全文获取类型
收费全文 | 298篇 |
免费 | 32篇 |
出版年
2023年 | 3篇 |
2020年 | 3篇 |
2019年 | 9篇 |
2018年 | 5篇 |
2017年 | 9篇 |
2016年 | 6篇 |
2015年 | 15篇 |
2014年 | 11篇 |
2013年 | 17篇 |
2012年 | 14篇 |
2011年 | 15篇 |
2010年 | 7篇 |
2009年 | 9篇 |
2008年 | 15篇 |
2007年 | 15篇 |
2006年 | 6篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 7篇 |
2002年 | 5篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 7篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1972年 | 4篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1966年 | 2篇 |
1960年 | 2篇 |
排序方式: 共有330条查询结果,搜索用时 46 毫秒
71.
Isabel M. D. Rosa Ana Teresa Marques Gustavo Palminha Hugo Costa Miguel Mascarenhas Carlos Fonseca Joana Bernardino 《Ibis》2016,158(1):28-42
Radar systems have been increasingly used to monitor birds. To take full advantage of the large datasets provided by radars, researchers have implemented machine learning (ML) techniques that automatically read and attempt to classify targets. Here we used data collected from two locations in Portugal with two marine radar antennas (VSR and HSR) to apply and compare the performance of six ML algorithms that are widely used in the literature: random forests (RF), support vector machine (SVM), artificial neural networks (NN), linear discriminant analysis (LDA), quadratic discriminant analysis (QDA) and decision trees (DT), all trained with several dataset configurations. We found that all algorithms performed well (area under the receiver operating characteristic (AUC) and accuracy > 0.80, P < 0.001) when discriminating birds from non‐biological targets such as vehicles, rain or wind turbines, but greater variance in the performance among algorithms was apparent when separating different bird functional groups or bird species (e.g. herons vs. gulls). In our case study, only RF was able to hold an accuracy > 0.80 for all classification tasks, although SVM and DT also performed well. Further, all algorithms correctly classified 86% and 66% (VSR and HSR) of the target points, and only 2% and 4% of these points were misclassified by all algorithms. Our results suggest that ML algorithms are suitable for classifying radar targets as birds, and thereby separating them from other non‐biological targets. The ability of these algorithms to correctly identify among bird species functional groups was found to be much weaker, but if properly trained and supported by a good ground truthing dataset, targeted to the relevant species groups, some of these algorithms are still able to achieve high accuracies in classification tasks. Such results indicate that ML algorithms are suitable for use in near real‐time monitoring of bird movements, and may help to mitigate collision of birds with, for example, wind turbines or airplanes. 相似文献
72.
Fernanda Sofia Quintela da Silva Brandão Marco Paulo Lages Parente Paulo Alexandre Gomes Gonçalves Rocha Maria Teresa da Quinta e Costa de Mascarenhas Saraiva Isabel Maria Amorim Pereira Ramos Renato Manuel Natal Jorge 《Computer methods in biomechanics and biomedical engineering》2016,19(4):347-356
We performed numerical simulation of voluntary contraction of the pelvic floor muscles to evaluate the resulting displacements of the organs and muscles. Structures were segmented in Magnetic Resonance (MR) images. Different material properties and constitutive models were attributed. The Finite Element Method was applied, and displacements were compared with dynamic MRI findings. Numerical simulation showed muscle magnitude displacement ranging from 0 to 7.9 mm, more evident in the posterior area. Accordingly, the anorectum moved more than the uterus and bladder. Dynamic MRI showed less 0.2 mm and 4.1 mm muscle dislocation in the anterior and cranial directions, respectively. Applications of this model include evaluating muscle impairment, subject-specific mesh implant planning, or effectiveness of rehabilitation. 相似文献
73.
MM El-Shazly El Elzayat IIA El-Sebeay YA Edmardash MM Soliman 《African Journal of Aquatic Science》2016,41(3):289-296
Manzala Lake, as one of the main Egyptian wetland ecosystems, is facing risks of pollution. An in vitro cytotoxicity test using a mammalian cell line was employed to determine the toxicity of multiple pollutants in the water and Tilapia zillii fish sampled from the lake. The concentrations of seven polychlorinated dibenzo-p-dioxins and ten polychlorinated dibenzofurans were investigated in water and muscle of the fish in 2014. Cytotoxicity testing showed that the percentage inhibition of cell viability in the studied sites ranged between 56.16% and 83.22%. Dioxin analysis indicated that the average concentrations of 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin, 1,2,3,4,7,8-hexachlorodibenzofuran, 1,2,3,4,6,7,8-heptachlorodibenzofuran and 1,2,3,4,6,7,8,9-octachlorodibenzofuran were higher than the toxic equivalence quotients (TEQs) set by the World Health Organization (WHO) in all water and fish muscle samples; however, the average concentration of 2,3,7,8-tetrachlorodibenzofuran was higher only in fish muscle samples. The bioaccumulation factor (BAF) ranged dramatically between 2 and 58.5 for the detected dioxins. Adverse human health effects through the consumption of fish are not expected, because dioxin levels in fish muscle are deemed safe for human consumption. Implementation of a strategic multidisciplinary action plan is strongly recommended to sustain this delta wetland ecosystem. 相似文献
74.
