全文获取类型
收费全文 | 1439篇 |
免费 | 1篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 26篇 |
化学工业 | 118篇 |
金属工艺 | 51篇 |
机械仪表 | 60篇 |
建筑科学 | 13篇 |
矿业工程 | 38篇 |
能源动力 | 2篇 |
轻工业 | 4篇 |
水利工程 | 19篇 |
石油天然气 | 53篇 |
无线电 | 68篇 |
一般工业技术 | 232篇 |
冶金工业 | 578篇 |
原子能技术 | 152篇 |
自动化技术 | 29篇 |
出版年
2021年 | 15篇 |
2019年 | 13篇 |
2018年 | 23篇 |
2017年 | 22篇 |
2016年 | 23篇 |
2015年 | 15篇 |
2014年 | 30篇 |
2013年 | 39篇 |
2012年 | 34篇 |
2011年 | 21篇 |
2010年 | 29篇 |
2009年 | 20篇 |
2008年 | 31篇 |
2007年 | 35篇 |
2006年 | 26篇 |
2005年 | 20篇 |
2004年 | 24篇 |
2003年 | 21篇 |
2002年 | 21篇 |
2001年 | 16篇 |
2000年 | 18篇 |
1999年 | 15篇 |
1998年 | 154篇 |
1997年 | 111篇 |
1996年 | 73篇 |
1995年 | 39篇 |
1994年 | 34篇 |
1993年 | 44篇 |
1992年 | 12篇 |
1990年 | 16篇 |
1989年 | 13篇 |
1988年 | 13篇 |
1986年 | 15篇 |
1985年 | 14篇 |
1984年 | 12篇 |
1983年 | 16篇 |
1982年 | 14篇 |
1981年 | 18篇 |
1980年 | 22篇 |
1979年 | 11篇 |
1978年 | 18篇 |
1977年 | 41篇 |
1976年 | 55篇 |
1975年 | 19篇 |
1974年 | 14篇 |
1973年 | 17篇 |
1972年 | 14篇 |
1970年 | 16篇 |
1968年 | 14篇 |
1966年 | 12篇 |
排序方式: 共有1443条查询结果,搜索用时 640 毫秒
1.
O. Yu. Alekseev V. S. Borisov M. V. Davidovich N. F. Popova 《Journal of Communications Technology and Electronics》2006,51(11):1240-1247
Direct and inverse problems are considered for diffraction by an open end of a rectangular waveguide (RW) with a flange that adjoins a piecewise inhomogeneous planar layered lossy medium. Also considered are similar diffraction problems for a junction of an RW and a rectangular resonator filled with a multilayer medium and a junction of two RWs, one of which contains a multilayer plate. Such open and shielded waveguide probe structures (WPSs) are used for determination and nondestructive testing of parameters of multilayer samples. The direct problem is formulated on the basis of admittance and impedance algorithms with consideration for losses existing in the medium, flange, and screens. In this case, the approximation of the given aperture field allows obtainment of explicit solutions for open and shielded WPSs in the form of integrals. Solution of the inverse problem that lies in determining thicknesses, permittivities, and permeabilities of the layers from measured values of the magnitude of the reflection coefficient is obtained by minimizing the corresponding least-squares error and by constructing artificial neural networks. In order to increase the accuracy, it is proposed to use a two-port of errors and perform measurements for several positions of the sample with respect to the flange and different impedance conditions behind the sample. 相似文献
2.
