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   698篇
  免费   10篇
  国内免费   5篇
工业技术   713篇
  2023年   3篇
  2022年   2篇
  2021年   9篇
  2020年   8篇
  2019年   5篇
  2018年   14篇
  2017年   7篇
  2016年   11篇
  2015年   7篇
  2014年   15篇
  2013年   37篇
  2012年   25篇
  2011年   28篇
  2010年   18篇
  2009年   25篇
  2008年   29篇
  2007年   22篇
  2006年   19篇
  2005年   27篇
  2004年   28篇
  2003年   16篇
  2002年   20篇
  2001年   17篇
  2000年   18篇
  1999年   22篇
  1998年   58篇
  1997年   37篇
  1996年   26篇
  1995年   14篇
  1994年   13篇
  1993年   15篇
  1992年   7篇
  1991年   6篇
  1990年   7篇
  1989年   8篇
  1988年   4篇
  1987年   10篇
  1986年   9篇
  1985年   7篇
  1984年   6篇
  1983年   6篇
  1982年   7篇
  1981年   9篇
  1980年   7篇
  1979年   6篇
  1978年   5篇
  1977年   3篇
  1976年   3篇
  1975年   2篇
  1973年   4篇
排序方式: 共有713条查询结果,搜索用时 15 毫秒
1.
Effects of 5-fluorouracil (5-FU) and UFT on an experimental liver metastasis model were compared at equi-effective dosage levels against subcutaneous tumor of mouse colon 26. 5-FU at the dosage level of 40 mg/kg suppressed the subcutaneous tumor growth by 70.0% and 45.0% on day 13 and day 18, respectively, and UFT at 20 mg/kg provided almost equal suppression (63.0% and 48.0%). In the liver metastasis model, 5-FU at 40 mg/kg showed more potent prevention of the formation of metastatic foci (94.9%) than did UFT (60.4%) at 20 mg/kg. 5-FU at 40 mg/kg produced a much higher peak serum level of 5-FU than did UFT at 20 mg/kg and also showed a much higher AUC (area under the curve) level in the portal blood. These results suggest that oral administration of 5-FU might be useful in prevention of liver metastasis of colorectal cancer.  相似文献   
2.
A nitroalkane-oxidizing enzyme was purified to homogeneity from Neurospora crassa. The enzyme is composed of two subunits; the molecular weight of each subunit is approximately 40,000. The enzyme catalyzes the oxidation of nitroalkanes to produce the corresponding carbonyl compounds. It acts on 2-nitropropane better than on nitroethane and 1-nitropropane, and anionic forms of nitroalkanes are much better substrates than are neutral forms. The enzyme does not act on aromatic compounds. When the enzyme reaction was conducted in an 18O2 atmosphere with the anionic form of 2-nitropropane as the substrate, acetone (with a molecular mass of 60 Da) was produced. This indicates that the oxygen atom of acetone was derived from molecular oxygen, not from water; hence, the enzyme is an oxygenase. The reaction stoichiometry was 2CH3CH(NO2)CH3 + O2-->2CH3COCH3 + 2HNO2, which is identical to that of the reaction of 2-nitropropane dioxygenase from Hansenula mrakii. The reaction of the Neurospora enzyme was inhibited by superoxide anion scavengers in the same manner as that of the Hansenula enzyme. Both of these enzymes are flavoenzymes; however, the Neurospora enzyme contains flavin mononucleotide as a prosthetic group, whereas the Hansenula enzyme contains flavin adenine dinucleotide.  相似文献   
3.
4.
The purpose of pipe rupture studies in JAERI is to perform model tests on pipe whip, restraint behavior, jet impingement and jet thrust force, and to establish a computational method for analyzing these phenomena. This report presents the analytical results of 4-inch pipe whip tests under BWR LOCA conditions.Dynamic response analyses were performed using the general-purpose finite element program ADINA. The test pipe was modelled by straight beam elements and the four restraints were modelled by a single truss element. The analytical results were compared with the experimental results. Impact time and maximum total restraint force showed good agreement with experimental results. On the other hand, pipe strain and pipe deflection could not be predicted so well. The reason for this is that the sliding of the restraint during the pipe whip movement cannot be considered in the analyses.  相似文献   
5.
6.
The surface chemical states of the perovskite-type compounds, strontium doped lanthanum cobalt oxides (La1?x Sr x CoO3), have been investigated using X-ray photoelectron spectroscopy (XPS). Catalytic oxidations of both methane and CO have also been investigated using flow methods. The chemical composition of the surface of La1?x Sr x CoO3 was very different from that in the bulk, which was measured by X-ray fluorescence spectroscopy (XRFS). The catalytic activity of La1?x Sr x CoO3 increased with an increase in the quantity of cobalt atoms on the surface.  相似文献   
7.
This series of articles provides, from an international perspective, an analysis of the future of the automotive industry and aluminum’s role in automobile weight reduction. Part I briefly described technological, environmental, and societal issues that are mandating vehicular weight reduction for, among other reasons, purposes of fuel economy. Part II described the status of the weight-reduction technologies that are currently available and projects how they may evolve in the coming years. Part III, the final installment, examines some of the specific strengths and weaknesses of aluminum alloys with regard to their long-term attractiveness to automakers.  相似文献   
8.
Far-infrared reflection spectra of dielectric ceramics, BaSm2Ti5O14, BaTi4O9, and some pcrovskites such as Ba(Zn1/3Nb2/3)O3, have been measured at room temperature using a Fourier transform infrared spectrometer in order to investigate the effect of the crystal structure on the dielectric properties. As for perovskites, Sr(Zn1/3Nb2/3)O3 and Sr(Mg1/3Nb2/3)O3, in which B site ions are ordered, were also measured. Reflectance data were analyzed by means of a factorized form of dielectric functions instead of the classical dispersion theory, and all of the spectra were well fitted. The values of dielectric constants and tan δ calculated from the reflectance data were in good agreement with resonant cavity measurements at 5 GHz. Furthermore, results of this study have shown that the main contribution to the microwave dielectric properties is caused by low-frequency optically active modes located at 50 to about 300 cm−1, and for perovskite structures it is suggested that the ordering of B site ions is significant in obtaining low dielectric losses.  相似文献   
9.
Watching and tracking an object while seeing a much wider view is one of advantages of the eye system. We proposed and developed a tracking camera system that mimics the eyes by using double-lens modules. In the system, a wide view is captured through the wide-lens module, while the target in it is tracked and magnified through the telescopic lens module. Electronic circuits for tracking control are implemented onto the reconfigurable VLSI or FPGA in order to embed the parallelism in the tracking algorithm into the hardware. A successfully developed FPGA-based prototype performs high-speed tracking at the video-rate. This work was present in part at the 12th International Symposium on Artificial Life and Robotics, Oita, Japan, January 25–27, 2007  相似文献   
10.
Polarization-controlled single-mode VCSEL   总被引:2,自引:0,他引:2  
Relative intensity noise (RIN) in a vertical-cavity surface-emitting laser (VCSEL) was greatly reduced through the use of polarization control to eliminate competition between two orthogonal polarization states by ensuring there was only one polarization state. Polarization was stable with optical feedback of up to 10%. Polarization control was achieved by inducing a small loss anisotropy in fundamental transversal mode VCSEL's. Anisotropic post structures, such as a rectangular post, an oblique post, or a zigzag-sidewall post, were found to be effective in creating loss anisotropy without serious degradation of other VCSEL characteristics such as light-output power or beam profile  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-23

京公网安备 11010802026262号