全文获取类型
收费全文 | 6178篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 4篇 |
综合类 | 1篇 |
化学工业 | 60篇 |
金属工艺 | 7篇 |
机械仪表 | 5篇 |
建筑科学 | 18篇 |
矿业工程 | 4篇 |
能源动力 | 11篇 |
轻工业 | 50篇 |
水利工程 | 1篇 |
无线电 | 24篇 |
一般工业技术 | 31篇 |
冶金工业 | 5935篇 |
自动化技术 | 38篇 |
出版年
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 4篇 |
2014年 | 5篇 |
2013年 | 8篇 |
2012年 | 6篇 |
2011年 | 9篇 |
2010年 | 7篇 |
2009年 | 4篇 |
2008年 | 10篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 17篇 |
2004年 | 16篇 |
2003年 | 18篇 |
2002年 | 9篇 |
2001年 | 4篇 |
2000年 | 8篇 |
1999年 | 195篇 |
1998年 | 1938篇 |
1997年 | 1115篇 |
1996年 | 716篇 |
1995年 | 391篇 |
1994年 | 284篇 |
1993年 | 366篇 |
1992年 | 48篇 |
1991年 | 46篇 |
1990年 | 56篇 |
1989年 | 52篇 |
1988年 | 44篇 |
1987年 | 44篇 |
1986年 | 40篇 |
1985年 | 49篇 |
1984年 | 3篇 |
1983年 | 10篇 |
1982年 | 21篇 |
1981年 | 40篇 |
1980年 | 54篇 |
1979年 | 5篇 |
1978年 | 15篇 |
1977年 | 137篇 |
1976年 | 304篇 |
1975年 | 14篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1955年 | 4篇 |
排序方式: 共有6189条查询结果,搜索用时 578 毫秒
961.
A 7-year-old girl twice developed severe hypernatremia (serum sodium values up to 194 mEq/l) without obvious cause. The ability of her kidneys to conserve water was normal, and increasing her plasma osmolality stimulated an appropriate ADH response. Unable to excrete a water load, her kidneys continued to conserve water even with a serum sodium concentration of 133 mEq/l. She was never thirsty and did not ingest sufficient fluid by choice. Although there was no demonstrable anatomic lesion, we postulate a localized defect of her thirst center. This may have modified release of ADH and resulted in an inability to dilute the urine by interrupting a pathway that could exist from the thirst center to the supraoptic nuclei. A therapeutic regimen based on these studies has prevented further hypernatremia. 相似文献
962.
Frank R. Jorgensen 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1977,27(1):303-308
Sodium and potassium silicate glass was continuously dissolved in a tower dissolver operated at atmospheric pressure. In pilot experiments the rate, controlled by the dissolution process occurring at the glass/liquor interface, was dependent on surface area, temperature, type, and chemical composition of the glass, but was independent of concentration and flowrate. Activation energies for the dissolution process lay in the range 22-48 kJ/mol, while typical rates of dissolution were 26 and 21 kg m?3 h?1 for 2.0 and 3.2 SiO2/Na2O weight ratio sodium silicate glass at 99°C. The corresponding rate for potassium silicate glass of SiO2/K2O weight ratio 2.0was 195 kgm?3h?1 at 80°C. Loss of potassium silicate due to the formation of insoluble compounds was prevented by operating below 93°C. Tower dissolvers warrant further consideration as an alternative to conventional digestors, having the advantages of continuous operation and uniform product density. 相似文献
963.
964.
PS Weisner GR Bower LA Dollimore AM Forster B Higley AE Storey 《Canadian Metallurgical Quarterly》1993,20(8):661-666
Technetium-99m exametazime (99mTc-d,l-HMPAO), prepared by the reconstitution of the Ceretec kit, is widely used in the investigation of regional cerebral blood flow. The radiochemical purity specification of not less than 80% lipophilic complex requires that the kit is used within 30 min of reconstitution. In certain circumstances this imposes restrictions on its clinical availability. A number of approaches to extending the 30-min shelf life have been proposed and these are discussed. A method of stabilising the kit by the addition of 200 micrograms cobalt chloride hexahydrate (CoCl2 x 6H2O) in 2 ml of water is described. The addition of this solution can extend the shelf life of the reconstituted kit to at least 5 h post reconstitution. 相似文献
965.
