全文获取类型
收费全文 | 173505篇 |
免费 | 17979篇 |
国内免费 | 11182篇 |
专业分类
电工技术 | 12312篇 |
技术理论 | 2篇 |
综合类 | 19917篇 |
化学工业 | 22521篇 |
金属工艺 | 6744篇 |
机械仪表 | 11424篇 |
建筑科学 | 18516篇 |
矿业工程 | 7755篇 |
能源动力 | 5101篇 |
轻工业 | 18460篇 |
水利工程 | 6611篇 |
石油天然气 | 6957篇 |
武器工业 | 2130篇 |
无线电 | 11831篇 |
一般工业技术 | 19473篇 |
冶金工业 | 6925篇 |
原子能技术 | 2743篇 |
自动化技术 | 23244篇 |
出版年
2024年 | 826篇 |
2023年 | 2241篇 |
2022年 | 4209篇 |
2021年 | 4966篇 |
2020年 | 5655篇 |
2019年 | 4848篇 |
2018年 | 4709篇 |
2017年 | 5795篇 |
2016年 | 6395篇 |
2015年 | 6757篇 |
2014年 | 10546篇 |
2013年 | 10545篇 |
2012年 | 14060篇 |
2011年 | 13764篇 |
2010年 | 10477篇 |
2009年 | 10646篇 |
2008年 | 9842篇 |
2007年 | 12198篇 |
2006年 | 10676篇 |
2005年 | 8857篇 |
2004年 | 7211篇 |
2003年 | 6210篇 |
2002年 | 5118篇 |
2001年 | 4241篇 |
2000年 | 3764篇 |
1999年 | 3251篇 |
1998年 | 2558篇 |
1997年 | 2251篇 |
1996年 | 1864篇 |
1995年 | 1660篇 |
1994年 | 1381篇 |
1993年 | 1025篇 |
1992年 | 935篇 |
1991年 | 652篇 |
1990年 | 547篇 |
1989年 | 533篇 |
1988年 | 378篇 |
1987年 | 237篇 |
1986年 | 194篇 |
1985年 | 96篇 |
1984年 | 96篇 |
1983年 | 56篇 |
1982年 | 56篇 |
1981年 | 68篇 |
1980年 | 42篇 |
1979年 | 42篇 |
1978年 | 23篇 |
1977年 | 19篇 |
1974年 | 16篇 |
1959年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
From the principle of of the Domain Decomposition Method (DDM), we analyse the 2nd-order linear elliptic partial differential problems and link the Separated-Layers Algorithm (SLA) with DDM. The mathematical properties of SLA and numerical example are presented to obtain satisfactory computation results. For general linear differential ones, also are the structure of SLA and its characteristics discussed. 相似文献
72.
Three coupling strategies in matching the Ritz-Galerkin method and the finite element method are introduced for general elliptic equations, and useful numerical techniques are provided. Numerical experiments have been carried out for solving the typical, singular Motz problem, which shows that optimal convergence rates of numerical solutions can be achieved by using the combined methods and techniques provided in this paper. 相似文献
73.
用溶剂萃取法代替目前广泛使用的金泥处理方法,可以节约资源,降低成本,提高金的回收率,还能回收金泥中的银,产品金的纯度在99.9%以上;连续作业,操作方便,大大减轻劳动强度和改善工作条件,而且便于自动化操作管理,是一种社会,环境,经济三种效益都佳的成熟技术,应大力推广应用。 相似文献
74.
