全文获取类型
收费全文 | 1734篇 |
免费 | 29篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 80篇 |
综合类 | 3篇 |
化学工业 | 338篇 |
金属工艺 | 36篇 |
机械仪表 | 29篇 |
建筑科学 | 22篇 |
能源动力 | 73篇 |
轻工业 | 145篇 |
水利工程 | 2篇 |
无线电 | 155篇 |
一般工业技术 | 295篇 |
冶金工业 | 381篇 |
原子能技术 | 64篇 |
自动化技术 | 143篇 |
出版年
2022年 | 14篇 |
2021年 | 14篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 16篇 |
2017年 | 13篇 |
2016年 | 14篇 |
2015年 | 12篇 |
2014年 | 27篇 |
2013年 | 73篇 |
2012年 | 56篇 |
2011年 | 79篇 |
2010年 | 55篇 |
2009年 | 56篇 |
2008年 | 52篇 |
2007年 | 65篇 |
2006年 | 58篇 |
2005年 | 58篇 |
2004年 | 51篇 |
2003年 | 58篇 |
2002年 | 54篇 |
2001年 | 48篇 |
2000年 | 35篇 |
1999年 | 29篇 |
1998年 | 148篇 |
1997年 | 86篇 |
1996年 | 80篇 |
1995年 | 48篇 |
1994年 | 42篇 |
1993年 | 55篇 |
1992年 | 28篇 |
1991年 | 24篇 |
1990年 | 22篇 |
1989年 | 21篇 |
1988年 | 22篇 |
1987年 | 14篇 |
1986年 | 20篇 |
1985年 | 24篇 |
1984年 | 17篇 |
1983年 | 19篇 |
1982年 | 22篇 |
1981年 | 22篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1978年 | 15篇 |
1977年 | 19篇 |
1976年 | 16篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1967年 | 3篇 |
排序方式: 共有1766条查询结果,搜索用时 0 毫秒
71.
Xiong Wei Wu Tomoo Yamamura Suguru Ohta Qi Xiu Zhang Fu Cong Lv Can Ming Liu Kenji Shirasaki Isamu Satoh Tatsuo Shikama Dan Lu Su Qin Liu 《Journal of Applied Electrochemistry》2011,41(10):1183-1190
The redox kinetics of VO2+/VO2 + and V3+/V2+ couples on a carbon paper (CP, HCP030 N, Shanghai Hesen, Ltd., China) electrode were investigated in terms of their standard rate constant (k 0) and reaction mechanism. The values determined for k 0 for VO2+ ?? VO2 + and V3+ ?? V2+ using the CP electrode are 1.0 × 10?3 and 1.1 × 10?3 cm s?1, respectively. The value of k 0 increases by one or two order(s) of magnitude compared with values obtained using electrodes composed of pyrolytic graphite and glassy carbon. The acceleration of the redox kinetics of vanadium ions is a result of the large surface area of the CP electrode. An inner-sphere mechanism for the reaction on the surface of the electrode is proposed. The kinetic features of vanadium redox reactions on the CP electrode reveal that CP is suitable for use as the electrodes in vanadium redox-flow batteries. 相似文献
72.
Corrosion characteristics of reduced activation ferritic steel, JLF-1 (8.92Cr–2W) in molten salts Flibe and Flinak 总被引:1,自引:0,他引:1
Masatoshi Kondo Takuya Nagasaka Qi Xu Takeo Muroga Akio Sagara Nobuaki Noda Daisuke Ninomiya Masaru Nagura Akihiro Suzuki Takayuki Terai Naoki Fujii 《Fusion Engineering and Design》2009,84(7-11):1081-1085
Static corrosion tests were performed in molten salts, LiF–BeF2 (Flibe) and LiF–NaF–KF (Flinak), at 500 °C and 600 °C for 1000 h. The purpose is to investigate the corrosion characteristics of reduced activation ferritic steels, JLF-1 (8.92Cr–2W) in the fluids. The concentration of hydrogen fluoride (HF) in the fluids was measured by slurry pH titration method before and after the exposure. The HF concentration determined the fluoridation potential. The corrosion was mainly caused by dissolution of Fe and Cr into the fluids due to fluoridation and/or electrochemical corrosion. Carbon on the surface might be dissolved into the fluids due to the corrosion, and this resulted to the decrease of carbide on the surface. The corrosion depth of the JLF-1 specimen, which was obtained from the weight losses, was 0.637 μm in Flibe at 600 °C and 6.73 μm in Flinak at 600 °C. 相似文献
73.
