全文获取类型
收费全文 | 2597篇 |
免费 | 47篇 |
国内免费 | 19篇 |
专业分类
化学 | 1982篇 |
晶体学 | 21篇 |
力学 | 28篇 |
数学 | 166篇 |
物理学 | 466篇 |
出版年
2021年 | 15篇 |
2020年 | 18篇 |
2019年 | 21篇 |
2018年 | 17篇 |
2017年 | 17篇 |
2016年 | 31篇 |
2015年 | 16篇 |
2014年 | 35篇 |
2013年 | 118篇 |
2012年 | 92篇 |
2011年 | 135篇 |
2010年 | 70篇 |
2009年 | 72篇 |
2008年 | 125篇 |
2007年 | 132篇 |
2006年 | 149篇 |
2005年 | 144篇 |
2004年 | 132篇 |
2003年 | 116篇 |
2002年 | 108篇 |
2001年 | 41篇 |
2000年 | 63篇 |
1999年 | 38篇 |
1998年 | 39篇 |
1997年 | 31篇 |
1996年 | 27篇 |
1995年 | 26篇 |
1994年 | 30篇 |
1993年 | 25篇 |
1992年 | 26篇 |
1991年 | 30篇 |
1990年 | 24篇 |
1989年 | 22篇 |
1988年 | 36篇 |
1987年 | 30篇 |
1986年 | 25篇 |
1985年 | 48篇 |
1984年 | 47篇 |
1983年 | 23篇 |
1982年 | 45篇 |
1981年 | 65篇 |
1980年 | 46篇 |
1979年 | 39篇 |
1978年 | 38篇 |
1977年 | 33篇 |
1976年 | 36篇 |
1975年 | 29篇 |
1974年 | 37篇 |
1973年 | 28篇 |
1972年 | 16篇 |
排序方式: 共有2663条查询结果,搜索用时 31 毫秒
1.
Inside Cover: Photoinduced Formation of an Azobenzene‐Based CD‐Active Supramolecular Cyclic Dimer (Chem. Eur. J. 18/2015)
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
2.
3.
Yong Lee Kazuhiko Hosomi Hiroyuki Uchiyama Toshio Katsuyama Shinya Kominami Tomoyoshi Mishima 《Optical Review》2003,10(1):38-42
An InGaAsP slab-type asymmetric-coupled-waveguide-based dispersion compensator with a mode selector has been designed and fabricated. The mode selector is necessary to select either a symmetric [with a positive group-velocity dispersion (GVD)] or antisymmetric (with a negative GVD) supermode. These supermodes exist simultaneously in the dispersion-compensation region of the device. Pulse-compression experiments were used to test the dispersion compensator, evaluating the function of the mode selector. A theoretical study of the experimental results shows that the mode selector obtains a very strong selectivity (nearly 100%) for the antisymmetric supermode. 相似文献
4.
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
5.
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
6.
Ken Ono 《Mathematische Annalen》1998,312(2):251-260
7.
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
8.
Yoshinori Nishiwaki Masahiko Shimoyama Toshio Nakanishi Toshio Ninomiya Izumi Nakai 《Analytical sciences》2006,22(10):1297-1300
Total reflection X-ray fluorescence spectrometry (TXRF) has been applied for trace elemental analysis of small glass fragments. A small glass sample (a fragment with weight less than 0.5 mg) was decomposed by 100 microg of HF/HNO3 acid; the material was condensed to 10 microl and was dried on a Si wafer. Since the size of the dried residue on the Si wafer was less than 1 cm in diameter, an incident X-ray beam with about 1 cm in width could effectively excite elemental components in such a small glass fragment. The precision of the present technique was checked by analyzing the glass fragments (<0.5 mg) from NIST SRM612; the relative standard deviations (RSD) of less than 8.1% were achieved for elemental ratios that were normalized by Sr. Fragments (<0.5 mg) obtained from 23 figured sheet glasses were used as samples for estimating the utility of this technique to forensic discrimination. Comparison of five elemental ratios of Ti/Sr, Mn/Sr, Zn/Sr, Rb/Sr, and Pb/Sr calculated from X-ray fluorescence spectra was effective in distinguishing glass fragments that could not be differentiated by their refractive indexes (RI). 相似文献
9.
Yamada Kaoru Matsutani Shigeaki Uchiyama Akira Takahashi Toshio 《Journal of inclusion phenomena and macrocyclic chemistry》1991,11(1):49-54
Analyses of crown ether complexes of alkali metal ions and characterization of the complexes formed inm-nitrobenzyl alcohol have been carried out by fast atom bombardment (FAB) mass spectrometry. By using m-nitrobenzyl alcohol as a matrix for measurements, the stoichiometry of the complexes was assessed on the basis of the observed FAB peaks. In addition, the formation of crown ether-alkali metal complexes at a 2 : 1 molar ratio was enhanced by increasing the ionic radius of the metal ion in agreement with previous observations. On these grounds, FAB mass spectrometry may provide a rapid means for investigation of the complexation behavior of crown ethers and the stoichiometry of the complexes. 相似文献
10.