全文获取类型
收费全文 | 10145篇 |
免费 | 114篇 |
国内免费 | 20篇 |
专业分类
教育 | 6811篇 |
科学研究 | 1239篇 |
各国文化 | 57篇 |
体育 | 993篇 |
综合类 | 4篇 |
文化理论 | 78篇 |
信息传播 | 1097篇 |
出版年
2022年 | 83篇 |
2021年 | 138篇 |
2020年 | 171篇 |
2019年 | 240篇 |
2018年 | 386篇 |
2017年 | 351篇 |
2016年 | 352篇 |
2015年 | 204篇 |
2014年 | 327篇 |
2013年 | 1576篇 |
2012年 | 286篇 |
2011年 | 307篇 |
2010年 | 281篇 |
2009年 | 243篇 |
2008年 | 282篇 |
2007年 | 244篇 |
2006年 | 231篇 |
2005年 | 206篇 |
2004年 | 217篇 |
2003年 | 157篇 |
2002年 | 168篇 |
2001年 | 225篇 |
2000年 | 220篇 |
1999年 | 201篇 |
1998年 | 114篇 |
1997年 | 143篇 |
1996年 | 116篇 |
1995年 | 82篇 |
1994年 | 106篇 |
1993年 | 78篇 |
1992年 | 175篇 |
1991年 | 131篇 |
1990年 | 128篇 |
1989年 | 149篇 |
1988年 | 134篇 |
1987年 | 106篇 |
1986年 | 117篇 |
1985年 | 113篇 |
1984年 | 87篇 |
1983年 | 96篇 |
1982年 | 64篇 |
1981年 | 76篇 |
1980年 | 65篇 |
1979年 | 111篇 |
1978年 | 70篇 |
1977年 | 68篇 |
1976年 | 56篇 |
1975年 | 61篇 |
1974年 | 66篇 |
1973年 | 58篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Oliver K. Burmeister 《Ethics and Information Technology》2016,18(3):185-198
Developing technology that accounts for values has been achieved in many areas, including security, gaming, finance, engineering, and many more. The main methodological approach has been that of value sensitive design. But most of the work to date has been on the first of its three stages. The focus of this article is on advances related to its second stage, empirical investigation, and in particular the impact of contextual understanding in that stage. Although lessons can be learnt from other domains, the specific context of dementia means that there are nuances to understanding values, including justice and autonomy, that differ from other areas. The integration of value considerations in the development of assistive technology in dementia is explored in two broad categories: the traditional and ongoing need for fixed decision support, and adaptable decision support technologies. For fixed decision support the A&D Benchmark is particularly useful in design. But for adaptable technologies, that benchmark requires further development, including consideration of the values of additional stakeholders, such as the general public. 相似文献
992.
K. Poornima M. Cariappa K. Asha H. P. Kedilaya M. Nandini 《Indian journal of clinical biochemistry : IJCB》2003,18(2):197-205
An adequate antioxidant reserve which is usually present in a vegetarian diet is associated with higher life expectancy. On
the other hand habitual consumption of fish is associated with lower risk of cardiovascular diseases which is attributed to
the polyunsaturated fatty acids (PUFA) present in it. However the PUFA are readily susceptible to oxidation leading to the
formation of free radicals which is known to be involved in the causation of several diseases.
The oxidant-antioxidant status of 23 vegetarians and 22 fish eaters was studied by determining the plasma lipid peroxides
measured as malondialdehyde (MDA) and the antioxidants, viz. glutathione (GSH), ascorbic acid, ceruloplasmin and uric acid.
Results show that the ascorbic acid values were significantly higher in vegetarians. In addition, MDA correlated negatively
with ascorbic acid only in vegetarians. However, correlation of MDA with glutathione showed a significant negative correlation
only in fish eaters. There was no statistically significant difference in the MDA, GSH, ceruloplasmin and uric acid levels.
The mechanism behind these findings are not clear and needs to be explored. 相似文献
993.
994.
This paper presents the applications of the stability-equation method to the analysis and design of linear systems. Control systems with multiple inputs and outputs are considered; the absolute stability and relative stability characteristics are analyzed. Stability conditions for control systems with a transport lag or a distributive lag are presented. Finally, the stability characteristics of a system with a distributive parameter are analyzed. 相似文献
995.
The level of sialic acid in the obese polymorphonuclear leukocytes (PMNL) was found to be significantly reduced as compared to normal. Activity of sialic acid degrading enzyme, sialidase, was found to be increased in the obese state. Restoration in both sialic acid content and sialidase activity was also evidenced in the PMNL of treated obese patients. 相似文献
996.
997.
Biswajit Majumdar Susri Ray Chaudhuri Arun Ray Sandip K Bandyopadhyay 《Indian journal of clinical biochemistry : IJCB》2002,17(1):49-57
Pretreatment of an ethanolic extract of leaf ofPiper betle linn at a dose of 200mg/kg body weight, orally administered to rats for ten consecutive days, was found to possess a significant
protective action against gastric lesions induced by indomethacin. The extract pretreatment resulted in significant increase
in superoxide dismutase (SOD) and catalase (CAT) activity, increase in mucus, hexosamine and total thiol group content, but
marked reduction in oxidatively damaged protein and peroxidised lipid levels as compared to untreated ulcerated control. The
extract was also found to possess both superoxide and hydroxyl free radical scavenging action. The present observations establish
the efficacy of the extract in prevention of experimentally induced peptic ulcer by indomethacin and antioxidant property
appears to be predominantly responsible for such cytoprotective activity in the experimental model. 相似文献
998.
A method has been presented in recent papers for deriving precisely stabilized waveform generators by relating them to second-order conservative oscillators. The present paper suggests a method for considerably generalizing the previous class ofgenerator models. This should enable the development of a larger variety of waveform generators with ease and flexibility. The new method is analyzed and is shown to possess implications to theoretical biology and other fields. 相似文献
999.
This paper examines the terminological confusion underlying the study of information use, and reviews the major studies in the field. The conclusion is that confusion in research methods is inextricably linked to a lack of clarity in terminology. Attention is drawn to the significance of different social and cultural contexts in shaping ‘information needs’, and a research scheme is evolved for the study of users of ‘professional information’ in Poland. 相似文献
1000.
Farhana Zahir Shameem J Rizvi Soghra K Haq Rizwan H Khan 《Indian journal of clinical biochemistry : IJCB》2006,21(2):149-152
Mercury pollution and acute neurotoxicity of mercury is well known. The recent reports suggest the adverse effect of low dose
mercury, though the available literature is still silent on its mechanism. This study was therefore undertaken to probe the
effect of low dose methyl mercury induced heavy metal toxicity on free radical stress and its impact on behaviour of male
albino rats. Male albino rats were exposed to 1 mg/kg body wt of methylmercury chloride for seven days, on day 8 they were
tested for motor and memory functions. They were sacrificed later for biochemical estimations for rate of lipid peroxidation,
nucleic acids, proteins in cerebrum, cerebellum and brain stem. There was an increase in the rate of lipid peroxidation showing
methyl mercury induced free radical stress. The motor and memory functions demonstrated a clear decline, besides there was
a lowering in the levels of nucleic acids and proteins as compared to controls. The results are important in view of recent
reports that methyl mercury induced free radical stress results in early ageing and may serve as an initiating factor more
specifically for neurodegenerative disorders like Alzeihemer's disease and dementias. The current findings support the notion
that incorporating dietary antioxidants like curcumin, ascorbic acid and α-tocopherol in routine diet from early age may help
combat the risk of developing such disorders in ensuing years. 相似文献