全文获取类型
收费全文 | 2685篇 |
免费 | 145篇 |
专业分类
电工技术 | 22篇 |
综合类 | 1篇 |
化学工业 | 753篇 |
金属工艺 | 59篇 |
机械仪表 | 92篇 |
建筑科学 | 86篇 |
矿业工程 | 7篇 |
能源动力 | 102篇 |
轻工业 | 705篇 |
水利工程 | 20篇 |
石油天然气 | 17篇 |
无线电 | 114篇 |
一般工业技术 | 354篇 |
冶金工业 | 231篇 |
原子能技术 | 16篇 |
自动化技术 | 251篇 |
出版年
2024年 | 9篇 |
2023年 | 20篇 |
2022年 | 137篇 |
2021年 | 133篇 |
2020年 | 74篇 |
2019年 | 77篇 |
2018年 | 83篇 |
2017年 | 116篇 |
2016年 | 88篇 |
2015年 | 76篇 |
2014年 | 103篇 |
2013年 | 217篇 |
2012年 | 198篇 |
2011年 | 187篇 |
2010年 | 151篇 |
2009年 | 131篇 |
2008年 | 130篇 |
2007年 | 122篇 |
2006年 | 90篇 |
2005年 | 68篇 |
2004年 | 61篇 |
2003年 | 57篇 |
2002年 | 43篇 |
2001年 | 39篇 |
2000年 | 25篇 |
1999年 | 20篇 |
1998年 | 84篇 |
1997年 | 42篇 |
1996年 | 39篇 |
1995年 | 34篇 |
1994年 | 23篇 |
1993年 | 23篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 14篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1977年 | 3篇 |
1976年 | 10篇 |
1975年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有2830条查询结果,搜索用时 15 毫秒
11.
Several polyimide resins were tested as possible scratch resistant coatings for aluminosilicate glass centrifuge tubes. Tubes with siloxane pretreatments provided the best adhesion between the polyimide and glass surface. Resins synthesized with an alkoxysilane group incorporated into the polyimide chain also showed improved adhesion, but the results were not as significant as when the pretreatment was used. Elastic recovery and effective Young's modulus of the polyimide coatings were calculated from nano-scratching. The results indicate that polyimides with a lower modulus, and higher elastic recovery, protected the glass surface best, exhibiting compression of the coating layer. An example was poly-4-4'-oxydiphenylene pyromellitimide (PMDA-ODA), whereas the coatings with a high effective Young's modulus and low elastic recovery ruptured. An example of a failed coating was poly-4,4'-carbonyldiphenylene 3,3',4,4'-biphenylenetetracarboximide (BPDA-DABP) which had low amount of elastic recovery, high effective Young's modulus and a large amount of flaking during macroscratch testing. 相似文献
12.
M J Gatti M E Fraga C Magnoli A M Dalcero C A da Rocha Rosa 《Food Additives & Contaminants》2003,20(12):1120-1126
A mycological survey was carried out on 115 samples of whole dried black pepper seeds, from two main production regions of Brazil (Pará and Espírito Santo). A high incidence of contamination was verified in both regions when 99.1% of the samples showed filamentous fungi contamination. A total of 497 species of nine different genera were isolated (Aspergillus, Eurotium, Rhizopus, Penicillium, Curvularia, Cladosporium, Absidia, Emericella and Paecilomyces). The genus Aspergillus was the predominant (53.5%) followed by species from the Eurotium genus (24.5%). Eurotium chevalieri (16.4%) was the most predominant species followed by A. flavus (14.6%) present on 55 samples of black pepper (47.8%) analysed. Twenty-five samples (21.7%) were contaminated with aflatoxigenic strains of A. flavus and A. parasiticus. In relation to the types of aflatoxins produced by mycotoxigenic strains, it was observed that 25 strains (44.6%) of 56 isolated of A. flavus produced aflatoxins. From 12 samples, A. ochraceus species were isolated in low frequency (3.5%). Two strains of A. ochraceus from 16 isolated were producers of ochratoxin A. With respect to the aflatoxins and ochratoxin A natural contamination, none of the samples presented detectable levels of these mycotoxins using thin-layer chromatographic analysis. 相似文献
13.
