全文获取类型
收费全文 | 48084篇 |
免费 | 2320篇 |
国内免费 | 66篇 |
专业分类
电工技术 | 328篇 |
综合类 | 37篇 |
化学工业 | 11047篇 |
金属工艺 | 899篇 |
机械仪表 | 936篇 |
建筑科学 | 1516篇 |
矿业工程 | 88篇 |
能源动力 | 1503篇 |
轻工业 | 8923篇 |
水利工程 | 461篇 |
石油天然气 | 217篇 |
武器工业 | 3篇 |
无线电 | 2063篇 |
一般工业技术 | 7262篇 |
冶金工业 | 8449篇 |
原子能技术 | 259篇 |
自动化技术 | 6479篇 |
出版年
2024年 | 90篇 |
2023年 | 423篇 |
2022年 | 929篇 |
2021年 | 1441篇 |
2020年 | 1028篇 |
2019年 | 1176篇 |
2018年 | 1666篇 |
2017年 | 1668篇 |
2016年 | 1824篇 |
2015年 | 1415篇 |
2014年 | 1794篇 |
2013年 | 3540篇 |
2012年 | 2786篇 |
2011年 | 3095篇 |
2010年 | 2385篇 |
2009年 | 2249篇 |
2008年 | 2107篇 |
2007年 | 1894篇 |
2006年 | 1444篇 |
2005年 | 1249篇 |
2004年 | 1144篇 |
2003年 | 1045篇 |
2002年 | 934篇 |
2001年 | 674篇 |
2000年 | 633篇 |
1999年 | 709篇 |
1998年 | 2938篇 |
1997年 | 1906篇 |
1996年 | 1281篇 |
1995年 | 739篇 |
1994年 | 602篇 |
1993年 | 612篇 |
1992年 | 214篇 |
1991年 | 206篇 |
1990年 | 160篇 |
1989年 | 174篇 |
1988年 | 181篇 |
1987年 | 171篇 |
1986年 | 126篇 |
1985年 | 175篇 |
1984年 | 134篇 |
1983年 | 99篇 |
1982年 | 101篇 |
1981年 | 121篇 |
1980年 | 121篇 |
1978年 | 64篇 |
1977年 | 201篇 |
1976年 | 381篇 |
1975年 | 60篇 |
1973年 | 72篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
J Comas I Rodríguez-Roda M Poch K V Gernaey C Rosen U Jeppsson 《Water science and technology》2006,53(4-5):303-311
Wastewater treatment plant operators encounter complex operational problems related to the activated sludge process and usually respond to these by applying their own intuition and by taking advantage of what they have learnt from past experiences of similar problems. However, previous process experiences are not easy to integrate in numerical control, and new tools must be developed to enable re-use of plant operating experience. The aim of this paper is to investigate the usefulness of a case-based reasoning (CBR) approach to apply learning and re-use of knowledge gained during past incidents to confront actual complex problems through the IWA/COST Benchmark protocol. A case study shows that the proposed CBR system achieves a significant improvement of the benchmark plant performance when facing a high-flow event disturbance. 相似文献
2.
The tensile elastic modulus (E), yield stress (σY) and microhardness (MH) of neat and binary and ternary blends of glassy semicrystalline ethylene–vinyl alcohol copolymer (EVOH), a glassy amorphous polyamide and a semicrystalline nylon‐containing ionomer covering a broad range of properties were examined. The tests were carried out on dry and water‐equilibrated samples to produce stiffer and softer materials, respectively. From the results, more accurate linear correlations were found to describe adequately the microhardness, modulus and yield stress of these strongly self‐associated polymers through hydrogen bonding. Copyright © 2003 Society of Chemical Industry 相似文献
3.
