全文获取类型
收费全文 | 82040篇 |
免费 | 11340篇 |
国内免费 | 5806篇 |
专业分类
电工技术 | 14004篇 |
技术理论 | 2篇 |
综合类 | 7562篇 |
化学工业 | 14669篇 |
金属工艺 | 5707篇 |
机械仪表 | 3588篇 |
建筑科学 | 4523篇 |
矿业工程 | 2071篇 |
能源动力 | 3385篇 |
轻工业 | 3887篇 |
水利工程 | 1960篇 |
石油天然气 | 4461篇 |
武器工业 | 838篇 |
无线电 | 10334篇 |
一般工业技术 | 9247篇 |
冶金工业 | 4138篇 |
原子能技术 | 1315篇 |
自动化技术 | 7495篇 |
出版年
2024年 | 440篇 |
2023年 | 1444篇 |
2022年 | 2400篇 |
2021年 | 2952篇 |
2020年 | 3279篇 |
2019年 | 2961篇 |
2018年 | 2764篇 |
2017年 | 3335篇 |
2016年 | 3364篇 |
2015年 | 3472篇 |
2014年 | 4938篇 |
2013年 | 5394篇 |
2012年 | 5778篇 |
2011年 | 5887篇 |
2010年 | 4224篇 |
2009年 | 4648篇 |
2008年 | 4427篇 |
2007年 | 5179篇 |
2006年 | 4822篇 |
2005年 | 3924篇 |
2004年 | 3393篇 |
2003年 | 3132篇 |
2002年 | 2641篇 |
2001年 | 2266篇 |
2000年 | 2023篇 |
1999年 | 1656篇 |
1998年 | 1422篇 |
1997年 | 1198篇 |
1996年 | 976篇 |
1995年 | 908篇 |
1994年 | 847篇 |
1993年 | 570篇 |
1992年 | 524篇 |
1991年 | 421篇 |
1990年 | 369篇 |
1989年 | 334篇 |
1988年 | 192篇 |
1987年 | 131篇 |
1986年 | 105篇 |
1985年 | 90篇 |
1984年 | 78篇 |
1983年 | 51篇 |
1982年 | 61篇 |
1981年 | 31篇 |
1980年 | 38篇 |
1979年 | 12篇 |
1977年 | 11篇 |
1975年 | 9篇 |
1959年 | 11篇 |
1951年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
121.
钨合金圆筒爆破试验破片分布的统计分析 总被引:1,自引:1,他引:0
采用圆筒爆破试验方法研究了易碎型钨合金的破片分布特征,并与93W合金的结果进行了对比.对破片的数量和质量分布特征进行了统计分析,发现易碎型钨合金的破片率明显高于93W合金,而且破片的均匀性也明显好于93W合金,但易碎钨合金的破片回收率低于93W合金,而且受装药量的影响较大. 相似文献
122.
V. Psota I. Boha
enko J. Hartmann M. Budinsk J. Chmelík 《Journal of the Institute of Brewing》2002,108(2):200-203
A newly developed method GFFF (Gravitational Field‐Flow Fractionation) and the well known method LALLS (Low Angle Laser Light Scattering) were used to assess starch granule size distribution of ten varieties of spring barley. As a distribution criterion, the ratio of starch granule content larger than 8 μm (type A) and smaller than 8 μm (type B) was chosen. Both methods divided the observed set in a similar way. Varieties Akcent, Forum and Atribut formed a variety set with the highest ratio of large and small starch granules. Varieties Scarlet and Kompakt had intermediate ratios. The remaining five varieties Amulet, Novum, Olbram, Tolar and Krona had the lowest ratios of large and small starch granules. Statistical analysis showed that there was a highly significant correlation between the GFFF and LALLS methods. 相似文献
123.
多输入单输出逆高斯分布流域汇流模型 总被引:1,自引:0,他引:1
本文将逆高斯分布应用于由水库和区间组成的复杂的流域汇流系统,并建立了多输入单输出逆高斯单位线模型。讨论了模型参数的估计方法,并对沾益流域的雨洪资料进行了实例分析。 相似文献
124.