Developmental ability of cloned embryos from neural stem cells 总被引:2,自引:0,他引:2
Mizutani E Ohta H Kishigami S Van Thuan N Hikichi T Wakayama S Kosaka M Sato E Wakayama T 《Reproduction (Cambridge, England)》2006,132(6):849-857
The success rate is generally higher when cloning mice from embryonic stem (ES) cell nuclei than from somatic cell nuclei, suggesting that the embryonic nature or the undifferentiated state of the donor cell increases cloning efficiency. We assessed the developmental ability of cloned embryos derived from cultured neural stem cell (NSC) nuclei and compared the success rate with that of embryos cloned from other donor cells such as differentiated NSCs, cumulus cells, Sertoli cells and ES cells in the mouse. The transfer of two-cell cloned embryos derived from cultured NSC nuclei into surrogate mothers produced five live cloned mice. However, the success rate (0.5%) was higher in embryos cloned from cultured NSC nuclei than from differentiated NSCs (0%), but lower than that obtained by cloning mice from other cell nuclei (2.2-3.5%). Although the in vitro developmental potential to the two-cell stage of the cloned embryos derived from NSC nuclei (73%) was similar to that of the cloned embryos derived from other somatic cell nuclei (e.g., 85% in Sertoli cells and 75% in cumulus cells), the developmental rate to the morula-blastocyst stage was only 7%. This rate is remarkably lower than that produced from other somatic cells (e.g., 50% in Sertoli cells and 54% in cumulus cells). These results indicate that the undifferentiated state of neural cells does not enhance the cloning efficiency in mice and that the arrest point for in vitro development of cloned embryos depends on the donor cell type. 相似文献
74.
Volatiles were extracted from rice plants of various growth stages with solid-phase microextraction (SPME) and analyzed by
gas chromatography-mass spectrometry (GC-MS) to identify attractants that cause invasion of the rice leaf bug Trigonotylus caelestialium (Kirkaldy) into paddy fields. The composition of volatile blends produced by rice plants changed with rice development. In
addition, volatile blend compositions differed between the panicles and the stems and leaves. The relative geranyl acetone
content was high in all plant structures analyzed. In volatiles from whole plants in the fourth-leaf stage and panicles in
the full-ripe stage, the relative content of green leaf volatiles (GLVs) was higher than that found in other rice plant structures.
In contrast, relative terpene levels emitted from whole plants in the panicle-formation stage and by panicles and stems and
leaves in the flowering stage were higher than those of other rice plant structures. However, the type of terpenes found differed
between the panicles and the stems and leaves. Relative levels of β-caryophyllene in whole plants in the panicle-formation
stage and panicles in the flowering stage were much higher than that in stems and leaves in the flowering stage. Our previous
studies demonstrated that the odor from whole plants in the panicle-formation stage and panicles in the flowering stage is
attractive to rice leaf bugs. Here, the attractiveness of β-caryophyllene to adult bugs was investigated in olfactometer assays.
Adult females were attracted to β-caryophyllene at a concentration of 0.001%, which is approximately equivalent to the concentration
produced by flowering rice panicles. However, β-caryophyllene also was present in the odor of whole plants in the fourth-leaf
stage and in stems and leaves in the flowering stage. Furthermore, the amounts of this compound emitted from these structures
were similar. Therefore, we suggest that the relative abundance of this compound in a volatile blend is important for attractance
of the bugs. 相似文献
75.
