全文获取类型
收费全文 | 43860篇 |
免费 | 4574篇 |
国内免费 | 2998篇 |
专业分类
电工技术 | 2459篇 |
技术理论 | 1篇 |
综合类 | 4014篇 |
化学工业 | 7279篇 |
金属工艺 | 3291篇 |
机械仪表 | 1857篇 |
建筑科学 | 2925篇 |
矿业工程 | 1943篇 |
能源动力 | 2141篇 |
轻工业 | 3548篇 |
水利工程 | 1398篇 |
石油天然气 | 2589篇 |
武器工业 | 591篇 |
无线电 | 4468篇 |
一般工业技术 | 4974篇 |
冶金工业 | 3056篇 |
原子能技术 | 1102篇 |
自动化技术 | 3796篇 |
出版年
2024年 | 178篇 |
2023年 | 599篇 |
2022年 | 1177篇 |
2021年 | 1426篇 |
2020年 | 1589篇 |
2019年 | 1334篇 |
2018年 | 1319篇 |
2017年 | 1706篇 |
2016年 | 1852篇 |
2015年 | 1872篇 |
2014年 | 2833篇 |
2013年 | 3092篇 |
2012年 | 3375篇 |
2011年 | 3463篇 |
2010年 | 2561篇 |
2009年 | 2499篇 |
2008年 | 2226篇 |
2007年 | 2778篇 |
2006年 | 2331篇 |
2005年 | 2011篇 |
2004年 | 1773篇 |
2003年 | 1505篇 |
2002年 | 1291篇 |
2001年 | 1119篇 |
2000年 | 943篇 |
1999年 | 783篇 |
1998年 | 667篇 |
1997年 | 559篇 |
1996年 | 517篇 |
1995年 | 432篇 |
1994年 | 321篇 |
1993年 | 259篇 |
1992年 | 237篇 |
1991年 | 180篇 |
1990年 | 152篇 |
1989年 | 105篇 |
1988年 | 73篇 |
1987年 | 46篇 |
1986年 | 48篇 |
1985年 | 38篇 |
1984年 | 36篇 |
1983年 | 19篇 |
1982年 | 19篇 |
1981年 | 16篇 |
1980年 | 17篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1975年 | 10篇 |
1959年 | 9篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
RLL码的计算机辅助设计 总被引:1,自引:1,他引:0
本文着重讨论计算机辅助设计RLL码的具体实现问题.该过程首先根据RLL码两个参数d,k确定一个编码率p/q,然后构造出RLL码的高阶状态转换-输出符号矩阵并求相应的近似特征向量.最后通过状态分裂和状态归并过程,即可得到一个满足d,k约束的编码输出表.其中状态转换-输出符号矩阵为实现计算机辅助设计RLL码提供了有效的数据结构,而且要优化RLL码编码器,就必须有选择地进行状态分裂. 相似文献
82.
83.
本文利用可控平均冷却速度的单向凝固实验炉测定了45号钢在不同平均冷却速度下的冷却曲线,由此得到其在凝固期间的平均冷却速度R,相应地测量了不同平均冷却速度下试样的二次枝晶臂间距S2,通过回归,得到了如下关系式:S2=727R-0.41,并将引式成功地应用于实际生产中。 相似文献
84.
A finite element formulation and the solution of a set of nonlinear coupled heat and mass transfer equations for a two-phase system with a moving evaporation interface is presented. The interface condition takes into account the moisture transfer balance at the moving boundary. The finite element results were compared with existing results for a single phase system for model validation. In the two-phase system, the movement of evaporation front has an appreciable effect on the temperature and moisture distribution inside the porous medium during drying. The effect of the nondimensional heat of vapourization parameter γ on the evaporation front, temperature and moisture distribution in porous medium was studied. The higher the value of γ, the slower is the movement of the evaporation front. The temperature decreased and the moisture content increased as the nondimensional vapourization parameter γ increased. This model has potential applications in studying the heat and mass transfer characteristics in food and biomaterials. 相似文献
85.
Drying of textile bobbins was carried out on two kinds of laboratory-scale dryers: in a cross circulation drying rig, atmospheric pressure heating air is used, while in the through circulation drying apparatus, the heating air is pressurized before the drying process takes place. In both cases, a bobbin was fitted with seven thermocouples, placed in a plane normal to the bobbin axis but at different radial distances, in order to provide temperature data during the drying process. In cross circulation drying, plots of temperature against time indicated the presence of two moving fronts, one starting from inside the bobbin, another from the outside, while in through circulation drying, similar plots showed the presence of an evaporation front, moving from inside the bobbin to the outside. In both canes, numerical models were developed to simulate the drying processes. 相似文献
86.
V. A. Roginsky T. K. Barsukova A. A. Remorova W. Bors 《Journal of the American Oil Chemists' Society》1996,73(6):777-786
The relative reactivities as well as the stoichiometric coefficients for a number of flavonoids, catechols, and—for comparison—standard
phenolic antioxidants were determined by analyzing the kinetics of oxygen consumption in organic and micellar systems, with
peroxidation initiated by lipid- and water-soluble azo initiators. The results demonstrated that the flavonoids did not behave
as classic phenolic antioxidants such as α-tocopherol, but showed only moderate chain-breaking activities. The results were
in line with other structure-activity relationship studies on the importance of the B-ring catechol structure, the 2,3-double
bond, and the 3,5-hydroxy groups. The data are discussed in view of possible explanations of the deviations flavonoids reveal
in their behavior compared with regular phenolic antioxidants. 相似文献
87.
The influence of irreversibility of finite-rate heat transfer on the performance of an absorption refrigerator is investigated using an endoreversible cycle model with continuous flow. The cooling rate is adopted as an objective function for refrigerator optimization. The maximum cooling rate and the corresponding coefficient of performance are derived. The optimal performance with respect to heat transfer areas of the refrigerator is analysed. In addition, certain significant conclusions are reached. 相似文献
88.
Cryogenic detectors with superconducting tunnel junctions can provide an energy resolution improved by at least one order of magnitude compared with standard semiconductor detectors. While the detection principle was already demonstrated many years ago, the past years were dedicated to the transition from the laboratory sample to practical detectors. Our most favored detector design gives rise to tunnel junctions with electrodes of unequal energy gaps. In such hetero tunnel junctions bias conditions can be established which cause a negative signal current. We report the experimental verification of this effect, and we discuss the yield of charge signal of cryogenic detectors based upon superconducting tunnel junctions. 相似文献
89.
本文在Knockout交换结构的基础上,探讨一种新的ATM交换结构,使其本身带有优先权控制功能,以适应不同业务对信元丢失率及时延的不同要求。这种结构既能最大限度地有效利用系统资源,又能满足不同用户对业务质量的不同要求,并能降低交换结构复杂度。 相似文献
90.
128kb/s电视电话系统中数码率缓存器的控制策略研究 总被引:2,自引:0,他引:2
本文探讨了电视电话/会议电视的H,261建议中低码率时(p=2)数码率缓存器的控制问题,提出一种既有宏观预分配又有微观分割的控制策略(简称GALS),并用测试图像序列进行了计算机模拟。将本文方法与RM8中有关策略作了比较,实验结果表明图像的主观质量有所改善。 相似文献