全文获取类型
收费全文 | 36199篇 |
免费 | 1954篇 |
国内免费 | 34篇 |
专业分类
电工技术 | 280篇 |
综合类 | 18篇 |
化学工业 | 7500篇 |
金属工艺 | 690篇 |
机械仪表 | 775篇 |
建筑科学 | 1018篇 |
矿业工程 | 87篇 |
能源动力 | 633篇 |
轻工业 | 5853篇 |
水利工程 | 331篇 |
石油天然气 | 124篇 |
武器工业 | 5篇 |
无线电 | 1408篇 |
一般工业技术 | 6274篇 |
冶金工业 | 8001篇 |
原子能技术 | 142篇 |
自动化技术 | 5048篇 |
出版年
2024年 | 84篇 |
2023年 | 337篇 |
2022年 | 395篇 |
2021年 | 924篇 |
2020年 | 774篇 |
2019年 | 852篇 |
2018年 | 1484篇 |
2017年 | 1473篇 |
2016年 | 1538篇 |
2015年 | 1175篇 |
2014年 | 1377篇 |
2013年 | 2903篇 |
2012年 | 2100篇 |
2011年 | 1968篇 |
2010年 | 1605篇 |
2009年 | 1409篇 |
2008年 | 1348篇 |
2007年 | 1254篇 |
2006年 | 839篇 |
2005年 | 716篇 |
2004年 | 684篇 |
2003年 | 605篇 |
2002年 | 583篇 |
2001年 | 442篇 |
2000年 | 411篇 |
1999年 | 459篇 |
1998年 | 2381篇 |
1997年 | 1634篇 |
1996年 | 1043篇 |
1995年 | 633篇 |
1994年 | 495篇 |
1993年 | 577篇 |
1992年 | 217篇 |
1991年 | 220篇 |
1990年 | 161篇 |
1989年 | 166篇 |
1988年 | 168篇 |
1987年 | 149篇 |
1986年 | 131篇 |
1985年 | 161篇 |
1984年 | 149篇 |
1983年 | 113篇 |
1982年 | 146篇 |
1981年 | 163篇 |
1980年 | 168篇 |
1979年 | 94篇 |
1978年 | 90篇 |
1977年 | 292篇 |
1976年 | 640篇 |
1973年 | 81篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
EL Romano RF Monta?o B Brito R Apitz J Alonso M Romano S Gebrán A Soyano 《Canadian Metallurgical Quarterly》1997,19(1):15-36
An increasing flow of evidences collected on elementary forms of learning processes in selected animal models evidentiates some mechanisms which can represent the basic cellular principles underlying plastic changes: 1. 5HT and second messengers of nucleotide type (like cAMP) have a pivotal role in the learning process. 2. In almost all short-term learning processes the modifications are subserved by a mechanism of protein phosphorylation. 3. In various animal models the modulation of K+ and Ca2+ channels is the molecular mechanism for learning. Experiments performed in sensory T neuron of the leech indicate that the modulation of Na+/K+ electrogenic pump is one of the fundamental mechanism for learning. 4. In long-term plastic changes, the most important finding is that newly synthesized proteins are formed. 5. In addition to what has been observed in the Aplysia model, where changes in synaptic efficacy represent the basic principles of memory storage, in the leech it has been demonstrated that a molecular machinery present in a single neuron can adapt the activity of the cell to environmental stimuli. 相似文献
53.
54.
The free amino acids and peptides contents of Mahon cheese during four months of ripening were studied using high performance liquid chromatography and gel electrophoresis, respectively. The total content of free amino acids generally increased throughout the ripening period, except in one batch. Phenylalanine, valine, proline, glutamic acid and isoleucine were the most abundant free amino acids in all the tests throughout the four month period. They accounted for between 67 and 80% of the free amino acids. No difference was found between the pattern of traditionally made and industrially made Mahon cheeses. Electrophoresis of soluble nitrogen showed the main whey proteins as well as other bands corresponding to peptides. 相似文献
55.
56.
57.
