全文获取类型
收费全文 | 1351篇 |
免费 | 42篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 19篇 |
综合类 | 10篇 |
化学工业 | 345篇 |
金属工艺 | 29篇 |
机械仪表 | 16篇 |
建筑科学 | 33篇 |
矿业工程 | 2篇 |
能源动力 | 23篇 |
轻工业 | 107篇 |
水利工程 | 9篇 |
石油天然气 | 1篇 |
无线电 | 95篇 |
一般工业技术 | 219篇 |
冶金工业 | 313篇 |
原子能技术 | 14篇 |
自动化技术 | 160篇 |
出版年
2022年 | 11篇 |
2021年 | 20篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 24篇 |
2016年 | 21篇 |
2015年 | 24篇 |
2014年 | 39篇 |
2013年 | 60篇 |
2012年 | 39篇 |
2011年 | 48篇 |
2010年 | 42篇 |
2009年 | 36篇 |
2008年 | 52篇 |
2007年 | 49篇 |
2006年 | 38篇 |
2005年 | 54篇 |
2004年 | 33篇 |
2003年 | 28篇 |
2002年 | 35篇 |
2001年 | 28篇 |
2000年 | 21篇 |
1999年 | 32篇 |
1998年 | 84篇 |
1997年 | 55篇 |
1996年 | 54篇 |
1995年 | 34篇 |
1994年 | 21篇 |
1993年 | 28篇 |
1992年 | 28篇 |
1991年 | 13篇 |
1990年 | 24篇 |
1989年 | 18篇 |
1988年 | 19篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 20篇 |
1984年 | 18篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 14篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 13篇 |
1976年 | 17篇 |
1970年 | 10篇 |
1968年 | 7篇 |
1966年 | 5篇 |
排序方式: 共有1395条查询结果,搜索用时 62 毫秒
1.
Marcus Heinze Sandra Starke Marcel Händler Hartmut Komber Marco Drache Norbert Moszner Brigitte Voit Doris Pospiech 《应用聚合物科学杂志》2019,136(48):48256
We demonstrate in this study that the combination of modern inline monitoring methods [here: inline nuclear magnetic resonance (NMR)] with simulations gains more exact and profound kinetic results than previously used methods like linearization without that combination. The 1H-NMR spectroscopic data (more than 100 data points) are used to construct the copolymerization diagram. The reactivity ratios are obtained applying the van Herks nonlinear least square method. The examination of the radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) with (2-{[2-(ethoxycarbonyl)prop-2-en-1-yl]oxy}ethyl) phosphonic acid (ECPPA) as important adhesive monomer used in dentistry yields reactivity ratios of rHEMA = 1.83; rECPPA = 0.42. The copolymerization diagram reflects nonideal, non-azeotropic copolymerization. The sequence distribution of the obtained by Monte Carlo simulation indicates the generation of statistical copolymers. As an important finding, it is demonstrated that the repeating units responsible for etching and adhesion are arranged over the whole polymer chain, which is necessary to achieve proper functionality. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48256. 相似文献
2.
Direct charging of thin slabs of low carbon steel (0.05%C) was investigated by using laboratory tests on a thin-slab-casting Simulator linked with the hot deformation Simulator (Wumsi). Starting with a different initial thickness of simulated thin slabs (45 down to 25 mm) the total strain ?∑ was varied. Hot deformation schedules (with and without roughing) with different finishing temperatures TF lead to some differences in the hot strip microstructure. Nevertheless, after cold rolling and batch annealing, a rather uniform pancake-structure and a pronounced {111}-texture were achieved in the cold strip without any significant relation to the processing routs. The measurement of final mechanical properties proved that a good deep drawability of cold strip can be achieved with direct charging of thin slabs, well comparable to that after a conventional cold charging of thick slabs. 相似文献
3.
A multilayer theory has been developed for unidirectional/cross-ply unbalanced laminates subjected to surface shear tractions, using the assumption of plane strain. The analytical solution for the stress field in the laminate is obtained and it is shown that the stresses in each layer are in good agreement with the results of a three-dimensional finite element analysis. Approximate formulae for the analytical stresses are also derived for a laminate subjected to an offset distributed force at one end. The accuracy of this solution is shown by comparison with a three-dimensional finite element analysis. 相似文献
4.
5.
