全文获取类型
收费全文 | 4273篇 |
免费 | 129篇 |
国内免费 | 106篇 |
专业分类
电工技术 | 143篇 |
综合类 | 238篇 |
化学工业 | 1488篇 |
金属工艺 | 114篇 |
机械仪表 | 259篇 |
建筑科学 | 361篇 |
矿业工程 | 84篇 |
能源动力 | 171篇 |
轻工业 | 169篇 |
水利工程 | 56篇 |
石油天然气 | 84篇 |
武器工业 | 11篇 |
无线电 | 238篇 |
一般工业技术 | 273篇 |
冶金工业 | 99篇 |
原子能技术 | 48篇 |
自动化技术 | 672篇 |
出版年
2023年 | 22篇 |
2022年 | 26篇 |
2021年 | 23篇 |
2020年 | 28篇 |
2019年 | 32篇 |
2018年 | 29篇 |
2017年 | 25篇 |
2016年 | 48篇 |
2015年 | 49篇 |
2014年 | 93篇 |
2013年 | 100篇 |
2012年 | 116篇 |
2011年 | 155篇 |
2010年 | 107篇 |
2009年 | 127篇 |
2008年 | 121篇 |
2007年 | 167篇 |
2006年 | 142篇 |
2005年 | 143篇 |
2004年 | 125篇 |
2003年 | 129篇 |
2002年 | 114篇 |
2001年 | 75篇 |
2000年 | 92篇 |
1999年 | 76篇 |
1998年 | 83篇 |
1997年 | 65篇 |
1996年 | 62篇 |
1995年 | 108篇 |
1994年 | 74篇 |
1993年 | 25篇 |
1992年 | 26篇 |
1991年 | 20篇 |
1990年 | 14篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1986年 | 9篇 |
1985年 | 161篇 |
1984年 | 291篇 |
1983年 | 346篇 |
1982年 | 264篇 |
1981年 | 347篇 |
1980年 | 155篇 |
1979年 | 67篇 |
1978年 | 81篇 |
1977年 | 38篇 |
1976年 | 19篇 |
1975年 | 34篇 |
1974年 | 15篇 |
1973年 | 7篇 |
排序方式: 共有4508条查询结果,搜索用时 359 毫秒
1.
Xiao-Mei Sha Li-Jun Zhang Wen-Mei Chen Guang-Yao Wang Jin-Lin Li Zi-Zi Hu Zong-Cai Tu 《International Journal of Food Science & Technology》2022,57(3):1573-1586
Thermal action in extraction process had effects on characteristic tryptic peptides identification and gelling properties of porcine gelatin. SDS-PAGE, HPLC-LTQ/Orbitrap high-resolution mass spectrometry, texture analyser and rheometer were used to evaluate collagen depolymerisation degree, characteristic tryptic peptides and gelling properties of gelatins prepared in various thermal actions. Results showed that with increasing temperature and time, depolymerisation degree enlarged, while gel strength, gelling and melting temperature decreased. Mass spectra showed that 47 and 49 common characteristic tryptic peptides were identified in gelatins extracted at 50 °C and 100 °C with various times, respectively. Moreover, 34 common characteristic tryptic peptides were identified in all gelatin samples. Further comparison between this work and our previous investigations yielded 20 common characteristic tryptic peptides, which stably exist in various thermal actions. These common characteristic tryptic peptides may be very helpful for the accurate authentication of porcine gelatin. 相似文献
2.
焊膏工艺性要求及性能检测方法 总被引:9,自引:0,他引:9
焊膏是SMT工艺中不可缺少的钎焊材料,广泛应用于再流焊中;它是由一定的合金粉末和助焊剂均匀混合而成的膏状体。主要对SMT中焊膏的组成及焊膏性能检测方法进行了简要分析。 相似文献
3.
用保角变换法对共面波导金属厚度效应进行了理论分析,编制了相应的计算机程序,给出了数值解,并对此进行了多元曲线拟合,导出了考虑金属厚度后的形状比k、有效介电常数、特征阻抗、损耗的闭定表达式。用此修正表达式求得特征阻抗及损耗的数值解,并与K.C.格普塔的修正值及实验测量值进行了详细比较,结果表明此修正公式与实验值相符较好。 相似文献
4.
