全文获取类型
收费全文 | 1517篇 |
免费 | 85篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 19篇 |
综合类 | 12篇 |
化学工业 | 518篇 |
金属工艺 | 35篇 |
机械仪表 | 35篇 |
建筑科学 | 119篇 |
矿业工程 | 2篇 |
能源动力 | 47篇 |
轻工业 | 125篇 |
水利工程 | 3篇 |
石油天然气 | 3篇 |
无线电 | 103篇 |
一般工业技术 | 297篇 |
冶金工业 | 53篇 |
原子能技术 | 14篇 |
自动化技术 | 223篇 |
出版年
2023年 | 18篇 |
2022年 | 33篇 |
2021年 | 41篇 |
2020年 | 25篇 |
2019年 | 39篇 |
2018年 | 37篇 |
2017年 | 30篇 |
2016年 | 55篇 |
2015年 | 63篇 |
2014年 | 61篇 |
2013年 | 72篇 |
2012年 | 76篇 |
2011年 | 122篇 |
2010年 | 84篇 |
2009年 | 90篇 |
2008年 | 67篇 |
2007年 | 79篇 |
2006年 | 52篇 |
2005年 | 60篇 |
2004年 | 50篇 |
2003年 | 41篇 |
2002年 | 39篇 |
2001年 | 19篇 |
2000年 | 24篇 |
1999年 | 30篇 |
1998年 | 25篇 |
1997年 | 19篇 |
1996年 | 16篇 |
1995年 | 16篇 |
1994年 | 12篇 |
1993年 | 16篇 |
1992年 | 13篇 |
1991年 | 23篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 15篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1972年 | 4篇 |
1969年 | 4篇 |
排序方式: 共有1608条查询结果,搜索用时 0 毫秒
31.
32.
Poly(methylmethacrylate) (PMMA), poly(butylmethacrylate) (PBMA), and poly(decylmethacrylate) (PDMA) are completely miscible with toluene at normal pressure from room temperature up to the boiling point of the solvent. In alkanes (C6 to C10) and 1-pentanol the solubility increases with the length of the side chain of the polymer: PMMA always exhibits a solubility gap within the above temperature range, PBMA shows upper critical solution temperatures (except n-hexane, which is a non-solvent), and PDMA mixes completely with all alkanes under consideration. Alcohols (up to C4) are non-solvents for PMMA but theta solvents for PBMA and PDMA (except ethanol which is a non-solvent for the latter). The low temperature demixing of ethanol/PBMA is shifted towards lower temperatures by pressure. 相似文献
33.
Summary: The influence of number‐average molecular weight ranging from 1.4 · 104 to 1.2 · 106 g/mol on the thermal behaviour of polytetrafluoroethylene (PTFE) has been studied. Samples have been prepared by radiation‐induced degradation of commercial PTFE. The molecular weight has been calculated using end‐group concentration determined by infrared (IR) spectroscopy and 19F solid‐state nuclear magnetic resonance (NMR) spectroscopy. Melting and crystallisation heats were investigated by differential scanning calorimetry (DSC). The results have been discussed with respect to quantitative relationships between number‐average molecular weight and heat of crystallisation of PTFE described in the literature. The molecular weight calculated from Suwa's equation, which is often used in the literature, has been found to be too low.
34.
Sirirung Wongsakul Poonsuk Prasertsan Uwe T. Bornscheuer Aran H‐Kittikun 《European Journal of Lipid Science and Technology》2003,105(2):68-73
Commercial immobilized lipases were used for the synthesis of 2‐monoglycerides (2‐MG) by alcoholysis of palm and tuna oils with ethanol in organic solvents. Several parameters were studied, i.e., the type of immobilized lipases, water activity, type of solvents and temperatures. The optimum conditions for alcoholysis of tuna oil were at a water activity of 0.43 and a temperature of 60 °C in methyl‐tert‐butyl ether for ~12 h. Although immobilized lipase preparations from Pseudomonas sp. and Candida antarctica fraction B are not 1, 3‐regiospecific enzymes, they were considered to be more suitable for the production of 2‐MG by the alcoholysis of tuna oil than the 1, 3‐regiospecific lipases (Lipozyme RM IM from Rhizomucor miehei and lipase D from Rhizopus delemar). With Pseudomonas sp. lipase a yield of up to 81% 2‐MG containing 80% PUFA (poly‐unsaturated fatty acids) from tuna oil was achieved. The optimum conditions for alcoholysis of palm oil were similar as these of tuna oil alcoholysis. However, lipase D immobilized on Accurel EP100 was used as catalyst at 40 °C with shorter reaction times (<12 h). This lead to a yield of ~60% 2‐MG containing 55.0‐55.7% oleic acid and 18.7‐21.0% linoleic acid. 相似文献
35.
Vladimir Rozenshtein Alexander Berg Haim Levanon Uwe Krueger Dietmar Stehlik Yuri Kandrashkin Art Van Der Est 《Israel journal of chemistry》2003,43(3-4):373-381
Light-induced spin-polarized transient EPR spectra are reported for several water-soluble copper porphyrins. The spectra are assigned to the doublet ground state, with emissive spin polarization resulting from photoexcitation and subsequent electronic relaxation. In contrast to other systems for which polarization of a doublet ground state has been observed, the exchange interactions in the copper porphyrins are strong and the geometry is fixed. It is proposed that intersystem crossing from the photoexcited trip-doublet to the trip-quartet state can lead to net polarization of the spin system and that this polarization is maintained during electronic decay, possibly via charge-transfer and exciplex states. The intensity of the observed spin polarization is essentially independent of the molecular orientation in the external field, but is strongly dependent on the nature of the charged peripheral groups. Possible reasons for this behavior are discussed. 相似文献
36.
