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   272篇
  免费   5篇
电工技术   13篇
化学工业   51篇
金属工艺   13篇
机械仪表   1篇
建筑科学   7篇
矿业工程   1篇
能源动力   7篇
轻工业   12篇
水利工程   2篇
无线电   29篇
一般工业技术   23篇
冶金工业   95篇
原子能技术   2篇
自动化技术   21篇
  2023年   2篇
  2022年   2篇
  2021年   4篇
  2020年   6篇
  2019年   4篇
  2018年   2篇
  2017年   3篇
  2016年   6篇
  2015年   4篇
  2014年   3篇
  2013年   15篇
  2012年   5篇
  2011年   12篇
  2010年   7篇
  2009年   10篇
  2008年   6篇
  2007年   5篇
  2006年   4篇
  2005年   6篇
  2004年   4篇
  2003年   5篇
  2002年   8篇
  2001年   9篇
  2000年   3篇
  1999年   5篇
  1998年   43篇
  1997年   18篇
  1996年   15篇
  1995年   8篇
  1994年   8篇
  1993年   7篇
  1992年   4篇
  1991年   3篇
  1990年   4篇
  1989年   1篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1983年   2篇
  1982年   2篇
  1981年   4篇
  1980年   5篇
  1979年   2篇
  1978年   1篇
  1976年   4篇
  1975年   1篇
  1971年   1篇
排序方式: 共有277条查询结果,搜索用时 9 毫秒
61.
The effect of Mo on the corrosion behavior of Ni20Cr–xMo alloys in an oxidizing chlorine-containing atmosphere using air mixed with the salt-vapor mixture of NaCl–KCl–CaCl2 at 570°C was investigated. The results revealed that the corrosion performance of the Ni20Cr alloys in the oxidizing chlorine atmosphere was improved by Mo addition of up to 3 wt%. The Mo-free alloy formed a potassium chromate during corrosion as a result of the reaction between the Cr2O3 scale and KCl vapor. The chromate formation increased the chlorine potential at the scale surface and induced the breakdown of the protective Cr2O3 scale, resulting in internal chromium chloride precipitates and a Cr-depleted zone. In contrast, the presence of Mo resulted in the formation of a NiO scale, which did not react with the salt vapors and, therefore, prevented the formation of chromates. The beneficial effect of Mo on the high-temperature chlorination of Ni–Cr alloys in salt-vapor-containing atmospheres was ascribed to the suppression of chlorine generation due to NiO scale formation.  相似文献   
62.
63.
We determined whether tumor cells consistently generating granulocyte/macrophage colony- stimulating factor (GM-CSF) can recruit and activate macrophages to generate angiostatin and, hence, inhibit the growth of distant metastasis. Two murine melanoma lines, B16-F10 (syngeneic to C57BL/6 mice) and K-1735 (syngeneic to C3H/HeN mice), were engineered to produce GM-CSF. High GM-CSF (>1 ng/10(6) cells)- and low GM-CSF (<10 pg/10(6) cells)-producing clones were identified. Parental, low, and high GM-CSF-producing cells were injected subcutaneously into syngeneic and into nude mice. Parental and low-producing cells produced rapidly growing tumors, whereas the high-producing cells produced slow-growing tumors. Macrophage density inversely correlated with tumorigenicity and directly correlated with steady state levels of macrophage metalloelastase (MME) mRNA. B16 and K-1735 subcutaneous (s.c.) tumors producing high levels of GM-CSF significantly suppressed lung metastasis of 3LL, UV-2237 fibrosarcoma, K-1735 M2, and B16-F10 cells, but parental or low-producing tumors did not. The level of angiostatin in the serum directly correlated with the production of GM-CSF by the s.c. tumors. Macrophages incubated with medium conditioned by GM-CSF- producing B16 or K-1735 cells had higher MME activity and generated fourfold more angiostatin than control counterparts. These data provide direct evidence that GM-CSF released from a primary tumor can upregulate angiostatin production and suppress growth of metastases.  相似文献   
64.
The EORTC QLQ-C30 was developed in English-speaking cultures. To determine if this instrument could cross a broad cultural divide and be used in Japan, the cross-cultural validity of its Japanese version was estimated. In evaluating psychometric testing, internal consistency by Cronbach's alpha, item-discrimination by multitrait scaling analysis, and validity analysis with ECOG performance score (PS) and Karnofsky Performance Status Scale (KPS) were performed. The QLQ-C30 (version 1.0) was given to 105 patients with lung cancer. Although the response rate was low in patients with PS 4, the questionnaire was well accepted by patients with PS 0-3. The Japanese QLQ-C30 has a weak scale of role functioning in terms of item discriminative validity. It also has a weak scale of cognitive functioning in items of discriminative validity and internal consistency. However, known-groups comparison showed the expected clinical validity with PS for all the scales except for financial impact, and longitudinally clinical validity with KPS was shown in scales of cognitive functioning, fatigue, and nausea and vomiting. Multitrait scaling analysis showed that the predicted scales constituting quality of life (QOL) in the English-speaking culture were extracted from the Japanese QLQ-C30, and found to be valid in Japan, indicating its possible usefulness as an instrument that is universally applicable across cultures.  相似文献   
65.
