全文获取类型
收费全文 | 5251篇 |
免费 | 33篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 21篇 |
综合类 | 9篇 |
化学工业 | 181篇 |
金属工艺 | 30篇 |
机械仪表 | 45篇 |
建筑科学 | 166篇 |
矿业工程 | 13篇 |
能源动力 | 23篇 |
轻工业 | 86篇 |
水利工程 | 20篇 |
石油天然气 | 7篇 |
武器工业 | 1篇 |
无线电 | 119篇 |
一般工业技术 | 158篇 |
冶金工业 | 4267篇 |
原子能技术 | 15篇 |
自动化技术 | 127篇 |
出版年
2021年 | 9篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 13篇 |
2017年 | 12篇 |
2016年 | 25篇 |
2015年 | 10篇 |
2014年 | 19篇 |
2013年 | 53篇 |
2012年 | 36篇 |
2011年 | 57篇 |
2010年 | 31篇 |
2009年 | 47篇 |
2008年 | 49篇 |
2007年 | 83篇 |
2006年 | 26篇 |
2005年 | 49篇 |
2004年 | 24篇 |
2003年 | 31篇 |
2002年 | 31篇 |
2001年 | 17篇 |
2000年 | 35篇 |
1999年 | 165篇 |
1998年 | 1355篇 |
1997年 | 749篇 |
1996年 | 515篇 |
1995年 | 286篇 |
1994年 | 251篇 |
1993年 | 279篇 |
1992年 | 51篇 |
1991年 | 57篇 |
1990年 | 63篇 |
1989年 | 62篇 |
1988年 | 57篇 |
1987年 | 41篇 |
1986年 | 43篇 |
1985年 | 52篇 |
1984年 | 18篇 |
1983年 | 19篇 |
1982年 | 39篇 |
1981年 | 42篇 |
1980年 | 55篇 |
1979年 | 16篇 |
1978年 | 16篇 |
1977年 | 88篇 |
1976年 | 186篇 |
1975年 | 17篇 |
1974年 | 13篇 |
1973年 | 13篇 |
1972年 | 12篇 |
排序方式: 共有5288条查询结果,搜索用时 15 毫秒
951.
CA Frazier 《Canadian Metallurgical Quarterly》1976,235(22):2410-2411
952.
133 undergraduate females responded to a pre-experimental questionnaire assessing their contraceptive use (28% on contraceptive pills), sexual experience (71% had had sexual intercourse), and present phase of menstrual cycle. Ss then read an erotic story intended to induce sexual arousal. Results of a self-report postexperimental questionnaire assessing sexual arousal and genital stimulation show no significant response differences based on menstrual cycle phases for Ss not using contraceptive pills. Greatest degree of arousal and sensation was experienced by Ss on contraceptive pills who were in the menstrual phase of the cycle; least arousal and sensation was experienced by Ss on contraceptive pills who were in the premenstrual phase of the cycle. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
953.
Correlations between alterations in hip joints, described in a post-mortem study, have established the independence of limited and progressive alterations, and in addition have shown that there is a weak association between limited alterations and osteophytes and a strong one between progressive alterations and osteophytes. Nevertheless limited alterations may rarely undergo progressive damage. Cysts relate strongly to osteophytes but only moderately with progressive alterations. Limited alterations of both head and acetabulum can be subdivided. Some implications of these findings are discussed. 相似文献
954.
H. D. Hamilton 《Journal of the American Oil Chemists' Society》1969,46(7):a344-a348
A case history of waste water disposal at the Drew Chemical, Boonton, New Jersey plant is presented together with details
of various treatments that have been studied. These include biological, chemical and physical treatment methods. Treatment
of concentrated wastes having a soluble biochemical oxygen demand of approximately 10,000 mg/liter is emphasized.
Presented at the AOCS Meeting, New York, October, 1968. 相似文献
955.
Studies on the occurrence and effects of specular reflection in midinfrared spectra of soils have shown that distortions due to specular reflection occur for both organic (humic acid) and non-organic fractions (carbonates, silica, ashed fraction of soil). The results explain why the spectra of CaCO(3) in limed soils do not match published spectra and offer an explanation as to why the presence of inorganic C interferes with the development of calibrations for organic C. These results may also have implications for the use of mid-infrared spectra for quantitative and qualitative analysis of soils. For example, libraries of spectra collected by means other than diffuse reflectance would be largely useless for comparing mineral spectra to soil spectra. To obtain the best results with forages and grains, it is necessary to develop separate calibrations for different products, but this has not seemed to be a problem for diverse sets of soil samples with C contents of 0 to 5%. Mid-infrared calibrations have also appeared to be more robust than the corresponding near-infrared calibrations in that fewer outliers are found. However, the results discussed here indicate that at least for some soil types (e. g., large differences in mineralogy or C contents), separate calibrations may be necessary. 相似文献
956.
