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1.
Pervaporation (PV) is a membrane technology that holds great promise for industrial applications. To better understand the PV mechanism, PV dehydrations of various types of organic solvents (methanol, ethanol, iso-propanol, tert-butanol, and acetone) were performed on five types of organosilica and two types of silicon carbide-based membranes, all with different pore sizes. Water permeance was dependent on the types of organic aqueous solutions, which suggested that organic solvents penetrated the pores and hindered the permeation of water. In addition, water permeance of various types of membranes in PV was well correlated with hydrogen permeance in single-gas permeation. Furthermore, a clear correlation was obtained between the permeance ratio in PV and that in single-gas permeation, which was confirmed via the modified-gas translation model. These correlations make it possible to use single-gas permeation properties to predict PV performance.  相似文献   
2.
The damage induced in 3C-SiC epilayers on a silicon wafer by 2.3-MeV Si ion irradiation for fluences of 1014, 1015, and 1016 cm−2, was studied by conventional and high-resolution transmission electron microscopy (TEM/HRTEM). The evolution of extended defects and lattice disorder is followed in both the 3C-SiC film and Si substrate as a function of ion fluence, with reference to previous FTIR spectroscopy data. The likelihood of athermal unfaulting of native stacking faults by point defect migration to the native stacking faults is discussed in relation to damage recovery. Threshold energy densities and irradiation doses for dislocation loop formation and amorphous phase transformation are deduced from the damage depth profile by nuclear collisions. The role of electronic excitations on the damage recovery at high fluence is also addressed for both SiC and Si.  相似文献   
3.
采用复合溶胶–凝胶法结合后续热处理,制备了具有包埋结构的氧化亚硅/碳(SiOx/C)复合负极材料。扫描电子显微镜分析结果表明:氧化亚硅纳米颗粒嵌入在无定形碳中。电化学性能测试表明:SiOx/C复合材料具有较高的比容量、优异的循环稳定性和倍率性能。材料在0.1 A/g的电流密度下100次循环后的可逆比容量为710 m A·h/g,容量几乎无衰减;在1.6 A/g的电流密度下,可逆比容量为380 m A·h/g。优异的电化学性能是由于材料的包埋结构能有效地缓冲SiOx充放电过程中的体积膨胀,保证材料的结构完整性和电化学循环稳定性。  相似文献   
4.
Hi Nicalon, Hi Nicalon S, Sylramic, and Sylramic iBN SiC fibers were exposed to ~60 μg/cm2 of Na2SO4 in a 0.1% SO2/O2 gaseous environment for times between 0.75 and 24 h at 1000°C. After exposure, the corrosion products were characterized using SEM, EDS, ICP-OES, TEM, and EFTEM to determine their high-temperature resistance to Na2SO4 and key reaction mechanisms. All SiC fiber types tested in this work exhibited little resistance to Na2SO4 deposit-induced attack relative to their behavior in dry O2 environments. It was found that Hi-Nicalon displayed the least resistance to Na2SO4 deposit-induced attack due to excess carbon content resulting in the formation of a highly porous crystalline oxide and promotion of basic corrosion conditions. All fiber types formed a crystalline SiO2 reaction product, either cristobalite or tridymite. Sylramic and Sylramic iBN formed a crystalline SiO2 reaction layer containing TiO2 needles due oxidation of TiB2 particles. Additionally, Na2SO4 deposits resulted in pitting of all fiber surfaces.  相似文献   
5.
在多晶硅太阳能电池的生产过程中, 金刚线切割技术(Diamond wire sawn, DWS)具有切割速度快、精度高、原材料损耗少等优点, 受到了广泛关注。金刚线切割多晶硅表面形成的损伤层较浅, 与传统的酸腐蚀制绒技术无法匹配, 金属催化化学腐蚀法应运而生。金属催化化学腐蚀法制绒具有操作简单、结构可控且易形成高深宽比的绒面等优点, 具有广阔的应用前景。本文总结了不同类型的金属催化剂在制绒过程中的腐蚀机理及其形成的绒面结构, 深入分析和讨论了具有代表性的银、铜的单一及复合催化腐蚀过程及绒面结构和电池片性能。最后对金刚线切割多晶硅片表面的金属催化化学腐蚀法存在的问题进行了分析, 并展望了未来的研究方向。  相似文献   
6.