Extramedullary plasmacytoma (EMP) is a very rare disease and mainly arises in the head and neck area. We herein reported a case of EMP arising in the retroperitoneal space. A 46-year-old man was referred to our outpatient clinic in November 1989 with the complaint of flank pain on the left side. Radiological examinations showed a tumor formation in the retroperitoneal space, which involved the left kidney, spleen and pancreas. Immunoelectrophoresis showed an elevation of serum IgG level and a spike of M-protein was detected in the serum protein electrophoresis. No bone lesions were detected, and bone marrow aspiration showed no abnormal cells. US-guided needle biopsy of the tumor led to the histological diagnosis as plasmacytoma of the IgG-kappa type. Following three cycles of preoperative chemotherapy (a THP-COP regimen), which resulted in a size reduction of the tumor by 40%, extensive resection of the tumor including extirpation of the left kidney, spleen, and tail of pancreas was performed. Because of tumor extension into the posterior wall of the stomach, however, the surgery resulted in incomplete resection. A total of 11 cycles of postoperative chemotherapy (THP-COP) was performed periodically for the residual tumor in the stomach. Rapid tumor spreading in addition to re-elevation of the serum IgG level, however, developed after the 11th postoperative chemotherapy, which extensively involved the stomach and intestines. The patient died of the disease 33 months after the initiation of treatment.  相似文献   
66.
Several EEG studies have reported an early component of the visual evoked potential. However, it is controversial whether this component is cortical or subcortical. Our study has aimed to clarify this problem using MEG and EEG in nine normal volunteers. A total of 4000 stimuli were presented to the monocular visual hemifield through a light-proof stimulating goggle and the visual evoked magnetic field and visual evoked potential was measured above the occipital lobe. The early component was observed in three of the nine subjects. The latency ranged from 40 to 45 ms in MEG and from 39 to 47 ms in EEG. The result of dipole localization analysis showed that its origin was cortical, and specifically, the striate cortex.  相似文献   
67.
1. 11 beta-Hydroxysteroid dehydrogenase (11-HSD) activity in mesenteric arteries of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats was determined and expressed as the percentage conversion of [3H]-corticosterone to [3H]-11-dehydrocorticosterone. 2. 11-HSD activity was significantly decreased in mesenteric arteries of both 4 and 9 week old SHR (8.4 +/- 0.8%, 5.0 +/- 1.5%, respectively) compared with WKY rats (12.4 +/- 0.6%, 15.8 +/- 0.7%, respectively; P < 0.05). 3. Total RNA from rat vascular smooth muscle cells (VSMC) and endothelial cells (EC) were prepared with selective precipitation in 3 mol/L LiCl/6 mol/L urea. The expression of 11-HSD mRNA was confirmed in the rat VSMC but its mRNA expression was not detected in EC, using northern blot analysis. 4. The results in this study indicate that 11-HSD in the vascular wall may play a role in the pathogenesis of hypertension in SHR.  相似文献   
68.
BACKGROUND: Local failure rates are high for locally irresectable primary or recurrent colorectal cancer, even when chemoradiation therapy is employed. AIM: This review evaluates evidence supporting aggressive preoperative chemoradiation followed by maximal surgical resection and intraoperative radiation therapy to achieve disease control and cure for patients with locally advanced irresectable primary or recurrent rectal cancer. RESULTS: A 5-year survival rate of 42 per cent with a central failure rate of 2 per cent may be achieved in patients with locally irresectable primary rectal cancer. In patients with locally recurrent disease, these values at 5 years are 18 and 28 per cent respectively. The 5-year incidence of distant metastasis remains high, affecting 64 per cent of patients with primary cancer and 75 per cent of those with recurrent cancer. CONCLUSION: A disease-free surgical resection margin remains paramount to achieve cure. Encouraging trends exist, however, for further evaluation of multimodality therapy as a means of reducing local recurrence of disease.  相似文献   
69.
This paper reports the design and performance of a multi-channel FM-SCM video distribution system that can be placed into practical use. Fifty FM video channels can be delivered to more than 10 000 customers through three-cascaded erbium-doped fiber amplifiers, and wideband/low-noise analog SCM links. As the outdoor plant is completely passive, reliability and easy maintenance can be expected. An evaluation of fabricated equipment shows good transmission quality and stable operation  相似文献   
70.
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