全文获取类型
收费全文 | 25052篇 |
免费 | 2167篇 |
国内免费 | 2245篇 |
专业分类
电工技术 | 897篇 |
技术理论 | 2篇 |
综合类 | 2412篇 |
化学工业 | 4426篇 |
金属工艺 | 2361篇 |
机械仪表 | 913篇 |
建筑科学 | 1768篇 |
矿业工程 | 517篇 |
能源动力 | 761篇 |
轻工业 | 2322篇 |
水利工程 | 627篇 |
石油天然气 | 710篇 |
武器工业 | 211篇 |
无线电 | 1853篇 |
一般工业技术 | 6159篇 |
冶金工业 | 1024篇 |
原子能技术 | 410篇 |
自动化技术 | 2091篇 |
出版年
2024年 | 77篇 |
2023年 | 373篇 |
2022年 | 699篇 |
2021年 | 819篇 |
2020年 | 797篇 |
2019年 | 783篇 |
2018年 | 697篇 |
2017年 | 887篇 |
2016年 | 922篇 |
2015年 | 883篇 |
2014年 | 1283篇 |
2013年 | 1768篇 |
2012年 | 1510篇 |
2011年 | 1785篇 |
2010年 | 1402篇 |
2009年 | 1474篇 |
2008年 | 1405篇 |
2007年 | 1490篇 |
2006年 | 1339篇 |
2005年 | 1173篇 |
2004年 | 1043篇 |
2003年 | 862篇 |
2002年 | 755篇 |
2001年 | 657篇 |
2000年 | 642篇 |
1999年 | 521篇 |
1998年 | 471篇 |
1997年 | 391篇 |
1996年 | 351篇 |
1995年 | 338篇 |
1994年 | 287篇 |
1993年 | 215篇 |
1992年 | 242篇 |
1991年 | 206篇 |
1990年 | 187篇 |
1989年 | 130篇 |
1988年 | 104篇 |
1987年 | 72篇 |
1986年 | 68篇 |
1985年 | 70篇 |
1984年 | 69篇 |
1983年 | 40篇 |
1982年 | 41篇 |
1981年 | 21篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1977年 | 14篇 |
1976年 | 9篇 |
1974年 | 10篇 |
1959年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
In this work, ZnO nanostructures are electrodeposited on a transparent conducting glass from chloride baths. The influence of H2O2 concentration on the electrochemical characteristics has been studied using cyclic voltammetry (CV) and chronoamperometry (CA) techniques. From the analysis of the current transients on the basis of the Scharifker–Hills model, it is found that nucleation mechanism is progressive with a typical three-dimensional (3D) nucleation and growth process; independently with the concentration of H2O2. However, the nucleation rate of the ZnO changes with the increase of H2O2 concentration. The Mott–Schottky measurements demonstrate an n-type semiconductor character for all samples with a carrier density varying between 5.14×1018 cm−3 and 1.47×1018 cm−3. Scanning electron microscopy (SEM) observations show arrays of vertically aligned ZnO nanorods (NRs) with good homogeneity. The X-ray diffraction (XRD) patterns show that the ZnO deposited crystallises according to a hexagonal Würtzite-type structure and with the c-axis perpendicular to the electrode surface. The directional growth along (002) crystallographic plane is very important for deposits obtained at 5 and 7 mM of H2O2. The high optical properties of the ZnO NRs with a low density of deep defects was checked by UV–vis transmittance analyses, the band gap energy of films varies between 3.23 and 3.31 eV with transparency around 80–90%. 相似文献
3.
为了减小传统的最差情况设计方法引入的电压裕量,提出了一种变化可知的自适应电压缩减(AVS)技术,通过调整电源电压来降低电路功耗.自适应电压缩减技术基于检测关键路径的延时变化,基于此设计了一款预错误原位延时检测电路,可以检测关键路径延时并输出预错误信号,进而控制单元可根据反馈回的预错误信号的个数调整系统电压.本芯片采用SMIC180 nm工艺设计验证,仿真分析表明,采用自适应电压缩减技术后,4个目标验证电路分别节省功耗12.4%,11.3%,10.4%和11.6%. 相似文献
4.
《Intermetallics》2015
The non-equiatomic FeCoNiAlSi alloy is prepared by the Bridgman solidification (BS) technique at different withdrawal velocities (V = 30, 100, and 200 μm/s). Various characterization techniques have been used to study the microstructure and crystal orientation. The morphological evolutions accompanying the crystal growth of the alloy prepared at different withdrawal velocities are nearly the same, from equiaxed grains to columnar crystals. The transition of coercivity is closely related to the local microstructure, while the saturation magnetization changes little at different sites. The coercivity can be significantly reduced from the equiaxed grain area to the columnar crystal area when the applied magnetic field direction is parallel to the crystal growth direction, no matter what is the withdrawal velocity. In addition, the alloy possesses magnetic anisotropy when the applied magnetic field is in different directions. 相似文献
5.
Fatigue crack growth behaviour of Ti–6Al–2Zr–1.5Mo–1.5V (VT-20 a near-α Ti alloy) was studied in lamellar, bimodal and acicular microstructural conditions. Fatigue crack growth tests at both increasing and decreasing stress intensity factor range values were performed at ambient temperature and a loading ratio of 0.3 using compact tension samples. Lamellar and acicular microstructures showed lower fatigue crack growth rates as compared to the bimodal microstructure due to the tortuous nature of cracks in the former and the cleavage of primary α in the latter. The threshold stress intensity factor range was highest for acicular microstructure. 相似文献
6.
7.
8.
Multifilament Ag-sheathed BiPbSrCaCuO (2223) superconducting tapes containing 49 filaments were fabricated by the powder-in-tube route and the roll-anneal process. The transport critical current densityJ
c
was 1.3×104 A cm–2 at 77 K and 7×104 A cm–2 at 4.2 K in self-field. A 12-m-long tape was used to construct superconducting solenoids (50, 28, and 14 mm internal diameters) generating dc fields 380–1070 G at 4.2 K. Measurements of the variation ofJ
c
with field (0–1.6 T) and bend strain (0–5%) are used to explain the performance of the solenoids. The critical bend strain of tapes was about 1.5%. 相似文献
9.
G
V Vijaya T Gireesh Gajanan S Bhat 《Journal of the science of food and agriculture》2002,82(5):493-496
The effect of enzymatic hydrolysis of proteins in milk using neutrase on the growth of the probiotic strain Bifidobacterium bifidus was evaluated by estimation of microbial growth, acidity, viscosity and flavour production. A significant increase in the growth of B bifidus was observed in neutrase‐hydrolysed milk. The setting time of bifidus‐cultured milk was advanced by about 12 h at 5% degree of hydrolysis. Enzymatic hydrolysis of proteins prior to cultivation also significantly increased the viscosity of the product. An approximately 60% increase in viscosity of the product was observed in neutrase‐hydrolysed milk. Production of steam‐volatile monocarbonyls as an indication of development of flavour was also higher in neutrase‐hydrolysed milk. The concentration of steam‐volatile monocarbonyls was 2.47 µmol per 100 ml in neutrase‐hydrolysed milk but only 1.84 µmol per 100 ml in control milk at the setting point of the curd. © 2002 Society of Chemical Industry 相似文献
10.
1 INTRODUCTIONParticlesreinforcedtitaniumalloymatrixcomposites(TMCp)havewideapplicationfieldsfortheirattractivehighspecificstreng 相似文献