全文获取类型
收费全文 | 3897篇 |
免费 | 32篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 21篇 |
综合类 | 2篇 |
化学工业 | 237篇 |
金属工艺 | 56篇 |
机械仪表 | 47篇 |
建筑科学 | 78篇 |
矿业工程 | 7篇 |
能源动力 | 27篇 |
轻工业 | 122篇 |
水利工程 | 21篇 |
石油天然气 | 10篇 |
无线电 | 122篇 |
一般工业技术 | 204篇 |
冶金工业 | 2738篇 |
原子能技术 | 28篇 |
自动化技术 | 213篇 |
出版年
2021年 | 10篇 |
2020年 | 12篇 |
2019年 | 11篇 |
2018年 | 20篇 |
2017年 | 17篇 |
2016年 | 29篇 |
2015年 | 19篇 |
2014年 | 19篇 |
2013年 | 68篇 |
2012年 | 37篇 |
2011年 | 37篇 |
2010年 | 36篇 |
2009年 | 47篇 |
2008年 | 53篇 |
2007年 | 44篇 |
2006年 | 41篇 |
2005年 | 42篇 |
2004年 | 30篇 |
2003年 | 37篇 |
2002年 | 24篇 |
2001年 | 38篇 |
2000年 | 40篇 |
1999年 | 122篇 |
1998年 | 930篇 |
1997年 | 486篇 |
1996年 | 325篇 |
1995年 | 198篇 |
1994年 | 156篇 |
1993年 | 190篇 |
1992年 | 33篇 |
1991年 | 50篇 |
1990年 | 51篇 |
1989年 | 44篇 |
1988年 | 47篇 |
1987年 | 58篇 |
1986年 | 45篇 |
1985年 | 36篇 |
1984年 | 22篇 |
1983年 | 18篇 |
1982年 | 27篇 |
1981年 | 24篇 |
1980年 | 50篇 |
1979年 | 16篇 |
1978年 | 11篇 |
1977年 | 44篇 |
1976年 | 131篇 |
1975年 | 18篇 |
1974年 | 10篇 |
1973年 | 10篇 |
1971年 | 9篇 |
排序方式: 共有3933条查询结果,搜索用时 12 毫秒
71.
R.J. Clarke 《Food chemistry》1979,4(1):81-96
The author describes the particular technical features of coffee standards used commercially and/or legislatively. Existing national standards on green coffee and their harmonisation of terminology, sampling and test method are described and discussed. Comparisons are made of the various legislative standards of different countries with respect to instant coffee and their harmonisation within the EEC member countries. Roasted coffee is considered to a lesser extent as it is not an important element in the world trade for coffee. The role of various international organisations in standardisation is described. It is emphasised that the flavour of coffee is not amenable to international standardisation. 相似文献
72.
Evidence for plasmid-associated crystal toxin production in Bacillus thuringiensis subsp. israelensis 总被引:1,自引:0,他引:1
RM Faust K Abe GA Held T Iizuka LA Bulla CL Meyers 《Canadian Metallurgical Quarterly》1983,9(1):98-103
Three crystalliferous (Cry+) strains of Bacillus thuringiensis subsp. israelensis (serotype 14) that produce parasporal protein crystals toxic to dipteran larvae and several acrystalliferous (Cry-) mutants, either induced or spontaneously derived from a single Cry+ parent, were examined for the presence of covalently closed circular (CCC) DNA in attempts to correlate toxin production with the presence of a specific plasmid. The plasmid profiles of both Cry+ and Cry- variants were analyzed by both a cleared lysate- and a modified Eckhardt lysate-electrophoresis technique. All of the Cry- mutants derived from the Cry+ parental strain had lost a 4.0- to 4.4-megadalton (Mdal) plasmid. Bioassay data confirmed loss of toxin production by the Cry- variants. All three Cry+ strains, including the parent of the Cry- strains, contained CCC plasmids DNAs of the following approximate molecular weights: 4.0 to 4.4, 5.2 to 6.0, and 11.4 to 13.0 Mdal. One Cry+ strain contained an additional CCC plasmid of 6.7 to 7.2 Mdal. The plasmid patterns for several Cry- derivatives differed in other respects from the pattern for their parent strain. The various Cry+ and Cry- strains could be distinguished either by phenotypical differences in antibiotic sensitivity, crystal production, and toxicity, or by differences in their plasmid profiles. 相似文献
73.