Uwe Hassler 《时间序列分析杂志》2013,34(5):562-573
The effect of temporal aggregation on bivariate spectral measures is investigated. First, the low‐frequency regression coefficient turns out to be invariant under aggregation irrespective of differencing, with the exception of when the aggregation of flow and stock variables is combined. Second, the long‐run squared coherency is invariant with respect to aggregation irrespective of differencing. Third, for frequencies different from zero, limiting results for a growing aggregation level m are obtained equal to those at frequency 0 of the underlying basic series. Hence, all frequency domain information is distorted by aggregation apart from the long‐run one. This also holds true for the phase angle that always approaches zero with growing aggregation level m. The sole exception to these findings is the case of the skip sampling stationary series. Moreover, for finite aggregation level, one may exactly quantify the aggregational effect on each cycle of interest. Numerical examples illustrate our results. 相似文献
37.
38.
Uwe Kruger David Antory Juergen Hahn George W. Irwin Geoff McCullough 《Computers & Chemical Engineering》2005,29(11-12):2355
Although principal component analysis (PCA) is an important tool in standard multivariate data analysis, little interest has been devoted to assessing whether the underlying relationship within a given variable set can be described by a linear PCA model or whether nonlinear PCA must be utilized. This paper addresses this deficiency by introducing a nonlinearity measure for principal component models. The measure is based on the following two principles: (i) the range of recorded process operation is divided into smaller regions; and (ii) accuracy bounds are determined for the sum of the discarded eigenvalues. If this sum is within the accuracy bounds for each region, the process is assumed to be linear and vice versa. This procedure is automated through the use of cross-validation. Finally, the paper shows the utility of the new nonlinearity measure using two simulation studies and with data from an industrial melter process. 相似文献
39.
Summary: The powder blend of poly(acrylic acid) (PAA) with zinc oxide or zinc oxide/magnesium oxide was applied successfully to produce zinc polycarboxylate during the 3D dispensing of an aqueous ink by means of 3D printers (Z402? from ZCorporation and Deskmodeler? from bmt Company). The layer‐by‐layer inkjet printing afforded zinc ionomer 3D objects with excellent water resistance, no inherent color formation and high mechanical and dimensional stabilities. In contrast to the 3D printing of conventional powders such as starch/cellulose/dextrose blends, poly(vinyl alcohol) (PVA) or plaster, no postprinting treatments were required. Excellent dimensional accuracy of the models, as evidenced by very small deviation of the dimensions from those of the corresponding CAD data, was achieved. The mechanical properties improved with increasing PAA content, ink amount (saturation value), decreasing particle size of the sintered zinc oxide ceramic. At high PAA content >7 wt.‐%, post‐treatment with aqueous zinc acetate solution improved the mechanical properties. The setting time of the zinc cements shows no significant effect on the mechanical properties, but on the water resistance of the models. The porosity of the 3D objects, measured by means of X‐ray microtomography (μ‐CT), had profound impact on the variations of the mechanical properties of the 3D objects prepared by 3D printing processes.
40.
Yvonne Rellmann Elco Eidhof Uwe Hansen Lutz Fleischhauer Jonas Vogel Hauke Clausen-Schaumann Attila Aszodi Rita Dreier 《International journal of molecular sciences》2022,23(1)
Ageing or obesity are risk factors for protein aggregation in the endoplasmic reticulum (ER) of chondrocytes. This condition is called ER stress and leads to induction of the unfolded protein response (UPR), which, depending on the stress level, restores normal cell function or initiates apoptotic cell death. Here the role of ER stress in knee osteoarthritis (OA) was evaluated. It was first tested in vitro and in vivo whether a knockout (KO) of the protein disulfide isomerase ERp57 in chondrocytes induces sufficient ER stress for such analyses. ER stress in ERp57 KO chondrocytes was confirmed by immunofluorescence, immunohistochemistry, and transmission electron microscopy. Knee joints of wildtype (WT) and cartilage-specific ERp57 KO mice (ERp57 cKO) were analyzed by indentation-type atomic force microscopy (IT-AFM), toluidine blue, and immunofluorescence/-histochemical staining. Apoptotic cell death was investigated by a TUNEL assay. Additionally, OA was induced via forced exercise on a treadmill. ER stress in chondrocytes resulted in a reduced compressive stiffness of knee cartilage. With ER stress, 18-month-old mice developed osteoarthritic cartilage degeneration with osteophyte formation in knee joints. These degenerative changes were preceded by apoptotic death in articular chondrocytes. Young mice were not susceptible to OA, even when subjected to forced exercise. This study demonstrates that ER stress induces the development of age-related knee osteoarthritis owing to a decreased protective function of the UPR in chondrocytes with increasing age, while apoptosis increases. Therefore, inhibition of ER stress appears to be an attractive therapeutic target for OA. 相似文献