全文获取类型
收费全文 | 13143篇 |
免费 | 1026篇 |
国内免费 | 494篇 |
专业分类
电工技术 | 669篇 |
综合类 | 683篇 |
化学工业 | 2296篇 |
金属工艺 | 685篇 |
机械仪表 | 816篇 |
建筑科学 | 904篇 |
矿业工程 | 334篇 |
能源动力 | 411篇 |
轻工业 | 744篇 |
水利工程 | 177篇 |
石油天然气 | 856篇 |
武器工业 | 72篇 |
无线电 | 1827篇 |
一般工业技术 | 1695篇 |
冶金工业 | 664篇 |
原子能技术 | 89篇 |
自动化技术 | 1741篇 |
出版年
2024年 | 43篇 |
2023年 | 223篇 |
2022年 | 355篇 |
2021年 | 514篇 |
2020年 | 343篇 |
2019年 | 308篇 |
2018年 | 345篇 |
2017年 | 382篇 |
2016年 | 361篇 |
2015年 | 488篇 |
2014年 | 663篇 |
2013年 | 802篇 |
2012年 | 772篇 |
2011年 | 926篇 |
2010年 | 777篇 |
2009年 | 715篇 |
2008年 | 759篇 |
2007年 | 689篇 |
2006年 | 746篇 |
2005年 | 665篇 |
2004年 | 424篇 |
2003年 | 361篇 |
2002年 | 296篇 |
2001年 | 276篇 |
2000年 | 275篇 |
1999年 | 395篇 |
1998年 | 356篇 |
1997年 | 269篇 |
1996年 | 257篇 |
1995年 | 184篇 |
1994年 | 176篇 |
1993年 | 115篇 |
1992年 | 99篇 |
1991年 | 67篇 |
1990年 | 58篇 |
1989年 | 37篇 |
1988年 | 28篇 |
1987年 | 9篇 |
1986年 | 23篇 |
1985年 | 6篇 |
1984年 | 14篇 |
1983年 | 7篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
本文研究了从发酵液中用D2EHPA-煤油溶剂萃取分离L-异亮氨酸工艺.考察了萃取时pH值、萃取剂浓度和异亮氨酸浓度对于异亮氨酸和缬氨酸的萃取分配比的影响.在计算机上进行回归,得到以下分配模型:当1≤pH≤3.5时lgDIle=0.09906pH2+0.8625pH+2.2696lgCHR-0.09188lg2CIle+0.1766lgCIle-1.366lgDrmVal=-0.0293pH2+0.550pH+1.2659lgCHR-0.2420lg2CIle+0.4549lgCIle-1.696用此模型,应用分馏萃取理论,进行逐级计算,求取了萃取工艺的主要参数,并在φ20mm的多级离心萃取器上对上述结果进行了验证.结果表明:当CHR浓度为1.5mol/L,相比V:L:L’=2:1:2,N’=3,N=6时,异亮氨酸的收率达到90%以上,纯度>99%.实验取得了较为满意的结果. 相似文献
112.
Traditional methods based on the product of exponentials (POE) formula are parametrically continuous and complete for the calibration of the kinematic parameters of serial robots. However, these methods are not minimal due to the constraints of joint twists. This paper puts forward a new POE-based model, whose parameters are totally independent and conform to the formula of minimality. This is the first model that simultaneously satisfies the requirements of parametric continuity, completeness, and minimality with uniform and generic modeling rules. The proposed approach avoids the operations of normalization and orthogonalization which are necessary redundancy elimination steps with the traditional model. Simulations on a SCARA robot and experiments on an ABB IRB 120 robot prove that the new model outperforms in convergence, accuracy, and efficiency. 相似文献
113.
