全文获取类型
收费全文 | 14341篇 |
免费 | 182篇 |
国内免费 | 22篇 |
专业分类
教育 | 10053篇 |
科学研究 | 1584篇 |
各国文化 | 134篇 |
体育 | 1200篇 |
综合类 | 7篇 |
文化理论 | 105篇 |
信息传播 | 1462篇 |
出版年
2021年 | 141篇 |
2020年 | 198篇 |
2019年 | 275篇 |
2018年 | 379篇 |
2017年 | 361篇 |
2016年 | 369篇 |
2015年 | 245篇 |
2014年 | 329篇 |
2013年 | 2527篇 |
2012年 | 313篇 |
2011年 | 334篇 |
2010年 | 301篇 |
2009年 | 235篇 |
2008年 | 289篇 |
2007年 | 264篇 |
2006年 | 241篇 |
2005年 | 218篇 |
2004年 | 240篇 |
2003年 | 217篇 |
2002年 | 194篇 |
2001年 | 461篇 |
2000年 | 303篇 |
1999年 | 264篇 |
1998年 | 129篇 |
1997年 | 168篇 |
1996年 | 155篇 |
1995年 | 137篇 |
1994年 | 159篇 |
1993年 | 132篇 |
1992年 | 193篇 |
1991年 | 209篇 |
1990年 | 203篇 |
1989年 | 216篇 |
1988年 | 174篇 |
1987年 | 171篇 |
1986年 | 172篇 |
1985年 | 215篇 |
1984年 | 169篇 |
1983年 | 161篇 |
1982年 | 144篇 |
1981年 | 130篇 |
1980年 | 126篇 |
1979年 | 176篇 |
1978年 | 143篇 |
1977年 | 127篇 |
1976年 | 101篇 |
1975年 | 119篇 |
1974年 | 112篇 |
1973年 | 120篇 |
1971年 | 108篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
891.
The comparative kilogram-price of an equivalent product group in international trade is a rough indication of underlying technological capability. Although there are many theoretical and practical difficulties involved in applying this approach to East-West trade, these difficulties can be minimised by a careful selection of product groups. In this connection, advanced chemical products are particularly suitable because the chemical industry is one in which both kilogram-prices and technological sophistication tend to increase hand-in-hand at successive stages of manufacture. The results of this enquiry are quite striking. From the standpoint of bilateral trade, the kilogram-prices of Soviet and East European exports to the EEC countries are consistently lower than those of corresponding imports from the EEC. Throughout the period 1960–1972 these differentials appears to be closing either very slowly or not at all, while the Soviet and East European share of the EEC marked has remained more or less constant or has declined since the mid-1960's. From the alternative perspective of the “neutral” Yugoslavian market, the kilogram-prices of EEC exports are again consistently higher than those obtained by the Comecon coun tries. Moreover, there has been a considerable eroson in the market share of the Comecon countries since the mid-1960's. These general findings are broadly in line with other kinds of estimates and suggest that in these relatively advanced and dynamic sectors of industry, Soviet and East European technology is at present substantially inferior to that of the Common Market countries. 相似文献
892.
Using population census data since 1921, this article traces changes in employment and occupational structure in Singapore in the past 80 years. This is a follow-up to an earlier paper by Kuo and Chen (1987) that reported the nascent formation of the information society in Singapore till the 1980s. It also makes an assessment of the role of proactive government policies in directing industrial restructuring and occupational changes in this city-state. It is found that the long-term growing trend in information-related occupations has been in tandem and supportive of industrial changes in Singapore. One more wave of growth of information producers (and certainly, innovators) and information distributors is expected in the next couple of decades. The momentum has started, and competition from regional countries similarly aspiring to be information and knowledge economies will quicken the pace. The government has initiated fundamental changes in the educational system to meet the challenges of the knowledge-based economy. The small city-state has also long adopted an adaptive philosophy to be responsive to the ever-changing environment, either in technology or in regional politics. Based on the trend analysis, it is expected that the emergent information society will graduate into full status when Singapore attains a developed country status in the forthcoming decades. 相似文献
893.
894.
J.C. Dunn 《Journal of The Franklin Institute》1973,295(2):117-133
If T maps a convex domain DT into itself, and if {ωn} is a real sequence with range in (0, 1] then the recursive averaging process, generates a sequence {x?n}; with range in DT. Under suitable conditions on DT, T and {ωn} the sequence {x?n} will converge in some sense to a fixed point of T. We prove that if DT is a closed convex subset of a complex Hilbert space H, if Tω = (1 ? ω) I + ωT is a strict contraction for some ω ? (0, 1], and if {ωn} satisfies the conditions, and then, for arbitrary ξ ? DT, {x?n} converges strongly to (the unique) fixed point of T. We also prove that if DT and {ωn} satisfy the foregoing conditions, if T has at least one fixed point, and if Tω is non-expansive for some ω ? (0, 1], then for all ξ ? DT, {x?n} converges at least weakly to some fixed point of T. Finally, we apply these results to linear equations involving bounded normal operators and obtain an extension of the classical Neumann operator series. 相似文献
895.
多种原因造成了知识产权担保在发放信贷方面的重要性不如其他财产的担保。原因之一是知识产权具有一些特殊属性,一些潜在贷款人对这种财产属性缺乏了解。另一个原因是对许多知识产权的估价存在困难,相关法律在调整这些法定权利上的担保权益方面也不甚健全。尽管金融机构及其法律顾问已经越来越多地理解了知识产权担保借贷中的诸要素,但以知识产权担保的融资仍处在初期阶段。这是一个无论在法律领域,还是在信贷实践方面都很复杂的问题。立法者在回应专门立法需求以促进其发展方面也行动缓慢。这就进一步增加了用知识产权这种价值可能很大、但寿命又可能很短的财产做担保提供信贷的不确定性。 相似文献
896.
897.
M. V. R. Reddy R. Alli B. C. Harinath 《Indian journal of clinical biochemistry : IJCB》2000,15(1):127-135
Lymphatic filariasis caused mainly by infection fromWuchereria bancrofti andBrugia malayi remains as the major cause of clinical morbidity in tropical and subtropical countries. Development of vaccine against filarial infection can act as additional measure to the existing therapeutic and vector control methods in the control of this disease. The main hurdles in the development of anti-filarial vaccine are the strict primate specificity ofWuchereria bancrofti, the paucity of parasite material, the diversity of clinical manifestations and their associated complex immune responses, lack of clear understanding on host-parasite interactions and the mechanisms involved in protective immunity. However in the past few years, the information generated in immuno-epidemiological studies, correlated with observations in experimental animals suggests that a filarial vaccine is feasible. Initially live irradiated infective larvae have been successfully used to induce high level of protective immunity in several animal models. Applying diverse strategies, variety of purified or recombinant filarial antigens have been explored for their ability to induce protection in different host-parasite systems. Some of these targeted filarial antigens induced high level of resistance in experimental animals against challenge infections. More focussed studies on thorough characterization of parasitological and immunological changes associated with resistance induced by such candidate protective antigens and on delivery mechanisms and safety aspects will be crucial in their selection for possible use in humans. 相似文献
898.
RobertC.Gallo LucMontagnier 《中国科技信息》2002,(24):41-42
超过7000万人感染HIV、2000万人死亡,艾滋病是医学史上最严重的流行病之一. 相似文献
899.
900.
Isis at seventy-five 总被引:1,自引:0,他引:1