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   244篇
  免费   4篇
电工技术   1篇
化学工业   21篇
金属工艺   2篇
建筑科学   38篇
能源动力   4篇
轻工业   22篇
水利工程   3篇
无线电   5篇
一般工业技术   21篇
冶金工业   120篇
自动化技术   11篇
  2022年   1篇
  2021年   3篇
  2018年   3篇
  2016年   2篇
  2015年   4篇
  2014年   4篇
  2013年   13篇
  2012年   9篇
  2011年   10篇
  2010年   5篇
  2009年   8篇
  2008年   13篇
  2007年   9篇
  2006年   7篇
  2004年   6篇
  2003年   3篇
  2002年   6篇
  2001年   7篇
  1999年   10篇
  1998年   38篇
  1997年   17篇
  1996年   22篇
  1995年   7篇
  1994年   8篇
  1993年   7篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
  1986年   1篇
  1984年   2篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1977年   6篇
  1976年   6篇
  1971年   1篇
  1954年   1篇
排序方式: 共有248条查询结果,搜索用时 15 毫秒
1.
Separate injections of Haemophilus influenzae type b capsular polysaccharide-tetanus conjugate (PRP-T) vaccine and diphtheria-tetanus-pertussis (DTP) reconstitution of freeze-dried PRP-T vaccine with liquid DTP vaccine have been shown to be safe and immunogenic in infants. The present study was conducted to test the safety and immunogenicity of the liquid combination vaccine administered to young infants in the dual-chamber syringe. The study was a monocenter, open clinical trial of 3 month-old infants receiving PRP-T and DTP vaccines in the dual-chamber syringe reconstituted prior to injection. Healthy infants were immunized according to a 3, 4 and 5 months-of-age schedule. The vaccine was administered in a dual-chamber syringe, ready to use with two chambers. The proximal chamber contained freeze-dried PRP-T and the distal chamber contained liquid combination-vaccine DTP. The freeze-dried PRP-T vaccine was reconstituted with the liquid DTP vaccine in the same unidose dual-chamber syringe (0.5 mL) and was injected intramuscularly into the deltoid region. Blood sampling was performed prior to vaccination at 3 months of age and after the third vaccination at 6 months. The primary end-point was the serological response to PRP-T vaccine as expressed by the percentage of infants with an antibody titer greater than or equal to 1 microgram/mL. The reactogenicity was expressed as the percentage of reported local and systemic reactions. A total of 108 infants were included in the study and received the dual-chamber syringe vaccine. After the third injection, all the infants had a PRP antibody titer greater than or equal to 0.15 microgram/mL and 94.4% of infants had a PRP antibody titer greater than or equal to 1 microgram/mL; the pertussis agglutinin titers were over the threshold 40 and 80 in all infants and 98.1% were over the threshold 320. After the third injection, all the infants had diphtheria antibody titers greater than 0.1 IU/mL and 83.3% had titers greater than 1 IU/mL; all the infants had tetanus antibody titers greater than 0.1 IU/mL and 97.2% had results over 1 IU/mL. Thirty-seven infants (34.6%) had local reactions and 64.5% had systemic reactions. The dual-chamber syringe may reduce the cost of vaccine delivery, as well as the workload, and increase the vaccine acceptability and coverage rate of vaccines.  相似文献   
2.
Aspirin-sensitive patients may be desensitized through a graded series of exposures to aspirin. We investigated the underlying mechanism of aspirin desensitization by measuring the release of leukotrienes B4 and C4 from calcium ionophore-stimulated peripheral blood monocytes. Compared with monocytes from normal volunteers (n = 5), monocytes from patients with aspirin-sensitive asthma (n = 10) released increased amounts of thromboxane B2 (1060 +/- 245 pg/ml vs 456 +/- 62 pg/ml), leukotriene B4 (861 +/- 139 pg/ml vs 341 +/- 44 pg/ml), and leukotriene C4 (147 +/- 31 pg/ml vs 56 +/- 6 pg/ml) at baseline. After aspirin desensitization, thromboxane B2 release was almost completely suppressed in both groups. Leukotriene B4 release was significantly decreased in the aspirin-sensitive group (484 +/- 85 pg/ml) but not in the normal subject group (466 +/- 55 pg/ml). The need for prednisone decreased significantly after patients were desensitized to aspirin (10.4 +/- 2.2 mg/day to 1.6 +/- 2.8 mg/day). These results demonstrate that desensitization to aspirin results in decreased monocyte leukotriene B4 release. On the basis of the bronchospastic and inflammatory potential of leukotrienes, the decrease in leukotriene release may contribute to the clinical improvement seen after aspirin desensitization.  相似文献   
3.
4.
