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91.
《Ergonomics》2012,55(5):1025-1035
Abstract Several studies indicate that the ISO standards for school furniture seem to be inappropriate, and there is increasing evidence that the inclination of the seat should be forward and that it should be possible to adjust the table-top to a certain non-horizontal angle. However, these studies have predominantly used objective measurement methods on adult subjects for short-term experiments in rather artificial surroundings. By means of structured interviews registering the school children's perception of ergonomic comfort, the present study has compared three types of school furniture—the original ISO-standard type, and two different new types characterized by forward slanting seats and tiltable desk-tops, the main difference between the two being approximately 15 cm in the height of the chair as well as the table. The study showed that the highest of the two tilting types was perceived to be significantly better than the two others in terms of table height, chair height, reading position, back-rest, and global assessment. Likewise, the feature of a tiltable table-top was considered overwhelmingly positive independently of the height of the furniture. It is recommended that school authorities, producers of school furniture, and relevant medical personnel consider these results for alternative designs of school furniture. It should be kept in mind, however, that school furniture is only one among many factors in the multifactorial field of the back health of school children. 相似文献
92.
尾板对重型载货汽车尾部流场的影响 总被引:1,自引:0,他引:1
为了降低风的阻力,对某牵引式重型载货汽车加装了4种不同形式和尺寸的尾板。并采用数值仿真的方法分析了尾板对流场的影响,探索了风阻产生机理和降低原因。仿真工况模拟正常车辆行驶速度25m/s,未考虑侧风影响。计算结果表明:安装4种尾板后风阻系数均有降低,降幅最大为2.8%,获得了较满意的降阻效果。对比分析了4种方案的整车气动阻力系数、流速分布及总压为零等值面的计算结果。研究发现:尾板对车身周围气流的影响集中在货箱尾部,改变了尾流中原有的环形漩涡结构,从而降低了风阻。 相似文献
93.
为探索一种简单易行、精度良好的砌体墙板开裂模式预测方法,建立了一个预测面外均布荷载下砌体墙板开裂模式的支持向量机方法:对砌体墙板试验开裂模式进行特征提取,获取开裂模式先验知识;对提取的开裂模式特征进行数值化定义,得到描述开裂模式的特征值;应用支持向量机学习这些试验墙板开裂模式的特征值;应用学习/训练后的支持向量机模型,对新墙板进行开裂模式的预测.对该支持向量机方法的验证,分别考察了3种情况:三边支撑墙板、四边支撑墙板、混合两种支撑的墙板.结果表明所建立的支持向量机方法,能够基于试验墙板开裂模式,较精确地预测新墙板开裂模式. 相似文献
94.
以Zn-22Al(ZA22)基泡沫材料为芯材,LY12铝板为面板制备了泡沫夹芯复合板。研究了泡沫夹芯复合板的三点弯曲行为,观察了复合板的破坏模式,分析了复合板弯曲性能的影响因素,运用层合梁刚度优化理论探讨了其机理。研究结果表明,ZA22泡沫夹芯复合板的三点弯曲载荷-位移曲线可按线性段、非线性段和失稳段表示其特征;其弯曲极限载荷随孔隙率的增大而减小,并且泡沫夹芯复合板表现出明显的层合效果。三点弯曲载荷作用下,泡沫夹芯复合板的主要失效模式为芯材的剪切破坏。 相似文献
95.
96.
Mahdi Ghasemi-Varnamkhasti Seyed Saeid MohtasebiMaria Luz Rodriguez-Mendez Jesus LozanoSeyed Hadi Razavi Hojat AhmadiConstantin Apetrei 《Expert systems with applications》2012,39(4):4315-4327
Sensory evaluation is the application of knowledge and skills derived from several different scientific and technical disciplines, physiology, chemistry, mathematics and statistics, human behavior, and knowledge about product preparation practices. This research was aimed to evaluate aftertaste sensory attributes of commercial non-alcoholic beer brands (P1, P2, P3, P4, P5, P6, P7) by several chemometric tools. These attributes were bitter, sour, sweet, fruity, liquorice, artificial, body, intensity and duration. The results showed that the data are in a good consistency. Therefore, the brands were statistically classified in several categories. Linear techniques as Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) were performed over the data that revealed all types of beer are well separated except a partial overlapping between zones corresponding to P4, P6 and P7. In this research, for the confirmation of the groups observed in PCA and in order to calculate the errors in calibration and in validation, PLS-DA technique was used. Based on the quantitative data of PLS-DA, the classification accuracy values were ranked within 49-86%. Moreover, it was found that the classification accuracy of LDA was much better than PCA. It shows that this trained sensory panel can discriminate among the samples except an overlapping between two types of beer. Also, two types of artificial networks were used: Probabilistic Neural Networks (PNN) with Radial Basis Functions (RBF) and FeedForward Networks with Back Propagation (BP) learning method. The highest classification success rate (correct predicted number over total number of measurements) of about 97% was obtained for RBF followed by 94% for BP. The results obtained in this study could be used as a reference for electronic nose and electronic tongue in beer quality control. 相似文献
97.
