全文获取类型
收费全文 | 333035篇 |
免费 | 23974篇 |
国内免费 | 12553篇 |
专业分类
电工技术 | 17911篇 |
技术理论 | 56篇 |
综合类 | 19689篇 |
化学工业 | 56538篇 |
金属工艺 | 18546篇 |
机械仪表 | 21175篇 |
建筑科学 | 25715篇 |
矿业工程 | 10960篇 |
能源动力 | 9763篇 |
轻工业 | 18630篇 |
水利工程 | 5255篇 |
石油天然气 | 22975篇 |
武器工业 | 2599篇 |
无线电 | 36630篇 |
一般工业技术 | 39800篇 |
冶金工业 | 18379篇 |
原子能技术 | 3215篇 |
自动化技术 | 41726篇 |
出版年
2024年 | 1289篇 |
2023年 | 5210篇 |
2022年 | 8869篇 |
2021年 | 12542篇 |
2020年 | 9823篇 |
2019年 | 8008篇 |
2018年 | 9199篇 |
2017年 | 10375篇 |
2016年 | 9278篇 |
2015年 | 12218篇 |
2014年 | 15868篇 |
2013年 | 19179篇 |
2012年 | 20166篇 |
2011年 | 22447篇 |
2010年 | 19199篇 |
2009年 | 18330篇 |
2008年 | 17974篇 |
2007年 | 17395篇 |
2006年 | 18276篇 |
2005年 | 16131篇 |
2004年 | 10344篇 |
2003年 | 9127篇 |
2002年 | 8132篇 |
2001年 | 7472篇 |
2000年 | 8003篇 |
1999年 | 9653篇 |
1998年 | 8156篇 |
1997年 | 6769篇 |
1996年 | 6362篇 |
1995年 | 5339篇 |
1994年 | 4378篇 |
1993年 | 3089篇 |
1992年 | 2492篇 |
1991年 | 1961篇 |
1990年 | 1504篇 |
1989年 | 1232篇 |
1988年 | 1019篇 |
1987年 | 681篇 |
1986年 | 535篇 |
1985年 | 342篇 |
1984年 | 243篇 |
1983年 | 204篇 |
1982年 | 196篇 |
1981年 | 129篇 |
1980年 | 130篇 |
1979年 | 67篇 |
1978年 | 33篇 |
1977年 | 38篇 |
1976年 | 55篇 |
1975年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Xing Li Zuoqing Wang Cheng Kuei Jen Viens M. Cheeke J.D.N. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1996,43(2):331-336
Theoretical and experimental investigations of thin-walled tube acoustic wave devices for gravimetric sensing applications are presented. Integrated sensor configurations have been demonstrated by employing a sol-gel processed thin piezoelectric lead zirconate titanate (PZT) film. This was coated coaxially on stainless steel tubes and interdigital transducers (IDT) fabricated as the transmitter and receiver on the curved tube surfaces. We have observed tube waves along both the axial and circumferential directions between 1 and 6.6 MHz. We have also analyzed the mass sensitivities of different modes propagating along the tubes and shown that high mass sensitivity can be achieved by keeping the tube wall thin 相似文献
122.
Hankun Wang 《Dynamics and Control》1993,3(4):353-369
In this article, we consider stabilization of two wave equations coupled in parallel by viscous damping. Uniform exponential stabilization can be achieved when damping is presented in two equations. In general only strong stabilization can be achieved when damping is present in one equation, while uniform exponential stabilization is still possible for some special cases. 相似文献
123.
Da-Peng Wang Gow-Zaw Liang Yu-Hsing Tu 《Drug development and industrial pharmacy》1994,20(11):1895-1903
A stability-indicating reversed-phase high performance liquid chromatographic method was developed for the detection of mitoxantrone HC1 and its degradation products under accelerated degradation conditions. The degradation kinetics of mitoxantrone HC1 in aqueous solution over a pH range of 1.18 to 7.20 and its stability in propylene glycol-or polyethylene glycol 400-based solutions were investigated. The observed rate constants were shown to follow apparent first-order kinetics in all cases. The pH-rate profile shows that maximum stability of mitoxantrone HC1 was obtained at pH 4.01. No general acid or base catalysis from acetate or phosphate buffer species was observed. The catalysis rate constants on the protonated mitoxantrone imposed by hydrogen ion water and hydroxy ion were determined to be 3.72 × 10 min-1 5.64 × 10-min-1 and 1.108 × 10-2min-1, respectively. The degradation rate constants of mitoxantrone affected by different ionic strength systems. Irradiation with 254 nm UV light at 25±0.5°C was found when canpared with the light-protected controls. Incorporation of nonaqueous propylene glycol or polyethylene glycol in the pH 4.01 mitoxantrone solution shows an increase in its stability at 502±0.5°C. 相似文献
124.
