全文获取类型
收费全文 | 233337篇 |
免费 | 1424篇 |
国内免费 | 246篇 |
专业分类
电工技术 | 3938篇 |
综合类 | 206篇 |
化学工业 | 34665篇 |
金属工艺 | 15541篇 |
机械仪表 | 10148篇 |
建筑科学 | 4257篇 |
矿业工程 | 2506篇 |
能源动力 | 3319篇 |
轻工业 | 9983篇 |
水利工程 | 3688篇 |
石油天然气 | 9635篇 |
武器工业 | 12篇 |
无线电 | 20493篇 |
一般工业技术 | 55214篇 |
冶金工业 | 32762篇 |
原子能技术 | 7741篇 |
自动化技术 | 20899篇 |
出版年
2018年 | 10363篇 |
2017年 | 10910篇 |
2016年 | 7649篇 |
2015年 | 2147篇 |
2014年 | 3037篇 |
2013年 | 6386篇 |
2012年 | 6582篇 |
2011年 | 12639篇 |
2010年 | 11525篇 |
2009年 | 10762篇 |
2008年 | 10815篇 |
2007年 | 12553篇 |
2006年 | 4199篇 |
2005年 | 6793篇 |
2004年 | 5433篇 |
2003年 | 5066篇 |
2002年 | 4070篇 |
2001年 | 3524篇 |
2000年 | 3502篇 |
1999年 | 3234篇 |
1998年 | 7023篇 |
1997年 | 5150篇 |
1996年 | 3834篇 |
1995年 | 2927篇 |
1994年 | 2624篇 |
1993年 | 2744篇 |
1992年 | 2271篇 |
1991年 | 2327篇 |
1990年 | 2409篇 |
1989年 | 2315篇 |
1988年 | 2320篇 |
1987年 | 2190篇 |
1986年 | 2246篇 |
1985年 | 2292篇 |
1984年 | 2206篇 |
1983年 | 2135篇 |
1982年 | 1980篇 |
1981年 | 2193篇 |
1980年 | 2053篇 |
1979年 | 2269篇 |
1978年 | 2431篇 |
1977年 | 2430篇 |
1976年 | 3095篇 |
1975年 | 2244篇 |
1974年 | 2307篇 |
1973年 | 2342篇 |
1972年 | 2155篇 |
1971年 | 1911篇 |
1970年 | 1701篇 |
1969年 | 1687篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
Yachao Dong Christos T. Maravelias Norman F. Jerome 《Optimization and Engineering》2018,19(4):937-976
We study a maritime inventory routing problem, in which shipments between production and consumption nodes are carried out by a fleet of vessels. The vessels have specific capacities and can be chartered under different agreements. The inventory levels of all consumption nodes and some production nodes should be maintained within specified bounds; for the remaining production nodes, orders should be picked up within pre-defined time windows. We propose a discrete-time mixed-integer programming model. In the face of new information and uncertainty, this optimization model has to be re-solved, as the horizon is rolled forward. We discuss how to account for different sources of uncertainty. We present a rolling-horizon reoptimization framework that allows us to study different policies that impact the quality of the implemented solution, so we can identify the optimal set of policies. 相似文献
93.
94.
95.
96.
Technical Physics Letters - Possible designs of a terahertz laser that use the effect of Bloch oscillations in SiC natural superlattices have been considered. It has been proposed to use as a... 相似文献
97.
J Comas I Rodríguez-Roda M Poch K V Gernaey C Rosen U Jeppsson 《Water science and technology》2006,53(4-5):303-311
Wastewater treatment plant operators encounter complex operational problems related to the activated sludge process and usually respond to these by applying their own intuition and by taking advantage of what they have learnt from past experiences of similar problems. However, previous process experiences are not easy to integrate in numerical control, and new tools must be developed to enable re-use of plant operating experience. The aim of this paper is to investigate the usefulness of a case-based reasoning (CBR) approach to apply learning and re-use of knowledge gained during past incidents to confront actual complex problems through the IWA/COST Benchmark protocol. A case study shows that the proposed CBR system achieves a significant improvement of the benchmark plant performance when facing a high-flow event disturbance. 相似文献
98.
Y S Cao C M Ang K S Raajeevan A K Kiran K C Lai S W Ng I Zulkifli Y L Wah 《Water science and technology》2006,54(8):237-246
This paper analyses the performance of the anaerobic selector (A/O process) in a full-scale activated sludge process receiving mostly industrial sewage discharge (> 60%) in Singapore. In addition to the sludge settleability, enhanced biological phosphorus removal (EBPR) was studied. The sludge volume index (SVI) reduced from 200 to 80 ml g(-1) and foaming was suppressed significantly, indicating the effectiveness of the anaerobic selector in improving sludge settleability. The phosphorus removal efficiency was 66%, and 7.5 mg HAc-COD was consumed per mg PO4(3-) -P removed. In the anaerobic compartment, 31% of the SCOD and 73% of the acetic acid in the settled sewage were removed with PO4(3-) -P release of 14.1 mg PO4(3-)-P l(-1). The linear correlation between PO4(3-) -P release in the anaerobic compartment and PO4(3-) -P uptake in the aerobic compartment indicates that there is about 0.8 mg PO4(3-) -P release in the anaerobic compartment per mg PO34(3-) -P uptake in the aerobic compartment. The fates of volatile fatty acids (VFAs) and its short chain acids (SCAs) in the process were studied and discussed. 相似文献
99.
The main factors that determine the uniformity with which smelting products are tapped from a blast furnace are the rate of accumulation of the products in the hearth and the tapping rate. The first parameter is in turn determined by the stability of the furnace’s operation and can vary significantly even over the course of 24 h. The second parameter is determined mainly by the condition of the iron notch, the maintenance it receives, any changes that occur in the diameter of the channel of the notch, and the quality of the materials used to form the notch. Recommendations are presented to optimize tapping of the smelting products. 相似文献
100.
D. A. Mirzaev N. I. Vorob’ev O. K. Tokovi D. V. Shaburov E. A. Fominykh 《Russian Metallurgy (Metally)》2006,(1):38-41
The solutions to a differential equation for the problem of heating of a cylinder in a medium with a fixed temperature are used to obtain equations for estimating the change in the hydrogen concentration in forgings from data on the hydrogen concentration at the cylinder axis or on the average bulk hydrogen concentration. Similar equations are also obtained for forgings having square cross sections. The calculation demonstrates that, for the case of a twofold decrease in the hydrogen concentration in a forging, the calculated times of annealing of a cylindrical forging differ by three times. 相似文献