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151.
Experimental work was carried out to investigate the rheological properties of bitumen in water emulsions containing solids of different shape and size. The bitumen volumetric concentration was varied up to 60%, solids free basis, and the solids volume fraction (total volume basis) was varied up to 0.2. Irregular-shaped silica sand (average diameter: 9 and 33 μm) and smooth spherical glass beads (average diameter: 27 and 44 μm) were used as the added solids. In the low shear stress range, shear thinning behavior was observed for bitumen in water emulsions. At high shear stress, the viscosity of the emulsions became fairly independent of the shear stress. The addition of solids to the bitumen emulsions increased the mixture viscosity. The addition of irregular-shaped silica sand gave a higher viscosity than a similar addition of the spherical glass beads. The viscosity of the emulsion/solids mixtures was influenced by the solids size as well; the smaller size particles gave a higher viscosity. The addition of solids to the bitumen emulsions also induced shear thickening (dilatancy) behavior at high solids volume fraction. The degree of the shear thickening increased with the oil concentration. 相似文献
152.
This work presents experimental results on pickup velocity (critical velocity) measurements for a variety of particulate solids. The present experiments together with previously published experiments of a number of researchers encompass about 100 measurements of 24 materials for a wide range of particle sizes, shapes and densities. Based on the experimental results, three zones are defined by establishing simple relationships between the Reynolds and Archimedes numbers. The empirical relationships were further modified by taking into account the pipe diameter and particle shape (sphericity). The three-zone model was shown to reasonably correlate to Geldart's classification groups. 相似文献
153.
为了提高车门静态刚度, 采用基于HDMR理论的多参数解耦优化方法与Morph技术结合, 对一款处于概念设计阶段车门的主截面形状进行优化。这种建模方法的特点在于通过少量的样本点识别形状变量之间的耦合关系, 进而将高维问题进行分解, 在保证精度的前提下提高计算效率。采用Kriging插值方法对Cut-HDMR的各项进行构造, 得到车门各刚度下的考察点位移和质量的近似模型, 进而利用非支配排序多目标遗传算法(NSGA-Ⅱ)对近似模型进行优化, 在车门静态刚度均达到设计要求的前提下合理进行减重, 使垂直刚度和扭转刚度得到了很大的提高。 相似文献
154.
Different types of solid bodies (particles) with specific shape and size are needed for industrial processes. For spherical particles, ‘sizer’ measurements are usually reported as sphere diameters. For non-spherical particles, particle shape and especially orientation must be taken into account. Particles of a specific shape will present different views when looked at from different directions.We have employed a Camsizer® instrument to measure the distribution of projected area under different physical conditions for solid cylindrical particles:
- •
- Under ‘ideal’ conditions, corresponding to a uniform distribution of particle orientation, measurements agreed with predictions. The celebrated theorem of Cauchy applies only to this case.
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- For two other situations, measured and predicted results differed. However, from the experimental data it was possible to infer the particle orientations and hence theoretically predict the projected area distribution. Excellent agreement between theory and practice was then restored.
155.
Sorption of sulfur dioxide (SO2) was carried out on calcium‐based sorbents under dynamic conditions in a fixed bed. The experimental conditions were reaction temperature (700 to 1000°C), SO2 concentration (1000‐10 000 ppm), sorbent particles size (1 to 2 mm) and the types of sorbents (hydroxide or carbonate). The sorption process was found to be effective at low concentration levels (less than 10 000 ppm) as the breakthrough time significantly decreased with increase in concentration. The maximum removal of SO2 was observed at a reaction temperature of 950°C. The hydroxide‐based sorbents of relatively smaller particle size were found to exhibit superior sorption performance in terms of longer breakthrough time and higher sulfate conversion. A mathematical model developed, assuming a porous structure of the sorbent materials, attributed the low sulfation conversion during SO2 sorption due to a pore diffusion mechanism. 相似文献
156.
为有效识别出新维文中大小写同形字母,分析新维文的特点,提出一种基于模板匹配的大小写同形字母识别算法。根据同形字母中大写字母外轮廓大而小写字母外轮廓小的特点,统计字母外轮廓大小与全文字母外轮廓平均大小的比例值,进行字母的大小写判断。分析结果表明,该方法有效克服了传统模板匹配方法容易混淆同形字母的大小写的缺点,提高了系统的识别率。 相似文献
157.
158.
多孔羟基磷灰石(HA)陶瓷内部结构满足细胞向内部渗透、迁移、粘附和生长的条件。实验探讨了HA陶瓷内部成孔与孔道连结的机理与技术,采用添加制孔剂和固化纤维2种方法制备系列样品,测算了样品气孔率,并对微观结构进行扫描电镜观察,最终确定可人工调控内部结构的HA陶瓷成孔与贯通技术。 相似文献
159.
160.
C.C. Yang 《Cement and Concrete Research》2006,36(7):1304-1311
In this study the electrochemical technique is applied to accelerate chloride ion migration in concrete to determine the chloride ions in anode cell, and the pore characteristic of the same mortars in concrete was obtained from the mercury intrusion porosimetry (MIP). The plain ordinary Portland cement and the constant aggregate with eight w/c ratios ranging from 0.3 to 0.65 were used. A good linear relationship between the steady-state migration coefficient and non-steady-state migration coefficient based on the same experimental setup and specimens was obtained. Both of the steady-state migration coefficient and non-steady-state migration coefficient were linearly related to the capillary pore volume and the critical pore diameter. 相似文献