Target differentiation with simple infrared sensors using statistical pattern recognition techniques
Billur Barshan Author Vitae Tayfun Aytaç Author VitaeAuthor Vitae 《Pattern recognition》2007,40(10):2607-2620
This study compares the performances of various statistical pattern recognition techniques for the differentiation of commonly encountered features in indoor environments, possibly with different surface properties, using simple infrared (IR) sensors. The intensity measurements obtained from such sensors are highly dependent on the location, geometry, and surface properties of the reflecting feature in a way that cannot be represented by a simple analytical relationship, therefore complicating the differentiation process. We construct feature vectors based on the parameters of angular IR intensity scans from different targets to determine their geometry and/or surface type. Mixture of normals classifier with three components correctly differentiates three types of geometries with different surface properties, resulting in the best performance (100%) in geometry differentiation. Parametric differentiation correctly identifies six different surface types of the same planar geometry, resulting in the best surface differentiation rate (100%). However, this rate is not maintained with the inclusion of more surfaces. The results indicate that the geometrical properties of the targets are more distinctive than their surface properties, and surface recognition is the limiting factor in differentiation. The results demonstrate that simple IR sensors, when coupled with appropriate processing and recognition techniques, can be used to extract substantially more information than such devices are commonly employed for. 相似文献
75.
Maciej Winiewski Artur Jakubiak Jan Szymanowski 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):209-214
Decyl isonicotiniate and decyl nicotiniate permit a rapid extraction of palladium(II) from its hydrochloride solutions. Decyl picoliniate is not a suitable extractant. 4-Octylphenylamine can act as a phase transfer catalyst when its concentration in the organic phase is at least 2·5 × 10?4 M . It seems that the interfacial adsorption of pyridine carboxylates and of 4-octylphenylamine is not the decisive phenomenon in palladium(II) extraction. The negligible protonation of the pyridine-type extractants and the phase transfer catalysis explains well the quick extraction of palladium(II) with the commercial and highly hydrophobic extractant ACORGA CLX-50. 相似文献
76.
The method of Moser, Moin, and Leonard (1983) for the approximation of the three-dimensional Navier-Stokes equations using divergence-free subspaces is revisited and analyzed. It is shown that the computed velocity field converges to the physical one with spectral accuracy. Moreover, a method for recovering the pressure field is proposed. This method is stable and provides a pressure that converges to the physical one with spectral accuracy. 相似文献
77.
采用微波高压制样技术,快速提取饲料中的氟元素,结合氟离子选择性电极标准添加和电位极差测试方法,能够快速、准确地测试饲料中的含氟量 相似文献
78.
LIU Li xinEngineer Design Institute Changjiang Water Resources Commission Wuhan China CHANG Han junEngineer Design Institute Changjiang Water Resources Commission Wuhan China 《人民长江》2001,(Z1)
1 OverviewTheGeheyanPowerStationhasfourcircularinlettun nels,ontherightbankofdamsite,withtheirexcavationdi ameterof 11.3mto 12.5m,after liningdiameterof 9.5m,axis to axisspacingof2 4m.Thethicknessofpillarsareequaltothetunneldiameter.Theintakecenterisateleva ti… 相似文献
79.
Chestnuts were dehydrated by using a combined method of osmotic dehydration followed by air drying. Samples were osmotically pretreated with sucrose (60% w/w) and glucose (56% w/w) for 8 h, air-dried at temperatures of 45, 55, and 65°C, at a relative humidity of 30% and at a velocity of 2.7 m·s-1 and the experimental data of the drying kinetics were obtained. Whole samples were dried with different peelings: (a) removal of endocarp and pericarp (peeled) and (b) additionally the internal rough surface (cut). In all cases, cut chestnuts show greater drying rates than peeled samples, indicating that a significant mass transfer resistance in the layer nearest to the surface takes place. Peeled samples pretreated with sucrose solutions behave in a similar way to untreated samples. For the rest of the samples, the cut samples osmotically treated with sucrose solutions and all the samples treated with the glucose solution, the drying rates decrease during drying. Drying kinetics are successfully modeled by employing a diffusional model that takes the shrinkage into account. The effective coefficient of water diffusion was evaluated and correlated with temperature. The quality of the final product was monitored by color change. In spite of the fact that the total color difference is not modified by the osmotic treatment, the L*, a*, and b* color coordinates of cut samples treated with sucrose and glucose solutions do undergo changes; the L* and a* coordinates change less than the b*. 相似文献
80.
闩体的刚度和强度必须满足设计要求。用有限元法对复杂结构件进行力学性能分析是非常有效的方法。采用ANSYS软件对闩体进行了刚度和强度分析,得出了有用的结论,可供相关设计借鉴。 相似文献