全文获取类型
收费全文 | 55877篇 |
免费 | 6365篇 |
国内免费 | 3545篇 |
专业分类
电工技术 | 3724篇 |
技术理论 | 1篇 |
综合类 | 4490篇 |
化学工业 | 8679篇 |
金属工艺 | 3201篇 |
机械仪表 | 3665篇 |
建筑科学 | 4095篇 |
矿业工程 | 1464篇 |
能源动力 | 1402篇 |
轻工业 | 5941篇 |
水利工程 | 1271篇 |
石油天然气 | 2216篇 |
武器工业 | 583篇 |
无线电 | 6686篇 |
一般工业技术 | 6346篇 |
冶金工业 | 2118篇 |
原子能技术 | 662篇 |
自动化技术 | 9243篇 |
出版年
2024年 | 284篇 |
2023年 | 978篇 |
2022年 | 1926篇 |
2021年 | 2588篇 |
2020年 | 1954篇 |
2019年 | 1626篇 |
2018年 | 1790篇 |
2017年 | 1875篇 |
2016年 | 1818篇 |
2015年 | 2524篇 |
2014年 | 3168篇 |
2013年 | 3766篇 |
2012年 | 4281篇 |
2011年 | 4712篇 |
2010年 | 4252篇 |
2009年 | 4145篇 |
2008年 | 4011篇 |
2007年 | 3719篇 |
2006年 | 3352篇 |
2005年 | 2780篇 |
2004年 | 1988篇 |
2003年 | 1533篇 |
2002年 | 1436篇 |
2001年 | 1208篇 |
2000年 | 933篇 |
1999年 | 717篇 |
1998年 | 445篇 |
1997年 | 397篇 |
1996年 | 322篇 |
1995年 | 251篇 |
1994年 | 216篇 |
1993年 | 166篇 |
1992年 | 126篇 |
1991年 | 106篇 |
1990年 | 77篇 |
1989年 | 56篇 |
1988年 | 42篇 |
1987年 | 35篇 |
1986年 | 27篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 17篇 |
1980年 | 18篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 15篇 |
1975年 | 9篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
131.
永进油田目的层产状平缓,断层不发育,储层厚度小、埋深大、描述困难。运用伪波阻抗技术对该区的储层进行了研究,取得了较好的效果。 相似文献
132.
133.
134.
Robustness analysis of responses of vibration control structures with uncertain parameters using interval algorithm 总被引:1,自引:0,他引:1
Variations in system parameters due to uncertainties may result in system performance deterioration. Uncertainties in modeling of structures are often considered to ensure that control system is robust with respect to response errors. Hence, the uncertain concept plays an important role in vibration control of the engineering structures. The paper discusses the robustness of responses of vibration control systems with the uncertain parameters. The vibration control problem of an uncertain system is approximated by a deterministic one. The uncertain parameters are described by interval variables. The uncertain state matrix is constructed directly using system physical parameters and avoided to use bounds in Euclidean norm. The feedback gain matrix is determined based on the deterministic systems, and then it is applied to the actual uncertain systems. A method to calculate the upper and lower bounds of responses of the closed-loop system with uncertain parameters is presented. The upper bounds of responses can be used to estimate the robustness of responses of the controlled system with uncertain parameters. Two numerical examples are given to illustrate the applications of the present approach. 相似文献
135.
作者对5个盆地18个轻质油样品作了C_1—C_7轻烃分析,检测出29种单体轻烃。通过轻烃组成特征研究,认识到石蜡指数(PI_1)和庚烷值(PI_2)作为成熟度的指标,不受沉积盆地类型影响;C_6,C_7烃类族组分受母质类型影响较大。陆相(含煤地层)有机质生成轻质芳烃(苯)的含量比海相有机质要高。新疆塔里木盆地沙参2井原油的轻烃分析资料表明,该井油源岩为海相沉积。 相似文献
136.
137.
138.
Microwave plasma synthesis of TiN and ZrN nanopowders 总被引:2,自引:0,他引:2
This work demonstrates that TiN and ZrN nanopowders can be prepared by microwave plasma synthesis method. The effects of flow rate of plasma forming gas, flow rate of carrier gas and feeding rate of precursor raw material to the average particle size were studied. The TiN and ZrN nanopowders were characterized by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD). 相似文献
139.
In recent years, the Asia-Pacific region has experienced several financial setbacks, including speculative attacks in 1998 and the SARS outbreak in 2003. Financial stresses of this nature are unanticipated, and not all of the dangers can be predicted by the examination of market information and macroeconomic indicators. The Early Warning System (EWS) that has been adopted by the International Monetary Fund may not be able to predict future financial crises for all possible scenarios, because shocks come in many different forms. To supplement the EWS, this paper proposes a data mining framework to measure the resilience of an economy. The resilience framework does not predict a crisis, but rather assesses the current state of health of an economy and its ability to withstand a financial shock should one occur. The framework is based on a feedback system consisting of two stages. The first stage assigns a resilience score to each economy based on a fuzzy logic scoring scheme that is built on the ambiguous reasoning of experts. The second stage uses the classification tree approach to estimate thresholds for each economic indicator, and examines the quality of the fuzzy score. The result from the second stage is then passed back to the first stage as feedback. The final result is obtained when the feedback system reaches its equilibrium state. The proposed resilience framework is applied to the external-sector and the public-sector economies of several countries to illustrate its applicability. 相似文献
140.