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991.
针对常规PID控制策略在复配釜內化学反应的吸热升温阶段和放热保温阶段的转折处难以取得满意控制效果的问题,提出了利用多变量动态矩阵控制(DMC)算法实现对设定温度的跟踪控制.进一步引入了DMC-PID控制策略,以改善系统的控制性能,实现了对设定温度的有效跟踪控制.最后通过试验研究,验证了本文方法的有效性. 相似文献
992.
直接法合成甲基(氢)二氯硅烷新工艺研究 总被引:1,自引:0,他引:1
本文通过催化作用原理研究,提出了以Si、CH_3Cl为原料,直接法合成CH_3SiHCl_2的新工艺.采用CuCl-Ni-Zn催化体系不但能使CH_3Cl适量分解产生HCl.而且还能促进HCl与Si、CH_3Cl反应并有效地转化为目的产物CH_3SiHCl_2,由小试和400mm流化床中试所得的混合单体中,CH_3SiHCl_2含量>15%,(CH_3)_2SiCl_2>50%,为工业化生产有机硅含氢单体开辟了新的途径。 相似文献
993.
994.
介绍了环氧丙烯酸酯从双酯合成到双酯的改性,以及近几年新提出的单酯合成及应用的研究现状,评述了环氧丙烯酸酯,尤其是环氧丙烯酸单酯合成的研究进展。 相似文献
995.
H. Sun D. Wiesenborn P. Rayas-Duarte A. Mohamed K. Hagen 《Journal of the American Oil Chemists' Society》1995,72(12):1551-1555
Amaranth seed (Amaranthus hypochondriacus cv. K432) was processed to obtain oil, reported to be a promising source of squalene. The amaranth seed was ground using
a stone mill, then separated into oil-rich embryonic tissue (or “bran”) and starchy perisperm. Amaranth bran was much more
stable than rice bran when free fatty acid (FFA) content and peroxide value were monitored. Milling at a gap of 0.755 mm did
not result in excessive damage to the starch in the perisperm fraction and yielded a bran fraction that contained more than
three-fourths of the oil and a starchy fraction consisting of more than two-thirds of the seed weight. The bran particles
were too fine for effective bench-scale extraction of the oil. Consequently the bran was extruded into collects prior to extraction.
Two extrusion settings were evaluated regarding the rate of moisture injection, while the bran feed rates were constant. There
was no significant difference in appearance or size between the two dried collets. Collets were extracted with hexane using
an Armfield Extraction/Desolventizing Unit (Model FT 29, Armfield, Ltd., Hampshire, England). Oil recovery averaged 97.7 and
80.0%, respectively. Oil was extracted at high yield from the bran when the bran was extruded into collets. Oil can be obtained
as a coproduct of amaranth starch by milling and separating the fractions of amaranth seed. Milling, extrusion, and extraction
did not decrease significantly the squalene content in amaranth oil, but increased FFA content and peroxide value and changed
tocopherol content of the oil. 相似文献
996.
Secure and robust image hashing via compressive sensing 总被引:1,自引:0,他引:1
Image hash functions find extensive applications in content authentication, database search. This paper develops a novel algorithm for generating a secure and robust image hash based on compressive sensing and Fourier-Mellin transform. Firstly, we incorporate Fourier-Mellin transform into our method to improve its performance under rotation, scale, transition attacks. Secondly, we exploit the property of dimension reduction inherent in compressive sensing for hash design. The statistic structure and sparse of the wavelet coefficients assure efficient compression in situation of including maximum the image features. The hashing method is computationally secure without additional randomization process. Such a combined approach is capable of tackling all types of attacks and thus can yield a better overall performance in multimedia identification. To demonstrate the superior performance of the proposed schemes, receiver operating characteristics analysis over a large image database is performed. Experimental results show that the proposed image hashing is robust to a wide range of distortions and attacks. When compared with the current state-of-the-art methods, the proposed method yields better identification performances under geometric attacks such as rotation attacks and brightness changes. 相似文献
997.
We are living in a world of various kinds of social information networks with small-world and scale-free characteristics. It is still an intriguing problem for researchers to explain how and why so many obviously different networks emerge and share common intrinsic characteristics such as short diameter, higher cluster and power-law degree distribution. Most previous works studied the topology formation and information navigation of complex networks in separated models. In this paper, we propose a metric based range intersection model to explore the topology evolution and information navigation in a synthetic way. We model the network as a set of nodes in a distance metric space where each node has an ID and a range of neighbor information around its ID in the metric space. The range of a node can be seen as the local knowledge or information that the node has around its position in the metric space. The topology is formed by setting up a link between two nodes that have intersected ranges. Information navigation over the network is modeled as a greedy routing process using neighbor links and the distance metric. Different from previous models, we do not assume that nodes join the network one by one and set up link according to the degree distribution of existing nodes or distances between nodes. Range of node is the key factor determining the topology and navigation properties of a network. Moreover, as the ranges of nodes grow, the network evolves from a set of totally isolated nodes to a connected network. Thus, we can easily model the network evolutions in terms of the network size and the individual node information range using the range intersection model. A set of experiments shows that networks constructed using the range intersection model have the scale-free degree distribution, high cluster, short diameter, and high navigability properties that are owned by the real networks. 相似文献
998.
Shangguang Wang Ching-Hsien Hsu Zhongjun Liang Qibo Sun Fangchun Yang 《Information Systems Frontiers》2014,16(1):143-152
In order to find best services to meet multi-user’s QoS requirements, some multi-user Web service selection schemes were proposed. However, the unavoidable challenges in these schemes are the efficiency and effect. Most existing schemes are proposed for the single request condition without considering the overload of Web services, which cannot be directly used in this problem. Furthermore, existing methods assumed the QoS information for users are all known and accurate, and in real case, there are always many missing QoS values in history records, which increase the difficulty of the selection. In this paper, we propose a new framework for multi-user Web service selection problem. This framework first predicts the missing multi-QoS values according to the historical QoS experience from users, and then selects the global optimal solution for multi-user by our fast match approach. Comprehensive empirical studies demonstrate the utility of the proposed method. 相似文献
999.
1000.