全文获取类型
收费全文 | 8982篇 |
免费 | 971篇 |
国内免费 | 851篇 |
专业分类
化学 | 3278篇 |
晶体学 | 79篇 |
力学 | 2332篇 |
综合类 | 128篇 |
数学 | 1503篇 |
物理学 | 3484篇 |
出版年
2024年 | 17篇 |
2023年 | 73篇 |
2022年 | 166篇 |
2021年 | 250篇 |
2020年 | 308篇 |
2019年 | 208篇 |
2018年 | 235篇 |
2017年 | 327篇 |
2016年 | 449篇 |
2015年 | 340篇 |
2014年 | 487篇 |
2013年 | 574篇 |
2012年 | 443篇 |
2011年 | 566篇 |
2010年 | 498篇 |
2009年 | 569篇 |
2008年 | 550篇 |
2007年 | 582篇 |
2006年 | 528篇 |
2005年 | 466篇 |
2004年 | 478篇 |
2003年 | 397篇 |
2002年 | 330篇 |
2001年 | 282篇 |
2000年 | 258篇 |
1999年 | 242篇 |
1998年 | 208篇 |
1997年 | 150篇 |
1996年 | 132篇 |
1995年 | 112篇 |
1994年 | 94篇 |
1993年 | 56篇 |
1992年 | 43篇 |
1991年 | 59篇 |
1990年 | 47篇 |
1989年 | 24篇 |
1988年 | 38篇 |
1987年 | 32篇 |
1986年 | 24篇 |
1985年 | 25篇 |
1984年 | 21篇 |
1983年 | 6篇 |
1982年 | 23篇 |
1981年 | 8篇 |
1980年 | 14篇 |
1979年 | 22篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1974年 | 5篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
981.
《中国化学》2017,35(7):1165-1169
We synthesized a new cyanide (CN −) chemosensor CX based on a nucleophilic addition reaction prompted by cyanide ion, which could be used for highly selective and sensitive fluorescence turn‐on detection of cyanide in aqueous media. The CX showed selective fluorescence recognition for CN −, the miscellaneous competitive anions (F−, Cl−, Br−, I−, AcO −, H2PO4−, HSO4−, ClO4−, S2 −, PO43−, CO32− and SCN −) did not lead to any significant interference. The detection limit of the sensor towards CN − is 1.15 × 10−7 mol•L−1. The sensor has been successfully applied to estimate the cyanide ion in seeds of cherries. Test strips based on CX were fabricated, which could be used as a convenient and efficient CN − test kit to detect CN − in aqueous solution for “in‐the‐field” measurement. 相似文献
982.
《Macromolecular rapid communications》2017,38(21)
Increasing complexity and diversity of polymersomes and their compartments is a key issue for mimicking cellular functions and protocells. Thus, new challenges arise in terms of achieving tunable membrane permeability and combining it with control over the membrane diffusion process, and thus enabling a localized and dynamic control of functionality and docking possibilities within or on the surface of polymeric compartments. This study reports the concept of polymersomes with pH‐tunable membrane permeability for controlling sequential docking and undocking processes of small molecules and nanometer‐sized protein mimics selectively on the inside and outside of the polymersome membrane as a further step toward the design of intelligent multifunctional compartments for use in synthetic biology and as protocells. Host–guest interactions between adamantane and β‐cyclodextrin as well as noncovalent interactions between poly(ethylene glycol) tails and β‐cyclodextrin are used to achieve selective and dynamic functionalization of the inner and outer spheres of the polymersome membrane. 相似文献
983.
Sanchita Mondal Saikat Kumar Manna Kalipada Maiti Rajkishor Maji Syed Samim Ali Srimanta Manna 《Supramolecular chemistry》2017,29(8):616-626
A FRET-based chemosensor L containing donor phenanthroline and acceptor fluorescein moiety was designed, synthesised and characterised for the ratiometric fluorescent detection of Cu2+ in organo-aqueous solution. Probe L showed high selectivity and excellent sensitivity towards Cu2+ ions by exhibiting both colorimetric and fluorometric changes due to opening of the spirolactum ring of fluorescein upon complexation with Cu2+. In presence of Cu2+ ions, probe L formed L-Cu2+ complex in 1:1 stoichiometric fashion which is established on the basis of Job’s plot and mass spectroscopy. We also performed DFT computational studies to know the binding nature and coordination feature of the complex. Furthermore, fluorescence imaging studies revealed that probe L was cell permeable and could be used to detect intracellular Cu2+ in living cells. 相似文献
984.
随着信息技术的进步和发展,现代生物学越来越多地将这些技术用于大规模生物数据的收集、分析、挖掘等过程.大量计算机技术,特别是统计方法被用来进行复杂疾病的分析.大量研究表明,人体的许多表型性状差异以及对药物和疾病的易感性等都可能与某些位点相关联,或和包含有多个位点的基因相关联.因此,定位与性状或疾病相关联的位点在染色体或基因中的位置,能帮助研究人员了解性状和一些疾病的遗传机理,也能使人们对致病位点加以干预,防止一些遗传病的发生.利用随机森林方法、Bootstrap重抽样、logistic回归等大数据分析方法,意在解决优化生物学位点关联性分析中单一致病位点识别、多位点相互作用和多性状位点关联性分析等子问题. 相似文献
985.
In this paper, the empirical Bayes (EB) two-sided test for parameter of Cox models is investigated under square loss functions. At first by using recursive kernel estimation of probability function the empirical Bayes two-sided test rule is constructed. It proves that the proposed empirical Bayes test rule is asymptotic optimal and convergence rates are obtained under suitable conditions. Finally an example of satisfying theorem conditions is given. 相似文献
986.
987.
Prof. Dr. Jörg Grunenberg 《Angewandte Chemie (International ed. in English)》2017,56(25):7288-7291
The first quantum-mechanical calculations of all relevant potential constants in both the iron-molybdenum cofactor and the iron-vanadium cofactor of nitrogenase suggest that the carbide is bound to the center of the enzyme much more strongly than hitherto assumed. Previous studies seemed to indicate a dummy function of the interstitial carbon, with a weak force constant (ca. 0.32 N cm−1). Our new investigations confirm a different picture: the central carbon atom binds the iron-sulfur cluster through six covalent C−Fe bonds. With a potential constant of more than 1.3 N cm−1, the interstitial carbon also appears to be dynamically persistent. According to our investigations, the values for the elasticity within the iron-sulfur cluster have to be corrected too. These new details on the mechano-chemical properties of the FeMo cofactor will be important for elucidating the catalytic cycle of nitrogen fixation. By implementing our new algorithm in the freely available COMPLIANCE program, the dependence on the coordinates during the calculation of Hesse matrices is eliminated completely. 相似文献
988.
Calin Iulian Martin 《Applicable analysis》2017,96(7):1207-1214
This paper is concerned with the governing equations (together with the free boundary and the bottom boundary conditions) for an inviscid, incompressible fluid, written in spherical coordinates which are fixed at a point on the rotating Earth. For a special type of a steady flow moving only in the azimuthal direction, with no variation in this direction, we provide a functional-analytic study of the link between the pressure at the free surface of the ocean and the distortion of that surface. 相似文献
989.
990.
本文讨论了高次杂交壳体元在材料非线性分析中的应用,为了更精确估计单元内各部分应力的不同影响,本文应用了分区非线性变分原理推导出杂交壳元在应力增量下应用初始应力法的失衡节点力,这使得高次杂交元在非线性分析中的优点得以充分的发挥,从而大大提高了计算精度。 相似文献