全文获取类型
收费全文 | 2983篇 |
免费 | 53篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 26篇 |
综合类 | 1篇 |
化学工业 | 235篇 |
金属工艺 | 24篇 |
机械仪表 | 92篇 |
建筑科学 | 30篇 |
矿业工程 | 6篇 |
能源动力 | 33篇 |
轻工业 | 143篇 |
水利工程 | 6篇 |
石油天然气 | 14篇 |
无线电 | 73篇 |
一般工业技术 | 137篇 |
冶金工业 | 2115篇 |
原子能技术 | 8篇 |
自动化技术 | 97篇 |
出版年
2023年 | 9篇 |
2022年 | 18篇 |
2021年 | 35篇 |
2020年 | 26篇 |
2019年 | 33篇 |
2018年 | 29篇 |
2017年 | 43篇 |
2016年 | 35篇 |
2015年 | 24篇 |
2014年 | 31篇 |
2013年 | 82篇 |
2012年 | 45篇 |
2011年 | 41篇 |
2010年 | 56篇 |
2009年 | 63篇 |
2008年 | 43篇 |
2007年 | 32篇 |
2006年 | 40篇 |
2005年 | 30篇 |
2004年 | 24篇 |
2003年 | 18篇 |
2002年 | 28篇 |
2001年 | 18篇 |
2000年 | 27篇 |
1999年 | 85篇 |
1998年 | 636篇 |
1997年 | 377篇 |
1996年 | 243篇 |
1995年 | 149篇 |
1994年 | 105篇 |
1993年 | 130篇 |
1992年 | 21篇 |
1991年 | 24篇 |
1990年 | 19篇 |
1989年 | 21篇 |
1988年 | 27篇 |
1987年 | 14篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 2篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 23篇 |
1980年 | 27篇 |
1978年 | 6篇 |
1977年 | 68篇 |
1976年 | 165篇 |
1975年 | 4篇 |
1964年 | 1篇 |
1955年 | 3篇 |
排序方式: 共有3040条查询结果,搜索用时 15 毫秒
981.
During the initial phase of spaceflight, there is a translocation of fluid from the lower parts of the body to the central vascular compartment with a resultant natriuresis, diuresis, and weight loss. Whether this natriuresis and diuresis result in the attainment of a new steady state or whether the circulatory adjustment is incomplete is the subject of continuing controversy. Because water immersion is regarded as an appropriate model for studying the redistribution of fluid that occurs in weightlessness, we carried out an immersion study of relatively prolonged duration in order to characterize the temporal profile of the renal adaptation to central hypervolemia. Twelve normal male subjects underwent an immersion study of 8-h duration in the sodium-replete state. Immersion resulted in marked natriuresis and diuresis which were sustained throughout the immersion period. The failure of that natriuresis and diuresis of immersion to abate or cease despite marked extrcellular fluid volume contraction as evidenced by a mean weight loss of -2.2 +/- 0.3 kg suggests that central blood volume was not restored to normal and that some degree of central hypervolemia probably persisted. 相似文献
982.
983.
984.
985.
PM Al'perovich AG Korne?chuk VI Burlia IaI Pshuk GA Starinets 《Canadian Metallurgical Quarterly》1981,81(8):1176-1185
The effectiveness of a variety of the most popular methods used for treatment Bell's paralysis is analyzed on a great number (1168 patients) of cases. It has been found that the results of the treatment are predetermined primarily by the gravity of the facial nerve affection. No convincing dependence of the treatment effect on the disease etiology was noted, except cases of Bell's paralysis of vascular etiology, the outcome of which was worse. A less favourable outcome was also observed in patients over 60 years of age and in cases of paralysis relapses. Of the methods of treating Bell's paralysis tested by the authors it was early use of perineural injections of hydrocortisone and novocaine in combination with the traditional methods (etiotropic, resorptive, and restorative means, electrotherapy, exercises) that proved to be the most efficacious. On the basis of the follow-up study of 676 patients recommendations on the treatment of residual phenomena of Bell's paralysis and on preventing the latter's relapses are given. 相似文献
986.
AM Borkon CL McIntosh M Jones LC Lipson KM Kent AG Morrow 《Canadian Metallurgical Quarterly》1981,82(4):601-607
Reports that the hemodynamic performance of the standard orifice aortic bioprosthesis in less than optimal have prompted recommendations that mechanical prosthesis or anulus-enlarging procedures be used in adult patients with a small aortic root. The hemodynamic function of the Hancock bioprosthesis was evaluated in 77 patients who underwent cardiac catheterization of rest and with isoproterenol infusion (15 patients) an average of 6 months after operation. The average peak systolic gradient (basal conditions) was 7 mm Hg (range 0 to 37 mm Hg); 35 patients had no resting gradient. Fifteen patients received 21 mm diameter valves and had an average systolic valve gradient of 10 mm Hg (range 0 to 30 mm Hg); the average effective valve orifice area was 1.27 +/- 0.17 cm2 for 21 mm, 1.46 +/- 0.11 cm2 for 23 mm, 1.72 +/- k0.20 cm2 for 25 mm, and 1.97 +/- 0.06 for 27 mm bioprostheses. Isoproterenol infusion, elevating cardiac output 66%, increased the peak systolic gradient from an average of 11 mm Hg (range 0 to 37 mm Hg) to 44 mm Hg (range 10 to 85 mm Hg). It is concluded that small-diameter (21 and 23 mm) Hancock bioprostheses can be used with acceptable clinical and hemodynamic function in patients with a small body surface area. 相似文献
987.
A retrospective study was performed on 31 patients in whose sera an immune complex between alkaline phosphatase and immunoglobulin G had been detected. The average age of these patients was 64 years and the sexes were equally represented. Twenty-three patients (74%) had a disease with either an autoimmune aetiology or associated with circulating immune complexes or autoantibodies. Sera from 16 patients were tested for the presence of circulating immune complexes in addition to the alkaline phosphatase immune complex, and these complexes were detected in 14 cases (88%). Sera from 17 patients were tested for the presence of specific autoantibodies and these were detected in 9 cases (53%). Twelve patients were followed up for a mean period of 11.6 months (range 0.5 to 39 month). At the end of the follow-up period, 10 patients (83%) showed persistence of the immunoglobulin-G-alkaline phosphatase complex. 相似文献
988.
The regulatory properties of adenylate deaminase (EC 3.5.4.6) from Ehrlich ascites tumor cells suggest that the reaction catalyzed by this enzyme serves to protect the cell against sharp decreases in the adenylate energy charge by removing adenosine 5'-monophosphate generated when the rate of utilization of adenosine triphosphate is suddenly increased. The enzyme is effectively inhibited under normal physiological conditions of high energy charge (0.9) and 4 to 5 mM adenine nucleotide pool size. The reaction is sharply activated by a decrease in the energy charge in the physiological range (0.9 to 0.6). At low energy charge (0.6), decrease in the size of the pool causes a marked and nonlinear decrease in the rate of the deaminase reaction. This effect presumably serves to prevent excessive depletion of the adenine nucleotide pool. Calculations based on the kinetic data obtained in this study show that the AMP deaminase reaction can account for the well-established alteration of adenine nucleotide metabolism that is observed following addition of glucose or 2-deoxyglucose to intact ascites cells. 相似文献
989.
990.