全文获取类型
收费全文 | 14606篇 |
免费 | 1935篇 |
国内免费 | 588篇 |
专业分类
电工技术 | 214篇 |
综合类 | 1085篇 |
化学工业 | 5780篇 |
金属工艺 | 366篇 |
机械仪表 | 835篇 |
建筑科学 | 861篇 |
矿业工程 | 272篇 |
能源动力 | 321篇 |
轻工业 | 1675篇 |
水利工程 | 153篇 |
石油天然气 | 946篇 |
武器工业 | 33篇 |
无线电 | 1024篇 |
一般工业技术 | 1716篇 |
冶金工业 | 1067篇 |
原子能技术 | 360篇 |
自动化技术 | 421篇 |
出版年
2024年 | 45篇 |
2023年 | 217篇 |
2022年 | 330篇 |
2021年 | 591篇 |
2020年 | 534篇 |
2019年 | 503篇 |
2018年 | 447篇 |
2017年 | 573篇 |
2016年 | 610篇 |
2015年 | 607篇 |
2014年 | 896篇 |
2013年 | 915篇 |
2012年 | 1262篇 |
2011年 | 1122篇 |
2010年 | 854篇 |
2009年 | 893篇 |
2008年 | 715篇 |
2007年 | 915篇 |
2006年 | 832篇 |
2005年 | 656篇 |
2004年 | 570篇 |
2003年 | 510篇 |
2002年 | 410篇 |
2001年 | 329篇 |
2000年 | 280篇 |
1999年 | 234篇 |
1998年 | 174篇 |
1997年 | 166篇 |
1996年 | 149篇 |
1995年 | 117篇 |
1994年 | 98篇 |
1993年 | 80篇 |
1992年 | 89篇 |
1991年 | 60篇 |
1990年 | 49篇 |
1989年 | 38篇 |
1988年 | 29篇 |
1987年 | 44篇 |
1986年 | 25篇 |
1985年 | 45篇 |
1984年 | 42篇 |
1983年 | 26篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 3篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1959年 | 2篇 |
1955年 | 1篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
J. Sieber D. Broton C. Fales S. Leigh B. MacDonald A. Marlow S. Nettles J. Yen 《Cement and Concrete Research》2002,32(12):1899-1906
The eight portland cements and two calcium aluminate cements in the Standard Reference Material (SRM) 1880 series are among the most popular SRMs in the catalog of the National Institute of Standards and Technology (NIST) Standard Reference Materials Program. Numerous laboratories rely on them for elemental analysis and qualification for ASTM C 114-00 Standard Test Methods for Chemical Analysis of Hydraulic Cement. NIST has collected new candidate materials from around the world and partnered with Construction Technology Laboratories (CTL) in their preparation and certification. This paper describes the procedures taken at NIST and CTL to prepare and test materials for certification including the homogeneity testing, the X-ray fluorescence methods and the statistical data analysis performed for value assignment. 相似文献
52.
高温延缓型有机硼OB-200交联压裂液的性能与应用 总被引:7,自引:2,他引:5
报道了实验考察高温延缓型有机硼交联剂OB 200在5g/L羟丙基瓜尔胶水基压裂液中的各项性能及其影响因素的结果,简述了在7口井上应用该压裂液的情况。OB 200/HPG压裂液在pH=11.5、温度5~35(40)℃时交联时间长达4.7~5.6min;不加破胶剂的压裂液在温度115~135℃时,8h内可完全破胶液化,讨论了OB 200体系的自动破胶机制;在135℃、170s-1条件下剪切2h,压裂液粘度>120mPa·s;高速(500s-1)剪切后,在低速下(80s-1)粘度可恢复到初始值的94.5%(95℃下)或70.0%(135℃下);在95~135℃滤失小,滤失系数为6.93×10-4~9.81×10-4m/(min)1/2;残渣含量低,135℃下破胶20h后为319mg/L,而对比硼酸盐压裂液(90℃)和有机钛压裂液(135℃)分别为364和457mg/L;在人造岩心上测得渗透率伤害率在5.74%~9.66%,平均7.32%,而对比有机钛压裂液为24.07%~29.98%,平均27.09%。在中原油田桥口和户部寨地区7口井2706~3769m井段用该压裂液压裂,施工成功率100%,获得了油、气增产效果。图5表4参3。 相似文献
53.