M. Kotwal Mridula P. K. Gupta A. F. Mascarenhas 《Plant Cell, Tissue and Organ Culture》1983,2(2):133-139
Multiple shoots formation and elongation was induced from stem explants of Sapium seedlings on media containing cytokinins. Leaf explants produced callus on a medium containing cytokinins, auxin, casein hydrolysate and coconut milk, which could be induced to form multiple shoots on transfer to a medium lacking casein hydrolysate, coconut milk and auxin. Rooting of isolated shoots by treatment with an auxin mixture (indole-3-acetic acid, indole-3-butyric acid and indole-3-propionic acid) and transfer of the plantlets to field have also been successful. 相似文献
75.
76.
Joseph P. Mascarenhas 《The Botanical review》1975,41(3):259-314
Recent work concerning the regulation of pollen and pollen tube development at the biochemical level in angiosperms has been reviewed, commencing with the microspore immediately after meiosis and terminating with the entry of the pollen tube into the embryo sac. Some of the topics that have been considered are, (1) the role of the tapetum in pollen development, (2) gene activity in the microspore and pollen grain prior to anthesis, (3) DNA synthesis in the microspore and pollen tube, (4) the types of RNA and protein synthesized in the pollen tube including the biochemistry of the vegetative and generative nuclei and finally, (5) the interactions between pollen and pistil after pollination. 相似文献
77.
Genes expressed in the male gametophyte of flowering plants and their isolation 总被引:21,自引:3,他引:18 下载免费PDF全文
Stinson JR Eisenberg AJ Willing RP Pe ME Hanson DD Mascarenhas JP 《Plant physiology》1987,83(2):442-447
Recombinant cDNA libraries to poly(A)RNA isolated from mature pollen of Zea mays and Tradescantia paludosa have been constructed. Northern blot analyses indicate that several of the clones are unique to pollen and are not expressed in vegetative tissues. The majority, however, are expressed both in pollen and vegetative tissues. Southern hybridizations show that the pollen specific sequences in corn are present in one or a very few copies in the genome. By using several of the clones as probes, it was found that there are at least two different groups of mRNAs with respect to their synthesis. The mRNAs of the first group represented by the pollen specific clones are synthesized after microspore mitosis and increase in concentration up to maturity. The second group, exemplified by actin mRNA, begins to accumulate soon after meiosis, reaches its maximum by late pollen interphase, and decreases thereafter. Although the actin mRNA and the pollen specific mRNAs studied show very different patterns of initiation of synthesis and accumulation during pollen development, the rates of decline of these mRNAs during the first 60 minutes of germination and pollen tube growth in Tradescantia are similar and reflect the previously observed declines in rates of protein synthesis during this period. 相似文献
78.
79.
Sans résuméI. Analyse électrocapillaire des matières colorantes. Rev. gén. Mat. Col. 1926 Vol. 30 pp 34–45II. Phénomènes électrocapillaires et le problème du cancer. Arch. Med. Exper. 1926 Vol. I p 381III. Phénomènes électrocapillaires et l'antagonismes microbiens. Bol. Istituto Sier. Milano 1927 Vol. VI p 313. 相似文献
80.
Joseph P. Mascarenhas 《Protoplasma》1966,62(1):53-58
Summary The distribution of ionic calcium in the tissues of the gynoecium ofAntirrhinum majus flowers has been studied using the glyoxal bis (2-hydroxy-anil) staining procedure.The highest concentration of ionic calcium is found in the cells of the placenta and the cells lining the inner ovary wall. The cells of the ovule are comparatively low in calcium, and there is no higher concentration of calcium in the region of the micropyle and embryo sac. The cells of the stigma contain less calcium than those of the placenta, but almost the same as the cells of the ovule. The stigmatoid tissue and surrounding parenchyma in the style contain a low amount of calcium, lower than that found in the ovule and stigma. The relevance of these data to the growth and chemotropism of pollen tubes is discussed.This study was made possible by a grant from the Brown-Hazen Fund of Research Corporation and by Grant GB 3243 from the National Science Foundation. The technical assistance of Miss Annabelle M. Birrow is gratefully acknowledged. 相似文献