全文获取类型
收费全文 | 365篇 |
免费 | 27篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 9篇 |
综合类 | 2篇 |
化学工业 | 97篇 |
金属工艺 | 4篇 |
机械仪表 | 10篇 |
建筑科学 | 12篇 |
能源动力 | 11篇 |
轻工业 | 53篇 |
水利工程 | 2篇 |
无线电 | 22篇 |
一般工业技术 | 46篇 |
冶金工业 | 64篇 |
原子能技术 | 2篇 |
自动化技术 | 60篇 |
出版年
2023年 | 1篇 |
2022年 | 12篇 |
2021年 | 20篇 |
2020年 | 12篇 |
2019年 | 4篇 |
2018年 | 11篇 |
2017年 | 10篇 |
2016年 | 12篇 |
2015年 | 19篇 |
2014年 | 8篇 |
2013年 | 28篇 |
2012年 | 21篇 |
2011年 | 25篇 |
2010年 | 23篇 |
2009年 | 18篇 |
2008年 | 21篇 |
2007年 | 8篇 |
2006年 | 16篇 |
2005年 | 8篇 |
2004年 | 9篇 |
2003年 | 10篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 10篇 |
1998年 | 18篇 |
1997年 | 15篇 |
1996年 | 6篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有394条查询结果,搜索用时 31 毫秒
51.
Bothrops lanceolatus venom has high caseinolytic, phospholipasic, esterolytic and hemorrhagic activities. In spite of having no coagulant effect on plasma, this venom contains a thrombin-like enzyme. Using gel filtration and ion-exchange chromatographies, we have purified an esterolytic fraction (F-II-1a) from this venom with a protein yield of 4% and a 58% recovery in enzyme activity. SDS-PAGE in the presence of beta-mercaptoethanol showed that the enzyme is a single chain polypeptide with a MW=38,100. Immunodiffusion and immunoelectrophoresis of fraction F-II-1a against serum from horses immunized with B. lanceolatus venom and against rabbit antiserum prepared using fraction F-II-1a both showed a single immunoprecipitin line. The Km and Vmax values for TAME hydrolysis were 0.85 mM and 38.6 micromol/min/mg, respectively. The esterolytic activity was completely inhibited by PMSF (10 mM) but not by EDTA (20 mM). Fraction F-II-1a hydrolyzed the alpha and beta chains of fibrinogen. Degradation of the alpha chain occurred within 10 min while that of the beta-chain was slower. The enzyme had no effect on the gamma-chain even after 4 h of hydrolysis. 相似文献
52.
Gorji Marzban Anita Herndl Sara Pietrozotto Srijib Banerjee Christian Obinger Fatemeh Maghuly Rainer Hahn Donato Boscia Hermann Katinger Margit Laimer 《Food chemistry》2009
Mal d 2, a thaumatin-like protein from apple was previously described to react to almost 75% of the apple allergic patient sera. Based on the molecular structure of this protein, the present study focused on the conformational stability of Mal d 2 in relation to in vitro IgE-binding under different physico-chemical conditions and proteolysis. The structural integrity of Mal d 2 was monitored using SDS–PAGE, Western blotting using polyclonal antibodies and human sera, fluorescence spectrometry and circular dichroism. Results confirmed the stability of Mal d 2. However, Mal d 2 was reactive to human serum IgEs mainly after reduction of disulphide bridges fixing the α-helical domain II. Contrary to previous assumptions, the current findings suggest that the allergenic epitopes of Mal d 2 are hidden inside the protein structure and none of the rigorous conditions applied in industrial juice processing or digestive proteolysis enhance or reduce the binding to IgE molecules. 相似文献
53.
The life cycle of schistosomes is reviewed in its various steps, both in permissive hosts (in which the cycle is completed) and in nonpermissive hosts (which excrete no viable eggs as a result of the infection). A large worm loss occurs at (or after) the lung stage in both types of hosts (normal attrition) and some nonpermissive hosts (like the rat) have an additional elimination of worms from the portal circulation. Worm growth and reproductive maturation are also impaired in several nonpermissive hosts and the possible host-parasite interactions leading to such limitations are discussed, with special reference to hormonal influences. Attention is also given to peculiar phenomena occurring in some hosts, like the late portal worm elimination in rhesus monkeys, the migration from mesenteric veins to lungs in rats, and the block to egg excretion in guinea pigs. The steps of the schistosome life cycle which appear vulnerable in several hosts are contrasted with the steps which are carried out successfully in the majority of hosts studied. 相似文献
54.