Edward?V.?BongioEmail author Hamilton?Black Fabienne?C.?Raszewski Doreen?Edwards Caspar?J.?McConville Vasantha?R.?W.?Amarakoon 《Journal of Electroceramics》2005,14(3):193-198
Strontium-doped lanthanum ferrites (LSF) were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), 4-point D.C. electrical conductivity and bulk property measurements. The results were compared to those of previous studies as well as selected processing conditions. The investigation focused on effects of sintering temperature, time, atmosphere (air, O2 and N2) and composition of La1–xSrxFeO3– (x = 0.2–0.9), on the sintering behavior, microstructural development and electrical conductivity. An oxalate precipitation method was used to prepare lanthanum ferrite powders. Simultaneous thermogravimetric and differential thermal analysis (TGA/DTA) studies found calcination temperatures of 800 and 850^C were necessary to form single-phase crystalline powders, as determined by XRD. Specimens were sintered from 1300 to 1400^C with dwell times from
to 2 hrs. Results from SEM/EDS analysis showed the presence of a second phase in the samples fired in air or oxygen. The second phase was not detected by x-ray diffraction due to the small amount of material present. Samples fired in nitrogen had the lowest conductivity while those fired in oxygen had the highest. A composition of x = 0.5 resulted in the highest conductivity, 352 S/cm, at an operating temperature of 550C in air. High strontium additions (x = 0.9) lowered the linear shrinkage of LSF. 相似文献
957.
Barley RW Hutton C Brown MM Cusworth JE Hamilton TJ 《The Science of the total environment》2005,338(1-2):107-114
An assessment of the rate of biomass production both of the reeds in the aerobic cells and the algae in the rock filters, which form the final stage in the series of treatment cells, has been undertaken. The biomass production for the reeds was found to be highest for the lime-dosed anoxic limestone drain system, but even this was very low in comparison to values reported for natural and constructed wetlands. The algal coverage of each lagoon was relatively homogeneous, with no significant difference between the three systems studied. However, too many unknown factors suggest that further study is required. The metal uptake was higher in the roots than the stems, although no variation between cells of systems was detectable, and the difference was not as marked as reported by other workers. The metal concentrations in the debris samples were markedly higher than the roots of the reeds. The values for Fe, Al and As were several orders of magnitude larger than the influent minewater. Further study is required here, but this appears to be a key component in the function of the reeds. The lime-dosed system rock filter showed the highest Fe removal rate but the lowest Mn removal rate. Some possible mechanisms are discussed in the paper, but further investigation would be required to test these hypotheses. 相似文献
958.
The major plasma inhibitor of factor Xa is thought to be anti-thrombin III (At III). However, adsorption of plasma by aluminium hydroxide (A1(OH)3) increases its rate of neutralisation 7-8 fold, and this 'fast-acting' anti-Xa activity has been shown to be independent of At III. Gel filtration of plasma indicated that the anti-Xa activity after A1(OH)3 adsorption was located largely in the high molecular weight (greater than 200,000) fractions, which contain most of the plasma lipoproteins. Purified lipoproteins of very low-density (VLDL), low-density (LDL) and high density (HDL) were prepared by ultracentrifugation and their anti-Xa activities measured before and after adsorption by A1(OH)3. Both LDL and HDL had significant anti-Xa activities by clotting and amidolytic assays. A1(OH)3 adsorption of LDL and HDL gave a marked increase in anti-Xa clotting activity and a decrease in amidolytic activity. Incubation of the adsorbed lipoproteins with phospholipase enzymes destroyed the anti-Xa activity, and prior incubation of Factor Xa with Ca++ and phospholipid protected it against inactivation, indicating that the anti-Xa activity of the adsorbed lipoproteins is mediated via binding of Xa to phospholipid in the lipoproteins. These results indicate that lipoproteins, especially LDL and HDL, are responsible for the increased anti-Xa activity of plasma after A1(OH)3 adsorption. These lipoproteins appear to contain high affinity phospholipid binding sites for Xa which are revealed by A1(OH)3 adsorption. 相似文献
959.
960.