全文获取类型
收费全文 | 3359篇 |
免费 | 34篇 |
专业分类
电工技术 | 14篇 |
综合类 | 2篇 |
化学工业 | 212篇 |
金属工艺 | 37篇 |
机械仪表 | 20篇 |
建筑科学 | 55篇 |
能源动力 | 33篇 |
轻工业 | 98篇 |
水利工程 | 11篇 |
无线电 | 116篇 |
一般工业技术 | 218篇 |
冶金工业 | 2422篇 |
原子能技术 | 16篇 |
自动化技术 | 139篇 |
出版年
2023年 | 8篇 |
2022年 | 11篇 |
2021年 | 14篇 |
2020年 | 10篇 |
2019年 | 18篇 |
2018年 | 16篇 |
2017年 | 16篇 |
2016年 | 25篇 |
2015年 | 20篇 |
2014年 | 19篇 |
2013年 | 48篇 |
2012年 | 42篇 |
2011年 | 56篇 |
2010年 | 40篇 |
2009年 | 34篇 |
2008年 | 45篇 |
2007年 | 48篇 |
2006年 | 36篇 |
2005年 | 39篇 |
2004年 | 37篇 |
2003年 | 33篇 |
2002年 | 35篇 |
2001年 | 34篇 |
2000年 | 26篇 |
1999年 | 96篇 |
1998年 | 677篇 |
1997年 | 378篇 |
1996年 | 235篇 |
1995年 | 146篇 |
1994年 | 161篇 |
1993年 | 166篇 |
1992年 | 25篇 |
1991年 | 31篇 |
1990年 | 44篇 |
1989年 | 50篇 |
1988年 | 47篇 |
1987年 | 39篇 |
1986年 | 40篇 |
1985年 | 32篇 |
1984年 | 13篇 |
1983年 | 16篇 |
1982年 | 24篇 |
1981年 | 29篇 |
1980年 | 29篇 |
1979年 | 14篇 |
1977年 | 78篇 |
1976年 | 190篇 |
1975年 | 19篇 |
1974年 | 10篇 |
1972年 | 8篇 |
排序方式: 共有3393条查询结果,搜索用时 0 毫秒
51.
52.
Cover Picture: Development of Potent and Metabolically Stable APJ Ligands with High Therapeutic Potential (ChemMedChem 21/2016) 下载免费PDF全文
53.
Polystyrene (PS) blocks in poly(styrene-b-isobutylene-b-styrene) (PS-PIB-PS) block copolymers were partially sulfonated and the acid groups converted to Na+SO3− groups to create ionomers. Then, dimethylacetamide was used to selectively swell the ionic PS domains and the swollen films were exposed to sol-gel reactive tetraethylorthosilicate solutions. (EtO)4−xSi(OH)x monomers then permeated films so that sol-gel reactions occurred within/around the ionic PS domains. Environmental scanning electron microscopy/energy dispersive X-ray spectroscopy investigations showed that silicate structures can be incorporated within the interior of the ionomer films. Differential scanning calorimetry studies indicated that there is no variance in the PIB block Tg with respect to ionomer formation, or with respect to silicate loading of the ionomer at low levels, which suggests that the silicate component does not reside in the PIB phase. 23Na solid state NMR spectroscopy detected isolated Na+SO3− groups as well as aggregated SO3−Na+ ion pairs for ‘as cast’ and ‘dry’ non-silicate containing ionomer samples. In a hydrated sample, almost all Na+ ions were solvent-separated. AFM analysis showed that phase separation exists, but that the degree of order is significantly less than that for hybrids based on the corresponding benzyltrimethylammonium ionomer. This frustrated morphology was also seen in the results of small angle X-ray scattering experiments. Given the scale of organic/inorganic heterogeneity, these hybrids are properly classified as nanocomposites. 相似文献
54.
