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   484篇
  免费   12篇
  国内免费   1篇
电工技术   9篇
综合类   1篇
化学工业   173篇
金属工艺   7篇
机械仪表   8篇
建筑科学   13篇
矿业工程   3篇
能源动力   9篇
轻工业   29篇
水利工程   1篇
无线电   26篇
一般工业技术   82篇
冶金工业   103篇
原子能技术   9篇
自动化技术   24篇
  2022年   2篇
  2021年   4篇
  2020年   4篇
  2019年   3篇
  2018年   3篇
  2017年   11篇
  2016年   7篇
  2015年   6篇
  2014年   10篇
  2013年   29篇
  2012年   12篇
  2011年   21篇
  2010年   14篇
  2009年   25篇
  2008年   31篇
  2007年   14篇
  2006年   6篇
  2005年   12篇
  2004年   8篇
  2003年   12篇
  2002年   14篇
  2001年   14篇
  2000年   9篇
  1999年   11篇
  1998年   41篇
  1997年   27篇
  1996年   24篇
  1995年   18篇
  1994年   18篇
  1993年   12篇
  1992年   9篇
  1991年   5篇
  1989年   4篇
  1988年   3篇
  1987年   2篇
  1986年   3篇
  1985年   3篇
  1984年   8篇
  1983年   2篇
  1982年   3篇
  1981年   4篇
  1980年   5篇
  1979年   2篇
  1978年   3篇
  1977年   3篇
  1976年   4篇
  1975年   4篇
  1972年   2篇
  1971年   2篇
  1967年   1篇
排序方式: 共有497条查询结果,搜索用时 1 毫秒
91.
A new electrospray system has been successfully developed by employing a proportional–integral–derivative control action to maintain an electric current at a certain value. A polymer precursor solution containing polyethylene glycol was used to examine the performance of this system. The result showed that cone-jet geometry could be controlled easily by adjusting the electric current. The length of the cone-jet decreased as the electric current was increased, in a correlation that followed power law. We also found that the cone-jet observed during electrospraying was stable and robust with no disturbance during long periods of use (up to 4000 s). The present study is very useful for further development of high precision aerosol generators and particle synthesis.  相似文献   
92.
Gallium nitride (GaN) nanoparticles were successfully produced from nano-sized gallium oxide (Ga2O3) particles under a flow of ammonia gas. The gallium oxide nanoparticles were prepared by salt-assisted spray pyrolysis (SASP). Highly crystalline Ga2O3 nanoparticles with an average diameter of approximately 10 nm were obtained at various temperatures when a flux salt (LiCl, 5 mol/l) was added to the precursor solution. The effects of the crystallinity of the Ga2O3 particles and nitridation time on transformation to GaN were characterized using X-ray diffraction and scanning/transmission electron microscopy. Highly crystalline GaN nanoparticles with a mean size of 23.4 nm and a geometric standard deviation of 1.68 nm were obtained when Ga2O3 nanoparticles with relatively low crystallinity were used as the starting material. The resulting GaN nanoparticles showed a photoluminescence peak at 364 nm under UV excitation at 254 nm.  相似文献   
93.
In this paper, a new method is proposed for the decolorization of a yellow-hued suspension of rutile TiO2 nanoparticles in an organic solvent (diethylene glycol dimethylether). The presence of color has always been undesirable in a suspension of nanoparticles filler used for industrial needs, particularly for optical applications.A colorless suspension was achieved by irradiating well-dispersed TiO2 nanoparticles in an organic solvent with UV-light (λ = 254 nm) for 5 h. TiO2 nanoparticles of 1 and 5 wt.% were dispersed using a beads mill method. Trimethoxytrifluor(propyl) silane was used as a dispersant to achieve stability. The effect of the UV-light irradiation on the TiO2 nanosuspension was investigated by means of a Fourier transform nuclear magnetic resonance analyzer (FT-NMR). The dispersant was partially desorbed due to the interaction of UV light and the TiO2/dispersant complex. Thus, an enhanced transparency and the absence of color were obtained for well-dispersed TiO2 nanoparticles in an organic solvent.  相似文献   
94.
M Numano  Y Tominaga  K Uchida  A Orihara  Y Tanaka  H Takagi 《Canadian Metallurgical Quarterly》1998,22(10):1098-102; discussion 1103
In secondary hyperparathyroidism (2HPT) fundamentally all parathyroid glands, including supernumerary glands, become hyperplastic, and stimulation of parathyroid glands continues after parathyroidectomy (PTx). Therefore supernumerary glands have special significance during surgery for 2HPT, whether persistent or recurrent HPT. In the present study 570 patients underwent initial total PTx with a forearm autograft. The frequency, type, location, histopathology, and clinical significance of the supernumerary glands were evaluated. At the initial operation 90 supernumerary glands were removed from 82 to 570 patients (14.4%); 12 patients (2.1%) required extirpation of supernumerary glands for persistent/recurrent HPT. Altogether 104 supernumerary glands were identified at operation in 94 of the 570 patients (16.5%). Among these 104 glands, 25 (24.0%) were of the rudimentary, or split, type and 79 (76.0%) of the proper type. Supernumerary glands were most frequently identified in the thymic tongue (53/104, 51.0%); 32 (60.4%) of these 53 glands were identified only microscopically. In 6 of the 570 cases (1.1%), reoperation was required for persistent HPT due to supernumerary glands located in the mediastinum, and 6 patients underwent neck reexploration for recurrence. Histopathologically, 61 of 104 (58.7%) supernumerary glands, including 36 glands recognized only microscopically, showed diffuse hyperplasia, and 43 (41.3%) displayed nodular hyperplasia. Residual small supernumerary glands with diffuse hyperplasia have the potential to be transformed to nodular hyperplasia during long-term hemodialysis. Therefore all parathyroid glands including supernumerary glands should, if possible, be removed at the initial operation. Routine removal of the thymic tongue and careful examination of the regions surrounding the lower poles of the thyroid, especially on the left side, are important steps in the surgical treatment.  相似文献   
95.