关于广义函数δ(x)的讨论 总被引:1,自引:0,他引:1
沈永朝 《电气电子教学学报》2002,24(1):28-31
本文应用《电气子教学学报》之邀约而写,旨在针对一些读者对该韩过去刊出的有关广义函数δ(x)的文章中的质疑,从数学角度提供一些有助于正确认识、处理和运用广义函数的辅助材料。 相似文献
125.
单相开关磁阻电机及其控制 总被引:1,自引:0,他引:1
通过分析一种可以实现自启动的新型结构的永磁单相开关磁阻电机的基本工作原理,提出了一种性价比较高的控制方案,通过实验得出了结论。 相似文献
126.
本文采用粉末冶金法制备了不同成分的PSZ/Mo复合材料。并对其密度、弹性模量和热膨胀系数进行了测量和分析 ,用XRD进行了物相分析。实验结果表明 :纳米氧化锆的烧结性能比金属钼好 ;弹性模量估算选用简单混合法则进行计算时应进行修正 ;钼和氧化锆在烧结时不发生化学反应。通过热压PSZ/Mo功能梯度材料的断口扫描分析发现 :虽然金属钼和纳米氧化锆具有一定增韧作用 ,但材料断裂方式仍以脆性断裂为主 相似文献
127.
128.
A novel series of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] (p(NIPAM‐co‐EMA)) microgels was prepared by the surfactant‐free radical polymerization of N‐isopropylacrylamide (NIPAM) with ethyl methacrylate (EMA). The shape, size dispersity and volume‐phase transition behavior of the microgels were investigated by transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC). The transmission electron micrographs and DLS results showed that microgels with narrow distributions were prepared. It was shown from UV–Vis, DLS and DSC measurements that the volume‐phase transition temperature (VPTT) of the p(NIPAM‐co‐EMA) microgels decreased with increasing incorporation of EMA, but the temperature‐sensitivity was impaired when more EMA was incorporated, causing the volume‐phase transition of the microgels to become more continuous. It is noteworthy that incorporation of moderate amounts of EMA could not only lower the VPTT but also enhance the temperature‐sensitivity of the microgels. The reason for this phenomenon could be attributed to changes in the complicated interactions between the various molecules. Copyright © 2004 Society of Chemical Industry 相似文献
129.
The miscibility and phase behavior of ternary blends containing dimethylpolycarbonate (DMPC), tetramethylpolycarbonate (TMPC) and poly[styrene‐co‐(methyl methacrylate)] copolymer (SMMA) have been explored. Ternary blends containing polystyrene (PS) instead of SMMA were also examined. Blends of DMPC with SMMA copolymers (or PS) did not form miscible blends regardless of methyl methacrylate (MMA) content in copolymers. However, DMPC blends with SMMA (or PS) blends become miscible by adding TMPC. The miscible region of ternary blends is compared with the previously determined miscibility region of binary blends having the same chemical components and compositions. The region where the ternary blends are miscible is much narrower than that of binary blends. Based on lattice fluid theory, the observed phase behavior of ternary blends was analyzed. Even though the term representing the Gibbs free energy change of mixing for certain ternary blends had a negative value, blends were immiscible. It was revealed that a negative value of the Gibbs free energy change of mixing was not a sufficient condition for miscible ternary blends because of the asymmetry in the binary interactions involved in ternary blends. Copyright © 2004 Society of Chemical Industry 相似文献
130.
The d.c. electrical conductivity of sodium vanadate, rubidium vanadate, cesium vanadate and their solid solutions sodium-rubidium
vanadate and sodium-cesium vanadate were studied by a two-probe method in the temperature range covering their transition
points. The electrical conductivity shows sharp change at the phase transition temperature of these materials. In NaVO3, RbVO3 and CsVO3, increase in d.c. conductivity is observed in the ferroelectric region while nonlinearities are observed above transition
temperatures. In solid solutions, the activation energy in the paraelectric state is higher than that in the ferroelectric
state and depends upon sodium concentration. 相似文献