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   1548800篇
  免费   27924篇
  国内免费   6958篇
工业技术   1583682篇
  2021年   15529篇
  2020年   12021篇
  2019年   14758篇
  2018年   17251篇
  2017年   16584篇
  2016年   22157篇
  2015年   17622篇
  2014年   28911篇
  2013年   88269篇
  2012年   37229篇
  2011年   50842篇
  2010年   44039篇
  2009年   51964篇
  2008年   47048篇
  2007年   44433篇
  2006年   45974篇
  2005年   40958篇
  2004年   42859篇
  2003年   42601篇
  2002年   41427篇
  2001年   38568篇
  2000年   36749篇
  1999年   36415篇
  1998年   54922篇
  1997年   45228篇
  1996年   37557篇
  1995年   32406篇
  1994年   30023篇
  1993年   29981篇
  1992年   26167篇
  1991年   23355篇
  1990年   23708篇
  1989年   22651篇
  1988年   21180篇
  1987年   19499篇
  1986年   18880篇
  1985年   22189篇
  1984年   22169篇
  1983年   20104篇
  1982年   19149篇
  1981年   19293篇
  1980年   17927篇
  1979年   18357篇
  1978年   17671篇
  1977年   17829篇
  1976年   19468篇
  1975年   15847篇
  1974年   15352篇
  1973年   15469篇
  1972年   12998篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
Revin  A. A.  Mikhaylova  A. M.  Konakov  A. A.  Tsyplenkov  V. V.  Shastin  V. N. 《Semiconductors》2021,55(12):879-884
Semiconductors - The wave functions of electrons localized at P, As, and Sb shallow donors in Ge are calculated in the envelope function approximation taking into account valley–orbit...  相似文献   
142.
This review examines the application, limitations, and potential alternatives to the Hagberg–Perten falling number (FN) method used in the global wheat industry for detecting the risk of poor end-product quality mainly due to starch degradation by the enzyme α-amylase. By viscometry, the FN test indirectly detects the presence of α-amylase, the primary enzyme that digests starch. Elevated α-amylase results in low FN and damages wheat product quality resulting in cakes that fall, and sticky bread and noodles. Low FN can occur from preharvest sprouting (PHS) and late maturity α-amylase (LMA). Moist or rainy conditions before harvest cause PHS on the mother plant. Continuously cool or fluctuating temperatures during the grain filling stage cause LMA. Due to the expression of additional hydrolytic enzymes, PHS has a stronger negative impact than LMA. Wheat grain with low FN/high α-amylase results in serious losses for farmers, traders, millers, and bakers worldwide. Although blending of low FN grain with sound wheat may be used as a means of moving affected grain through the marketplace, care must be taken to avoid grain lots from falling below contract-specified FN. A large amount of sound wheat can be ruined if mixed with a small amount of sprouted wheat. The FN method is widely employed to detect α-amylase after harvest. However, it has several limitations, including sampling variability, high cost, labor intensiveness, the destructive nature of the test, and an inability to differentiate between LMA and PHS. Faster, cheaper, and more accurate alternatives could improve breeding for resistance to PHS and LMA and could preserve the value of wheat grain by avoiding inadvertent mixing of high- and low-FN grain by enabling testing at more stages of the value stream including at harvest, delivery, transport, storage, and milling. Alternatives to the FN method explored here include the Rapid Visco Analyzer, enzyme assays, immunoassays, near-infrared spectroscopy, and hyperspectral imaging.  相似文献   
143.
Mosquito-borne Zika virus (ZIKV) became a real threat to human health due to the lack of vaccine and effective antiviral treatment. The virus has recently been responsible for a global outbreak leading to millions of infected cases. ZIKV complications were highlighted in adults with Guillain–Barré syndrome and in newborns with increasing numbers of congenital disorders ranging from mild developmental delays to fatal conditions. The ability of ZIKV to establish a long-term infection in diverse organs including the kidneys has been recently documented but the consequences of such a viral infection are still debated. Our study aimed to determine whether the efficiency of ZIKV growth in kidney cells relates to glucose concentration. Human kidney HK-2 cells were infected with different ZIKV strains in presence of normal and high glucose concentrations. Virological assays showed a decrease in viral replication without modifying entry steps (viral binding, internalization, fusion) under high glucose conditions. This decrease replication was associated with a lower virus progeny and increased cell viability when compared to ZIKV-infected HK-2 cells in normal glucose concentration. In conclusion, we showed for the first time that an elevated glucose level influences ZIKV replication level with an effect on kidney cell survival.  相似文献   
144.
Multimedia Tools and Applications - Discovering the relevant web services for specific applications in the dynamically changing business world becomes very critical. Researchers have used many...  相似文献   
145.
Journal of Materials Science - For transformers and inductors to meet the world’s growing demand for electrical power, more efficient soft magnetic materials with high saturation magnetic...  相似文献   
146.
Mobile Networks and Applications - 5G/6G communication are first generation high speed wireless communication network which integrates the aerial data, terrestrial data and maritime data via...  相似文献   
147.
148.
Theoretical Foundations of Chemical Engineering - The effect of the electrolyte composition, mass-transfer conditions, pore diameter, interpore distance, and electric parameters on the formation of...  相似文献   
149.
Fluoro-substituted and heteroaromatic compounds are valuable intermediates for a variety of applications in pharma- and agrochemistry and synthetic chemistry. This study investigates the chemoenzymatic preparation of chiral alcohols bearing a heteroaromatic ring with an increasing degree of fluorination in α-position. Starting from readily available picoline derivatives prochiral α-halogenated acyl moieties were introduced with excellent selectivity and 64–95 % yield. The formed carbonyl group was subsequently reduced to the corresponding alcohols using the alcohol dehydrogenase from Lactobacillus kefir, yielding an enantiomeric excess of 95–>99 % and up to 98 % yield.  相似文献   
150.
Journal of Inorganic and Organometallic Polymers and Materials - This paper reports the performance of alizarin based SnO2 dye-sensitized solar cells. A novel template assisted method has been...  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