Industrially manufactured carbon blacks (CBs) provide highly dispersed carbon materials with a specific surface of up to 1700 m2 g–1. Precompaction at p > 10 MPa in the presence of 3–10 wt% PTFE (provided as a dispersion) is known to lead to stable electrodes for electrochemical supercapacitors. Specific capacitances for single electrodes (Cs,1) were measured by constant current cycling (CCC) at 34 mA cm–2 to be up to 250 F g–1. It is shown that substitution of PTFE by fluorine-free binders, such as aqueous dispersions of polystyrene, styrene/butadien-copolymer and ethylene/acrylic acid copolymer is possible. Optimum systems were with 3–10 wt% binders of butadiene/styrene copolymers. They allowed stable results within hundreds of cycles. No shedding of the CB particles was observed, and swelling of the electrode was minimum. 相似文献
55.
It is shown that industrial carbon blacks (CBs) are interesting materials for electrochemical supercapacitors (ECSCs). The specific areas A
s ranged from 28 to 1690 m2 g–1. The highest values were realized through activation in CO2 at 1100 °C. Precompacted carbon black electrodes with 5–10 wt% PTFE as a binder in the pellet in 10–12 M H2SO4 were characterized by constant current cycling, CCC, j = 20–50 mA cm–2. Voltage–time curves showed nearly pure capacitive behaviour. Specific capacitance of single electrodes, C
s,1, could be derived therefrom. A plot of C
s,1 against A
s shows a linear behavior according to C
s,1 = C
A,DL
A
s, where C
A,DL is the Helmholtz double layer capacitance per atomic surface area. Best fit was obtained with C
A,DL = 16 F cm–2. The highest experimental values, C
s,1 = 250 F g–1, are due to 60% of the theoretical maximum, which corresponds to an A
s calculated from both faces of isolated graphene layers. Only marginal pseudocapacitances are observed. Model cells for ECSCs (with microporous CelgardTM separators) could be extensively cycled (CCC). A monopolar cell endured Z > 2000 cycles. Bipolar cells (5 units) allowed 700 cycles. Practical problems such as the development of electrode holders and of carbon black filled polypropylene composites for current collectors are discussed. It is concluded that entirely metal-free ECSCs with low cost can be produced. 相似文献
56.
Epoxidation of 2-cyclohexen-1-ol with TBHP and TiO2–SiO2, Fe2O3–SiO2 and SiO2 aerogels has been studied. The influence of surface silanol groups and transition metal impurities in titania–silica on the product distribution has been analyzed. The results, supported by literature data, indicate that high surface area silica cannot generally be regarded as an inert matrix in epoxidation catalysts. Contribution of Ti-free silica limits the selectivity of Ti- and Si-containing catalysts in demanding epoxidation reactions. The activity of silica – together with the background oxidation of the olefin – may lead to overestimated intrinsic activities when the reaction rate is related to the Ti content of the catalyst. 相似文献
57.
58.
Fábián TK Hermann P Beck A Fejérdy P Fábián G 《International journal of molecular sciences》2012,13(4):4295-4320
There are numerous defense proteins present in the saliva. Although some of these molecules are present in rather low concentrations, their effects are additive and/or synergistic, resulting in an efficient molecular defense network of the oral cavity. Moreover, local concentrations of these proteins near the mucosal surfaces (mucosal transudate), periodontal sulcus (gingival crevicular fluid) and oral wounds and ulcers (transudate) may be much greater, and in many cases reinforced by immune and/or inflammatory reactions of the oral mucosa. Some defense proteins, like salivary immunoglobulins and salivary chaperokine HSP70/HSPAs (70 kDa heat shock proteins), are involved in both innate and acquired immunity. Cationic peptides and other defense proteins like lysozyme, bactericidal/permeability increasing protein (BPI), BPI-like proteins, PLUNC (palate lung and nasal epithelial clone) proteins, salivary amylase, cystatins, prolin-rich proteins, mucins, peroxidases, statherin and others are primarily responsible for innate immunity. In this paper, this complex system and function of the salivary defense proteins will be reviewed. 相似文献
59.
60.
Jeffrey R Stout B Sue Graves Abbie E Smith Michael J Hartman Joel T Cramer Travis W Beck Roger C Harris 《Journal of the International Society of Sports Nutrition》2008,5(1):1-6