全文获取类型
收费全文 | 191篇 |
免费 | 0篇 |
国内免费 | 5篇 |
专业分类
系统科学 | 5篇 |
丛书文集 | 53篇 |
理论与方法论 | 1篇 |
现状及发展 | 40篇 |
研究方法 | 3篇 |
综合类 | 94篇 |
出版年
2020年 | 1篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2013年 | 3篇 |
2012年 | 4篇 |
2011年 | 3篇 |
2009年 | 5篇 |
2007年 | 3篇 |
2006年 | 5篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1997年 | 1篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1965年 | 1篇 |
1959年 | 16篇 |
1958年 | 30篇 |
1957年 | 23篇 |
1956年 | 10篇 |
1955年 | 16篇 |
1954年 | 23篇 |
1948年 | 7篇 |
1947年 | 3篇 |
排序方式: 共有196条查询结果,搜索用时 46 毫秒
71.
在内蒙古四子王旗采用挖掘法对不同带间距柠条林地灌草根系体积的空间分布特征进行研究,结果表明:带间灌草根系体积水平分布为全部根系与直径≥0.5 mm根系分布特征相似;直径≤0.2 mm根系对全部根系分布特征的影响在近柠条带1.5 m之内,对16 m带间距林地的影响在2.0 m之后,且呈波状变化;根系体积垂直分布总体上随着土层的加深而减少,随着带间距的加大表土层根系逐渐增加;5 m带间距时遵从y=aebx函数关系,10 m、16 m带间距时遵从y=aLn(x)+b函数关系.16 m带间距林地根系水平分布相对均匀,垂直分布在0~20 cm土层比例较大,是比较适合该地区的灌草复合林地. 相似文献
72.
针对节点增加的动态网络,提出一种对应的动态网络社群结构探测算法CD(Community Structure Detection Algorithm for Dynamic Networks).CDD算法依据节点加入引起模块性指标变化的情况,对网络节点进行社群划分, 从而可以发现网络社群结构随时间的动态变化过程.利用计算机生成数据、Ucinet和Pajek提供的有关网络数据,通过社群结构探测试验表明, CDD算法不但可以对动态网络的社群结构变化进行探测,同样也可以实现静态网络的社群结构探测; 与N-G算法和A-N算法等社群结构探测算法相比, 算法的速度快, 所获得的模块性指标也基本相当. 相似文献
73.
将激光反射仪应用于溶液吸附上,考察了聚氧乙烯十二烷基醚--一种非离子表面活性剂溶液在硅片表面上的吸附解吸过程,结果表明其吸附过程极快,30s 达到稳定值,且解吸完全.其最大吸附量Г(mg·m-2)是2.45 mg·m-2.在临界表面相关浓度CSAC(0.045 5 mmol·L-1)以下的浓度范围内,吸附模型符合Langmuir模型. 相似文献
74.
Hsieh AC Liu Y Edlind MP Ingolia NT Janes MR Sher A Shi EY Stumpf CR Christensen C Bonham MJ Wang S Ren P Martin M Jessen K Feldman ME Weissman JS Shokat KM Rommel C Ruggero D 《Nature》2012,485(7396):55-61
The mammalian target of rapamycin (mTOR) kinase is a master regulator of protein synthesis that couples nutrient sensing to cell growth and cancer. However, the downstream translationally regulated nodes of gene expression that may direct cancer development are poorly characterized. Using ribosome profiling, we uncover specialized translation of the prostate cancer genome by oncogenic mTOR signalling, revealing a remarkably specific repertoire of genes involved in cell proliferation, metabolism and invasion. We extend these findings by functionally characterizing a class of translationally controlled pro-invasion messenger RNAs that we show direct prostate cancer invasion and metastasis downstream of oncogenic mTOR signalling. Furthermore, we develop a clinically relevant ATP site inhibitor of mTOR, INK128, which reprograms this gene expression signature with therapeutic benefit for prostate cancer metastasis, for which there is presently no cure. Together, these findings extend our understanding of how the 'cancerous' translation machinery steers specific cancer cell behaviours, including metastasis, and may be therapeutically targeted. 相似文献
75.
76.
