全文获取类型
收费全文 | 368篇 |
免费 | 7篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 147篇 |
金属工艺 | 8篇 |
机械仪表 | 7篇 |
建筑科学 | 9篇 |
能源动力 | 28篇 |
轻工业 | 30篇 |
水利工程 | 1篇 |
无线电 | 24篇 |
一般工业技术 | 66篇 |
冶金工业 | 18篇 |
原子能技术 | 16篇 |
自动化技术 | 9篇 |
出版年
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 10篇 |
2017年 | 2篇 |
2016年 | 8篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 29篇 |
2012年 | 14篇 |
2011年 | 17篇 |
2010年 | 18篇 |
2009年 | 21篇 |
2008年 | 28篇 |
2007年 | 19篇 |
2006年 | 15篇 |
2005年 | 9篇 |
2004年 | 18篇 |
2003年 | 8篇 |
2002年 | 15篇 |
2001年 | 9篇 |
2000年 | 14篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1972年 | 2篇 |
1967年 | 1篇 |
排序方式: 共有375条查询结果,搜索用时 15 毫秒
41.
本文主要介绍以φ4×4英寸 NaI(Tl)为探测器的4道脉冲甄别器,用以测量和区分包括宇宙射线在内的不同成分的环境天然辐射水平的方法。4道:Disr、Ch1、Ch2、Ch3的甄别阈范围设定为使其能记录的γ射线的能量范围(主要包括天然辐射成分)依次约为0.58MeV—∞(~(40)K、铀、钍系核素的γ射线,宇宙射线)、2.0—4.2MeV(铀系~(214)Bi 中能量为2.2MeV 的γ射线,钍系~(208)Tl 中能量为2.61MeV 的γ射线,少量低能宇宙射线)、>4.2 MeV(除少量低能宇宙射线外的全部宇宙射线)、>12.5MeV(能量较高的宇宙射线)。用此方法在中国辐射防护研究院低本底放射性实验室和地下铁室进行了测量,评价了地下铁室的屏蔽效果。文中还给出了在广州—太原和北京—大阪航线的飞机上的测量结果。 相似文献
42.
Molecular motion in the β-form crystal of fully annealed silk fibre was investigated by means of an X-ray diffractometer, an infra-red spectrophotometer, and thermal and viscoelastic measurements. There was ordinary thermal expansion in stable sheets up to 250°C, in which chains were bound side by side with intermolecular hydrogen bonds. It was shown that the slip motion between the sheets started at about 200°C, accompanied by active motion and/or slight scission of the side chains packed in the intersheets. Melting of the crystal occurred due to scission of the intermolecular hydrogen bonds above 260°C in the sheets. Melting was accompanied by degradation of the molecular chains. 相似文献
43.
A series of resol-type phenol-formaldehyde resins with varying phenol/formaldehyde (P/F) molar ratio were investigated by infrared spectroscopy. The infrared spectroscopic data suggest that absorbance ratio of D2920, D1610, D1150, D1010, and D760 based on 1 590 cm?1 band can be used for the determination of phenol/formaldehyde molar ratio of the resins. 相似文献
44.
The polymerization of acrylonitrile was studied by the system of copper(II)-oligo(n)ethylene-(n+1)amine complex and carbon tetrachloride. Addition of amines to the initiating system accelerates the polymerization. The acceleration by these amines was found to be in the following order: prim.-amine<sec.-amine<tert.-amine<diamine<phenylenediamine. Effects of the sort of the ligands in the copper(II) chelates on the polymerization were also studied. 相似文献
45.
Behaviormetrika - Apartment dwellers move more and more frequently in recent years. Motives of the move are job transfer, change for better housing, and marriage. The desire for change is the... 相似文献
46.
Masanobu Horie Akira ItoTakehiko Kiyohara Yoshinori KawabeMasamichi Kamihira 《Journal of Bioscience and Bioengineering》2010,110(5):582-587
Conventionally, embryonic stem (ES) cells are cultured on a cell layer of mouse embryonic fibroblasts (MEFs) as feeder cells to support undifferentiated growth of ES cells. In this study, cell–cell interactions between mouse ES and feeder cells were artificially engineered via an epithelial cell adhesion molecule, E-cadherin, whose expression is considerable in ES cells. Mouse mesenchymal STO and NIH3T3 cells that were genetically engineered to express E-cadherin were used in ES cell cultures as feeder cells. ES cells cultured on the E-cadherin-expressing feeder cells maintained the expression of stem cell markers, alkaline phosphatase (AP), Oct3/4, Nanog and Sox2, and the efficiency of AP-positive colony formation was comparable to MEFs, and much better than parental STO and NIH3T3 cells. Furthermore, ES cells maintained on the E-cadherin-expressing feeder cells possessed the ability to differentiate into the three germ layers both in vitro and in vivo. The results indicated that E-cadherin expression in feeder cells could improve the performance of feeder cells, which may be further applicable to create new artificial feeder cell lines. 相似文献
47.
