全文获取类型
收费全文 | 122656篇 |
免费 | 7818篇 |
国内免费 | 2931篇 |
专业分类
电工技术 | 4570篇 |
技术理论 | 6篇 |
综合类 | 4491篇 |
化学工业 | 23225篇 |
金属工艺 | 6071篇 |
机械仪表 | 8037篇 |
建筑科学 | 6296篇 |
矿业工程 | 2428篇 |
能源动力 | 4340篇 |
轻工业 | 8558篇 |
水利工程 | 1271篇 |
石油天然气 | 5364篇 |
武器工业 | 462篇 |
无线电 | 15378篇 |
一般工业技术 | 19889篇 |
冶金工业 | 7801篇 |
原子能技术 | 1410篇 |
自动化技术 | 13808篇 |
出版年
2024年 | 349篇 |
2023年 | 1825篇 |
2022年 | 2956篇 |
2021年 | 4352篇 |
2020年 | 3247篇 |
2019年 | 3103篇 |
2018年 | 3695篇 |
2017年 | 3885篇 |
2016年 | 3799篇 |
2015年 | 3970篇 |
2014年 | 5487篇 |
2013年 | 7176篇 |
2012年 | 7554篇 |
2011年 | 8689篇 |
2010年 | 6948篇 |
2009年 | 6868篇 |
2008年 | 6630篇 |
2007年 | 5889篇 |
2006年 | 5805篇 |
2005年 | 5166篇 |
2004年 | 3837篇 |
2003年 | 3582篇 |
2002年 | 3177篇 |
2001年 | 2758篇 |
2000年 | 2806篇 |
1999年 | 2975篇 |
1998年 | 3332篇 |
1997年 | 2423篇 |
1996年 | 2213篇 |
1995年 | 1742篇 |
1994年 | 1414篇 |
1993年 | 1129篇 |
1992年 | 838篇 |
1991年 | 708篇 |
1990年 | 587篇 |
1989年 | 494篇 |
1988年 | 430篇 |
1987年 | 310篇 |
1986年 | 240篇 |
1985年 | 209篇 |
1984年 | 159篇 |
1983年 | 103篇 |
1982年 | 82篇 |
1981年 | 68篇 |
1980年 | 55篇 |
1979年 | 44篇 |
1978年 | 33篇 |
1977年 | 45篇 |
1976年 | 69篇 |
1975年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
2.
3.
S H Lee J H Ko J R Kim Y J Kim J J Lee C W Kim T H Lee 《Water science and technology》2006,53(4-5):115-123
The adverse effect of nitrate on the phosphate release rate in the anaerobic phase was observed and was hardly explainable with conventional EBPR process models. Four possible mechanisms were proposed including substrate competition, reduced fermentation, parallel reaction and sequential reaction. Batch experiments were designed and conducted to identify the dominant mechanism. Results showed that the sequential reaction was the only possible mechanism where only denitrification occurred if any nitrate existed in the anaerobic phase. Then the phosphate release following after the nitrate was completely removed. Nitrate inhibition effect was added into the PHA storage rate to incorporate the sequential reaction in the conventional ASM3 plus EAWAG bio-P module (ASM3 + P). Nitrate inhibition coefficient, K(I,NO,PAO) was found to be as low as 0.05 mg/L. This correlated well with experimental observation where no also meant that the anaerobic compartment of a continuous flow reactor could be seriously affected by the residual nitrate contained in the sludge recycle flow. This phenomenon caused overestimation of the phosphate uptake rate and consequently underestimation of PO4(3-) -P concentration. This problem was resolved by incorporation of a nitrate inhibition term in the ASM3 + P for more accurate simulation of the EBPR process. 相似文献
4.
孙洪松 《石油化工管理干部学院学报》2006,(1):52-55
目前,我国股票市场上的股票评级尚处于探索阶段,评级时多采用专家法或历史法,而对于影响股票评级的各因素的确定以及因素间的相互作用缺乏定量分析。研究将结构模型应用到我国股票市场的股票评级中,建立关于我国股票评级的财务结构模型;分析各个因素对股票评级的影响;建立股票评级经验模式值。 相似文献
5.
