全文获取类型
收费全文 | 641772篇 |
免费 | 72480篇 |
国内免费 | 48947篇 |
专业分类
电工技术 | 55478篇 |
技术理论 | 6篇 |
综合类 | 65930篇 |
化学工业 | 83462篇 |
金属工艺 | 43256篇 |
机械仪表 | 45626篇 |
建筑科学 | 50225篇 |
矿业工程 | 26396篇 |
能源动力 | 17328篇 |
轻工业 | 63549篇 |
水利工程 | 20357篇 |
石油天然气 | 24657篇 |
武器工业 | 9531篇 |
无线电 | 70432篇 |
一般工业技术 | 57107篇 |
冶金工业 | 24928篇 |
原子能技术 | 10068篇 |
自动化技术 | 94863篇 |
出版年
2024年 | 3321篇 |
2023年 | 9829篇 |
2022年 | 23298篇 |
2021年 | 30643篇 |
2020年 | 22095篇 |
2019年 | 15836篇 |
2018年 | 16796篇 |
2017年 | 19303篇 |
2016年 | 17569篇 |
2015年 | 28319篇 |
2014年 | 35350篇 |
2013年 | 41895篇 |
2012年 | 52338篇 |
2011年 | 54949篇 |
2010年 | 52037篇 |
2009年 | 49939篇 |
2008年 | 50811篇 |
2007年 | 49331篇 |
2006年 | 43920篇 |
2005年 | 35263篇 |
2004年 | 25674篇 |
2003年 | 17656篇 |
2002年 | 16280篇 |
2001年 | 14744篇 |
2000年 | 12112篇 |
1999年 | 6240篇 |
1998年 | 3252篇 |
1997年 | 2619篇 |
1996年 | 2275篇 |
1995年 | 1869篇 |
1994年 | 1538篇 |
1993年 | 1212篇 |
1992年 | 936篇 |
1991年 | 752篇 |
1990年 | 580篇 |
1989年 | 559篇 |
1988年 | 378篇 |
1987年 | 278篇 |
1986年 | 241篇 |
1985年 | 153篇 |
1984年 | 107篇 |
1983年 | 102篇 |
1982年 | 93篇 |
1981年 | 123篇 |
1980年 | 188篇 |
1979年 | 103篇 |
1977年 | 14篇 |
1976年 | 17篇 |
1959年 | 110篇 |
1951年 | 104篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
992.
从恒定、渐变流河段能量方程式中推导出以高程与河道断面特性平均积分曲线图解河道水面线的方法,并通过某河段水面线计算实例说明了此方法的计算图解步骤。对于同一河道,由于高程与河道断面特性平均积分曲线不变。故曲线可重复利用。因此,对进行多种设计标准的水面线计算可很方便地直接从曲线图上得出水面线结果。 相似文献
993.
Shihong XU Pengshou XU Mingrong JI Xianming LIU Maosheng MA Jingsheng ZHU Yuheng ZHANG Structure Research Laboratory University of Science Technology of China Hefei ChinaZhenjia XU Institute of Semiconductor Academia Sinica Beijing China 《材料科学技术学报》1993,9(6):437-440
The alkali-metal Na adsorption on Si(100)2×1 surface and its promoted oxidation and Si oxidegrowth have been investigated by means of thermal desorption,work function,Auger electronspectroscopy and photoemission electron spectroscopy.The experimental data showed that therewas a new state,interface electron state,near the Fermi level after the deposition of Na atoms.It wasfound that the presence of Na always caused an increase of the oxygen initial uptake whereas thepromotion of Si oxide growth was observed only at the coverage of Na greater than 0.5 ML.A newmechanism of Na-promoted Si oxide growth is suggested in this paper. 相似文献
994.
湿敏半导体材料电导率计算方法的研究 总被引:3,自引:0,他引:3
结合修正了的耗尽层理论和多孔湿敏半导体的特点,本文提出了一个简单的物理模型作为n型湿敏半导体特征的一级近似。描述了多孔湿敏半导体的导电机理,并给出了湿度与宏观电导率的关系。 相似文献
995.
