全文获取类型
收费全文 | 11327篇 |
免费 | 810篇 |
国内免费 | 44篇 |
专业分类
电工技术 | 207篇 |
综合类 | 68篇 |
化学工业 | 3036篇 |
金属工艺 | 245篇 |
机械仪表 | 334篇 |
建筑科学 | 395篇 |
矿业工程 | 36篇 |
能源动力 | 490篇 |
轻工业 | 1937篇 |
水利工程 | 140篇 |
石油天然气 | 84篇 |
无线电 | 769篇 |
一般工业技术 | 1800篇 |
冶金工业 | 757篇 |
原子能技术 | 82篇 |
自动化技术 | 1801篇 |
出版年
2024年 | 40篇 |
2023年 | 129篇 |
2022年 | 369篇 |
2021年 | 540篇 |
2020年 | 397篇 |
2019年 | 430篇 |
2018年 | 481篇 |
2017年 | 441篇 |
2016年 | 485篇 |
2015年 | 368篇 |
2014年 | 532篇 |
2013年 | 907篇 |
2012年 | 723篇 |
2011年 | 849篇 |
2010年 | 586篇 |
2009年 | 631篇 |
2008年 | 559篇 |
2007年 | 454篇 |
2006年 | 400篇 |
2005年 | 305篇 |
2004年 | 268篇 |
2003年 | 319篇 |
2002年 | 317篇 |
2001年 | 202篇 |
2000年 | 139篇 |
1999年 | 117篇 |
1998年 | 229篇 |
1997年 | 155篇 |
1996年 | 126篇 |
1995年 | 105篇 |
1994年 | 71篇 |
1993年 | 79篇 |
1992年 | 46篇 |
1991年 | 48篇 |
1990年 | 39篇 |
1989年 | 30篇 |
1988年 | 41篇 |
1987年 | 26篇 |
1986年 | 24篇 |
1985年 | 26篇 |
1984年 | 26篇 |
1983年 | 12篇 |
1982年 | 20篇 |
1981年 | 7篇 |
1980年 | 17篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 18篇 |
1975年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
Maribel Plascencia‐Jatomea Miguel A Olvera‐Novoa Jos Luis Arredondo‐Figueroa George M Hall Keiko Shirai 《Journal of the science of food and agriculture》2002,82(7):753-759
This study provides information on the use of shrimp head silage protein hydrolysate (SPH) as an alternative protein source for tilapia feeding. Six diets (28% protein, 12% lipid) were prepared where fishmeal protein was replaced at levels of 0 (control), 10, 15, 20, 25 and 30% with the hydrolysate. The diets were supplied to Nile tilapia fry (338 mg initial weight) stocked in plastic recirculating 20 l tanks (10 animals per tank), with three replicates per treatment. After an 8 week experimental period, fish fed the diets containing 10 and 15% SPH showed significantly better performance in terms of final body weight, weight gain (%), mean daily weight gain (mg day?1), specific growth ratio and feed conversion ratio than those fed the control diet (fishmeal as protein source) and higher‐SPH diets. It is concluded that shrimp head hydrolysate is a promising alternative protein source for tilapia feeding, improving growth ratio at dietary inclusion levels as high as 15%. In addition, the diets with added shrimp silage protein were well accepted by the fish, which avidly consumed the feed during the experiment. © 2002 Society of Chemical Industry 相似文献
45.
46.
47.
Cypriano G da Trindade Neto Ana LP Fernandes Ana IB Santos Waldenice A Morais Marcos VM Navarro Tereza NC Dantas Mrcia R Pereira Jos LC Fonseca 《Polymer International》2005,54(4):659-666
Complexation of chitosan in aqueous solutions by low molecular weight electrolytes is one of the simplest methods for the preparation of aqueous chitosan dispersions. In this work, the influence of storage time, sulfate concentration, method of preparation and surfactant content on some properties of the resultant chitosan dispersions (turbidity, viscosity and zeta potential) was analyzed. Turbidimetry was adequate to monitor the formation of particles, while viscometry was suitable to monitor changes in the dispersing phase. An analysis of the properties of these systems, mainly in terms of particle–particle and macromolecule–macromolecule interactions was carried out. Copyright © 2004 Society of Chemical Industry 相似文献
48.
The thermal and mechanical properties and the morphologies of blends of poly(propylene) (PP) and an ethylene–(vinyl alcohol) copolymer (EVOH) and of blends of PP/EVOH/ethylene–(methacrylic acid)–Zn2+ ionomer were studied to establish the influence of the ionomer addition on the compatibilization of PP/EVOH blends and on their properties. The oxygen transmission rate (O2TR) values of the blends were measured as well. PP and EVOH are initially incompatible as was determined by tensile tests and scanning electronic microscopy. Addition of the ionomer Zn2+ led to good compatibility and mechanical behaviour was improved in all blends. The mechanical properties on extruded films were studied for 90/10 and 80/20 w/w PP/EVOH blends compatibilized with 10 % of ionomer Zn2+. These experiments have shown that the tensile properties are better than in the injection‐moulded samples. The stretching during the extrusion improved the compatibility of the blends, diminishing the size of EVOH domains and enhancing their distribution in the PP matrix. As was to be expected, the EVOH improved the oxygen permeation of the films, even in compatibilized blends. Copyright © 2004 Society of Chemical Industry 相似文献
49.
Two types of composite were prepared, based on a thermoplastic polymer, polyvinylidene fluoride (PVDF), and an elastomer, ethylene‐propylene‐diene terpolymer (EPDM), respectively. We obtained both series by addition of an inorganic proton‐conducting antimonic acid derivative (HSb) and polystyrene crosslinked with a small percentage of divinylbenzene (PS‐co‐DVB). From these composites, membranes were obtained and subjected to a heterogeneous‐phase sulfonation reaction with chlorosulfonic acid. All experimental materials were characterized from a morphological and electrical point of view, by means of techniques such as differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), non‐isothermal crystallization and complex impedance analysis. Copyright © 2005 Society of Chemical Industry 相似文献
50.
V. Anjos M.J.V. Bell E.F. da Silva Jr. R.W.A. Franco I.A. Esquef 《Microelectronics Journal》2005,36(11):977-980
In this paper we report the use of photothermal techniques such as Thermal lens (TL) spectrometry, Photoacoustic and heat capacity, ρcp, to determine the thermo-optical parameters, such as thermal conductivity (K), thermal diffusivity (D), specific heat (cp) and the optical path dependence with temperature (ds/dT), of an undoped polycrystalline 3C-SiC. To our knowledge, this is the first time that Thermal lens technique is used for wide band-gap systems. Results obtained for the polycrystalline sample with TL technique indicates that ds/dT is negative at room temperature. Moreover, the obtained values of thermal diffusivity and thermal conductivity are in good agreement with that found in the literature, indicating that the phototermal techniques can be used to obtain the referred parameters in circumstances where other techniques cannot be used, for example, in harsh environments. 相似文献