全文获取类型
收费全文 | 33799篇 |
免费 | 2903篇 |
国内免费 | 958篇 |
专业分类
电工技术 | 1253篇 |
综合类 | 1615篇 |
化学工业 | 7062篇 |
金属工艺 | 1128篇 |
机械仪表 | 1380篇 |
建筑科学 | 1871篇 |
矿业工程 | 460篇 |
能源动力 | 801篇 |
轻工业 | 5733篇 |
水利工程 | 598篇 |
石油天然气 | 743篇 |
武器工业 | 136篇 |
无线电 | 2813篇 |
一般工业技术 | 4532篇 |
冶金工业 | 1377篇 |
原子能技术 | 224篇 |
自动化技术 | 5934篇 |
出版年
2024年 | 138篇 |
2023年 | 487篇 |
2022年 | 992篇 |
2021年 | 1390篇 |
2020年 | 1110篇 |
2019年 | 957篇 |
2018年 | 1192篇 |
2017年 | 1284篇 |
2016年 | 1285篇 |
2015年 | 1516篇 |
2014年 | 1998篇 |
2013年 | 2766篇 |
2012年 | 2974篇 |
2011年 | 3000篇 |
2010年 | 2380篇 |
2009年 | 2261篇 |
2008年 | 2196篇 |
2007年 | 2036篇 |
2006年 | 1618篇 |
2005年 | 1201篇 |
2004年 | 878篇 |
2003年 | 678篇 |
2002年 | 586篇 |
2001年 | 387篇 |
2000年 | 324篇 |
1999年 | 251篇 |
1998年 | 249篇 |
1997年 | 212篇 |
1996年 | 163篇 |
1995年 | 138篇 |
1994年 | 126篇 |
1993年 | 106篇 |
1992年 | 78篇 |
1991年 | 58篇 |
1990年 | 50篇 |
1989年 | 48篇 |
1988年 | 44篇 |
1987年 | 37篇 |
1986年 | 37篇 |
1985年 | 50篇 |
1984年 | 40篇 |
1983年 | 27篇 |
1982年 | 28篇 |
1981年 | 39篇 |
1980年 | 23篇 |
1979年 | 31篇 |
1978年 | 18篇 |
1977年 | 15篇 |
1976年 | 23篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Post-treatment of an UASB reactor effluent, fed with domestic sewage, was conducted using two-stage flotation and UV disinfection. Results were compared to those obtained in a parallel stabilisation pond. The first flotation stage employed 5 - 7.5 mg L(-1) cationic flocculant to separate off more than 99% of the suspended solids. Then, phosphate ions were completely recovered using carrier flotation with 5-25 mg L(-1) of Fe (FeCl3) at pH 6.3-7.0. This staged flotation led to high recoveries of water and allowed us to separate organic matter and phosphate bearing sludge. The water still contained about 1 x 10(2) NMP/100 mL total coliforms, which were removed using UV radiation to below detection levels. Final water turbidity was < 1.0 NTU, COD < 20 mg L(-1) O2 and 71 mNm(-1), the liquid/air interfacial tension. This flotation-UV flowsheet was found to be more efficient than the treatment in the stabilisation pond and appears to have some potential for water reuse. Results were discussed in terms of the biological, chemical and physicochemical mechanisms involved. 相似文献
42.
Rui A. S. Lapa José L. F. C. Lima 《Journal of Automated Methods and Management in Chemistry》1991,13(3):119-122
The construction of a microcomputer-controlled electrode switch for
use in potentiometric determinations is described. This can be coupled to most of the analytical equipment usually found in laboratories, to enable a setting up of automatic systems capable of performing sequential determinations with several ion-selective
electrodes. The assessment of its analytical usage and behaviour are discussed. 相似文献
43.
Juan Manuel Mendez Stephen Muhl G. Contreras-Puente J. Aguilar-Hernandez 《Thin solid films》1992,220(1-2):125-131
Carbon films have been produced using a graphite hollow cathode and an r.f. plasma of hydrogen or hydrogen and argon. No hydrocarbon gas was used. The films were subjected to heat treatments up to 700 °C in air. The optical properties of the films were studied using Fourier transform IR, UV-visible, Raman, ellipsometry and photoluminescence techniques before and after the annealing. Films prepared without argon have a narrower band gap and a different photoluminescence response from films prepared with argon. The index of refraction was seen to have values between 1.7 and 2.2 depending on the preparation conditions. The optical band gap of the films was generally greater than 2 eV and the annealing process both increased the gap and reduced the density of states responsible for the large photoluminescence signal. 相似文献
44.
