全文获取类型
收费全文 | 2837篇 |
免费 | 168篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 30篇 |
综合类 | 3篇 |
化学工业 | 618篇 |
金属工艺 | 67篇 |
机械仪表 | 143篇 |
建筑科学 | 113篇 |
矿业工程 | 4篇 |
能源动力 | 69篇 |
轻工业 | 491篇 |
水利工程 | 15篇 |
石油天然气 | 19篇 |
无线电 | 210篇 |
一般工业技术 | 467篇 |
冶金工业 | 320篇 |
原子能技术 | 15篇 |
自动化技术 | 423篇 |
出版年
2024年 | 4篇 |
2023年 | 27篇 |
2022年 | 67篇 |
2021年 | 106篇 |
2020年 | 60篇 |
2019年 | 78篇 |
2018年 | 94篇 |
2017年 | 90篇 |
2016年 | 140篇 |
2015年 | 80篇 |
2014年 | 110篇 |
2013年 | 185篇 |
2012年 | 159篇 |
2011年 | 185篇 |
2010年 | 118篇 |
2009年 | 138篇 |
2008年 | 127篇 |
2007年 | 101篇 |
2006年 | 95篇 |
2005年 | 186篇 |
2004年 | 169篇 |
2003年 | 119篇 |
2002年 | 54篇 |
2001年 | 35篇 |
2000年 | 34篇 |
1999年 | 26篇 |
1998年 | 109篇 |
1997年 | 66篇 |
1996年 | 58篇 |
1995年 | 23篇 |
1994年 | 20篇 |
1993年 | 32篇 |
1992年 | 16篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1976年 | 13篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1971年 | 2篇 |
排序方式: 共有3007条查询结果,搜索用时 273 毫秒
71.
Since the introduction of sodium metabisulfite as a food preservative, it has been associated with several idiosyncratic reactions (eg, bronchospasm, oculonasal symptoms, and urticaria/angioedema) in sulfite-sensitive individuals. The pathogenic mechanism of these reactions is not yet understood. We report the case of two crewmen on a shrimp trawler who were found dead in the ship's hold. Their deaths had occurred while they were applying dry sodium metabisulfite, referred to as "shrimp dip" in the shrimping industry. Postmortem examinations showed diffuse pulmonary edema consistent with death secondary to asphyxia. Associated findings were visceral congestion. Although it is possible to measure death from sodium metabisulfite with available records, its potential morbidity cannot be estimated. It is known that sodium metabisulfite can react with acids and water, releasing toxic sulfur dioxide (SO2) gas. In addition, SO2 gas reacts with respiratory tissue forming sulfureous acid, and inducing a pulmonary reaction causing hypoxemia. Furthermore, sodium metabisulfite, compared with sodium bisulfite, has a much greater propensity to release SO2 gas. We conclude that there is a need for improved education regarding the potential side effects of sodium metabisulfite, thus eliminating needless occupational morbidity and mortality. 相似文献
72.
M.?Peláez C.?Orellana A.?Marqués M.?Busquets A.?Guerrero A.?ManresaEmail author 《Journal of the American Oil Chemists' Society》2003,80(9):859-866
Estolides are a group of FA polyesters resulting from ester bond formation between a hydroxyl or olefinic group of one FA
and the terminal carboxyl group of a second FA. These products are commonly found in trace amounts, forming tetraglycerides
in several oil seed plants, and have been produced by acid clay and enzymatic catalysis in vitro. In this study, natural estolides produced by a bacterial culture are presented for the first time. Pseudomonas sp. 42A2 produced (E)-10-hydroxy-8-octadecenoic acid and (E)-7,10-dihydroxy-8-octadecenoic acid when grown on oleic acid. It is suggested that these FA were polymerized in culture by
a lipase produced by the bacterial strain, resulting in a mixture of estolides. These compounds amounted to 3.8 g/L after
72 h of incubation. LC-MS analysis indicated that the types of estolides formed were dimers (m/z 560–610), trimers (m/z 845–906), tetramers (m/z 1122–1202), pentamers (m/z 1328–1424), and hexamers (m/z 1554–1788), with a relative abundance of 27.5, 19.4, 15, 9.7, and 11%, respectively. This is the first report in which hexamers
were detected in a bacterial culture. 相似文献
73.