Michio Tajima Masatoshi Ikebe Yoshio Ohshita Atsushi Ogura 《Journal of Electronic Materials》2010,39(6):747-750
We investigated the effect of Fe contamination on the electronic properties of dislocation clusters in relation to oxygen
precipitation in multicrystalline silicon (mc-Si). Photoluminescence (PL) spectroscopy and mapping were performed at room
and liquid-He temperatures on mc-Si wafers before and after Fe contamination. PL spectra consisted of the band-edge emission,
the 0.78-eV emission associated with oxygen precipitates, and the dislocation-related D-lines. The Fe contamination increased
the electrically active dislocation clusters. Part of these clusters acted as preferential oxygen precipitation sites, and
their electronic properties were not further influenced by the Fe contamination. 相似文献
76.
K. Kainosho M. Ohta M. Uchida M. Nakamura O. Oda 《Journal of Electronic Materials》1996,25(3):353-356
Recently, it was found that undoped semi-insulating InP can be obtained by highpressure annealing of high purity materials.
The reproducibility and the uniformity was, however, not satisfactory. In the present work, we found that not only Fe concentrations
but also Cr and Ni concentrations in annealed wafers were slightly increased during annealing. Since it seems that the origin
of the contamination was due to the vapor source of red phosphorus, conductive InP with a trace amount of Fe was annealed
under low phosphorus vapor pressure in order to reduce the contamination. By preventing the contamination of Cr and Ni, preparation
of semi-insulating InP became highly reproducible. The minimum Fe concentration for realizing semi-insulating InP was found
to be 1 x 1015cm−3. It was also found that the better resistivity uniformity can be obtained at higher annealing temperatures. 相似文献
77.
78.
79.
Masaki Oiwa Shunsuke Minami Kenichiro Tsuji Noriaki Onodera Masatoshi Saruwatari 《Optical Fiber Technology》2010,16(4):192-204
We theoretically and experimentally study the all-optical clock recovery performance using the primary or the secondary temporal Talbot effects (PTTE or STTE, respectively) in a dispersive medium having the first-order dispersion together with the second-order dispersion (e.g., conventional single-mode fibers: SMFs). Our preliminary numerical simulations have indicated that the STTE-based all-optical clock recovery technique can improve double its performance as compared with the conventional PTTE-based technique when the second-order dispersion (dispersion slope) can be neglected. The following simulation results have revealed that the second-order dispersion, that the normal SMFs possess, limits the performance improvements in the STTE-based clock recovery, whereas the limited performance can be improved by appropriately compensating for the second-order dispersion. On the basis of our simulation results, experiments of the STTE-based clock recovery were conducted by compensating for the second-order dispersion of SMFs used as dispersive media. To be specific, SMFs’ second-order dispersion has been reduced to the one-sixteenth of its original value by combining with the reverse-dispersion fibers (RDFs) which can provide the second-order dispersion of the opposite sign to the SMFs. As a result, the performance improvements in the STTE-based clock recovery was demonstrated so that the 10-GHz clear optical clock pulses were successfully recovered from 10-Gbit/s return-to-zero (RZ) pseudo-random bit sequence (PRBS) optical signals. 相似文献
80.
Masayuki Ohta Keitaro Kondo Masayuki Matsunaka Hiroyuki Miyamaru Isao Murata Toshiyuki Iida Kentaro Ochiai Chikara Konno 《Fusion Engineering and Design》2009,84(7-11):1446-1449
Integral benchmark experiments with DT neutrons are not always sufficient for nuclear data benchmarking in the MeV region, below 10 MeV. A neutron spectrum shifter, which will be placed between a sample and a DT neutron source, is effective to moderate DT neutrons incident to the sample. In order to estimate effects of the spectrum shifter, the ratio of the contribution of 14 MeV neutrons in the leakage neutron and gamma-ray spectra was calculated with MCNP-4C for an experimental configuration at FNS of JAEA, Japan. The calculations were carried out for a Li2TiO3 sample with a Be, D2O, or 7LiD spectrum shifter. It was found out that the Be shifter was superior to others and the Be shifter was effective to decrease the contribution of 14 MeV neutrons especially for secondary gamma-ray spectrum measurements. 相似文献