全文获取类型
收费全文 | 249172篇 |
免费 | 1672篇 |
国内免费 | 265篇 |
专业分类
电工技术 | 4044篇 |
综合类 | 103篇 |
化学工业 | 40420篇 |
金属工艺 | 15150篇 |
机械仪表 | 10062篇 |
建筑科学 | 4182篇 |
矿业工程 | 3759篇 |
能源动力 | 3878篇 |
轻工业 | 9722篇 |
水利工程 | 4089篇 |
石油天然气 | 13009篇 |
武器工业 | 28篇 |
无线电 | 20187篇 |
一般工业技术 | 62778篇 |
冶金工业 | 32134篇 |
原子能技术 | 11137篇 |
自动化技术 | 16427篇 |
出版年
2021年 | 2781篇 |
2019年 | 2736篇 |
2018年 | 5433篇 |
2017年 | 5715篇 |
2016年 | 6049篇 |
2015年 | 3062篇 |
2014年 | 5332篇 |
2013年 | 10092篇 |
2012年 | 7312篇 |
2011年 | 8942篇 |
2010年 | 7306篇 |
2009年 | 8116篇 |
2008年 | 8180篇 |
2007年 | 7860篇 |
2006年 | 6361篇 |
2005年 | 5563篇 |
2004年 | 5479篇 |
2003年 | 5300篇 |
2002年 | 5134篇 |
2001年 | 4947篇 |
2000年 | 4937篇 |
1999年 | 4253篇 |
1998年 | 7174篇 |
1997年 | 5834篇 |
1996年 | 4421篇 |
1995年 | 3654篇 |
1994年 | 3422篇 |
1993年 | 3623篇 |
1992年 | 3215篇 |
1991年 | 3359篇 |
1990年 | 3481篇 |
1989年 | 3370篇 |
1988年 | 3269篇 |
1987年 | 3260篇 |
1986年 | 3156篇 |
1985年 | 3316篇 |
1984年 | 3252篇 |
1983年 | 3146篇 |
1982年 | 2993篇 |
1981年 | 3045篇 |
1980年 | 3072篇 |
1979年 | 3262篇 |
1978年 | 3490篇 |
1977年 | 3462篇 |
1976年 | 3911篇 |
1975年 | 3209篇 |
1974年 | 3294篇 |
1973年 | 3344篇 |
1972年 | 2987篇 |
1971年 | 2754篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
191.
192.
In recent years the measurement of mold spore concentrations in working environments where workers spend long periods of time has acquired considerable importance because of the diffusion of diseases caused by fungi. On this basis, the aim of the research was to evaluate the level of environmental fungal pollution and contamination by mites in three factories producing seasoned foods, i.e., hams, sausages and cheeses. We also studied the occurrence of fungal species in the upper respiratory tract of workers operating in the washing and brushing areas, which was compared with the environmental concentrations in these areas, where contamination with fungal spores was visibly high. The results showed high and widespread fungal pollution in most of the working environments sampled and a significant presence of the same species in the upper respiratory tract of the workers. The data obtained indicate that the environments sampled can constitute a possible health risk factor for workers. 相似文献
193.
Abstract: This paper describes a system of shallow and deep knowledge acquisition and representation for diagnostic expert systems. The acquisition system is integrated into a diagnostic expert system shell. Shallow knowledge is represented in a failure model as a set of cause-effect relations among the possible faults, while deep knowledge is represented in three deep models: a functional, a deep causal and a taxonomic model. The acquisition and the representation of all the models are fully integrated. The deep knowledge is used by the final expert system in order to provide the user with deep explanations of the cause-effect relations of the failure model. 相似文献
194.
195.
Solute transport processes occur within a wide range of water engineering structures, and urban drainage engineers increasingly rely on modelling tools to represent the transport of dissolved materials. The models take as input representative travel time and dispersion characteristics for key system components, and these generally have to be identified via field or laboratory measurements. Computational Fluid Dynamics (CFD) has the potential to reveal the underlying hydraulic processes that control solute transport, and to provide a generic means of identifying relevant parameter values. This paper reports on a study that has been undertaken to evaluate the feasibility of utilising a CFD-based approach to modelling solute transport. Discrete phase modelling has been adopted, as this is computationally efficient and robust when compared with the time-dependent solution of the advection-dispersion equation. Simulation results are compared with published laboratory data characterising the dispersion effects of surcharged manholes, focusing specifically on an 800 mm diameter laboratory manhole for a flowrate of 0.002 m(3)/s and a range of surcharge depths. Preliminary indications are that the CFD results adequately replicate the measured downstream temporal concentration profiles, and that a threshold surcharge depth, corresponding to a change in hydraulic regime within the manhole, can also be identified. 相似文献
196.
V. A. Matochkin 《Steel in Translation》2007,37(5):445-447
197.
V. A. Kudrin 《Metallurgist》2007,51(11-12):649-651
The most important element of manufacturing processes that employ new metallurgical technologies is improving the quality of the scrap metal used in the given process. Introducing modern scrap-processing equipment is especially important in this regard. At the same time, it is also necessary to use the latest technological advances in order to reduce the oxidation loss of iron during refining in arc steelmaking furnaces. 相似文献
198.
M.V.C. Sastri 《International Journal of Hydrogen Energy》1985,10(2):133
199.
200.
Zinc-containing nanoparticles stable in the liquid phase are synthesized by the radiation chemical reduction of zinc ions
in solutions of inverse micelles. The effects of the absorbed radiation dose and the size of the micelle water pool on the
spectral characteristics of samples are studied. The HPLC and electron microscopy results indicate that the composition of
nanoparticles synthesized depends on the salt nature.
Original Russian Text ? A.A. Revina, E.V. Oksentyuk, A.A. Fenin, 2007, published in Zashchita Metallov, 2007, Vol. 43, No.
6, pp. 613–618. 相似文献