We here report on the DC and microwave performance of HEMTs tested on wafer under different temperature conditions. The relevant experimental data show that the most important electrical parameters, such as the output current, the threshold voltage, the transconductance and the forward transmission coefficient, are sensibly affected by thermal phenomena. We focused our attention on the variations of the above parameters with the temperature because such a detailed knowledge is essential to establish the optimum bias point for a given application. Furthermore, we analyze the influence of the DC quiescent point degradations, due to thermal phenomena, on the small signal equivalent circuit. Since the thermal behavior of the circuit model is a function of the bias, we examine the behavior of the circuit elements vs. temperature over a wide range of bias conditions. 相似文献
55.
G Nocivelli G Bordiga M Castellani R Chiesa F Donato 《Canadian Metallurgical Quarterly》1993,86(6):815-819
The authors report the results of the first two rounds of a mammographic screening program by the Health District of Gardone Val Trompia (Brescia) including women 50 to 69 years old. 9,650 women were invited for round one and 6,415 (66.5%) attended; 9,656 were invited for round two and 6,552 (67.8%) attended. Fifty-four cancers were found in round one (detection rate: 8.4/1000): 11.1% of them were in situ carcinomas, 63% were T1 and 24.1% were T2 lesions, or higher. In round two, 32 lesions were detected (detection rate: 4.9/1000): 15.6% of them were in situ carcinomas, 78.1% were T1 and 3.2% were T2 lesions. In the positive cases axillary lymph nodes involvement was observed in 24.1% of cases in round one and was unknown in 27.8%, but the figures decreased to 6.2% and 9.4%, respectively, in round two. Effectiveness indicators were always observed. 相似文献
56.
Donato Trigiante 《Calcolo》1973,10(2):117-131
Sommario In questa nota descriviamo una classe di possibili generalizzazioni del metodo della secaute per la soluzione di equazioni
e di sistemi di equazioni, cui, per ragioni che risulteranno evidenti nel paragrafo 1.1., abbiamo dato il nome di metodo dei
momenti.
Vienes discusso l'ordine di convergenza e presentati alcuni esempi. Nel paragrafo 1.3., limitaitamente al caso della secante,
viene dato un nuovo criterio per la scelta del punto da scartare dopo ogni iterazione, il quale offre notevoli vantaggi.
In this paper we describe a class of possible generalization of the secant method for solving equations and systems of equations. To this class, for the reason illustrated in paragraph 1.1., we gave the name of the method of moments. The convergency order is discussed and some examples are introduced. In the paragraph 1.3., only for the sant case, a new criterion is given for the choice of the point to be discarded after every iterations. It offers some remarkable advantages.相似文献
57.
MS Pearle HL Pierce GL Miller JA Summa JM Mutz BA Petty CG Roehrborn JV Kryger SY Nakada 《Canadian Metallurgical Quarterly》1998,160(4):1260-1264
PURPOSE: We compare the efficacy of percutaneous nephrostomy with retrograde ureteral catheterization for renal drainage in cases of obstruction and infection associated with ureteral calculi. MATERIALS AND METHODS: We randomized 42 consecutive patients presenting with obstructing ureteral calculi and clinical signs of infection (temperature greater than 38 C and/or white blood count greater than 17,000/mm.3) to drainage with percutaneous nephrostomy or retrograde ureteral catheterization. Preoperative patient and stone characteristics, procedural parameters, clinical outcomes and costs were assessed for each group. RESULTS: Urine cultures obtained at drainage were positive in 62.9% of percutaneous nephrostomy and 19.1% of retrograde ureteral catheterization patients. There was no significant difference in the time to treatment between the 2 groups. Procedural and fluoroscopy times were significantly shorter in the retrograde ureteral catheterization (32.7 and 5.1 minutes, respectively) compared with the percutaneous nephrostomy (49.2 and 7.7 minutes, respectively) group. One treatment failure occurred in the percutaneous nephrostomy group, which was successfully salvaged with retrograde ureteral catheterization. Time to normal temperature was 2.3 days in the percutaneous nephrostomy and 2.6 in the retrograde ureteral catheterization group, and time to normal white blood count was 2 days in the percutaneous nephrostomy and 1.7 days in the retrograde ureteral catheterization group (p not significant). Length of stay was 4.5 days in the percutaneous nephrostomy group compared with 3.2 days in the retrograde ureteral catheterization group (p not significant). Cost analysis revealed that retrograde ureteral catheterization was twice as costly as percutaneous nephrostomy. CONCLUSIONS: Retrograde ureteral catheterization and percutaneous nephrostomy effectively relieve obstruction and infection due to ureteral calculi. Neither modality demonstrated superiority in promoting a more rapid recovery after drainage. Percutaneous nephrostomy is less costly than retrograde ureteral catheterization. The decision of which mode of drainage to use may be based on logistical factors, surgeon preference and stone characteristics. 相似文献
58.
