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   1207篇
  免费   198篇
  国内免费   86篇
化学   480篇
晶体学   13篇
力学   110篇
综合类   2篇
数学   323篇
物理学   563篇
  2024年   1篇
  2023年   57篇
  2022年   79篇
  2021年   90篇
  2020年   64篇
  2019年   63篇
  2018年   37篇
  2017年   62篇
  2016年   47篇
  2015年   73篇
  2014年   111篇
  2013年   94篇
  2012年   130篇
  2011年   83篇
  2010年   76篇
  2009年   63篇
  2008年   47篇
  2007年   50篇
  2006年   37篇
  2005年   20篇
  2004年   16篇
  2003年   10篇
  2002年   14篇
  2001年   17篇
  2000年   8篇
  1999年   14篇
  1998年   6篇
  1997年   6篇
  1996年   1篇
  1995年   2篇
  1994年   5篇
  1993年   9篇
  1992年   4篇
  1991年   2篇
  1990年   1篇
  1989年   3篇
  1988年   17篇
  1987年   25篇
  1986年   22篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1981年   3篇
  1980年   1篇
  1979年   4篇
  1978年   5篇
  1976年   7篇
  1957年   1篇
排序方式: 共有1491条查询结果,搜索用时 0 毫秒
61.
A new approach to Burger's equation is proposed using the decomposition method, eliminating smallness assumptions or linearization.  相似文献   
62.
《Nuclear Physics A》1988,486(2):278-284
The internal ionization accompanying the first-forbidden unique electron-capture decay of 41Ca was investigated. The integrated probability of electron ejection with energy greater than 38keV was found to be (0.17 ± 0.02) × 10−5 per K-capture. In this energy range, the measured spectrum of ejected electrons is fairly close to predictions of the simple theory of Primakoff and Porter, and of the relativistic theory of Mukoyama et al. By a model-dependent extrapolation of this spectrum toward low energies, the total probability of internal ionization in 41Ca was estimated and compared with relevant experimental results for other isotopes.  相似文献   
63.
建立了一种简便、高效的靶上脱盐新方法。利用Fe3O4/TiO2磁性纳米材料对肽段的吸附作用,将其作为载体用于靶上肽段富集和脱盐。在对纳米材料使用量、浸洗条件进行优化的基础上,成功地鉴定了溶于10mol/L尿素溶液的100fmol的肌红蛋白样品,也对溶于3mol/L尿素溶液中的10fmol的肌红蛋白样品进行了成功地分析鉴定。通过对肌红蛋白样品进行预处理和质谱分析重复实验,表明该方法重现性好,且简便、高效,所需时间短,一次可同时处理多个样品,易于实现通量化,为有效地解决目前蛋白质组分析中所面临的基质辅助激光解析/离子化飞行时间质谱耐盐性差的问题提供了一种新的手段。  相似文献   
64.
王祥云  陈涛  刘春立 《化学进展》2011,23(7):1400-1410
我国将采用深地质处置的方法处理核能发展所产生的大量高水平放射性废物。为了准确地预测核素的迁移行为,评估处置库的安全性,除了实验之外,还必须使用模型。本文对高放废物地质处置中所涉及的模型,以及与模型相关的软件、数据库做了综述,重点叙述了用于化学种态分析的地球化学模型,扼要介绍了多场耦合模型。此外还简要报告了本实验室核素迁移实验数据的处理方法和程序。  相似文献   
65.
The CD44 family are type-1 transmembrane glycoproteins which are important in mediating the response of cells to their microenvironment, including regulation of growth, survival, differentiation, and motility. All these important functions have been reported to be regulated by N-glycosylation; however, little is known about this process. In the CD44 family, the most prolific isoform is CD44 standard type (CD44s). In this work, an integrated strategy combining stable isotope labeling, chemical derivatization, hydrophilic-interaction liquid chromatographic (HILIC) separation, and mass spectrometric (MS) identification was used to perform a comprehensive qualitative and quantitative survey of the N-glycosylation of recombinant CD44s. Specifically, the occupation ratios of the N-glycosites were first determined by MS with (18)O labeling; the results revealed five glycosites with different occupation ratios. Next, N-glycans were profiled by chemical derivatization and exoglycosidase digestion, followed by MALDI-TOF-MS and HILIC-ESI-MS-MS analysis. Interestingly, the quantitative analysis showed that non-sialylated, fucosylated complex-type glycans dominated the N-glycans of CD44s. Furthermore, the site-specific N-glycan distributions profiled by LC-ESI-MS(E) indicated that most glycosites bore complex-type glycans, except for glycosite N100, which was occupied by high-mannose-type N-glycans. This is the first comprehensive report of the N-glycosylation of CD44s. Figure Strategies for characterization of the N-glycosylation status of CD44s.  相似文献   
66.
An India ink immune reaction was used for the direct detection, in diarrhoel stools, of Escherichia coli possessing the CFA/I, CFA/II and E8775 fimbriae. With this method, a presumptive diagnosis of enterotoxigenic E. coli (ETEC) can rapidly be made. Staining required the bivalency of rabbit anti-fimbriae IgG; the F(ab')2 fragment was necessary. The reaction was impossible with purified Fab fragment. A comparative study of this technique and detection by culture of ETEC strains showed good correlation when the India ink immune reaction was performed at the beginning of infection.  相似文献   
67.
针对融资租赁中租金偿还违约风险的防范问题,研究了如何合理设置租赁保证金来防范违约风险.运用博弈理论建立了租金偿还的动态博弈模型,采用逆向归纳法求解该博弈模型并推导出了预防性保证金确定方法及其适用条件,通过边界条件的改变继而推导出了补偿性保证金确定方法及其适用条件.算例分析表明,运用两种方法来计算租赁保证金时,只需已知租赁项目各期租金和租赁资产的价值而无需知道租赁项目的各期收益,仅以出租人预期租赁项目在各期的收益与租金之间的大小作为判据来选择保证金确定方法.两种保证金确定方法具有较高的实用性和可操作性,是出租人合理地确定租赁保证金的有效方法.  相似文献   
68.
《Tetrahedron letters》1988,29(6):685-688
The acetal stannanes (2) and (3) have been prepared and shown to be of limited use for the preparation of six and seven-membered rings due to an enhanced ability to undergo an alternative β-elimination reaction. A tentative explanation for this enhancement is presented.  相似文献   
69.
王翀  王菲菲  付星球  张恩迪  许志 《中国物理 B》2011,20(5):50701-050701
Alpha-Fe2O3 nanorods are synthesized through a hydrothermal method with no surfactant introduced and ethanol sensors are fabricated from these nanorods.The device can respond to ethanol vapour in a concentration range from 1 to 1500 parts per million and shows both p-type and n-type responding characteristics during the investigation of the ethanol sensing.The sensor displays a p-type characteristic when the ethanol concentration is low and converted into an n-type characteristic as the concentration exceeds a certain value.Such a phenomenon is attributed to the chemisorbed oxygen,which leads to different modifications of the energy band at the surface,namely,depletion layer or inversion layer.  相似文献   
70.
《Nuclear Physics A》1987,474(1):193-218
High-spin states of 159,160Yb have been studied using the escape-suppressed array TESSA 2. Extensions of yrast and lateral bands have been found up to I ~ 40. Experimental data suggest strong correlations between maximum alignment configurations of the valence nucleons and related collective states. Theoretical analysis fully supports the idea of prolate-collective versus oblate-noncollective correlations. Band termination interpretation is discussed.  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