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991.
Stable p-type conductivity and enhanced photoconductivity from nitrogen-doped annealed ZnO thin film
Soumen DharaP.K. Giri 《Thin solid films》2012,520(15):5000-5006
We report on the growth of p-type ZnO thin films with improved stability on various substrates and study the photoconductive property of the p-type ZnO films. The nitrogen doped ZnO (N:ZnO) thin films were grown on Si, quartz and alumina substrates by radio frequency magnetron sputtering followed by thermal annealing. Structural studies show that the N:ZnO films possess high crystallinity with c-axis orientation. The as-grown films possess higher lattice constants compared to the undoped films. Besides the high crystallinity, the Raman spectra show clear evidence of nitrogen incorporation in the doped ZnO lattice. A strong UV photoluminescence emission at ~ 380 nm is observed from all the N:ZnO thin films. Prior to post-deposition annealing, p-type conductivity was found to be unstable at room temperature. Post-growth annealing of N:ZnO film on Si substrate shows a relatively stable p-type ZnO with room temperature resistivity of 0.2 Ω cm, Hall mobility of 58 cm2/V s and hole concentration of 1.95 × 1017 cm− 3. A homo-junction p-n diode fabricated on the annealed p-type ZnO layer showed rectification behavior in the current-voltage characteristics demonstrating the p-type conduction of the doped layer. Doped ZnO films (annealed) show more than two orders of magnitude enhancement in the photoconductivity as compared to that of the undoped film. The transient photoconductivity measurement with UV light illumination on the doped ZnO film shows a slow photoresponse with bi-exponential growth and bi-exponential decay behaviors. Mechanism of improved photoconductivity and slow photoresponse is discussed based on high mobility of carriers and photodesorption of oxygen molecules in the N:ZnO film, respectively. 相似文献
992.
993.
994.
I-Tai WangJenq-Gong Duh Chih-Yuan ChengJim Wang 《Materials Science and Engineering: B》2012,177(2):278-282
Sn3.0Ag0.5Cu solder doped with 0, 100, and 500 ppm Pd was reflowed with electroless Ni/immersion Au substrate. As Pd concentration increased in the solder, formation and growth of (Cu,Ni)6Sn5 were suppressed. After thermal aging, Cu4Ni2Sn5 and Cu5NiSn5 were observed at interface of Sn3.0Ag0.5Cu-xPd/Au/Ni systems. As compared to Cu4Ni2Sn5, more Pd dissolved in Cu5NiSn5. In addition, Pd doping enhanced the growth of Cu4Ni2Sn5 and slowed the formation of Cu5NiSn5, which would stabilize the intermetallic compound. Based on quantitative analysis by field emission electron probe microanalyzer, the correlation between Pd doping and elemental redistribution in solder joints was probed and discussed. This study described a possible mechanism of the formation of different intermetallic compounds in Pd-doped lead-free solder. 相似文献
995.
Geskus D Aravazhi S García-Blanco SM Pollnau M 《Advanced materials (Deerfield Beach, Fla.)》2012,24(10):OP19-OP22
Modal gain per unit length versus launched pump power is predicted and measured in a 47.5 at.% Yb(3+) -doped potassium double tungstate channel waveguide. The highest measured gain exceeds values previously reported for rare-earth-ion-doped materials by two orders of magnitude. 相似文献
996.
Converting graphene oxide monolayers into boron carbonitride nanosheets by substitutional doping 总被引:1,自引:0,他引:1
Lin TW Su CY Zhang XQ Zhang W Lee YH Chu CW Lin HY Chang MT Chen FR Li LJ 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(9):1384-1391
To realize graphene-based electronics, bandgap opening of graphene has become one of the most important issues that urgently need to be addressed. Recent theoretical and experimental studies show that intentional doping of graphene with boron and nitrogen atoms is a promising route to open the bandgap, and the doped graphene might exhibit properties complementary to those of graphene and hexagonal boron nitride (h-BN), largely extending the applications of these materials in the areas of electronics and optics. This work demonstrates the conversion of graphene oxide nanosheets into boron carbonitride (BCN) nanosheets by reacting them with B(2) O(3) and ammonia at 900 to 1100 °C, by which the boron and nitrogen atoms are incorporated into the graphene lattice in randomly distributed BN nanodomains. The content of BN in BN-doped graphene nanosheets can be tuned by changing the reaction temperature, which in turn affects the optical bandgap of these nanosheets. Electrical measurements show that the BN-doped graphene nanosheet exhibits an ambipolar semiconductor behavior and the electrical bandgap is estimated to be ≈25.8 meV. This study provides a novel and simple route to synthesize BN-doped graphene nanosheets that may be useful for various optoelectronic applications. 相似文献
997.
Guo XH Mao CC Zhang J Huang J Wang WN Deng YH Wang YY Cao Y Huang WX Yu SH 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(10):1515-1520
High-quality cobalt-doped ceria nanostructures with triangular column, triangular slab, and disklike shapes are synthesized by tuning the doping amount of cobalt nitrate in a facile hydrothermal reaction. The cobalt-doped ceria nanodisks display significantly enhanced catalytic activity in CO oxidation due to exposed highly active crystal planes and the presence of numerous surface defects. 相似文献
998.
999.
为改善Na0.5Bi0.5TiO3材料的电性能,采用溶胶-凝胶法制备了Na0.5Bi0.5TiO3粉体.通过液相Ce掺杂和气相Ce扩渗两种方法,对Na0.5Bi0.5TiO3粉体进行了改性,采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、阻抗分析仪和电阻仪对改性前后Na0.5Bi0.5TiO3粉体的组成、结构和电性能的变化进行了研究.结果表明:Ce元素的添加有助于Na0.5Bi0.5TiO3粉体电阻率的降低,而扩渗改性使电阻率的降低更为显著,经600℃扩渗的Na0.5Bi0.5TiO3粉体的电阻率由3.71×106Ω.m降至2.39×101Ω.m;稀土Ce掺杂使Na0.5Bi0.5TiO3的介电常数减小,而Ce扩渗使Na0.5Bi0.5TiO3的介电常数显著增大;Ce掺杂使粒径更加均匀,而随着气相扩渗温度的提高,晶粒粒径逐渐变大;Ce掺杂没有改变Na0.5Bi0.5TiO3的主晶相结构,但Na0.5Bi0.5TiO3粉体经Ce扩渗后,出现了单质Bi及Bi2Ti2O7、Na2Ti9O19、Na2Ti6O13的特征峰. 相似文献
1000.
以Li2CO3、B2O3和V2O53种常见的低熔点氧化物为烧结助剂,用传统固相法制备了Li2CO3-B2O3-V2O5掺杂的ZnO-TiO2微波介质陶瓷,并利用XRD、SEM等研究了ZnO-TiO2陶瓷的烧结行为、物相组成、显微结构特征及微波介电性能等。结果表明,当掺入3%(质量分数)Li2CO3-B2O3-V2O5时,在840℃烧结2h可制备出体积密度为4.99g/cm3的ZnO-TiO2陶瓷,达到理论密度的96.5%以上,εr、Q.f、τf分别约为24、22900GHz、-4×10-6/℃。 相似文献