全文获取类型
收费全文 | 28655篇 |
免费 | 2341篇 |
国内免费 | 1163篇 |
专业分类
电工技术 | 2117篇 |
技术理论 | 1篇 |
综合类 | 1498篇 |
化学工业 | 7984篇 |
金属工艺 | 1309篇 |
机械仪表 | 628篇 |
建筑科学 | 1420篇 |
矿业工程 | 648篇 |
能源动力 | 1945篇 |
轻工业 | 2120篇 |
水利工程 | 757篇 |
石油天然气 | 925篇 |
武器工业 | 108篇 |
无线电 | 1619篇 |
一般工业技术 | 5318篇 |
冶金工业 | 1969篇 |
原子能技术 | 307篇 |
自动化技术 | 1486篇 |
出版年
2024年 | 110篇 |
2023年 | 747篇 |
2022年 | 865篇 |
2021年 | 1069篇 |
2020年 | 1048篇 |
2019年 | 955篇 |
2018年 | 858篇 |
2017年 | 996篇 |
2016年 | 970篇 |
2015年 | 868篇 |
2014年 | 1584篇 |
2013年 | 1766篇 |
2012年 | 1675篇 |
2011年 | 2301篇 |
2010年 | 1531篇 |
2009年 | 1657篇 |
2008年 | 1390篇 |
2007年 | 1636篇 |
2006年 | 1532篇 |
2005年 | 1281篇 |
2004年 | 1113篇 |
2003年 | 1001篇 |
2002年 | 821篇 |
2001年 | 665篇 |
2000年 | 576篇 |
1999年 | 485篇 |
1998年 | 438篇 |
1997年 | 357篇 |
1996年 | 315篇 |
1995年 | 288篇 |
1994年 | 217篇 |
1993年 | 186篇 |
1992年 | 160篇 |
1991年 | 127篇 |
1990年 | 83篇 |
1989年 | 75篇 |
1988年 | 73篇 |
1987年 | 40篇 |
1986年 | 43篇 |
1985年 | 47篇 |
1984年 | 45篇 |
1983年 | 36篇 |
1982年 | 23篇 |
1981年 | 22篇 |
1980年 | 22篇 |
1979年 | 10篇 |
1977年 | 11篇 |
1976年 | 6篇 |
1975年 | 9篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
K-S. Park S-H. Park Y-K. Sun K-S. Nahm Y-S. Lee M. Yoshio 《Journal of Applied Electrochemistry》2002,32(11):1229-1233
The structural and electrochemical properties of LiNiO2 powders were investigated as a function of the oxygen flow rate employed in the preparation of lithium nickel oxide. It was found that oxygen played an important role in the synthesis of highly crystallized LiNiO2(R3¯m). In the crystallization process of LiNiO2, a deficiency of oxygen in the calcination reactor induced the formation of impurities and cubic rock-salt structure (Fm3m) in LiNiO2 powders. For LiNiO2 prepared at higher oxygen flow rates, the electrode delivered high discharge capacities with relatively good retention rates. But very low electrode capacity was obtained from LiNiO2 prepared at lower oxygen flow rates. 相似文献
92.
10000m3/h制氧机板式换热器损坏修复后,热端跑冷严重,氧气取出量不足,制氧机工况恶化,通过分析找出了原因是因某单元氧通道堵塞,并采取了处理措施。 相似文献
93.
Thermodynamic analysis of solar photovoltaic cell systems 总被引:1,自引:0,他引:1
Ahmet Duran Sahin Ibrahim Dincer Marc A. Rosen 《Solar Energy Materials & Solar Cells》2007,91(2-3):153-159
The thermodynamic characteristics of solar photovoltaic (PV) cells are investigated from a perspective based on exergy. A new efficiency is developed that is useful in studying PV performance and possible improvements. Exergy analysis is applied to a PV system and its components, and exergy flows, losses and efficiencies are evaluated. Energy efficiency is seen to vary between 7% and 12% during the day. In contrast, exergy efficiencies, which incorporate the second law of thermodynamics and account for solar irradiation exergy values, are lower for electricity generation using the considered PV system, ranging from 2% to 8%. Values of “fill factors” are determined for the system and observed to be similar to values of exergy efficiency. 相似文献
94.
对云母粒子化学镀镍及以LDPE为基材,镀镍云母粒子为填料制备的导电复合材料进行研究。认为此种导电复合材料只有质量轻、强度大及良好的导电等性能。 相似文献
95.
甄汉生 《真空科学与技术学报》1993,(2)
微波电子回旋共振等离子体是淀积薄膜、微细加工和材料表面改性的一种重要手段。由于这种等离子体电离水平高,化学活性好,可以用来实现基片上薄膜的室温化学气相淀积和反应离子刻蚀,因此对于微电子学、光电子学和薄膜传感器件的发展,这种等离子体会具有重要的意义。此外,采用微波电子回旋共振等离子体原理,没有灯丝的离子源可以提高离子源的使用寿命,可以增加离子束的束流密度。可以确信,微波电子回旋共振等离子体的发展,将把离子源技术提高到一个新的水平。显然,这必将对材料表面改性工艺,包括离子注入掺杂等工艺的发展发挥作用。自从1985年以来,为了得到大容积等离子体而发展了微波电子回旋共振多磁极等离子体,这些技术在薄膜技术、微细加工以及材料表面改性中的应用前景是乐观的。我们将在本文中,介绍微波电子回旋共振等离子体的原理及其应用。 相似文献
96.
The existing geochemical diversity of clay deposits consists the underlying assumption for the determination of provenance of archaeological ceramics on the basis of their chemical composition. This assumption was tested on Quarternary red clayey alluviums from Central and Eastern Crete (Greece), an area rich in archaeological pottery and very popular for ceramics provenance studies. This type of clay has been used for pottery production on the island since the antiquity and it is still in use by traditional workshops. Altogether, 17 samples of clayey raw materials were collected from 7 different locations in Central and Eastern Crete, and characterised by chemistry, mineralogy and petrography. The study was focussed on the internal variability within deposits and the diversity among different deposits.It was possible to distinguish all seven deposits from each other on the basis of their chemical composition, taking into account the available mineralogical and petrographical information, although some deposits presented compositional relations. Compared to Neogene clay deposits in the same area, the variability among the examined red clayey deposits was clearly higher and exceeded by far the intra-deposit variability. 相似文献
97.
The methodology of response reactions (RERs) introduced earlier from thermodynamic and kinetic considerations is used in this work to develop a new algorithm for the classification and enumeration of unique/direct reaction routes (RRs) and overall reactions (ORs). According to the RERs approach, a unique set of both RRs and ORs may be generated starting from any conceivable set of linearly independent RRs and ORs. In particular, the direct ORs may be most conveniently enumerated starting from the formula matrix of the terminal species (reactants and products), i.e., without any relation to the elementary reactions comprising the detailed mechanism. Depending on the type of ORs produced by the RRs one can distinguish between two distinct types of direct RRs. Namely, one option is to define a direct RR by specifying the intermediate species that need to be eliminated. This type of RR is referred to as Milner RRs. The other option is to require the direct RRs to produce RERs, thus resulting in RRs referred to as Happel-Sellers RRs. 相似文献
98.
99.
《稀有金属材料与工程》2006,23(1):32-34
叙述了用红外吸收法对钛及钛合金中氧和氢联合测定的方法,取得了测定的最佳条件。连续测定6次的相对标准偏差在10%以下,作加标回收试验的回收率为95.6%~103.9%。分析时间在3min以内,可应用于日常分析,结果满意。 相似文献
100.