全文获取类型
收费全文 | 1738250篇 |
免费 | 44312篇 |
国内免费 | 15520篇 |
专业分类
电工技术 | 46505篇 |
技术理论 | 24篇 |
综合类 | 20139篇 |
化学工业 | 307619篇 |
金属工艺 | 76693篇 |
机械仪表 | 57461篇 |
建筑科学 | 63897篇 |
矿业工程 | 18928篇 |
能源动力 | 56576篇 |
轻工业 | 126164篇 |
水利工程 | 18978篇 |
石油天然气 | 53066篇 |
武器工业 | 1772篇 |
无线电 | 220017篇 |
一般工业技术 | 312085篇 |
冶金工业 | 183983篇 |
原子能技术 | 36369篇 |
自动化技术 | 197806篇 |
出版年
2022年 | 14643篇 |
2021年 | 24129篇 |
2020年 | 18447篇 |
2019年 | 20182篇 |
2018年 | 23158篇 |
2017年 | 23572篇 |
2016年 | 28169篇 |
2015年 | 25908篇 |
2014年 | 39495篇 |
2013年 | 100650篇 |
2012年 | 50076篇 |
2011年 | 64335篇 |
2010年 | 56566篇 |
2009年 | 63970篇 |
2008年 | 57675篇 |
2007年 | 54651篇 |
2006年 | 56792篇 |
2005年 | 50408篇 |
2004年 | 48666篇 |
2003年 | 47634篇 |
2002年 | 45830篇 |
2001年 | 41947篇 |
2000年 | 40964篇 |
1999年 | 41225篇 |
1998年 | 53083篇 |
1997年 | 44839篇 |
1996年 | 40159篇 |
1995年 | 34450篇 |
1994年 | 31822篇 |
1993年 | 30876篇 |
1992年 | 27557篇 |
1991年 | 24378篇 |
1990年 | 24538篇 |
1989年 | 23409篇 |
1988年 | 21750篇 |
1987年 | 19828篇 |
1986年 | 19151篇 |
1985年 | 22409篇 |
1984年 | 22524篇 |
1983年 | 20387篇 |
1982年 | 19430篇 |
1981年 | 19531篇 |
1980年 | 18060篇 |
1979年 | 18525篇 |
1978年 | 17752篇 |
1977年 | 17525篇 |
1976年 | 18449篇 |
1975年 | 16026篇 |
1974年 | 15502篇 |
1973年 | 15605篇 |
排序方式: 共有10000条查询结果,搜索用时 378 毫秒
181.
182.
Kruglikov S. S. Zagorskii D. L. Kolesnikov V. A. Doludenko I. M. Bedin S. A. 《Theoretical Foundations of Chemical Engineering》2021,55(5):942-951
Theoretical Foundations of Chemical Engineering - The effect of the electrolyte composition, mass-transfer conditions, pore diameter, interpore distance, and electric parameters on the formation of... 相似文献
183.
Yuan-Xia Wang Ying Shi Chen-Chen Wang Jia-Hui Cheng Ying Wang Wen-Jun Shao Li-Zhi Liu 《应用聚合物科学杂志》2021,138(27):50651
Crosslinking of polyolefin elastomer (POE, ENGAGE™ 8480) with Dicumyl Peroxide (DCP) can have effects on its crystallization dynamics, crystal structure, and properties. The POE crosslinked uniformly has significantly lower crystalline ability than the one with only amorphous phase crosslinked, which, in turn, has weaker crystalline ability than neat POE. The crystallinity and melting point depend on how the POE is crosslinked. The neat POE and POE crosslinked in amorphous phase only, are investigated with DSC and in-situ tensile/synchrotron radiation (WAXD/SAXS). In situ tensile/synchrotron X-ray during a uniaxial stretching process indicates that severe crystal fragmentation is observed at a strain around 45%, and with further increase in strain. The stress in the crosslinked POE is significantly larger than neat POE. For both samples, crystal orientation increases sharply within the strain range up to 88% where orientation-induced new crystals aligned in stretching direction are observed. The long period increases more in stretching direction for the crosslinked POE, consistent with larger stress in this sample, and the stress difference is more pronounced at large strains (27.3 vs. 10.9 MPa at a strain 435%). Permanent set of the crosslinked POE is smaller, consistent with less oriented crystals observed after the test for permanent set. 相似文献
184.
