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   668篇
  免费   16篇
电工技术   24篇
综合类   1篇
化学工业   112篇
金属工艺   14篇
机械仪表   18篇
建筑科学   11篇
能源动力   18篇
轻工业   58篇
水利工程   2篇
无线电   46篇
一般工业技术   110篇
冶金工业   210篇
原子能技术   4篇
自动化技术   56篇
  2023年   1篇
  2022年   3篇
  2021年   9篇
  2020年   4篇
  2019年   11篇
  2018年   13篇
  2017年   8篇
  2016年   10篇
  2015年   2篇
  2014年   12篇
  2013年   33篇
  2012年   15篇
  2011年   34篇
  2010年   18篇
  2009年   19篇
  2008年   21篇
  2007年   16篇
  2006年   20篇
  2005年   17篇
  2004年   24篇
  2003年   18篇
  2002年   13篇
  2001年   10篇
  2000年   11篇
  1999年   14篇
  1998年   73篇
  1997年   65篇
  1996年   32篇
  1995年   12篇
  1994年   14篇
  1993年   22篇
  1992年   6篇
  1991年   5篇
  1990年   7篇
  1989年   12篇
  1988年   6篇
  1987年   4篇
  1986年   8篇
  1985年   7篇
  1984年   6篇
  1983年   5篇
  1982年   5篇
  1981年   5篇
  1980年   9篇
  1979年   5篇
  1978年   3篇
  1977年   6篇
  1976年   3篇
  1975年   6篇
  1973年   2篇
排序方式: 共有684条查询结果,搜索用时 885 毫秒
81.
We evaluated the utility of a hybrid car in which both power sources of an electric motor and a gasoline engine are used and solar cells are settled on the roof and the bonnet. An array of 1.6 kW solar cells was installed on the top of a building to charge the batteries by solar energy. Though the capacities of the electric motor and batteries are half compared with conventional electric vehicles, we confirmed that this hybrid car has sufficient utility for practical use. The whole electric energy consumed in a day can be supplied by 1.6 kW solar cell system.  相似文献   
82.
For future exploration missions to small planetary bodies, in-situ surface observation by robots would be a promising method to investigate the target body whose surface gravity is very small. The authors have researched the mobility system under the microgravity environment and proposed a new mobile system which drives a robot by hopping. Due to the uncertainty of the escape velocity from the target small body, the hop velocity of the robot has to be controlled on-board. This paper proposes a velocity control method of the hopping mechanism, which was evaluated by microgravity experiments and compared with numerical simulation analyses.  相似文献   
83.
We previously reported that loss of heterozygosity (LOH) on chromosome 9p21 correlates with poor prognosis of neuroblastoma and the p16 gene is not expressed in approximately two thirds of neuroblastoma cell lines. Here we demonstrated that p16 expression was induced by 5-aza-2-deoxycytidine treatment in cell lines with 5' CpG island methylation but not in cell lines without methylation. Furthermore, the cell cycle of neuroblastoma cell lines significantly delayed with accumulation of cells in G1 phase by transfection of a wild-type p16 expression vector. These results indicate that p16 is inactivated in part by DNA methylation and its expression is involved in the growth of neuroblastoma cells in vitro. To assess the biological and clinical significance of p16 expression in primary tumors, we undertook immunohistochemical analysis in 74 paraffin sections of neuroblastomas. p16 protein was undetectable in 45 of 74 cases (61%) and lack of p16 expression significantly correlated with poor prognosis of patients and advanced stage of the disease. There was no correlation between loss of p16 expression and N-myc amplification in these tumors. These results indicate that inactivation of the p16 gene is involved in the progression of neuroblastoma independently of N-myc amplification.  相似文献   
84.
