全文获取类型
收费全文 | 225140篇 |
免费 | 73778篇 |
国内免费 | 50748篇 |
专业分类
电工技术 | 32526篇 |
综合类 | 26414篇 |
化学工业 | 27708篇 |
金属工艺 | 27995篇 |
机械仪表 | 9898篇 |
建筑科学 | 15652篇 |
矿业工程 | 14715篇 |
能源动力 | 9258篇 |
轻工业 | 25369篇 |
水利工程 | 8902篇 |
石油天然气 | 13271篇 |
武器工业 | 4229篇 |
无线电 | 34239篇 |
一般工业技术 | 32612篇 |
冶金工业 | 7802篇 |
原子能技术 | 2431篇 |
自动化技术 | 56645篇 |
出版年
2024年 | 2971篇 |
2023年 | 5026篇 |
2022年 | 6681篇 |
2021年 | 7680篇 |
2020年 | 10073篇 |
2019年 | 18776篇 |
2018年 | 20200篇 |
2017年 | 21778篇 |
2016年 | 21292篇 |
2015年 | 20985篇 |
2014年 | 20299篇 |
2013年 | 19804篇 |
2012年 | 19988篇 |
2011年 | 16658篇 |
2010年 | 15318篇 |
2009年 | 12498篇 |
2008年 | 10547篇 |
2007年 | 10139篇 |
2006年 | 8542篇 |
2005年 | 7636篇 |
2004年 | 9593篇 |
2003年 | 7465篇 |
2002年 | 7144篇 |
2001年 | 6258篇 |
2000年 | 5689篇 |
1999年 | 4666篇 |
1998年 | 3993篇 |
1997年 | 3575篇 |
1996年 | 3419篇 |
1995年 | 3477篇 |
1994年 | 2882篇 |
1993年 | 2660篇 |
1992年 | 2587篇 |
1991年 | 1874篇 |
1990年 | 1474篇 |
1989年 | 1387篇 |
1988年 | 1056篇 |
1987年 | 324篇 |
1986年 | 284篇 |
1985年 | 204篇 |
1984年 | 141篇 |
1983年 | 104篇 |
1982年 | 145篇 |
1981年 | 152篇 |
1980年 | 103篇 |
1976年 | 228篇 |
1975年 | 203篇 |
1972年 | 235篇 |
1971年 | 127篇 |
1960年 | 206篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
This paper focuses on the microscopic damage and progressive failure of a composite reinforced by plain-weave glass cloth under tensile fatigue loading. The fatigue process was divided into three stages like that of multi-directional laminates. It was found that the internal damage at each stage (matrix cracks, debonds in the weft, successive debonds in the warp and ‘metadelaminations’ between warps and wefts) occurred near the cross-over point of the fabric. The modulus decay mechanism was explained by considering the progression of this internal damage. From the end of the first stage to the beginning of the middle stage, a characteristic damage state (CDS) (called a ‘meta-CDS’) was observed. It was found that woven composites have a unit area of damage accumulation (called a ‘unit cell’) and the damage of each unit cell and its distribution control the total fatigue damage of the material. 相似文献
102.
Fastconvergentstudyonpotential-harmonicmethodofdirectlysolvingSchrodingerequationinfew-bodysystemsWangYi-Xuan(王沂轩)andDensCong... 相似文献
103.
Novel algorithmic features of multimedia applications and advances in VLSI technologies are driving forces behind the new multimedia signal processors. We propose an architecture platform which could provide high performance and flexibility, and would require less external I/O and memory access. It is comprised of array processors to be used as the hardware accelerator and RISC cores to be used as the basis of the programmable processor. It is a hierarchical and scalable architecture style which facilitates the hardware-software codesign of multimedia signal processing circuits and systems. While some control-intensive functions can be implemented using programmable CPUs, other computation-intensive functions can rely on hardware accelerators.To compile multimedia algorithms, we also present an operation placement and scheduling scheme suitable for the proposed architectural platform. Our scheme addresses data reusability and exploits local communication in order to avoid the memory/communication bandwidth bottleneck, which leads to faster program execution. Our method shows a promising performance: a linear speed-up of 16 times can be achieved for the block-matching motion estimation algorithm and the true motion tracking algorithm, which have formed many multimedia applications (e.g., MPEG-2 and MPEG-4). 相似文献
104.
