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   298523篇
  免费   3973篇
  国内免费   729篇
工业技术   303225篇
  2022年   3836篇
  2021年   5660篇
  2020年   4235篇
  2019年   5345篇
  2018年   4853篇
  2017年   4413篇
  2016年   4449篇
  2015年   2876篇
  2014年   4745篇
  2013年   12235篇
  2012年   7428篇
  2011年   10739篇
  2010年   8459篇
  2009年   9309篇
  2008年   9167篇
  2007年   9218篇
  2006年   8370篇
  2005年   7605篇
  2004年   8303篇
  2003年   7885篇
  2002年   7811篇
  2001年   7128篇
  2000年   6244篇
  1999年   6082篇
  1998年   13303篇
  1997年   9596篇
  1996年   7381篇
  1995年   6011篇
  1994年   5560篇
  1993年   5278篇
  1992年   4320篇
  1991年   3819篇
  1990年   4140篇
  1989年   4092篇
  1988年   3809篇
  1987年   3379篇
  1986年   3486篇
  1985年   3979篇
  1984年   3729篇
  1983年   3437篇
  1982年   3240篇
  1981年   3183篇
  1980年   3024篇
  1979年   3010篇
  1978年   3087篇
  1977年   3351篇
  1976年   4113篇
  1975年   2722篇
  1974年   2552篇
  1973年   2619篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Tribology Letters - Most asteroids with a diameter larger than $$\sim 300 \ {\mathrm{m}}$$ are rubble piles, i.e., consisting of more than one solid object. All asteroids are rotating but almost...  相似文献   
82.
Cybernetics and Systems Analysis - The authors propose a method for solving the problem of approach of controlled objects in dynamic game problems with a terminal payoff function. The method is...  相似文献   
83.
Virtual Reality - Do apparatuses and eyestrain have effects on learning performances and quality of experience? Materials and Methods: 42 participants played a serious game simulating a job...  相似文献   
84.
Multimedia Tools and Applications - Modern boom and understanding of our growing needs, applications based on the Mobile Internet of Things (MIoT) are becoming important for future internet...  相似文献   
85.
Wireless Personal Communications - Ultrasound scan plays a predominant role in assisting the health care provider for monitoring pregnancy. This methods is employed for providing insights about...  相似文献   
86.
Cybernetics and Systems Analysis - The paper examines prerequisites and assumptions of the classical Bass innovation diffusion model with the aim of applying it in modeling of relevant stochastic...  相似文献   
87.

Several herbivorous caterpillars contain effectors in their oral secretions that alter the emission of green leaf volatiles (GLVs) produced by the plants upon which the caterpillars are feeding. These effectors include an isomerase, a fatty acid dehydratase (FHD), and a heat-stable hexenal trapping (HALT) molecule. GLVs serve as signaling compounds in plant-insect interactions and inter-and intra-plant communication. However, it is not known whether these GLV-altering effectors are common among herbivorous caterpillars, or the evolutionary context of these effectors in relation to GLV emission by host plants in response to feeding damage. Here, we examined the distribution and activity of the isomerase, FHD, and HALT effectors across 10 species spanning 7 lepidopteran families. Six of the 10 species possessed all three effectors in their oral secretions. Activity from the HALT and FHD effectors was observed in all examined caterpillar species, while activity from the isomerase effector varied in some species and was absent in others. There was no discernable pattern in effector activity based on evolutionary divergence, since individual species within a family did not possess similar mechanisms to alter GLV emission. These data, demonstrating the GLV-altering effectors acting at different steps in the GLV biosynthetic pathway and present in the examined caterpillar species at different combinations with different activities, highlight the importance of these effectors in changing the emission of these compounds during caterpillar herbivory. Understanding the prevalence and roles of GLV-altering effectors and GLV emission itself will open new research areas in the dynamics of plant-insect interactions.

  相似文献   
88.
Theoretical Foundations of Chemical Engineering - The results of numerical modeling of the heat and mass transfer of drops during drying of a liquid under the conditions of...  相似文献   
89.
Protection of Metals and Physical Chemistry of Surfaces - Impedance spectroscopy was used to study the adsorption of the IFKhAN-92 inhibitor, a triazole derivative, on cathodically polarized...  相似文献   
90.
Biomaterials with dynamically tunable properties are critical for a range of applications in regenerative medicine and basic biology. In this work, we show the reversible control of gelatin methacrylate (GelMA) hydrogel stiffness through the use of DNA crosslinkers. We replaced some of the inter-GelMA crosslinks with double-stranded DNA, allowing for their removal through toehold-mediated strand displacement. The crosslinks could be restored by adding fresh dsDNA with complementary handles to those on the hydrogel. The elastic modulus (G’) of the hydrogels could be tuned between 500 and 1000 Pa, reversibly, over two cycles without degradation of performance. By functionalizing the gels with a second DNA strand, it was possible to control the crosslink density and a model ligand in an orthogonal fashion with two different displacement strands. Our results demonstrate the potential for DNA to reversibly control both stiffness and ligand presentation in a protein-based hydrogel, and will be useful for teasing apart the spatiotemporal behavior of encapsulated cells.  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