由纸蜂窝和玻璃布面板制成的蜂窝夹层板具有质轻、比强度高、隔音、隔热和防潮等特点,是一种极有前途的新型建筑材料,研制了一种具有成本低、污染小、阻燃等特点,可满足建筑用蜂窝板的制造工艺和使用性能要求的胶粘剂。 相似文献
98.
99.
Vacuum insulation panels (VIPs) have a thermal resistance that is about a factor of 10 higher than that of equally thick conventional polystyrene boards. VIPs nowadays mostly consist of a load-bearing kernel of fumed silica. The kernel is evacuated to below 1 mbar and sealed in a high- barrier laminate, which consists of several layers of Al-coated polyethylene (PE) or polyethylene terephthalate (PET). The laminate is optimized for extremely low leakage rates for air and moisture and thus for a long service life, which is required especially for building applications. The evacuated kernel has a thermal conductivity of about 4 × 10−3 W · m−1 · K−1 at room temperature, which results mainly from solid thermal conduction along the tenuous silica backbone. A U-value of 0.2 W · m−2 · K−1 results from a thickness of 2 cm. Thus slim, yet highly insulating fa?ade constructions can be realized. As the kernel has nano-size pores, the gaseous thermal conductivity becomes noticeable only for pressures above 10 mbar. Only above 100 mbar the thermal conductivity doubles to about 8 × 10−3 W · m−1 · K−1, such a pressure could occur after several decades of usage in a middle European climate. These investigations revealed that the pressure increase is due to water vapor permeating the laminate itself, and to N2 and O2, which tend to penetrate the VIP via the sealed edges. An extremely important innovation is the integration of a thermo-sensor into the VIP to nondestructively measure the thermal performance in situ. A successful “self-trial” was the integration of about 100 hand-made VIPs into the new ZAE-building in Würzburg. Afterwards, several other buildings were super-insulated using VIPs within a large joint R&D project initiated and coordinated by ZAE Bayern and funded by the Bavarian Ministry of Economics in Munich. These VIPs were manufactured commercially and integrated into floorings, the gable fa?ade of an old building under protection, the roof and the facades of a terraced house as well as into an ultra-low-energy “passive house” and the slim balustrade of a hospital. The thermal reliability of these constructions was monitored using an infrared camera.Invited paper presented at the Seventh European Conference on Thermophysical Properties, September 5-8, 2005, Bratislava, Slovak Republic. 相似文献
100.
Jeong-Ryeol Kim Geun-Kyu Choi Dong Kyun Yim Jong-Sung Park Kug Sun Hong 《Journal of Electroceramics》2006,17(1):65-69
Glasses in the ZnO-B2O3-MO3(M = W, Mo) ternary were examined as potential replacements to PbO-B2O3-SiO2-ZnO glass frits with the low firing temperature (500–600∘C) for the dielectric layer of a plasma display panels (PDPs). Glasses were melted in air at 950–1150∘C in a narrow region of the ternary using standard reagent grade materials. The glasses were evaluated for glass transition
temperature (T
g
), softening temperature (T
d
), the coefficient of thermal expansion (CTE), dielectric constant (ε
r
), and optical property. The glass transition temperature of the glasses varied between 470 and 560∘C. The coefficient of thermal expansion and the dielectric constant of the glasses were in the range of 5–8 × 10− 6/∘C and 8–10, respectively. The addition of MO3to ZnO-B2O3binary could induce the expansion of glass forming region, the reduction of T
g
and the increase in the CTE and the dielectric constant of the glasses. Also, the effect of the addition of MO3to ZnO-B2O3binary on the transmittance in the visible-light region (350–700 nm) was investigated. 相似文献