André Girard Pierre Dominique Lansard Bernard Liau Anne Marie Mongeon Jean Luc Thibault 《电信纪事》1991,46(5-6):335-350
Classical hierarchical routing in telephone networks is extended to a wider class called out-of-chain routing in such a way that some useful properties of hierarchical routing are retained. This new routing pattern offers more potential paths than the fixed hierarchical one and can be introduced as a dynamic routing where the fixed alternate sequences change at some predetermined instants during the day. The effect of this new routing pattern on the network performances is examined. The main topic of this paper is to present heuristic methods used to optimise such routings in large networks. We show on artificial networks that the throughput of a given network can be significantly improved by suitable routing choices. We demonstrate that the integration of routing changes within a multihour dimensioning process is possible but the lack of realistic data does not permit at this time to quantify the value of routing optimization on real networks. 相似文献
45.
The composition of yellow bronze coatings deposited from acidic sulfate solutions added with polyether laprol and the electrodeposition
conditions are studied by voltammetry and XPS. It is found that halides in rather low (micromolar) concentrations affect significantly
the partial electrodeposition processes. Chlorides increases cathodic polarization, widen the current window of the yellow
bronze electrodeposition, and favor the increase in tin content of the coatings. Bromides narrow the current window, lower
the tin content in the coatings, and hinder the yellow bronze surface oxidation. Iodides inhibit the copper electroreduction
markedly, which makes the yellow bronze deposition practically impossible.
Original Russian Text ? Z. Mockus, S. Kanapeckaité, V. Jasulaitiené, A. Survila, 2006, published in Zashchita Metallov, 2006,
Vol. 42, No. 5, pp. 526–531. 相似文献
46.
47.
Patrícia Carvalho de Souza André Salim Khayat Igor Chamon Seligmann Rommel Mario Rodríguez Burbano 《Biocell》2008,32(2):207-210
The collared peccary (Tayassu tajacu) is widely distributed over the American continent, being found from the south of the USA to the north of Argentina. In Brazil, it is spread all over the country, being one of the potential species to be raised in captivity. Therefore, the cytogenetic techniques could be a potential tool for reproductive monitoring of animals raised in captivity, mainly when destined for commercial purposes. This study had the objective of determining the chromosome number of two populations raised in captivity and characterizing them by GTG banding. For this purpose, an analysis was made of mitotic metaphases obtained from lymphocyte cultures made from blood samples of 11 animals, six of which from the Northeast and five from the North of Brazil. The results of this analysis showed the same karyotype pattern for the species (2n=30 chromosomes and NF=48), besides corresponding to the South American pattern of the species, i.e., without a translocation between autosomes 1 and 8, chromosome X acrocentric, and no differences were found between the two populations studied. However, chromosomal polymorphisms were observed compared to data from the literature on populations from North and South America. 相似文献
48.
为了继承和发扬错金工艺,从其定义出发,探讨了该工艺在中国古代及国外的发展与应用以及笔者对该工艺的实验研究。针对在错金工艺实践过程中出现的问题,在查阅了相关的资料后,对传统错金工艺的实现方法提出了质疑。 相似文献
49.
Baudilio Coto Carmen Martos Jos L. Pea Juan J. Espada María D. Robustillo 《Fuel》2008,87(10-11):2090-2094
Wax precipitation is one of the most important flow assurance problems. Unfortunately, experimental data are very scarce to confirm existing models for prediction of such precipitation problem. This work reports a new experimental method. Multistage fractional wax precipitation was carried out by decreasing the temperature of crude oil. No solvent dilution was used, so the effect of solvent on temperature wax precipitation was avoided. The reproducibility of the method was tested with comparable results. The precipitation curve and the wax appearance temperature were obtained for two crude oils with different chemical nature using the reported method. 相似文献
50.
An optical nondestructive strain measurement technique was performed to analyze the mechanical deformation induced by an electrical field within the insulating materials. Poly(ethylene naphthalene 2,6‐dicarboxylate) (PEN) films were then subjected to constant electrical fields right up to their electrical breakdown. The experimental technique made it possible to follow the various stages of the mechanical behavior of PEN in real time. The final breakdown occurred in the observation zone and the related mechanical deformation was captured. A “margarita” structure was observed with a hole at the center. The experimental results indicated that the level of the induced‐mechanical deformations depended on the local environment. We defined two different zones representing the inside and the outside of the damaged area. The induced‐deformations were larger in the damaged zone. It was also observed that deformations increased when the sample had a lower degree of crystallinity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献