全文获取类型
收费全文 | 102249篇 |
免费 | 9136篇 |
国内免费 | 4624篇 |
专业分类
电工技术 | 6040篇 |
技术理论 | 12篇 |
综合类 | 6614篇 |
化学工业 | 17071篇 |
金属工艺 | 5884篇 |
机械仪表 | 6847篇 |
建筑科学 | 7808篇 |
矿业工程 | 3429篇 |
能源动力 | 3054篇 |
轻工业 | 6539篇 |
水利工程 | 1919篇 |
石油天然气 | 6610篇 |
武器工业 | 985篇 |
无线电 | 11328篇 |
一般工业技术 | 12183篇 |
冶金工业 | 5068篇 |
原子能技术 | 1255篇 |
自动化技术 | 13363篇 |
出版年
2024年 | 502篇 |
2023年 | 1838篇 |
2022年 | 3121篇 |
2021年 | 4287篇 |
2020年 | 3286篇 |
2019年 | 2817篇 |
2018年 | 3166篇 |
2017年 | 3454篇 |
2016年 | 3159篇 |
2015年 | 4187篇 |
2014年 | 5202篇 |
2013年 | 6206篇 |
2012年 | 6753篇 |
2011年 | 7300篇 |
2010年 | 6267篇 |
2009年 | 6042篇 |
2008年 | 5928篇 |
2007年 | 5512篇 |
2006年 | 5388篇 |
2005年 | 4642篇 |
2004年 | 3203篇 |
2003年 | 2969篇 |
2002年 | 2920篇 |
2001年 | 2573篇 |
2000年 | 2393篇 |
1999年 | 2559篇 |
1998年 | 1899篇 |
1997年 | 1564篇 |
1996年 | 1428篇 |
1995年 | 1264篇 |
1994年 | 999篇 |
1993年 | 775篇 |
1992年 | 601篇 |
1991年 | 435篇 |
1990年 | 357篇 |
1989年 | 241篇 |
1988年 | 234篇 |
1987年 | 133篇 |
1986年 | 120篇 |
1985年 | 61篇 |
1984年 | 52篇 |
1983年 | 47篇 |
1982年 | 37篇 |
1981年 | 22篇 |
1980年 | 17篇 |
1979年 | 14篇 |
1977年 | 7篇 |
1975年 | 5篇 |
1970年 | 6篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
介绍了军用飞机电子吊舱蒸汽压缩制冷环境控制系统的工作特点,给出了电子膨胀阀在电子吊舱地面模拟制冷系统中的初步试验研究结果。 相似文献
82.
根据大庆油田油气集输工艺设计的实践,分析了几种实用的油气集输管道敷设方式的优缺点。在对不同敷设方式的管道热耗做了较详细计算的基础上,进行了比较,提出了确定油气集输管道的最佳敷设方式:站外管道基本上采用埋地敷设;站内管道则应依据站址处的常年最高地下水位资料来确定,即在保证管道不长期受地下水浸泡的前提下,站内室外管道以埋地敷设为主,室内管道以架空与理地同时敷设为最佳;地下水位高的站内,以架空敷设最佳。 相似文献
83.
84.
OBJECTIVE: To evaluate the therapeutical mechanism of Bushen Shengxue Paste (BSSXP) on anemia. METHODS: Chronic renal failure induced anemia patients were treated with BSSXP, clinical manifestation, anemia and renal function as indicators were observed in patients. The erythropoietin (EPO) and inhibition of colony-forming unit-erythrocyte (CFU-E) in patients' serum were determined by CFU-E in vitro. RESULTS: The patients' symptoms, renal function and anemia were improved after administration with BSSXP 1-2 course. EPO in serum was slightly increased. The inhibition of CFU-E in patient's serum was significantly decreased. CONCLUSIONS: BSSXP could improve the anemia degree, its mechanism might be through clearing the inhibitor of CFU-E in serum. 相似文献
85.
For the first time, the surface metal on nonalloyed ohmic electrodes is found to significantly change the profiles of gate grooves, when resist openings are employed to monitor drain current during wet-chemical gate recess for sub-micron InAlAs/lnGaAs heterojunction field-effect transistors (HFETs). The surface metal of Ni enhances the etching rate in comparison with that in the absence of electrodes by a factor of 4 and 10, laterally and vertically, which is favorable to fabricate deep gate grooves with small side etching. The Pt surface metal, however, leads to preferential etching of InGaAs over InAlAs, which can be useful to realize large side etching. The existence of an electrochemistry-related etching component, which arises when the ohmic electrodes are present during recess etching, is considered to be responsible for these behaviors 相似文献
86.
复杂目标近场电磁散射的可视化计算方法 总被引:9,自引:1,他引:8
首次介绍了复杂目标近场散射计算的可视化方法。采用非均匀有理B样条曲面(NURBS)精确构造任意形状散射体,结合几何体近场透视变换和Z-Buffer技术实现了基于Windows平台的近场散射计算。提出广义雷达散射截面的概念并给出的若干算例。该方法充分利用了计算机3D图形设备的几何运算能力,运算速度快,严谨高,可扩展性好。 相似文献
87.
Q Hu M Trevisan Y Xu W Dong SA Berger SD Lyman MD Minden 《Canadian Metallurgical Quarterly》1995,95(6):2530-2538
The growth of human leukemic cells in culture and in vivo is dependent upon the presence of hematopoietic growth factors. Most populations of human leukemic acute myeloblastic leukemia (AML) cells express c-Kit on their surface and respond to Kit ligand (KL) in culture. To determine if this interaction was of potential significance in vivo we used a mouse model system. 32D cells, a murine IL-3-dependent myeloid cell line, were rendered KL responsive by transfection of the murine c-Kit. After injection of 32D or 32D-Kit cells into syngeneic hosts, animals bearing 32D-Kit cells, but not 32D cells, became moribund and were killed. These animals had circulating leukemic blast cells, infiltration of bone marrow, spleen, brain, liver, lung, and kidney. Cells recovered from some of the animals continued to be dependent upon IL-3 or KL for growth while in other cases the cells were factor independent. This model illustrates that the constitutive expression of c-Kit enhances the leukemic potential of 32D cells. The model will be useful for studying the progression of leukemia in vivo and testing whether interruption of the interaction of Kit and KL can affect the growth of leukemic cells. 相似文献
88.
Kwang Soo Lee In Soo Park & Dong Sun Lee 《International Journal of Food Science & Technology》1996,31(1):7-13
The aim of this study was to design a modified atmosphere package for a mixed vegetable salad consisting of 75 g of cut carrot, 55 g of cut cucumber, 20 g of sliced garlic and 50 g of whole green pepper. Respiration data of all the components were combined with film permeability data to predict package atmospheres and design optimal packages for experimental testing for improved shelf-life of the produce. The optimal package avoided minimum O2 and maximum CO2 tolerance limits, and chilling injury temperatures for any component. A pouch form package made of 27 mm low density polyethylene developed a modified atmosphere of 2.0–2.1% O2 and 5.5–5.7% CO2 , which was beneficial for all components and provided better quality retention than other test packages. 相似文献
89.
90.
机械化栽培甜菜平均单产33.18吨/公顷,比人工栽培生产田提高52.03%;平均含糖15.5度,比人工栽培生产田提高1.09度;平均技术效果138.2元/公顷;经济效果1588.8元/公顷;创造社会经济效益24.47万元。 相似文献