全文获取类型
收费全文 | 5087篇 |
免费 | 189篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 313篇 |
综合类 | 17篇 |
化学工业 | 1527篇 |
金属工艺 | 132篇 |
机械仪表 | 143篇 |
建筑科学 | 128篇 |
矿业工程 | 5篇 |
能源动力 | 215篇 |
轻工业 | 465篇 |
水利工程 | 18篇 |
石油天然气 | 8篇 |
无线电 | 368篇 |
一般工业技术 | 1057篇 |
冶金工业 | 322篇 |
原子能技术 | 140篇 |
自动化技术 | 439篇 |
出版年
2023年 | 38篇 |
2022年 | 57篇 |
2021年 | 137篇 |
2020年 | 61篇 |
2019年 | 79篇 |
2018年 | 95篇 |
2017年 | 76篇 |
2016年 | 120篇 |
2015年 | 93篇 |
2014年 | 140篇 |
2013年 | 271篇 |
2012年 | 272篇 |
2011年 | 321篇 |
2010年 | 259篇 |
2009年 | 282篇 |
2008年 | 306篇 |
2007年 | 248篇 |
2006年 | 233篇 |
2005年 | 156篇 |
2004年 | 167篇 |
2003年 | 182篇 |
2002年 | 181篇 |
2001年 | 102篇 |
2000年 | 88篇 |
1999年 | 82篇 |
1998年 | 162篇 |
1997年 | 109篇 |
1996年 | 97篇 |
1995年 | 78篇 |
1994年 | 66篇 |
1993年 | 75篇 |
1992年 | 61篇 |
1991年 | 65篇 |
1990年 | 42篇 |
1989年 | 52篇 |
1988年 | 20篇 |
1987年 | 44篇 |
1986年 | 31篇 |
1985年 | 44篇 |
1984年 | 28篇 |
1983年 | 40篇 |
1982年 | 41篇 |
1981年 | 33篇 |
1980年 | 23篇 |
1979年 | 25篇 |
1978年 | 25篇 |
1977年 | 21篇 |
1976年 | 23篇 |
1975年 | 9篇 |
1974年 | 10篇 |
排序方式: 共有5297条查询结果,搜索用时 15 毫秒
971.
972.
973.
974.
Kurauchi K Nakaguchi Y Tsutsumi M Hori H Kurihara R Hashimoto S Ohnuma R Yamamoto Y Matsuoka S Kawai S Hirata T Kinoshita M 《Environmental science & technology》2005,39(8):2762-2768
Detection of endocrine disrupting chemicals, in particular, environmental estrogens with living organisms, has many advantages if compared to chemical analysis. The screening of novel pollutants with meaningful endpoints, the integration of uptake, bioconcentration, and excretion as well as the evaluation of endocrine disrupting effects with respect to toxicity require in vivo biotests for estrogen-like substances (ELSs). Critical disadvantages of whole organism biotests are their low sensitivity and the need for laborious and time-consuming work. To overcome these problems, we have developed a transgenic medaka strain harboring the green fluorescence protein (GFP) gene driven by choriogenin H gene regulatory elements. Choriogenin H is an egg envelope protein induced by estrogens in the liver. With yolk sac larvae of this strain, GFP induction in liver was observed 24 h after onset of aqueous exposure to 0.63 nM 17beta-estradiol (E2), 0.34 nM ethynylestradiol, or 14.8 nM estrone. Furthermore, concentrated sewage treatment effluent induced GFP expression. Comparison of E2 equivalents estimated by GFP-induction in transgenic medaka, a YES assay, and GC/MS showed detection limits in the same order of magnitude. These results indicated that the sensitivity of the transgenic medaka strain was sufficient for application as an alternative model in monitoring environmental water samples for ELSs. 相似文献
975.
Yui T Kan A Saitoh C Koike K Ibusuki T Ishitani O 《ACS applied materials & interfaces》2011,3(7):2594-2600
Reduction of CO(2) using semiconductors as photocatalysts has recently attracted a great deal of attention again. The effects of organic adsorbates on semiconductors on the photocatalytic products are noteworthy. On untreated TiO(2) (P-25) particles a considerable number of organic molecules such as acetic acid were adsorbed. Although irradiation of an aqueous suspension of this TiO(2) resulted in the formation of a significant amount of CH(4) as a major product, it was strongly suggested that its formation mainly proceeded via the photo-Kolbe reaction of acetic acid. Using TiO(2) treated by calcination and washing procedures for removal of the organic adsorbates, CO was photocatalytically generated as a major product, along with a very small amount of CH(4), from an aqueous suspension under a CO(2) atmosphere. In contrast, by using Pd (>0.5 wt %) deposited on TiO(2) (Pd-TiO(2)) on which organic adsorbates were not detected, CH(4) was the main product, but CO formation was drastically reduced compared with that on the pretreated TiO(2). Experimental data, including isotope labeling, indicated that CO(2) and CO(3)(2-) are the main carbon sources of the CH(4) formation, which proceeds on the Pd site of Pd-TiO(2). Prolonged irradiation caused deactivation of the photocatalysis of Pd-TiO(2) because of the partial oxidation of the deposited Pd to PdO. 相似文献
976.
