全文获取类型
收费全文 | 3400篇 |
免费 | 229篇 |
国内免费 | 1002篇 |
专业分类
林业 | 394篇 |
农学 | 275篇 |
基础科学 | 760篇 |
1229篇 | |
综合类 | 1554篇 |
农作物 | 75篇 |
水产渔业 | 50篇 |
畜牧兽医 | 143篇 |
园艺 | 34篇 |
植物保护 | 117篇 |
出版年
2024年 | 43篇 |
2023年 | 142篇 |
2022年 | 208篇 |
2021年 | 230篇 |
2020年 | 193篇 |
2019年 | 183篇 |
2018年 | 149篇 |
2017年 | 218篇 |
2016年 | 224篇 |
2015年 | 199篇 |
2014年 | 217篇 |
2013年 | 242篇 |
2012年 | 295篇 |
2011年 | 266篇 |
2010年 | 256篇 |
2009年 | 221篇 |
2008年 | 202篇 |
2007年 | 243篇 |
2006年 | 188篇 |
2005年 | 185篇 |
2004年 | 123篇 |
2003年 | 83篇 |
2002年 | 73篇 |
2001年 | 51篇 |
2000年 | 26篇 |
1999年 | 27篇 |
1998年 | 24篇 |
1997年 | 17篇 |
1996年 | 16篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1993年 | 20篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有4631条查询结果,搜索用时 323 毫秒
41.
To the question that a meter is correspond with a set of lead and a sensor,this paper presents a design of data acquisition system for vehicle based on CAN bus.In this way,the combinatorial instrument is only connected by a bus unit.Author introduces the data acquisition structure chart and the CAN interface,analyzes the software by program flow chart,and shows it's application for vehicle virtual instrument.A method of calculating vehicle speed,engine rotate speed and the course of development mileage are also given. 相似文献
42.
Considering the difficult of acquiring and transmission the signal from the moving equipment, a new fault diagnosis monitoring system is presented. The system acquires the state signal from the moving equipment by data acquisition module that based in W77E58 high-speed SCM, and transmits the data fast by wireless mode. The signal data can be use for fault diagnosis and precise analysis. The system has the ability for acquiring abundance of data with a high speed, the ability for high accuracy data conversion, and has a function of programme controlling gain and programme controlling low-pass filtering. The successful application of this system on the vibration monitor about the material-transporting bogie in an iron works of a domestic steel enterprise proves the stability and credibility about the design project, also testifies its practical value and versatility. 相似文献
43.
The colored patterns on arbitrary cut plane is an important method in 3D data-field visualization of finite element.By using the technology of the Object-Oriented Programming and the method of scan-line,the colored patterns on arbitrary cut plane are given.The example by the OPENGL of Visual C++ R6 can support the theory satisfactorily. 相似文献
44.
Aimed at soving the problem existing in the knowledge-acquisition directing-operation expert systems, a new method is proposed to acquire knowledge of expert-operation, excluding errors existed in examples and reinforce the accuracy of examples,the goal of knowledge acquisition can be achieved, the method presented in this paper solves the problem of self-enhancement of expert knowledge on line efficiently. 相似文献
45.
Image compression is very important in picture archiving and communication system(PACS). The author studied the statistical distribution of image wavelet subimage coefficients and concluded that the distribution of wavelet subimage coefficients is similar to that of Laplasian distribution. On the other hand, in image reconstruction, the coefficient with different amplitude owns different weight, and different accuracy can be applied to different coefficients according to their different weight. Then, the author has designed a image quantization encoding scheme for PACS. In this scheme, they selected the sample-standard-deviation of coefficients in every subimage as the quantization threshold, and accurately encoded those coefficients with higher weight. Also, this algorithm utilized the visual character of human. The test has proved that the main advantages of this method are the simplicity in computing and predictable encoded coefficients, and a high compression efficiency can obtain too. 相似文献
46.
A vision system based on the service robot is involved. In the system, picture signal is acquired by the picture sensor OV7635. Frame memory AL422B is used as data buffer memory, while CPLD controlled the time order DSP performed. In the software system of image processing, to accomplish color image segmentation and recognition, the threshold vector judgment and improved seed-fill algorithm is introduced, and the image geometric moment is calculated during the segmenting. In order to achieve a vision servo system which composed of image-based feedback and adaptive compensation, the deduced matrix-based Jacobian from the image moment is taken as image feature. Adopted the TFT LCD is adopted to straightly disolav the result of vision recognition and vision tracing. 相似文献
47.
Fractal image coding techniques usually partition the input image into small range blocks. This artificially introduces boundaries into the image resulting in the unpleasant blocking artifacts in the decoded images especially at high compression rate. Because the effect is especially responsible for the restrictions of the block-based coders, the solutions must be sought to reduce this blockiness. Recently two possible schemes have been proposed by other researchers: One may try to use overlapping blocks in the fractal transform, and the other to employ the combined fractal wavelet approach. An alternative solution is proposed, which employs the bilinear interpolation techniques and the resolution independence of fractal coding, in the sense that an image can be decoded at higher or lower resolutions than the original. Experiments show that the proposed scheme can eliminate the blocking artifacts. 相似文献
48.
Aiming at the problem of representation of regions in the process of image processing, the paper presents a method applied to representation of spatial uncertain area in image based on Cloud-model. In two-dimension universe of discourse of image, the linguistic term of the polygons, which have uncertain edge, can be accomplished by relaxation iteration. The linguistic term of the polygons can be considered Cloud-core of Cloud-model. Based on the characteristics of pixels of transition region of fuzzy edge, Object-clouds of polygons can be constructed by Backward-cloud-generator. So Object-cloud can be representation model of spatial uncertain area and spatial uncertain area in image can be represented by digital characteristics of Object-cloud. Experiments testify the method. It enriches the cloud theory, and proposes a new idea for image comprehending and analyzing, especially remote sensing image. 相似文献
49.
The damage of bridge cable directly hazards the normal use of bridge and the safety of people. The paper discussed the signal acquisition and detection system which takes embedded DSP processor as core technology, combined with CCD, video decode chip, SDRAM, FLASH ROM, and established the fast measuring algorithm of the surface corrosion and damage, which includes deteminating the processing region, improving medium filter, sobel edge detection and dynamic threshold segment, close operation of morphology, computing defect area and saving. The experimental resuits show that this method implemented the real-time, non-contact and intelligence detecting of cable surface defect and gives the specifications of the system. 相似文献
50.