全文获取类型
收费全文 | 1751篇 |
免费 | 18篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 8篇 |
综合类 | 1篇 |
化学工业 | 106篇 |
金属工艺 | 19篇 |
机械仪表 | 21篇 |
建筑科学 | 16篇 |
能源动力 | 15篇 |
轻工业 | 29篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 75篇 |
一般工业技术 | 107篇 |
冶金工业 | 1231篇 |
原子能技术 | 7篇 |
自动化技术 | 130篇 |
出版年
2024年 | 3篇 |
2023年 | 8篇 |
2022年 | 24篇 |
2021年 | 22篇 |
2020年 | 31篇 |
2019年 | 26篇 |
2018年 | 20篇 |
2017年 | 16篇 |
2016年 | 27篇 |
2015年 | 14篇 |
2014年 | 16篇 |
2013年 | 21篇 |
2012年 | 30篇 |
2011年 | 28篇 |
2010年 | 13篇 |
2009年 | 29篇 |
2008年 | 22篇 |
2007年 | 24篇 |
2006年 | 9篇 |
2005年 | 20篇 |
2004年 | 13篇 |
2003年 | 16篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 38篇 |
1998年 | 411篇 |
1997年 | 208篇 |
1996年 | 128篇 |
1995年 | 89篇 |
1994年 | 66篇 |
1993年 | 81篇 |
1992年 | 20篇 |
1991年 | 21篇 |
1990年 | 21篇 |
1989年 | 28篇 |
1988年 | 24篇 |
1987年 | 24篇 |
1986年 | 16篇 |
1985年 | 13篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 15篇 |
1977年 | 35篇 |
1976年 | 57篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 2篇 |
排序方式: 共有1771条查询结果,搜索用时 15 毫秒
41.
A one-dimensional steady-state mathematical model has been developed to simulate the process of calcination of petroleum coke in a rotary kiln. A simulation is made to reproduce the operating conditions prevailing during a normal working day, in order to validate the model, and to study the effects of the main process control variables. It has been found that of the energy provided by combustion, 59.5 % comes from hydrogen, 14.6 % from the carbon of the coke bed, 13.8 % from coke dust, 11.3 % from methane and 0.8 % from tar. A comparison with existing models is made to identify eventual similarities between the various kilns under study. It appears that maximum coke temperature occurs at 45 to 55 % of kiln length, while volatile matters evolution takes place between 5 and 60 % of kiln length, measured from feed end. 相似文献
42.
We report a novel method of polyimide (PI) synthesis from prepolymers based on dianhydrides and diacetyl derivatives of aromatic diamines that facilitate the preparation of a melt processable mixture at 300 ± 10°C of the prepolymer and magnetic Nd‐Fe‐B alloy to provide PI‐bonded magnets with enhanced properties. It is shown that chemical structure of the prepolymers strongly influences viscosity behavior via crystallization of the oligoimide in the melt, leading to formation of PI with rigid‐rod like structure. This structural ordering of the prepolymers based on diacetyl derivative of diamine used in this study, if not controlled, leads to exponential increase of melt viscosity with time, making it practically impossible to prepare melt processable mixture of the magnetic particles and the PI prepolymers at elevated temperatures. The results obtained demonstrate that appropriate dianhydrides and diacetyl derivatives of diamines that do not lead to crystallization of oligoimides in prepolymer mixture can be used under controlled processing conditions to prepare melt‐processable PI‐bonded magnets containing rigid‐rod like PI structure that significantly increases thermal stability of the magnets. The temperature dependencies of the magnetic properties of the PI‐bonded magnets under conditions that they are likely to encounter during their service life were found to be remarkably similar to that of commercial thermoplastic magnets such as injection‐molded nylon magnets. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 478–485, 2006 相似文献
43.
Gerhard Maier Vendula Knopfova Brigitte Voit Pham Huu Ly Bui Tien Dung Do Bich Thanh 《大分子材料与工程》2004,289(10):927-932
Summary: Segmented block copolymers, consisting of non‐polar soft segments from hydroxyl‐terminated liquid natural rubber (HTNR) and polar hard segments from α,ω‐diisocyanato telechelics obtained by “criss‐cross”‐cycloaddition, have been synthesized. The block copolymer formation took place under relatively mild reaction conditions at 80 °C in dichloroethane in the presence of dibutyltin dilaurate as a catalyst. The resulting block copolymers were characterized by spectroscopic techniques (1H NMR, FTIR, UV‐vis spectroscopy) as well as GPC for molar mass determination. The block copolymers were compression molded in a hot stage press, and the resulting samples were characterized by DSC and stress‐strain measurement. The solubility and phase morphology of the materials have also been studied.
44.
