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   3151篇
  免费   687篇
  国内免费   598篇
化学   1866篇
晶体学   15篇
力学   347篇
综合类   60篇
数学   1035篇
物理学   1113篇
  2024年   18篇
  2023年   82篇
  2022年   180篇
  2021年   266篇
  2020年   342篇
  2019年   209篇
  2018年   183篇
  2017年   147篇
  2016年   195篇
  2015年   171篇
  2014年   157篇
  2013年   286篇
  2012年   130篇
  2011年   165篇
  2010年   148篇
  2009年   192篇
  2008年   180篇
  2007年   176篇
  2006年   175篇
  2005年   113篇
  2004年   149篇
  2003年   114篇
  2002年   104篇
  2001年   69篇
  2000年   67篇
  1999年   71篇
  1998年   52篇
  1997年   44篇
  1996年   32篇
  1995年   34篇
  1994年   21篇
  1993年   16篇
  1992年   12篇
  1991年   17篇
  1990年   14篇
  1989年   9篇
  1988年   3篇
  1987年   5篇
  1986年   3篇
  1985年   23篇
  1984年   16篇
  1983年   6篇
  1982年   8篇
  1981年   10篇
  1980年   6篇
  1979年   6篇
  1978年   3篇
  1977年   5篇
  1975年   1篇
  1969年   1篇
排序方式: 共有4436条查询结果,搜索用时 15 毫秒
991.
Recombinant antibodies for environmental analysis   总被引:1,自引:0,他引:1  
Initial steps of antibody engineering in the late eighties revolutionized the technology of antibody production, particularly in the area of immunotherapy and diagnostics. Hallmarks that seemed to be out of reach for a long time are now the state of the art, e.g. tailoring of antibodies to match particular needs or by-passing immunization by use of antibody libraries. Despite the apparent benefits of recombinant antibody technologies, this field has been opened up hesitantly for other applications. This review addresses the development of recombinant antibody synthesis in environmental analysis. Examples are given of the molecular evolution of pesticide antibodies and their application for the analysis of real samples.  相似文献   
992.
In this roadmap, we address the development and perspectives of hydrogen evolution reaction, oxygen reduction reaction, oxygen evolution reaction, carbon dioxide reduction reaction and nitrogen reduction.  相似文献   
993.
Photocatalytic hydrogen production from water is considered as an approach for conversion of the solar energy into the chemical energy. During the past decades much efforts have been made to exploit the semiconductor photocatalysts working under both UV a…  相似文献   
994.
995.
Genomic imprinting, the parent of origin‐dependent expression of genes, has been discovered as a fascinating example of the control of gene expression by epigenetic processes in the human body. It affects about 100 genes, which are often involved in growth and development. In this Review, we discuss the mechanisms leading to the generation of gender‐specific imprints in form of DNA methylation marks, their preservation during growth and development of the organism, and the processes that translate parental methylation marks into monoallelic gene expression. We discuss the gender‐specific dimorphic nature of imprints from an evolutionary point of view and present the prevalent model that molecular imprinting mediates a conflict of interest between the parents that occurs in viviparous animals. Finally, we summarize the relevance of parental imprinting for human health.  相似文献   
996.
启发式算法优化有固定投资费用的换热网络时,由于存在整型变量而造成结构进化困难,提出固定投资费用松弛策略.对固定投资费用进行松弛处理实现对数学模型的简化,当换热器换热量很小时固定投资费用几乎为零,随着换热量的增大,固定投资费用以一定斜率逐步增大最终等于实际值.通过松弛强度系数控制变化斜率,在保证优化结果可靠性的基础上引导存在结构进化障碍的换热器生成或消去.对文献中两个算例的优化结果进行分析,考察不同松弛强度下对换热器生成、消去的作用.提出基于固定投资费用松弛策略的强制进化随机游走算法,并应用于换热网络实例.  相似文献   
997.
In the present study, Proteus vulgaris lipase (PVL) was engineered using directed evolution to increase methanol tolerance so that it would be more tolerant and efficient for harsh conditions employed in biodiesel synthesis, which is limiting their industrial use. The influence of ultrasound under different experimental conditions on the biodiesel conversion yield using methanolysis of non-edible neem oil was also emphasized. A special attention was also paid to the immobilization of lipase on Polysulfone (PS) beads and comparative studies with industrially used Burkholderia cepacia lipase. The Engineered Proteus vulgaris lipase showed >80% activity after 3 h when incubated in 50% methanol with simultaneous sonication. The lipase retained improved longevity (~70% residual activity) over wild-type PVL over repeated use.  相似文献   
998.
999.
1000.
Water splitting as a greatly desired technology to produce clean renewable energy, but is hampered by the sluggish oxygen evolution reaction. So, the development of highly active and durable water oxidation electrocatalysts is of primarily significance for energy conversion. Here, a facial strategy to synthesize FeCoNi nanohybrids with adjustable morphological structures by using fluorine is introduced. The morphology and electrocatalytic activity of the sample is determined by the innovative introduction of fluorine. Among them, the overpotential at 10 mA cm−2 of the best sample is approximately 97 mV lower than the commercial RuO2 toward the oxygen evolution reaction in 1 m KOH. Additionally, the catalysts also have low Tafel slopes and remarkable stability.  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