Glow discharge treatment of soda lime glass and silica substrates prior to depositing copper films in oil-free ultra high vacuum as well as in conventional vacuum has been found to increase film adhesion suggesting that gross contamination removal is not the only effect of importance in this method of improving film adhesion. There is evidence from Auger electron emission spectroscopy for sorption of gas from the discharge into the substrate surface layers. Desorption of gases from the substrate also appears to take place. A difference in electron emission from a variety of insulating surfaces following glow discharge was observed in a scanning electron microscope, the sign of the change depending on the nature of the discharge gas. No sputtered material from system components could be detected on the substrate and there was no detectable micro-roughening nor net surface electric charge. 相似文献
74.
A "polarization mapping" method has been applied to improve the fitting quality of sum frequency generation (SFG) vibrational spectra of complicated systems and validate the data analysis of simple SFG spectra. Using such a method, two-dimensional SFG spectra can be constructed, from which more reliable spectral information can be obtained from a surface/interface. Model calculations as well as experiments have been employed to illustrate the power of the polarization mapping method for spectral analysis of SFG spectra. By using a deuterated polystyrene surface and interfacial protein molecules as examples, we demonstrate that this method is especially important for complicated molecules, such as polymers and proteins. 相似文献
75.
76.
Raymond N. Skinner Terence E. Kavanagh Graham A. Hughes Robert P. Hildebrand Brian J. Clarke 《Journal of the science of food and agriculture》1975,26(7):1037-1046
Commercial harvestings of hops (Humulus lupuhlus L, var., Pride of Ringwood) were conducted over a 5 week period encompassing normal harvest time. The effect on yield and α-acid content of the crop was determined, as was the effect on the subsequent crop. Although the yields of hops and α-acid from the first crop were found to plateau for at least 4 weeks, beginning 2 weeks prior to normal harvest, the time of harvesting exercised a significant effect on the yield for the following season. The magnitude of the effect was generally found to correlate with the length of time between training and harvesting of the initial crop, i.e. the shorter the time, the lower the yield of the subsequent crop. 相似文献
77.
CL van Limborgh 《Canadian Metallurgical Quarterly》1980,105(3):96-105
A practitioner should be aware of the most important items regarding feed and water supply that may by a factor in assessing problems on large commercial units or in fancy breeding. A breif introduction on the function of the digestive tract precedes a discussion of the main causes of nutritional disorders which are frequently lethal. The specific mechanism of recirculation (caecotrophy) causing increased vulnerability to variations in the texture of feeds is stressed. Severe intestinal malfunction is readily induced by contaminated and spoiled feed and/or drinking water. These effects are probably underestimated in comparison with specific diseases. Data on nutritional requirements are also presented to the extent to which they are relevant in this context. 相似文献
78.
Terentjev EM Hotta A Clarke SM Warner M 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2003,361(1805):653-63; discussion 663-4
The equilibrium mechanical response of nematic elastomers can be soft or hard depending on the relation between the imposed strains and the nematic director, in particular, if the local nematic director is able to respond by rotating. The dynamical response proves to be equally unusual. We examine the linear dynamic mechanical response of monodomain nematic elastomers under shear and the aspects of time-temperature superposition of the dynamical data across phase-transition regions. In the low-frequency region of the master curves, one finds a dramatic reduction of rubber plateau modulus and the rise in internal dissipation: in the shear geometries compatible with dynamic soft elasticity. Power-law variation of the storage modulus with frequency G' proportional, variant omega(a) agrees very well with the results of static stress relaxation, where each relaxation curve obeys the analogous power law G' proportional, variant t(-a) in the corresponding region of long times and temperatures. 相似文献
79.
The preparation and characterization of two triorganophosphinegold(I) complexes containing the anion derived from thiobenzoic acid are described. The cytotoxicity of these complexes has been investigated along with that of triphenylphosphinegold(I) mercaptopurinate, a known anti-tumor compound, against a variety of human cell lines. The complexes showed moderate to high cytotoxicity (ID(50) 250 - 2500 ng/ml). 相似文献
80.