全文获取类型
收费全文 | 2177篇 |
免费 | 10篇 |
专业分类
电工技术 | 18篇 |
化学工业 | 96篇 |
金属工艺 | 6篇 |
机械仪表 | 15篇 |
建筑科学 | 20篇 |
矿业工程 | 2篇 |
能源动力 | 22篇 |
轻工业 | 105篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 74篇 |
一般工业技术 | 99篇 |
冶金工业 | 1679篇 |
原子能技术 | 5篇 |
自动化技术 | 42篇 |
出版年
2021年 | 5篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 9篇 |
2016年 | 4篇 |
2015年 | 7篇 |
2014年 | 12篇 |
2013年 | 17篇 |
2012年 | 18篇 |
2011年 | 19篇 |
2010年 | 11篇 |
2009年 | 16篇 |
2008年 | 21篇 |
2007年 | 21篇 |
2006年 | 24篇 |
2005年 | 20篇 |
2004年 | 20篇 |
2003年 | 28篇 |
2002年 | 24篇 |
2001年 | 16篇 |
2000年 | 31篇 |
1999年 | 83篇 |
1998年 | 600篇 |
1997年 | 320篇 |
1996年 | 178篇 |
1995年 | 108篇 |
1994年 | 79篇 |
1993年 | 118篇 |
1992年 | 24篇 |
1991年 | 24篇 |
1990年 | 22篇 |
1989年 | 20篇 |
1988年 | 25篇 |
1987年 | 17篇 |
1986年 | 20篇 |
1985年 | 19篇 |
1984年 | 3篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 17篇 |
1978年 | 11篇 |
1977年 | 31篇 |
1976年 | 59篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1973年 | 8篇 |
1972年 | 9篇 |
1971年 | 3篇 |
1966年 | 2篇 |
排序方式: 共有2187条查询结果,搜索用时 296 毫秒
1.
Thin Film Thermoelectric Metal–Organic Framework with High Seebeck Coefficient and Low Thermal Conductivity 下载免费PDF全文
2.
J Hibbert DC Howlett KL Greenwood LM MacDonald AJ Saunders 《Canadian Metallurgical Quarterly》1997,70(839):1191-1194
Renal vein thrombosis (RVT) is the most frequently occurring vascular condition in the new-born kidney. The predisposing factors include dehydration, sepsis, birth asphyxia, maternal diabetes, polycythaemia and the presence of an indwelling umbilical venous catheter. (RVT) may present clinically with a flank mass, haematuria, hypertension or renal failure. Many imaging modalities have been employed, but ultrasound is the technique most commonly used in the evaluation of neonates with suspected RVT. Thrombosis commences in the small renal veins and subsequently propagates via larger interlobar veins to the main renal vein and inferior vena cava (IVC). The ultrasound appearances depend upon the stage at which the examination is performed and extent of the thrombus. Initially, the interlobular and interlobar thrombus appears as highly echogenic streaks. These streaks commence in a peripheral, focal segment of the involved kidney and only persist for a few days. In the first week the affected kidney swells and becomes echogenic with prominent echopoor medullary pyramids. Later, the swelling increases and the kidney becomes heterogenous with loss of corticomedullary differentiation. Grey scale ultrasound readily demonstrates thrombus within the renal vein and IVC. Adrenal haemorrhage is a recognized association and may be identified ultrasonically. Colour Doppler scanning provides additional information. In the early stages of RVT, colour Doppler may demonstrate absent intrarenal and renal venous flow. Ultimately, the kidney may recover, show focal scarring or become atrophic. Thus, ultrasound provides an accessible and reliable tool in the assessment of suspected neonatal RVT. 相似文献
3.
The technique of high pressure is utilized to study the carrier transport behaviour in doped and undoped bulk amorphous (GeSe3·5)100−x
Bi
x
(x=0, 2, 4, 10) down to liquid nitrogen temperature to observe impurity induced modifications in amorphous semiconductors. It
is observed that pressure induced effects in lightly doped (2 at % Bi) and heavily doped (x=4, 10) semiconductors are markedly different. Results are discussed in view of the incorporation behaviour of the bismuth
impurity. 相似文献
4.