54.
Kenji Imura 《Color research and application》2007,32(3):195-200
In this article, a new method for measuring a total spectral radiance factor of a FWA‐treated sample illuminated by a specific standard illuminant is introduced. The method replaces an unstable real fluorescent standard by a bi‐spectral luminescent radiance factor data, which works as a virtual fluorescent standard (VFS) by knowing spectral intensity distributions of illuminations applied to the sample. The method utilizes two illuminations I1 and I2 whose relative spectral intensity distributions are different from each other and synthesizes a virtual illumination presenting the identical fluorescent spectral radiance factor to that presented by the standard illuminant with the VFS of the specific bi‐spectral luminescent radiance factor by linearly combining I1 and I2 with the suitable weighting factors. The applicability of the method is examined in principle by comparing ISO brightness and CIE whiteness index of fluorescent standard paper as a test sample obtained by this new method to the assigned values. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 195–200, 2007 相似文献
55.
Hari B. Goyal M. O. Garg K. R. Rao R. D. Srivastava 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1985,35(2):49-56
The kinetics of the reaction of acetic acid and acetylene over zinc acetate-activated carbon catalyst was investigated over a wide range of process variables in a pilot reactor. Although various catalytic reaction mechanisms were postulated, the rate of reaction was most satisfactorily correlated by a mechanism of surface reaction between charged adsorbed acetic acid and acetylene, which assumes that the rate controlling step was the irreversible charged adsorption of acetylene and acetic acid. 相似文献
56.
57.
鼻咽癌药物我成像定位仪的光学设计 总被引:9,自引:1,他引:8
对药物荧光鼻咽癌定位的光学系统进行理论分析,给出了该系统的光学设计方法和设计结果。光学系统设计包括,激光器出射光束与光纤高效率耦合技术,同光轴非接触两光纤间的光束耦合技术以及获得较好的像清晰度和衬度的技术。 相似文献
58.
New HPLC Method to Determine Ethyl Carbamate in Alcoholic Beverages Using Fluorescence Detection 总被引:2,自引:0,他引:2
ABSTRACT: A new methodology to the quantification of ethyl carbamate (EC) has been developed. This method allows the analysis by HPLC of ethyl carbamate in samples of wine, fortified wine, and wine brandy, by a pre-column derivatization with 9-xanthydrol, and fluorescence detection. This does not require previous sample extraction or concentration. The method presents an average recovery of 96% among samples studied, a detection limit of 4.2μg/L, and an average intermediate precision of 6.3%. The comparison of the results obtained for EC analysis on the same wine brandy samples by GC/MS and HPLC are statistically indistinguishable with 97.5% probability. The results of the analysis of 42 samples are presented. 相似文献
59.
HerlinaAdrian Wing-Keung Law 《International Journal of Heat and Mass Transfer》2002,45(24):4899-4905
The results of a laboratory investigation on the turbulence characteristics of a circular three-dimensional turbulent wall jet are presented. Measurements were taken up to 50 nozzle diameters using combined particle image velocimetry and planar laser induced fluorescence. The results showed that the induced turbulence was still evolving in the present range and had not achieved similarity. While the turbulent intensity for both velocity and concentration increased downstream, the turbulent mass transport showed a decline over distance for both the streamwise and spanwise directions, implying weakening dispersion from the jet core. 相似文献
60.
D. Bogdal V. Yashchuk J. Pielichowski T. Ogul'Chansky M. Warzala V. Kudrya 《应用聚合物科学杂志》2002,84(9):1650-1656
The alkyl methacrylates with halogenated carbazolyl pendant groups were prepared, and the analysis of their absorption and emission spectra showed that the polymers containing monohalogenatged carbazole rings were capable of exhibiting a high singlet‐triplet (S‐T) conversion. The reasons that mainly triplet excitons could be observed in such polymers and additional bands appearance in the spectra of the polymers with dihalogenated carbazole rings are discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1650–1656, 2002; DOI 10.1002/app.10469 相似文献