全文获取类型
收费全文 | 2232篇 |
免费 | 191篇 |
国内免费 | 1篇 |
出版年
2024年 | 2篇 |
2023年 | 22篇 |
2022年 | 8篇 |
2021年 | 45篇 |
2020年 | 35篇 |
2019年 | 48篇 |
2018年 | 61篇 |
2017年 | 63篇 |
2016年 | 79篇 |
2015年 | 140篇 |
2014年 | 138篇 |
2013年 | 165篇 |
2012年 | 194篇 |
2011年 | 175篇 |
2010年 | 121篇 |
2009年 | 104篇 |
2008年 | 132篇 |
2007年 | 121篇 |
2006年 | 133篇 |
2005年 | 114篇 |
2004年 | 91篇 |
2003年 | 90篇 |
2002年 | 86篇 |
2001年 | 37篇 |
2000年 | 16篇 |
1999年 | 20篇 |
1998年 | 19篇 |
1997年 | 14篇 |
1996年 | 12篇 |
1995年 | 19篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 12篇 |
1991年 | 10篇 |
1990年 | 14篇 |
1989年 | 9篇 |
1988年 | 16篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1978年 | 3篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有2424条查询结果,搜索用时 15 毫秒
21.
22.
Pere Fullana i Palmer Rita Puig Alba Bala Grau Baquero Jordi Riba Marco Raugei 《Journal of Industrial Ecology》2011,15(3):458-475
Life cycle assessment (LCA) is a widely accepted methodology to support decision‐making processes in which one compares alternatives, and that helps prevent shifting of environmental burdens along the value chain or among impact categories. According to regulation in the European Union (EU), the movement of waste needs to be reduced and, if unavoidable, the environmental gain from a specific waste treatment option requiring transport must be larger than the losses arising from transport. The EU explicitly recommends the use of LCA or life cycle thinking for the formulation of new waste management plans. In the last two revisions of the Industrial Waste Management Programme of Catalonia (PROGRIC), the use of a life cycle thinking approach to waste policy was mandated. In this article we explain the process developed to arrive at practical life cycle management (LCM) from what started as an LCA project. LCM principles we have labeled the “3/3” principle or the “good enough is best” principle were found to be essential to obtain simplified models that are easy to understand for legislators and industries, useful in waste management regulation, and, ultimately, feasible. In this article, we present the four models of options for the management of waste solvent to be addressed under Catalan industrial waste management regulation. All involved actors concluded that the models are sufficiently robust, are easy to apply, and accomplish the aim of limiting the transport of waste outside Catalonia, according to the principles of proximity and sufficiency. 相似文献
23.
24.
Sara Teller Clara Granell Manlio De Domenico Jordi Soriano Sergio Gómez Alex Arenas 《PLoS computational biology》2014,10(9)
The analysis of the activity of neuronal cultures is considered to be a good proxy of the functional connectivity of in vivo neuronal tissues. Thus, the functional complex network inferred from activity patterns is a promising way to unravel the interplay between structure and functionality of neuronal systems. Here, we monitor the spontaneous self-sustained dynamics in neuronal cultures formed by interconnected aggregates of neurons (clusters). Dynamics is characterized by the fast activation of groups of clusters in sequences termed bursts. The analysis of the time delays between clusters'' activations within the bursts allows the reconstruction of the directed functional connectivity of the network. We propose a method to statistically infer this connectivity and analyze the resulting properties of the associated complex networks. Surprisingly enough, in contrast to what has been reported for many biological networks, the clustered neuronal cultures present assortative mixing connectivity values, meaning that there is a preference for clusters to link to other clusters that share similar functional connectivity, as well as a rich-club core, which shapes a ‘connectivity backbone’ in the network. These results point out that the grouping of neurons and the assortative connectivity between clusters are intrinsic survival mechanisms of the culture. 相似文献
25.
