全文获取类型

收费全文 |
15350篇 |

免费 |
1835篇 |

国内免费 |
1394篇 |

专业分类

电工技术 |
1254篇 |

综合类 |
1905篇 |

化学工业 |
1245篇 |

金属工艺 |
957篇 |

机械仪表 |
1161篇 |

建筑科学 |
1267篇 |

矿业工程 |
620篇 |

能源动力 |
531篇 |

轻工业 |
1012篇 |

水利工程 |
1018篇 |

石油天然气 |
626篇 |

武器工业 |
188篇 |

无线电 |
1217篇 |

一般工业技术 |
1247篇 |

冶金工业 |
575篇 |

原子能技术 |
84篇 |

自动化技术 |
3672篇 |

出版年

2024年 |
130篇 |

2023年 |
434篇 |

2022年 |
566篇 |

2021年 |
687篇 |

2020年 |
688篇 |

2019年 |
511篇 |

2018年 |
429篇 |

2017年 |
480篇 |

2016年 |
485篇 |

2015年 |
569篇 |

2014年 |
801篇 |

2013年 |
924篇 |

2012年 |
1017篇 |

2011年 |
1025篇 |

2010年 |
808篇 |

2009年 |
854篇 |

2008年 |
795篇 |

2007年 |
1035篇 |

2006年 |
1038篇 |

2005年 |
853篇 |

2004年 |
757篇 |

2003年 |
620篇 |

2002年 |
502篇 |

2001年 |
520篇 |

2000年 |
401篇 |

1999年 |
350篇 |

1998年 |
265篇 |

1997年 |
183篇 |

1996年 |
187篇 |

1995年 |
141篇 |

1994年 |
127篇 |

1993年 |
85篇 |

1992年 |
61篇 |

1991年 |
47篇 |

1990年 |
47篇 |

1989年 |
33篇 |

1988年 |
40篇 |

1987年 |
25篇 |

1986年 |
13篇 |

1985年 |
8篇 |

1984年 |
8篇 |

1983年 |
5篇 |

1981年 |
2篇 |

1980年 |
6篇 |

1979年 |
3篇 |

1977年 |
2篇 |

1975年 |
2篇 |

1964年 |
2篇 |

1960年 |
2篇 |

1959年 |
2篇 |

**排序方式：**共有10000条查询结果，搜索用时 15 毫秒

1.

镀锌测厚仪

**总被引：2，自引：0，他引：2** 安福林 《核电子学与探测技术》1997,17(4):288-291

本文叙述了Ｘ射线荧光测厚仪的原理、特点及测量头的设计考虑原则。并以我们研制的两种镀锌测得仪为例作了详细说明。 相似文献

2.

Chongbin Zhao Tianyun Liu 《International journal for numerical methods in engineering》2003,58(10):1435-1456

This paper presents an exact non‐reflecting boundary condition for dealing with transient scalar wave propagation problems in a two‐dimensional infinite homogeneous layer. In order to model the complicated geometry and material properties in the near field, two vertical artificial boundaries are considered in the infinite layer so as to truncate the infinite domain into a finite domain. This treatment requires the appropriate boundary conditions, which are often referred to as the artificial boundary conditions, to be applied on the truncated boundaries. Since the infinite extension direction is different for these two truncated vertical boundaries, namely one extends toward x →∞ and another extends toward x→‐ ∞, the non‐reflecting boundary condition needs to be derived on these two boundaries. Applying the variable separation method to the wave equation results in a reduction in spatial variables by one. The reduced wave equation, which is a time‐dependent partial differential equation with only one spatial variable, can be further changed into a linear first‐order ordinary differential equation by using both the operator splitting method and the modal radiation function concept simultaneously. As a result, the non‐reflecting artificial boundary condition can be obtained by solving the ordinary differential equation whose stability is ensured. Some numerical examples have demonstrated that the non‐reflecting boundary condition is of high accuracy in dealing with scalar wave propagation problems in infinite and semi‐infinite media. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献

3.

Christine Di Massimo Paul A. Lant Aidan Saunders Gary A. Montague Ming T. Tham A. Julian Morris 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,53(3):265-277

The last decade has seen the development of a number of approaches for estimating those variables which are difficult to measure on-line in industrial process situations. Whilst a range of techniques is available, a common element is the use of process knowledge in the form of a system model. In the case of bioprocess systems, although a large range of models has been presented in the literature, their use in estimation schemes on an industrial scale has been limited. A number of reasons can be identified for their low level of utilisation. Of particular significance is the uncertainty which exists in quantifying system performance and the process-model mismatch which inevitably results. The level of ‘pre-defined model’ uncertainty, together with the knowledge gained during the course of the fermentation, serves to dictate estimator structure. The paper considers a range of estimation strategies and contrasts, through industrial applications, their performance characteristics and utility. 相似文献

4.

