全文获取类型
收费全文 | 2488篇 |
免费 | 165篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 31篇 |
综合类 | 4篇 |
化学工业 | 646篇 |
金属工艺 | 83篇 |
机械仪表 | 118篇 |
建筑科学 | 96篇 |
矿业工程 | 4篇 |
能源动力 | 120篇 |
轻工业 | 414篇 |
水利工程 | 8篇 |
石油天然气 | 27篇 |
无线电 | 175篇 |
一般工业技术 | 414篇 |
冶金工业 | 165篇 |
原子能技术 | 19篇 |
自动化技术 | 341篇 |
出版年
2024年 | 13篇 |
2023年 | 32篇 |
2022年 | 62篇 |
2021年 | 103篇 |
2020年 | 74篇 |
2019年 | 85篇 |
2018年 | 102篇 |
2017年 | 102篇 |
2016年 | 134篇 |
2015年 | 98篇 |
2014年 | 139篇 |
2013年 | 298篇 |
2012年 | 121篇 |
2011年 | 145篇 |
2010年 | 139篇 |
2009年 | 130篇 |
2008年 | 106篇 |
2007年 | 80篇 |
2006年 | 71篇 |
2005年 | 46篇 |
2004年 | 39篇 |
2003年 | 31篇 |
2002年 | 41篇 |
2001年 | 26篇 |
2000年 | 29篇 |
1999年 | 20篇 |
1998年 | 42篇 |
1997年 | 21篇 |
1996年 | 37篇 |
1995年 | 19篇 |
1994年 | 15篇 |
1993年 | 17篇 |
1992年 | 15篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 15篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 23篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 17篇 |
1979年 | 9篇 |
1978年 | 14篇 |
1977年 | 9篇 |
1976年 | 22篇 |
1975年 | 13篇 |
排序方式: 共有2665条查询结果,搜索用时 31 毫秒
1.
2.
Hasrul Abdi Hasibuan Azis Boing Sitanggang Nuri Andarwulan Purwiyatno Hariyadi 《International Journal of Food Science & Technology》2021,56(9):4549-4558
This research aimed to produce triacylglycerols fraction rich in palmitic acid (PA) at the sn-2 position from hard palm stearin (HPS) through acetone fractionation. Fractionations were done at HPS-to-acetone ratios of 1:3, 1:5 and 1:7 (w/v) and at temperatures of 25, 30 and 35 °C for 3 h. Triacylglycerols with PA at the sn-2 position, such as tripalmitoylglycerol (PPP) and dipalmitoyl-stearoyl-glycerol (PPS), were concentrated in the solid fraction, obtained after separation by filtration. The optimal fractionation conditions were at a HPS-to-acetone ratio of 1:5 (w/v) and 30 °C. The total PPP and PPS content was more than 91%, with a corresponding yield of more than 59%. Triacylglycerols obtained were composed of more than 91% PA in which 88% were at the sn-2 position. Conclusively, the solvent fractionation is a suited alternative method for the preparation of triacylglycerols used for the enzymatic synthesis of 1,3-dioleoyl-2-palmitoylglycerol which is the main triacylglycerol for human milk fat substitute. 相似文献
3.
Bican Osman Bayça Salih Uğur Kuleyin Hamdi Gümrük Recep 《Metal Science and Heat Treatment》2021,63(3-4):156-162
Metal Science and Heat Treatment - The effect of solid boronizing at 950°C for 2 and 4 h on the phase composition, microstructure, hardness and abrasive wear of steel AISI 304L is studied... 相似文献
4.
5.
R. Murgan F. Razak D. R. Tilley T. Y. Tan J. Osman M. N. A. Halif 《Computational Materials Science》2004,30(3-4):468-473
We derive an expression for transmittivity (TSHG) of second harmonic generation (SHG) signals from a ferroelectric (FE) film. Intensities of up and down fields in the medium are investigated in relation to TSHG. The derivations are made based on undepletion of input fields and nonlinear wave equation derived from the Maxwell equations. We present two cases: film without mirrors and with partial mirrors. Expressions for the newly derived nonlinear susceptibility coefficients of SHG for real crystal symmetry [J. Opt. Soc. Am. B 19 (2002) 2007] are used to get more realistic results. Variations in TSHG with respect to film thickness are illustrated. 相似文献
6.