A good performance of the solid‐liquid unit operation is required for the economical exploitation of the Bayer process. A computational fluid dynamics (CFD) model simulating the operation of the last washing stage mud thickener of a large Canadian alumina plant is presented. The parametric study of the impact of changes in four parameters shows that the diameter of flocculated red mud particles, the feed flow rate and the radius of the feed well are critical parameters for the operation of the thickener. 相似文献
45.
G. A. Tul'chinskii Bui Tkhyk Khet 《Power Technology and Engineering (formerly Hydrotechnical Construction)》1991,25(6):364-367
1. | The equipment of the Hoabinh hydroelectric plant operates in conformity with the specified parameters and ensures utilization of the installed capacity in the power system of North Vietnam. Further increase in the effectiveness of utilization of the plant capacity and of its specific share in the base portion of the load graph are determined by development of the transmission line system for supply to the consumers and the interconnection with the power system of central Vietnam. |
2. | As a result of the investigations and the introduced measures for realization of the multistage personnel training system, safe and accident-free operation has been ensured for operation of the first units under conditions of combination with construction-erection work in the underground complex of the hydroelectric plant. |
46.
Cell-free apoptosis in Xenopus egg extracts: inhibition by Bcl-2 and requirement for an organelle fraction enriched in mitochondria 总被引:1,自引:0,他引:1
Apoptotic cell death involves a ritual series of morphological changes, presumably reflecting a conserved molecular pathway. We now report that the nuclear events typical of apoptosis can be reproduced in "apoptotic" Xenopus egg extracts. In this cell-free system, nuclear assembly and protein import are initially normal; after 2-4 hr, however, a process of nuclear destruction ensues involving chromatin condensation and the shrinkage and fragmentation of the nuclei. This apoptotic process, which also occurs in nuclei added exogenously, is blocked by the addition of baculovirus-expressed Bcl-2 protein. To block the disintegration of nuclei that are added later, Bcl-2 must be present during this latent period. "Apoptosis" in these extracts requires a dense organelle fraction enriched in mitochondria. The cell-free system described here provides a novel tool for understanding intracellular events in apoptosis and the inhibitory function of Bcl-2. 相似文献
47.
Tammy L. Smith Divakaran Masilamani Long Kim Bui Raymond Brambilla Yash P. Khanna Kristina A. Garbriel 《应用聚合物科学杂志》1994,52(5):591-596
Nucleating agents increase the impact strength, tensile strength, and tensile elasticity modulus of semicrystalline polymers. Nucleating agents also decrease product cycle times, resulting in a cost savings per product unit. We have synthesized and tested 15 compounds as nucleactors for polypropylene. Of these, trinapthylidene sorbitol, tri-(4-methyl-1-naphthylidene)sorbitol, tri-(4-methoxy-1-naphthylidene) sorbitol, and dibenzylidene xylitol are efficient nucleators of polypropylene. Trinaphthylidene sorbitol (tns) has two major diastereomers: The “S” diastereomer yields a faster crystallization rate for polypropylene than does the commercial nucleator dibenzylidene sorbitol (Millad 3905). Crystallization rates are 208 and 88, respectively (t min?1 × 1000). The “R” diastereomer, however, is a poor nucleator and interferes with the nucleating activity of the “S” diastereomer. A 52/48 mixture of diastereomers does not nucleate polypropylene, even at twice the concentration. This is first time that the importance of stereochemistry has been demonstrated in the nucleating action. © 1994 John Wiley & Sons, Inc. 相似文献
48.
DD Stapleton TC Moffett DG Baskin JB Bassingthwaighte 《Canadian Metallurgical Quarterly》1995,2(3):277-282
OBJECTIVE: Provide regional flow measurement in the hearts of small mammals using a new, higher-resolution technique based on the deposition of a molecular marker. METHODS: We determined the instantaneous extraction and retention of the "molecular microsphere" radiolabeled desmethylimipramine in retrogradely perfused hamster hearts. In a separate series of experiments, autoradiography was used to measure regional myocardial deposition densities in hamster hearts of about 0.5 g with spatial area resolution of 16 x 16 microns. RESULTS: Radiolabeled desmethylimipramine is almost 100% extracted during a single transcapillary passage and is retained in the tissue for many minutes. Autoradiographic images demonstrated a spatial flow heterogeneity with standard deviations of 31 +/- 4% of the mean flow (N = 5) in 16 x 16 x 20-micronm3 voxels. This is equivalent to the projections made using fractal relationships from cruder observations obtained with microspheres in the hearts of baboons, sheep, and rabbits. CONCLUSIONS: Autoradiography using a molecular deposition marker provides quantitative information on myocardial flow heterogeneities with resolution at the size of cardiac myocytes. Because the regions resolved are smaller than the volume of regions supplied by single arterioles, the results must slightly exaggerate the true heterogeneity of regional flows. 相似文献
49.
Engineering with Computers - This paper is devoted to numerical investigations on mechanical behavior of cracked composite functionally graded (FG) plates. We thus develop an efficient adaptive... 相似文献
50.