全文获取类型
收费全文 | 448篇 |
免费 | 47篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 15篇 |
2013年 | 20篇 |
2012年 | 37篇 |
2011年 | 30篇 |
2010年 | 15篇 |
2009年 | 15篇 |
2008年 | 19篇 |
2007年 | 23篇 |
2006年 | 24篇 |
2005年 | 23篇 |
2004年 | 14篇 |
2003年 | 12篇 |
2002年 | 26篇 |
2001年 | 21篇 |
2000年 | 13篇 |
1999年 | 15篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 2篇 |
1992年 | 13篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1981年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 1篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有495条查询结果,搜索用时 31 毫秒
71.
Patrick McDonnell Glen Smith Sanjay Joshi Soundar R.T. Kumara 《Flexible Services and Manufacturing Journal》1999,11(1):37-62
A new contract net-style auction protocol is proposed as a framework for integrating process planning and shop floor control in heterarchical manufacturing systems. Process planning is partitioned into on-line and off-line activities; off-line process planning decisions are represented in a graph format and used as input for on-line process planning activities performed by machine controllers. Triggered by the opening round of an auction, the final on-line stages of process planning are dovetailed with the resource allocation process in the shop floor control system. The auction process allows final process planning decisions to be based on timely information, relying on the distribution of static process planning information rather than the distribution of a model of dynamic shop floor status and allowing a controller to identify all the primary and secondary resources and operations that must be provided for the incremental processing of a part. 相似文献
72.
D J Schaid S K McDonnell M L Blute S N Thibodeau 《American journal of human genetics》1998,62(6):1425-1438
A family-history cancer survey was conducted on 5,486 men who underwent a radical prostatectomy, for clinically localized prostate cancer, in the Department of Urology at the Mayo Clinic during 1966-95; 4,288 men responded to the survey. Complex segregation analysis was performed to assess the genetic basis of age at diagnosis and the familial clustering of prostate cancer. For the total group, no single-gene model of inheritance clearly explained familial clustering of disease, which could be partly explained by lack of Hardy-Weinberg equilibrium, with an excess of homozygotes. After accounting for deviations from Hardy-Weinberg equilibrium, the best-fitting model that explained the familial aggregation and age at diagnosis was a rare autosomal dominant susceptibility gene, and this model fitted best when probands were diagnosed at <60 years of age. The model predicts that the frequency of the susceptibility gene in the population is .006 and that the risk of prostate cancer by age 85 years is 89% among carriers of the gene and 3% among noncarriers. A strength of our study is its large size, such that genetic models could be fitted within strata defined by the age of the proband. Although the autosomal dominant model was consistently the best model, the parameter estimates differed somewhat (P=.03) across the different age groups, suggesting genetic heterogeneity. Additional evidence that the hereditary basis of prostate cancer is likely to be genetically complex was provided by the following: (1) there was a significantly elevated age-adjusted risk of prostate cancer among brothers of probands, compared with their fathers (relative risk 1.5 [95% confidence interval 1.4-1.7]); (2) the autosomal dominant model predicted an excess of homozygotes, over that predicted by Hardy-Weinberg equilibrium; and (3) the model-predicted risk of prostate cancer among relatives was inadequate when probands were diagnosed at age >=70 years. 相似文献
73.
74.
Functional trait changes in the floras of 11 cities across the globe in response to urbanization
下载免费PDF全文
![点击此处可从《Ecography》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Estibaliz Palma Jane A. Catford Richard T. Corlett Richard P. Duncan Amy K. Hahs Michael A. McCarthy Mark J. McDonnell Ken Thompson Nicholas S. G. Williams Peter A. Vesk 《Ecography》2017,40(7):875-886
Urbanization causes major environmental changes globally, which can potentially homogenize biota across cities through the loss and gain of particular types of species. We examine whether urban environments consistently select for plants with particular traits and the implications of such changes on the functional composition of urban floras. We classified plant recorded in 11 cities around the globe as species that have either colonized (arrived and naturalized), persisted or been lost (local extirpation) following urbanization. We analyzed how 10 traits previously linked with plant responses to environmental conditions explained membership of these three groups, by comparing colonisers with persistent and extirpated plants through individual city‐level Bayesian models. Then, we used meta‐analysis to assess consistency of traits across urban areas. Finally, we explored several possible scenarios of functional change using these results. On average, urban colonizers had heavier seeds, unspecialised nutrient requirements, were taller and were annual species more often, especially when compared to locally extirpated plants. Common trends of functional change in urban plant communities include shifts towards taller and heavier‐seeded plants, and an increased prevalence of the short‐lived species, and plants without mutualistic nutritional strategies. Our results suggest that plant traits influence the species that succeed in urban environments worldwide. Different species use different ecological strategies to live in urban environments, as suggested by the importance of several traits that may appear as trait constellations. Plant height and seed mass were the only traits associated with both colonizer and extirpated plant status in urban environments. Based on our data, predicting colonization in urban environments may be easier than identifying extirpation‐prone plants; albeit some regional variation, colonization seems strongly driven by environmental conditions common to most cities (e.g. altered disturbance regimes), whereas extirpation may depend more on processes that vary across cities. 相似文献
75.
