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   54133篇
  免费   2828篇
  国内免费   159篇
工业技术   57120篇
  2024年   52篇
  2023年   604篇
  2022年   933篇
  2021年   1570篇
  2020年   1146篇
  2019年   1294篇
  2018年   1575篇
  2017年   1540篇
  2016年   1930篇
  2015年   1446篇
  2014年   2294篇
  2013年   3332篇
  2012年   3534篇
  2011年   4255篇
  2010年   3096篇
  2009年   3186篇
  2008年   3021篇
  2007年   2377篇
  2006年   2200篇
  2005年   1875篇
  2004年   1708篇
  2003年   1642篇
  2002年   1456篇
  2001年   1241篇
  2000年   1113篇
  1999年   1039篇
  1998年   1695篇
  1997年   1095篇
  1996年   889篇
  1995年   619篇
  1994年   490篇
  1993年   450篇
  1992年   318篇
  1991年   304篇
  1990年   281篇
  1989年   260篇
  1988年   222篇
  1987年   175篇
  1986年   127篇
  1985年   122篇
  1984年   97篇
  1983年   70篇
  1982年   40篇
  1981年   45篇
  1980年   34篇
  1979年   34篇
  1978年   34篇
  1977年   46篇
  1976年   74篇
  1975年   27篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
5.
6.
A technology for slag formation in the ladle–furnace unit is considered; the slag is based on the CaO–SiO2–MgO–Al2O3–B2O3 system. This technology permits both microalloying of the steel with boron (reduced from the oxide phase) and desulfurization of the steel. The resulting boron content in the steel is 0.001–0.008%; the sulfur content in low-alloy steel and pipe steel is low (0.004–0.010%); and the consumption of manganese ferroalloys is reduced to 0.5 kg/t for 08кп steel and 1.4 kg/t for 09Г2C steel. In addition, the proposed technology increases the strength of the rolled steel, without loss in its plasticity; and reduces the environmental impact thanks to the replacement of fluorspar by colemanite.  相似文献   
7.
Peer-to-Peer Networking and Applications - Recently, as the P2P service environment repeats evolution, its usage in mobile is rapidly increasing. Applications are being developed in various mobile...  相似文献   
8.
Many e-commerce companies collect users’ personal data for marketing purposes despite privacy concerns. Information-collecting companies often offer a monetary reward to users to alleviate privacy concerns and ease the collection of personal information. This study focused on the negative effects of monetary rewards on both information privacy concerns (IPC) and information disclosure. A survey approach was used to collect data and 370 final responses were analysed using a two-way analysis of variance and a binomial logistic regression model. The results show that monetary rewards increase IPC when an information-collecting company requires sensitive information. Additional results indicate that building trust is a more effective way of collecting personal data. This study identifies how organisations can best execute information-collection activities and contributes additional insights for academia and practitioners.  相似文献   
9.
10.
A lotus-type porous carbon steel with cylindrical pores was fabricated by the continuous zone melting method in a pressurized mixture of hydrogen and helium gases. The porosity increases with increasing partial pressure of the hydrogen gas, while the pore diameter remains almost constant, independent of the pressure. The ultimate tensile strength of the specimen with cylindrical pores parallel to the tensile direction is lower than the estimated value, assuming that the strength is decreased in proportion to the decrease of the cross-sectional area of the specimen, while the yield strength is higher than the estimated value. The compressive yield strength is also higher than the estimated value. The increase in yield strength is considered to be due to precipitation strengthening. The tensile strength is increased by quenching and tempering, while the elongation decreases. Such mechanical properties are discussed in terms of the microstructural analysis.  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