全文获取类型
收费全文 | 13529篇 |
免费 | 1969篇 |
国内免费 | 1373篇 |
专业分类
电工技术 | 1845篇 |
技术理论 | 3篇 |
综合类 | 1543篇 |
化学工业 | 368篇 |
金属工艺 | 254篇 |
机械仪表 | 1861篇 |
建筑科学 | 458篇 |
矿业工程 | 238篇 |
能源动力 | 268篇 |
轻工业 | 123篇 |
水利工程 | 206篇 |
石油天然气 | 201篇 |
武器工业 | 129篇 |
无线电 | 1935篇 |
一般工业技术 | 860篇 |
冶金工业 | 155篇 |
原子能技术 | 139篇 |
自动化技术 | 6285篇 |
出版年
2024年 | 53篇 |
2023年 | 143篇 |
2022年 | 266篇 |
2021年 | 349篇 |
2020年 | 361篇 |
2019年 | 302篇 |
2018年 | 330篇 |
2017年 | 459篇 |
2016年 | 553篇 |
2015年 | 651篇 |
2014年 | 895篇 |
2013年 | 847篇 |
2012年 | 1104篇 |
2011年 | 1103篇 |
2010年 | 815篇 |
2009年 | 833篇 |
2008年 | 885篇 |
2007年 | 1043篇 |
2006年 | 888篇 |
2005年 | 820篇 |
2004年 | 729篇 |
2003年 | 588篇 |
2002年 | 480篇 |
2001年 | 402篇 |
2000年 | 348篇 |
1999年 | 253篇 |
1998年 | 210篇 |
1997年 | 208篇 |
1996年 | 164篇 |
1995年 | 152篇 |
1994年 | 133篇 |
1993年 | 98篇 |
1992年 | 105篇 |
1991年 | 45篇 |
1990年 | 46篇 |
1989年 | 45篇 |
1988年 | 36篇 |
1987年 | 24篇 |
1986年 | 17篇 |
1985年 | 23篇 |
1984年 | 17篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Investigation on the miniaturized parallel multichannel-based devices packed with glass beads to improve the mass exchange execution is the critical focal point of the current study. One of the essential parameters to specify the miniaturized devices' flow distribution is the residence time distribution (RTD). In the present context, the RTDs of a liquid tracer were investigated for the air-water multiphase flows (concurrent) across the multichannel-based miniaturized devices (comprising of 11 similar dimensional parallel channels). The devices were variable in height and packed with glass beads. The conductivity estimations generated the RTD curves and were addressed by the axial dispersion model (ADM). The fluid-flow rates differed within the range of 5–23 ml min−1. The axial dispersion coefficients and the rate of the specific energy dispersion were investigated. The effects of pressure difference and geometry on the hydrodynamic attributes and mixing properties were well-illustrated, and the new correlations were suggested. 相似文献
2.
《Advanced Powder Technology》2022,33(11):103627
Naringin (NAR), a major flavanone (FVA) glycoside, is a component of food mainly obtained from grapefruit. We used NAR as a food additive to improve the solubility and permeability of hydrophobic polyphenols used as supplements in the food industry. The spray-dried particles (SDPs) of NAR alone show an amorphous state with a glass transition temperature (Tg) at 93.2 °C. SDPs of hydrophobic polyphenols, such as flavone (FVO), quercetin (QCT), naringenin (NRG), and resveratrol (RVT) were prepared by adding varying amounts of NAR. All SDPs of hydrophobic polyphenols with added NAR were in an amorphous state with a single Tg, but SDPs of hydrophobic polyphenols without added NAR showed diffraction peaks derived from each crystal. The SDPs with NAR could keep an amorphous state after storage at a high humidity condition for one month, except for SDPs of RVT/NAR. SDPs with NAR enhanced the solubility of hydrophobic polyphenols, especially NRG solubility, which was enhanced more than 9 times compared to NRG crystal. The enhanced solubility resulted in the increased membrane permeability of NRG. The antioxidant effect of the hydrophobic NRG was also enhanced by the synergetic effect of NAR. The findings demonstrated that NAR could be used as a food additive to enhance the solubility and membrane permeability of hydrophobic polyphenols. 相似文献
3.
