全文获取类型
收费全文 | 202篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
系统科学 | 6篇 |
理论与方法论 | 2篇 |
现状及发展 | 67篇 |
研究方法 | 46篇 |
综合类 | 78篇 |
自然研究 | 6篇 |
出版年
2021年 | 2篇 |
2019年 | 1篇 |
2018年 | 9篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 5篇 |
2012年 | 21篇 |
2011年 | 24篇 |
2010年 | 10篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 11篇 |
2006年 | 21篇 |
2005年 | 13篇 |
2004年 | 16篇 |
2003年 | 8篇 |
2002年 | 13篇 |
2001年 | 1篇 |
1997年 | 1篇 |
1981年 | 1篇 |
1979年 | 4篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1961年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有205条查询结果,搜索用时 2 毫秒
201.
The term ‘Sustainable Development’ is brandished by modern businesses as a marketing ploy used to suggest evidence of ethical conduct, innovative thinking and moral superiority. However, when analysing an organisations’ adoption of sustainable practices, it is often clear—within the UK—that there are few activities that have been undertaken as an ethical stance instead of legal obligation (McCormick in Environmental politics and policy in industrialized countries, MIT, London, 2002). Our hypothesis is that most methodologies and practices for environmental management do not adopt a holistic perspective, causing significant problems in implementation from inadequate structures and communication channels (Espinosa et al. in Eur J Oper Res, 187:636–651, 2008). In particular we consider that most organisations are currently stifled with management hierarchies that prevent informal/social networking, which may be one of the most powerful natural forms for self-organisation. It is proposed that sustainable development requires more efficient communication channels that foster self-organisation and self-regulation as a method for more productive change processes. In this paper, we explain the reasons why meta-systemic principles of self-organisation and distributed network management offer clear criteria to design an environmental management system that operates on the basis of self-controlled individuals and communities. 相似文献
202.
Puente XS Pinyol M Quesada V Conde L Ordóñez GR Villamor N Escaramis G Jares P Beà S González-Díaz M Bassaganyas L Baumann T Juan M López-Guerra M Colomer D Tubío JM López C Navarro A Tornador C Aymerich M Rozman M Hernández JM Puente DA Freije JM Velasco G Gutiérrez-Fernández A Costa D Carrió A Guijarro S Enjuanes A Hernández L Yagüe J Nicolás P Romeo-Casabona CM Himmelbauer H Castillo E Dohm JC de Sanjosé S Piris MA de Alava E San Miguel J Royo R Gelpí JL Torrents D Orozco M Pisano DG 《Nature》2011,475(7354):101-105
Chronic lymphocytic leukaemia (CLL), the most frequent leukaemia in adults in Western countries, is a heterogeneous disease with variable clinical presentation and evolution. Two major molecular subtypes can be distinguished, characterized respectively by a high or low number of somatic hypermutations in the variable region of immunoglobulin genes. The molecular changes leading to the pathogenesis of the disease are still poorly understood. Here we performed whole-genome sequencing of four cases of CLL and identified 46 somatic mutations that potentially affect gene function. Further analysis of these mutations in 363 patients with CLL identified four genes that are recurrently mutated: notch 1 (NOTCH1), exportin 1 (XPO1), myeloid differentiation primary response gene 88 (MYD88) and kelch-like 6 (KLHL6). Mutations in MYD88 and KLHL6 are predominant in cases of CLL with mutated immunoglobulin genes, whereas NOTCH1 and XPO1 mutations are mainly detected in patients with unmutated immunoglobulins. The patterns of somatic mutation, supported by functional and clinical analyses, strongly indicate that the recurrent NOTCH1, MYD88 and XPO1 mutations are oncogenic changes that contribute to the clinical evolution of the disease. To our knowledge, this is the first comprehensive analysis of CLL combining whole-genome sequencing with clinical characteristics and clinical outcomes. It highlights the usefulness of this approach for the identification of clinically relevant mutations in cancer. 相似文献
203.