Toshiaki Yamaguchi Sota Shimizu Toshio Suzuki Yoshinobu Fujishiro Masanobu Awano 《Journal of the American Ceramic Society》2009,92(S1):S107-S111
We report the design and fabrication of a novel electrode-supported honeycomb solid oxide fuel cell (SOFC), that can generate high volumetric power density. Among various cell designs, honeycomb SOFCs are suitable for compact SOFC modules because they have a large surface electrode area per unit volume. We have succeeded in fabricating a cathode-supported honeycomb SOFC via extrusion of a LaSrMnO3 honeycomb monolith and through the use of a new slurry injection method for the channel surface coating using electrolyte/anode bi-layers. The fabricated honeycomb SOFCs exhibited high volumetric power densities of approximately 1.2 W/cm3 at 600°C under a wet H2 fuel flow. 相似文献
48.
Ni-free 23Cr-1N stainless steel was examined as bipolar plates for proton exchange membrane fuel cells. Corrosion resistance of the 23Cr-1N stainless steel was better relative to 22Cr stainless steel in the simulated cathodic environments. As confirmed by X-ray photoelectron spectroscopy, the polarized 22Cr and 23Cr-1N stainless steels at pH 2.3 presented predominantly chromium oxide in the outer passive layers. At pH 4.3, the passive layer of the polarized 22Cr stainless steel changed to iron oxides dominant. Interestingly, on the other hand, the polarized 23Cr-1N stainless steel preserved chromium oxide rich outer passive layer, which provides good corrosion resistance. As a result, although the initial cell voltage was slightly lower (∼40 mV), the 23Cr-1N stainless steel bipolar plates employing cell showed better cell voltage stability up to 1000 h, compared with the 22Cr stainless steel employing cell. The operation voltage became further higher through a surface modification of the 23Cr-1N stainless steel with TiN nanoparticles. It seems that the corrosion resistive Ni-free 23Cr-1N is possible to apply for bipolar plates of proton exchange membrane fuel cells. 相似文献
49.
Yukari Totsuka Takashi Higuchi Toshio Imai Akiyoshi Nishikawa Takehiko Nohmi Tatsuya Kato Shuich Masuda Naohide Kinae Kyoko Hiyoshi Sayaka Ogo Masanobu Kawanishi Takashi Yagi Takamichi Ichinose Nobutaka Fukumori Masatoshi Watanabe Takashi Sugimura Keiji Wakabayashi 《Particle and fibre toxicology》2009,6(1):1-11
Background
Recently, manufactured nano/microparticles such as fullerenes (C60), carbon black (CB) and ceramic fiber are being widely used because of their desirable properties in industrial, medical and cosmetic fields. However, there are few data on these particles in mammalian mutagenesis and carcinogenesis. To examine genotoxic effects by C60, CB and kaolin, an in vitro micronuclei (MN) test was conducted with human lung cancer cell line, A549 cells. In addition, DNA damage and mutations were analyzed by in vivo assay systems using male C57BL/6J or gpt delta transgenic mice which were intratracheally instilled with single or multiple doses of 0.2 mg per animal of particles.Results
In in vitro genotoxic analysis, increased MN frequencies were observed in A549 cells treated with C60, CB and kaolin in a dose-dependent manner. These three nano/microparticles also induced DNA damage in the lungs of C57BL/6J mice measured by comet assay. Moreover, single or multiple instillations of C60 and kaolin, increased either or both of gpt and Spi- mutant frequencies in the lungs of gpt delta transgenic mice. Mutation spectra analysis showed transversions were predominant, and more than 60% of the base substitutions occurred at G:C base pairs in the gpt genes. The G:C to C:G transversion was commonly increased by these particle instillations.Conclusion
Manufactured nano/microparticles, CB, C60 and kaolin, were shown to be genotoxic in in vitro and in vivo assay systems. 相似文献50.
Zero crossing (ZC) statistic is the number of zero crossings observed in a time series. The expected value of the ZC specifies the first‐order autocorrelation of the processes. Hence, we can estimate the autocorrelation by using the ZC estimator. The asymptotic consistency and normality of the ZC estimator for scalar Gaussian processes are already discussed in 1980. In this article, first, we derive the joint asymptotic distribution of the ZC estimator for ellipsoidal processes. Next, we show the variance of the ZC estimator does not attain the Cramer–Rao lower bound (CRLB). However, it is shown that the ZC estimator has robustness when the process is contaminated by an outlier. In contrast with this, we observe that the quasi‐maximum likelihood estimator (QMLE) attains the CRLB. However, we can see that QMLE is sensitive for the outlier. 相似文献