全文获取类型
收费全文 | 14738篇 |
免费 | 2168篇 |
国内免费 | 1276篇 |
专业分类
电工技术 | 1453篇 |
技术理论 | 1篇 |
综合类 | 2682篇 |
化学工业 | 835篇 |
金属工艺 | 382篇 |
机械仪表 | 893篇 |
建筑科学 | 906篇 |
矿业工程 | 315篇 |
能源动力 | 359篇 |
轻工业 | 377篇 |
水利工程 | 318篇 |
石油天然气 | 452篇 |
武器工业 | 147篇 |
无线电 | 1811篇 |
一般工业技术 | 2220篇 |
冶金工业 | 469篇 |
原子能技术 | 176篇 |
自动化技术 | 4386篇 |
出版年
2024年 | 24篇 |
2023年 | 182篇 |
2022年 | 263篇 |
2021年 | 408篇 |
2020年 | 549篇 |
2019年 | 535篇 |
2018年 | 510篇 |
2017年 | 622篇 |
2016年 | 677篇 |
2015年 | 629篇 |
2014年 | 828篇 |
2013年 | 1000篇 |
2012年 | 1060篇 |
2011年 | 1118篇 |
2010年 | 856篇 |
2009年 | 899篇 |
2008年 | 893篇 |
2007年 | 999篇 |
2006年 | 825篇 |
2005年 | 706篇 |
2004年 | 624篇 |
2003年 | 622篇 |
2002年 | 491篇 |
2001年 | 453篇 |
2000年 | 401篇 |
1999年 | 299篇 |
1998年 | 227篇 |
1997年 | 231篇 |
1996年 | 200篇 |
1995年 | 164篇 |
1994年 | 168篇 |
1993年 | 114篇 |
1992年 | 125篇 |
1991年 | 83篇 |
1990年 | 75篇 |
1989年 | 59篇 |
1988年 | 44篇 |
1987年 | 22篇 |
1986年 | 21篇 |
1985年 | 16篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 14篇 |
1981年 | 25篇 |
1980年 | 20篇 |
1979年 | 20篇 |
1978年 | 8篇 |
1966年 | 5篇 |
1964年 | 13篇 |
1963年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
61.
C. S. Sravanthi 《亚洲传热研究》2020,49(1):86-102
The purpose of the present paper is to explore the second order slip effects on nanofluid flow over a vertical cone. The effects of nonlinear thermal radiation and nonuniform heat source/sink are also taken into account. Water with copper nanoparticles is used as nanofluid in this investigation. The governing partial differential equations for the flow are converted into ordinary differential equations by using transformations and then are solved using homotopy analysis method. The influence of various important parameters on velocity, temperature, skin‐friction, and Nusselt number are presented through graphs. Results indicate that the velocity and magnitude of skin friction decrease with a rise in first and second order velocity slips. A raise in either first or second order temperature jump causes a fall in temperature. Nonlinear radiation increases the more rapidly when compared to the linear radiation case. 相似文献
62.
榆神矿区浅表层水资源短缺,生态脆弱,在划分主采煤层上覆含、隔水层组合类型的基础上,采用Visual Modflow软件构建煤层开采的地下水流数值模型,研究地下水流场演化规律,统计区内地下水位观测网(56个水文观测孔)近3年的有效观测数据,掌握首采煤层开采地下水位动态变化。结果表明:2020年第四系萨拉乌苏组潜水流场与2005年统测地下水流场形态基本一致,地下水位降深值在西南部达10 m;近3年的地下水位未发生明显变化,仅YS22钻孔处受村民井取水引起水位下降。研究成果对榆神矿区地下水资源保护与利用具有重要的指导意义。 相似文献
63.
We propose a general n-fractal aperiodic zone plate generating a beam with the first-order foci with more chosen positions. The construction method of the general n-fractal aperiodic zone plate can apply to many aperiodic zone plates, e.g. fractal, Thue-Morse and Fibonacci zone plates, and the general n-fractal aperiodic zone plates can generate more adjustable first-order foci. Parameters of the n-fractal aperiodic zone plate such as the substitution rule and the fractal order are examined and found not to affect the fractal distribution of the first-order foci. The more adjustable first-order foci generated by the general n-fractal aperiodic zone plate have been verified with both simulations and experiments. 相似文献
64.
Pradum Pundlikrao Ige Rohit Ravindra Badgujar Pankaj Padmakar Nerkar Hitendra Shaligram Mahajan Raju Onkar Sonawane Sanjay Javarilal Surana 《Particulate Science and Technology》2018,36(5):583-591
Drug which shows extensive first pass effect is difficult task that, needs to be solved by formulators in the pharmaceutical science. The low oral bioavailability (49%) of flutamide may be due to poor wettability, low aqueous solubility and extensive first pass effect. The aim of present investigation was to prepare flutamide loaded microspheres and incorporate it into suppositories for rectal delivery to avoid first pass effect and enhance residence time. Flutamide loaded mucoadhesive microspheres of Ocimum Basilicum mucilage (OBM) were prepared using spray drying and characterized by percent production yield, encapsulation efficiency, particle size, zeta potential, polydispersity index, DSC, SEM, XRPD, in vitro drug release and stability studies. Moreover, ex vivo mucoadhesion was investigated using falling liquid film technique to determine the adhesion of microspheres to sheep rectal mucosa. The microspheres had nearly spherical shape and size about 2.53?μm. The encapsulation efficiency and mucoadhesion of optimized formulation MBF10 were found to be 69.6?±?2.3% and 89.01?±?2.18%, respectively. Percent CDR of optimized flutamide loaded mucoadhesive microspheres was found to be 88.7?±?1.3 at 7?h. In conclusion, OBM microparticles based suppository could be used to deliver drug through rectal delivery. 相似文献
65.