Hyunjung Shim Rolf Adelsberger James Dokyoon Kim Seon-Min Rhee Taehyun Rhee Jae-Young Sim Markus Gross Changyeong Kim 《The Visual computer》2012,28(12):1139-1151
This paper presents a multi-view acquisition system using multi-modal sensors, composed of time-of-flight (ToF) range sensors and color cameras. Our system captures the multiple pairs of color images and depth maps at multiple viewing directions. In order to ensure the acceptable accuracy of measurements, we compensate errors in sensor measurement and calibrate multi-modal devices. Upon manifold experiments and extensive analysis, we identify the major sources of systematic error in sensor measurement and construct an error model for compensation. As a result, we provide a practical solution for the real-time error compensation of depth measurement. Moreover, we implement the calibration scheme for multi-modal devices, unifying the spatial coordinate for multi-modal sensors. The main contribution of this work is to present the thorough analysis of systematic error in sensor measurement and therefore provide a reliable methodology for robust error compensation. The proposed system offers a real-time multi-modal sensor calibration method and thereby is applicable for the 3D reconstruction of dynamic scenes. 相似文献
74.
S. L. Correia A. P. N. Oliveira D. Hotza A. M. Segadães 《Journal of the American Ceramic Society》2006,89(11):3356-3365
The effect of raw materials type and content on the properties of clay–feldspar–quartz compositions was studied using the statistical design of mixture experiments. Based on wall and floor tile industrial practice, 10 mixtures of three raw materials were selected and processed. Characterization results were used to calculate statistically significant and valid regression equations, relating fired body properties with clay, feldspar, and quartz contents in the unfired mixture. Such statistical modeling is discussed against quantitative X-ray diffraction and scanning electron microscopy results. The glassy phase present was found to control the microstructure and the mechanical strength of the fired ceramic body. 相似文献
75.
The tensile properties and microstructures of various Al alloys fabricated by the pressureless infiltration method under a nitrogen atmosphere were examined. The spontaneous infiltration of molten metal into the powder bed occurred at 800 °C for 1 h under a nitrogen atmosphere. As a result, it was possible to fabricate Al alloys reinforced with AlN particles formed by in situ reaction. A significant strengthening even in the control alloy occurred due to the formation of in situ AlN particle even without an addition of artificial reinforcement. Strength values of the control alloy were increased with decreasing Al powders in bottom powders bed. In addition, tensile strength in Al–Mg alloys was increased with Mg content. 相似文献
76.
Jos M. Simes Moita Cristvo M. Mota Soares Carlos A. Mota Soares 《Composite Structures》2005,71(3-4):349-355
This paper deals with a finite element formulation for active control of forced vibrations, including resonance, of thin plate/shell laminated structures with integrated piezoelectric layers, acting as sensors and actuators, based on third-order shear deformation theory. The finite element model is a single layer triangular nonconforming plate/shell element with 24 degrees of freedom for the generalized displacements, and one electrical potential degree of freedom for each piezoelectric element layer, which are surface bonded or embedded in the laminate.
The Newmark method is considered to calculate the dynamic response of the laminated structures, forced to vibrate in the first natural frequency. To achieve a mechanism of active control of the structure dynamic response, a feedback control algorithm is used, coupling the sensor and active piezoelectric layers. The model is applied in the solution of illustrative cases, and the results are presented and discussed. 相似文献
77.