Raquel Alves dos Santos Teresinha Rosa Cabral Isabel Rosa Cabral Lusania Maria Greggi Antunes Cristiane Pontes Andrade Plínio Cerqueira dos Santos Cardoso Marcelo de Oliveira Bahia Claudia Pessoa José Luis Martins do Nascimento Rommel Rodríguez Burbano Catarina Satie Takahashi 《Biocell》2008,32(2):195-200
Physalis angulata L (Solanaceae) is a medicinal plant from North of Brazil, whose different extracts and infusions are commonly used in the popular medicine for the treatment of malaria, asthma, hepatitis, dermatitis and rheumatism. However, the genotoxic effects of P. angulata on human cells is not well known. The main purpose of the present study was to evaluate the in vitro genotoxic effects of aqueous extract of P. angulata using the comet assay and the micronucleus assay in human lymphocytes provided from 6 healthy donors. Treatments with P. angulata extracts were performed in vitro in order to access the extent of DNA damage. The comet assay has shown that treatments with P. angulata at 0.5, 1.0, 2.0, 3.0 and 6.0 microg/mL in culture medium were genotoxic. Lymphocytes treated with P. angulata at the concentrations of 3.0 and 6.0 microg/mL in culture medium showed a statistically significant increase in the frequency of micronucleus (p<0.05), however, the cytokinesis blocked proliferation index (CBPI) was not decreased after P. angulata treatment. In conclusion, the present work demonstrated the genotoxic effects of P. angulata extract on human lymphocytes in vitro. 相似文献
14.
Giampiero Sacchetti Paola Pittia Manuela Biserni Gian G. Pinnavaia & Marco D. Rosa 《International Journal of Food Science & Technology》2003,38(2):135-143
Summary Ready‐to‐eat breakfast cereals immersed in milk undergo undesirable changes in texture because of sudden moisture uptake. The textural changes are ascribable to a plasticizing effect of water, which modifies the mechanical strength of products by softening the starch/protein matrix. In this work, some textural parameters of different cereal flakes were derived from the force–displacement curves monitored during 300 s of immersion in milk. Hardness loss, deformability increment and changes in the force–displacement curve profile were calculated and plotted against soaking time. The application of a sugar coating process to a model cereal flake increased the initial product hardness and improved the preservation of the textural parameters during immersion. The Peleg model closely fitted the experimental data, with regression coefficients from 0.967 to 0.999. 相似文献
15.
A Di Lieto G De Rosa G Albano F Gallo M Pontillo R Micalef A Colucci A Paladini 《Canadian Metallurgical Quarterly》1996,23(4):220-228
Clinical and pathological changes of the mammary gland have been studied in 64 women affected by symptomatic Benign Breast Disease (BBD) coexisting with endometriosis or uterine leiomyomata. These patients were rendered hypoestrogenic by subcutaneous administration of the LH-RH analogue Goserelin depot [D-ser (tBu)6 Aza-Gly10-GnRH (ICI118630)] performed every 28 days, for six months. They were evaluated clinically and ultrasonographically before and after treatment to find possible changes of BBD as well as of endometriosis or uterine leiomyomata. Mammary biopsies were performed before and after treatment in all the patients to study the changes of EGF-R expression. Results showed that clinical improvement is accompanied with a reduction of EGF-R expression. 相似文献
16.
F.J. Rodriguez L.A. García de la Rosa A. Alatorre J. Ibaez L. Godinez S. Gutierrez P. Herrasti 《Progress in Organic Coatings》2007,60(4):297-302
This paper reports the capacity of polypyrrole to reduce toxic hexavalent chromium (Cr(VI)). The influence of using different electrolytes during the polymer's synthesis has been studied. To improve the reduction of Cr(VI), the parameters considered were the polypyrrole morphology and the amount of conducting polymer. Polypyrrole obtained by cyclic voltammetry at a low sweep rate using KBr as supporting electrolyte showed better performance for Cr(VI) reduction compared to coatings obtained by constant potential or cyclic voltammetry at high sweep rates. 相似文献
17.
