全文获取类型
收费全文 | 9947篇 |
免费 | 167篇 |
国内免费 | 19篇 |
专业分类
化学 | 6715篇 |
晶体学 | 94篇 |
力学 | 145篇 |
数学 | 1234篇 |
物理学 | 1945篇 |
出版年
2019年 | 74篇 |
2016年 | 125篇 |
2015年 | 104篇 |
2014年 | 144篇 |
2013年 | 331篇 |
2012年 | 213篇 |
2011年 | 313篇 |
2010年 | 218篇 |
2009年 | 174篇 |
2008年 | 281篇 |
2007年 | 277篇 |
2006年 | 272篇 |
2005年 | 289篇 |
2004年 | 261篇 |
2003年 | 228篇 |
2002年 | 206篇 |
2001年 | 172篇 |
2000年 | 163篇 |
1999年 | 137篇 |
1998年 | 101篇 |
1997年 | 108篇 |
1996年 | 128篇 |
1995年 | 154篇 |
1994年 | 139篇 |
1993年 | 178篇 |
1992年 | 136篇 |
1991年 | 114篇 |
1990年 | 111篇 |
1989年 | 129篇 |
1988年 | 124篇 |
1987年 | 147篇 |
1986年 | 129篇 |
1985年 | 146篇 |
1984年 | 145篇 |
1983年 | 148篇 |
1982年 | 127篇 |
1981年 | 138篇 |
1980年 | 134篇 |
1979年 | 133篇 |
1978年 | 152篇 |
1977年 | 102篇 |
1976年 | 150篇 |
1975年 | 130篇 |
1974年 | 102篇 |
1973年 | 117篇 |
1972年 | 76篇 |
1971年 | 76篇 |
1970年 | 62篇 |
1967年 | 62篇 |
1966年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Enantiomeric Cyclic Peptides with Different Caco‐2 Permeability Suggest Carrier‐Mediated Transport 下载免费PDF全文
B. Sc. Eduard Puig Prof. Dr. Beat Ernst Prof. Dr. Horst Kessler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8023-8027
Recently, oral absorption of cyclic hexapeptides was improved by N‐methylation of their backbone amides. However, the number and position of N‐methylations or of solvent exposed NHs did not correlate to intestinal permeability, measured in a Caco‐2 model. In this study, we investigate enantiomeric pairs of three polar and two lipophilic peptides to demonstrate the participation of carrier‐mediated transporters. As expected, all the enantiomeric peptides exhibited identical lipophilicity (logD7.4) and passive transcellular permeability determined by the parallel artificial membrane permeability assay (PAMPA). However, the enantiomeric polar peptides exhibited different Caco‐2 permeability (Papp) in both directions a–b and b–a. The same trend was observed for one of the lipophilic peptide, whereas the second lipophilic enantiomer pair showed identical Caco‐2 permeability (within the errors). These findings provide the first evidence for the involvement of carrier‐mediated transport for peptides, especially for those of polar nature. 相似文献
2.
We have recently demonstrated that polarization transfer using an adiabatic passage through the Hartmann-Hahn condition (APHH-CP) by a variation of the radio-frequency amplitude can substantially improve the transfer efficiency over Hartmann-Hahn cross polarization. Here we show that APHH-CP can be combined with fast magic angle sample spinning (MAS). The heteronuclear dipolar order, established in the course of the transfer, can indeed be created and preserved. 相似文献
3.
J. E. Fischer E. Werwa P. A. Heiney 《Applied Physics A: Materials Science & Processing》1993,56(3):193-196
We have used both reflection-geometry and grazing-incidence-geometry X-ray scattering to study thin films of C60 evaporated onto mica substrates via a hot-wall technique. The growth mode yields close-packed C60 planes, which are parallel to the substrate surface and which exhibit out-of-plane correlation lengths of 850 Å. In the film plane the C60 is at best pseudo-epitaxial, with a 0.9° distribution of crystallite orientations, a 450 Å in-plane correlation length, and a 3.7% lattice mismatch, better than obtained by other thin film techniques but far from the accepted definition of single crystal thin film epitaxy. 相似文献
4.
5.
6.
7.
C. Mattea N. Fatkullin E. Fischer U. Beginn E. Anoardo M. Kroutieva R. Kimmich 《Applied magnetic resonance》2004,27(3-4):371-381
Linear polyethylene oxides with molecular weightsM w of 1665 and 10170 confined in pores with variable diameters in a solid methacrylate matrix were studied by proton field-cycling nuclear magnetic resonance relaxometry. The pore diameter was varied in the range of 9–57 nm. In all cases, the spin-lattice relaxation time shows a frequency dependence close toT 1∞ v3/4 in the range ofv=3·10?1-2·101 MHz as predicted by the tube-reptation model. This protonT 1 dispersion essentially reproduces that found in a previous deuteron study (R. Kimmich, R.-O. Seitter, U. Beginn, M. Möller, N. Fatkullin: Chem. Phys. Lett. 307, 147, 1999). As a feature particularly characteristic for reptation, this finding suggests that reptation is the dominating chain dynamics mechanism under pore confinement in the corresponding time range. The absolute values of the spin-lattice relaxation times indicate that the diameter of the effective tubes in which reptation occurs is much smaller than the pore diameters on the time scale of spin-lattice relaxation experimens. An estimation leads to a valued *~0.5 nm. The impenetrability of the solid pore walls, the uncrossability of polymer chains (“excluded volume”) and the low value of the compressibility in polymer melts create the “corset effect” which reduces the lateral motions of polymer chains to a microscopic scale of only a few tenths of a nanometer. 相似文献
8.
Ernst Junker 《Colloid and polymer science》1941,95(2):213-250
Ohne ZusammenfassungMeinem verehrten Lehrer, Herrn Prof. Dr. H. Pallmann — auf dessen Anregung diese Arbeit ausgeführt würde — möchte ich für die mir zuteil gewordene Förderung und die wertvollen Ratschläge bestens danken. 相似文献
9.
Worm Müller Jac G. Otto Arno Behr und O. Hesse 《Fresenius' Journal of Analytical Chemistry》1884,23(1):82-85
Ohne Zusammenfassung 相似文献
10.
S. Vogel J. Hutter T. H. Fischer H. P. Lüthi 《International journal of quantum chemistry》1993,45(6):665-678
A program to optimize the structure of large molecules at the Hartree–Fock level of theory running concurrently on a network of workstations is presented. Problems encountered in obtaining nearly optimal speedup and their solutions are discussed. A simple scheduling algorithm is presented that enables up to 99.5% of the code to run in parallel. © 1993 John Wiley & Sons, Inc. 相似文献