66.
This study proposes a method of constructing type II generalized angulated elements (GAEs II) Hoberman sphere mechanisms on the basis of deployment axes that intersect at one point. First, the constraint conditions for inserting n GAEs II into n deployment axes to form a loop are given. The angle constraint conditions of the deployment axes are obtained through a series of linear equations. Second, the connection conditions of two GAEs II loops that share a common deployable center are discussed. Third, a flowchart of constructing the generalized Hoberman sphere mechanism on the basis of deployment axes is provided. Finally, four generalized Hoberman sphere mechanisms based on a fully enclosed regular hexahedron, arithmetic sequence axes, orthonormal arithmetic sequence axes, and spiral-like axes are constructed in accordance with the given arrangement of deployment axes that satisfy the constraint conditions to verify the feasibility of the proposed method. 相似文献
67.
为缩短常村煤矿S2采区S206综放面的初次来压步距,以邻近的S208综放面为工程背景,根据聚能爆破机理分析,研究出一种聚能装药结构,利用聚能爆破的特性来提高顶板预裂效果。再通过ANSYS/LS-DYNA数值模拟,从应力云图、裂隙半径及压力-时间历程分析直接装药和聚能装药两种方式爆破的预裂效果,得出聚能装药爆破具有聚能效应,预裂效果更佳,更能弱化顶板,保障初采期安全。最终得出S208综放面初次来压步距为15.2m,与S206综放面相比,缩短了2.4m,提高了初采采出率,具有良好的经济价值和应用价值。 相似文献
68.
Weibing Guo Haitao Xue Xin Wei Xiaoming Zhang 《International Journal of Applied Ceramic Technology》2020,17(3):1286-1292
Ti element is an important active element in brazing Zirconia ceramic (ZrO2) ceramic. Therefore, the interface bonding mechanism of Ti and ZrO2 was studied by using first principles calculation. Two kinds of interfaces with different termination and stacking sequence were established, and the interfacial bonding mechanism was studied using work of adhesion (Wad), electronic behavior and interface energy. The results show that in the O-terminated interface, Ti and O form a strong ion-covalent bond at the interface, and the Wad can reach 13.61 J/m2. In the Zr-terminated interface, Ti and Zr form a metal-covalent bond, and the Wad is 5.56 J/m2. At a temperature of 1123K, when the lnPO2 is larger than e−17, the O-rich interface is more stable in thermodynamics. Therefore, under the experimental condition, the interface tends to form Ti-O compounds when ZrO2 is brazed using Ag(Ti) filler metal. 相似文献
69.
Israel I. Zetina-Rios Gloria-L. Osorio-Gordillo Rodolfo A. Vargas-Méndez Guadalupe Madrigal-Espinosa Carlos-M. Astorga-Zaragoza 《International Journal of Adaptive Control and Signal Processing》2021,35(5):828-845
This article presents a generalized learning observer (GLO) design for the simultaneous estimation of states and actuator faults for polytopic quasi-linear parameter varying systems. The proposed approach is based on the use of a GLO, which generalized the existing results on the proportional-integral observers. Conditions of existence and stability of the observer are given through the stability analysis in the sense of Lyapunov. Its design is obtained in terms of a set of linear matrix inequalities. The performance of the proposed method is evaluated by simulation in a one-link-flexible joint robot system. 相似文献
70.
Jeongmook Lee Choah Kwon Jandee Kim Young‐Sang Youn Jong‐Yun Kim Byungchan Han Sang Ho Lim 《国际能源研究杂志》2019,43(8):3322-3329
We, for the first time, observe ZrO8 complex in Zr‐doped UO2, which is a corium structure, using experimental characterization integrated with first‐principle computational validation. Atomic level structure of U1?yZryO2 pellets (y = 0.01, 0.03, 0.05, and 0.1) is identified using Raman spectroscopy measurement and X‐ray diffraction pattern analysis. The lattice constants shrink with increasing Zr doping levels, which consistently represents in the positive shift of T2g Raman vibration peak around 445 cm?1. More interestingly, conventionally unknown new Raman peak appears around 598 cm?1, which has not been observed in neither a pure ZrO2 nor UO2 doped with tetravalent elements other than Zr. We unveil that the new peak originates from ZrO8‐type complex formed on the fluorite UO2. Our study provides precise understanding on the formation mechanisms and material properties of the corium in the hypervalent oxide. 相似文献