全文获取类型
收费全文 | 6862篇 |
免费 | 453篇 |
国内免费 | 43篇 |
专业分类
电工技术 | 93篇 |
综合类 | 18篇 |
化学工业 | 1791篇 |
金属工艺 | 182篇 |
机械仪表 | 267篇 |
建筑科学 | 267篇 |
矿业工程 | 5篇 |
能源动力 | 384篇 |
轻工业 | 681篇 |
水利工程 | 92篇 |
石油天然气 | 78篇 |
武器工业 | 4篇 |
无线电 | 774篇 |
一般工业技术 | 1319篇 |
冶金工业 | 255篇 |
原子能技术 | 50篇 |
自动化技术 | 1098篇 |
出版年
2024年 | 16篇 |
2023年 | 124篇 |
2022年 | 234篇 |
2021年 | 425篇 |
2020年 | 343篇 |
2019年 | 368篇 |
2018年 | 432篇 |
2017年 | 375篇 |
2016年 | 399篇 |
2015年 | 267篇 |
2014年 | 467篇 |
2013年 | 682篇 |
2012年 | 430篇 |
2011年 | 532篇 |
2010年 | 334篇 |
2009年 | 274篇 |
2008年 | 211篇 |
2007年 | 161篇 |
2006年 | 152篇 |
2005年 | 94篇 |
2004年 | 85篇 |
2003年 | 76篇 |
2002年 | 48篇 |
2001年 | 62篇 |
2000年 | 57篇 |
1999年 | 40篇 |
1998年 | 54篇 |
1997年 | 42篇 |
1996年 | 56篇 |
1995年 | 40篇 |
1994年 | 36篇 |
1993年 | 33篇 |
1992年 | 30篇 |
1991年 | 33篇 |
1990年 | 23篇 |
1989年 | 18篇 |
1988年 | 29篇 |
1987年 | 31篇 |
1986年 | 29篇 |
1985年 | 28篇 |
1984年 | 23篇 |
1983年 | 20篇 |
1982年 | 18篇 |
1981年 | 12篇 |
1979年 | 14篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1976年 | 14篇 |
1975年 | 10篇 |
1970年 | 10篇 |
排序方式: 共有7358条查询结果,搜索用时 312 毫秒
101.
In this paper, the problem of fault detection for continuous‐time switched systems under asynchronous switching is investigated. The designed fault detection filter is assumed to be asynchronous with the original systems. Attention is focused on designing a fault detection filter such that the estimation error between the residual and the fault is minimized in the sense of H ∞ norm. By employing piecewise Lyapunov function and average dwell time techniques, a sufficient condition for the existence of such a filter is exploited in terms of certain linear matrix inequalities. Finally, an example of a switched electrical circuit is provided to illustrate the effectiveness of the proposed approach. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
102.
Mehdi Qasim Jinan Al‐Dabbagh Naser Mahmoud Ahmed V.G. Chigrinov Gurumurthy Hegde 《Journal of the Society for Information Display》2014,22(4):187-190
Indium tin oxide‐coated thin films (200 nm) are deposited on glass substrates by using R.f. sputtering technique. Here, we investigate the influence of new technique of treatment, which is called as “oil thermal annealing” on the nano‐structured indium tin oxide thin films at fixed temperature (150 °C) which improves adhesion strength, electrical conductivity and optical properties (transmittance) of the films. Oil thermal annealing is used to reduce inherent defects that may be introduced during the prepared thin film and cooling processes. Proposed technique is highly suitable for liquid crystal displays, solar cells and organic light emitting diodes, and many other display‐related applications. 相似文献
103.
M. S. Miskandar Y. B. Che Man M. S. A. Yusoff R. Abdul Rahman 《Journal of the American Oil Chemists' Society》2002,79(9):931-936
The effects of scraped-surface tube cooler temperatures on the isothermal solid fat content (SFC) of palm oil margarine during
processing and on margarine consistency (yield value, g/cm2), SFC, and polymorphic changes in storage were studied. SFC was measured in the mixing tank after leaving the tube cooler
and the pin worker. The SFC at the tube cooler exit was proportional to the amount of cooling; a higher SFC was produced by
more extreme cooling treatment. The SFC of all margarines were reduced in the pin worker, and the reduction was related to
the initial SFC profile of palm oil. Margarine samples were stored at 28°C for 28 d and tested daily. Margarine processed
at 25°C in the tube cooler had the highest consistency and the least change in SFC, but by the second week crystals had transformed
into the β form. Uniform product consistency and SFC were observed in margarines processed at 20 and 15°C. These margarines
retained the β′ crystal form for 3 and 4 wk, respectively. The best palm oil margarine was obtained with a tube cooler temperature
of 15°C and a residence time of 1.8 min. 相似文献
104.
