全文获取类型
收费全文 | 199832篇 |
免费 | 2309篇 |
国内免费 | 614篇 |
专业分类
电工技术 | 3468篇 |
综合类 | 149篇 |
化学工业 | 28971篇 |
金属工艺 | 8052篇 |
机械仪表 | 6069篇 |
建筑科学 | 4812篇 |
矿业工程 | 1303篇 |
能源动力 | 5127篇 |
轻工业 | 17118篇 |
水利工程 | 2302篇 |
石油天然气 | 4041篇 |
武器工业 | 8篇 |
无线电 | 23070篇 |
一般工业技术 | 40025篇 |
冶金工业 | 37334篇 |
原子能技术 | 5086篇 |
自动化技术 | 15820篇 |
出版年
2021年 | 1607篇 |
2019年 | 1568篇 |
2018年 | 2576篇 |
2017年 | 2647篇 |
2016年 | 2775篇 |
2015年 | 1795篇 |
2014年 | 3076篇 |
2013年 | 8942篇 |
2012年 | 5051篇 |
2011年 | 7027篇 |
2010年 | 5590篇 |
2009年 | 6350篇 |
2008年 | 6444篇 |
2007年 | 6515篇 |
2006年 | 5581篇 |
2005年 | 5231篇 |
2004年 | 5006篇 |
2003年 | 4888篇 |
2002年 | 4529篇 |
2001年 | 4658篇 |
2000年 | 4581篇 |
1999年 | 4732篇 |
1998年 | 11401篇 |
1997年 | 8132篇 |
1996年 | 6412篇 |
1995年 | 4677篇 |
1994年 | 4280篇 |
1993年 | 4077篇 |
1992年 | 3224篇 |
1991年 | 3076篇 |
1990年 | 2873篇 |
1989年 | 2953篇 |
1988年 | 2826篇 |
1987年 | 2403篇 |
1986年 | 2312篇 |
1985年 | 2718篇 |
1984年 | 2511篇 |
1983年 | 2347篇 |
1982年 | 2092篇 |
1981年 | 2206篇 |
1980年 | 2029篇 |
1979年 | 2129篇 |
1978年 | 2123篇 |
1977年 | 2371篇 |
1976年 | 3190篇 |
1975年 | 1834篇 |
1974年 | 1763篇 |
1973年 | 1773篇 |
1972年 | 1444篇 |
1971年 | 1339篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Wastewater discharge from coal refining plants contains a number of biologically toxic compounds; 2000-2500 mg/l of COD of which 40% is composed of phenol, 100-400 mg/l of thiocyanate, 10-40 mg/l of cyanide, 100-250 mg/l of NH4+-N and 150-300 mg/l of total nitrogen. In order to treat this kind of high strength wastewater, we have developed a high performance biofilm process using fluidizing bio-carriers of the tube chip type. The fluidizing biofilm carriers are made of a composite of polyethylene and several inorganic materials, whose density is controlled at 0.97-0.98 g/ml. The fluidizing biofilm carriers show sound fluidization characteristics inside bioreactors. The wastewater is treated using three consecutive series reactors in oxic-anoxic-oxic arrangement. Each reactor is charged with the fluidizing biofilm carriers of 50 vol%. Furthermore, newly cultured active microorganisms for the thiocyanate biodegradation are added in the biofilm process. At total hydraulic retention time of 2.2 days, this process can achieve steady state removal efficiencies: COD, 99%; thiocyanate, 99%; NH4+-N, 99% and total nitrogen, 90%. 相似文献
62.
O Bernard B Chachuat A Hélias B Le Dantec B Sialve J-P Steyer L Lardon P Neveu S Lambert J Gallop M Dixon P Ratini A Quintabà S Frattesi J M Lema E Roca G Ruiz J Rodriguez A Franco P Vanrolleghem U Zaher D J W De Pauw K De Neve K Lievens D Dochaine O Schoefs H Fibrianto R Farina V Alcaraz Gonzalez V Gonzalez Alvarez P Lemaire J A Martinez F Esandi O Duclaud J F Lavigne 《Water science and technology》2005,52(1-2):457-464
The TELEMAC project brings new methodologies from the Information and Science Technologies field to the world of water treatment. TELEMAC offers an advanced remote management system which adapts to most of the anaerobic wastewater treatment plants that do not benefit from a local expert in wastewater treatment. The TELEMAC system takes advantage of new sensors to better monitor the process dynamics and to run automatic controllers that stabilise the treatment plant, meet the depollution requirements and provide a biogas quality suitable for cogeneration. If the automatic system detects a failure which cannot be solved automatically or locally by a technician, then an expert from the TELEMAC Control Centre is contacted via the internet and manages the problem. 相似文献
63.
