-scale, indirectly heated desorber for treatability tests was originally developed and first applied to natural soils with different textures (silty sand, loam, silt clay, and clayey silt) that were “ad hoc” highly contaminated with diesel oil at various desorption process conditions (heating temperature in the range of 300–390°C, and reactor retention time in the range of 40–120 min). The Italian soil threshold level for heavy hydrocarbons (C > 12) of 50 mg kg?1 (dry matter) was assumed to be the successful goal of the treatability studies. In addition to the individuation of the favorable desorption process conditions for each soil, also in terms of a composite evaluation of heating temperature and retention time, the comparative experimental results provided useful indications of the possible influence of soil texture, the reduction of initial soil organic matter, and the evaluation of kinetic rate constants. 相似文献