Dr. Timo Broese Dr. Peter Ehlers Dr. Peter Langer Dr. Jan von Langermann 《Chembiochem : a European journal of chemical biology》2021,22(23):3314-3318
Fluoro-substituted and heteroaromatic compounds are valuable intermediates for a variety of applications in pharma- and agrochemistry and synthetic chemistry. This study investigates the chemoenzymatic preparation of chiral alcohols bearing a heteroaromatic ring with an increasing degree of fluorination in α-position. Starting from readily available picoline derivatives prochiral α-halogenated acyl moieties were introduced with excellent selectivity and 64–95 % yield. The formed carbonyl group was subsequently reduced to the corresponding alcohols using the alcohol dehydrogenase from Lactobacillus kefir, yielding an enantiomeric excess of 95–>99 % and up to 98 % yield. 相似文献
185.
Vasanthapriya R. Neelakandeswari N. Uthayarani K. Chitra M. 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(11):4272-4280
Journal of Inorganic and Organometallic Polymers and Materials - This paper reports the performance of alizarin based SnO2 dye-sensitized solar cells. A novel template assisted method has been... 相似文献
186.
Applied Composite Materials - Determining the impact behavior of adhesive joints allows the designing of high-strength joints. Therefore, the dynamic behavior of adhesive joints has recently become... 相似文献
187.
Keran Su Kim Huey Ee Jingcan Sun Shao Quan Liu Benjamin Lassabliere Ulrich Feiter Yunle Huang Rui Min Vivian Goh Aileen Pua Bin Yu 《International Journal of Food Science & Technology》2022,57(3):1666-1678
The structural diversity of polyphenols and the inherent limitations of current extraction techniques pose a challenge to extract polyphenols using a simple and green method. Hence, in this study, a method was developed to simultaneously fractionate multiple classes of polyphenols by only varying ethanol-water solutions. Honeybush tea, which is rich in polyphenols, was selected as a model for this study. Solvent extraction followed by solid-phase extraction (SPE) was developed to obtain a polyphenol-rich fraction from six honeybush samples. Based on a gradient elution programme (10%, 30%, 50%, 70% and 90% (v/v) ethanol-water solution) of SPE, the Strata X cartridge showed a better recovery of most targeted polyphenols under 0.9 mL of the drying volume and 1 mL min−1 of the dispensing speed. The elution programme for fractionating most polyphenols was as follows: single elution with 50% ethanol, followed by twice elution with 70% ethanol. The antioxidant capacity was used to analyse the differences among the polyphenol-rich fractions from six honeybush samples. Principal component analysis (PCA) revealed that unfermented C. genistoides (GG) has the greatest antioxidant capacity among the honeybush species studied. Additionally, mangiferin, isomangiferin and vicenin-2 were the main contributors to the antioxidant capacity in six honeybush fractions according to the correlation study. 相似文献
188.
189.
Yan He Kangren Kong Zhengxi Guo Weifeng Fang Zaiqiang Ma Haihua Pan Ruikang Tang Zhaoming Liu 《Advanced functional materials》2021,31(26):2101291
Sensitivity and multi-directional motivation are major two factors for developing optimized humidity-response materials, which are promising for sensing, energy production, etc. Organic functional groups are commonly used as the water sensitive units through hydrogen bond interactions with water molecules in actuators. The multi-coordination ability of inorganic ions implies that the inorganic ionic compounds are potentially superior water sensitive units. However, the particle forms of inorganic ionic compounds produced by classical nucleation limit the number of exposed ions to interact with water. Recent progress on the inorganic ionic oligomers has broken through the limitation of classical nucleation, and realized the molecular-scaled incorporation of inorganic ionic compounds into an organic matrix. Here, the incorporation of hydrophilic calcium carbonate ionic oligomers into hydrophobic poly(vinylidene fluoride) (PVDF) is demonstrated. The ultra-small calcium carbonate oligomers within a PVDF film endow it with an ultra-sensitive, reversible, and bidirectional response. The motivation ability is superior to other bidirectional humidity-actuators at present, which realizes self-motivation on an ice surface, converting the chemical potential energy of the humidity gradient from ice to kinetic energy. 相似文献
190.
Carolyn A. Grimley Stephen Funni Christopher Green Elizabeth C. Dickey 《Journal of the European Ceramic Society》2021,41(4):2807-2817
In flash sintering experiments, the thermal history of the sample is key to understanding the mechanisms underlying densification rate and final properties. By combining robust temperature measurements with current-ramp-rate control, this study examined the effects of the thermal profile on the flash sintering of yttria-stabilized zirconia, with experiments ranging from a few seconds to several hours. The final density was maximized at slower heating rates, although processes slower than a certain threshold led to grain growth. The amount of grain growth observed was comparable to a similar conventional thermal process. The bulk electrical conductivity correlated with the maximum temperature and cooling rate. The only property that exhibited behavior that could not be attributed to solely the thermal profile was the grain boundary conductivity, which was consistently higher than conventional in flash sintered samples. These results suggest that, during flash sintering, athermal electric field effects are relegated to the grain boundary. 相似文献