全文获取类型
收费全文 | 61565篇 |
免费 | 4229篇 |
国内免费 | 1357篇 |
专业分类
电工技术 | 526篇 |
综合类 | 2965篇 |
化学工业 | 28915篇 |
金属工艺 | 1462篇 |
机械仪表 | 587篇 |
建筑科学 | 865篇 |
矿业工程 | 1156篇 |
能源动力 | 1222篇 |
轻工业 | 19557篇 |
水利工程 | 98篇 |
石油天然气 | 3444篇 |
武器工业 | 75篇 |
无线电 | 409篇 |
一般工业技术 | 2950篇 |
冶金工业 | 2100篇 |
原子能技术 | 481篇 |
自动化技术 | 339篇 |
出版年
2024年 | 287篇 |
2023年 | 789篇 |
2022年 | 1698篇 |
2021年 | 2105篇 |
2020年 | 1852篇 |
2019年 | 1807篇 |
2018年 | 1594篇 |
2017年 | 2042篇 |
2016年 | 2116篇 |
2015年 | 2091篇 |
2014年 | 3166篇 |
2013年 | 3737篇 |
2012年 | 4297篇 |
2011年 | 4425篇 |
2010年 | 3173篇 |
2009年 | 3221篇 |
2008年 | 2776篇 |
2007年 | 3658篇 |
2006年 | 3413篇 |
2005年 | 2892篇 |
2004年 | 2455篇 |
2003年 | 2134篇 |
2002年 | 1876篇 |
2001年 | 1605篇 |
2000年 | 1452篇 |
1999年 | 1267篇 |
1998年 | 1023篇 |
1997年 | 756篇 |
1996年 | 651篇 |
1995年 | 542篇 |
1994年 | 478篇 |
1993年 | 393篇 |
1992年 | 294篇 |
1991年 | 234篇 |
1990年 | 178篇 |
1989年 | 117篇 |
1988年 | 76篇 |
1987年 | 93篇 |
1986年 | 64篇 |
1985年 | 78篇 |
1984年 | 77篇 |
1983年 | 38篇 |
1982年 | 25篇 |
1981年 | 18篇 |
1980年 | 29篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Copper phthalocyanine as corrosion inhibitor for ASTM A606-4 steel in 16% hydrochloric acid 总被引:2,自引:0,他引:2
A study based on the corrosion inhibition properties of copper phthalocyanine is described. Coverage degrees of copper phthalocyanine (Cu-phcy) on ASTM-A606-4 steel, obtained by weight loss measurements, were fitted to Langmuir, Frumkin, Temkin and Flory–Huggins adsorption isotherms. A better fit to the Langmuir isotherm was obtained. The polarization curves showed that polarization of both the anodic and cathodic reactions were verified for concentrations higher than 10–4 M, indicating a mixed type action. Only the anodic reactions were polarized for lower concentrations. At high frequencies the Nyquist diagrams showed one capacitive loop attributable to double layer charging and a small one at intermediary frequencies attributable to the faradaic process of hydrogen evolution. The formation of an adsorbed film was characterized by increasing charge transfer resistance values in the low frequency range for increasing inhibitor concentrations. According to the techniques used in this study, copper phthalocyanines showed a high corrosion inhibiting efficiency for all concentrations. 相似文献
63.
本文重点讨论了硫氰酸钠湿纺腈纶设备因钝化膜缺陷和Cl-侵入而产生孔蚀的机理及环境因素对孔蚀的影响,并针对产生孔蚀的主要原因提出了防护措施。 相似文献
64.
Bhupesh C. Roy Motonobu Goto & Tsutomu Hirose 《International Journal of Food Science & Technology》1996,31(2):137-141
Tomato seed oil was extracted with supercritical carbon dioxide in a semibatch-flow extractor within the temperature range 313–343 K and the pressure range 10.8–24.5MPa. The extraction rates increased with pressure, but decreased with temperature increase because of the variation in solvent density and resultant differences in oil solubility. The fatty acid composition of the extracted oil was similar to that of soybean oil. 相似文献
65.
66.
67.
以椰油酸甲酯、单乙醇胺,P2O5等为原料制备一种新型阴离子表面活性剂-烷醇酰胺磷酸酯盐。初步探讨了工艺条件,测定了其物化性能。 相似文献
68.
马来酸及其酐和衣康酸与PP熔体接枝反应机理的研究 总被引:13,自引:0,他引:13
以马来酸酐作对照,用热分析、流变、化学分析等方法,研究了马来酸和衣康酸在非隔氧条件下与PP熔体催化接枝反应的特点和规律,阐述了单体结构-单元反应相对速率--接枝产物结构之间的关系,提出了3种接枝物的结构模型。 相似文献
69.
Thi Thi Nge Makiko Yamaguchi Naruhito Hori Akio Takemura Hirokuni Ono 《应用聚合物科学杂志》2002,83(5):1025-1035
Polyelectrolyte complex based on chitosan and acrylic acid monomer by photoinitiated free‐radical polymerization in the absence of crosslinker showed a large transition in swelling in response to changes in pH of surrounding medium. Their ability to swell arises from polyelectrolyte interactions and molecular structure of the complex. The main properties of interest that related to the molecular structure, swelling volumes, glass transition temperature, and elastic modulus of the complex were investigated. The effect of water content, the only variable in the sample component, played an important role in molecular structure of the complex and as a consequence, the extent of intermolecular linkage, especially amide bonds which in turn governed the degree of swelling of the polyelectrolyte complex in this study. The decreased degree of swelling and higher temperature shift of glass transition temperature was found with increased water content, whereas increased modulus of elasticity of dry complex was found in lower water content of synthesis component. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1025–1035, 2002 相似文献
70.
Analysis of characteristic odors from human male axillae 总被引:7,自引:0,他引:7
Xiao -nong Zeng James J. Leyden Henry J. Lawley Kiyohito Sawano Isao Nohara George Preti 《Journal of chemical ecology》1991,17(7):1469-1492
A number of studies concerning the analysis of axillary odors have assumed that the characteristic odor produced in the axillae is due to volatile steroids and isovaleric acid. Organoleptic evaluation of Chromatographic eluants from axillary extracts was employed to isolate the region in the chromatogram where the characteristic odor eluted. The odor of the dissolved eluant was eliminated when it was treated with base, suggesting that acids make up the characteristic axillary odor. Subsequent extraction of the pH-adjusted axillary extract in conjunction with organoleptic evaluation of the Chromatographic eluant, preparative gas chromatography, and analysis by GC-MS as well as GC-FTIR showed the presence of a number of C6 to C11 straight-chain, branched, and unsaturated acids as important contributors to the axillary odor. The major odor component is (E)-3-methyl-2-hexenoic acid. Three homologous series of minor components are also important odor contributors; these consist of the terminally unsaturated acids, the 2-methyl-C6 to -C10 acids and the 4-ethyl-C5 to -C11 acids. These types of acids have not been reported previously as components of the human axillary secretions and have not been proposed previously as part of the principal odor components in this area. 相似文献