全文获取类型
收费全文 | 1045篇 |
免费 | 24篇 |
国内免费 | 11篇 |
专业分类
化学 | 696篇 |
晶体学 | 13篇 |
力学 | 8篇 |
数学 | 88篇 |
物理学 | 275篇 |
出版年
2021年 | 11篇 |
2020年 | 9篇 |
2019年 | 15篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 20篇 |
2015年 | 10篇 |
2014年 | 20篇 |
2013年 | 50篇 |
2012年 | 50篇 |
2011年 | 67篇 |
2010年 | 31篇 |
2009年 | 34篇 |
2008年 | 61篇 |
2007年 | 56篇 |
2006年 | 61篇 |
2005年 | 58篇 |
2004年 | 43篇 |
2003年 | 62篇 |
2002年 | 39篇 |
2001年 | 25篇 |
2000年 | 35篇 |
1999年 | 14篇 |
1998年 | 17篇 |
1997年 | 13篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 5篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1972年 | 11篇 |
排序方式: 共有1080条查询结果,搜索用时 296 毫秒
1.
2.
Using a single variable theta identity, which is similar to the Jacobi Triple Product identity, we produce the generating functions for values of certain expressions of Hurwitz zeta functions at non-positive integers. 相似文献
3.
We have investigated the spin-1 Ising model on the simple cubic lattice with bilinear, biquadratic interaction and anisotropic energy (BEG model). We have been specially interested in the case of antiferro biquadratic interaction, because the interaction will cause the competition with bilinear interaction and anisotropy. A two-sublattice ordering, so called the staggered quadrupole (SQ) phase, occurs as long as biquadratic interaction is negative large enough. We have obtained a full phase diagram in the whole interaction parameter space (for the positive bilinear interaction) by the Bethe approximation, and found several kinds of phase transitions, such as successive, re-entrant and double re-entrant transitions. These transitions are also confirmed by Monte Carlo simulations on simple cubic lattices. 相似文献
4.
Ken Ono 《Mathematische Annalen》1998,312(2):251-260
5.
T Kusama T Soga Y Ono E Kumazawa E Shioya Y Osada S Kusumoto T Shiba 《Chemical & pharmaceutical bulletin》1991,39(8):1994-1999
Two novel analogs of a biosynthetic precursor of lipid A (2) were synthesized. The one analog (3) has acyl groups identical to those of 2, and the other (4) has tetradecanoyl groups in place of the (R)-3-hydroxytetradecanoyl groups of 2. Both 3 and 4 possess an alpha-glycosidically-bound phosphonooxyethyl group in place of the alpha-glycosyl phosphate group of 2. Compounds 3 and 4 exhibited definite antitumor activity against Meth A fibrosarcoma and low toxicity in rabbits, as the original compound 2 does. The replacement of the hydroxytetradecanoyl groups with tetradecanoyl groups barely affected the antitumor activity, but slightly enhanced the toxicity in rabbits. 相似文献
6.
7.
8.
Yoshitomo Ono Naoyuki Kawashima Hiroto Kudo Tadatomi Nishikubo Takabumi Nagai 《Journal of polymer science. Part A, Polymer chemistry》2007,45(14):2978-2988
The ring‐opening copolymerization of a glycidyl ester derivative having a benzophenone group and the donor–acceptor norbornadiene (D‐A NBD) dicarboxylic acid, 5‐(4‐methoxyphenyl)‐1,4,6,7,7‐pentamethyl‐2,5‐norbornadiene‐2,3‐dicarboxylic acid, monoglycidyl ester derivatives with D‐A NBD dicarboxylic anhydride using tetraphenylphosphonium bromide as a catalyst proceeded smoothly to give novel self‐photosensitizing NBD polymers in good yields. The molecular weight of these polyesters was about 4,000, and lower than that of analogous NBD polymers having no benzophenone group. All the synthesized NBD polymers isomerized smoothly to the corresponding quadricyclane (QC) polymers upon UV irradiation in tetrahydrofuran (THF) solution and in the film state. The rate of the photoisomerization of the D‐A NBD moieties in these polymers was higher than that of the D‐A NBD moieties in the polymer having no photosensitizing group. Furthermore, the rate of the photoisomerization of the D‐A NBD moieties in these polymers was also higher than that of the NBD polymer with low molecular weight photosensitizer in dilute solution. The photo‐irradiated polymers having QC moieties released thermal energies of 146–180 J/g. The D‐A NBD moieties contained in these NBD polymers possessed fair to good fatigue resistance. The degradation of the NBD moieties in these polymers was 15–30% after 50 repeated cycles of interconversion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2978–2988, 2007 相似文献
9.
Thi Thi Nge Naruhito Hori Akio Takemura Hirokuni Ono Tsunehisa Kimura 《Journal of Polymer Science.Polymer Physics》2003,41(7):711-714
A high magnetic field of 5 T was used to fabricate a magnetically aligned, optically anisotropic, liquid‐crystalline chitin/poly(acrylic acid) composite. The aligned mesophase was fixed by photoinitiated free‐radical polymerization. From an examination of polarized optical micrographs and an X‐ray diffraction study, a high degree of orientation of 0.70 was observed for the composite with a higher liquid‐crystalline chitin concentration (10.70 wt %); the orientation was reduced with a decreased chitin concentration at a given acrylic acid concentration. The X‐ray data for the developed composite showed a uniplanar orientation for the chitin crystallites, with its molecular long axes perpendicular to the direction of the magnetic field. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 711–714, 2003 相似文献
10.
Makoto Kume Atsunori Hirano Bungo Ochiai Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2006,44(11):3666-3673
A spiro orthoester with an exomethylene group (exoSOE) was radically copolymerized with acrylonitrile or vinyl acetate at several feed ratios to obtain the corresponding copolymers having spiro orthoester moieties in the side chain. The obtained copolymers could be crosslinked via the double ring‐opening polymerization of the spiro orthoester moieties in their side chain by a treatment with BF3OEt2. The volume changes upon the crosslinking of the copolymers were evaluated by density measurements with a micromeritics gas pycnometer. The copolymers experienced less than 1% volume expansion instead of volume shrinkage during typical cationic crosslinking, regardless of the copolymer compositions. Negligible shrinkage was observed during the thermal cationic crosslinking of a film cast from a nitrobenzene solution of the copolymers containing a benzylthiophenium salt as a thermally latent cationic initiator. The constantly low volume changes during the crosslinking of the copolymers from exoSOE probably depended on the almost zero volume change during the cationic polymerizations of spiro orthoester derivatives. This indicates that exoSOE is an effective monomer for crosslinkable polymers without volume changes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3666–3673, 2006 相似文献