全文获取类型
收费全文 | 8693篇 |
免费 | 682篇 |
国内免费 | 42篇 |
专业分类
电工技术 | 180篇 |
综合类 | 67篇 |
化学工业 | 2185篇 |
金属工艺 | 249篇 |
机械仪表 | 294篇 |
建筑科学 | 256篇 |
矿业工程 | 36篇 |
能源动力 | 385篇 |
轻工业 | 1650篇 |
水利工程 | 97篇 |
石油天然气 | 67篇 |
无线电 | 583篇 |
一般工业技术 | 1382篇 |
冶金工业 | 844篇 |
原子能技术 | 65篇 |
自动化技术 | 1077篇 |
出版年
2024年 | 33篇 |
2023年 | 105篇 |
2022年 | 257篇 |
2021年 | 444篇 |
2020年 | 301篇 |
2019年 | 353篇 |
2018年 | 392篇 |
2017年 | 412篇 |
2016年 | 377篇 |
2015年 | 263篇 |
2014年 | 373篇 |
2013年 | 665篇 |
2012年 | 524篇 |
2011年 | 593篇 |
2010年 | 415篇 |
2009年 | 459篇 |
2008年 | 385篇 |
2007年 | 326篇 |
2006年 | 283篇 |
2005年 | 185篇 |
2004年 | 199篇 |
2003年 | 240篇 |
2002年 | 248篇 |
2001年 | 194篇 |
2000年 | 135篇 |
1999年 | 116篇 |
1998年 | 246篇 |
1997年 | 189篇 |
1996年 | 145篇 |
1995年 | 90篇 |
1994年 | 66篇 |
1993年 | 72篇 |
1992年 | 37篇 |
1991年 | 30篇 |
1990年 | 37篇 |
1989年 | 21篇 |
1988年 | 34篇 |
1987年 | 15篇 |
1986年 | 21篇 |
1985年 | 17篇 |
1984年 | 9篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 28篇 |
1975年 | 8篇 |
1974年 | 7篇 |
排序方式: 共有9417条查询结果,搜索用时 15 毫秒
991.
The separation of phospholipid classes from human heart was achieved in two steps by high performance liquid chromatography
(HPLC) using a silica column with an ultraviolet spectromonitor at 206 nm. A complete partitioning of phosphatidylcholines
(PC), phosphatidylethanolamines (PE), phosphatidylinositols (PI), phosphatidylserines (PS), cardiolipins (CL), lysophosphatidylcholines
(LPC) and sphingomyelins (Sph) was obtained for further analysis. 相似文献
992.
Martin Me Court Eric Imbert Pascale Vincensini-fort Jérôme Mars Hervé Ribot Dominique Persegol Thierry Jacquemin Josette Toussan-berger Denis Trystram José Camargo da Costa Mahmoud Helal Atman Guerchaoui Noureddine Mhaya Ignacio Jesus Ania de Briseno Chien Nguyen Duc Laurent Chety 《电信纪事》1989,44(3-4):194-197
993.
JA Oliveira Filho AC Silva E Lira Filho B Luna Filho SH Covre FA Lauro MA Danucalov WA Leite S Tuffik JL Andrade AA de Paola E Martinez Filho 《Canadian Metallurgical Quarterly》1997,69(6):385-388
Nineteen children with congenital upper alimentary tract malformation were studied prospectively at the Department of Paediatrics, University College Hospital (UCH), Ibadan, over a period of 12 months. There were 20 cases, grouped into six types comprising congenital hypertrophic pyloric stenosis, seven; cleft lip and/or cleft palate, five; oesophagal atresia with or without tracheo-oesophageal fistula, four; jejunal atresia two and a case each of achalasia and annular pancreas. One patient had oesophageal atresia and congenital hypertrophic pyloric stenosis. The mortality rate was 31.51% (six out of nineteen). Low mortality was recorded in cases of cleft lip and/or palate, while mortalities of over 70% were recorded among cases of jejunal atresia, and oesophageal atresia with or without tracheo-oesophageal fistul. The common causes of death were milk feed aspiration (28.6%-two cases), purulent peritonitis (14.3%-one case), and probable septicaemia (14.3%-one case). The cause of death in two cases could not be determined. 相似文献
994.