《Ceramics International》2021,47(23):33353-33362
High thermal conductivity Si3N4 ceramics were fabricated using a one-step method consisting of reaction-bonded Si3N4 (RBSN) and post-sintering. The influence of Si content on nitridation rate, β/(α+β) phase rate, thermal conductivity and mechanical properties was investigated in this work. It is of special interest to note that the thermal conductivity showed a tendency to increase first and then decrease with increasing Si content. This experimental result shows that the optimal thermal conductivity and fracture toughness were obtained to be 66 W (m K)-1 and 12.0 MPa m1/2, respectively. As a comparison, the nitridation rate and β/(α+β) phase rate in a static pressure nitriding system, i.e., 97% (MS10), 97% (MS15), 97% (MS20) and 8.3% (MS10), 8.3% (MS15), 8.9% (MS20), respectively, have obvious advantages over those in a flowing nitriding system, i.e., 91% (MS10), 91% (MS15), 93% (MS20) and 3.1% (MS10), 3.3% (MS15), 3.3% (MS20), respectively. Moreover, high lattice integrity of the β-Si3N4 phase was observed, which can effectively confine O atoms into the β-Si3N4 lattice using MgO as a sintering additive. This result indicates that one-step sintering can provide a new route to prepare Si3N4 ceramics with a good combination of thermal conductivity and mechanical properties.  相似文献   
7.
To achieve the balance between mechanical properties and electromagnetic wave-transparent properties of porous silicon nitride (Si3N4), the key is to form an interlocking microstructure constituted by columnar β-Si3N4 crystals. This structure can be realized by liquid-phase sintering. However, grain boundaries which affect high temperature properties and volume shrinkage during sintering are inevitable. We proposed a strategy to realize this structure by gel-casting of β-Si3N4 whisker (Si3N4w) and Si powder followed by in-situ nitridation of Si. To achieve chemically-stable slurry containing micro-sized Si with low viscosity, a novel formulation was developed. Two key structural parameters of the interlocking Si3N4w network, i.e., density of the Si3N4w skeleton and inter-whisker bonding mode, were adjusted by composition of raw materials and nitridation temperature. The flexural strength, dielectric constant and loss of the porous ceramics are 44.9 MPa, 2.7 and 2 × 10−3, when the volume fraction of Si3N4w/Si is 5 and the nitriding temperature is 1400 °C.  相似文献   
8.
The highly porous Si3N4 ceramic foams were prepared by direct foaming with mixed surfactants. The surface tension and viscosity of slurries were tailored by different carbon chain length of surfactants and different mean Si3N4 particle size to achieve the pore size controlling. The nearly linear relationship between the pore size and the ratio of surface tension to viscosity was observed, which indicates that the pore size could be precisely tailored by the slurry properties. Si3N4 ceramic foams with porosity of nearly 94%, mean pore size of 110–230 µm, and compressive strength of 1.24–3.51 MPa were obtained.  相似文献   
9.
研究了高硅铝硅合金(45wt% Si)熔体电磁分离过程中,Sb添加量、下拉速率、温度等对分离效果的影响,对Sb在高硅铝硅合金电磁分离过程中的变质机理进行了分析。结果表明,在1500℃、下拉速率为10 μm/s时,过共晶铝硅合金熔体中加入Sb进行定向凝固后,合金部分硅铝比从11.53%降至11.21%,初晶硅富集区的硅含量从86wt%增至90wt%;当1500℃、下拉速率为40 μm/s时,合金部分硅铝比从12.56%降至12.13%,初晶硅富集区的硅含量从81wt%增至86.5wt%;加入变质剂后合金部分共晶硅相在α-Al基体中分布均匀且连续,形貌有所细化。  相似文献   
10.
基于硅介质柱型光子晶体,采用时域有限差分方法(FDTD),探究高斯光束在光子晶体界面的逆古斯汉欣(GH)位移。通过在光子晶体下表面添加硅透镜,研究高斯光束的入射角度、硅透镜的曲率半径以及温度对光子晶体逆GH位移的影响。研究结果表明,发生最大逆GH位移的角度大于几何理想全反射角。添加焦点位于光子晶体表面中心的硅透镜可以使逆GH位移显著增强,且当硅透镜的曲率半径为170时,逆GH位移增大为不加透镜时的1.7倍。研究不同入射角度下温度对光子晶体的逆GH位移的影响发现,当高斯光束的入射角为26o时,逆GH位移随着温度的变化最大且线性度较好,便于温度监测。  相似文献   
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