全文获取类型
收费全文 | 848256篇 |
免费 | 128458篇 |
国内免费 | 86707篇 |
专业分类
电工技术 | 78124篇 |
技术理论 | 14篇 |
综合类 | 85178篇 |
化学工业 | 114038篇 |
金属工艺 | 66077篇 |
机械仪表 | 53927篇 |
建筑科学 | 64396篇 |
矿业工程 | 37728篇 |
能源动力 | 25165篇 |
轻工业 | 81985篇 |
水利工程 | 26717篇 |
石油天然气 | 38324篇 |
武器工业 | 12395篇 |
无线电 | 100252篇 |
一般工业技术 | 89033篇 |
冶金工业 | 35280篇 |
原子能技术 | 11603篇 |
自动化技术 | 143185篇 |
出版年
2024年 | 5262篇 |
2023年 | 13986篇 |
2022年 | 28970篇 |
2021年 | 37111篇 |
2020年 | 30061篇 |
2019年 | 30170篇 |
2018年 | 32510篇 |
2017年 | 36485篇 |
2016年 | 34148篇 |
2015年 | 43770篇 |
2014年 | 51136篇 |
2013年 | 58300篇 |
2012年 | 67844篇 |
2011年 | 68511篇 |
2010年 | 63796篇 |
2009年 | 59338篇 |
2008年 | 58711篇 |
2007年 | 57074篇 |
2006年 | 50232篇 |
2005年 | 42131篇 |
2004年 | 33404篇 |
2003年 | 24223篇 |
2002年 | 22539篇 |
2001年 | 20380篇 |
2000年 | 17801篇 |
1999年 | 12521篇 |
1998年 | 9458篇 |
1997年 | 7998篇 |
1996年 | 7372篇 |
1995年 | 6812篇 |
1994年 | 5577篇 |
1993年 | 4862篇 |
1992年 | 4296篇 |
1991年 | 3131篇 |
1990年 | 2536篇 |
1989年 | 2354篇 |
1988年 | 1762篇 |
1987年 | 852篇 |
1986年 | 708篇 |
1985年 | 529篇 |
1984年 | 379篇 |
1983年 | 320篇 |
1982年 | 331篇 |
1981年 | 355篇 |
1980年 | 380篇 |
1979年 | 262篇 |
1976年 | 304篇 |
1975年 | 248篇 |
1972年 | 258篇 |
1960年 | 207篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
111.
全球炼化工程总承包市场呈现出垄断竞争型特征,欧美和日韩国际工程公司由于技术和报价竞争力较强,一直占据本行业高端市场,中国炼化工程企业尚有差距.文章综合考虑投标报价阶段竞争者分析路径,提出了随机型和不完全信息静态博弈综合集成分析的投标报价最优决策模型,并以中东海湾地区某炼化工程总承包项目为例,进行多维度的实证分析,提出模型的有效性和可行性,为中国炼化工程企业"走出去"高质量发展提供有益的决策支持和信息参考. 相似文献
112.
113.
Myelodysplastic syndromes (MDS) are highly heterogeneous myeloid neoplasms, and a large number of
patients are difficult to diagnose and classify by blood and bone marrow examination. As a surface marker of
granulocyte, studies have shown CD10 can be used to define the degree of granulocyte maturation in MDS patients.
However, whether it can be used for differential diagnosis of MDS and other hematological diseases remains
inconclusive. To explore the value of CD10 for differential diagnosis of MDS, 60 newly diagnosed MDS, 20 aplastic
anemia (AA) patients, and 35 iron-deficient anemia (IDA) patients were selected for this study. Bone marrow (BM)
specimens were processed for surface marker analysis and labeled with pre-conjugated monoclonal antibodies. Stained
cells were detected by flow cytometry. Our results indicated that CD10-positive granulocytes were significantly
decreased in BM of MDS patients than AA and IDA patients, and the level of CD10-positive mature granulocytes was
not associated with the clinical stages of malignancy. Receiver operating characteristic (ROC) areas under the curve
(AUC) of CD10-positive granulocytes was 0.86 and 0.85, respectively, in MDS patients than the IDA group and AA
group with good specificity and sensitivity. Further, CD10-positive granulocytes were increased after effective
treatment. In conclusion, we found the decrease in CD10-positive granulocytes has a differential diagnostic value of MDS. 相似文献
114.
Amino acid modified polyaspartic acids were evaluated as calcium-scale inhibitors. Feasibility of scale inhibition experiments was analyzed by molecular dynamics simulation and Gaussian optimization, and the scale inhibition mechanism was theoretically analyzed. Scale inhibition performance was studied by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, static scale inhibition experiments, and electrochemical performance testing, which provided an experimental basis for the molecular dynamics simulation. The experimental results showed that Arg-SA-PASP has better scale inhibition and corrosion inhibition performance than His-SA-PASP. The scale inhibition effect increased with increasing concentration. Electrochemical tests indicated that Arg-SA-PASP is an excellent scale and corrosion inhibitor. 相似文献
115.
为了建立适用于书画打印宣纸印刷质量的预测模型,本研究测量了14种书画打印宣纸的粗糙度、白度、不透明度、定量、光泽度和针对宣纸特别设定的帘纹深浅以及帘纹疏密度等表面物理参量,并在相同条件下,使用喷墨打印设备输出并测量印品色度值,利用总变差模型构建去除帘纹色差的测定方法,得到与人眼视觉特征相符的色差。运用GRNN广义回归神经网络结合书画打印宣纸表面物理参量与宣纸去帘纹后的色差值,建立预测模型。结果表明,该模型能够在仅测量书画打印宣纸表面物理参量的情况下,便能较为准确地预测书画打印宣纸印刷质量,为书画打印宣纸印刷前的选纸工作提供指导依据。 相似文献
116.
117.
118.
Fluorescence‐Activated Cell Sorters: Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter (Small 40/2018) 下载免费PDF全文
119.
Because of heat amount is different from peripheral to central of friction welding interface, which is leaded to vary the characterizations along that interface. Current study, respectively, focused on the effect of different friction pressure on micro-structural and mechanical properties of that friction welding joint interface. Presently, these friction pressures are 110, 130, 150 and 170 MPa while kept all other conditions constant. The effects of different friction pressure on welding interface characterization were investigated by EDX, SEM, tensile, compression, impact and hardness tests. The tensile tests carried out on the standardized test piece with diameter 6 mm and 8 mm, thus, compression tests were extracted from the positions of 0°, 45° 90° with test specimen of 4 mm diameter and 6.5 mm length at weld center. Whereas, the impact test pieces were picked up in two positions, the first one is symmetrical, which it obtained to the respect of the rotation axis and the interface, on the other hand, the second one is non-symmetrical with the axis of rotation and symmetrical to the interface, for making the notch head coincide with the center of the welded joint, The obtained results showed that with reducing of friction pressure will present lack of bonding increasing from peripheral toward the welding center, which will responsible on reducing of the mechanical properties such as tensile, compression and impact strength. 相似文献
120.
目的研究蛋类礼盒包装结构的缓冲性能。方法以蛋类尺寸为基础,建立可发性聚乙烯(expandable polyethylene. EPE)缓冲单元结构和组合结构,进行静态仿真分析和实验验证,比较结构在形状、叠合层数、组合形式等参数变化时的载荷与位移。结果结构层数变化相同时,单元结构的极限载荷从143N增加到236 N,组合结构的极限载荷从224 N增加到476 N,均呈近线性增长。结论蛋类礼盒包装中,组合结构的承载能力优于单元结构,通过单元结构的组合,可满足不同蛋类的包装要求。 相似文献