AM Campbell 《Canadian Metallurgical Quarterly》1993,135(1-2):147-151
The present status of some general questions about DNA recombination is assessed. Topics include the mechanisms of synapsis and strand exchange, and the functions of recombination in nature. 相似文献
966.
ME Cohen-Solal AM Graulet MA Denne J Gueris D Baylink MC de Vernejoul 《Canadian Metallurgical Quarterly》1993,77(6):1648-1653
Increased bone resorption is a mechanism contributing to bone loss in the postmenopausal period. Cytokines are involved in osteoclastic differentiation and, therefore, may play a role in the regulation of bone resorption. Several previous works showed the implication of interleukin-1 (IL-1), IL-6, and tumor necrosis factor-alpha (TNF alpha) in the modulation of bone remodeling. This study determines the concomitant production of the three cytokines and tests the bone-resorbing activity of peripheral monocyte supernatants. Four groups of women were studied: premenopausal women (n = 13; mean age, 47 +/- 0.9 yr), untreated postmenopausal women (n = 21; mean age, 52 +/- 0.6 yr), postmenopausal women treated with estrogens (n = 14; mean age, 54.2 +/- 1.1 yr), or postmenopausal women treated with ethanehydroxydiphosphonate (n = 12; mean age, 53.2 +/- 2 yr). Assignment to clinical groups was verified by plasma FSH and estradiol determinations. Lumbar spine bone mineral density was significantly higher in the premenopausal women group than in the three postmenopausal groups. Peripheral blood monocytes were cultured for 48 h with 20% autologous plasma, and after stimulation with lipopolysaccharides. IL-1, IL-6, and TNF alpha levels were measured by RIA in the monocyte surpernatants. The three cytokines were highly correlated to each other, IL-1 with IL-6 (r = 0.76; P < 0.001), IL-1 with TNF alpha (r = 0.89; P < 0.001), and IL-6 with TNF alpha (r = 0.89; P < 0.001). The mean levels of the three cytokines could not be compared because of the variations in the values. However, a trend toward lower levels in the three cytokines was noted in estrogen-treated women compared to the untreated postmenopausals. The bone-resorbing activity of monocyte supernatants, assessed by fetal long bone-resorbing assay, increased in untreated postmenopausal compared to that in premenopausal women (1.22 +/- 0.08 vs. 0.87 +/- 0.11; P < 0.05). In estrogen-treated patients, this activity decreased to premenopausal levels (0.89 +/- 0.04 vs. 0.87 +/- 0.11; P = NS). The resorbing activity was correlated to IL-1 (r = 0.28; P = 0.03), IL-6 (r = 0.52; P < 0.01), and TNF alpha (r = 0.48; P < 0.01). The addition of cytokine inhibitors and IL-1 receptor antagonist and TNF alpha antibodies to the supernatant bone culture medium induced a significant decrease in the calcium release. Those data show the involvement of several cytokines in the bone resorption process after estrogen deficiency. 相似文献
967.
968.
969.
970.
DP Stoker ML Perl G Abrams AR Baden T Barklow BA Barnett AM Boyarski J Boyer PR Burchat F Butler JM Dorfan GJ Feldman G Gidal G Hanson BD Harral K Hayes D Herrup JE Hylen WR Innes JA Jaros JA Kadyk D Karlen SR Klein AJ Lankford BW LeClaire M Levi V Lüth JA Matthews RA Ong K Riles PC Rowson DR Wood 《Canadian Metallurgical Quarterly》1989,39(7):1811-1824