全文获取类型
收费全文 | 5739篇 |
免费 | 27篇 |
国内免费 | 77篇 |
专业分类
系统科学 | 871篇 |
丛书文集 | 57篇 |
教育与普及 | 133篇 |
理论与方法论 | 9篇 |
现状及发展 | 51篇 |
研究方法 | 3篇 |
综合类 | 4719篇 |
出版年
2023年 | 1篇 |
2019年 | 1篇 |
2017年 | 20篇 |
2016年 | 24篇 |
2015年 | 34篇 |
2014年 | 8篇 |
2013年 | 8篇 |
2012年 | 9篇 |
2011年 | 349篇 |
2010年 | 111篇 |
2009年 | 282篇 |
2008年 | 92篇 |
2007年 | 120篇 |
2006年 | 58篇 |
2005年 | 85篇 |
2004年 | 621篇 |
2003年 | 510篇 |
2002年 | 256篇 |
2001年 | 208篇 |
2000年 | 106篇 |
1999年 | 174篇 |
1998年 | 311篇 |
1997年 | 262篇 |
1996年 | 69篇 |
1995年 | 70篇 |
1994年 | 66篇 |
1993年 | 493篇 |
1992年 | 396篇 |
1991年 | 359篇 |
1990年 | 247篇 |
1989年 | 184篇 |
1988年 | 107篇 |
1987年 | 122篇 |
1986年 | 73篇 |
1985年 | 6篇 |
1983年 | 1篇 |
排序方式: 共有5843条查询结果,搜索用时 15 毫秒
121.
Parallel Mechanisms with Two or Three Degrees of Freedom 总被引:2,自引:0,他引:2
Parallel manipulators for the machine tool industry have been studied extensively for various industrial applications. However, limited useful workspace areas, the poor mobility, and design difficulties of more complex parallel manipulators have led to more interest in parallel manipulators with less than six degrees of freedom (DoFs). Several parallel mechanisms with various numbers and types of degrees of freedom are described in this paper, which can be used in parallel kinematics machines, motion simulators, and industrial robots. 相似文献
122.
Nine kinds of reactive dye solutions: Reactive K-2RL, H-E2R, X-6B1Y, HE-4G, X-3B, K-2R,H-E7B, X-4RN and S-F3B were treated by usingFenton reagent. While the concentration of dye is 400mg/L, the FeSO_4 dosage 100-180 mg/L, H_2O_2 240~540 mg/L, that is the stoichiometric numbers of Fe~(2+)and H_2O_2. are between 1: 9~1: 12, pH=3, reaction 相似文献
123.
Multi-objective Scheduling Using an Artificial Immune System 总被引:1,自引:0,他引:1
124.
Two methods of computer data processing, linear fitting and nonlinear fitting, are applied to compute the rate constant for hydrogen peroxide decomposition reaction. The results indicate that not only the new methods work with no necessity to measure the final oxygen volume, but also the fitting errors decrease evidently. 相似文献
125.
A group of grafted PET fibers with different graft yield are formed by grafting acrylamide onto the PET main chains. The structure of grafted fibers are studied by scanning electronic microscope ( SEM ), infra-red spectrophotometer ( IR ), and differential scanning calorimetry(DSC). At the same time, the moisture regain, dyeability, strength, and elongation at break of the samples are measured and their relations with structural changes are discussed. Compared with ungrafted fiber, shape of the fiber cross-section, IR characteristic absorption peaks, and melting behavior of the grafted fibers have been changed, causing the fiber dyeability and moisture regain to be increased, and mechanical properties to be changed. 相似文献
126.
A set of new current sensing device is used to realize joint torque control based on current measurement in a precision assembly robot's third joint. The output torque's model of the joint's brushless DC motor is founded. Disturbance factors and the compensated effect of the torque's closed loop based on current measurement are analyzed. Related simulations and experiments show that the system has good current tracking and anti-disturbances performance, which improve the force control performance of the robot in assembly. 相似文献
127.
With layer-measured contours, an algorithm that can extract the contour segments from a rotational surface is presented. The extraction can be divided into two stages, i. e. the rough segmentation and the refinement. In the rough segmenting stage, an optimal contour matching method is put forward to find similar contour segment from another closed contour with respect to the seed contour. In the refining stage, an iterative way that can extract a circular arc precisely is presented based on parameters identification and contour-ends expanding/shrinking operation. The algorithm can extract the open contour segments from a rotational surface precisely, as demonstrated in the examples. Based on the work of this paper, further research, such as parameter identification of 3 - D surface and CAD model creation, can be conducted. 相似文献
128.
Acute toxicity and accumulated toxicity of chlorine dioxide (ClO2) and by-products chlorite (ClO2-) and chlorate (ClO3-) in water acted on mice are studied by the method of Horn and accumulation coefficient. Subchronic toxicity of the mixture of ClO2 and ClO2-and ClO3- in water acted on rat is studied though feeding test for 90 days, including statistical analysis of variance on weight gaining, food utilization efficiency,index of blood and serum,liver (or kidney) to body weight ratio, and histopathological examination on liver and kidney. The results show that aqueous solution of ClO2, NaClO2 and NaClO3 ( with the concentration of 276.5 mg/L, 200 mg/L and 200 mg/L respectively) and the mixed aqueous solution of ClO2 with the concentration of 553 mg/L are actually non-poisonous , and non-cumulative aqueous solution as well. 相似文献
129.
A novel hyper-redundant manipulator named RT1 is designed and studied. The unique feature of RT1 is all degrees of freedom (DOF) are actuated with only one motor via special designed hinge bar universal joints. The mechanisms of RT1 are introduced in detail. Some experiments are carried out in order to test the movability and adaptability of the manipulator. RT1 is actuated by pulse string and acts discretely. The discrete working space of RT1 is described and the parameter optimization for kinematical redundancy resolution is studied also. The optimization criterion is altering the design parameter as little as possible during manipulator's motion from the initial position to the expected position. An optimization example is given that is realized with Matlab optimize tool-box. 相似文献
130.
详细论述了混炼型聚氨酯弹性体(MPU)的加工过程和特性,通过实验指出了生胶可塑度与MPU的加工过程和质量有密切的关系,影响可塑度的因素有生胶中硬链段的含量、聚酯二醇的结构和生胶的分子量。 相似文献