We studied the long-term outcome of percutaneous isolated hepatic perfusion (PIHP) for patients with hepatocellular carcinoma. This study included 31 patients with Stage IVA and 5 with IVB disease treated by PIHP until December, 1997. The mean age and tumor diameter were 55 and 7.7 cm, respectively. Twenty-two had portal vein invasion, 13 had hepatic vein invasion, and all patients had multiple intrahepatic metastases of more than 5 tumor foci. The PIHP with adriamycin or cisplatin was undertaken in a total of 50 treatments in these 36 patients. CR was observed in 6 and PR in 13 with an overall response rate of 59%, excluding 4 patients who were not evaluable. Five of 6 patients with CR remain free of disease at 7 to 54 months after the first treatment. The overall survival rate was 67% at 1 year and 32% at 5 years. The survival rates of Stage IVA patients (1-year = 71%, 5-year = 36%) were higher than Stage IVB patients (1-year = 20%, 5-year = 0%). The 5-year survival rates of patients with vascular invasion (Vp1-3 = 23%, Vv1-3 = 8%) were lower than those without it (Vp0 = 47%, Vv0 = 51%). These results indicated that PIHP achieved a 5-year survival rate of approximately 40% in patients with multiple advanced hepatocellular carcinoma in the absence of distant organ metastases and marked vascular invasion, and yielded complete long-term remission in some of these patients.  相似文献   
96.
Mutation of the adenomatous polyposis coli (APC) gene is frequently found in colorectal tumors from both familial adenomatous polyposis (FAP) and non-FAP patients. Analysis of APC mutation is time-consuming and costly due to the large size of the APC gene. As the majority of APC mutations result in the truncation of gene products, the detection of truncated APC proteins may be used as a screening method for APC mutations. The aim of this study is to establish a practical method of detecting truncated APC proteins for the screening of APC mutations. APC proteins in human colorectal cancer cell lines were analyzed by western blotting. Truncated APC proteins were expressed in all of the colorectal cancer cell lines studied. Two species of truncated APC proteins were expressed in two cell lines. Western blotting is a rapid, reliable screening method for APC mutations and provides information on both alleles.  相似文献   
97.
98.
Chemokines such as IFN-inducible protein-10 (IP-10) and JE/monocyte chemotactic protein-1 (MCP-1) are induced in the murine liver in a tissue-specific manner. We examined whether IP-10 and MCP-1 are pathologically involved in chronic hepatitis. Whereas the serum levels of IP-10 and MCP-1 in patients with chronic persistent hepatitis C were elevated compared with those in normal volunteers, both chemokine levels were further significantly higher in patients with the active form (chronic active hepatitis (CAH)). The elevated IP-10 level was not a general phenomenon of inflammation, because it was not seen in patients with rheumatoid arthritis, whereas MCP-1 levels were elevated to the same extent in both patient groups. Better responsiveness to IFN therapy in CAH was related to lesser grades of necroinflammatory activity and was predicted by the lower IP-10 and higher MCP-1 levels. IP-10 levels in patients cured by IFN therapy decreased to the levels in normal volunteers, while the MCP-1 levels only slightly decreased. Serum levels of both chemokines in patients who were not cured remained unchanged after IFN therapy. In situ hybridization analysis of CAH revealed that IP-10 mRNA was expressed mainly in hepatocytes around intralobular focal and periportal piecemeal necrosis, while some MCP-1 mRNA was expressed in some sinusoidal cells. These results suggested that IP-10 plays a specific role in the intralobular accumulation of mononuclear cells and/or the death of hepatocytes in chronic hepatitis.  相似文献   
99.
Sociodemographic differences between rural and urban clients with severe mental illness (SMI) are explored using approaches which extend research in this area beyond limitations found in the few existing studies. Sixteen hundred adult clients from 18 Wisconsin counties are classified according to the degree of rurality of their counties of residence, using two definitions: a dichotomous metropolitan-non-metropolitan grouping and population density. There are significant differences between rural and urban clients for age, gender, and marital status, but not education or income. Young (18-35 years), unmarried males are more likely to live in more densely populated counties. Older (65 and older) women who are currently or previously married are more likely to live in less densely populated counties.  相似文献   
100.
The organization and nucleotide sequence of the capsular gene cluster involved in the biosynthesis of the type 33F capsular polysaccharide of Streptococcus pneumoniae have been determined. The complete type 33F operon (cap33f) is composed of 14 potential open reading frames where the last ten genes are group-specific. Putative functions have been assigned to several gene products by sequence comparison with the proteins included in the databases. A functional promoter located immediately upstream from the first gene of the cap33f gene cluster has been demonstrated. A 20 kb DNA fragment containing the cap33f genes and the operon promoter was sufficient to transform a S. pneumoniae type 3 unencapsulated mutant to the type 33F capsule.  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