MJ Castro P Morales V Fernández-Soria B Suarez MJ Recio M Alvarez M Martín-Villa A Arnaiz-Villena 《Canadian Metallurgical Quarterly》1996,43(6):327-336
The aim of this study was to determine whether bisaramil-an antiarrhythmic compound under clinical investigation-influences the reperfusion-induced arrhythmias and biochemical parameters characterizing occlusion-reperfusion-induced free-radical reactions. The left descending coronary artery (LAD) was occluded for 60 min in anaesthetized dogs followed by one hour of reperfusion. Blood samples were taken at different times of the occlusion and reperfusion for the determination of plasma concentration of malondialdehyde (MDA), reduced (GSH) and oxidized glutathione (GSSG); furthermore of the activity of catalase and superoxide dismutase (SOD). Free-radical generating capacity of polymorph neutrophil granulocytes (PMN) was also measured. At the end of the experiments heart tissue samples were excised from the injured areas and from the intact part of the left ventricular muscle. In tissues samples the concentrations of MDA and GSH and the activity of SOD were determined. Bisaramil was given as an i.v. bolus injection at a dose of 2 mg kg-1 several minutes prior to the end of LAD-occlusion; then the administration was repeated in the 30th minute of reperfusion. In the control group (10 dogs) ventricular fibrillation (VF) occurred in seven cases which resulted in death in three. In the bisaramil-treated group, however. VF was seen in three cases and no death was recorded. Bisaramil inhibited the elevation of the plasma concentration of MDA and GSSG during the reperfusion and abolished the decrease in the plasma concentration of GSH during the occlusion and reperfusion. The activity of SOD and catalase in plasma was much better preserved in the bisaramil-treated group then in the controls. Bisaramil significantly inhibited the increase of the superoxide-radical generating capacity of PMNs during the reperfusion. The data obtained from myocardial tissue samples supported the cardioprotective effect of bisaramil. The biochemical investigation of ischemic-reperfused myocardium showed that bisaramil promoted preservation of SOD-activity and of tissue glutathione. Results of this study clearly showed that bisaramil has a significant effect on ischemiareperfusion injury. Besides its inhibitory effects on ischaemia-reperfusion induced arrhythmias it has a special benefit in influencing free-radical mediated damage leading to better preservation of membranes and to limitations of irreversible cell injuries. 相似文献
58.
59.
Malacoplakia of the prostate and seminal vesicle. Ultrastructural study and review of the literature
M Sánchez Chapado J Angulo Cuesta M Guil Cid R Lera Fernández A Dehaini L Prieto Chaparro 《Canadian Metallurgical Quarterly》1995,48(8):775-778
OBJECTIVES: The present study describes a case of malacoplakia of the genitourinary tract arising in the seminal vesicle and prostate and reviews similar cases previously reported in the literature. METHOD: A 67-year-old male consulted for hemospermia and voiding symptoms. Prostatic neoplasm was suspected on the basis of the clinical and radiological findings. RESULTS: The diagnosis was made only after biopsy and histological analysis. Electron microscopy is a very useful tool. Long-term antibiotic therapy may achieve optimal results. Treatment with fluoroquinolones was successful. CONCLUSION: To avoid unwarranted radical approaches, we underscore the possibility that prostatic pseudotumors may be misinterpreted as neoplasia. Malacoplakia is diagnosed only by histology and requires medical treatment. 相似文献
60.
Ivan Cimrák 《Archives of Computational Methods in Engineering》2007,15(3):277-309
The Landau-Lifshitz (LL)equation of micromagnetism governs rich variety of the evolution of magnetization patterns in ferromagnetic
media. This is due to the complexity of physical quantities appearing in the LL equation. This complexity causes also an interesting
mathematical properties of the LL equation: nonlocal character for some quantities,nonconvex side-constraints, strongly nonlinear
terms. These effects influence also the numerical approximations. In this work, recent developments on the approximation of
weak solutions, together with the overview of well-known methods for strong solutions,are addressed.
Author is supported by the Fund for Scientific Research - Flanders FWO (Belgium). 相似文献