化学镀Ni—P镀层的X射线衍射研究 总被引:2,自引:0,他引:2
根据X射线衍射分析结果,对化学镀高P(含P>11wt%或19at%)Ni-P镀层加热时效时,镀层成分和加热温度对结构转变的影响作了研究,结果表明,高P共晶、过共晶(含P>11wt%或19at%)合金的结构转变有如下特征:(1)相同加热时效条件下,Ni-P合金的结构转变与成分有密切关系:(2)对同一成分的过共晶合金,Ni-P合金的结构转变与时效温度密切相关;(3)过共晶合金在290~360℃温度范围内时效处理,出现Ni_xP_y介稳相,X射线衍射分析认为Ni_xP_y为Ni_(12)P_5。 相似文献
125.
本文介绍了用αβ谱仪系统同时测量αβ谱、实现Rn/Th子体补偿、确定超铀α核素气溶胶体积活度及人工放射性气溶胶总β体积活度的技术途径。利用RaA、RaC′a峰的二段时间计数可确定空气中RaA、RaB、RaC的气溶胶体积活度,相应的,也能给出RaB、RaC对总β计数的贡献。根据一般环境条件下的平衡比,用ThC′的。计数修正Th子体对αβ测量的影响。 ̄[239]pu或/和 ̄[241]Am人工核素的α计数,可通过两段时间分别扣除RaA、RaC′拖尾的方法确定;β计数分别扣除Rn/Th子体β贡献即可确定。在本文规定的测量条件下,对室内天然Rn子体水平在15Bq/m ̄3以下,超铀α核素气溶胶体积活度的测量下限可达到0.1Bq/m ̄3;即使在75Bq/m ̄3环境下,人工核素总β的测量下限也可达lBq/m ̄3以下。 相似文献
126.
E Galanis J Buckner D Kimmel R Jenkins B Alderete J O''Fallon CH Wang BW Scheithauer CD James 《Canadian Metallurgical Quarterly》1998,13(4):717-724
ND10 are recently characterized nuclear domains that are composed of 0.5 microm sized, precisely circumscribed dots in cultured human cell lines. To investigate the distribution and number of ND10 on various types of normal and neoplastic human tissues, we carried out immunostaining and immunoprecipitation analyses with monoclonal antibodies 138 and 1150. The number of ND10 varied from 1 to 10 or more in various tissues as did their size. ND10 were diffusely located in early embryonic and normal tissues, except for the exocrine and endocrine cells of the pancreas and for hepatocytes. In normal squamous mucosa, basal cells had more ND10 than did differentiated superficial squamous cells. The number and size of ND10 were markedly increased in malignant neoplasms but were similar in benign tumors and corresponding normal tissues. Sex hormone-related normal tissues, such as the endometrium or myometrium, and neoplasms strongly stained for ND10. The distribution pattern of ND10 in human tissues indicates that they are conserved nuclear substructures that are closely associated with cellular differentiation, hormonal stimulation, and oncogenesis. 相似文献
127.
直接斜率波前复原算法的控制效果分析 总被引:7,自引:0,他引:7
建立自适应光学系统功率谱抑制函数的概念,分析了采用直接斜率波前复原算法的自适应当光学系统的控制效果,理论分析与61单元自适应光学系统上的实验结果表明,直接斜率波前复原算法将导致控制效果下降。 相似文献
128.
Plasmapropertiesoflaser-ablatedSttargetinairWangXiang-Tai(王象泰);ManBao-Yuan(满宝元);WangGong-Tang(王公堂);FanXi-Jun(樊锡君);WangJun(王军)... 相似文献
129.