Coproduction in Practice: Participatory Action Research to Develop a Model of Community Aged Care 总被引:2,自引:2,他引:0
Goetz Ottmann Carmel Laragy Jacqui Allen Peter Feldman 《Systemic Practice and Action Research》2011,24(5):413-427
Coproduction has become synonymous with innovative approaches to public service delivery in European Union countries as well
as in Australia. Coproduction has the potential to bring together individuals, communities, and organisations in a process
to collaboratively develop new models and services which improve public services. Yet, Australian policy makers and practitioners
who would like to deploy coproduction within the context of older adult social care can only draw on a handful of papers and
reports that could guide implementation. This paper fills this gap by reporting on the implementation of a multi-stakeholder
coproduction approach to the development of a consumer directed care model for older people with complex health issues. The
paper describes and critically highlights methodological challenges encountered during the 12 month-long participatory action
research phase of a larger project involving older people with complex care needs, their carers, and government and non-government
stakeholders. The paper outlines key considerations regarding (1) the involvement of older people with complex needs, (2)
collaboration with industry partners, (3) engagement of government representatives, and (4) reflects on implementing participatory
research projects within a context of outsourcing and interlinked supply chains. While not all challenges encountered could
be resolved, the coproduction approach was successful in bringing together a wide range of stakeholders with competing agendas
in an iterative process geared to resolve a plethora of concerns raised by older people, carers and services providers. This
paper provides an example for others seeking to use coproduction and participatory methods to provide person-centred care
services for older people. 相似文献
77.
对事故多发点进行改造是减少事故的发生、增强交通安全的重要措施,其中增加标志标线等交通安全设施是常见的改造方式。由于驾驶行为是影响交通安全的重要因素,因此有必要从驾驶员角度对改造效进行评价。本文研究了某二级公路的事故多发点特点,在现场实验的基础上结合驾驶员眼动注视点的特征分析,分别从驾驶员注视特征、运营速度、改造前后的事故分析,综合评价事故多发点的改造效果,同时分析驾驶员负荷特征,为未来事故多发点的安全改造方案提出可行建议。 相似文献
78.
新集二矿针对W1607俯斜沿空综采工作面瓦斯涌出的特点,分析了工作面上隅角的瓦斯来源,对综采工作面设施了合理配风、均压通风、本煤层瓦斯抽放、顶板走向钻孔抽放及顶板高抽巷抽放瓦斯的综合治理及防火措施,确保了高产高效俯斜沿空综采工作面的安全生产。 相似文献
79.
Baker M Mackenzie IR Pickering-Brown SM Gass J Rademakers R Lindholm C Snowden J Adamson J Sadovnick AD Rollinson S Cannon A Dwosh E Neary D Melquist S Richardson A Dickson D Berger Z Eriksen J Robinson T Zehr C Dickey CA Crook R McGowan E Mann D Boeve B Feldman H Hutton M 《Nature》2006,442(7105):916-919
Frontotemporal dementia (FTD) is the second most common cause of dementia in people under the age of 65 years. A large proportion of FTD patients (35-50%) have a family history of dementia, consistent with a strong genetic component to the disease. In 1998, mutations in the gene encoding the microtubule-associated protein tau (MAPT) were shown to cause familial FTD with parkinsonism linked to chromosome 17q21 (FTDP-17). The neuropathology of patients with defined MAPT mutations is characterized by cytoplasmic neurofibrillary inclusions composed of hyperphosphorylated tau. However, in multiple FTD families with significant evidence for linkage to the same region on chromosome 17q21 (D17S1787-D17S806), mutations in MAPT have not been found and the patients consistently lack tau-immunoreactive inclusion pathology. In contrast, these patients have ubiquitin (ub)-immunoreactive neuronal cytoplasmic inclusions and characteristic lentiform ub-immunoreactive neuronal intranuclear inclusions. Here we demonstrate that in these families, FTD is caused by mutations in progranulin (PGRN) that are likely to create null alleles. PGRN is located 1.7 Mb centromeric of MAPT on chromosome 17q21.31 and encodes a 68.5-kDa secreted growth factor involved in the regulation of multiple processes including development, wound repair and inflammation. PGRN has also been strongly linked to tumorigenesis. Moreover, PGRN expression is increased in activated microglia in many neurodegenerative diseases including Creutzfeldt-Jakob disease, motor neuron disease and Alzheimer's disease. Our results identify mutations in PGRN as a cause of neurodegenerative disease and indicate the importance of PGRN function for neuronal survival. 相似文献
80.