全文获取类型
收费全文 | 2897篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 1篇 |
综合类 | 1篇 |
化学工业 | 77篇 |
金属工艺 | 3篇 |
机械仪表 | 17篇 |
建筑科学 | 14篇 |
矿业工程 | 1篇 |
能源动力 | 11篇 |
轻工业 | 22篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
武器工业 | 1篇 |
无线电 | 23篇 |
一般工业技术 | 58篇 |
冶金工业 | 2643篇 |
原子能技术 | 4篇 |
自动化技术 | 26篇 |
出版年
2021年 | 3篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 10篇 |
2012年 | 10篇 |
2011年 | 15篇 |
2010年 | 13篇 |
2009年 | 10篇 |
2008年 | 11篇 |
2007年 | 12篇 |
2006年 | 7篇 |
2005年 | 10篇 |
2004年 | 12篇 |
2003年 | 9篇 |
2002年 | 8篇 |
2001年 | 14篇 |
2000年 | 18篇 |
1999年 | 87篇 |
1998年 | 815篇 |
1997年 | 470篇 |
1996年 | 297篇 |
1995年 | 149篇 |
1994年 | 138篇 |
1993年 | 155篇 |
1992年 | 33篇 |
1991年 | 36篇 |
1990年 | 33篇 |
1989年 | 44篇 |
1988年 | 36篇 |
1987年 | 34篇 |
1986年 | 25篇 |
1985年 | 34篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 16篇 |
1978年 | 8篇 |
1977年 | 61篇 |
1976年 | 179篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1940年 | 1篇 |
1929年 | 1篇 |
1923年 | 1篇 |
1920年 | 1篇 |
排序方式: 共有2907条查询结果,搜索用时 15 毫秒
21.
Hemodynamic, respiratory, and regional blood flow measurements were carried out in two groups of monkeys at three roughly equivalent stages of endotoxin and hemorrhagic shock. Comparisons revealed characteristic differences at the two early stages, particularly in systemic vascular resistance and the pattern of distribution of cardiac output. However, at the final stage of shock, these patterns had merged and there were no characteristic differences between the two groups. The pathologic significance of these findings, in terms of the endotoxin theory of irreversible hemorrhagic shock and the realtive contributions of vasoactive humoral substances at various stages of the two forms of shock, is discussed. 相似文献
22.
HO Williamson PB Underwood A Kreutner JF Rogers RS Mathur HR Pratt-Thomas 《Canadian Metallurgical Quarterly》1976,126(5):579-585
Six patients with a total of nine gonadoblastomas are presented; three--and possibly a fourth--had dysgerminomatous overgrowth which was massive in two patients. Calcification detected by abdominal films was present in three sufficient for preoperative diagnosis. All patients were found to have a Y stem line on peripheral leukocyte chromosome cultures except one patient, who had a 46 XX/45 XO karyotype. She was found to have Y chromatin bodies in the germ cells of her tumor which was in a normal ovary found at exploration for an ectopic pregnancy. Three were found in virilized phenotypic females investigated for amenorrhea, and two for therapy of pelvic masses due to dysgerminomatous overgrowth. Y chromatin studies are reported on gonadal tissue. 相似文献
23.
The effects of intra-arterial infusion of E. coli endotoxin at 1.0 mg. per minute on the gastric total and mucosal blood flows, electrical potential difference, and ionic fluxes across the gastric mucosa were studied in an exteriorized, chambered preparation of canine fundic stomach. Gamma-labelled microsphere technique was used in addition to venous drainage and plasma aminopyrine clearance for the measurement of total and mucosal blood flow, respectively. In spite of normal systemic blood pressure throughout the experiment, E. coli endotoxin infusion caused a significant decrease in total gastric blood flow and in the fractional distribution of flow to the mucosae. There was no significant arteriovenous shunting of microspheres. Significant reduction in potential difference and hydrogen-ion back diffusion also was noted after endotoxin infusion, possibly as a consequence of reduced mucosal blood flow. The results indicate that significant gastric mucosal ischemia can occur and may represent a mechanism in the development of gastric erosions in endotoxemia, even in the absence of systemic hypotension. 相似文献
24.
The results of a 1974 survey of albumin measurements as performed by more than 1,300 laboratories are presented. The most widely used methods are the dye-binding technics: bromcresol green (BCG) and 2-(4'-hydroxyazobenzene) benzoic acid (HABA). These are followed by electrophoresis and salt fractionation. All methods yielded comparable albumin concentrations except electrophoresis, which manifested a consistent low bias. This close agreement is attributed, in part, to the normal-range concentration of albumin in the test specimen. Type of standardization, i.e., commercial serum, bovine serum albumin, human serum albumin, or pooled serum, did not appear to be a factor in the estimation of albumin in the normal serum submitted for analysis. Surprisingly, interlaboratory variation, from method means, was the lowest for salt fractionation and electrophoretic technics. 相似文献
25.
26.
R Jewelewicz S Khalaf RS Neuwirth RL Vande Wiele 《Canadian Metallurgical Quarterly》1976,47(6):701-705
This review comprises 36 patients who were treated for Asherman's syndrome from 1968 to 1974 at the Sloane Hospital for Women. Of the 18 patients who later conceived only 6 had uncomplicated term deliveries. Four had premature deliveries resulting in neonatal death. Three had placenta accreta and postpartum hemorrhage, necessitating a cesarean hysterectomy in 1. Two patients required cesarean section for complications due to the syndrome, 2 had spontaneous abortion, and 1 had a cervical pregnancy requiring total hysterectomy. Only 10 babies survived. The incidence and severity of complications in conceptions following treatment for Asherman's syndrome is high, and the obstetrician must be prepared to manage them. 相似文献
27.
28.
The experience of professional structural engineers with welded steel moment frame connections following the 1994 Northbridge earthquake were gathered by personal interview. This paper captures their experiences in inspecting and repairing these connections following the earthquake. The engineers interviewed represent a wide cross section of Los Angeles structural engineering firms. 相似文献
29.
As efforts are made to efficiently exploit and recover bitumen resources in Canada, increasingly more complex reservoirs in the Athabasca area continue to challenge the application of Steam‐Assisted Gravity Drainage (SAGD) technology. Several studies have been done to investigate the impact of heterogeneities/complexities such as shale barriers, lean zones, and top and bottom water on the performance of the SAGD process. However, the literature is deficient for point bar deposits with top water zones, a common occurrence in oil sands systems. This study, by using thermal reservoir simulation, examines SAGD performance in a point bar deposit reservoir where an overlying top water and an inclined heterolithic strata (IHS) is present. The results show that where the top water is unconfined and steam injection pressure is higher than that of the top water zone, there is a loss of thermal energy, but the top water does not impact steam chamber development. At steam injection pressure lower than that of the top water zone, top water continuously drains into the reservoir and constrains the size of the chamber. However, the IHS zone helps to delay drainage of the top water into the chamber when steam is injected at underbalanced conditions. Finally, under proper steam injection pressure conditions, top water production can be considerably delayed. 相似文献
30.
Ron C. Runnebaum Tarit Nimmanwudipong Ryan R. Limbo David E. Block Bruce C. Gates 《Catalysis Letters》2012,142(1):7-15