Manel Puig-Domingo Raúl M. Luque Jordi L. Reverter Laura M. López-Sánchez Manuel D. Gahete Michael D. Culler Gonzalo Díaz-Soto Francisco Lome?a Mattia Squarcia José Luis Mate Mireia Mora Laureano Fernández-Cruz Oscar Vidal Antonio Alastrué Jose Balibrea Irene Halperin Dídac Mauricio Justo P. Casta?o 《PloS one》2014,9(1)
Somatostatin receptors (ssts) are expressed in thyroid cancer cells, but their biological significance is not well understood. The aim of this study was to assess ssts in well differentiated (WDTC) and poorly differentiated thyroid cancer (PDTC) by means of imaging and molecular tools and its relationship with the efficacy of somatostatin analog treatment. Thirty-nine cases of thyroid carcinoma were evaluated (20 PDTC and 19 WDTC). Depreotide scintigraphy and mRNA levels of sst-subtypes, including the truncated variant sst5TMD4, were carried out. Depreotide scans were positive in the recurrent tumor in the neck in 6 of 11 (54%) PDTC, and in those with lung metastases in 5/11 cases (45.4%); sst5TMD4 was present in 18/20 (90%) of PDTC, being the most densely expressed sst-subtype, with a 20-fold increase in relation to sst2. In WDTC, sst2 was the most represented, while sst5TMD4 was not found; sst2 was significantly increased in PDTC in comparison to WDTC. Five depreotide positive PDTC received octreotide for 3–6 months in a pilot study with no changes in the size of the lesions in 3 of them, and a significant increase in the pulmonary and cervical lesions in the other 2. All PDTC patients treated with octreotide showed high expression of sst5TMD4. ROC curve analysis demonstrated that only sst5TMD4 discriminates between PDTC and WDTC. We conclude that sst5TMD4 is overexpressed in PDTC and may be involved in the lack of response to somatostatin analogue treatment. 相似文献
26.
Santiago Esteban-Martín Jordi Silvestre-Ryan Carlos?W. Bertoncini Xavier Salvatella 《Biophysical journal》2013,105(5):1192-1198
Structural conversion of the presynaptic, intrinsically disordered protein α-synuclein into amyloid fibrils underlies neurotoxicity in Parkinson’s disease. The detailed mechanism by which this conversion occurs is largely unknown. Here, we identify a discrete pattern of transient tertiary interactions in monomeric α-synuclein involving amino acid residues that are, in the fibrillar state, part of β-strands. Importantly, this pattern of pairwise interactions does not correspond to that found in the amyloid state. A redistribution of this network of fibril-like contacts must precede aggregation into the amyloid structure. 相似文献
27.
Fluorescence microscopy is a method commonly used to examine individual differences between bacterial cells, yet many studies still lack a quantitative analysis of fluorescence microscopy data. Here we introduce some simple tools that microbiologists can use to analyze and compare their microscopy images. We show how image data can be converted to distribution data. These data can be subjected to a cluster analysis that makes it possible to objectively compare microscopy images. The distribution data can further be analyzed using distribution fitting. We illustrate our methods by scrutinizing two independently acquired data sets, each containing microscopy images of a doubly labeled Bacillus subtilis strain. For the first data set, we examined the expression of srfA and tapA, two genes which are expressed in surfactin-producing and matrix-producing cells, respectively. For the second data set, we examined the expression of eps and tapA; these genes are expressed in matrix-producing cells. We show that srfA is expressed by all cells in the population, a finding which contrasts with a previously reported bimodal distribution of srfA expression. In addition, we show that eps and tapA do not always have the same expression profiles, despite being expressed in the same cell type: both operons are expressed in cell chains, while single cells mainly express eps. These findings exemplify that the quantification and comparison of microscopy data can yield insights that otherwise would go unnoticed. 相似文献
28.
29.
Juan P. Ferrio José Luis Araus Ramon Buxó Jordi Voltas Jordi Bort 《Vegetation History and Archaeobotany》2005,14(4):510-517
Carbon isotope discrimination (Δ13C) in charred grains from archaeological sites provides reliable information about water availability of ancient crops. However,
as cereals are cultivated plants, they may reflect not only climatic fluctuations, but also the effect on water status of
certain agronomic practices, such as sowing in naturally wet soils or irrigation. In this work, we propose a methodological
approach to combine Δ13C data from different plant species, in order to discriminate between climate-derived and anthropogenic effects on ancient
crops. We updated previous models for estimating water inputs from Δ13C of cereal grains of Hordeum vulgare and Triticum aestivum/durum, and we applied them to published data from several archaeological sites, including samples from the Neolithic to the present
day in northeast and southeast Spain, as well as from the Neolithic site of Tell Halula (northwest Syria). We found an important
decrease in water availability from the Neolithic to the present time in the three areas of study, especially clear for the
two driest areas (southeast Spain and northwest Syria). Potential differences in water management practices between wheat
and barley, as well as between cereal and legume crops (Vicia faba and Lens culinaris), are also discussed on the basis of the comparison of Δ13C values across several archaeological sites. 相似文献