全文获取类型
收费全文 | 168432篇 |
免费 | 1324篇 |
国内免费 | 193篇 |
专业分类
电工技术 | 2553篇 |
综合类 | 119篇 |
化学工业 | 26653篇 |
金属工艺 | 9472篇 |
机械仪表 | 5715篇 |
建筑科学 | 3009篇 |
矿业工程 | 1887篇 |
能源动力 | 2706篇 |
轻工业 | 8821篇 |
水利工程 | 2729篇 |
石油天然气 | 8695篇 |
武器工业 | 12篇 |
无线电 | 14492篇 |
一般工业技术 | 38252篇 |
冶金工业 | 27805篇 |
原子能技术 | 6933篇 |
自动化技术 | 10096篇 |
出版年
2018年 | 2979篇 |
2017年 | 3092篇 |
2016年 | 3344篇 |
2015年 | 1673篇 |
2014年 | 2954篇 |
2013年 | 6340篇 |
2012年 | 4311篇 |
2011年 | 5399篇 |
2010年 | 4421篇 |
2009年 | 4895篇 |
2008年 | 4943篇 |
2007年 | 4872篇 |
2006年 | 4147篇 |
2005年 | 3821篇 |
2004年 | 3634篇 |
2003年 | 3524篇 |
2002年 | 3452篇 |
2001年 | 3464篇 |
2000年 | 3361篇 |
1999年 | 3212篇 |
1998年 | 7022篇 |
1997年 | 5149篇 |
1996年 | 3823篇 |
1995年 | 2919篇 |
1994年 | 2596篇 |
1993年 | 2720篇 |
1992年 | 2254篇 |
1991年 | 2305篇 |
1990年 | 2409篇 |
1989年 | 2316篇 |
1988年 | 2313篇 |
1987年 | 2190篇 |
1986年 | 2246篇 |
1985年 | 2295篇 |
1984年 | 2210篇 |
1983年 | 2139篇 |
1982年 | 1982篇 |
1981年 | 2195篇 |
1980年 | 2053篇 |
1979年 | 2271篇 |
1978年 | 2432篇 |
1977年 | 2431篇 |
1976年 | 3096篇 |
1975年 | 2244篇 |
1974年 | 2307篇 |
1973年 | 2342篇 |
1972年 | 2156篇 |
1971年 | 1911篇 |
1970年 | 1702篇 |
1969年 | 1632篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
G. A. Bondarenko L. A. Serovskii I. E. Vilenskaya 《Chemical and Petroleum Engineering》1992,28(5):321-325
Translated from Khimicheskoe i Neftyanoe Machinostroenie, No. 5, pp. 26–29, May, 1992. 相似文献
942.
943.
944.
G. V. Martyusha S. A. Semenov T. A. Kartasheva N. V. Zubkova I. A. Timokhin 《Chemistry and Technology of Fuels and Oils》1992,28(8):468-469
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 8, pp. 29–30, August, 1992. 相似文献
945.
946.
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
947.
The authors consider the problem of detecting visual evoked potentials (VEP's). A matched subspace filter is applied to the detection of the VEP and is demonstrated to perform better than a number of other evoked potential detectors. Unlike single-harmonic detectors, the matched subspace filter (MSF) detector is suitable for detecting multiharmonic VEP's. Moreover, the MSF is optimal in the uniformly most powerful sense for multiharmonic signals with unknown noise variance 相似文献
948.
949.
Free and bound hydrosoluble protein extracts were prepared from four anatomical areas of a multiple sclerosis (MS) cerebrum and from corresponding anatomical areas of a normal (non-MS) control. Increased levels of IgG and anti-myelin basic protein antibodies (anti-MBP) were detected in all MS samples and they were undetectable in the controls. IgG and anti-MBP from free (unbound) hydrosoluble protein extracts are defined as free IgG and free anti-MBP while IgG and anti-MBP from tissue bound protein extracts are defined as bound IgG and bound anti-MBP. IgG was purified from free protein extracts by protein G Sepharose affinity chromatography and anti-MBP was further isolated from purified IgG by antigen specific (MBP) Sepharose affinity chromatography. Free and bound anti-MBP were reacted with 20 synthetic peptides of human MBP prepared by the Fmoc method. Free anti-MBP, whether in the context of whole protein extracts, or as purified IgG or as purified antibody was completely neutralized by peptides #12, #15, #56 and #56* containing overall residues 75-106, partially neutralized by peptides #27, #16 and #21 containing overall residues 61-83 and did not react with the remaining 13 peptides. Tissue bound anti-MBP was completely neutralized only by peptides #12, #15, #56 and #56* (overall residues 75-106) and showed no reactivity towards the remaining 16 peptides including peptides #27, #16 and #21. Synthetic peptide specificity of free anti-MBP purified from MS cerebrum was identical to previously reported specificity of free anti-MBP from MS cerebrospinal fluid (CSF), while tissue bound anti-MBP, as well as bound anti-MBP from CSF had a more restricted synthetic peptide specificity than free anti-MBP. This suggests that the most likely epitope of anti-MBP is located between residues 84 and 95 of human MBP just proximal to the tri-proline sequence (99-101). 相似文献
950.
Rectal and axillary temperatures were measured simultaneously in 83 children using three different thermometer devices providing 166 pairs of results. In the first series consisting of 22 febrile children (44 measurements) and 20 afebrile children (40 measurements), the rectal mercury measurement was compared to an axillary mercury and axillary Tempa-DOT thermometer. The axillary mercury had sensitivity of 14/22 (64%) and specificity of 20/20 (100%) while the Tempa-DOT had sensitivity of 15/22 (68%) and specificity of 19/20 (95%). In the second series comprising 21 febrile children (42 measurements) and 20 afebrile children (40 measurements) the axillary mercury had sensitivity of 11/21 (52%) and specificity of 20/20 (100%) while the electronic thermometer had sensitivity of 10/21 (48%) and specificity of 20/20 (100%). Regardless of the thermometer used, the axilla is a poor alternative to rectal measurements in the diagnosis of fever. CONCLUSION: Mercury-free thermometers, when used in the axilla are as poor alternatives to rectal measurements as mercury-in-glass thermometers. 相似文献