The high incidence of loss of heterozygosity (LOH) on chromosome 18q in advanced non-small cell lung carcinomas indicates the presence of tumor suppressor gene(s) on this chromosome arm, which plays an important role in the acquisition of malignant phenotypes in lung cancers. In the present study, we examined 62 lung cancer specimens and 54 lung cancer cell lines for allelic imbalance at 11 microsatellite loci to define common regions of 18q deletions. Allelic imbalance of 18q was detected in 24 (55.8%) non-small cell lung carcinoma specimens and in 6 (31.6%) small cell lung carcinoma specimens, whereas a similar frequency of LOH was statistically inferred to occur in cell lines by analyzing marker homozygosity as an indirect measure of LOH. Five specimens and 11 cell lines showed partial or interstitial deletions of chromosome 18q, and 2 of them had homozygous deletions at the 18q21.1 region. A commonly deleted region was assigned between the D18S46 and y953G12R loci. The size of this region is less than 1 Mb, and the coding exons of three candidate tumor suppressor genes, Smad2, Smad4, and DCC, were mapped outside the region. This result suggests that the common region harbors a novel tumor suppressor gene involved in the progression of lung cancer.  相似文献   
85.
A backfire mode zigzag antenna is analysed using the method of moments. The effects of the filament length of the zigzag on the -10 dB beam width is calculated. The zigzag antenna is applied to a symmetrical paraboloidal reflector antenna as a primary feed. The reflector antenna shows a relatively constant gain in the communication satellite frequency band 12.25-2.75 GHz.<>  相似文献   
86.
An epidermoid tumor inside the Meckel's cave is rare. The symptoms caused by this tumor include trigeminal neuralgia, facial hypesthesia and paresis of the 3rd, 4th and 6th nerves. A case of epidermoid tumor inside Meckel's cave was presented. A 54-year-old female who had complained of 3rd nerve palsy with right facial hypesthesia since 3 years before was referred to our clinic. Magnetic resonance imaging (MRI) showed the tumor at Meckel's cave. The tumor removal was performed using the orbito-zygomatic approach. To avoid injury of the internal carotid artery and nerves inside the cavernous sinus, removal of the tumor inside the capsule was carried out leaving the capsule. Postoperatively, the tumor removal was confirmed by MRI and improvement of the 3rd and the 5th nerve palsy was obtained three months after surgery. This case suggests that the capsule of the tumor inside the Meckel's cave should be allowed to remain to avoid injury of the adjacent 4th, 5th and 6th nerves and of the internal carotid artery.  相似文献   
87.
In this study, we examined a large number of patients to clarify the distribution and frequency of a recently described FLT3 tandem duplication among hematopoietic malignancies, including 112 acute myelocytic leukemia (AML), 55 acute lymphoblastic leukemia (ALL), 37 myelodysplastic syndrome (MDS), 20 chronic myelogenous leukemia (CML), 30 non-Hodgkin's lymphoma (NHL), 14 adult T cell leukemia, 15 chronic lymphocytic leukemia (CLL) and 38 multiple myeloma (MM). We also evaluated 71 cell lines derived from 11 AML, 31 ALL, two hairy cell leukemia, three acute unclassified leukemia, 10 CML, 12 NHL including six Burkitt's lymphoma, and two MM. Using genomic PCR of exon 11 coding for the juxtamembrane (JM) domain and first amino acids of the 5'-tyrosine kinase (TK) domain, this length mutation was found only in AML (22/112, 20%) and MDS (1/37). According to the FAB subclassification, they were 5/18 (28%) of M1, 4/29 (14%) of M2, 3/17 (18%) of M3, 6/24 (25%) of M4, 4/20 (20%) of M5 and 1/9 of refractory anemia with excess of blast in transformation. In the various cell lines examined, this abnormality was determined in only one derived from AML and never found in other hematological malignancies. The sequence analysis of the abnormal PCR products revealed that 23 of 24 showed internal tandem duplication with or without insertion of nucleotides. In one AML, insertion and deletion without duplication was determined. All 24 lengthened sequences were in-frame. Duplication takes place in the sequence coding for the JM domain and leaves the TK domain intact. In conclusion, we emphasize that the length mutation of FLT3 at JM/TK-I domains were restricted to AML and MDS. Since all these mutations resulted in in-frame, this abnormality might function for the proliferation of leukemic cells.  相似文献   
88.
89.
90.
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