全文获取类型
收费全文 | 1458篇 |
免费 | 10篇 |
专业分类
电工技术 | 2篇 |
综合类 | 2篇 |
化学工业 | 55篇 |
金属工艺 | 3篇 |
机械仪表 | 5篇 |
建筑科学 | 28篇 |
矿业工程 | 4篇 |
能源动力 | 17篇 |
轻工业 | 33篇 |
水利工程 | 3篇 |
无线电 | 58篇 |
一般工业技术 | 58篇 |
冶金工业 | 1160篇 |
原子能技术 | 2篇 |
自动化技术 | 38篇 |
出版年
2021年 | 3篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 18篇 |
2012年 | 8篇 |
2011年 | 17篇 |
2010年 | 17篇 |
2009年 | 13篇 |
2008年 | 14篇 |
2007年 | 10篇 |
2006年 | 16篇 |
2005年 | 13篇 |
2004年 | 14篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 12篇 |
2000年 | 8篇 |
1999年 | 33篇 |
1998年 | 345篇 |
1997年 | 202篇 |
1996年 | 138篇 |
1995年 | 64篇 |
1994年 | 92篇 |
1993年 | 73篇 |
1992年 | 18篇 |
1991年 | 20篇 |
1990年 | 15篇 |
1989年 | 11篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1983年 | 8篇 |
1982年 | 13篇 |
1981年 | 16篇 |
1980年 | 20篇 |
1978年 | 5篇 |
1977年 | 37篇 |
1976年 | 60篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有1468条查询结果,搜索用时 48 毫秒
91.
Development of synthetic carbonaceous fuels and feedstocks (SCFF) is imperative if the U.S. is to maintain its world leadership. Nuclear power can provide not only the stationary thermal and electrical power backbone in the country but can also be of great assistance in supplying SCFF. All forms of carbonaceous materials can serve as sources of raw material for SCFF, however, here we consider the ultimate renewable resource of carbon which is CO2 from the atmosphere or the oceans. A number of methods for the recovery of CO2 have been examined. An absorption-stripping system utilizing dilute carbonate solvent appears most economical for atmospheric recovery while distillation appears of interest for sea-water recovery. An alternative isothermal process utilizing chlor-alkali cells is also described. Electrolytic hydrogen is thermocatalytically combined with the CO2 to form methanol which can then be dehydrated to gasoline. Production cost is dominated by the energy for hydrogen and the plant capital investment. Base loaded nuclear power plants supplying peaking load and generating SCFF in an off-peak mode is proposed for reducing costs. Under 1974/5 conditions, incremental power costs would have been a minimum. Under 1985 escalated conditions, incremental costs indicate 6 mills/kWh(e) for power which yields 33.9 c/gallon methanol or 77.1 c/gallon of equivalent gasoline which takes credit for oxygen would break even with $23/bb1 of oil. The capital investment for producing the equivalent of one million barrels/day of gasoline in 142 nuclear reactors of 100 MW(e) capacity, operating in an off-peak mode, amounts to slightly more than the investment in new oil exploration and production facilities and considerable less than the projected outflow of capital to foreign OPEC countries. The nuclear synthesis-route using atmospheric and aquatic CO2, simulates the solar photosynthetic process and provides a long-term renewable and environmentally acceptable alternate source of SCFF. 相似文献
92.
Interactions between atrial natriuretic peptide (ANP) and bradykinin (BDK) on norepinephrine (NE) uptake were demonstrated in the adrenal medulla of the rat. One hundred nM ANP and 10 nM BDK increased total NE uptake. Subthreshold concentration of ANP (1nM) or BDK (1nM) reverted the effects of thre shold concentrations of both peptides (10 nM BDK and 100 nM ANP respectively). Effective concentrations of ANP and BDK acting simultaneously did not induce additive effects on total NE uptake. Threshold concentrations of both peptides increased neuronal NE uptake only. These results suggest interactions between ANP and BDK at the neuronal uptake level. They confirm that ANP and BDK take part in the regulation of the sympathetic activity in the adrenal medulla of the rat. 相似文献
93.
94.
We report a man with a slowly progressive bulbar palsy 14 years after radiation therapy for nasopharyngeal carcinoma. Electromyography demonstrated prominent myokymic and neuromyotonic discharges in muscles innervated by the lower cranial nerves. Late effects of radiation therapy can occur in the cranial nerve musculature that are similar to well-recognized syndromes affecting the brachial plexus and spinal cord. 相似文献
95.
96.
97.
Passive immunity in neonatal calves is influenced by environment. Placing newly born Holstein calves (108 head) in three different housing environments (shade, cooled shade, hutch) during hot weather produced differences in body temperature, serum cortocosteroids, immunoglobulin IgG1 concentrations, and mortality. Experimental design permitted examination of effects due to treatments, time, differences in colostrum, and climatic environment in an analysis of variance. Calves exposed to the hotter, less desirable environment responded by having a higher mortality, higher serum corticosteroid concentration, and lower serum immunoglobulin IgG1 at 2 and 10 days after birth. All of these were correlated. Calves that died had serum immunoglobulin IgG1 falling below the mean for all experimental calves. 相似文献
98.
M. Sarikaya B. G. Steinberg G. Thomas 《Metallurgical and Materials Transactions A》1982,13(12):2227-2237
Optimization of the composition and the heat treatments to provide a microduplex structure of dislocated-autotempered lath
martensite and thin film retained austenite for good combinations of mechanical properties has been attained for Fe/Cr/C base
steels. Substituting 0.5 wt pct Mo to reduce Cr from 4 pct to 3 pct did not affect the microstructures nor the properties.
It was found that air melting as compared to vacuum melting does not cause deterioration of toughness in Mn containing alloys
but does so in Ni containing alloys. Tempered martensite embrittlement was confirmed as being due to the decomposition of
retained austenite. Further improvements in the fracture toughness are achieved by double heat treatments which provide grain
refinement. These alloys are considered to be very promising for structural applications. 相似文献
99.
100.
Human serum albumin does not decay monoexponentially although it contains a single tryptophan residue per molecule. The molecular population is thus heterogeneous with respect to the tryptophan emission. The separated monomeric and dimeric molecules of this protein, as well as various fractions isolated by the procedures of Foster and his coworkers, exhibit deviations from monoexponential decay which are comparable to those of the unfractionated protein; thus, the heterogeneity in molecular population of human serum albumin persists in the various fractions. By comparing the fluorescence decay data of this protein in the presence of thyroxine with the corresponding quenching data it was found that the fluorescence of the protein does not respond uniformly to the binding for all protein molecules. Qualitatively similar behavior was found for bovine serum albumin. In view of the above, binding studies followed by fluorescence should be viewed as averages over a heterogeneous population of the molecules of the serum albumin. 相似文献