Butler Emily A.; Egloff Boris; Wlhelm Frank H.; Smith Nancy C.; Erickson Elizabeth A.; Gross James J. 《Canadian Metallurgical Quarterly》2003,3(1):48
At times, people keep their emotions from showing during social interactions. The authors' analysis suggests that such expressive suppression should disrupt communication and increase stress levels. To test this hypothesis, the authors conducted 2 studies in which unacquainted pairs of women discussed an upsetting topic. In Study 1, one member of each pair was randomly assigned to (a) suppress her emotional behavior, (b) respond naturally, or (c) cognitively reappraise in a way that reduced emotional responding. Suppression alone disrupted communication and magnified blood pressure responses in the suppressors' partners. In Study 2, suppression had a negative impact on the regulators' emotional experience and increased blood pressure in both regulators and their partners. Suppression also reduced rapport and inhibited relationship formation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
AA Gooley K Ou J Russell MR Wilkins JC Sanchez DF Hochstrasser KL Williams 《Canadian Metallurgical Quarterly》1997,18(7):1068-1072
Advances in protein database design and the software used to access the sequence data has led to progress in using protein attributes such as amino acid composition and peptide masses to identify proteins separated by two-dimensional electrophoresis. However, Edman degradation remains the principal technique for protein identification and it presents a significant bottleneck in the progress towards rapid protein identification. Simple modifications to the sequencing hardware, which automate the delivery of protein spots into the sequencer, and parallel sequencing of the protein spots represent a significant advance in the use of Edman degradation to rapidly generate the powerful protein attribute, an N-terminal sequence tag. 相似文献
6.
Paraquat (1,1'-dimethyl-4,4'-dipyridylium) is an herbicide associated with both accidental and intentional ingestion, leading to severe and often fatal toxicity. Prognosis is largely dependent on the amount of paraquat absorbed. Rapid identification of the symptoms of paraquat toxicity (burns or ulceration at the site of ingestion or injection, acute respiratory distress, and renal failure) can facilitate early treatment intervention to limit absorption. We report a case of a 71-year-old man with a suicidal ingestion of paraquat 2 days prior to presentation. Serum paraquat levels, time elapsed since ingestion, and clinical symptoms all indicated poor prognosis. The patient developed severe respiratory distress and progressive renal failure, and died 6 days after admission to the hospital. 相似文献
7.
Oncogenic avian retroviruses, such as Rous sarcoma virus (RSV) and the avian leukosis viruses, contain a strong enhancer in the U3 portion of the proviral long terminal repeat (LTR). The LTRs of a second class of avian retroviruses, the endogenous viruses (ev) lack detectable enhancer activity. By creating ev-RSV hybrid LTRs, we previously demonstrated that, despite the lack of independent enhancer activity in the ev U3 region, ev LTRs contain sequences that are able to functionally replace essential enhancer domains from the RSV enhancer. A hypothesis proposed to explain these data was that ev LTRs contain a partial enhancer that includes sequences necessary but not sufficient for enhancer activity and that these sequences were complemented by RSV enhancer domains present in the original hybrid constructs to generate a functional enhancer. Studies described in this report were designed to define sequences from both the ev and RSV LTRs required to generate this composite enhancer. This was approached by generating additional ev-RSV hybrid LTRs that exchanged defined regions between ev and RSV and by directly testing the requirement for specific motifs by site-directed mutagenesis. Results obtained demonstrate that ev enhancer sequences are present in the same relative location as upstream enhancer sequences from RSV, with which they share limited sequence similarity. In addition, a 67-bp region from the internal portion of the RSV LTR that is required to complement ev enhancer sequences was identified. Finally, data showing that CArG motifs are essential for high-level activity, a finding that has not been previously demonstrated for retroviral LTRs, are presented. 相似文献
8.
Even without electrolyte imbalance, dehydration and fever, seizures are found occasionally in the cases of mild diarrhea. Such patients have shown favorable outcome during long-term follow-up. Twenty cases (10 boys and 10 girls) of benign seizure with mild diarrhea have been diagnosed at the Pediatric Department of Cathay General Hospital from January 1987 to March 1991. Ages-of-onset ranged from 3 months to 43 months (mean 19 months). Most cases were found between December and March (16 cases, 80%). Most seizure episodes were from 2 to 5 times (10 cases, 50%); the durations of seizures were mostly within a 5-minute period (16 cases, 80%). All seizures were generalized and symmetric, including tonic-clonic (13 cases, 65%), tonic (5 cases, 25%), and clonic (2 cases, 10%). Six out of 11 cases (54.5%) showed Rotazyme (Latex agglutination) positive. After six month to four year follow up, no patient had suffered any type of epilepsy, and psychomotor development was normal in all. Further discussion of clinical features is provided. 相似文献
9.
10.
KL Hopkins PK Dickson TI Ball RR Ricketts PA O'Shea CR Abramowsky 《Canadian Metallurgical Quarterly》1997,32(10):1476-1479
Fetus-in-fetu is an unusual condition in which a vertebrate fetus is enclosed within the abdomen of another fetus. These occurrences are usually benign. This report describes an instance of malignant recurrence after resection of a fetus-in-fetu. 相似文献