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   604篇
  免费   18篇
电工技术   20篇
化学工业   143篇
金属工艺   13篇
机械仪表   16篇
建筑科学   10篇
能源动力   23篇
轻工业   51篇
水利工程   2篇
石油天然气   2篇
无线电   79篇
一般工业技术   108篇
冶金工业   122篇
原子能技术   12篇
自动化技术   21篇
  2023年   5篇
  2022年   9篇
  2021年   18篇
  2020年   6篇
  2019年   5篇
  2018年   8篇
  2017年   13篇
  2016年   12篇
  2015年   8篇
  2014年   13篇
  2013年   36篇
  2012年   22篇
  2011年   30篇
  2010年   14篇
  2009年   19篇
  2008年   21篇
  2007年   23篇
  2006年   15篇
  2005年   20篇
  2004年   11篇
  2003年   22篇
  2002年   15篇
  2001年   12篇
  2000年   16篇
  1999年   19篇
  1998年   48篇
  1997年   30篇
  1996年   20篇
  1995年   24篇
  1994年   15篇
  1993年   15篇
  1992年   5篇
  1991年   5篇
  1990年   4篇
  1989年   8篇
  1988年   5篇
  1987年   3篇
  1986年   2篇
  1985年   3篇
  1984年   2篇
  1983年   6篇
  1982年   3篇
  1981年   4篇
  1980年   2篇
  1979年   3篇
  1978年   3篇
  1977年   7篇
  1976年   3篇
  1975年   4篇
  1974年   2篇
排序方式: 共有622条查询结果,搜索用时 31 毫秒
1.
A single-ended amplifier using small packaged GaN-FETs exhibits a record 2.14 GHz W-CDMA output power. The amplifier, composed of paralleled 48 mm gate periphery FET die, delivers a peak saturated output power of 371 W with a linear gain of 11.2 dB at a drain voltage of 45 V under 2.14 GHz 3GPP W-CDMA signal input. The output power density (output power/package size) of 1.1 W/mm/sup 2/ is twice as high as that of the existing over 300 W GaAs-FET amplifiers. A low 5 MHz offset ACLR of -36 dBc with a drain efficiency of 24% is also obtained at 8 dB power back off from the saturated output power.  相似文献   
2.
We have developed a novel immunoassay method using bacterial magnetic particles for the determination of immunoglobulin G (IgG). Fluorescein isothiocyanate (FITC) conjugated anti IgG-bacterial magnetic particles were prepared. The fluorescence quenching caused by agglutination of FITC-anti IgG antibody-bacterial magnetic particle conjugates was measured by using a fluorescence spectrophotometer. The aggregates based on specific immunoreaction were separated by a gelatin solution. The aggregation of bacterial magnetic particle conjugates was enhanced by application of a magnetic field. The relative fluorescence intensity correlated linearly with a concentration of IgG in the range 0.5-100 ng/mL.  相似文献   
3.
The patient was a 83-year-old female with 2' T2-type gastric cancer associated with positive H. pylori in the lesser curvature of the stomach. The patient was treated with oral UFT-E alone in a daily dose of 400 mg. The tumor exhibited an O' IIa + IIc-like appearance 4 weeks after the start of administration and became scarred 8 weeks later, revealing marked tumor reduction in a short period of time. At 8 weeks, biopsy showed marked polymorphonuclear cells infiltration of gastric mucosa with no evidence of malignancy. In an attempt to eradicate H. pylori, 30 mg of lansoprazole, 400 mg of clarithromycin, and 2.0 g of ecabet-Na (3.0 g of Gastrom) were administered for 2 weeks. H. pylori was found to have been successfully eradicated, and the inflammatory lesions were no longer visible histologically. UFT-E was highly effective in this patient, and the eradication of H. pylori may contribute to the prevention of cancer recurrence.  相似文献   
4.
Antitumor polyacetylenic alcohol, panaxynol, was isolated and purified from a powder of the root of Panax ginseng C.A. Meyer. Panaxynol inhibited the growth of various kinds of cultured tumor cell lines in a dose-dependent manner. In this paper we demonstrated the first specific antibody production against panaxynol. Anti-panaxynol antibody was elicited in rabbits by immunization with panaxynol hemisuccinate-bovine serum albumin conjugate (panaxynol hemisuccinate-BSA conjugate). An enzyme immunoassay (EIA) for the determination of panaxynol was established using a double-antibody technique. The EIA was highly specific against panaxynol although the antibody showed a minimal cross-reactivity with other types of polyacetylenic alcohol, i.e. panaxydol (12.0%) and panaxytriol (0.77%). Panaxynol at a concentration as low as 6.4 ng/ml can be detected. Using this assay we reconfirmed the rapid consumption of panaxynol by target tumor cells in an in vitro-culture system. The anti-panaxynol antibody may be a valuable tool for studies of the biological properties of polyacetylenic compounds.  相似文献   
5.