Yanai N Kitayama K Hijikata Y Sato H Matsuda R Kubota Y Takata M Mizuno M Uemura T Kitagawa S 《Nature materials》2011,10(10):787-793
The development of a new methodology for visualizing and detecting gases is imperative for various applications. Here, we report a novel strategy in which gas molecules are detected by signals from a reporter guest that can read out a host structural transformation. A composite between a flexible porous coordination polymer and fluorescent reporter distyrylbenzene (DSB) selectively adsorbed CO? over other atmospheric gases. This adsorption induced a host transformation, which was accompanied by conformational variations of the included DSB. This read-out process resulted in a critical change in DSB fluorescence at a specific threshold pressure. The composite shows different fluorescence responses to CO? and acetylene, compounds that have similar physicochemical properties. Our system showed, for the first time, that fluorescent molecules can detect gases without any chemical interaction or energy transfer. The host-guest coupled transformations play a pivotal role in converting the gas adsorption events into detectable output signals. 相似文献
977.
Ino T Hayashi T Fukuda T Ueno K Shirai H 《Journal of nanoscience and nanotechnology》2011,11(9):8035-8039
Highly-conductive poly(3,4-ethylene dioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) films obtained by the addition of dimethylsulfoxide (DMSO) and the argon plasma exposure were used as a transparent conductive anode (TCA) for copper-phthalocyanine (CuPc)/C60 organic thin-film solar cells (OSCs). The CuPc/C60 OSCs on as-grown DMSO added PEDOT:PSS layer showed a power efficiency of 0.6%, whereas it was improved markedly to 1.34% after the atmospheric-pressure argon plasma exposure, which was comparable to that formed on indium-tin-oxide layer. Effects of the DMSO addition and the argon plasma exposure in the spin-coated PEDOT:PSS films is demonstrated in terms of the in-depth characterization of optical and electrical properties. 相似文献
978.
Tsukigase H Suzuki Y Berger MH Sagawa T Yoshikawa S 《Journal of nanoscience and nanotechnology》2011,11(3):1914-1922
SnS-sensitized TiO2 electrodes were applied in quantum dot-sensitized solar cells (QDSSCs) which are environmentally more favorable than conventional Cd or Pb-chalcogenide-sensitized electrodes. SnS nanoparticles were well-distributed over the surface of TiO2 nanoparticles by the successive ionic layer adsorption and reaction (SILAR) method. Deposited SnS nanoparticles had diameter about 3 nm. Under AM1.5 irradiation with 100 mW/cm2 light intensity (at 1 sun), the energy conversion efficiency of obtained cells reached a value of 0.21% (0.25 cm2) at SILAR coating cycles of 5. In addition, the photovoltaic performance was improved by additional ZnS coating on the surface of SnS-sensitized TiO2 electrodes. 相似文献
979.
Carbon nanofibers (CNFs) and carbon nanotubes (CNTs) are new carbon-based materials. However, the production of CNFs and CNTs is very difficult due to the complicated processes and high temperature involved. Therefore, a method of fabrication is required that enables high throughput at a low cost.Our previous study reported that oxygen ion beam energy of 500 eV applied to glassy carbon (GC) forms the finest pitch conical anti-reflection (AR) structures, and that an irradiation time of more than 24 min fabricates conical AR structures with heights of more than 250 nm. After the fabrication of the AR structures, irradiation by an argon ion (Ar+ beam changes the surface morphology, and oblique angle irradiation can form CNFs. Thus, we carried out oblique Ar+ beam irradiation on conical carbon protrusions on GC fabricated by oxygen ion beam irradiation. As a result, CNFs have been formed using oxygen and argon ion beam irradiation at room temperature. In addition, multi-wall CNT can be obtained by two-step ion beam irradiation. 相似文献
980.
Noriyasu Kobayashi Souichi Ueno Satoshi Nagai Makoto Ochiai Noboru Jimbo 《Nuclear Engineering and Design》2011,241(12):4643-4648
We confirmed the defect detection performances of the remote field eddy current testing (RFECT) in order to inspect the helical-coil-type double wall tube steam generator (DWTSG) with the wire mesh layer for the new small fast reactor 4S (Super-Safe, Small and Simple). As the high sensitivity techniques, we tried to increase the direct magnetic field intensity in the vicinity of the inner wall of the tube and decrease the direct magnetic field around the central axis of the tube using the exciter coil with the flux guide made of the iron–nickel alloy. We adopted the horizontal type multiple detector coils with the flux guides arrayed circumferentially to enhance the sensitivity of the radial component. According to the experimental results, the output voltage of the detector coil in the region of indirect magnetic field increased more than 100 times by the application of the exciter and detector coils with the flux guides. Finally, we were able to detect the small hole defect of 1 mm in diameter and 20% of the outer tube thickness in depth over the wire mesh layer by the adoption of the exciter coil and horizontal type multiple detector coils with the flux guides. We also confirmed that the RFECT probe is useful for detecting thinning defects. These experimental results indicated that there is the possibility that we can inspect the double wall tube with the wire mesh layer using the RFECT. 相似文献