Computing surfaces invariant under subdivision 总被引:3,自引:0,他引:3
In this paper, we propose a general subdivision algorithm for generating surfaces. The algorithm has as motivation our earlier work on the design of free form curves where similar ideas were investigated. Here we describe some properties of uniform refinement algorithms for surface generation. A detail analysis of their properties will be given later by one of us. 相似文献
6.
7.
A new sub-class of binding protein-dependent transporter with specificity for a broad range of polar amino acids has been identified by sequence comparison, in Rhizobium leguminosarum, Rhodobacter capsulatus, Escherichia coli and Pseudomonas fluorescens. Southern blotting and PCR analysis has shown that transporters from this new sub-class are widely distributed in Gram-negative bacteria, including, in addition to the above, Citrobacter freundii, Erwinia carotovorum and Rhizobium meliloti. ABC transporters of polar amino acids can be divided into two groups: those with narrow solute specificity and the newly identified sub-class with broad solute specificity. The binding and inner membrane proteins from transporters with a broad solute specificity are larger by approximately 30% than those with a narrow solute specificity. Multiple alignment of the inner membrane proteins from all sequenced polar amino acid transporters indicates there is an N-terminal conserved region that may be involved in solute specificity. A conserved arginine or lysine at residue 30 of this region is changed to glutamate in arginine transporters. Residue 53 also has a strong correlation with the charge on the transported solute, with basic amino acid transporters replacing an aliphatic amino acid at this position with a negatively charged amino acid. The general amino acid permease from R. leguminosarum, which will transport aliphatic as well as basic and acidic amino acids, juxtaposes two prolines at residues 52 and 53 of the N-terminal conserved region. 相似文献
8.
An intracellular endopeptidase was purified from cell-free extracts of Lactobacillus delbrueckii subsp. bulgaricus B14 by anion exchange chromatography on DEAE-Sepharose, hydroxyapatite chromatography, second anion exchange chromatography on Mono-Q, and metal-chelating affinity chromatography. The endopeptidase was a monomer with a molecular mass of approximately 70 kDa determined by SDS-PAGE and gel filtration. Various oligopeptides (e.g. Met-enkephalin, bradykinin) were hydrolysed by the endopeptidase. Exopeptidase activity and cleavage of dipeptides or tripeptides was not observed. The KM value for the cleavage of Metenkephalin was 1.2 mM. Temperature and pH optima were 47 °C and pH 7.7, respectively. The endopeptidase was inhibited by the classical agents for metal-dependent (EDTA) and serine (DFP) enzymes. Activity was increased by Co2+ and Mg2+, no effect was observed with Ca2+. After inhibition with EDTA, enzyme activity could be restored fully by Co2+. Activity was inhibited by Zn2+, Mn2+, Fe2+, Cu2+, Cd2+ and Hg2+. The N-terminal sequence of the endopeptidase was determined as: H2N-Val-Arg-Gly-Gly-Ser-Gly-Asp-Thr-Thr-Val-0H. 相似文献
9.
10.
The clinical presentation, electrocardiographic findings, and technetium-99m sestamibi single-photon emission computed tomography (SPECT) imaging results of 134 consecutive patients who underwent nuclear exercise testing within 14 days of an acute myocardial infarction (AMI) were correlated with cardiac events over a 15 +/- 10-month follow-up. Whereas only 23 patients (17%) had chest pain and 31 (23%) had ischemic ST-segment depression during exercise, 94 (70%) had ischemia on SPECT (p < 0.001). On follow-up, 13 patients experienced a cardiac event: 7 were rehospitalized for unstable angina, 3 had recurrent AMI, and 3 died of cardiac causes. Ischemia on the sestamibi images identified 11 of these patients (85%), whereas chest pain identified only 3 (23%, p = 0.006), and electrocardiographic ischemia identified only 4 (31%, p = 0.017). The presence of either ischemia as seen on SPECT or defects in multiple vascular territories identified 12 patients (92%) with an event, including all who had cardiac death. By Cox regression analysis of clinical, stress, and image parameters, the number of ischemic defects on SPECT was the only significant correlate of a future event (chi-square = 4.62, p = 0.03), and patients with > or = 3 reversible sestamibi defects had an event rate of 38%. The extent of ischemia as seen on nuclear imaging remained a strong correlate (p = 0.008) of an event in the 54 patients (40%) who had received thrombolytic therapy. Thus, exercise technetium-99m sestamibi SPECT after AMI frequently reveals residual ischemia, and is better than clinical data, symptoms, and stress electrocardiographic data in identifying patients who will have a subsequent cardiac event. 相似文献