OA al-Swayeh MS al-Humayyd AA Mustafa AS al-Tuwaijri RS al-Rashed AT Ali 《Canadian Metallurgical Quarterly》1997,12(7):481-489
Recent evidence suggests that oxygen-derived free radicals are involved in mediating gastric microvascular and parenchymal cell injuries induced by ischaemia and reperfusion. Therefore, the effect of the locally acting anti-ulcer drug, sucralfate, was studied on ischaemia and reperfusion (e.g. induced gastric lesions, intraluminal bleeding, changes in vascular permeability and non-protein sulfhydryl levels in the rat stomach). Allopurinol was used as a known standard antioxidant drug. Rats were subjected to 30 min of gastric ischaemia in the presence of 100 mmol/L hydrochloric acid and reperfusion periods of 15, 30 or 60 min duration. The gastric lesions were assessed microscopically under an inverted microscope. The vascular permeability was quantified by measuring the extravasated Evans blue in the stomach. There were significantly greater numbers of gastric lesions, intraluminal bleeding and leakage of Evans blue during all reperfusion periods as compared with those of ischaemia, with maximum effects occurring at 60 min following reperfusion. Pretreatment with sucralfate (31.25-250 mg/kg, p.o.) or allopurinol (12.5-50 mg/kg, i.p.) 30 min before the procedure, dose-dependently reduced the gastric lesions, intraluminal bleeding, and decreased the vascular permeability induced by ischaemia and reperfusion. Furthermore, sucralfate dose-dependently reverses the ischaemia and reperfusion-induced depletion of mucosal non-protein sulfhydryl levels and inhibited the superoxide radical production in both cell-free xanthine-xanthine oxidase and in the stimulated polymorphonuclear cellular systems. These results suggest that the protection produced by sucralfate against gastric injury may be due to its antioxidant effects. 相似文献
3.
N. Mitchell A. Alekseev R. Gallix D. Holland R. Meyder A. Panin M. Shimada F. Wong E. Zapretelina 《Journal of Fusion Energy》1997,16(1-2):25-35
The ITER magnet system consists of structurally linked sets of toroidal (TF) and poloidal (PF) field coils, central solenoid (CS), and various support structures. The coils are superconducting, force flow Helium cooled with a Kapton-Glass-Epoxy multilayer insulation system. The stored magnetic energy is about 100GJ in the TF system and 20GJ in the PF-CS. Coils and structure are maintained at 4 K by enclosing them in a vacuum cryostat. The cryostat, comprising an outer envelope to the magnets, forms most of the second radioactivity confinement barrier. The inner primary barrier is formed by the vacuum vessel, its ports and their extensions. To keep the machine size within acceptable bounds, it is essential that the magnets are in close proximity to both of the nuclear confinement barriers. The objective of the magnet design is that, although local damage to one of the barriers may occur in very exceptional circumstances, large scale magnet structural or thermal failure leading to simultaneous breaching of both barriers is not credible. Magnet accidents fall into three categories: thermal (which includes arcing arising from insulation failure and local overheating due to discharge failure in the event of a superconductor quench), structural (which includes component mechanical failure arising from material inadequacies, design errors and exceptional force patterns arising from coil shorts or control failures), and fluid (Helium release due to cooling line failure). After a preliminary survey to select initial faults conceivable within the present design, these faults are systematically analyzed to provide an assessment of the damage potential. The results of this damage assessment together with an assessment of the reliability of the monitoring and protective systems, shows that the magnets can operate with the required safety condition. 相似文献
4.
SA Khotimchenko VM Kodentsova IA Alekseeva SG Vlaskina OA Vrzhesinskaia AA Sokol''nikov LA Kharitonchik IP Aleshko-Ozhevskií LV Sheviakova 《Canadian Metallurgical Quarterly》1997,43(3):158-164
Gamma delta T-Cells represent a minor subpopulation of T-lymphocytes in man and their role in normal and diseased human skin is unknown. This article is a comprehensive review of T-lymphocytes bearing the gamma delta T-cell receptor in normal and pathological human skin. Firstly, we have documented the occurrence of gamma delta T-cells in normal skin and in a range of reactive and malignant skin conditions. We have then discussed the experimental findings regarding the repertoire used by gamma delta T-cells in normal human skin and in cutaneous disorders with an increased percentage of gamma delta T-cells. 相似文献
5.
KhKh Sharafetdinov VA Meshcheriakova OA Plotnikova 《Canadian Metallurgical Quarterly》1998,86(3):30-33
The paper analyzes left ventricular structure-fraction relationships in the development of postinfarct aneurysm. The altered internal architectonics induces to systemic hemodynamic changes, drastically elevated intraventricular pressure. This is caused by to the dysfunction of the papillary-trabecular complex in the left ventricular cavity, which in turn. This leads to the fact that the heart work as a positive-displacement pump, by losing its capacity as a centrifugal component, by making the myocardium require additional energy expenditures, which in turn appears as varying heart failure. This investigation is of definite practical value in developing adequate correction methods for postinfarct aneurysm which can occur with the retained or formed certain ratios of cardiac structures. 相似文献
6.