Intuitionistic fuzzy sets (IFSs) have attracted more and more scholars’ attention due to their powerfulness in expressing vagueness and uncertainty. In the course of decision making with IFSs, aggregation operators play a very important role since they can be used to synthesize multidimensional evaluation values represented as intuitionistic fuzzy values into collective values. This paper proposes a family of intuitionistic fuzzy hybrid weighted aggregation operators, such as the intuitionistic fuzzy hybrid weighted averaging operator, the intuitionistic fuzzy hybrid weighted geometric operator, the generalized intuitionistic fuzzy hybrid weighted averaging operator, and the generalized intuitionistic fuzzy hybrid weighted geometric operator. All these newly developed operators not only can weight both the arguments and their ordered positions simultaneously but also have some desirable properties, such as idempotency, boundedness, and monotonicity. To show the applications of our proposed intuitionistic fuzzy hybrid weighted aggregation operators, a simple schema for decision making with intuitionistic fuzzy information is developed. An example concerning the human resource management is given to illustrate the validity and applicability of the proposed method and also the hybrid weighted aggregation operators. 相似文献
114.
115.
生物质中元素分布特征的聚类分析研究 总被引:2,自引:0,他引:2
测定了稻草秆、小麦秆、玉米秆、棉花秆、大豆秆、玉米芯、花生壳和柳树、松树、桦树、杨树、杉树 1 2个农业生物质和林业生物质种类 2 7个样品中主要元素 K,Ca,Na,Mg,Al,Fe,P和痕量元素 As,Cr,Co,Cu,Cd,Mn,Mo,Ni,Pb,Ti,Zn,V,Si,Ba,Be,Se,Sb,Ge,Hg的含量 ,并用SPSS聚类分析法分别进行了 R型和 Q型聚类研究 ,对这些元素在生物质中的分布特征进行了研究 .结果显示 :杨木、杉木和桦木与松木和柳木归成一大类 ,经济类作物黄豆秆和棉花秆分别归类后又归入一大类 ;农业生物质稻草秆和小麦秆、玉米秆被归入一类 ;虽然 2 7种生物质样品分别取自我国东北、华东、华北和西南地区 ,在地理位置上相距极远 ,但样品聚类谱系图表明 ,元素的分布特征与生物质的种类的关系显著 ,与产地的关系不明显 ,即元素的分布特征受种类的影响大 ,而受生长环境、气候、土壤条件的影响小 . 相似文献
116.
Ian Turk Matthew Sin Xin''an Zhou Jun Tao Chaoli Wang Qi Liao 《International Journal of Software and Informatics》2016,10(3)
We present a visual analytics system to understand the operation data of a
company, GAStech, from IEEE VAST Challenge 2016. The data include proximity data
recording the locations and movements of employees, and heating, ventilation, and air
conditioning (HVAC) data recording the environmental conditions in the building.
Analyzing the data to detect the suspicious behaviors of some disgruntled employees is of
special interest. Our system provides coordinated multiple views to visualize the proximity
data and the HVAC data over time. Visual hints and comparisons are designed for users to
identify abnormal patterns and compare them. Furthermore, the system automatically
detects and correlates the anomalies in the data. We provide use cases to demonstrate the
effectiveness of our system. 相似文献
117.
118.
A novel treatment process combining a membrane with outside-in flow configuration and a fluidized pellet rector for removing hardness was studied. The effects of influent water quality, e.g., concentrations of natural organic matter (NOM) and phosphate along with the hydrophobicity of NOM, on the hardness removal efficiency of the novel process were investigated. The hardness removal efficiency decreases with increasing NOM concentration. However, the NOM removal efficiency is independent of NOM concentration and is related to the hydrophobicity of NOM samples. Raw water containing phosphate has adverse impact on the hardness removal efficiency, which decreases from 85% for treating water containing no phosphate to only 38% and 14% for water containing 0.33 mg/L and 1.63 mg/L of phosphate, respectively. 相似文献
119.
概述了整流系统的配置,全数字化的计算机控制和监测系统,整流装置的电源和负载模式,整流辅助设备的新产品,新技术以及谐波抑制措施等新技术在工业上的应用现状。 相似文献
120.
聚烯烃接枝马来酸酐接枝率的测定—聚乙烯接枝 总被引:2,自引:1,他引:2
以非均相化学接枝法和红外光谱法相结合的方法绘制了定量校正曲线,可用于红外光谱法测定聚乙烯接枝马来酸酐的接枝率。该方法简便快速,准确可靠,重复性好。 相似文献