全文获取类型
收费全文 | 15124篇 |
免费 | 1284篇 |
国内免费 | 597篇 |
专业分类
电工技术 | 842篇 |
技术理论 | 2篇 |
综合类 | 871篇 |
化学工业 | 2651篇 |
金属工艺 | 945篇 |
机械仪表 | 962篇 |
建筑科学 | 1132篇 |
矿业工程 | 533篇 |
能源动力 | 446篇 |
轻工业 | 877篇 |
水利工程 | 239篇 |
石油天然气 | 1186篇 |
武器工业 | 102篇 |
无线电 | 1662篇 |
一般工业技术 | 1862篇 |
冶金工业 | 817篇 |
原子能技术 | 149篇 |
自动化技术 | 1727篇 |
出版年
2024年 | 53篇 |
2023年 | 287篇 |
2022年 | 437篇 |
2021年 | 645篇 |
2020年 | 507篇 |
2019年 | 434篇 |
2018年 | 502篇 |
2017年 | 511篇 |
2016年 | 434篇 |
2015年 | 597篇 |
2014年 | 774篇 |
2013年 | 828篇 |
2012年 | 948篇 |
2011年 | 1005篇 |
2010年 | 888篇 |
2009年 | 869篇 |
2008年 | 899篇 |
2007年 | 763篇 |
2006年 | 793篇 |
2005年 | 656篇 |
2004年 | 529篇 |
2003年 | 435篇 |
2002年 | 426篇 |
2001年 | 361篇 |
2000年 | 341篇 |
1999年 | 397篇 |
1998年 | 290篇 |
1997年 | 276篇 |
1996年 | 237篇 |
1995年 | 211篇 |
1994年 | 169篇 |
1993年 | 118篇 |
1992年 | 102篇 |
1991年 | 64篇 |
1990年 | 61篇 |
1989年 | 42篇 |
1988年 | 27篇 |
1987年 | 25篇 |
1986年 | 15篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 667 毫秒
151.
磷酸三聚氰胺复盐结晶法净化湿法磷酸技术进展 总被引:5,自引:0,他引:5
本文讨论了结晶法净化湿法磷酸方法,对复盐结晶法净化湿法磷酸生产磷酸盐,多聚磷酸盐的生产方法,工艺流程,工艺特点,产品质量进行了研究。 相似文献
152.
采用极限氧指数法、热重分析和差示扫描量热分析等技术和手段研究了氢氧化镁(MH)对乙烯-丙烯酸丁酯共聚物(EBA)的阻燃性能、力学性能及热降解行为的影响。结果表明:EBA/MH复合材料的拉伸强度、断裂伸长率和熔体流动速率均随着MH用量的增加而降低;当MH的质量分数为60%时,复合材料的极限氧指数可达34.3%;MH通过分解吸热可提高EBA的热稳定性;MH表面羟基与EBA的反应性基团发生相互作用,以及EBA发生酯裂解后形成的羧酸与MH反应形成热稳定性更高的离聚物,均可提高EBA在高温下的热稳定性,并改变EBA的热降解历程。MH的“热阱”机理对EBA的阻燃起着很重要的作用。 相似文献
153.
Jianjun Lei Kun Feng Meimin Wu Shuai Li Chunping Hou 《Multimedia Tools and Applications》2014,72(1):825-842
Rate control plays an important role in regulating bit streams in video coding. In order to obtain good coding performance, the hierarchical B prediction structure has been adopted in Multi-view Video Coding (MVC). However, the conventional rate control scheme is not efficient in the hierarchical B prediction structure. In this paper, we propose a rate control algorithm to address this problem. First, the accurate estimation of Mean Absolute Distortion (MAD) of the current frame is desired for both quantization parameter (QP) selection and Rate Distortion Optimization (RDO). Considering the hierarchical B structure, a bi-directional MAD prediction model is proposed to predict the MAD of the current frame by using the actual MADs of the encoded frames in the lower Temporal Layers (TLs). Second, the number of header bits has a close relationship with the TLs in the hierarchical B prediction structure. Therefore, we propose an enhanced prediction method in which a proportional relationship of the header bits is introduced if the frames are located in different TLs. Experimental results show that our proposed algorithm can achieve both accurate target bit rate and good coding performance. 相似文献
154.
155.
结合实际工作经验,讨论了整定计算软件在新型继电保护系统中应用的必要性,评定和探究了整定管理在继电保护故障分析中的运用,并总结了整定管理在整套系统中的实际应用。 相似文献
156.
A series of novel hydrogel polysucrose microspheres with the mean size ranging from 200 to 500 μm were prepared via two‐step method. First, soluble polysucrose was synthesized by solution polymerization between sucrose and epichlorohydrin; second, a reversed phase suspension crosslinking reaction was performed to prepare polysucrose microspheres. The SEM images indicated that these spherical beads had smooth surface and hydrogel interior structure. FTIR was used to characterize the chemical structure of the beads. The hydrated and dry densities, equilibrium water content, and hydroxyl content of polysucrose microspheres were also investigated. The characteristic of high hydroxyl content (15.48–19.04 mmol/g) make these microspheres suitable for protein adsorption. Meanwhile, bovine serum albumin was used to examine the adsorption capacity of the microspheres. These microspheres had a capacity as high as 49.28 mg/g. The adsorption kinetics and recycling of the beads were also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5934–5940, 2006 相似文献
157.
158.
推光漆是中国漆文化的重要组成部分。历史地看 ,推光漆注重人的德性培养、技气培养、美善培养和物化质量。推光漆的前人名之为“推光漆精神。”这种精神沿续甚久。在改革开放初期依然存在。失落推光漆精神始于二十世纪九十年代之初 ,企业承包 ,实行厂长 (经理 )责任制 ,抓经济放在了首位。抓经济 ,没有错 ,要富国强民 ,非走这条路子别无选择。问题是有些顾此失彼。其所失 ,那就是党的领导大大削弱 ,工会成了“喝凉水搭筷子” ,“职工之家”的牌子也摘了。几乎放弃了政治思想建设 ,放弃了爱岗敬业教育 ,放弃了推光漆精神。说是推光漆 ,若不说… 相似文献
159.
Trajectory tracking and roll stabilization are both vital practices in ship motion control. Trajectory tracking is a kind of low‐frequency control, while roll stabilization by means of fins is a kind of high‐frequency control. However, they have been studied separately previously; most tracking control of underactuated surface vessels in the previous studies do not account for roll stabilization by means of fins. In reality, however, they are an integral system. In this paper, a simple control strategy is proposed to achieve trajectory tracking and fin roll stabilization simultaneously. Four degrees of freedom derived from a six degrees of freedom mathematical model of a surface vessel is considered, including surge, sway, roll and yaw. Surge force, roll moment and yaw moment are considered as control inputs, while position, yaw angle and roll angle are controlled. The number of control inputs is fewer than the outputs to be controlled. Therefore, we are dealing with an underactuated problem. An adaptive hierarchical sliding mode control technique is employed to deal with the underactuation. Stabilization of underactuated surface vessels is studied as a special case. Random waves are applied to test the robustness of the designed controllers. Lyapunov stability theory is used to show the stability of closed‐loop system. The simulation results verify the effectiveness of the proposed strategy. 相似文献
160.
本文由无限稀释活度系数求取混合物MH-81状态方程的二元相互作用参数,预测了二元混合物的汽液平衡,获得了较满意的结果。 相似文献