首页 | 官方网站   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   485篇
  免费   28篇
工业技术   513篇
  2023年   2篇
  2022年   4篇
  2021年   34篇
  2020年   6篇
  2019年   11篇
  2018年   10篇
  2017年   17篇
  2016年   18篇
  2015年   9篇
  2014年   26篇
  2013年   49篇
  2012年   17篇
  2011年   26篇
  2010年   16篇
  2009年   16篇
  2008年   16篇
  2007年   19篇
  2006年   16篇
  2005年   18篇
  2004年   13篇
  2003年   11篇
  2002年   6篇
  2001年   5篇
  2000年   9篇
  1999年   6篇
  1998年   36篇
  1997年   29篇
  1996年   21篇
  1995年   10篇
  1994年   10篇
  1993年   6篇
  1992年   1篇
  1990年   3篇
  1989年   2篇
  1988年   2篇
  1985年   1篇
  1983年   1篇
  1980年   1篇
  1979年   1篇
  1976年   1篇
  1975年   3篇
  1974年   1篇
  1973年   1篇
  1970年   1篇
  1966年   1篇
  1965年   1篇
排序方式: 共有513条查询结果,搜索用时 171 毫秒
101.
The behavior of the dielectric properties of gelatin in the frequency range from 10(3) Hz to 10(7) Hz was investigated and compared with that of the globule protein, bovine serum albumin (BSA), desalted gelatin and BSA being used. Dielectric relaxation was observed for both the gelatin and BSA solutions. The relaxation data were fitted well by the Cole-Cole equation; the Cole-Cole parameter (beta) and the relaxation time (tau) were obtained. For the BSA solutions, tau was proportional to the solution viscosity (eta) at 40 degrees C and 25 degrees C, and the values of beta at 40 degrees C were similar to those at 25 degrees C. For gelatin solution, tau was proportional to eta at 40 degrees C, but was not proportional to eta at 25 degrees C. In addition, the values of beta at 25 degrees C were smaller than those at 40 degrees C. These results indicate that the rotation of gelatin and/or polarization of submolecular groups in the coil state greatly contributed to the dielectric relaxation at 40 degrees C; on the other hand, the formation of cross-linking junctions consisting of helix structures would have affected the dielectric relaxation at 25 degrees C.  相似文献   
102.
The distribution of gamma delta-T cells (gamma delta-TCR positive cells) in nasal mucosa and polyps was studied in patients with nasal allergy and non-allergic patients. The biopsy specimens from the inferior turbinate and resected polyps were frozen at -70 degrees C and sliced at a thickness of 4 microns with a cryostat. Monoclonal antibodies (CD3 and TCR-gamma delta-1) and the Labelled Streptavidin Biotin method were used to detect T lymphocytes and gamma delta-T cells. The results were as follows: 1) The rate of gamma delta-T cells in the epithelium is higher than that in the lamina propria in patients with nasal allergy. 2) In non-allergic patients, on the other hand, the rate of gamma delta-T cells was almost the same in these layers. 3) The distribution of gamma delta-T cells in nasal polyps was uniform and their rate was relatively high. It has been reported that gamma delta-T cells can recognize a stress antigen such as heat shock protein. These cells are thought to play an important role in non-specific immunoreactions. This study suggests that gamma delta-T cells in the nasal mucosa play an important role also in specific immunoreactions.  相似文献   
103.
The problem of detecting electrons in the 0.5–4.0 GeV energy range, in the presence of a high pion background, has been studied using a new type of electromagnetic shower detector. Its structural properties and the main parameters are given, together with the basic results in terms of energy resolution and of rejection power against pion background. The optimization of this new instrument gives a pion rejection power of ~ 6 × 10?4 for energy ? 1.2 GeV.  相似文献   
104.
von Recklinghausen's disease, or type I neurofibromatosis, a common familial tumor syndrome, is characterized by the occurrence of multiple benign neoplasms of nerve sheath cells. The disease is caused by germ-line mutations of the NF1 gene, which encodes a member of the GTPase-activating superfamily of Ras regulatory proteins. We analyzed 5 dinucleotide repeat loci in DNAs from neurofibromas and matched normal skin from 16 NF1 patients. Eight cases (50%) manifested microsatellite alterations. Expansions or compressions of dinucleotide repeats were observed at one locus in four cases and at two loci in one case. Banding patterns compatible with the loss of a microsatellite allele were observed in four cases, including one that also presented microsatellite instability. The surprisingly high frequency of microsatellite alterations suggests that the NF1 gene or another gene(s) contributing to the pathogenesis of neurofibromas might be directly or indirectly implicated in the control of genomic integrity.  相似文献   
105.
