全文获取类型
收费全文 | 7848篇 |
免费 | 202篇 |
国内免费 | 14篇 |
专业分类
财政金融 | 854篇 |
工业经济 | 341篇 |
计划管理 | 779篇 |
经济学 | 1084篇 |
综合类 | 65篇 |
运输经济 | 27篇 |
旅游经济 | 63篇 |
贸易经济 | 759篇 |
农业经济 | 233篇 |
经济概况 | 934篇 |
水利工程 | 2922篇 |
邮电经济 | 3篇 |
出版年
2020年 | 94篇 |
2019年 | 133篇 |
2018年 | 207篇 |
2017年 | 206篇 |
2016年 | 191篇 |
2015年 | 113篇 |
2014年 | 179篇 |
2013年 | 572篇 |
2012年 | 262篇 |
2011年 | 283篇 |
2010年 | 180篇 |
2009年 | 179篇 |
2008年 | 231篇 |
2007年 | 229篇 |
2006年 | 225篇 |
2005年 | 180篇 |
2004年 | 201篇 |
2003年 | 116篇 |
2002年 | 125篇 |
2001年 | 157篇 |
2000年 | 133篇 |
1999年 | 128篇 |
1998年 | 145篇 |
1997年 | 124篇 |
1996年 | 116篇 |
1995年 | 135篇 |
1994年 | 94篇 |
1993年 | 120篇 |
1992年 | 125篇 |
1991年 | 123篇 |
1990年 | 112篇 |
1989年 | 128篇 |
1988年 | 116篇 |
1987年 | 119篇 |
1986年 | 113篇 |
1985年 | 108篇 |
1984年 | 122篇 |
1983年 | 106篇 |
1982年 | 100篇 |
1981年 | 109篇 |
1980年 | 118篇 |
1979年 | 109篇 |
1978年 | 98篇 |
1977年 | 89篇 |
1976年 | 95篇 |
1975年 | 82篇 |
1973年 | 82篇 |
1972年 | 88篇 |
1971年 | 80篇 |
1969年 | 73篇 |
排序方式: 共有8064条查询结果,搜索用时 2 毫秒
1.
I. E. Ilina E. N. Zharova S. P. Burlankov 《Studies on Russian Economic Development》2018,29(2):207-213
This paper presents an approach to assessing the efficacy of public spending on research and development in state programs. At present, there is a need to develop a unified approach to the analysis and evaluation of the efficacy of such spending from the perspective of participants in state programs (federal executive bodies). The proposed approach does not allow evaluating the efficacy of public spending on the development of research areas assigned to the authors. 相似文献
2.
3.
4.
5.
6.
Upflow anaerobic sludge blanket (UASB) methane fermentation treatment of cow manure that was subjected to screw pressing, thermal treatment and subsequent solid-liquid separation was studied. Conducting batch scale tests at temperatures between 140 and 180 degrees C, the optimal temperature for sludge settling and the color suppression was found to be between 160-170 degrees C. UASB treatment was carried out with a supernatant obtained from the thermal treatment at the optimal conditions (170 degrees C for 30 minutes) and polymer-dosed solid-liquid separation. In the UASB treatment with a COD(Cr) loading of 11.7 kg/m3/d and water temperature of 32.2 degrees C, the COD(Cr) level dropped from 16,360 mg/L in raw water to 3,940 mg/L in treated water (COD(Cr), removal rate of 75.9%), and the methane production rate per COD(Cr) was 0.187 Nm3/kg. Using wastewater thermal-treated at the optimal conditions, also a methane fermentation treatment with a continuously stirred tank reactor (CSTR) was conducted (COD(Cr) in raw water: 38,000 mg/L, hydraulic retention time (HRT): 20 days, 35 degrees C). At the COD(Cr) loading of 1.9 kg/m3/d, the methane production rate per COD(Cr), was 0.153 Nm3/kg. This result shows that UASB treatment using thermal pre-treatment provides a COD(Cr), loading of four times or more and a methane production rate of 1.3 times higher than the CSTR treatment. 相似文献
7.
V. N. Durcheva S. M. Puchkova 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2006,40(2):71-78
Operation of the dam in a transitional mode is described.
__________
Translated from Gidrotekhnicheskoe Stroitel’stvo, No. 1, January 2006, pp. 8–15. 相似文献
8.
This paper investigates India's exceptional development pattern, specifically the major importance of information technology services (ITS), and compares it with China's development pattern. Both countries want to develop capabilities for carrying out the innovation of technologies that compete at the state-of-the-art in the world market. The paper posits that technological/economic success in the contemporary world market requires the ability to innovate complex technologies and complex technology-related services. The share of trade represented by complex technologies is compared with the “high-tech” share. The trading patterns of the two countries are compared using United Nations data. Two case studies of Indian ITS companies are then compared with two case studies of Chinese manufacturing companies. Historical and cultural differences appear to explain some of the differences in the development patterns of the companies located in the two countries. 相似文献
9.
10.
The biochemical composition can be seen as a good indicator of both the biodegradability and the methane potential of a given waste. The work presented here is an attempt to elaborate a typology of wastes and to compare it to the anaerobic degradation characteristics. The first data indicate that there is a link between the ligno-cellulosic content of the waste and the biodegradability. When dealing with application to anaerobic digestion processes, having a tool to predict the ability of the waste to be degraded could be of the greatest interest for preventing failures, estimating biogas production, methane content, or for the management of co-digestion processes. 相似文献