Rassoul Dinarvand Mohammed Massoud Alimorad Massoud Amanlou Hamid Akbari 《应用聚合物科学杂志》2006,101(4):2377-2383
Polyadipic anhydride (PAA), an aliphatic polyanhydride, and polytrimethylene carbonate (PTMC), an aliphatic polycarbonate, were synthesized via ring opening polymerization of oxepan‐2,7‐dione and melt‐condensation of trimethylene carbonate (1,3 dioxan‐2‐one), respectively. PTMC–PAA blend microspheres containing different ratios of buprenorphine HCl (2, 5, and 10%) were prepared by an oil‐in‐oil emulsion solvent removal method. Microspheres with different ratios of PTMC–PAA (85/15, 70/30, and 55/45) containing 5% buprenorphine HCl were prepared. Microspheres were spherical with visible cracks and pores on the surface. The average particle size of microspheres was around 200 μm for all microspheres. Drug loading efficiency of PTMC–PAA microspheres (85/15, 70/30, and 55/45) was 97.2, 95.2, and 70.2%, respectively. With the increase in the PTMC ratio, the melting point and the enthalpy of melting were both decreased. The mechanism for drug release from PTMC–PAA blend microspheres were generally a combination of drug diffusion through polymers and biodegradation of the polymers. In first three days, the release from microspheres followed zero order kinetics and was dependent on the PAA content. After three days the drug release from microspheres followed first order kinetics. In conclusion it was demonstrated that buprenorphine HCl release from microspheres could be successfully controlled by using different ratios of PTMC–PAA blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2377–2383, 2006 相似文献
105.
Mahmoud A.‐Halim Abdel‐Goad 《应用聚合物科学杂志》2004,93(1):37-40
Agricultural residues (cotton straw) were added as very small particles to polystyrene (PS) at different weight ratios by using a melt‐mixing technique. The dynamic mechanical tests were performed over a wide range of temperatures and frequencies by using an ARES rheometer (Rheometrics Scientific) operated in the dynamic mode. The dynamic mechanical properties in terms of the storage modulus (G′), loss modulus (G″), compliance moduli, loss tangent, and dynamic viscosity were studied and compared for PS and PS composite. The results showed that the dynamic mechanical moduli and viscosity were found to increase with the addition of cotton straw and rise further with its loading increasing. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 37–40, 2004 相似文献
106.
The Sr(B'0.5 Ta0.5 )O3 ceramics where B'=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, and Yb have been prepared by the conventional solid-state ceramic route and their microwave dielectric properties have been investigated. The structure and microstructure of the ceramics have been characterized by X-ray diffraction and scanning electron microscope techniques. The relative permittiviy (ɛr ) varies linearly with B'-site ionic radii, except for La, and the temperature coefficient of resonant frequency (τf ) varies linearly with the tolerance factor. The Sr(B'0.5 Ta0.5 )O3 ceramics have ɛr in the range 25.9–32, Q u × f =4500–54 300 GHz, and τf =−79 to −42 ppm/°C. A slight deviation from stoichiometry affects the dielectric properties of these double perovskites. Partial substitution of Ba for Sr could tune the dielectric properties. Addition of rutile (TiO2 ) lowered the sintering temperature and improved the dielectric properties of Sr(B'0.5 Ta0.5 )O3 ceramics. 相似文献
107.
108.
The response of lentil grown under rainfed conditions to directly applied and residual phosphorus (P) was described by a modified Mitscherlich equation, accounting for the effects of rainfall on (1) potential yield, and (2) the availability of soil-P to the crop. The response of lentil yield to directly applied and residual P was studied in two-course cereal–lentil rotational trials under rainfed conditions in a Mediterranean-type environment. Cereal crops were grown at different P application rates during 4 growing seasons at 3 sites, representing different rainfall zones in northwest Syria. Lentil (Lens culinaris Med.) was grown during 4 seasons at the same sites, each lentil crop following a cereal crop. In 3 out of 4 lentil-growing seasons, additional P was applied to lentil in subplots to compare the residual and direct effects of P application. The initial contents of extractable soil-P (P-Olsen) were low at all sites, in the range of 2–5 ppm P. Under the conditions of the experiments, lentil appeared to benefit slightly more from P applied to the preceding wheat crop (residual P) than from directly applied P. It is shown that the modified Mitscherlich equation could be used as a basis for P fertilizer recommendations for rainfed farming. As for lentil, it was concluded that a single application of P to the wheat crop in a wheat/lentil rotation could reduce the cost of lentil production, without reducing lentil yield. 相似文献
109.
110.
Natália F. C. Vargas Mahmoud S. Alkathy José A. Eiras Valmor Roberto Mastelaro Manuel H. Lente 《Journal of the American Ceramic Society》2021,104(6):2600-2609
In this work, the influence of the sintering temperature on the physical properties of (Pb0.8La0.2)(Ti0.9Ni0.1)O3 (PLT-Ni) ceramics is reported. The experimental data revealed that the energy band gap of PLT-Ni ceramics could be tailored from approximately 2.7 to 2.0 eV by changing the sintering temperature from 1100°C to 1250°C. It is demonstrated that the simple substitution of Ti4+ by Ni2+ cations is effective to decrease the intrinsic band gap while increasing the tetragonality factor and the spontaneous polarization. However, the additional red-shift observed in the absorption edge of the PLT-Ni with increasing the sintering temperature was associated with a continuous increase in the oxygen vacancies () amount. It is believed that the impact of the creation of these thermally induced is manifold. The presence of and Ni2+ ions generate the Ni2+- defect-pairs that promoted both a decrease in the intrinsic band gap and an additional increase of the tetragonality factor, consequently, increasing the spontaneous polarization. The creation of Ni2+- defects also changed the local symmetry of Ni2+ ions from octahedral to a square pyramid, thus lifting the degeneracy of the Ni2+ 3d orbitals. With the increase in the sintering temperature, lower-energy absorbing intraband states were also formed due to an excess of , being responsible for an add-on shoulder in the absorption edge, extending the light absorption curve to longer wavelengths and leading to an additional absorption in “all investigated” spectrum as well. 相似文献