全文获取类型
收费全文 | 1669篇 |
免费 | 96篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 8篇 |
综合类 | 6篇 |
化学工业 | 297篇 |
金属工艺 | 26篇 |
机械仪表 | 24篇 |
建筑科学 | 45篇 |
矿业工程 | 2篇 |
能源动力 | 64篇 |
轻工业 | 116篇 |
水利工程 | 30篇 |
石油天然气 | 1篇 |
无线电 | 210篇 |
一般工业技术 | 343篇 |
冶金工业 | 347篇 |
原子能技术 | 5篇 |
自动化技术 | 243篇 |
出版年
2023年 | 26篇 |
2022年 | 17篇 |
2021年 | 36篇 |
2020年 | 35篇 |
2019年 | 58篇 |
2018年 | 52篇 |
2017年 | 53篇 |
2016年 | 56篇 |
2015年 | 46篇 |
2014年 | 67篇 |
2013年 | 99篇 |
2012年 | 96篇 |
2011年 | 133篇 |
2010年 | 92篇 |
2009年 | 93篇 |
2008年 | 84篇 |
2007年 | 73篇 |
2006年 | 59篇 |
2005年 | 58篇 |
2004年 | 55篇 |
2003年 | 22篇 |
2002年 | 30篇 |
2001年 | 15篇 |
2000年 | 20篇 |
1999年 | 17篇 |
1998年 | 34篇 |
1997年 | 33篇 |
1996年 | 22篇 |
1995年 | 18篇 |
1994年 | 17篇 |
1993年 | 27篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1975年 | 7篇 |
1974年 | 6篇 |
1969年 | 6篇 |
1964年 | 9篇 |
排序方式: 共有1767条查询结果,搜索用时 0 毫秒
101.
102.
Nathan S. Jacobson rew J. Eckel Ajay K. Misra Donald L. Humphrey 《Journal of the American Ceramic Society》1990,73(8):2330-2332
The reactions of a sintered α-SiC with 5% H2 /H2 O/Ar at 1300°C were studied. Thermomchemical modeling indicates that three reaction regions are expected, depending on the initial water vapor or equivalently oxygen content of the gas stream. A high oxygen content ( P (O2 ) > 10−22 atm) leads to a SiO2 formation. This generally forms as a protective film and limits consumption of the SiC (passive oxidation). An intermediate oxygen content (10−22 atm > P (O2 ) > 10−26 atm) leads to SiO and CO formation. These gaseous products can lead to rapid consumption of the SiC (active oxidation). Thermogravimetric studies in this intermediate region gave reaction rates which appear to be controlled by H2 O gas-phase transport to the sample and reacted microstructures showed extensive grain-boundary attack in this region. Finally, a very low oxygen content ( P (O2 ) < 10−26 atm) is thermochemically predicted to lead to selective removal of carbon and formation of free silicon. Experimentally low weight losses and iron silicides are observed in this region. The iron silicides are attributed to reaction of free silicon and iron impurities in the system. 相似文献
103.
Morgan A. Wyatt M. C. Y. Mok Prof. Dr. Murray Junop Prof. Dr. Nathan A. Magarvey 《Chembiochem : a European journal of chemical biology》2012,13(16):2408-2415
Through a number of strategies nonribosomal peptide assembly lines give rise to a metabolic diversity not possible by ribosomal synthesis. One distinction within nonribosomal assembly is that products are elaborated on an enzyme‐tethered substrate, and their release is enzyme catalysed. Reductive release by NAD(P)H‐dependent catalysts is one observed nonribosomal termination and release strategy. Here we probed the selectivity of a terminal reductase domain by using a full‐length heterologously expressed nonribosomal peptide synthetase for the dipeptide aureusimine and were able to generate 17 new analogues. Further, we generated an X‐ray structure of aureusimine terminal reductase to gain insight into the structural details associated with this enzymatic domain. 相似文献
104.