Hamid R. Parsaei Mickey R. Wilhelm Sai S. Kolli 《Computers & Industrial Engineering》1993,25(1-4):357-360
Traditional economic evaluation methods concentrate on maximizing or minimizing a single objective such as net present value and pay back period. In the last decade, there has been an increased awareness of the need to consider multiple attributes in the evaluation of advanced manufacturing systems. Various methods have recently been developed for the evaluation of CIM systems. This paper discusses multiattribute methods for justification of CIM systems and outranking methods including ELECTRE, ORESTE, and PROMETHEE. 相似文献
105.
The Bi-system tapes and coils were prepared by the powder-in-tube method. The effect of processing and heat treatment on the properties of the tapes and coils was studied. It is found that the shearing stress produced by the rolling process may destroy the 2223 phase, and the destroyed 2223 phase cannot be recovered by heat treatment, whereas the pressing stress produced by the uniaxial pressing process only makes the 2223 phase grains break, and the broken 2223 phase can be closed by the heat treatment. TheJ
c values of the rolling samples, pressing sample, and the coil with a diameter of 35 mm are over 1.3×104, 2.5×104, and 4×103 A/cm2 (77 K, 0 T), respectively. 相似文献
106.
This article presents an overview of the results of a five-year research project on sensors for the food industry in Japan. This project was a government-sponsered research programme involving the food industry and the instrumentation industry, coordinated by the Japanese Ministry of Agriculture, Forestry and Fisheries. The programme focussed on 17 food processing operations and quality control tasks, where the need for an on-line (or rapid at-line) measurement had been established. The instrument development work employed biosensors pH and gas sensors, optical-imaging devices, as well as near-infrared, microwave, ultrasound and mechanical resonance techniques, together with robotics and advanced data-processing techniques. 相似文献
107.
This paper discusses the seafloor thermalwater spout sedimentary activity in South Yongmei Depression according to the following
evidences: the Yongmei region was in an extended tectonic environment of metaplateform and locally developed intracontinental
rift aulacogen in company with the activity of rich alkali, high potassium volcanics of double-peak type. Several kinds of
hydrothermal sedimentary rocks and the ore-bearing sedimentary formations of copper-polymetals, iron and manganese exist in
this region with a zoning feature of the seafloor thermalwater spout sedimentation.
Project supported by the Science Foundation of NECC for Returns
Synopsis of the first author Wu Chengjian, associated professor, born in 1957, majoring in ore deposit and mineralgraphy. 相似文献
108.
High-T
c
Bi(Pb)-Sr-Ca-Cu-O thin films have been made on single-crystal MgO substrates using high-pressure dc sputtering technique. X-ray studies confirm the crystallinity and highly oriented structure withc-axis perpendicular to the substrate. By optimizing the annealing schedule the formation of the high-T
c
phase is stabilized. The best film exhibited superconducting transition temperature with zero-resistance temperature,T
c(0), as high as 101 K. Temperature dependence ofJ
c
indicates the presence of Josephson-type weak links. 相似文献
109.
The temperature dependence of a marginal Fermi liquid has been calculated. We showed that the expectedT lnT correction is characteristic for the low-temperature domain. The high-temperature domain has a supplementary correction. The results are in agreement with the non-Fermi behavior of some metallic systems the in low-temperature domain. 相似文献
110.
Ben J. A. Kr se Kai M. Compagner Franciscus C. A. Groen 《Robotics and Autonomous Systems》1993,11(3-4):221-230
This paper describes a robust and accurate ultrasonic sensing system for a mobile robot. The system continuously updates a local map of the environment in which obstacles are represented by straight lines or points in a robot centered coordinate frame. The presented algorithms use a Kalman filter for the reduction of the noise in the ultrasonic data and use a systematical error correction (‘bundle correction’) to reduce the uncertainty in obstacle direction. Experiments are carried out in simulation and with a real mobile robot system. Results show that the accuracy with which line parameters can be estimated is in the order of 1 degree for the orientation and about 2 cm for the position. The effect of the bundle correction is significant and maximal when the robot approaches walls under a small angle. 相似文献