A. Gromann de Araujo Ges M. A. B. Alvarenga P. F. Frutuoso e Melo 《Reliability Engineering & System Safety》2005,87(2):136
We have developed and implemented a computerized reliability monitoring system for nuclear power plant applications, based on a neural network. The developed computer program is a new tool related to operator decision support systems, in case of component failures, for the determination of test and maintenance policies during normal operation or to follow an incident sequence in a nuclear power plant. The NAROAS (Neural Network Advanced Reliability Advisory System) computer system has been developed as a modularized integrated system in a C++ Builder environment, using a Hopfield neural network instead of fault trees, to follow and control the different system configurations, for interventions as quickly as possible at the plant. The observed results are comparable and similar to those of other computer system results. As shown, the application of this neural network contributes to the state of the art of risk monitoring systems by turning it easier to perform online reliability calculations in the context of probabilistic safety assessments of nuclear power plants. 相似文献
78.
Kwang Mong Sim Weng Hong Sun 《IEEE transactions on systems, man, and cybernetics. Part A, Systems and humans : a publication of the IEEE Systems, Man, and Cybernetics Society》2003,33(5):560-572
Although an ant is a simple creature, collectively a colony of ants performs useful tasks such as finding the shortest path to a food source and sharing this information with other ants by depositing pheromone. In the field of ant colony optimization (ACO), models of collective intelligence of ants are transformed into useful optimization techniques that find applications in computer networking. In this survey, the problem-solving paradigm of ACO is explicated and compared to traditional routing algorithms along the issues of routing information, routing overhead and adaptivity. The contributions of this survey include 1) providing a comparison and critique of the state-of-the-art approaches for mitigating stagnation (a major problem in many ACO algorithms), 2) surveying and comparing three major research in applying ACO in routing and load-balancing, and 3) discussing new directions and identifying open problems. The approaches for mitigating stagnation discussed include: evaporation, aging, pheromone smoothing and limiting, privileged pheromone laying and pheromone-heuristic control. The survey on ACO in routing/load-balancing includes comparison and critique of ant-based control and its ramifications, AntNet and its extensions, as well as ASGA and SynthECA. Discussions on new directions include an ongoing work of the authors in applying multiple ant colony optimization in load-balancing. 相似文献
79.
As the use of the computer is popularized, the damage from computer viruses and hacking by malicious users is increasing rapidly.
To block the hacking that is an intrusion into a person's computer, and the viruses that destroy data, a study into an intrusion
detection and virus detection system based on the biological immune system is in progress. In this article, we describe a
model of positive and negative selection for self-recognition, which has a similar function to the cytotoxic T cells that
play an important role in the biological immune system. We propose a self/nonself discrimination algorithm for a computer
system, which will the important when we detect data infected by a computer virus, of data modified by an intrusion from outside.
We also show the validity and effectiveness of the proposed self-recognition algorithm by a computer simulation of some infected
data obtained from cell changes and string changes in the self-file.
This work was presented, in part, at the Seventh International Symposium on Artificial Life and Robotics, Oita, Japan, January
16–18, 2002 相似文献
80.
Robust reweighted MAP motion estimation 总被引:2,自引:0,他引:2
Dong-Gyu Sim Rae-Hong Park 《IEEE transactions on pattern analysis and machine intelligence》1998,20(4):353-365
This paper proposes a motion estimation algorithm that is robust to motion discontinuity and noise. The proposed algorithm is constructed by embedding the least median squares (LMedS) of robust statistics into the maximum a posteriori (MAP) estimator. Difficulties in accurate estimation of the motion field arise from the smoothness constraint and the sensitivity to noise. To cope robustly with these problems, a median operator and the concept of reweighted least squares (RLS) are applied to the MAP motion estimator, resulting in the reweighted robust MAP (RRMAP). The proposed RRMAP motion estimation algorithm is also generalized for multiple image frame cases. Computer simulation with various synthetic image sequences shows that the proposed algorithm reduces errors, compared to three existing robust motion estimation algorithms that are based on M-estimation, total least squares (TLS), and Hough transform. It is also observed that the proposed algorithm is statistically efficient and robust to additive Gaussian noise and impulse noise. Furthermore, the proposed algorithm yields reasonable performance for real image sequences 相似文献