Rhabdoid tumor is a well-accepted clincopathologic entity among childhood renal neoplasms; similar tumors have been described in extrarenal locations. We present the clinicopathologic profile and the immunohistochemical features of a series of soft tissue rhabdoid tumors. Twenty-eight cases coded as extrarenal rhabdoid tumor (ERRT), RT, possible ERRT, and "large cell sarcoma" were retrieved from the Armed Forces Institute of Pathology soft tissue registry. The tumors were reclassified according to strict criteria by light microscopy, clinical information, immunohistochemistry, and, in some cases, electron microscopy. Soft tissue rhabdoid tumor (STRT) was defined as (1) a tumor composed of noncohesive single cells, clusters, or sheets of large tumor cells with abundant glassy eosinophilic cytoplasm, an eccentric vesicular nucleus, and an extremely large nucleolus; (2) positivity for vimentin and/or cytokeratin or other epithelial markers by immunostaining; and (3) exclusion of other tumor types with rhabdoid inclusions (melanoma, other sarcomas, carcinoma). Eighteen cases met our criteria for soft tissue rhabdoid tumors. The median patient age was 13 years (range, 6 months to 56 years). Ninety-four percent of STRT cases were positive for vimentin and 59% for pan-cytokeratin. Sixty-three percent and 60% were positive for CAM 5.2 and EMA, respectively. Seventy-nine percent stained for at least one epithelial marker; 76% stained for both vimentin and epithelial markers simultaneously. Forty-two percent stained for MSA, and 14% for CEA and SMA. CD99, synaptophysin, CD57 (Leu-7), NSE, and focal S100 protein were identified in 75%, 66%, 56%, 54%, and 31% of the STRT cases, respectively. All STRT cases examined were negative for HMB-45, chromogranin, BER-EP4, desmin, myoglobin, CD34, and GFAP. Follow-up examination in 61% of the STRT patients revealed that 64% of patients died of disease within a median follow-up interval of 19 months (range, 4 months to 5 years); 82% had metastases to lung, lymph nodes, or liver; 22% had local recurrences before metastasis; and 18% were alive without known disease status (median, 5.5 years). Soft tissue rhabdoid tumor is a highly aggressive sarcoma, predominantly of childhood. Besides having nearly consistent coexpression of vimentin and epithelial markers, STRTs show positivity for multiple neural/neuroectodermal markers that overlap with those of primitive neuroectodermal tumor.  相似文献   
5.
6.
By exploiting the rapid increase in available sequence data, the definition of medically relevant protein targets has been improved by a combination of: (i) differential genome analysis (target list): and (ii) analysis of individual proteins (target analysis). Fast sequence comparisons, data mining, and genetic algorithms further promote these procedures. Mycobacterium tuberculosis proteins were chosen as applied examples.  相似文献   
7.
Interleukin-3 (IL-3) is required for the proliferation, survival and differentiation of myeloid progenitors. In the absence of IL-3, murine myeloid 32D.3 cells accumulate in the G1 phase of the cell cycle and subsequently undergo programmed cell death, or apoptosis. Here we demonstrate that enforced expression of the v-raf oncogene suppresses apoptosis of myeloid 32D.3 cells following the withdrawal of IL-3. Surprisingly, steady state levels of Bcl-2, an oncogene known to suppress apoptosis, were not dependent upon IL-3 in 32D.3 cells and its levels were not augmented in v-raf clones. This suggests that ability of v-raf to suppress apoptosis in the absence of ligand is either Bcl-2 independent or that v-raf kinase promotes Bcl-2 function. v-raf also promoted growth of these cells in the presence of IL-3. v-raf clones proliferated at an increased rate due to a shortened G1 phase and had decreased requirements for IL-3 for growth. Therefore, transformation of myeloid cells by v-raf involves signaling pathways which promote both cell cycle progression and cell survival.  相似文献   
8.
A variety of different photo resists are used for fabrication of MEMS. Presently good results were reported for SU-8, a chemically amplified negative tone photoresist. But SU-8 has a disadvantage for some applications in LIGA technique, especially in the X-ray mask fabrication. After processing the finished resist pattern are hardly soluble from the substrate. This paper will briefly describe the current status of the development of the new negative tone photoresist CAR 44 whose big advantage is the easy removableness of the cross linked pattern. This work widely uses the contents of the presentation “A New Removable Resist for High Aspect Ratio Applications” to the High Aspect Ratio Micro Structure Technology workshop HARMST 2005 held in Gyeongyu (Republic of Korea), June 10–13, 2005.  相似文献   
9.
A non-linear system with time averaging can be regarded as one composed of a time varying system with a variable parameter. A non-linear operation, such as squaring is performed on the signal of the system and followed by low pass filtering. This filtered signal controls, in turn, the variable parameter. This paper considers the steady state analysis of time averaged non-linear systems. The analysis covers both passive (with input) and oscillatory (no input) systems, In the passive case it is shown that the response is similar to that of a passive system with the poles shifted. The harmonic content and distortion are computed for both the oscillatory and passive case. An evaluation of the frequency is carried out for the oscillatory case. An interesting result is that the significant filter characteristic is the attenuation at twice the frequency.  相似文献   
10.
Regulation of organogenesis involves a dynamic balance of the mechanisms regulating cell division, differentiation and death. Here we have investigated the pattern of expression of c-Raf kinase in the inner ear during early developmental stages and the consequences of manipulating c-Raf levels by misexpression of c-raf viral vectors in organotypic cultures of otic vesicle explants. We found that otic vesicles expressed c-Raf and its level remained constant during embryonic days 2 and 3 (E2-E3). c-Raf activity was increased in response to insulin like growth factor-I (IGF-I) and the activation by IGF-I of the c-Raf kinase pathway was a requirement to turn on cell proliferation in the otic vesicle. Overexpression of c-raf in E2.5 explants increased the proliferative response to low serum and IGF-I and blocked differentiation induced by retinoic acid. The increase in c-Raf levels also prevented nerve growth factor (NGF)-dependent induction of programmed cell death. Consistent with these results, the expression of a dominant negative c-Raf mutant potentiated retinoic acid action and decreased the rate of cell proliferation. We conclude that a strict control of c-Raf levels is essential for the co-ordination of the biological processes that operate simultaneously during early inner ear development.  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