全文获取类型
收费全文 | 2585篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
综合类 | 4篇 |
化学工业 | 52篇 |
金属工艺 | 6篇 |
机械仪表 | 5篇 |
建筑科学 | 6篇 |
能源动力 | 6篇 |
轻工业 | 36篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 51篇 |
一般工业技术 | 48篇 |
冶金工业 | 2317篇 |
原子能技术 | 2篇 |
自动化技术 | 53篇 |
出版年
2022年 | 2篇 |
2021年 | 4篇 |
2017年 | 1篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 7篇 |
2013年 | 17篇 |
2012年 | 13篇 |
2011年 | 14篇 |
2010年 | 4篇 |
2009年 | 14篇 |
2008年 | 4篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 13篇 |
2004年 | 13篇 |
2003年 | 15篇 |
2002年 | 13篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 81篇 |
1998年 | 772篇 |
1997年 | 442篇 |
1996年 | 253篇 |
1995年 | 151篇 |
1994年 | 126篇 |
1993年 | 150篇 |
1992年 | 26篇 |
1991年 | 25篇 |
1990年 | 29篇 |
1989年 | 28篇 |
1988年 | 38篇 |
1987年 | 37篇 |
1986年 | 20篇 |
1985年 | 25篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 18篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 45篇 |
1976年 | 97篇 |
1975年 | 3篇 |
1973年 | 3篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1966年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有2591条查询结果,搜索用时 15 毫秒
971.
Imaging of chlorophyll autofluorescence by confocal microscopy in intact whole petals of Arabidopsis thaliana has been used to analyze chloroplast development and redifferentiation during petal development. Young petals dissected from unopened buds contained green chloroplasts throughout their structure, but as the upper part of the petal lamina developed and expanded, plastids lost their chlorophyll and redifferentiated into leukoplasts, resulting in a white petal blade. Normal green chloroplasts remained in the stalk of the mature petal. In epidermal cells the chloroplasts were normal and green, in stark contrast with leaf epidermal cell plastids. In addition, the majority of these chloroplasts had dumbbell shapes, typical of dividing chloroplasts, and we suggest that the rapid expansion of petal epidermal cells may be a trigger for the initiation of chloroplast division. In petals of the Arabidopsis plastid division mutant arc6, the conversion of chloroplasts into leukoplasts was unaffected in spite of the greatly enlarged size and reduced number of arc6 chloroplasts in cells in the petal base, resulting in few enlarged leukoplasts in cells from the white lamina of arc6 petals. 相似文献
972.
Immediately after birth, a full-term infant was noted to be in severe respiratory distress and died approximately five hours later, despite resuscitative efforts. Postmortem examination revealed agenesis of the trachea with a 1-mm fistula joining the esophagus and the main stem bronchi at the carina. The right kidney, ureter, Fallopian tube, and cornu of the uterus were also absent. The 25 previously reported cases of agenesis of the trachea are summarized, with special emphasis on associated abnormalities. 相似文献
973.
974.
975.
976.
977.
Respiratory activity of kidney cortex homogenates was measured after various periods of hypothermic pulsatile preservation of dog kidneys with cryoprecipitated plasma. There was a progressive loss of pyruvate plus malate-stimulated respiration (30 to 40% at 3 days and 70 to 80% at 5 days) and succinate-stimulated respiration (15 to 20% at 3 days and 50 to 60% at 5 days). Perfusion under conditions of low pO2 (30 to 40 mm Hg) or with inhibitors of the toxic effects of hyperbaric oxygen (CO2+ Mn2+) preserved homogenate respiratory activity better than with normal pO2 (150 mm Hg) or high pO2 (300 mm Hg). The results suggest that oxygen toxicity (lipid peroxidation) and the progressive loss of respiration in homogenates may be limiting factors in obtaining long-term preservation. 相似文献
978.
KA Siegel 《Canadian Metallurgical Quarterly》1976,231(3):974-978
Hydrostatic pressure was applied to a cannula inserted into Wharton's duct of adult dogs anesthetized with pentobarbital and the effect of pressure on saliva flow rate and ionic composition of saliva was measured. Increasing the back pressure on a secreting gland resulted in a decrease in flow rate. Over the range of 0-100 mmHg back pressure the decrease in flow was proportional to the applied back pressure. The potassium concentration of saliva collected in the absence of back pressure and at raised pressure was similar even though back pressure reduced flow. In contrast, sodium concentration decreased when back pressure caused salivary flow rate to be reduced. However, when examined at the same flow rates the concentration of sodium is increased when back pressure is applied to the gland as compared to absence of back pressure. Under conditions of constant stimulation the total output of sodium and potassium into saliva decreases as back pressure is increased; but when equal flow rates are compared total sodium output increases in the presence of applied back pressure, whereas potassium output remains constant. 相似文献
979.
980.