J Byrne S Kienzle D Johnson G Duke V Gannon B Selinger J Thomas 《Water science and technology》2006,53(10):327-334
Long-term trends in alpine and prairie snow pack accumulation and melt are affecting streamflow within the Oldman River Basin in southern Alberta, Canada. Unchecked rural and urban development also has contributed to changes in water quality, including enhanced microbial populations and increased waterborne pathogen occurrence. In this study we look at changing environment within the Oldman River Basin and its impact on water quality and quantity. The cumulative effects include a decline in net water supplies, and declining quality resulting in increased risk of disease. Our data indicates that decreases in the rate of flow of water can result in sedimentation of bacterial contaminants within the water column. Water for ecosystems, urban consumption, recreation and distribution through irrigation is often drawn from waterholding facilities such as dams and weirs, and concern must be expressed over the potential for contaminate build-up and disproportionate potential of these structures to pose a risk to human and animal health. With disruption of natural flow rates for water resulting from environmental change such as global warming and/or human intervention, increased attention needs to be paid to use of best management practices to protect source water supplies. 相似文献
64.
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
65.
Filled fibrous sorbents modified with transition metal ferro- and ferricyanides capable to recover americium(III) and rare-earth metals(III) from nitric acid solutions were prepared. The most complete and rapid recovery is attained on complex-forming and cation-exchange sorbents (as filled fibrous materials) saturated with nickel ions. The sorbents are characterized by good kinetic properties and can be used for recovery of the above metals. 相似文献
66.
The discrimination problem for two normal populations with the same covariance matrix when additional information on the population is available is considered. A study of the robustness properties against training sample contamination of classification rules that incorporate this additional information is performed. These rules have received recently attention where their total misclassification probability (TMP) is proved to be lower than Fisher's linear discriminant rule. The results of a simulation study on the TMP which compares the behaviour of the new rules against Fisher's rule and some of its robustified versions under different types of contamination are presented. These results show that the rules that incorporate the additional information not only have lower TMP, but they also prevent against some types of contamination. In order to achieve prevention from all types of contamination a robustifed version of these rules is recommended. 相似文献
67.
During experiments on the MSL-1 (first microgravity science laboratory) mission of the space shuttle (STS-83 and STS-94, April
and July 1997), a droplet of palladium-silicon alloy was electromagnetically levitated for viscosity measurements. For the
nondeforming droplet, the resultant magnetohydrodynamic (MHD) flow inside the drop can be inferred from motion of impurity
particulates on the surface. In the experiments, subsequent to melting, Joule heating produces a continuous reduction of viscosity
of the fluid resulting in an acceleration of the flow with time. These observations indicate formation of a pair of co-rotating
toroidal flow structures inside the spheroidal drop that undergo flow instabilities. As the fluid temperature rises, the amplitude
of the secondary flow increases, and beyond a point, the tracers exhibit noncoherent chaotic motion signifying emergence of
turbulence inside the drop. Assuming that the observed laminar-turbulent transition is shear-layer type, the internal structure
of the toroidal loops is used to develop a semiempirical correlation for the onset of turbulence. Our calculations indicate
that the suggested correlation is in modest agreement with the experimental data, with the transition occurring at a Reynolds
number of 600. 相似文献
68.
Bestehen ausreichende Anhaltspunkte für die Hochwassergef?hrdung, ist die Gemeinde verpflichtet, sich durch Nachforschungen
Gewissheit über das Vorliegen oder Nichtvorliegen eines Hochwasserabflussgebietes gem § 38 Abs 3 WRG zu verschaffen. Liegt
ein solches vor, hat sie gem § 12 Abs 1 Z 2 krnt GplG dieses im Fl?chenwidmungsplan ersichtlich zu machen. Erteilt die Gemeinde
eine Baubewilligung ohne diese von der Erteilung einer wasserrechtlichen Bewilligung abh?ngig zu machen, haftet sie für die
Kosten der Bauführung, die bei gesetzes-konformer Vorgangsweise unterlassen worden w?re. 相似文献
69.
Undergraduate software engineering education is now well established in many countries, and many of these degree programs have received formal accreditation by the relevant country's professional body for computing. SE 2004 represents an enormous effort by numerous individuals across the discipline. Its quality has been clearly recognized by the sponsoring organizations. The developmental team confidently looks forward to the volume's use and to your participation in future evaluations and in the next phase of development. The volume provides usable results for those in emerging economies who wish to enter the software engineering community, and we know that individual project members and the participating national bodies are ready to assist. 相似文献
70.
A. B. Blyakhman A. V. Myakinkov A. G. Ryndyk 《Journal of Communications Technology and Electronics》2006,51(4):397-402
The maximum-likelihood technique is applied to determine the coordinates of moving targets in a three-dimensional bistatic forward-scattering radar. The potential accuracy of the coordinates’ determination is estimated. Simulation results are presented. 相似文献