4.
5.
针对平面并联机构无奇异位置工作空间求解困难、过程繁琐、计算量大等问题,提出了基于CAD求解平面并联机构工作空间的三维螺旋扫描方法。将[n]自由度平面并联机构分解成[n]条支链进行独立分析,得到每条支链下末端执行器的可达区域,再将所有支链可达区域取交集即为平面并联机构工作空间。应用SolidWorks软件建立平面并联机构模型,进行几何特征处理,通过自动求解器求解,将求解过程图形化,快速得到同轴布局5R机构和平面3-RPR并联机构的无奇异位置工作空间。通过同轴布局5R机构的运动学实验,验证了该求解方法的可行性。 相似文献
6.
Mohamed Becherif 《Asian journal of control》2019,21(4):2137-2154
Induction machines (IM) constitute a theoretically interesting and practically important class of nonlinear systems. They are frequently used as wind generators for their power/cost ratio. They are described by a fifth‐order nonlinear differential equation with two inputs and only three state variables available for measurement. The control task is further complicated by the fact that IM are subject to unknown (load) disturbances and the parameters can be of great uncertainty. One is then faced with the challenging problem of controlling a highly nonlinear system, with unknown time‐varying parameters, where the regulated output, besides being unmeasurable, is perturbed by an unknown additive signal. Passivity‐based control (PBC) is a well‐established structure‐preserving design methodology which has shown to be very powerful to design robust controllers for physical systems described by Euler‐Lagrange equations of motion. PBCs provide a natural procedure to "shape" the potential energy yielding controllers with a clear physical interpretation in terms of interconnection of the system with its environment and are robust vis á vis to unmodeled dissipative effects. One recent approach of PBC is the Interconnection and Damping Assignment Passivity‐Based Control (IDA‐PBC) which is a very useful technique to control nonlinear systems assigning a desired (Port‐Controlled Hamiltonian) structure to the closed‐loop. The aim of this paper is to give a survey on different PBC of IM. The originality of this work is that the author proves that the well known field oriented control of IM is a particular case of the IDA‐PBC with disturbance. 相似文献
7.
In this paper, we study scheduling games under mixed coordination mechanisms on hierarchical machines. The two scheduling policies involved are ‐ and ‐, where ‐ (resp., ‐) policy sequences jobs in nondecreasing order of their hierarchies, and jobs of the same hierarchy in nonincreasing (resp., nondecreasing) order of their processing times. We first show the existence of a Nash equilibrium. Then we present the price of anarchy and the price of stability for the games with social costs of minimizing the makespan and maximizing the minimum machine load. All the bounds given in this paper are tight. 相似文献
8.
9.
基于PC机群的大地电磁Occam反演并行计算研究 总被引:4,自引:0,他引:4
Occam反演以其稳定收敛和不依赖于初始模型的特性被广泛应用于大地电磁数据的处理,但偏导数矩阵的计算和拉格朗日乘子的求取导致大量的模型正演,使得反演速度较低。为此,研究了用基于PC机群的并行计算来解决这一问题的方法。首先对Occam反演方法进行了阐述;然后,分析了反演方法中各计算耗费的时间,提出对约占计算量90%的偏导数和拉格朗日乘子进行并行计算的思想,即偏导数计算采用频点计算一级的大粒度并行,拉格朗日乘子扫描和一维搜索分别采用弘值计算一级的大粒度并行和频点计算一级的小粒度并行;给出了并行计算的实现方法,即在PC机群上,利用主一从编程模式实现Occam反演的整体并行计算。在计算中,采用任务组合方式,减少了通信量,较好地实现了负载均衡。在4节点PC机群上,对应于拉格朗日乘子的扫描和一维搜索方式,整体加速比分别达到3.36和2.83。 相似文献
10.
开关电源的平均电流自动均流技术 总被引:1,自引:0,他引:1
针对多个开关电源并联时易出现负载电流在各模块间分配不均的现象,介绍了常用的负载电流自动均流法——平均电流自动均流法及其工作特性。并针对其存在母线电压降低的缺陷,提出了一种改进的平均电流自动均流方法,经试验证明均流精度比较高。 相似文献