Javier Ramírez Antonio García Uwe Meyer-Bäse Fred Taylor Antonio Lloris 《The Journal of VLSI Signal Processing》2003,33(1-2):171-190
Currently there are design barriers inhibiting the implementation of high-precision digital signal processing (DSP) objects with field programmable logic (FPL) devices. This paper explores overcoming these barriers by fusing together the popular distributed arithmetic (DA) method with the residue number system (RNS) for use in FPL-centric designs. The new design paradigm is studied in the context of a high-performance filter bank and a discrete wavelet transform (DWT). The proposed design paradigm is facilitated by a new RNS accumulator structure based on a carry save adder (CSA). The reported methodology also introduces a polyphase filter structure that results in a reduced look-up table (LUT) budget. The 2C-DA and RNS-DA are compared, in the context of a FPL implementation strategy, using a discrete wavelet transform (DWT) filter bank as a common design theme. The results show that the RNS-DA, compared to a traditional 2C-DA design, enjoys a performance advantage that increases with precision (wordlength). 相似文献
4.
孙维銮 《自动化与仪器仪表》1994,(3):31-34,38
从理论上和实践上对武钢1700、鞍钢1700改造前后、本钢1700改造前后和攀钢1450精轧机组的电动压下机构在带钢压下时的动特性进行计算和探讨,得出有说服力的结论。主题词: 相似文献
5.
6.
7.
There are some foods that contain mutagenic or carcinogenic agents, some of which occur naturally and others that may be formed during preparation or cooking. Several foods such as legumes, also contain natural antimutagens and/or anticarcinogens. Lupine is one such legume that contains high amounts of protein (40%) and oils (14%). About 90 species of lupine have been reported throughout Mexico. However, the use of this crop as a source of food has been limited by the presence of antinutritional agents such as phenolic compounds (PC), carbohydrates (CH) and quinolizidinic alkaloids (Qas). It has also been suggested that consuming these compounds can affect human health and may even reduce the risk of disease. The objective of this work was to determine the effect of PC, CH and Qas, isolated and quantified from Lupinus campestris on the mutagenicity of 1-nitropyrene (1-NP) as a model mutagen and we used the Salmonella typhimurium tester strain YG1024 by the Kado microsuspension method. The results indicate that L. campestris seeds have 11 mg (+)catechin equivalent g(-1) seed coat; 120.3 mg g(-1) seeds and 2.13 mg g(-1) seeds of PC, CH and Qas, respectively. 1-NP mutagenicity was inhibited by 86% for PC, 76% for CH and 75% for Qas at concentrations of 200, 512 and 13.6 microg/tube, respectively. 相似文献
8.
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
9.
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
10.
F Javier Benítez Ana I Leal Francisco J Real Juan L Acero Gloria Roldán 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(3):309-316
BACKGROUND: The first stage of the cork industrial process generates great volumes of wastewater with moderate to high organic pollutant content that must be purified using different procedures, such as filtration by membranes. RESULTS: The tangential filtration of these wastewaters was studied using two different laboratory equipments. In the first one, three ultrafiltration (UF) membranes were tested, with molecular weight cut‐off (MWCO) 100 kDa and 30 kDa, and two operating modes were used: total recycling of permeate and retentate streams, and in continuous mode, without recycling both streams. In the total recycling UF experiments, the influence of the operating variables on the permeate flux was first established. The effectiveness of the different membranes was determined by evaluating the rejection coefficients for several parameters that measure the global pollutant content of the effluent. The values found for these rejection coefficients were in the following order: ellagic acid and color > absorbance at 254 nm > tannic content > COD (chemical oxygen demand). In the continuous mode experiments, the fouling mechanism for each membrane was established by fitting the experimental data to various filtration fouling models given in the literature. The operating mode in the second equipment was batch concentration, and additional experiments were carried out with an UF membrane (2 kDa), and with a NF membrane (with MWCO in the range 150–300 Da). CONCLUSIONS: The three operating modes tested provided different rejection levels of organic matter; among them, the most effective procedure tested was batch concentration mode using a NF membrane. Copyright © 2007 Society of Chemical Industry 相似文献