AA Bakova BD Brondz OA Fedorkina VA Gusev AI Gordienko IuS Krivoshein IuL Krivorutchenko TG Prokopenko IA Popov 《Canadian Metallurgical Quarterly》1994,39(4):187-189
The possibilities of using influenza A (Leningrad) 385/80 (H3N2) virus matrix protein-specific FITC-labeled D8 monoclonal antibodies in immunofluorescence assays were investigated. The virus antigen accumulation was detected in chorioallantoic cells of chick embryos. Exhibiting the type-specific properties, the fluorescent antibodies stain the perinuclear space, cytoplasmic membrane, and granular structures in the cytoplasm of infected cells. The haemagglutination test tires in the corresponding specimens were at least 1:16. 相似文献
7.
VP Korhonen M Tolvanen JM Hyttinen M Uusi-Oukari R Sinervirta L Alhonen M Jauhiainen OA J?nne J J?nne 《Canadian Metallurgical Quarterly》1997,245(2):482-489
We have generated several transgenic mouse lines and rabbits expressing efficiently (up to 0.3 mg/ml in mice and up to 0.5 mg/ml in rabbits) human erythropoietin in their milk as bovine beta-lactoglobulin fusion protein. Human erythropoietin cDNA was inserted in frame into exon 5 of the bovine beta-lactoglobulin gene with a linker oligonucleotide encoding the cleavage site for bacterial IgA protease. RNA analysis performed on one lactating transgenic mouse and one transgenic rabbit revealed that the fusion gene was expressed almost exlusively in the mammary gland, although low amounts of transgene-derived RNA were detectable in salivary glands and uterus or in the kidney. The fusion protein was specifically cleaved with IgA protease. The erythropoietin part obtained upon digestion had a lower molecular mass than recombinant erythropoietin produced in Chinese hamster ovary cells. By deglycosylation analysis it was shown that the difference in size was due to a different type of glycosylation. Biological activity of the fusion protein, as determined by growth stimulation of TF-1 erythroleukemia cells, was less than 15% of that of human recombinant erythropoietin. Upon digestion of the fusion protein with IgA protease, biological activity comparable to that of the recombinant erythropoietin was recovered. Transgenic males and virgin females did not show signs of enhanced erythropoiesis, but lactating females expressing the transgene displayed transient increases in their hematocrit values. 相似文献
8.
II Kalachev AN Baídus' OA Ivanova EA Ganina IA Boldyrev EA Svetoch 《Canadian Metallurgical Quarterly》1997,(6):32-37
Unlike the glanders agent, the superficial structures of the melioidosis agent were demonstrated to be responsible for marked was immunosuppressive activity. Some antigenic fractions suppressing the blast transformation of lymphocytes, reducing the count of T helpers and profoundly potentiating the infection in vivo were isolated from P. pseudomallei cells. The immunogenic and immunosuppressive activities of both agents' superficial structures were studied by high performance chromatography. Antigenic complexes that were able to protect immunized laboratory animals against fatal infections and to prevent bacterial carriage due to the activation of T cells and to the bacterial activity of macrophages were identified. A composition comprising several immunogens was found to provide an additive protective action against both causative agents. Therefore, the composition may be considered to be a prototype of a molecular antipseudomonadic vaccine. 相似文献
9.
J Kongerud KI Myhre OA Hauge H Kjuus E Melbostad TB Aasen 《Canadian Metallurgical Quarterly》1996,116(6):759-763
The Norwegian Societies of Thoracic Medicine and Occupational Medicine established a working group to standardise diagnostic procedures and evaluation of work-related respiratory disorders. In cases of suspected work-related diseases the physician may be asked by the National Insurance Administration or an insurance company to make a statement which will be one of the documents used to decide the patient's right to compensation benefit. We discuss the role of the physician as an independent expert. This is different from his role as clinician. The statement should include a balanced presentation of information from different sources, including health and occupational history, and the employer's information about the work environment (quantitative and qualitative exposure data). The statement must also include the results of a clinical examination and an assessment of functional status based on objective tests. The paper contains recommendations for evaluation of permanent impairment in light of the present Norwegian laws and regulations. 相似文献
10.