全文获取类型
收费全文 | 11617篇 |
免费 | 19篇 |
专业分类
电工技术 | 15篇 |
综合类 | 2篇 |
化学工业 | 234篇 |
金属工艺 | 22篇 |
机械仪表 | 17篇 |
建筑科学 | 29篇 |
能源动力 | 16篇 |
轻工业 | 142篇 |
水利工程 | 7篇 |
石油天然气 | 6篇 |
无线电 | 111篇 |
一般工业技术 | 125篇 |
冶金工业 | 10724篇 |
原子能技术 | 32篇 |
自动化技术 | 154篇 |
出版年
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 10篇 |
2017年 | 8篇 |
2016年 | 19篇 |
2014年 | 26篇 |
2013年 | 46篇 |
2012年 | 23篇 |
2011年 | 35篇 |
2010年 | 38篇 |
2009年 | 43篇 |
2008年 | 41篇 |
2007年 | 43篇 |
2006年 | 47篇 |
2005年 | 38篇 |
2004年 | 33篇 |
2003年 | 39篇 |
2002年 | 23篇 |
2001年 | 28篇 |
2000年 | 28篇 |
1999年 | 325篇 |
1998年 | 3444篇 |
1997年 | 2018篇 |
1996年 | 1231篇 |
1995年 | 702篇 |
1994年 | 566篇 |
1993年 | 663篇 |
1992年 | 79篇 |
1991年 | 149篇 |
1990年 | 125篇 |
1989年 | 141篇 |
1988年 | 146篇 |
1987年 | 117篇 |
1986年 | 98篇 |
1985年 | 77篇 |
1984年 | 22篇 |
1983年 | 18篇 |
1982年 | 65篇 |
1981年 | 66篇 |
1980年 | 86篇 |
1979年 | 18篇 |
1978年 | 29篇 |
1977年 | 219篇 |
1976年 | 482篇 |
1975年 | 22篇 |
1974年 | 13篇 |
1973年 | 9篇 |
1972年 | 9篇 |
1970年 | 8篇 |
1955年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 61 毫秒
91.
J R?sch CT Dotter AJ Seaman JM Porter HH Common 《Canadian Metallurgical Quarterly》1976,127(4):553-558
Sequential ascending venographic studies were used to assess the healing of deep venous thrombosis in 50 patients randomly assigned to streptokinase or heparin therapy. Various degrees of thrombolysis and/or recanalization were demonstrated by venograms performed on the fourth and tenth days of treatment. Late follow-up studies (mean, 7 months after treatment) showed three basic patterns of resolution: (1) return to normal, (2) complete recanalization, and (3) incomplete recanalization and/or collateralization. Loss of valves or their function was associated with recanalization. The character, speed, and outcome of healing reflected the nature and extent of thrombosis, prior thrombotic disease in the extremity, and the type and timing of treatment. Streptokinase was highly effective and preferable to heparin in patients with deep vein thrombosis when therapy was begun within 4 days of onset of symptoms. In later stages of acute or recurrent deep vein thrombosis, the effectiveness of both drugs was significantly reduced. 相似文献
92.
93.
It is well-known that in the chick, dietary protein increases the levels of several hepatic enzymes that are involved in nitrogen metabolism and excretion. However, the biochemical mechanism of this response is essentially unknown. The experiments presented in this paper show that the chick is responding to alpha-amino nitrogen and not to any specific amino acid. Furthermore, it is shown that this system responds to endogenous sources of nitrogen as well as dietary protein and that the xanthine dehydrogenase response involves regulation of enzyme synthesis without changing the rate of degradation. 相似文献
94.
From a necropsy series of 14 kidneys, it is very easy to prove, that there is a quite good correlation between the theorical calculated volume of the kidney and its real volume. It is possible to compare the kidney to an ovoid, and to calculate its volume, knowing the 3 dimensions which are its length, its width, its depth. In this way, by echotomography it is possible to estimate these three parameters at the level of the transplanted and to calculate the volume and if, after two successive examinations of control, the kidney volume is found to be enlarged (over 20%) a reject phenomenon must be diagnozed. 相似文献
95.
96.
A Navarro Izquierdo C San Roman Terán JM Pereda García 《Canadian Metallurgical Quarterly》1976,141(1):33-37
This study reports the results of analysis concerning some chemical characteristics of 63 samples of tomato juice and paste. Copper was determined by atomic absorption spectrometry and its average content was 32 ppm. This is not a critical value for human health and results below the upper limit provided by law of several european and not european countries. 相似文献
97.
Over a ten-year period, 129 patients with idiopathic pelviureteric obstruction were randomly selected for splinted or unsplinted pyeloplasties. Of these groups, the patients with splinted pyeloplasties had a lower incidence of postoperative complications. The long-term results were similar in both groups. 相似文献
98.
CJ Vecht TC van Woerkom AW Teelken JM Minderhoud 《Canadian Metallurgical Quarterly》1976,34(1-4):11-21
In head injured patients changes were found in the CSF levels of metabolites of the dopaminergic and the serotonergic neurotransmission (HVA and 5-HIAA). After the fifth day following trauma a significant decrease of the HVA levels in the lumbar CSF after probenecid treatment was found. The intensity of this decrease was found to be related to the severity of the trauma (period of unconsciousness), but not to the state of consciousness. Also the probenecid-induced 5-HIAA levels in conscious patients were decreased after the fifth post-traumatic day. In unconscious patients, the period of unconsciousness, particularly in the period of 5-20 days after trauma. Between 21 and 60 days after trauma the 5-HIAA concentrations in unconscious patients decreased remarkably, but they were still significantly higher than in the conscious patients. It can be concluded that during unconsciousness serotonergic neurons have a high rate of turnover, but that both neurotransmitter systems are damaged by the direct or indirect consequences of the injury. 相似文献
99.
A case of primary retroperitoneal germinoma is presented in which markedly elevated serum lactic dehydrogenase levels were present before diagnosis, but declined to normal with abdominal irradiation. It is the first report of lactic dehydrogenase serving as a tumor marker in germinoma. 相似文献
100.