全文获取类型
收费全文 | 554270篇 |
免费 | 6520篇 |
国内免费 | 1780篇 |
专业分类
电工技术 | 10147篇 |
综合类 | 442篇 |
化学工业 | 81711篇 |
金属工艺 | 22064篇 |
机械仪表 | 17757篇 |
建筑科学 | 12256篇 |
矿业工程 | 3179篇 |
能源动力 | 15321篇 |
轻工业 | 41653篇 |
水利工程 | 5968篇 |
石油天然气 | 10686篇 |
武器工业 | 23篇 |
无线电 | 65944篇 |
一般工业技术 | 111753篇 |
冶金工业 | 105159篇 |
原子能技术 | 12477篇 |
自动化技术 | 46030篇 |
出版年
2021年 | 5061篇 |
2020年 | 3806篇 |
2019年 | 4897篇 |
2018年 | 8273篇 |
2017年 | 8292篇 |
2016年 | 8804篇 |
2015年 | 5639篇 |
2014年 | 9331篇 |
2013年 | 26581篇 |
2012年 | 14955篇 |
2011年 | 20253篇 |
2010年 | 16145篇 |
2009年 | 18267篇 |
2008年 | 18698篇 |
2007年 | 18496篇 |
2006年 | 16416篇 |
2005年 | 14835篇 |
2004年 | 14110篇 |
2003年 | 14034篇 |
2002年 | 13122篇 |
2001年 | 13121篇 |
2000年 | 12481篇 |
1999年 | 13022篇 |
1998年 | 33252篇 |
1997年 | 23059篇 |
1996年 | 17792篇 |
1995年 | 13164篇 |
1994年 | 11729篇 |
1993年 | 11576篇 |
1992年 | 8509篇 |
1991年 | 8020篇 |
1990年 | 7842篇 |
1989年 | 7577篇 |
1988年 | 7223篇 |
1987年 | 6355篇 |
1986年 | 6136篇 |
1985年 | 6976篇 |
1984年 | 6383篇 |
1983年 | 5852篇 |
1982年 | 5304篇 |
1981年 | 5519篇 |
1980年 | 5030篇 |
1979年 | 5026篇 |
1978年 | 5012篇 |
1977年 | 5675篇 |
1976年 | 7528篇 |
1975年 | 4314篇 |
1974年 | 4074篇 |
1973年 | 4144篇 |
1972年 | 3435篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Malignant bone pain: pathophysiology and treatment 总被引:1,自引:0,他引:1
S Mercadante 《Canadian Metallurgical Quarterly》1997,69(1-2):1-18
2-acetyl aminofluorene (AAF) reacts in acidic conditions with nitrous fume yielding N-nitroso-AAF (N-NO-AAF), as previously described, that exerts more toxic and mutagenic effects than its parental compound. In this study, the effect of sodium nitrite (NaNO2) on the tumorigenicity of AAF in rats fed with AAF and NaNO2 was observed. Wistar rats were divided into five groups: group I served as control; group II were treated with NaNO2 (0.3%); group III was given 0.02% AAF alone; groups IV and V received both AAF and NaNO2 (0.2 and 0.3% respectively) in their diet for 12 weeks. At the end of the experiment, all rats in groups III, IV and V developed early stage phenomena of hepatocellular carcinoma, including hepatomegaly with variable-sized foci and neoplastic nodules. Severe damage was observed in the rats treated with AAF and NaNO2. Feeding of AAF (0.02%) for 3 months elevated the levels of c-Fos, c-Jun and c-Myc proteins in the rat livers. The AAF-induced c-Jun, c-Fos and c-Myc expressions were significantly magnified (P < 0.001) by NaNO2. These data confirmed that the strengthening of AAF-induced hepatocarcinogenesis by NaNO2 should be associated with its enhancing effect on the AAF-induced increases in the expressions of c-Jun, c-Fos and c-Myc. 相似文献
73.
Uses a Markov process to model a real-time expert system architecture characterized by message passing and event-driven scheduling. The model is applied to the performance evaluation of rule grouping for real-time expert systems running on this architecture. An optimizing algorithm based on Kernighan-Lin heuristic graph partitioning for the real-time architecture is developed and a demonstration system based on the model and algorithm has been developed and tested on a portion of the advanced GPS receiver (AGR) and manned manoeuvring unit (MMU) knowledge bases 相似文献
74.
Implementing a neural network on a digital or mixed analog and digital chip yields the quantization of the synaptic weights dynamics. This paper addresses this topic in the case of Kohonen's self-organizing maps. We first study qualitatively how the quantization affects the convergence and the properties, and deduce from this analysis the way to choose the parameters of the network (adaptation gain and neighborhood). We show that a spatially decreasing neighborhood function is far more preferable than the usually rectangular neighborhood function, because of the weight quantization. Based on these results, an analog nonlinear network, integrated in a standard CMOS technology, and implementing this spatially decreasing neighborhood function is then presented. It can be used in a mixed analog and digital circuit implementation. 相似文献
75.
76.
77.
Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 95–112, March–April, 1994. 相似文献
78.
S. Otakulov 《Cybernetics and Systems Analysis》1994,30(3):458-462
Translated from Kibernetika i Sistemnyi Analiz, No. 3, pp. 172–176, May–June, 1994 相似文献
79.
80.
An extended logistic model with a varying asymptotic upper bound for long-range peak demand forecasting is described. The model has been applied to a typical fast growing system, the Saudi Consolidated Electric Company. The forecasts are compared with actual demands and with those obtained from classical forecasting methods. The model gave relatively accurate peak demand forecasts compared with other classical methods. The model with a single load observation is capable of producing several peak demand forecasts corresponding to different levels of maximum temperature and various levels of social activity. The forecasts produced by the model were also stable irrespective of the length of the ex-post simulation period 相似文献