全文获取类型
收费全文 | 2489篇 |
免费 | 81篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 157篇 |
综合类 | 7篇 |
化学工业 | 602篇 |
金属工艺 | 64篇 |
机械仪表 | 51篇 |
建筑科学 | 46篇 |
矿业工程 | 4篇 |
能源动力 | 132篇 |
轻工业 | 218篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
武器工业 | 1篇 |
无线电 | 222篇 |
一般工业技术 | 457篇 |
冶金工业 | 388篇 |
原子能技术 | 57篇 |
自动化技术 | 169篇 |
出版年
2023年 | 10篇 |
2022年 | 26篇 |
2021年 | 59篇 |
2020年 | 18篇 |
2019年 | 31篇 |
2018年 | 41篇 |
2017年 | 33篇 |
2016年 | 49篇 |
2015年 | 38篇 |
2014年 | 54篇 |
2013年 | 110篇 |
2012年 | 91篇 |
2011年 | 138篇 |
2010年 | 96篇 |
2009年 | 121篇 |
2008年 | 127篇 |
2007年 | 124篇 |
2006年 | 109篇 |
2005年 | 99篇 |
2004年 | 88篇 |
2003年 | 84篇 |
2002年 | 77篇 |
2001年 | 55篇 |
2000年 | 56篇 |
1999年 | 63篇 |
1998年 | 135篇 |
1997年 | 95篇 |
1996年 | 53篇 |
1995年 | 57篇 |
1994年 | 55篇 |
1993年 | 48篇 |
1992年 | 33篇 |
1991年 | 38篇 |
1990年 | 24篇 |
1989年 | 26篇 |
1988年 | 32篇 |
1987年 | 20篇 |
1986年 | 18篇 |
1985年 | 22篇 |
1984年 | 14篇 |
1983年 | 21篇 |
1982年 | 12篇 |
1981年 | 15篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 14篇 |
1972年 | 5篇 |
1967年 | 3篇 |
排序方式: 共有2581条查询结果,搜索用时 296 毫秒
21.
Rui Morimoto Chisato Yokomori Akiko Kikkawa Akira Izumi Hideki Matsumura 《Thin solid films》2003,430(1-2):230-235
In this paper, bulk-Si metal–oxide–semiconductor field effect transistors (MOSFETs) are fabricated using the catalytic chemical vapor deposition (Cat-CVD) method as an alternative technology to the conventional high-temperature thermal chemical vapor deposition. Particularly, formation of low-resistivity phosphorus (P)-doped poly-Si films is attempted by using Cat-CVD-deposited amorphous silicon (a-Si) films and successive rapid thermal annealing (RTA) of them. Even after RTA processes, neither peeling nor bubbling are observed, since hydrogen contents in Cat-CVD a-Si films can be as low as 1.1%. Both the crystallization and low resistivity of 0.004 Ω·cm are realized by RTA at 1000 °C for only 5 s. It is also revealed that Cat-CVD SiNx films prepared at 250 °C show excellent oxidation resistance, when the thickness of films is larger than approximately 10 nm for wet O2 oxidation at 1100 °C. It is found that the thickness required to stop oxygen penetration is equivalent to that for thermal CVD SiNx prepared at 750 °C. Finally, complementary MOSFETs (CMOSs) of single-crystalline Si were fabricated by using Cat-CVD poly-Si for gate electrodes and SiNx films for masks of local oxidation of silicon (LOCOS). At 3.3 V operation, less than 1.0 pA μm−1 of OFF leakage current and ON/OFF ratio of 107–108 are realized, i.e. the devices can operate similarly to conventional thermal CVD process. 相似文献
22.
An improved T -Ω method that can analyze magnetic fields produced not only by eddy currents but also by magnetizing currents is proposed. The method is applied to the analysis of 3-D eddy-current models with holes. The usefulness of the method is investigated by comparing calculated results with measured results and with results obtained by the A -Φ method. The T -Ω method has the advantage that the CPU time can be considerably reduced when most of the analyzed region is current-free and the eddy current flows two-dimensionally. The method is especially effective when the shape of the winding is simple and the distribution of magnetizing current is known beforehand. It is not effective when most of the analyzed region is current-carrying 相似文献
23.
Komoda M. Kawashima T. Arakane M. Aihara M. Fujiwara Y. Shinagawa J. 《Power Delivery, IEEE Transactions on》1991,6(2):541-545
A cable fault location instrument based on the detection of traveling wave currents was developed. It is different from the conventional pulse radar method based on voltage detection. Measurement is automated, and the distance to the fault point is displayed by merely pushing a switch. In a branched or crossbonded line, the fault point can be located without interference from the branched or the crossbonded point. Tests performed in both real and simulated lines confirmed the practical utility of this instrument 相似文献
24.
