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141.
胶原蛋白的三股螺旋结构是其不同于其他蛋白质的特殊结构,也是其具有特殊功能的基础,然而,胶原的三股螺旋结构易在外界条件的影响下被破坏。目前微波已被越来越多的应用于胶原蛋白的提取和改性过程,但是关于微波辐照对胶原蛋白结构影响的研究还相对较少。首先从牛跟腱中提取胶原蛋白,然后采用0.5 mg·mL-1的胶原蛋白溶液在30 ℃下以微波辐照保温为实验样,水浴加热和未经加热处理为对比样,最后采用紫外-可见光谱、傅里叶变换红外光谱、圆二色谱以及荧光发射光谱等方法,对不同加热方法中胶原蛋白的三股螺旋结构和超分子结构进行表征,研究了微波辐照对胶原蛋白结构的影响。实验结果表明,在低于胶原变性温度的条件下,无论是微波辐照还是水浴加热都不会破坏胶原蛋白的三股螺旋结构,也不会使胶原蛋白变性。但是,与水浴加热相比,微波辐照会对胶原蛋白的聚集行为产生抑制作用。微波辐照对胶原蛋白的作用既有与常规加热相同的热效应,又有常规加热过程中不存在的非热效应,非热效应表现为抑制胶原蛋白的聚集行为。研究结果可为微波场中胶原蛋白结构和性质的变化提供科学依据。 相似文献
142.
空间圆柱螺旋线的NURBS表示 总被引:4,自引:0,他引:4
O.引言用B样条方法或B6zier方法来表示自由曲线、曲面,是在CAD/CAM技术中广泛使用的数学手段.但是由于它们都不能精确地表示除抛物线或抛物面以外的圆锥曲线与初等二次曲面,因此近年来,另一种形式的参数样条-一参数有理多项式方法占据了主导地位.非均匀有理B样条(简称NURBS)已被国际标准组织(ISO)于1991年正式颁布为关于工业产品几何定义的STEP国际标准,将其作为定义产品形状的唯一数学方法.越来越多的CAD系统采用NURBS曲线与曲面来建立图形库,研究各种曲线与曲面的NURBS表示无疑是很有意义的.在描述圆锥曲线… 相似文献
143.
Proline residues in helices play an important role in the structure of proteins. The proline residue introduces a kink in
the helix which varies from about 5° to 50°. The presence of other residues such as threonine or valine near the proline region
can influence the flexibility exhibited by the kinked helix, which can have an important biological role. In the present paper,
the constraint introduced by threonine and valine on a proline helix is investigated by molecular dynamics studies. The systems
considered are (1) a poly-alanine helix with threonine-proline residues (TP) and (2) a poly-alanine helix with valine-threonineproline
residues (VTP), in the middle. Molecular dynamics simulations are carried out on these two systems for500 ps. The results are analyzed in terms of structural transitions, bend-related parameters and sidechain orientations. 相似文献
144.
Muthusamy Sivakumar K.P.O. Mahesh Yusuke Yamamoto Hiroaki Yoshimizu Yoshiharu Tsujita 《Journal of Polymer Science.Polymer Physics》2005,43(14):1873-1880
Syndiotactic polystyrene (sPS) membranes were prepared with different organic solvent systems and compared to get the information about the δ‐form complexing behavior of sPS. Further, the guest molecules included in the clathrate δ form of sPS are removed by stepwise extraction method. The conformational changes during the TTGG helical formation of sPS/organic solvent systems have been identified by FTIR spectroscopy, and it was concluded that the TTGG helices were constructed in regular sequences, which depends on the nature of the respective solvents. The TTGG content in the mesophase is found to be increased by removing the guest molecules. The structural changes of sPS/organic solvent systems have been characterized by WAXD analysis. Moreover, the different clathrate structures were found and showed the different crystalline reflections in the WAXD profiles, which are significantly changed with the kind of guest solvent included in sPS. The content of solvents in the clathrated sPS and the desorption temperatures were determined by thermal analysis. The resulted mesophase of sPS membrane contains the nanoporous molecular cavities that depend on the size of the guest molecule. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1873–1880, 2005 相似文献
145.
146.
Hai-Ling Wang Zhong-Hong Zhu Xiong-Feng Ma Dr. Hua-Hong Zou Prof. Fu-Pei Liang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(46):10813-10817
Metal nanoclusters have a certain rigidity due to their specific coordination patterns and shapes; thus, they face extreme difficulty in folding into a specific direction to form a double-helix structure and in further interconnecting to form metal–helix frameworks (MHFs). To date, no MHFs have been produced by the formation of heterometallic clusters. Selecting the appropriate “bonding molecules” to bond metal nanoclusters in a specific multiple direction is one of the most effective strategies for designing synthetic MHFs. In this study, we realized for the first time the control of different orientations of μ3-NO3− to join heterometallic clusters (Cu10Dy2) and subsequently form a left-handed double helix chain, which further joins to form MHFs. In the structure of the MHFs, four different directions of bridging μ3-NO3− exist, three of which are involved in the linkage of the double-helix chain. Each μ3-NO3− is connected to three adjacent Cu10Dy2. Herein, we extend a new method for designing synthetic double-helix structures and MHFs, thereby further laying the foundation for the development of similar DNA double-helix structures and nucleic acid secondary structures in vitro. 相似文献
147.
148.
149.
Antonio J. Di Scala 《Abhandlungen aus dem Mathematischen Seminar der Universit?t Hamburg》2009,79(1):37-46
Let M⊂ℝ
n
be a submanifold of a euclidean space. A vector d∈ℝ
n
is called a helix direction of M if the angle between d and any tangent space T
p
M is constant. Let ℋ(M) be the set of helix directions of M. If the set ℋ(M) contains r linearly independent vectors we say that M is a weak r-helix. We say that M is a strong r-helix if ℋ(M) is a r-dimensional linear subspace of ℝ
n
. For curves and hypersurfaces both definitions agree. The object of this article is to show that these definitions are not
equivalent. Namely, we construct (non strong) weak 2-helix surfaces of ℝ4.
The author is supported by the Project M.I.U.R. “Riemann Metrics and Differentiable Manifolds” and by G.N.S.A.G.A. of I.N.d.A.M.,
Italy. 相似文献
150.
Yoshio Furusho Eiji Yashima 《Journal of polymer science. Part A, Polymer chemistry》2009,47(20):5195-5207
There is growing interest in the design and synthesis of artificial helical polymers and oligomers, in connection with biological importance as well as development of novel chiral materials. Since the discovery of the helical structure of isotactic polypropylene, a significant advancement has been achieved for synthetic polymers and oligomers with a single helical conformation for about half a century. In contrast, the chemistry of double helical counterparts is still premature. This short review highlights the recent advances in the synthesis, structures, and functions of double helical polymers and oligomers, featuring an important role of supramolecular chemistry in the design and synthesis of double helices. Although the artificial double helices reported to date are still limited in number, recent advancement of supramolecular chemistry provides plenty of structural motifs for new designs. Therefore, artificial double helices hold great promise as a new class of compounds. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5195–5207, 2009 相似文献