全文获取类型
收费全文 | 1096篇 |
免费 | 23篇 |
国内免费 | 6篇 |
专业分类
化学 | 802篇 |
晶体学 | 7篇 |
力学 | 22篇 |
数学 | 44篇 |
物理学 | 250篇 |
出版年
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 8篇 |
2016年 | 8篇 |
2015年 | 29篇 |
2014年 | 17篇 |
2013年 | 43篇 |
2012年 | 37篇 |
2011年 | 38篇 |
2010年 | 41篇 |
2009年 | 25篇 |
2008年 | 50篇 |
2007年 | 51篇 |
2006年 | 40篇 |
2005年 | 44篇 |
2004年 | 32篇 |
2003年 | 36篇 |
2002年 | 25篇 |
2001年 | 28篇 |
2000年 | 36篇 |
1999年 | 14篇 |
1998年 | 7篇 |
1997年 | 12篇 |
1996年 | 9篇 |
1995年 | 11篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 14篇 |
1989年 | 29篇 |
1988年 | 24篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 37篇 |
1984年 | 17篇 |
1983年 | 16篇 |
1982年 | 20篇 |
1981年 | 29篇 |
1980年 | 20篇 |
1979年 | 22篇 |
1978年 | 15篇 |
1977年 | 23篇 |
1976年 | 26篇 |
1975年 | 27篇 |
1974年 | 12篇 |
1973年 | 9篇 |
1969年 | 6篇 |
1965年 | 4篇 |
排序方式: 共有1125条查询结果,搜索用时 15 毫秒
121.
Hiroko Nakagawa Kumiko Ohtsuka Katsuhito Sugahara Chika Kobayashi Yuichi Masuoka Koh-ichi Yamada Masami Kawase 《Tetrahedron: Asymmetry》2010,21(6):659-664
Helical [5]thiaheterohelicene 5HM, which rapidly interconverts between P and M enantiomers in solution, was connected to helical l-phenylalanine oligomers with an ester linkage to give peptidehelicenes (5Fn, where n: number of bonded phenylalanines). The characteristics of 5F4 and 5F5 with two types of helixes in a molecule were investigated, particularly in comparison with those of 5F1–5F3 with an incomplete coil of a peptide moiety. l-Phenylalanine peptide chains induced a shift in the equilibrium between the P and M helixes of 5HM toward the P side for all the 5Fns examined. The enantiomeric excess (ee) of the P form increased with a decrease in temperature, together with an elongation of the peptide chains. 5F4 and 5F5 in hot solutions of some solvents formed a gel at room temperature, whereas 5F1–5F3 showed no such behavior. In this gel, the stable helical form of the 5HM moiety in 5F4 and 5F5 was observed to be the M form in contrast to that in their solutions. 相似文献
122.
123.
Masashi Shiotsuki Atsushi Nakagawa Jesus Rodriguez Castañon Naoya Onishi Tatsurou Kobayashi Fumio Sanda Toshio Masuda 《Journal of polymer science. Part A, Polymer chemistry》2010,48(23):5549-5556
End‐functionalized poly(phenylacetylene)s were synthesized by the polymerization of phenylacetylene (PA) using the well‐defined palladium catalysts represented as [(dppf)PdBr(R)] {dppf = 1,1′‐bis(diphenylphosphino)ferrocene}. The Pd catalysts having a series of R groups such as o‐tolyl, mesityl, C(Ph)?CPh2, C6H4‐o‐CH2OH, C6H4‐p‐CN, and C6H4‐p‐NO2 in conjunction with silver triflate polymerized PA to give end‐functionalized poly(PA)s bearing the corresponding R groups in high yields. The results of IR and NMR spectroscopies and MALDI‐TOF mass analyses proved the introduction of these R groups at one end of each polymer chain. The poly(PA) bearing a hydroxy end group was applied as a macroinitiator to the synthesis of a block copolymer composed of poly(PA) and poly(β‐propiolactone) moieties. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
124.
Suppose that in the final stage of manufacturing of, for instance, chemical products, there is a process in which we weigh each product using a scale to obtain its exact weight, and then mark each product with its weight. In practice, such a weighing process is not necessarily carefully checked and its associated cost is reduced as much as possible since it does not affect the product quality itself. However, the scale occasionally becomes uncalibrated, that is, inaccurate, and hence will produce inaccurate weights for individual products. Particularly when the products are very heavy, a special scale is used and only qualified persons with licenses can inspect the scale to detect its inaccuracy and adjust it. We focus on a problem of this sort and propose a stochastic model aiming to control the volume of products shipped out with inaccurate marked weights. 相似文献
125.
126.
L. Gillo S. E. Golbreich T. Nagoshi I. Nakagawa C. S. Piper W. C. Campbell Marion I. Hanna L. Palfray C. Rocchi R. del Monte R. Lechner M. Roß L. A. Ynalvez H. Lecoq Th. A. G. Haanappel Thérèse Jullig J. Barbière A. Lecco L. Lilic P. M. Heertjes 《Analytical and bioanalytical chemistry》1943,125(3-4):133-137
127.
The effects of bredinin on the primary culture of fetal mouse cells (fetal cells) and adult mouse lung cells (lung cells) were compared. Bredinin inhibited the growth of both cells, and this inhibition was found to be caused, at least in part, by the inhibition of the S phase and/or the transition from the G1 to S phase of the cell cycle. Bredinin inhibited both DNA and RNA synthesis without affecting protein synthesis. However, the inhibitory effect of bredinin differed between the two cell lines; the fetal cells were more sensitive than the lung cells, and bredinin inhibited DNA synthesis 100 times more potently in the fetal cells. The inhibition of DNA synthesis by bredinin in the fetal cells was gradually lowered by in vitro aging of the fetal cells to a level similar to that in the lung cells. There was no difference in the rate of incorporation of bredinin into the cells between the fetal cells and the lung cells. When fetal tissue was used as an enzyme source, bredinin was converted to bredinin 5'-monophosphate (BMP), but when lung tissue was used, bredinin was not converted. This is in agreement with the finding that bredinin has selective toxicity on fetuses in vivo but is hardly toxic to adult cells, which suggests the involvement of BMP in the selective toxicity of bredinin on the fetus. 相似文献
128.
129.
This paper considers the following charging policy for a battery to back up memories of a computer system: If the voltage of a battery is lower than a prespecified threshold level when the power is on, a battery is charged for a fixed time T. Using the probability theory, an availability of the system is derived and an optimal time T* to maximize it is discussed. A numerical example is finally given. 相似文献
130.
The empirical energy parameters for a calcium ion and its ligands in proteins were determined within a pairwise additive framework. The interaction energies of Ca2+-water, Ca2+-peptide group and Ca2+-carboxyl group systems were calculated using the ab initio molecular orbital method with basis sets of double zeta quality including polarization or diffuse functions. The resulting potential energy surfaces served as references for the determination of the nonbonded parameters in the empirical energy function. The nonadditive corrections for the Ca2+-ligand pair potentials are incorporated implicitly in the nonbonded paremeters by treating three-body (1:2 complex) or seven-body (1:6 complex) systems in reference calculations. Ligand polarizations induced by Ca2+ are estimated from the partial atomic charges of two-body (1:1 complex) systems. The charge sets were determined by scaling so as to reproduce the reference potential energy surfaces. The newly determined parameter set was used in a stochastic boundary molecular dynamics simulation of phospholipase A2. The solvated structure of the Ca2+-binding site obtained from an X-ray crystallographic study is well reproduced by the parameter set. 相似文献