日本国家计量研究院(National Research Laboratory of Metrology)540kN静重式力基准机中的振荡分量主要是由于砝码的摆动引起的。本文对砝码的动态特性做了详细的分析,给出了其摆动的轨迹图,并对由于砝码摆动引起的相对不确定度进行了评估。提出了一类采用传感器并联的叠加系统(以下称叠加系统)输出的力值信号来评估砝码动态特性的信号处理方法。它对研究静重式测力机砝码摆动提供了有效的分析方法。  相似文献   
6.
The constituents in the fruit of Anthriscus sylvestris Hoffm. were investigated, and four lignans [deoxypodophyllotoxin, morelensin, (-)-deoxypodorhizone, and (-)-hinokinin], one phenylpropanoid [1-(3',4'-dimethoxyphenyl)-1 xi-hydroxy-2-propene], two phenylpropanoid esters [3',4'-dimethoxycinnamyl (Z)-2-angeloyloxymethyl-2-butenoate and 3',4'-dimethoxycinnamyl (Z)-2-tigloyloxymethyl-2-butenoate], and one polyacetylenic compound (falcarindiol) were isolated. Their antiproliferative activity against MK-1, HeLa and B16F10 cell lines is reported.  相似文献   
7.
An ultrahigh-speed 8 bit multiplexer (MUX) has been developed for future-generation optical-fiber communication systems having a data rate of 20 Gb/s. This IC was fabricated using a 0.5 μm WNx/W-gate GaAs MESFET process based on optical lithography, ion implantation, and furnace annealing for good reproducibility and high throughput. The WNx/W bilayer gate has a low sheet resistance, improving the circuit high frequency performance. To attain 20 GHz operation, advanced circuit techniques for the source-coupled FET logic (SCFL) were introduced. A cross coupled source-follower (CCSF) was developed mainly for the highest speed buffers to enhance the bandwidth. The first-stage T-type flip-flop was designed with optimization techniques and operated up to 21.1 GHz  相似文献   
8.
9.
STUDY DESIGN: The present study analyzed the restriction fragment length polymorphism patterns of alpha 2(XI) collagen, bone morphogenetic protein-2, alkaline phosphatase, and tumor necrosis factor-alpha genes in patients with ossification of the posterior longitudinal ligament. This study investigates the genetic polymorphism of bone-induced factors in patients with ossification of the posterior longitudinal ligament and compares it with healthy control subjects. OBJECTIVES: To clarify the genetic markers linked to ossification of the posterior longitudinal ligament. SUMMARY OF BACKGROUND DATA: Ossification of the posterior longitudinal ligament is a genetic disease associated with abnormal calcium metabolism involving the posterior longitudinal ligament. Previous genetic studies have not identified the pathologic mechanism of ossification of the posterior longitudinal ligament. Histopathologic studies of ossification of the posterior longitudinal ligament and the animal model, the spinal hyperostotic mouse, have revealed an increase in Type XI collagen and bone morphogenetic protein-2 expression. METHODS: Eighteen Japanese patients with ossification of the posterior longitudinal ligament and 51 healthy, unrelated control subjects were investigated for the restriction fragment length polymorphism patterns of COL11A2, bone morphogenetic protein-2, alkaline phosphatase, and tumor necrosis factor-alpha, genes with various restriction endonucleases. RESULTS: The gene frequencies of COL11A2 obtained with BamHl (10.0 kb fragment) and HindIII (19.0 kb fragment) observed in patients with ossification of the posterior longitudinal ligament were higher compared with control subjects (0.43 and 0.14, respectively). These differences were statistically significant (BamHl P = 0.018; Hindlll P = 0.046). Two new restriction fragment length polymorphism patterns were detected of the bone morphogenetic protein-2 gene with Mspl and Taql and one already known restriction fragment length polymorphism pattern of the tumor necrosis factor-alpha gene with Ncol. However, they were not significantly different from the control subjects. CONCLUSIONS: Seven restriction fragment length polymorphisms of COL11A2 gene were identified. Two of them (BamHl, 10.0/10.0 kb genotype; HindIII, 19.0/19.0 kb genotype) were significantly different in patients with ossification of the posterior longitudinal ligament.  相似文献   
10.
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