106.
The development of a superconductive detector for simultaneous measurement of energy and arrival time is reported. The detector consists of two superconducting tunnel junctions coupled through a passive network. The first junction operates in the quasi-particle regime and measures the energy absorbed by counting the total charge that tunnels. The second junction uses the DC Josephson effect to act as a fast discriminator for the onset of surplus current in the first junction. The feasibility of the detector is demonstrated through simultaneous time and energy measurements of 6 keV X-rays. A model of the detector is presented and numerical simulations show good correspondence with experimental data.  相似文献   
107.
The class I antiarrhythmic drug procainamide (Pd) was tested on BDF1 mice for its chemoprotective activity against cis-diamminedichloroplatinum(II) (DDP) toxicity. Pd at the dose of 50 mg/kg protected mice against otherwise lethal doses of DDP (survivors at Day 14 after 25 mg/kg DDP or 25 mg/kg DDP-Pd treatment: 0% vs 100%) and greatly reduced the weight loss induced by DDP. Moreover, the increased plasma urea nitrogen levels caused by a single ip administration of DDP in water (8 or 16 mg/kg) as well as the tubular degenerative changes detected by light microscopy were prevented by Pd. Pd had no effect on the sensitivity of P388 leukemic cells to DDP in vitro, but the administration of DDP (16 mg/kg) and Pd (50 mg/kg) to BDF1 mice bearing P388 leukemic cells produced a significant increase in survivals compared to mice receiving ip DDP alone diluted in 0.9% NaCl solution. The increased efficacy of this combination therapy in P388 leukemic mice compared to a single DDP treatment at the same dose was observed both when the drugs were administered ip simultaneously (p = 0.042) and when DDP and Pd were given ip and iv, respectively (p = 0.018). Since procaine, which differs from Pd merely in the replacement of the amide by the ester linkage, has also been reported to significantly enhance DDP efficacy (M. Esposito et al., 1990, J. Natl. Cancer Inst. 82, 677-684.), a comparison of their effects in tumored mice exposed to DDP has been made. Although both drug combinations were superior to that of DDP alone, in terms of both survival time and numbers of cures, Pd treatment seems to offer better protection against DDP-induced lethality than did procaine.  相似文献   
108.
109.
PURPOSE: At least in some European Countries, there is still considerable controversy regarding the choice between surgery and radiotherapy for the treatment of patients with early laryngeal-glottic carcinoma. METHODS AND MATERIALS: Two hundred and forty-six patients with laryngeal-glottic neoplasms, Stage I-II, were treated with radical radiotherapy. Before radiotherapy the patients were evaluated to determine the surgical procedure of choice. Either 66-68.4 Gy (33-38 fractions) or 63-65 Gy (28-29 fractions) of radiation therapy (RT) were administered. The overall disease free survival was determined for each subgroup of patients. Univariate and multivariate analyses were performed to determine significant prognostic variables. RESULTS: Five- and 10-year overall survival rates were 83 and 72%, respectively. At a median follow-up of 6 years 204 patients are alive and disease free. No patient developed distant metastases. One patient died of a large local recurrence, 38 patients died of causes unrelated to their tumor, and 3 patients were lost to follow-up. The multivariate analysis confirmed that performance status (PS), macroscopic presentation of the lesion, and persistence of dysphonia after radiotherapy are significant prognostic factors. CONCLUSIONS: According to the multivariate analysis, the patients with PS > 80 and with exophytic lesions are eligible for radical RT. The surgical procedure proposed for each patient was not found to be an independent prognostic factor.  相似文献   
110.
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-23

京公网安备 11010802026262号