76.
Dingcheng Gao Daniel Nolan Kevin McDonnell Linda Vahdat Robert Benezra Nasser Altorki Vivek Mittal 《生物化学与生物物理学报:癌评论》2009
Emerging evidence indicates that bone marrow (BM)-derived endothelial progenitor cells (EPCs) contribute to angiogenesis-mediated growth of certain tumors in mice and human. EPCs regulate the angiogenic switch via paracrine secretion of proangiogenic growth factors and by direct luminal incorporation into sprouting nascent vessels. While the contributions of EPCs to neovessel formation in spontaneous and transplanted tumors and to the metastatic transition have been reported to be relatively low, remarkably, specific EPC ablation in vivo has resulted in severe angiogenesis inhibition and impaired primary and metastatic tumor growth. The existence of a BM reservoir of EPCs, and the selective involvement of EPCs in neovascularization, have attracted considerable interest because these cells represent novel target for therapeutic intervention. In addition, EPCs are also being used as pharmacodynamic surrogate markers for monitoring cancer progression, as well as for optimizing efficacy of anti-angiogenic therapies in the clinic. This review will focus primarily on recent advances and emerging concepts in the field of EPC biology and discuss ongoing debates involving the role of EPCs in tumor neovascularization. For detailed information on the in vitro characterization of EPCs contribution to non-tumor pathologies, the reader is directed towards several excellent reviews and publications [F. Bertolini, Y. Shaked, P. Mancuso and R.S. Kerbel, Nat. Rev., Cancer 6 (2006) 835–845. [1]] [J.M. Hill, T. Finkel and A.A. Quyyumi, Vox Sang. 87 Suppl 2 (2004) 31–37. [2]] [A.Y. Khakoo and T. Finkel, Annu. Rev. Med. 56 (2005) 79–101. [3]] [H.G. Kopp, C.A. Ramos and S. Rafii, Curr. Opin. Hematol. 13 (2006) 175–181. [4]; K.K. Hirschi, D.A. Ingram and M.C. Yoder, Arterioscler. Thromb. Vasc. Biol. 28 (2008) 1584–1595. [5]; F. Timmermans, J. Plum, M.C. Yoder, D.A. Ingram, B. Vandekerckhove and J. Case, J. Cell. Mol. Med. 13 (2009) 87–102. [6]] and reviews by Bertolini, Voest and Yoder in this issue. 相似文献
77.
78.
Due to the ban on meat and bone meal (MBM) as an animal feed, combustion with energy recovery has been considered a viable alternative usage for the mounting stocks of MBM. The effects of the co-combustion of MBM and peat on flue gas emissions and fluidisation were studied using a bubbling fluidised bed (BFB) test facility (20 kW). The dispersion of emissions such as nitrogen dioxide (NO2), sulphur dioxide (SO2), carbon monoxide (CO), hydrogen chloride (HCl) and particulates was investigated for a proposed site and compared to the relevant national and international regulations. Concentrations of NO2, CO and HCl were less than 10% of legislative and guideline thresholds while ground level concentrations of SO2 were also below relevant EU and world guidelines. The results indicate the potential for using MBM as a co-fuel with peat in a BFB while maintaining high air quality standards. 相似文献
79.
Alaux C Folschweiller M McDonnell C Beslay D Cousin M Dussaubat C Brunet JL Le Conte Y 《Journal of invertebrate pathology》2011,106(3):380-385
Nosema ceranae, a microsporidian parasite originally described in the Asian honey bee Apis cerana, has recently been found to be cross-infective and to also parasitize the European honey bee Apis mellifera. Since this discovery, many studies have attempted to characterize the impact of this parasite in A. mellifera honey bees. Nosema species can infect all colony members, workers, drones and queens, but the pathological effects of this microsporidium has been mainly investigated in workers, despite the prime importance of the queen, who monopolizes the reproduction and regulates the cohesion of the society via pheromones. We therefore analyzed the impact of N. ceranae on queen physiology. We found that infection by N. ceranae did not affect the fat body content (an indicator of energy stores) but did alter the vitellogenin titer (an indicator of fertility and longevity), the total antioxidant capacity and the queen mandibular pheromones, which surprisingly were all significantly increased in Nosema-infected queens. Thus, such physiological changes may impact queen health, leading to changes in pheromone production, that could explain Nosema-induced supersedure (queen replacement). 相似文献
80.
Howarth J Kenny P McDonnell S O'Connor A 《Bioorganic & medicinal chemistry letters》2003,13(16):2693-2697
In the course of our investigation into the use of taxol as a lead compound to design new molecules with anti-cancer activity, we have synthesized four compounds based on protected guanosine coupled to taxol isoserine side-chain analogues. These analogues show in vitro anti-cancer activity against the colon cancer cell line SW480 that their constituent parts do not. 相似文献