全文获取类型
收费全文 | 14275篇 |
免费 | 1078篇 |
国内免费 | 395篇 |
专业分类
电工技术 | 658篇 |
综合类 | 479篇 |
化学工业 | 1990篇 |
金属工艺 | 487篇 |
机械仪表 | 548篇 |
建筑科学 | 677篇 |
矿业工程 | 149篇 |
能源动力 | 375篇 |
轻工业 | 1156篇 |
水利工程 | 204篇 |
石油天然气 | 265篇 |
武器工业 | 75篇 |
无线电 | 1710篇 |
一般工业技术 | 1622篇 |
冶金工业 | 3439篇 |
原子能技术 | 153篇 |
自动化技术 | 1761篇 |
出版年
2024年 | 62篇 |
2023年 | 215篇 |
2022年 | 423篇 |
2021年 | 623篇 |
2020年 | 456篇 |
2019年 | 388篇 |
2018年 | 437篇 |
2017年 | 415篇 |
2016年 | 425篇 |
2015年 | 476篇 |
2014年 | 608篇 |
2013年 | 736篇 |
2012年 | 767篇 |
2011年 | 856篇 |
2010年 | 634篇 |
2009年 | 580篇 |
2008年 | 591篇 |
2007年 | 515篇 |
2006年 | 426篇 |
2005年 | 339篇 |
2004年 | 290篇 |
2003年 | 258篇 |
2002年 | 280篇 |
2001年 | 221篇 |
2000年 | 183篇 |
1999年 | 264篇 |
1998年 | 1162篇 |
1997年 | 687篇 |
1996年 | 495篇 |
1995年 | 267篇 |
1994年 | 233篇 |
1993年 | 237篇 |
1992年 | 85篇 |
1991年 | 92篇 |
1990年 | 92篇 |
1989年 | 104篇 |
1988年 | 58篇 |
1987年 | 51篇 |
1986年 | 53篇 |
1985年 | 56篇 |
1984年 | 41篇 |
1983年 | 44篇 |
1982年 | 49篇 |
1981年 | 47篇 |
1980年 | 41篇 |
1979年 | 26篇 |
1978年 | 22篇 |
1977年 | 79篇 |
1976年 | 140篇 |
1975年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
HD Park MF Watanabe K Harda H Nagai M Suzuki M Watanabe H Hayashi 《Canadian Metallurgical Quarterly》1993,1(6):353-360
Amounts of hepatotoxic microcystin and neurotoxic anatoxin-a were estimated in natural blooms and strains of cyanobacteria from freshwaters in Japan. A simultaneous analysis method of anatoxin-a and microcystin was applied to natural bloom samples, which has been dominated by several species and the strains of cyanobacteria which produced simultaneously both toxins. The natural blooms examined in the present study were mainly composed of Anabaena and Oscillatoria, but most also contained Microcystis and other cyanobacteria. Only one sample was almost unialgal, Anabaena spiroides, collected from Lake Sagami. The toxins in 14 samples collected from nine different natural blooms during 1988-1992 were identified as microcystins-RR, -YR, and -LR; desmethyl-7-microcystin-LR (7-DMLR); and anatoxin-a. Microcystins were the main toxins contained in these natural blooms, with anatoxin-a not being detected or of very little quantity. 7-DMLR was detected in samples only from Lake Kasumigaura. Five strains of Anabaena isolated from waters in Japan produced a small amount of anatoxin-a, but no microcystins. One half of the strains of Microcystis produced microcystins and/or anatoxin-a. This is the first study showing Microcystis producing both anatoxin-a and microcystins. 相似文献
32.
SF Breniere MF Bosseno C Barnabe S Urdaneta-Morales M Tibayrenc 《Canadian Metallurgical Quarterly》1993,88(1):163-165
Detection of a nondistended pyriform sinus on cross-sectional imaging studies represents a diagnostic dilemma. The finding may be an inconstant physiologic phenomenon without clinical significance, or it may be due to tissue thickening and lack of pliability related to neoplasia or inflammation. Rescanning during respiratory maneuvers may clarify the anatomy, but full patient cooperation is needed. We demonstrate a method (turning the patient's head away from the side of the nondistended sinus) that induces distention of the pyriform sinus but does not require active patient participation. 相似文献
33.
34.
简单介绍了碳氧比测井的原理及通常的数据处理方法。分析了由常规数据处理所得曲线仍然存在的问题及可能的成因 ,并给出了可行的修正办法。讨论了另一种可行的曲线异常数据的检测、剔除方法。实践表明 :文章讨论的两点建议都是可行的 ,并且在提高测量曲线质量的同时也提高了地层含油饱和度的解释精度。 相似文献
35.
论述了电磁铁铁芯 (硅钢片 )模具的设计要点及其线切割加工的技巧 ,提出了提高模具加工精度和使用寿命的有效措施。 相似文献
36.
N. Roussel S. Staquet L. D’Aloia Schwarzentruber R. Le Roy F. Toutlemonde 《Materials and Structures》2007,40(9):877-887
Casting simulations of self-compacting concrete are carried out in order to obtain a value of the minimum fluidity needed to cast a VHPC precambered composite beam. The mix proportioning of the concrete takes into account this minimum value. The numerical predictions are finally compared with the experimental observations during two casting tests and the real casting of the two 13 m beams. Although the simplifying assumptions needed to carry out the simulations are numerous, there is an agreement between the predictions and the real casting. 相似文献
37.
38.
P. Papet N. Le Bars J. F. Baumard A. Lecomte A. Dauger 《Journal of Materials Science》1989,24(11):3850-3854
Transparent yttria-stabilized zirconia monolithic gels were synthesized under controlled conditions for hydrolysis and chemical polymerization. The influence of acetylacetone on the previous chemical reactions was explored, and a plausible explanation was proposed concerning the outstanding role of this additive during the gelation process. Small-angle X-ray scattering was used to estimate the size of the polymeric species and to investigate the influence of acetylacetone on the structure of the gels prepared. 相似文献
39.
The ring shape is a good solution to the study of the magnetization processes of magnetic materials because demagnetizing fields are easily avoided. However, when small samples are investigated, the magnitude of the field applied is necessarily limited by the low number of primary winding turns, and by the cross section of the wire itself. The use of sequential-type techniques for high current supply allows this problem to be avoided. One-cycle power production from the 50 Hz AC-line voltage is a simple example of such techniques. An electronic device designed around a commercial integrated circuit is described. A full period of current of 20-ms duration is applied to the load with a magnitude ranging from 0 to 100 A. Magnetization parameters of soft polycrystalline ring ceramics approaching the saturation region are studied as an application. The fitness to measure such characteristic parameters as saturation magnetization and magnetic hardness is shown 相似文献
40.
In "Stationary distributions for the random waypoint mobility model" (TMC, Vol. 3, No, 1), Navidi and Camp find the stationary distribution of the random waypoint model, with or without pause on a rectangular area. In this short note, we show that, under the stationary regime, speed and location are independent. 相似文献