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   2270篇
  免费   3篇
  国内免费   2篇
工业技术   2275篇
  2018年   1篇
  2016年   1篇
  2013年   2篇
  2012年   277篇
  2011年   382篇
  2010年   77篇
  2009年   21篇
  2008年   228篇
  2007年   235篇
  2006年   161篇
  2005年   138篇
  2004年   123篇
  2003年   99篇
  2002年   97篇
  2001年   82篇
  2000年   94篇
  1999年   33篇
  1998年   19篇
  1997年   22篇
  1996年   20篇
  1995年   22篇
  1994年   24篇
  1993年   7篇
  1992年   11篇
  1991年   9篇
  1990年   13篇
  1989年   24篇
  1988年   4篇
  1987年   7篇
  1986年   4篇
  1985年   5篇
  1984年   7篇
  1983年   4篇
  1982年   4篇
  1981年   2篇
  1980年   3篇
  1979年   2篇
  1978年   5篇
  1977年   1篇
  1976年   3篇
  1973年   1篇
  1957年   1篇
排序方式: 共有2275条查询结果,搜索用时 15 毫秒
1.
不少人都觉得S60打开短信的速度太慢,从桌面上的左软键进入"信息"大约需要2秒~3秒,还不如从"功能表"按"1"进入"信息"来得快,这是什么原因呢?  相似文献   
2.
3.
4.
5.
Graph visualization has been widely used to understand and present both global structural and local adjacency information in relational data sets (e.g., transportation networks, citation networks, or social networks). Graphs with dense edges, however, are difficult to visualize because fast layout and good clarity are not always easily achieved. When the number of edges is large, edge bundling can be used to improve the clarity, but in many cases, the edges could be still too cluttered to permit correct interpretation of the relations between nodes. In this paper, we present an ambiguity-free edge-bundling method especially for improving local detailed view of a complex graph. Our method makes more efficient use of display space and supports detail-on-demand viewing through an interactive interface. We demonstrate the effectiveness of our method with public coauthorship network data.  相似文献   
6.
The upper and lower limits of the electrostrictive constants, dielectric permittivities, spontaneous polarizations, and piezoelectric coefficients were calculated for ceramic PbTiO(3) from theoretical single-crystal constants. Experimental ceramic data fall between these upper and lower limits. The large piezoelectric anisotropy d(33)/d(31) of ceramic PbTiO(3 ) was shown to be related to the single-crystal PbTiO(3) electrostrictive anisotropies Q(11)/Q(12 ) and Q(44)/Q(12). The possibility of a change in sign of the ceramic d(31) coefficient due to a slight variation in the single-crystal electrostrictive anisotropies was discussed. The single-crystal and predicted ceramic hydrostatic electrostrictive constants were found to be equal. Using this result the ceramic hydrostatic g(h ) coefficient is always smaller than the single-crystal g (h), but the ceramic hydrostatic d(h) coefficient can be either larger or smaller than the single-crystal d(h) depending on the dielectric anisotropy (epsilon (11)/epsilon(33)) of the single-crystal.  相似文献   
7.
This paper describes the outcome of user trials of the Nordic Musculoskeletal Questionnaire which encompassed the views of the following groups: data entry clerks, technical staff, administrative clerks and 481 subjects employed in 10 supermarkets. A significant number of improvements was identified, especially concerning its wording, layout and administration. This has led to a standardized version being produced for use in studying the prevalence of reported symptoms in many types of occupational groups.  相似文献   
8.
The response characteristics of two tomographic systems were compared for imaging of positron emitters: a) a SPECT system with a 3/8 in crystal and 511 keV detector shielding, equipped with a specially designed 511 keV collimator, and b) a PET V system using coincidence detection. SPECT transverse plane resolution was 19 mm FWHM and 35 mm FWTM for a radius of rotation of 16 cm. Corresponding resolution for PET was 14 mm FWHM and 28 mm FWTM. Transverse images through a phantom containing cylindrical sources of various cross sections and uniform activity were obtained for each detector. The measured count density or recovery coefficient was found to decrease with source size, the dependence being similar for both systems. The theoretical values for recovery coefficients were calculated by convolution of a Gaussian fit to the SPECT resolution (FWHM, FWTM) values with the uniform cross section of each source. This simple mathematical model confirmed that the recovery coefficient dependence on source size was primarily related to the limited resolution of the detector. Experimental measurements demonstrated that the SPECT resolution for volume sources was sufficient for quantitation, although some limitations exist with respect to source sizes smaller than the detector resolution.  相似文献   
9.
10.
This work presents methods for estimating relaxation times T1 and T2 and proton density using a real time digital video processor. This device performs each mathematical step of the fitting algorithms in one video frame interval (1/30 s). Two-point fits of T1 and T2 may be generated in approximately 15 video frame intervals or about 0.5 s; generation of a T2 image from four acquired images requires about 30 video frame intervals or about 1 s. The hardware is common to many commercial MR scanners and requires no array processor. Such high-speed techniques can expedite the clinical use of computed images and facilitate the implementation of image synthesis.  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