Nathan Jacobson Serene Farmer Arthur Moore Haluk Sayir 《Journal of the American Ceramic Society》1999,82(2):393-398
High-temperature oxidation of monolithic boron nitride (BN) is examined at 900–1200°C. Hot-pressed BN and both low- and high-density chemically vapor-deposited BN are studied. The oxidation product is B2 O3 ( l ) and the oxidation kinetics are sensitive to crystallographic orientation, porosity, and impurity levels. The B2 O3 product also reacts readily with ambient water vapor in the test furnace (ppm levels) to form the volatile species HBO2 ( g ), leading to overall paralinear kinetics. The linear rate constant extracted from these experiments agreed with that predicted from diffusion of HBO2 ( g ) across a static boundary layer. 相似文献
105.
Nathan A. Tregger Margaret E. Pakula Surendra P. Shah 《Cement and Concrete Research》2010,40(3):384-391
The fresh state of concrete is becoming increasingly important in furthering the types of applications of today's construction world. Processing techniques have resulted in technologies such as self-consolidating concrete and depend on the microstructural changes that take place during and immediately after mixing and placing. These changes to the microstructure reflect the flocculation behavior between the particles in suspension. The ability to modify this behavior allows control over the balance among flowability and shape-stability of concrete. This study investigates how clay admixtures affect the microstructure of cement pastes from a rheological stand point. Shear and compressive rheology techniques are used to measure how the solids volume fraction of suspensions with different admixtures evolves with stress. Based on these relationships, the effectiveness of clays on the balance between flowability and shape-stability is measured. Results are consistent with green strength tests performed on concrete mixes derived from the cement paste mixes. 相似文献
106.
Yichuan Ding Nathan Krislock Jiawei Qian Henry Wolkowicz 《Optimization and Engineering》2010,11(1):45-66
We study Semidefinite Programming, SDP, relaxations for Sensor Network Localization, SNL, with anchors and with noisy distance information. The main point of the paper is to view SNL as a (nearest) Euclidean Distance Matrix, EDM, completion problem that does not distinguish between the anchors and the sensors. We show that there are advantages for using the well studied EDM model. In fact, the set of anchors simply corresponds to a given fixed clique for the graph of the EDM problem. 相似文献
107.
A substantial amount of research has demonstrated the importance of reference frames in organizing memory of object locations in both small and large environments. However, to date, little research has examined how the object locations represented in one reference frame are specified relative to object locations represented in another. In a series of 4 experiments, we demonstrate that multiple microreference frames can be established in memory for sets of objects that are spatially and semantically distinct, and that the spatial relations between these microreference frames are specified in memory by means of a more global, macroreference frame. Additionally, these experiments demonstrate that an established macroreference frame can influence which of several microreference frames will be coded in memory, but that a previously established microreference frame had no appreciable influence on the subsequent formation of a macroreference frame. These results are interpreted as indicating that the same cognitive mechanisms underlie interobject coding across multiple environmental scales. The implications for reference frame theories and theories positing hierarchical memory organization are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
108.
109.
Mei CS Mulkern RV Oshio K Chen NK Madore B Panych LP Hynynen K McDannold NJ 《Magma (New York, N.Y.)》2012,25(1):5-14
Object
To develop an ultrafast MRI-based temperature monitoring method for application during rapid ultrasound exposures in moving organs. 相似文献110.
D.S. Choi Jung-Rae Park T. Hahn N. Presser G.W. Stupian Fahad Khalid 《Thin solid films》2010,518(17):5007-5009
This paper describes the development of micro-capacitors with electrodes based on electrochemically grown vertical gold nanowire arrays. A high aspect-ratio anodized aluminum oxide template integrated on silicon dioxide/silicon substrates was exploited for fabricating a vertical array of nanowires with a high surface to volume ratio. Bismuth ferric oxide thin films were deposited to create high dielectric material between the electrodes using room temperature electrodeposition. This nanofabrication process may be compatible with a complementary metal-oxide-semiconductor (CMOS) process, therefore, this capacitor can be used for protecting and regulating the surge voltage biased to the CMOS circuits. This capacitor achieved a high density capacitance of 3.1 μF/m2 at 1 MHz, which was measured using a parallel plate set-up. 相似文献