Dental amalgams are based on a broad spectrum of materials differing in their chemical composition, metallurgical treatment, and in the way the initial alloys powders are prepared. In addition to their chemical composition, amalgams based on various powders differ in both their microstructure and the amount of mercury needed for preparation. All these facts may affect electrochemical processes occurring during their interaction with oral fluids, and also mercury release. While verifying the effect of the technology used for the preparation of the high‐copper ternary alloy powder on the properties of resulting amalgams, this study aimed at the mechanism of their interaction with a model saliva solution as well as mercury release was included. Measurements were done in a model saliva solution using standard electrochemical methods and exposition measurements. The interaction of individual types of amalgams with artificial saliva did not reveal any significant differences. The free corrosion potential of all these amalgams in an aerated solution settled in the range of values in which tin oxidation, resulting in a layer of insoluble corrosion producsts, turned out to be the dominant anodic process. The rate of mercury release was the lowest for amalgams based on a gas‐atomized alloy. The highest rate of mercury release, and also its dependence on time, was exhibited by lathe‐cut powder based amalgam. In addition to different volume fraction of the Ag‐Hg phase and the level of its tin alloying, this different behaviour may be explained by differences in the rate at which a layer of tin corrosion products acting as a barrier to mercury release is formed. 相似文献

5.

Kum‐Il Lee Yong‐Sik Yim Sang‐Wook Chung Jiaqiu Wei Jong Il Rhee 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(9):1036-1045

A two‐dimensional (2D) spectrofluorometer was used to monitor various fermentation processes with recombinant

*E coli*for the production of 5‐aminolevulinic acid (ALA). The whole fluorescence spectral data obtained during a process were analyzed using artificial neural networks, ie self‐organizing map (SOM) and feedforward backpropagation neural network (BPNN). The SOM‐based classification of the whole spectral data has made it possible to qualitatively associate some process parameters with the normalized weights and variances, and to select some useful combinations of excitation and emission wavelengths. Based on the classified fluorescence spectra a supervised BPNN algorithm was used to predict some of the process parameters. It was also shown that the BPNN models could elucidate some sections of the process's performance, eg forecasting the process's performance. Copyright © 2005 Society of Chemical Industry 相似文献6.

Emilio Marengo Valentina Longo Elisa Robotti Marco Bobba Fabio Gosetti Orfeo Zerbinati Silvana Di Martino 《应用聚合物科学杂志》2008,109(6):3975-3982

Principal component regression (PCR), partial least squares (PLS), StepWise ordinary least squares regression (OLS), and back‐propagation artificial neural network (BP‐ANN) are applied here for the determination of the propylene concentration of a set of 83 production samples of ethylene–propylene copolymers from their infrared spectra. The set of available samples was split into (a) a training set, for models calculation; (b) a test set, for selecting the correct number of latent variables in PCR and PLS and the end point of the training phase of BP‐ANN; (c) a production set, for evaluating the predictive ability of the models. The predictive ability of the models is thus evaluated by genuine predictions. The model obtained by StepWise OLS turned out to be the best one, both in fitting and prediction. The study of the breakdown number of samples to be included in the training set showed that at least 52 experiments are necessary to build a reliable and predictive calibration model. It can be concluded that FTIR spectroscopy and OLS can be properly employed for monitoring the synthesis or the final product of ethylene–propylene copolymers, by predicting the concentration of propylene directly along the process line. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献

7.

Scaffold‐guided tissue engineering based on synthetic and natural occurring polymers has gained many interests in recent year. In this study, the development of a chitosan‐heparin artificial extracellular matrix (AECM) is reported. Three‐dimensional, macroporous composite AECMs composed of heparin (Hep) and chitosan (Chito) were prepared by an interpolyelectrolyte complex/lyophilization method. The Chito‐Hep composite AECMs were, respectively, crosslinked with glutaraldehyde, as well as cocrosslinked with

*N,N*‐(3‐dimethylaminopropyl)‐*N*′‐ethyl carbodiimide (EDC/NHS) and*N*‐hydroxysuccinimide (NHS). The crosslinking reactions were examined by FT‐IR analysis. In physiological buffer solution (PBS), the EDC/NHS‐crosslinked Chito‐Hep composite AECM showed a relative lower water retention ratio than its glutaraldehyde‐crosslinked counterparts. The EDC/NHS‐crosslinked Chito‐Hep composite AECMs showed excellent biocompatibility, according to the results of the*in vitro*cytotoxic test. This result suggested that the EDC/NHS‐crosslinked Chito‐Hep composite AECMs might be a potential biomaterial for scaffold‐guided tissue engineering applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献8.

9.

10.