全文获取类型
收费全文 | 3196篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 61篇 |
金属工艺 | 2篇 |
机械仪表 | 1篇 |
建筑科学 | 1篇 |
轻工业 | 14篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 2篇 |
一般工业技术 | 17篇 |
冶金工业 | 3100篇 |
原子能技术 | 1篇 |
自动化技术 | 2篇 |
出版年
2020年 | 1篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 2篇 |
2012年 | 2篇 |
2011年 | 3篇 |
2010年 | 3篇 |
2009年 | 1篇 |
2008年 | 2篇 |
2007年 | 5篇 |
2006年 | 2篇 |
2005年 | 5篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 120篇 |
1998年 | 1012篇 |
1997年 | 597篇 |
1996年 | 375篇 |
1995年 | 179篇 |
1994年 | 187篇 |
1993年 | 183篇 |
1992年 | 23篇 |
1991年 | 13篇 |
1990年 | 19篇 |
1989年 | 24篇 |
1988年 | 28篇 |
1987年 | 19篇 |
1986年 | 16篇 |
1985年 | 17篇 |
1984年 | 1篇 |
1983年 | 6篇 |
1982年 | 21篇 |
1981年 | 17篇 |
1980年 | 22篇 |
1979年 | 1篇 |
1978年 | 7篇 |
1977年 | 86篇 |
1976年 | 160篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1965年 | 2篇 |
排序方式: 共有3204条查询结果,搜索用时 15 毫秒
161.
162.
163.
164.
MM Sheehan E Stanley GF Fitzgerald D van Sinderen 《Canadian Metallurgical Quarterly》1999,65(2):569-577
A lysis module encoded by the temperate bacteriophage phiO1205 was identified. This lysis module contains a lysin gene, designated lyt51, and two putative holin-encoding genes, designated lyt49 and lyt50. lyt51 encodes a lytic enzyme specifically directed against streptococcal cell walls. Similar to other phage-encoded lysins, Lyt51 appears to have a modular design in which the N-terminal portion corresponds to its enzymatic activity while the C-terminal region is responsible for its substrate binding specificity. The two putative holin-encoding genes, lyt49 and lyt50, located immediately upstream of lyt51, were identified on the basis of their homology to other identified holin-encoding genes. Expression of lyt49 or lyt50 in Escherichia coli was shown to cause cell death and leakage of the intracellular enzyme isocitrate dehydrogenase into the growth medium without apparent lysis of the cells. Southern blotting experiments demonstrated that at least one of the three components of the identified lysis module is present in all members of a large collection of bacteriophages, indicating that components of this lysis module are widespread among bacteriophages infecting Streptococcus thermophilus. 相似文献
165.
166.
167.
Two sensitive, spectrophotometric and atomic absorption spectrometric procedures are developed for the determination of ramipril and perindopril. Both methods are based on the formation of a ternary complex, extractable with chloroform, between copper(II), eosin and the two cited drugs. Spectrophotometrically under the optimum condition, the ternary complexes showed an absorption maximum at 535 nm, with apparent molar absorptivities of 6.55 and 4.00 x 10(3) mol(-1) x cm(-1) and Sandell's sensitivities of 5.80 x 10(-2) and 1.04 x 10(-1) microg x cm(-2) for perindopril and ramipril, respectively. The solution of ternary complex obeyed Beer's law in concentration ranges 10-60 and 20-100 microg x ml(-1) for perindopril and ramipril, respectively. The proposed method was applied to the determination of the two cited drugs in pharmaceutical tablets. The atomic absorption spectrometric method, directly through the quantitative determination of copper content of the organic extract of the complex, was also investigated for the purpose of enhancing the sensitivity of the determination. The spectrophotometric and atomic absorption spectrometric procedures hold their accuracy and precision well when applied to the determination of ramipril and perindopril dosage forms. 相似文献
168.
Infants today lose maternal measles antibody sooner than in the past. This is related to demographic changes in maternal immunization. Data for rates of decay of maternal antibody and seroconversion after measles vaccination for infants born to naturally immune (Group 1) or vaccinated (Group 2) mothers have been used to evaluate two vaccination schedules: Regime 1, measles-mumps-rubella (MMR) at 1 year of age and Regime 2, monovalent measles at 6 months followed by MMR at 15 months of age. Regime 2 costs less because MMR can be administered at 15 months with the last pentavalent booster. Months of protection/1000 children aged 0-15 months (child-months of protection) were estimated for infant populations ranging from 0 to 100% Group 1 for Regimes 1 and 2. Regime 1 provides more child-months of protection only for 100% Group 1 populations. For the study population Regime 2 provided at least 17% more child-months of protection than Regime 1. Regime 2 provides increased medical and financial benefits in proportion to the number of Group 2 infants in the population and thus is ever more advantageous for today's increasingly vaccinated populations. 相似文献
169.
Silver-ion high-performance liquid chromatographic separation and identification of conjugated linoleic acid isomers 总被引:38,自引:21,他引:17
Najibullah Sehat Martin P. Yurawecz John A. G. Roach Magdi M. Mossoba John K. G. Kramer Youh Ku 《Lipids》1998,33(2):217-221
This is the first report of the application of silverion impregnated high-performance liquid chromatography (Ag+-HPLC) to the separation of complex mixtures of conjugated linolenic acid (CLA) isomers present in commercial CLA sources
and foods and in biological specimens. This method showed a clear separation of CLA isomers into three groups related to their
trans,trans, cis,trans or trans,cis, and cis,cis configuration of the conjugated double-bound system. In addition, this method separated within each geometrical isomeric
group. Following Ag+-HPLC isolation, gas chromatography (GC)-electron impact mass spectrometry, and GC-direct deposition-Fourier transformed infrared
spectroscopy were used to confirm the identity of two major positional isomers in the cis/trans region, i.e., Δ8,10- and Δ11,13-octadecadienoic acid, which had not been chromatographically resolved previously, Furthermore,
the potential of this method was demonstrated by showing different Ag+-HPLC profiles exhibiting patterns of isomeric distributions for biological specimens from animals fed a diet containing a
commerical CLA preparation, as well as for a commerical cheese product. 相似文献
170.