针对不同地质目标的叠前时间偏移成像解释评价 总被引:3,自引:0,他引:3
随着计算机硬件和地震勘探成像技术的发展,叠前时间偏移正逐步替代常规的NMO加DMO加叠后时间偏移成为地震数据成像处理方法的主流。但对于不同的地质目标,叠前时间偏移的成像效果是否优于常规NMO加DMO加叠后时间偏移的成像效果呢?为此,从地震数据成像处理方法、处理流程和处理参数等方面进行了讨论,并基于某地区三维数据常规处理结果和叠前时间偏移处理结果,针对不同地质目标进行了剖析与评价。认为:叠前时间偏移成像的垂向分辨率较常规处理明显降低,但对于空间波阻抗变化明显的河流和断层,叠前时间偏移成像的空间分辨率要高于常规处理;对于小于1/4波长的叠置薄储层,叠前时间偏移成像的垂向和空间分辨率低于常规处理结果。 相似文献
6.
Namyong Kim 《ETRI Journal》2006,28(2):155-161
In this paper, we introduce an escalator (ESC) algorithm based on the least squares (LS) criterion. The proposed algorithm is relatively insensitive to the eigenvalue spread ratio (ESR) of an input signal and has a faster convergence speed than the conventional ESC algorithms. This algorithm exploits the fast adaptation ability of least squares methods and the orthogonalization property of the ESC structure. From the simulation results, the proposed algorithm shows superior convergence performance. 相似文献
7.
Flotation is a water treatment alternative to sedimentation, and uses small bubbles to remove low-density particles from potable water and wastewater. The effect of zeta potential, bubble size and particle size on removal efficiency of the electro-flotation process was investigated because previous model-simulations indicated that these attributes are critical for high collision efficiency between micro-bubbles and particles. Solutions containing Al3+ as the metal ion were subjected to various conditions. The zeta potentials of bubbles and particles were similar under identical conditions, and their charges were influenced by metal ion concentration and pH. Maximum removal efficiency was 98 and 12% in the presence and absence of flocculation, respectively. Removal efficiency was higher when particle size was similar to bubble size. These results agree with modelling simulations and indicate that collision efficiency is greater when the zeta potential of one is negative and that of the other is positive and when their sizes are similar. 相似文献
8.
根据Flether等人的研究,基于感知独立性假设的子带识别方法被用于抗噪声鲁棒语音识别。本文拓展子带方法,采用基于噪声污染假定的多带框架来减少噪声影响。论文不仅从理论上分析了噪声污染假定多带框架在识别性能上的潜在优势,而且提出了多带环境下的鲁棒语音识别算法。研究表明:多带框架不仅回避了独立感知假设要求,而且与子带方法相比,多带方法能更好的减少噪声影响,提高系统识别性能。 相似文献
9.
Because biological wastewater treatment plants (WWTPs) involve a long time-delay and various disturbances, in general, skilled operators manually control the plant based on empirical knowledge. And operators usually diagnose the plant using similar cases experienced in the past. For the effective management of the plant, system automation has to be accomplished based upon operating recipes. This paper introduces automatic control and diagnosis based upon the operator's knowledge. Fuzzy logic was employed to design this knowledge-based controller because fuzzy logic can convert the linguistic information to rules. The controller can manage the influent and external carbon in considering the loading rate. The input of the controller is not the loading rate but the dissolved oxygen (DO) lag-time, which has a strong relation to the loading rate. This approach can replace an expensive sensor, which measures the loading rate and ammonia concentration in the reactor, with a cheaper DO sensor. The proposed controller can assure optimal operation and prevent the over-feeding problem. Case-based diagnosis was achieved by the analysis of profile patterns collected from the past. A new test profile was diagnosed by comparing it with template patterns containing normal and abnormal cases. The proposed control and diagnostic system will guarantee the effective and stable operation of WWTPs. 相似文献
10.
杨宇 《中国室内装饰装修天地》2006,(7):54-61
华风气象影视大楼总面积4万平方米,根据空间功能不同分为办公大楼和商务写字楼两部分,办公大楼是集演播室、制作机房、办公室为一体的九层综合性建筑。设计师杨宇在刚接触到这个项目的时候,面对的是一个既成事实的建筑。 相似文献