996.
Z Ma S Ramanadham K Kempe Z Hu J Ladenson J Turk 《Canadian Metallurgical Quarterly》1996,1308(2):151-163
We prepared polymers having a phospholipid polar group, poly [omega-methacryloyloxyalkyl phosphorylcholine (MAPC)-co-n-butyl methacrylate(BMA)], as new biomedical materials and evaluated their blood compatibility with attention to protein adsorption and platelet adhesion. The total amount of proteins adsorbed on the polymer surface from human plasma was determined, and the distribution of adsorbed proteins on the plasma-contacting surface was analyzed. The amount of proteins adsorbed on every poly (MAPC-co-BMA) was small compared with that observed on polymers without the phospholipid polar group. However, there was no significant difference in the amount of adsorbed proteins on the poly(MAPC-co-BMA) even when the methylene chain length between the phospholipid polar group and the backbone in the MAPC moiety was altered. Platelet adhesion on the polymer surface from a platelet suspension in a buffered solution was evaluated with and without plasma treatment on the surface. When a rabbit platelet suspension was brought into contact with the poly(BMA) surface after treatment with plasma, many platelets adhered and aggregated. However, a reduced amount of platelet adhered on the poly(BMA) was found in the case of direct contact with the platelet suspension. On the other hand, the poly(MAPC-co-BMA)s could inhibit platelet adhesion under both conditions. Based on these results, it can be concluded that the proteins adsorbed on the surface play an important role in determining the platelet adhesion and suppression of the protein adsorption on the surface, which is one of the most significant ways of inhibiting platelet adhesion. 相似文献
997.
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
998.
SHS法陶瓷衬管的研究现状及应用前景 总被引:2,自引:0,他引:2
回顾了自蔓延高温合成陶瓷衬管的发展历史,对国内外的研究现状进行归纳总结,介绍了离心SHS法生产陶瓷衬管的工艺特点及产品性能,展望了离心SHS陶瓷衬管的应用前景。 相似文献
999.
从理论上研究了纸张背衬不同衬底的光反射率,得出下列表达式:Rb=Ro+(R∞-Ro)×(1/R∞-Ro)/(1/B-Ro)(B为衬底的光反射率),该式简单实用且物理意义明确。利用上述公式,可将Tappi标准列出的Tappi不透明度C0.89的换算公式简化,并可从理论上定性地讨论纸张不透明度与印刷透印性的关系。 相似文献
1000.
V Thomé-Duret G Reach MN Gangnerau F Lemonnier JC Klein Y Zhang Y Hu GS Wilson 《Canadian Metallurgical Quarterly》1996,68(21):3822-3826
The development of a hypoglycemic alarm system using a subcutaneous glucose sensor implies that a decrease in blood glucose is rapidly followed by a decrease in the signal generated by the sensor. In a first set of experiments the linearity and the kinetics of the response of sensors implanted in the subcutaneous tissue of normal rats were investigated during a progressive increase in plasma glucose concentration: the sensitivities determined between 5 and 10 mM and between 10 and 15 mM were not significantly different, and a 5-10 min delay in the sensor's response was observed. In a second set of experiments, performed in diabetic rats, the kinetics of the decrease in subcutaneous glucose concentration following insulin administration was monitored during a decrease in plasma glucose level, from 15 to 3 mmol/L. During the 20 first min following insulin administration, the sensor monitored glucose concentration in subcutaneous tissue with no lag time. Subsequently, the decrease in the estimation of subcutaneous glucose concentration preceded that of plasma glucose. This phenomenon was not observed when the same sensors were investigated in vitro during a similar decrease in glucose concentration and may be due to a mechanism occurring in vivo, such as the effect of insulin on glucose transfer from the interstitial space to the cells surrounding the sensor. It reinforces the interest of the use of implantable glucose sensors as a part of a hypoglycemic alarm. 相似文献