KN Prasad E Carvalho J Edwards-Prasad FG La Rosa S Kumar JH Kim A Meyers S Kentroti 《Canadian Metallurgical Quarterly》1994,(5):312-320
This study reports the establishment of alpha-amylase-producing human parotid pleomorphic adenoma cell lines (2HP and 2HP1) which have been maintained in culture for over 1 yr. The procedures required preparation of cellular clumps from tumor tissue and plating them on plasma clot or precoated dishes. During the initial phase of growth they required modified MCDB-153 medium without serum. When cells showed signs of degeneration they were changed to MCDB-153 medium containing first 2% and then 10% heat inactivated fetal bovine serum. Although cells grew well in MCDB-153 containing 10% serum, the epithelial cell morphology was not distinct. Therefore, the growth and morphology of cells grown in MCDB-10% serum were compared with those in RPMI growth medium containing 10% fetal bovine serum and F12 containing 10% agammaglobulin newborn bovine serum. Although the growth of cells was a little slower in F12 medium than those in MCDB and RPMI, the epithelial cell morphology was maintained better than in other growth media. The cells of 2HP and 2HP1 produce low levels of alpha-amylase and relatively high levels of alpha-amylase mRNAs of 1176 and 702 bp and contain neurofilament-160, a neuronal-specific marker. The cells of 2HP1 are tumorigenic when tested in athymic mice, but the cells of 2HP are not. The establishment of amylase-producing human parotid adenoma cell lines of different characteristics in culture provides a new opportunity to study the mechanisms of differentiation and transformation, and regulation of alpha-amylase in these cells. 相似文献
18.
Effect of atmospheric pollutants on the corrosion of high power electrical conductors: Part 1. Aluminium and AA6201 alloy 总被引:2,自引:0,他引:2
Rosa Vera 《Corrosion Science》2006,48(10):2882-2900
The aim of this study was to evaluate the joint effect of marine and industrial pollutants on the atmospheric corrosion of aluminium and its AA6201 alloy. Weight loss was determined after 4, 11, 16 and 24 months exposure being morphology and attack intensity analysed through SEM-EDX. Both materials showed the most intense attack for the highest SO2 contents. Good correlation among weight loss, attack depth and tensile strength to rupture with time and with pollutant contents was determined for both materials in most sites. The cause for low aggressiveness of the heaviest Cl− polluted atmosphere on aluminium was electrochemically demonstrated. 相似文献
19.
Lucia Garcia-Garcia Laia Olle Margarita Martin Jordi Roca-Ferrer Rosa Muoz-Cano 《International journal of molecular sciences》2021,22(10)
Adenosine is a nucleoside involved in the pathogenesis of allergic diseases. Its effects are mediated through its binding to G protein-coupled receptors: A1, A2a, A2b and A3. The receptors differ in the type of G protein they recruit, in the effect on adenylyl cyclase (AC) activity and the downstream signaling pathway triggered. Adenosine can produce both an enhancement and an inhibition of mast cell degranulation, indicating that adenosine effects on these receptors is controversial and remains to be clarified. Depending on the study model, A1, A2b, and A3 receptors have shown anti- or pro-inflammatory activity. However, most studies reported an anti-inflammatory activity of A2a receptor. The precise knowledge of the adenosine mechanism of action may allow to develop more efficient therapies for allergic diseases by using selective agonist and antagonist against specific receptor subtypes. 相似文献
20.
C. Tuve' R. Potenza M. Chiorboli M.G. Grimaldi F. La Rosa F. Raimondo M. Marinelli E. Milani A. Tucciarone G. Verona Rinati M. Donato G. Faggio G. Messina S. Santangelo G. Pucella 《Diamond and Related Materials》2006,15(11-12):1986
Polycrystalline (pCVD) and single crystal (scCVD) diamond films grown from Chemical Vapour Deposition (CVD), if sufficiently pure at Raman analysis, are very good materials for beam or flux monitors inside accelerators or nuclear reactors. This is because they are very hard to damage in high radiation fields and very resistant to high temperatures. Films of pCVD diamond are, however, not so good as spectroscopy detectors due to inhomogeneities induced by their growth in grains with the consequent presence of grain boundaries which worsen their energy resolution. The latter can be significantly improved by growing scCVD diamond films onto HPHT synthetic diamond substrates. We have shown that it is possible to measure the density of defects inside diamond specimens using as probes suitable penetrating nuclear radiations. With the preliminary results reported here we'll show that, bombarding CVD diamond films grown at Roma “Tor Vergata” with energetic protons and 4He, 6Li and 12C ions produced in the accelerators of Catania laboratories, the pulse height defects are higher than those in silicon detectors and likewise well described by a power law in the deposited energy. Furthermore, we'll show that pulse heights for the same particles seem to depend on the duration of the measurement, thus exhibiting a sort of depolarization of the insulator when exposed to the electric voltage which makes it a particle detector. 相似文献