全文获取类型
收费全文 | 5779篇 |
免费 | 384篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 73篇 |
综合类 | 4篇 |
化学工业 | 1502篇 |
金属工艺 | 136篇 |
机械仪表 | 177篇 |
建筑科学 | 164篇 |
矿业工程 | 8篇 |
能源动力 | 249篇 |
轻工业 | 1065篇 |
水利工程 | 42篇 |
石油天然气 | 50篇 |
无线电 | 353篇 |
一般工业技术 | 881篇 |
冶金工业 | 666篇 |
原子能技术 | 61篇 |
自动化技术 | 741篇 |
出版年
2024年 | 29篇 |
2023年 | 61篇 |
2022年 | 216篇 |
2021年 | 264篇 |
2020年 | 193篇 |
2019年 | 228篇 |
2018年 | 248篇 |
2017年 | 245篇 |
2016年 | 247篇 |
2015年 | 156篇 |
2014年 | 214篇 |
2013年 | 420篇 |
2012年 | 350篇 |
2011年 | 352篇 |
2010年 | 279篇 |
2009年 | 317篇 |
2008年 | 248篇 |
2007年 | 210篇 |
2006年 | 171篇 |
2005年 | 144篇 |
2004年 | 114篇 |
2003年 | 86篇 |
2002年 | 87篇 |
2001年 | 77篇 |
2000年 | 77篇 |
1999年 | 80篇 |
1998年 | 200篇 |
1997年 | 139篇 |
1996年 | 114篇 |
1995年 | 79篇 |
1994年 | 49篇 |
1993年 | 62篇 |
1992年 | 33篇 |
1991年 | 37篇 |
1990年 | 25篇 |
1989年 | 26篇 |
1988年 | 26篇 |
1987年 | 25篇 |
1986年 | 19篇 |
1985年 | 25篇 |
1984年 | 11篇 |
1983年 | 19篇 |
1981年 | 17篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1978年 | 21篇 |
1977年 | 19篇 |
1976年 | 24篇 |
1975年 | 8篇 |
1972年 | 10篇 |
排序方式: 共有6172条查询结果,搜索用时 15 毫秒
11.
Talita Moreira de Oliveira Nilda de Fátima Ferreira Soares Rodrigo Magela Pereira Kátia de Freitas Fraga 《Packaging Technology and Science》2007,20(2):147-153
Conservation of food products depends on product quality and packaging suitability. The objective of this work was to develop and evaluate the antimicrobial efficiency of natamycin‐incorporated film in the production process of Gorgonzola cheese. It aims to optimize the production process and increase shelf‐life and food safety for the consumer. Films with different concentrations of natamycin were produced and tested in Gorgonzola cheeses to evaluate its efficiency against Penicillium roqueforti on the cheese surface. Films with 2 and 4% natamycin presented satisfactory results for fungus inhibition and the amount of natamycin released to the cheese was below that allowed by the legislation. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
12.
S. Danto P. Houizot C. Boussard‐Pledel X.‐H. Zhang F. Smektala J. Lucas 《Advanced functional materials》2006,16(14):1847-1852
Conditions of formation of bulk tellurium chalcogenide glasses, containing 70–80 at % Te associated to Ga and Ge are described. The characteristic temperatures are measured: the glass‐transition temperature, Tg, is situated in the range 140–185 °C and the difference Tx – Tg, where Tx is the onset crystallization temperature, is in the range 76–113 °C. Moreover, the optical transmission window is exceptional, ranging from 1.99 μm in the bandgap up to 28 μm in the phonon region. Developed within the framework of requirements for the Darwin mission (a search for and study of extrasolar planets), feasibility of infrared optical fibers formed from these glasses is studied. Drawing experiments are conducted with the glass Ga2‐Ge3Te15, which possesses the maximum Tx – Tg, and a first optical fiber is presented. 相似文献
13.
