首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1663篇
  免费   7篇
  国内免费   1篇
电工技术   7篇
化学工业   51篇
金属工艺   8篇
机械仪表   10篇
建筑科学   37篇
矿业工程   3篇
能源动力   8篇
轻工业   26篇
水利工程   7篇
石油天然气   1篇
无线电   20篇
一般工业技术   48篇
冶金工业   1416篇
原子能技术   6篇
自动化技术   23篇
  2021年   3篇
  2020年   3篇
  2019年   2篇
  2018年   4篇
  2017年   4篇
  2016年   5篇
  2014年   4篇
  2013年   9篇
  2012年   11篇
  2011年   15篇
  2010年   7篇
  2009年   13篇
  2008年   7篇
  2007年   5篇
  2006年   18篇
  2005年   15篇
  2004年   6篇
  2003年   18篇
  2002年   15篇
  2001年   7篇
  2000年   10篇
  1999年   54篇
  1998年   391篇
  1997年   221篇
  1996年   157篇
  1995年   86篇
  1994年   78篇
  1993年   87篇
  1992年   14篇
  1991年   24篇
  1990年   23篇
  1989年   26篇
  1988年   24篇
  1987年   31篇
  1986年   21篇
  1985年   17篇
  1984年   7篇
  1983年   4篇
  1982年   15篇
  1981年   12篇
  1980年   27篇
  1979年   9篇
  1978年   9篇
  1977年   27篇
  1976年   108篇
  1975年   4篇
  1973年   2篇
  1967年   4篇
  1966年   1篇
  1955年   2篇
排序方式: 共有1671条查询结果,搜索用时 15 毫秒
991.
To define mechanisms involved in the transport of immunoglobulins into intestinal fluids, we localized IgM, IgA, IgG, and secretory component (SC) in human intestinal mucosa by the peroxidase-labeled antibody technique. At the light microscopic level, immunocytes containing IgA, IgM, or IgG were found in the lamina propria. IgA, IgM, and SC were prominent in the epithelium of gland crypts; IgG was limited to a few cells at tips of villi. At the electron-microscopic level, SC was localized to perinuclear spaces, endoplasmic reticulum, saccules associated with Golgi complexes, cytoplasmic vesicles, and lateral and basal plasma membranes of columnar epithelial cells. IgA and IgM, but not IgG, also were localized to plasma membranes and cytoplasmic vesicles of these cells. Neither the immunoglobulins nor SC was found within other types of epithelial cells (Paneth, goblet, endocrine). The findings provide evidence that (1) the site of SC synthesis in intestinal epithelium is secretory columnar cells, principally those in gland crypts; (2) the polymeric immunoglobulins IgM and IgA are translocated through such SC-containing cells by a process that involves formation of cytoplasmic vesicles; (3) IgM and IgA could combine with SC during transcellular transport (likely sites are lateral or basal plasma membranes or supranuclear cytoplasm); (4) the monomeric immunoglobulin IgG does not share the transepithelial cell route involved in IgM and IgA transport.  相似文献   
992.
Analysis of partial discharge signal using the Hilbert-Huang transform   总被引:1,自引:0,他引:1  
/sup T/he development of time-frequency and time-scale transforms has progressed rapidly over the last 20 years. The development and progression of numerical acquisition enable the utilization of these mathematical tools to analyze partial discharge in electrical equipment. This paper introduces a new transform, a Hilbert-Huang Transform to analyze partial discharge data. The mathematical model of a Hilbert-Huang Transform is described; and its application in a PD application shows its great advantage.  相似文献   
993.
994.
Central nervous system aspergillosis in two young adults   总被引:1,自引:0,他引:1  
Unusual and unique features were present in the cases of two patients with central nervous system aspergillosis: One had a previously unreported complication of aspergillosis, extracranial internal carotid artery thrombosis documented by angiography, and in the other patient, cerebral granulomas developed from Aspergillus fumigatus in association with intravenous narcotic abuse. The latter etiologic mechanism was suggested once before. Neither of these patients showed other underlying disease. A detailed neuropathologic examination correlated the salient clinical findings with formation of aspergillosis cerebral granulomata, basilar meningitis, and arterial occlusion. Diagnostic and therapeutic methods in this disease are limited.  相似文献   
995.
Seventy-five patients underwent a 90 percent distal gastric bypass for morbid obesity. The average weight was 121.4 kilogram, height 164 centimeters, and age 31.4 years in these 70 women and five men. There was a total of 20 surgical complications in the 75 patients, with wound infection being the most common. Sixteen chronic complications were noted and consisted of vomiting, diarrhea, reflux esophagitis, dysphagia, and vitamin deficiencies. None of the above complications were life-threatening or required dismantling of the bypass. Of 54 patients followed for 12 months or more after gastric bypass, there was a 24.5 percent average weight decrease at 6 months, and this progressed to 35.8 percent by 12 months. Fifty-two patients undergoing small bowel bypass previously at the same institution had a 25.4 percent weight reduction at 12 months. Of 54 patients, 83 percent followed for one or more years after gastric bypass have had an excellent or good clinical result, whereas only 42 percent of the 52 patients undergoing small bowel bypass have had an excellent or good clinical result with the same criteria. It is concluded that the Mason 90 percent distal gastric bypass is a suitable form of surgical treatment for the morbidity obese patient who cannot lose weight by dietary measures.  相似文献   
996.
997.
Plasma prostaglandin F (PGF) was measured by a radioimmunoassay method in 24 subjects with tumours of the female genital tract. Levels in the tumour group ranged from 25 pg/ml to 134 pg/ml and were almost all greater than the values observed in a control group of 41 healthy women who had a mean (+/-SD) level of 21 (+/-3.4)pg/ml. There was a relationship between plasma PGF levels and the stage of the disease. Patients with resectable tumours showed a fall in PGF levels postoperatively and those with disseminated malignancy demonstrated increasing levels as the disease progressed. Plasma PGF may provide a clinical prognostic marker in the management of patients with malignant tumours.  相似文献   
998.
999.
1000.
B.L. Farmer  R.K. Eby 《Polymer》1981,22(11):1487-1495
Energy analysis is used to determine the low energy crystal structure for polytetrafluoroethylene molecules in the 136 and 5425 conformations. The structure for the 5425 conformation contains an ordered repeating pattern of a left- and right-handed pair of molecules in a unit cell having projected parameters, a′, b′, and γ′, of 9.60 Å, 5.62 Å, and 91.4 degrees, respectively. These results, the relative orientations of the molecules, and the relative translations of the molecules are in good agreement with results obtained in a concurrent and independent analysis of diffraction data. Energies calculated for rotational and translational displacements in various modes suggest that a range of structures and a fairly large amount of disorder may be present, also in agreement with experiment.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号