25.
Characterization of C-S-H from Highly Reactive β-Dicalcium Silicate Prepared from Hillebrandite 总被引:1,自引:1,他引:0
Yoshihiko Okada Hideki Ishida Kaori Sasaki J. Francis Young Takeshi Mitsuda 《Journal of the American Ceramic Society》1994,77(5):1313-1318
β-dicalcium silicate synthesized by thermal dissociation of hydrothermally prepared hillebrandite (Ca2 (SiO3 )(OH)2 ) exhibits extremely high hydration activity. Characterization of the hydrates obtained and investigation of the hydration mechanism was carried out with the aid of trimethylsilylation analysis, 29 Si magic angle spinning nuclear magnetic resonance, transmission electron microscopy selected area electron diffraction, and XRD. The silicate anion structure of C-S-H consisted mainly of a dimer and a single-chain polymer. Polymerization advances with increasing curing temperature and curing time. The C-S-H has an oriented fibrous structure and exhibits a 0.73-nm dreierketten in the longitudinal direction. On heating, the C-S-H dissociates to form β-C2 S. The temperature at which βC2 S begins to form decreases with increasing chain length of the C-S-H or as the Ca/Si ratio becomes higher. The high activity of β-C2 S is due to its large specific surface area and the fact that the hydration is chemical-reaction-rate-controlled until its completion. As a result, the hydration progresses in situ and C-S-H with a high Ca/Si ratio is formed. 相似文献
26.
27.
Fujiwara T. Ito M. Kasami T. Kataoka M. Okui J. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1991,37(2):379-384
The problem of distributing a Cartesian product file on multiple disks to maximize the parallelism for partial match queries is addressed. C. Faloutsos et al. (1989) have proposed an allocation method for Cartesian product files on multiple disks by using linear error-correcting codes. The performance of the allocation method is analyzed. Some conditions under which the allocation method is strictly optimal for queries with a given number of unspecified attributes are presented. A necessary and sufficient condition for a linear code to give a strictly optimal allocation method is discussed. Formulas for the average response time on queries with w unspecified attributes, denoted T w, in terms of the weight distribution of the code or its dual code, and formulas for the average response time T on all queries, are given. Several examples whose average response times T w or T are close to theoretical lower bounds are presented 相似文献
28.
A case of Waldenstr?m's macroglobulinemia (WM) (IgM-kappa type) associated with acute-onset demyelinating peripheral neuropathy is reported. A 49-year-old woman was admitted to our hospital because of general fatigue and recurrent syncope attacks. She was treated with vincristine, cyclophosphamide, epirubicin and prednisolone. By 10th hospital day, her clinical condition improved and serum viscosity was reduced. However, on the 21st hospital day, she suffered from rapidly progressive writing and gait disturbance. Neurological examination showed muscular atrophy and weakness in the distal part of four extremities. Deep tendon reflexes were diminished. There was no sensory deficit. Cerebrospinal fluid was normal. Anti-myelin associated glycoprotein activity of her serum was negative. Both motor and sensory nerve conduction velocities were markedly decreased. Biopsy of sural nerve revealed marked demyelination and onion bulb formation. There was IgM deposition on myelin sheath. Minimal axonal changes excluded the possibility of vincristine neuropathy. Plasmapheresis improved her symptoms, but nerve conduction velocities remained unchanged. Polyneuropathy associated with WM is usually gradual onset and sensory dominant. In this case, associated neuropathy was acute onset, progressive and motor dominant. This type of neuropathy in patients with WM is very rare. 相似文献
29.
30.
The total volume change included gel and surrounded water with the swelling of five types of speherical cross-linked dextran (Sephadex) that are either nonionic (G) or possess one of four different ionic groups in the same molecular skeleton: CM: sodium carboxymethyl, SP: sodium sulphopropyl, DEAE: diethylaminoethyl chloride, and QAE: diethyl-(2-hydroxypropyl) aminoethyl chloride. All have been studied by dilatometry. The total volume decreased with the swelling of all Sephadexes. The maximum changes of total volume with the swelling in water were all negatives of CM, G, SP, (DEAE, QAE), which decrease in that order. These values did not depend on the concentration of sodium chloride and were closely related to the maximum heats of swelling. Total volume changes occurred by the dissociation of the ionic group of dextran derivatives that subtracted the total volume change due to hydration of Sephadex skeleton from the total volume change: ?21.6 ± 3.1 μL mmol?1 for CM, ?2.8 ± 8.0 μL mmol?1 for SP, +13.2 ± 4.4 μL mmol?1 for DEAE, and +15.4 ± 4.6 μL mmol?1 for QAE. These values are assumed to be reflected in the quantities of ions-water interaction of Sephadexes. © 1994 John Wiley & Sons, Inc. 相似文献