The differentiation method of model reduction is shown to be equivalent to forming successive ratios of multipoint Taylor polynomial approximation of the numerator and denominator of the transfer function, respectively. This reformulation allows the method to be applied entirely through a Routh-type array structure. Strong links are seen to exist between the method and other stability preserving methods via this Routh-type structure 相似文献
14.
C Guimar?es Madeira SA Jorge S Kakehashi I de Oliveira 《Canadian Metallurgical Quarterly》1996,30(2):217-228
The disposition behavior of trientine, a selective copper-chelating drug for Wilson's disease, and its metabolites in normal patients with Wilson's disease and rats were studied. A high concentration of metabolites appeared in blood samples of patients and rats in the early stage after administration of trientine. Furthermore, large amount of trientine metabolites were excreted into the urine of patients. These results suggest that trientine is remarkably subjected to a first-pass effect. The drug concentration area under the curve (AUC) of the unchanged form and the metabolites of trientine in patients was not dependent on the administered dosage. It seems that the absorption process is an important factor for the disposition behavior of trientine, we have also investigated the uptake characteristics of trientine by rat intestinal brush-border membrane vesicles. The uptake characteristics of trientine were similar to the physiological polyamines, spermine and spermidine. The uptake rate of trientine was dose-dependently inhibited by spermine and spermidine. Moreover, spermine competitively inhibited the uptake of trientine with a Ki value of 18.6 muM. This value is very close to the Km value for spermine (30.4 muM). These data suggested that the uptake mechanism of trientine in rat small intestinal brush-border membrane vesicles was almost identical to that of spermine and spermidine, and that the physiological polyamines seem to have the ability to inhibit the absorption of trientine from the gastrointestinal tract. 相似文献
15.
16.
F. Cœuret E. Oliveira Vilar E. Bezerra Cavalcanti 《Journal of Applied Electrochemistry》2002,32(10):1175-1182
The paper deals with carbon fibre cloth electrodes, employed in the fabrication of composite materials. The electrical conductivity of single bundles, groups of bundles and cloth is studied. Ohm's law applies to the electrical conduction in the direction of the fibre length, but bundle conductivity decreases with the number of fibres in the bundle. Electrochemical mass transfer between a flowing electrolyte and a cloth arranged as a flow-through or a flow-by porous electrode indicates the existence of double porosity in the material. Due to double porosity, only the external surface of the cloth works as an electrode. This finding shows that the material is not suitable for such an application. 相似文献
17.
Summary A synthetic approach for the preparation of poly(aryl ether amides) has been developed where the generation of an aryl ether
linkage was the polymer-forming reaction. The amide moiety was found to be sufficiently electron withdrawing to activate halosubstituents,
towards nucleophilic aromatic substitution polymerizations, analogous to conventional activating groups (i.e, sulfone, ketone
etc.). Several new A-B monomers, 4-fluoro-N-(4-hydroxyphenyl)benzamide, 1, and 4-fluoro-N-(3-hydroxyphenyl)benzamide, 2, which contain both an amide-activated fluoro group and a phenol group were prepared and their self polymerization studied.
Compounds 1 and 2 were prepared by the condensation of 4-fluorobenzoyl chloride with either 4-or 3-aminophenol, respectively. The polymerizations
were carried out in an N-methyl-2-pyrrolidone (NMP)/N-cyclohexyl-2-pyrrolidone (CHP) solvent mixture in the presence of potassium
carbonate. Several new high molecular weight poly(aryl ethers) were prepared by this route with Tg's in the 225 °C range. 相似文献
18.
Wax crystallization can cause serious damage to petroleum flow because as the viscosity increases, there is organic deposition in the pipe lines, which causes oil production reduction. Ethylene–vinyl acetate copolymers (EVA) are used as an alternative to prevent such problems. The influence of EVA copolymers on the properties of wax synthetic systems, composed of a solvent mixture and paraffin and petroleum asphalt residue (PAR), was evaluated in this work. The performance of EVA as a wax inhibitor depends on the molecular weight and vinyl acetate content of the copolymer and on the presence of the asphalt fraction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1337–1348, 2002 相似文献
19.
20.