Cleiton C. Silva Joo Paulo S.E. Machado Ana V.C. Sobral-Santiago Hosiberto B. de Sant'Ana Jesualdo P. Farias 《Journal of Petroleum Science and Engineering》2007,59(3-4):219-225
The aim of this study was to evaluate the effect of welding on the corrosion resistance of the heat-affected zone (HAZ) of the AISI 444 ferritic stainless steel in medium containing Venezuelan heavy oil. AISI 444 steel plates were welded through the use of three levels of welding heat input (4, 6 and 8 kJ/cm). Samples were extracted from the welded plates and thermally treated in three different temperatures (200, 300 e 400 °C), while immerged in petroleum for a period of 4 h. Optical microscopy (OM), scanning electronic microscopy (SEM) and energy dispersive X-ray analysis (EDX) techniques were used for the analysis of the surface and transversal section of the joint. Electrochemical trials of cyclic potentiokinetic reactivation of double loop (EPR-DL) were also carried out. It has been concluded that the temperature of treatment has direct influence on the level of material corrosion and that the increase in the welding heat input contributes to a higher level of corrosion. 相似文献
995.
996.
Helder Fleury Pinheiro Attílio José Giarola Carlos Leônidas da Silva Souza Sobrinho 《Journal of Infrared, Millimeter and Terahertz Waves》1995,16(11):1965-1975
The formulation is developed in the frequency domain and the finite difference method is used for the numerical solution of the scalar wave equation, written in terms of the transverse components of the magnetic field. As a result a conventional eigenvalue problem is obtained without the presence of spurious modes due to the implicit inclusion of the divergence of the magnetic field equal to zero. The formulation is developed to include biaxial anisotropic dielectrics with an index profile varying arbitrarily in the cross section of the waveguide under analysis. This formulation is then applied to the analysis of the influence on the dispersion characteristics of the dimensions of asymmetric coupled rectangular uniaxial anisotropic dielectric waveguides. As expected, the reduction of the height or the width of one of the rectangular dielectric waveguides causes the dispersion curves to move towards higher frequencies. 相似文献
997.
VB de Carvalho EF Sousa JH Vila JP da Silva MR Caiado SR Araujo R Macruz EJ Zerbini 《Canadian Metallurgical Quarterly》1996,94(8):1815-1817
BACKGROUND: Heart transplantation (HT) as a therapeutic option for end-stage chronic Chagas' heart disease (CCHD) is controversial. Reactivation of Trypanosoma cruzi infection and recurrence of the disease in the allograft are likely to occur. Furthermore, active myocarditis has been reported to predispose patients to an increased incidence and severity of rejection. METHODS AND RESULTS: We prospectively investigated the long-term follow-up of 10 patients with CCHD who underwent HT. Immunosuppression was based on cyclosporine A and azathioprine. T cruzi reactivation was prevented with benzonidazole. Besides allograft rejection surveillance, T cruzi infection was monitored through blood tests, myocardial biopsies, and serological tests. Over a mean follow-up period of 34 +/- 38 months (range, 73 to 124 months), 7 patients are alive and in NYHA functional class I. Life expectancy was 78% for the second year and 65% for 10 years. Rejection was less frequent in chagasic than in age- and sex-matched control patients (mean +/- SD, 1.60 +/- 1.26 versus 5.70 +/- 1.89 episodes per patient, respectively; P = .0001); decreased severity of rejection was also observed (P = .006). T cruzi parasitemias detected on three occasions were successfully treated with benzonidazole. There were no signs of recurrence of the disease in the allograft. CONCLUSIONS: These results suggest an important role of HT in the treatment of CCHD. There was a low frequency of T cruzi infection reactivation and no signs of recurrence of the disease in the allograft. The surprisingly decreased rejection incidence and severity require further studies for elucidation. 相似文献
998.
Two cases of eumycotic mycetomas in the head and neck region are reported. The first case is the localized mycetoma which involved only the soft tissue of the neck. It was completely excised and the patient needed no further treatment. In the second case, the lesion extensively involved the structures in the parapharyngeal space, submandibular space and carotid sheath. The upper limit is the skull base. The patient was treated by combination of wide excision with radial forearm flap and antifungal agents, however, the prognosis is fair. 相似文献
999.
1000.