Maher M. Osman Mounir M. Abd El-Malek Aida B. Tadros Atef M. Michael 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,62(1):46-52
4-Amino-3-thio-1,24-triazolidine (L1) and 4-amino-5-thio-1,3,4-thiadiazole (LII) as well as their metal complexes of the general formulae MLI·2H2O and MLIICl (M; Pb(II), Cd(II) and Zn(II)) were prepared. With Sn(II), we obtained Sn(LI)2·2H2O and SnLIICl, respectively. The structures of the compounds were identified through elemental analysis, and IR and UV spectra measurements, in addition to thermal analysis in case of the metal complexes. The antifouling properties of the compounds were tested by their incorporation into paint formulations which were applied to PVC substrates and tested in water from Alexandria western harbour. When the compounds were added at 17·5% by volume, the coated panels were fouled after 3 months of immersion. The addition of 6·7% by volume of tributyltin oxide to 15·8% of the prepared compounds in one formulation elevated the paint efficiency and prevented fouling for 11 months. Paint containing solely tributyltin oxide at the same concentration was inactive against algae. 相似文献
7.
8.
Physically based simulation of human hair is a well studied and well known problem. But the “pure” physically based representation of hair (and other animation elements) is not the only concern of the animators, who want to “control” the creation and animation phases of the content. This paper describes a sketch-based tool, with which a user can both create hair models with different styling parameters and produce animations of these created hair models using physically and key frame-based techniques. The model creation and animation production tasks are all performed with direct manipulation techniques in real-time. 相似文献
9.
Ibrahim H. Osman Nicos Christofides 《International Transactions in Operational Research》1994,1(3):317-336
The capacitated clustering problem (CCP) is the problem in which a given set of weighted objects is to be partitioned into clusters so that the total weight of objects in each cluster is less than a given value (cluster ‘capacity’). The objective is to minimize the total scatter of objects from the ‘centre’ of the cluster to which they have been allocated. A simple constructive heuristic, a R-interchange generation mechanism, a hybrid simulated annealing (SA) and tabu search (TS) algorithm which has computationally desirable features using a new non-monotonic cooling schedule, are developed. A classification of the existing SA cooling schedules is presented. The effects on the final solution quality of the initial solutions, the cooling schedule parameters and the neighbourhood search strategies are investigated. Computational results on randomly generated problems with size ranging from 50 to 100 customers indicate that the hybrid SA/TS algorithm out-performs previous simulated annealing algorithms, a simple tabu search and local descent algorithms. 相似文献
10.
W Graf M Dahlberg MM Osman L Holmberg L P?hlman B Glimelius 《Canadian Metallurgical Quarterly》1997,43(2):133-137
OBJECTIVE: The incidence of back pain in children in our country is unknown. Several causes can produce this symptom, but it is necessary to rule out pathologies that require specific treatments. The goal of this work was to study the incidence and the etiology of back pain in children in our country. PATIENTS AND METHODS: We present a prospective study done in our Orthopedic Department during a period of 7 months. Twenty-two patients were referred with back pain of at least two months duration. The incidence was 2.9% compared to the total number of patients. The average age ranged from 7 to 17 years. RESULTS: A careful history and a radiological examination diagnosed 50% (11 cases) of the causes of backache in the present study. An idiopathic etiology was the most frequent cause and represented 9 patients (41%). In the remaining 12 cases (59%) pathological causes that required special treatment were identified including 2 cases of Scheuermann disease, 4 cases of painful scoliosis, 3 spondylolysis with spondylolisthesis, 2 cases of discitis, 1 benign neoplasm and 1 psychogenic cause. CONCLUSIONS: We recommend conservative management with the use of medication for relief of pain and physical therapy in the idiopathic cases. In the remaining cases, the specific treatment of the disease can improve the back pain. 相似文献