全文获取类型
收费全文 | 6345篇 |
免费 | 504篇 |
国内免费 | 155篇 |
专业分类
电工技术 | 254篇 |
综合类 | 527篇 |
化学工业 | 740篇 |
金属工艺 | 428篇 |
机械仪表 | 822篇 |
建筑科学 | 264篇 |
矿业工程 | 138篇 |
能源动力 | 142篇 |
轻工业 | 2397篇 |
水利工程 | 150篇 |
石油天然气 | 95篇 |
武器工业 | 48篇 |
无线电 | 88篇 |
一般工业技术 | 408篇 |
冶金工业 | 256篇 |
原子能技术 | 18篇 |
自动化技术 | 229篇 |
出版年
2024年 | 39篇 |
2023年 | 83篇 |
2022年 | 162篇 |
2021年 | 170篇 |
2020年 | 198篇 |
2019年 | 162篇 |
2018年 | 156篇 |
2017年 | 177篇 |
2016年 | 221篇 |
2015年 | 278篇 |
2014年 | 405篇 |
2013年 | 345篇 |
2012年 | 495篇 |
2011年 | 527篇 |
2010年 | 352篇 |
2009年 | 357篇 |
2008年 | 295篇 |
2007年 | 398篇 |
2006年 | 362篇 |
2005年 | 288篇 |
2004年 | 237篇 |
2003年 | 215篇 |
2002年 | 183篇 |
2001年 | 142篇 |
2000年 | 136篇 |
1999年 | 99篇 |
1998年 | 96篇 |
1997年 | 67篇 |
1996年 | 75篇 |
1995年 | 58篇 |
1994年 | 47篇 |
1993年 | 39篇 |
1992年 | 39篇 |
1991年 | 22篇 |
1990年 | 16篇 |
1989年 | 9篇 |
1988年 | 21篇 |
1987年 | 13篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1964年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有7004条查询结果,搜索用时 9 毫秒
1.
This work is devoted to the stress–strain state of isotropic double curved shell with defect system. The construction is weakened by two non-through thickness (internal) cracks of different length and by a circular hole located between cracks. In this study we use the line-spring model. Within the framework of this model cracks are modeled as mathematical cuts of shell’s middle surface. This leads to a two-dimensional problem. The problem is reduced to a system of eight boundary integral equations. To ensure the uniqueness of solution an additional equation is added. In the numerical solution of the problem special quadrature formulas for singular integrals of Cauchy type and the finite difference method are applied. The influence of defects on each other for double curved shell has been investigated. The given theoretical results can be used for the calculation of structural elements with holes, cracks on the strength and fracture toughness in various branches of engineering. 相似文献
2.
Effect of complexation of oxidised corn starch with mineral elements on physicochemical properties 下载免费PDF全文
Sławomir Pietrzyk Teresa Fortuna Lesław Juszczak Dorota Gałkowska Karolina Królikowska Karolina Zięba 《International Journal of Food Science & Technology》2015,50(4):934-941
The objective of this study was to determine the effect of complexation of oxidised starch with mineral elements on its physicochemical properties. Corn starch was oxidised with sodium hypochlorite and, afterwards, modified with ions of potassium, magnesium and iron. Thus, native and modified starches were analysed for: contents of mineral elements, colour parameters (L*a*b*), water binding capacity and solubility in water at temperature of 60 and 80 °C. Thermodynamic characteristics of gelatinisation by DSC, molecular weight distribution by GPC, intrinsic viscosity and pasting properties by RVA were studied. The efficiency of incorporation of metal ions into oxidised corn starch was about 30%, 20% and 20% for potassium, magnesium and iron ions, respectively. The complexation with potassium ions caused the greatest changes in the molecular weight distribution and the intrinsic viscosity of starches and viscosity of starch pastes. Only modification of starch with iron ions affected the colour parameters of the starch. Incorporation of metal ions into starch resulted also in changes in its water binding capacity and solubility in water. 相似文献
3.
The aim of this paper is to assess the closeness of agreement between results of ELISA and LC-MS/MS methods for determination of aflatoxin B1 in corn and aflatoxin M1 in milk. Samples of corn (n=100) and milk (n=250) were simultaneously analyzed using ELISA and LC-MS/MS methods, after the severe drought that affected Serbia in summer 2012 resulting in occurrence of aflatoxin B1 in corn and aflatoxin M1 in milk. Regression analysis showed higher level of agreement between aflatoxin B1 samples (R2=0.994), compared to aflatoxin M1 samples (R2=0.920). However, both techniques were satisfactory in meeting the requirements for official control purposes. 相似文献
4.
Residual stress as measured quantity in quality assurance The x‐ray method is used in the Volkswagen Automotive Group at different world‐wide locations as a standard procedure to determine residual stress. As an important measured quantity in the quality assurance residual stresses are specified in drawings of different components (e.g. gears, coil springs). Measurements are carried out during quality assurance, production, damage analyse, technical development department and design control of components from suppliers. An optimum efficiency can be achieved, if it exists a unique correlation between residual stress values and loading capacity of components, and if the processes to introduce residual stress can be optimized using residual stress measurements during the production. 相似文献
5.
浅谈门式刚架轻型钢结构厂房中抗风柱的设置 总被引:1,自引:0,他引:1
通过对抗风柱上下端的节点几种形式进行分析比较,提出建议性的节点连续方式。 相似文献
6.
7.
本文结合实际资料,对内蒙古赤峰热水镇温泉天然气的地球化学特征进行了分析和研究。结果表明:上述天然气由多种成因气体组合而成。其中He属壳源放射性成因,CO_2属有机成因,CH_4属无机合成,N_2属大气成因。 相似文献
8.
Directional solidification studies of gelatinized corn starch-water mixtures were undertaken in order to examine, in situ, the freezing behavior of this food model. The solidification rate was controlled by varying sample cell velocity as it moved from a 25°C hot stage to a -25°C cold stage. While freezing at cell velocities ≤7.5 μm/sec, starch granules were alternately pushed or entrapped by the advancing solid-liquid interface producing a segregated structure consisting of alternating high-starch and low-starch bands. At a cell velocity of 10 μm/sec, the frozen product was homogeneous. The relationship between the solid-liquid interface velocity and segregation behavior was quantified and compared to an existing model of particle-interface interactions. 相似文献
9.
建立了扭杆弹簧的波动方程,提出求解扭杆弹簧传递特性的方法,并推导出弹性波在扭杆弹簧中的传递速度,对沿弹簧传播的位移、速度、应力、应变和作用力的传递特性进行了探讨。分析了扭杆弹簧弹性单波的求解方法及波动干涉问题。推导了弹簧的波阻公式,为扭杆弹簧的波动理论建模及实际应用提供参考。 相似文献
10.
论述了初春施工这个特定的施工季节所具有的特征,从气候、施工人员、工程情况及受冻土体等方面对初春施工易出现的问题进行了分析,对施工过程及施工技术规律性问题做了细化性研究和探讨。 相似文献