Huang AL Chen X Hoon MA Chandrashekar J Guo W Tränkner D Ryba NJ Zuker CS 《Nature》2006,442(7105):934-938
Mammals taste many compounds yet use a sensory palette consisting of only five basic taste modalities: sweet, bitter, sour, salty and umami (the taste of monosodium glutamate). Although this repertoire may seem modest, it provides animals with critical information about the nature and quality of food. Sour taste detection functions as an important sensory input to warn against the ingestion of acidic (for example, spoiled or unripe) food sources. We have used a combination of bioinformatics, genetic and functional studies to identify PKD2L1, a polycystic-kidney-disease-like ion channel, as a candidate mammalian sour taste sensor. In the tongue, PKD2L1 is expressed in a subset of taste receptor cells distinct from those responsible for sweet, bitter and umami taste. To examine the role of PKD2L1-expressing taste cells in vivo, we engineered mice with targeted genetic ablations of selected populations of taste receptor cells. Animals lacking PKD2L1-expressing cells are completely devoid of taste responses to sour stimuli. Notably, responses to all other tastants remained unaffected, proving that the segregation of taste qualities even extends to ionic stimuli. Our results now establish independent cellular substrates for four of the five basic taste modalities, and support a comprehensive labelled-line mode of taste coding at the periphery. Notably, PKD2L1 is also expressed in specific neurons surrounding the central canal of the spinal cord. Here we demonstrate that these PKD2L1-expressing neurons send projections to the central canal, and selectively trigger action potentials in response to decreases in extracellular pH. We propose that these cells correspond to the long-sought components of the cerebrospinal fluid chemosensory system. Taken together, our results suggest a common basis for acid sensing in disparate physiological settings. 相似文献
204.
Wang J Soisson SM Young K Shoop W Kodali S Galgoci A Painter R Parthasarathy G Tang YS Cummings R Ha S Dorso K Motyl M Jayasuriya H Ondeyka J Herath K Zhang C Hernandez L Allocco J Basilio A Tormo JR Genilloud O Vicente F Pelaez F Colwell L Lee SH Michael B Felcetto T Gill C Silver LL Hermes JD Bartizal K Barrett J Schmatz D Becker JW Cully D Singh SB 《Nature》2006,441(7091):358-361
Bacterial infection remains a serious threat to human lives because of emerging resistance to existing antibiotics. Although the scientific community has avidly pursued the discovery of new antibiotics that interact with new targets, these efforts have met with limited success since the early 1960s. Here we report the discovery of platensimycin, a previously unknown class of antibiotics produced by Streptomyces platensis. Platensimycin demonstrates strong, broad-spectrum Gram-positive antibacterial activity by selectively inhibiting cellular lipid biosynthesis. We show that this anti-bacterial effect is exerted through the selective targeting of beta-ketoacyl-(acyl-carrier-protein (ACP)) synthase I/II (FabF/B) in the synthetic pathway of fatty acids. Direct binding assays show that platensimycin interacts specifically with the acyl-enzyme intermediate of the target protein, and X-ray crystallographic studies reveal that a specific conformational change that occurs on acylation must take place before the inhibitor can bind. Treatment with platensimycin eradicates Staphylococcus aureus infection in mice. Because of its unique mode of action, platensimycin shows no cross-resistance to other key antibiotic-resistant strains tested, including methicillin-resistant S. aureus, vancomycin-intermediate S. aureus and vancomycin-resistant enterococci. Platensimycin is the most potent inhibitor reported for the FabF/B condensing enzymes, and is the only inhibitor of these targets that shows broad-spectrum activity, in vivo efficacy and no observed toxicity. 相似文献
205.
Kumar KA Sano G Boscardin S Nussenzweig RS Nussenzweig MC Zavala F Nussenzweig V 《Nature》2006,444(7121):937-940
Malaria infection starts when mosquitoes inject sporozoites into the skin. The parasites enter the blood stream and make their way to the liver where they develop into the exo-erythrocytic forms (EEFs). Immunization with irradiated sporozoites (IrSp) leads to robust protection against malaria infection in rodents, monkeys and humans by eliciting antibodies to circumsporozoite protein (CS) that inhibit sporozoite infectivity, and T cells that destroy the EEFs. To study the role of non-CS antigens in protection, we produced CS transgenic mice that were tolerant to CS T-cell epitopes. Here we show that in the absence of T-cell-dependent immune responses to CS, protection induced by immunization with two doses of IrSp was greatly reduced. Thus, although hundreds of other Plasmodium genes are expressed in sporozoites and EEFs, CS is a dominant protective antigen. Nevertheless, sterile immunity could be obtained by immunization of CS transgenics with three doses of IrSp. 相似文献