Chaline Detoni Nakédia M. F. Carvalho Rodrigo O. M. A. de Souza Donato A. G. Aranda O. A. C. Antunes 《Catalysis Letters》2009,129(1-2):79-84
The use of mononuclear Cu(II) 2,2′-bipyridine and 1,10-phenantroline complexes as catalysts in the oxidation of benzene, using hydrogen peroxide and tert-butyl hydroperoxide as oxidant in CH3CN/H2O solution is presented. The reactions were carried out at 25 and at 50 °C. The complexes [Cu(bipy)3]Cl2 · 6H2O (1), [Cu(bipy)2Cl]Cl · 5H2O (2), [Cu(bipy)Cl2] (3), [Cu(phen)3]Cl2 · 7H2O (4), [Cu(phen)2Cl]Cl · 5H2O (5), [Cu(phen)Cl2] (6) were able to oxidize benzene into phenol, hydroquinone and p-benzoquinone. Highest conversion (22%) was obtained using [Cu(Phen)Cl2] (6) as catalyst. 相似文献
59.
Katarzyna Świrk Paulina Summa Dominik Wierzbicki Monika Motak Patrick Da Costa 《International Journal of Hydrogen Energy》2021,46(34):17776-17783
A series of V-promoted hydrotalcite-derived nickel catalysts (1.0, 2.0, and 4.0 wt%) were tested in CO2 methanation. Ni–I–V2.0 with 2.0 wt% vanadium loading showed the highest catalytic activity, achieving 74.7% of CO2 conversion and 100% of CH4 selectivity at 300 °C. XRD and XANES analyses showed that the smallest Ni0 particles in Ni–I–V2.0 were consistent with the improved textural features observed for this catalyst. Moreover, CO2-TPD revealed the highest sum of weak and medium basic sites in Ni–I–V2.0 that can positively influence catalytic behavior. For the studied catalysts, a clear correlation was demonstrated between the catalytic activity and specific surface area, as well as the basic properties. 相似文献
60.
Samia Tássia Andrade Maciel Alexander Andrey Lopes da Silva Yasmin Guimarães Pedro Cristiano Nunes da Silva Leôncio Diógenes Tavares Câmara João Monnerat Araújo Ribeiro de Almeida Emerson Schwingel Ribeiro Gabriel Francisco da Silva Lisiane Santos Freitas Donato Alexandre Gomes Aranda 《化学工程与技术》2020,43(11):2149-2159
The catalytic hydrolysis of soybean oil was used as an alternative for the production of monoglycerides (MG) and diglycerides (DG). The reactions were conducted in a stainless-steel tubular reactor in the temperature range of 240–290 °C, on niobium phosphate (NBP) and niobium oxide (NBO) as catalysts. In the hydrolysis reactions at 270 °C, the maximum selectivities of the products of interest were obtained at 22 % MG and 48 % DG for the reaction with NBP, and 7 % MG and 33 % DG with NBO, for 59 % and 36 % of triglyceride conversion in 10 min, respectively. The proposed kinetic model presented a good fit of the theoretical model with the experimental data, showing that the previous hypotheses considered for the mechanism development are suitable for describing the kinetics of soybean oil hydrolysis. 相似文献