全文获取类型
收费全文 | 3218篇 |
免费 | 14篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 17篇 |
综合类 | 12篇 |
化学工业 | 37篇 |
金属工艺 | 21篇 |
机械仪表 | 11篇 |
建筑科学 | 12篇 |
矿业工程 | 1篇 |
能源动力 | 5篇 |
轻工业 | 74篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
无线电 | 2篇 |
一般工业技术 | 39篇 |
冶金工业 | 2969篇 |
自动化技术 | 41篇 |
出版年
2023年 | 2篇 |
2022年 | 10篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2015年 | 11篇 |
2014年 | 6篇 |
2013年 | 44篇 |
2012年 | 23篇 |
2011年 | 16篇 |
2010年 | 14篇 |
2009年 | 21篇 |
2008年 | 14篇 |
2007年 | 11篇 |
2006年 | 6篇 |
2005年 | 9篇 |
2004年 | 4篇 |
2003年 | 10篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 98篇 |
1998年 | 930篇 |
1997年 | 563篇 |
1996年 | 349篇 |
1995年 | 170篇 |
1994年 | 143篇 |
1993年 | 206篇 |
1992年 | 25篇 |
1991年 | 12篇 |
1990年 | 21篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 18篇 |
1986年 | 18篇 |
1985年 | 20篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 20篇 |
1980年 | 26篇 |
1979年 | 2篇 |
1978年 | 11篇 |
1977年 | 94篇 |
1976年 | 208篇 |
1975年 | 7篇 |
1973年 | 2篇 |
1964年 | 1篇 |
1955年 | 4篇 |
1954年 | 1篇 |
排序方式: 共有3245条查询结果,搜索用时 15 毫秒
991.
992.
As a result of histological and ultracytochemical investigations concerning the influence of thiamine and its disulfide derivative, thiamine tetrahydrofurfuryl disulfide (TTFD), on acetylcholinesterase (AChE) in extirpated guinea pig atria, it was found that there was a clear increase in the AChE activity by 10(-4) M TTFD, a weak increase with 10(-5) M and an extremely weak increase, about the same as that in only the nutrient (Locke's solution), with 5 x 10(-4) M. However, with 10(-4) M of thiamine there was a tendency for the activity to be the same degree as with Lock's solution alone or be even inhibited at times. 相似文献
993.
AP Zav''ialov ZS Aref''eva VA Nazsrov LA Khriashcheva 《Canadian Metallurgical Quarterly》1976,16(3):381-384
Hormonal levels were tested in postweanling rats, because these had not been well established despite much testing on adult animals. Holtzman rats, 25-26 days old, that had been handled daily were decapitated at various times of the day. Radioimmunoassays were used to measure serum levels of luteinizing hormone, follicle stimulating hormone (FSH), testosterone, androstenedione, progesterone, and 20alpha dehydroprogesterone. Only FSH, testosterone, and androstenedione showed a significant variation with time. The maximal values occurred late in the dark and early in the light period. 相似文献
994.
995.
996.
The adhesion of normal mouse macrophages to glass surfaces was reduced by nontoxic levels (1-50 mug/ml) of cytochalasin B in combination with a centrifugal force (1,000-8,000 g). Macrophages nonspecifically activated by Corynebacterium acnes were also detached by this treatment, but less effectively. The effects of cytochalasin B treatment on these cells were shown to be reversible. After detachment, the cells reattached to glass, appeared morphologically normal, and behaved like untreated cells as judged by adhesion, acid phosphatase levels, and phagocytosis. The effect of cytochalasin B on several parameters of phagocytosis by normal macrophages was also examined. The results demonstrate that cytochalasin B can be used to detach macrophages from surfaces and suggest a functional relationship between phagocytosis and macrophage adhesion to surfaces. Furthermore, the effect of cytochalasin B on adhesion of phagocytic cells provides a probe for further investigation of the adhesion of cells to surfaces. 相似文献
997.
In time of food shortage, accurate assessment of nutrition status is important so that effective aid may be directed to those in greatest need and, in the future, the impact of this aid on the nutritional situation may be assessed. Using a population proportional sampling method and the index weight for height (which is relatively independent of sex, race, and age) as a criterion of nutritional status, CDC investigators determined that about 10% of the sampled population (aged about 6 months through 6 years) in Mali, Mauritania, Niger, and Upper Volta and over 20% in the sampled population in Chad were severely and acutely undernourished. Apparently younger children were affected first, but as the food shortage became more severe the prevalence of undernourished older children increased. This method of nutrition surveillance has proven itself during a stressful period and should be considered a fundamental tool when rapid assessment of acute undernutrition in children in developing nations is required. 相似文献
998.
999.
1000.
Afterload reduction therapy with nitroprusside in severe aortic regurgitation: improved cardiac performance and reduced regurgitant volume 总被引:1,自引:0,他引:1
RR Miller LA Vismara AN DeMaria AF Salel DT Mason 《Canadian Metallurgical Quarterly》1976,38(5):564-567
To assess the hemodynamic effects of afterload reduction in severe aortic regurgitation, nitroprusside was infused at cardiac catheterization in 12 patients with aortic regurgitation. Cardiac hemodynamics, angiographic variables and regurgitant volumes were quantified during control periods, and nitroprusside was infused to reduce systemic systolic pressure to 110 to 125 mm Hg. The following were reduced by the drug: systolic arterial pressure (from 154 +/- 6.4 to 115 +/- 2.3 mm Hg, P less than 0.001); left ventricular end-diastolic pressure (from 23 +/- 2.2 to 11 +/- 1.0 mm Hg, P less than 0.001); systemic vascular resistance (from 1,782 +/- 133 to 1,148 +/- 94 dynes sec cm-5, P less than 0.001); left ventricular end-diastolic volume (from 242 +/- 25 to 196 +/- 19 ml, P less than 0.001); aortic regurgitant fraction (from 0.53 +/- 0.05 to 0.44 +/- 0.06, P less than 0.01); and aortic regurgitant minute volume (from 5.5 +/- 0.10 to 4.3 +/- 0.09 liters/min, P less than 0.01). Effective cardiac index increased (from 2.49 +/- 0.19 to 3.10 +/- 0.24 liters/min per m2, P less than 0.01), and left ventricular ejection fraction rose (from 0.55 +/- 0.03 to 0.61 +/- 0.03, P less than 0.005). These data indicate that afterload reduction with nitroprusside in severe aortic regurgitation improves cardiac performance, greatly decreases left ventricular preload and reduces aortic regurgitant volume. Thus, nitroprusside therapy has special value in severe aortic regurgitation that is of particular benefit in critical clinical conditions. 相似文献