Sung D. Kwon Sung J. Song Dong H. Bae Young Z. Lee 《Journal of Mechanical Science and Technology》2002,16(9):1084-1092
The frequency dependency of Rayleigh surface wave is investigated indirectly by measuring the angular dependency of the backward
radiation of the incident ultrasonic wave in two kinds of degraded specimens by scuffing or corrosion. Then, the frequency
dependency is compared with the residual stress distribution or the corrosion-fatigue characteristics for the scuffed or corroded
specimens, respectively. The width of the backward radiation profile increases with the increase of the variation in residual
stress distribution for the scuffed specimens. In the corroded specimens, the profile width decreases with the increase of
the effective aging layer thickness and is inversely proportional to the exponent, m, in the Paris’ law that can predict the
crack size increase due to fatigue. The result observed in this study demonstrates high potential of backward radiated ultrasound
as a tool for nondestructive evaluation of subsurface gradient of material degradation generated by scuffing or corrosion. 相似文献
5.
The void fraction in a three-component randomly packed bed was calculated from the authors' model, and the calculated values were compared with published experimental data for spherical and irregularly shaped particles and with results from computer simulations. Results from the model were in good agreement with simulated and published experimental data. 相似文献
6.
漏斗贮料压力计算公式 总被引:2,自引:0,他引:2
本文从平衡条件和常系数假定出发,建立贮料压力微分方程,导出了正倒锥漏斗、倒锥漏斗贮料压力计算公式。文中说明,圆柱仓筒贮料压力微分方程为上述方程的特殊情形。本文成果可供筒仓工程设计使用,还可供确定斗口给料机贮料荷载参考。 相似文献
7.
An efficient method is described for sensitivity analysis of nonlinear initial value problems, which may include algebraic equations as well as ordinary differential equations.The linearity of the sensitivity equations is utilized to solve them directly via the local Jacobian of the state equations. The method is implemented with the implicit integrator DASSL and is demonstrated on a stiff industrial reaction model. 相似文献
8.
K W Brown K C Donnelly J C Thomas P Davol B R Scott 《The Science of the total environment》1985,41(2):173-186
A chemical and biological testing protocol was employed to evaluate the mutagenic potential of the organic compounds extracted from three agricultural soils. The analytical procedures used included bioassays with Salmonella typhimurium and Aspergillus nidulans for the detection of point mutations and a gas chromatography/mass spectrometry/computer system to identify major organic constituents. The extracts of all three soils exhibited mutagenic response in the bioassays. At a dose level of 1000 micrograms per plate, the organic extract of the Bastrop clay induced 434 net revertants; while at the same dose level the Norwood sandy clay and the Sassafrass sandy loam induced 35 and 178 net revertants, respectively, in the Salmonella assay with metabolic activation. In the Aspergillus assay, the extract of the Norwood and Bastrop soils induced a positive response without metabolic activation; this effect was reduced or eliminated in the presence of metabolic activation. Chemical analysis identified a variety of initiators, promotors, inhibitors, and cocarcinogens; however, there were no mutagenic compounds identified in any of the soil extracts. The results of this combined testing protocol indicate that the agricultural soils tested had an inherent level of mutagenic activity, which was not detected by GC/MS analysis alone, and this activity may be related to the past history of agricultural practices, including biocide applications, fertilization, and cultivation. 相似文献
9.
随着设备高速化的日益发展,传统的螺杆设计方法及相应的供送特性评价体系已显落后。参照蜗型凸轮动力学性能的评价方法,建立了高速供送螺杆的动态性能评价体系,为高速化供送螺杆的设计提供了性能参照指标。 相似文献
10.
部分种子成分的特征X射线在等效生物材料中衰减的测定 总被引:6,自引:5,他引:1
用Si(Li)探测器实现了Na、Mg、S、Cl的特征X射线在有机膜中的相对衰减以及与O、K元素的特征X射线能量相当的X射线或轫致辐射在有机膜中的相对衰减,分别得出了它们减的数学描述,并把实验得到不同能量的X射线在有机膜中的质量吸收系数与Berkeley的OCG软件计算出的结果相比,相关都小于30%。 相似文献