全文获取类型
收费全文 | 1288篇 |
免费 | 59篇 |
国内免费 | 4篇 |
专业分类
化学 | 1074篇 |
晶体学 | 10篇 |
力学 | 12篇 |
数学 | 77篇 |
物理学 | 178篇 |
出版年
2023年 | 10篇 |
2022年 | 10篇 |
2021年 | 20篇 |
2020年 | 26篇 |
2019年 | 32篇 |
2018年 | 22篇 |
2017年 | 16篇 |
2016年 | 38篇 |
2015年 | 41篇 |
2014年 | 40篇 |
2013年 | 47篇 |
2012年 | 90篇 |
2011年 | 110篇 |
2010年 | 69篇 |
2009年 | 50篇 |
2008年 | 58篇 |
2007年 | 87篇 |
2006年 | 85篇 |
2005年 | 70篇 |
2004年 | 51篇 |
2003年 | 67篇 |
2002年 | 60篇 |
2001年 | 20篇 |
2000年 | 13篇 |
1999年 | 19篇 |
1998年 | 7篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 16篇 |
1994年 | 14篇 |
1993年 | 7篇 |
1992年 | 12篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1973年 | 5篇 |
1968年 | 2篇 |
排序方式: 共有1351条查询结果,搜索用时 31 毫秒
41.
S Murayama B Su K Okabe A Kishimura K Osada M Miura T Funatsu K Kataoka M Kato 《Chemical communications (Cambridge, England)》2012,48(67):8380-8382
We developed a simple preparation procedure for the protein encapsulated nanoparticle and used the nanoparticle for spatiotemporal activity control of various proteins. We succeeded in the local protein activation within cells by light using the nanoparticle. 相似文献
42.
Abstract The primary structure of an elicitor-active oligosaccharide, LN-3, prepared from partially hydrolyzed algal laminaran was determined by means of the analyses of glycosyl-linkage, fragments by acetolysis, and glycosyl-sequence. The elicitor-active oligosaccharide, LN-3, is a pyridylaminated hepta-β-d-glucoside which was shown to have the following linear structure: β-d-Glcp(1→6)-β-d-Glcp(1→3)-β-d-Glcp(1→3)-β-d-Glcp(1→3)-β-d-Glcp(1→6)-β-d-Glcp(1→3)-Glc-PA. 相似文献
43.
44.
Carbon dioxide fixation by microalgae photosynthesis using actual flue gas discharged from a boiler 总被引:2,自引:0,他引:2
Matsumoto Hiroyo Shioji Norio Hamasaki Akihiro Ikuta Yoshiaki Fukuda Yoshinori Sato Minoru Endo Noriyoshi Tsukamoto Toshiaki 《Applied biochemistry and biotechnology》1995,(1):681-692
To mitigate CO2 discharged from thermal power plants, studies on CO2 fixation by the photosynthesis of microalgae using actual exhaust gas have been carried out. The results are as follows.
相似文献
1. | A method is proposed for evaluating the maximum photosynthesis rate in the raceway cultivator using only the algal physical properties; |
2. | Outdoor cultivation tests taking actual flue gas were performed with no trouble or break throughout 1 yr using the strain collected in the test; |
3. | The produced microalgae is effective as solid fuel; and |
4. | The feasibility studies of this system were performed. The system required large land area, but the area is smaller than that required for other biomass systems, such as tree farms. |
45.
Tsuzuki S Wakisaka A Ono T Sonoda T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(3):951-960
The geometries and interaction energies of complexes of pyridine with C6F5X, C6H5X (X=I, Br, Cl, F and H) and RFI (RF=CF3, C2F5 and C3F7) have been studied by ab initio molecular orbital calculations. The CCSD(T) interaction energies (Eint) for the C6F5X–pyridine (X=I, Br, Cl, F and H) complexes at the basis set limit were estimated to be ?5.59, ?4.06, ?2.78, ?0.19 and ?4.37 kcal mol?1, respectively, whereas the Eint values for the C6H5X–pyridine (X=I, Br, Cl and H) complexes were estimated to be ?3.27, ?2.17, ?1.23 and ?1.78 kcal mol?1, respectively. Electrostatic interactions are the cause of the halogen dependence of the interaction energies and the enhancement of the attraction by the fluorine atoms in C6F5X. The values of Eint estimated for the RFI–pyridine (RF=CF3, C2F5 and C3F7) complexes (?5.14, ?5.38 and ?5.44 kcal mol?1, respectively) are close to that for the C6F5I–pyridine complex. Electrostatic interactions are the major source of the attraction in the strong halogen bond although induction and dispersion interactions also contribute to the attraction. Short‐range (charge‐transfer) interactions do not contribute significantly to the attraction. The magnitude of the directionality of the halogen bond correlates with the magnitude of the attraction. Electrostatic interactions are mainly responsible for the directionality of the halogen bond. The directionality of halogen bonds involving iodine and bromine is high, whereas that of chlorine is low and that of fluorine is negligible. The directionality of the halogen bonds in the C6F5I– and C2F5I–pyridine complexes is higher than that in the hydrogen bonds in the water dimer and water–formaldehyde complex. The calculations suggest that the C? I and C? Br halogen bonds play an important role in controlling the structures of molecular assemblies, that the C? Cl bonds play a less important role and that C? F bonds have a negligible impact. 相似文献
46.
Watanabe J Oki T Takebayashi J Yamasaki K Takano-Ishikawa Y Hino A Yasui A 《Analytical sciences》2012,28(2):159-165
Hydrophilic oxygen radical absorbance capacity (H-ORAC) is a method for evaluating antioxidant capacities of solutions of hydrophilic compounds. In this study, we improved the original method for H-ORAC determination, and evaluated the precision of the two improved methods (methods A and B) by interlaboratory studies using 5 antioxidant solutions and 5 food extracts as test samples. An interlaboratory study of method A, in accordance with the harmonized protocol, demonstrated satisfactory performance (intermediate precision relative standard deviations (RSD(int)) ranging from 4.6 to 18.8%; the reproducibility relative standard deviations (RSD(R)) ranging from 7.0 to 21.1%, and the HorRat values ranging from 0.40 to 1.93). However, methodological problems remained, and a further improved method, method B, was thus developed. An interlaboratory study of method B by 5 participating laboratories showed better intermediate precision and reproducibility (RSD(int) and RSD(R) ranging from 1.8 to 9.4%, and from 4.4 to 13.8%, respectively), and all HorRat values for the test samples were less than 1.3, suggesting good performance for the H-ORAC measurement. 相似文献
47.
Konarev DV Khasanov SS Otsuka A Yamochi H Saito G Lyubovskaya RN 《Inorganic chemistry》2012,51(6):3420-3426
The salt (DMI(+))(2)·(C(60)(?-))·{Cd(Et(2)NCS(2))(2)I(-)} (1) containing fullerene radical anions, the anions of cadmium diethyldithiocarbamate iodide, and N,N'-dimethylimidazolium cations was obtained. Fullerenes are monomeric in 1 at 250 K and form three-dimensional packing in which each fullerene has nearly tetrahedral surroundings from neighboring fullerenes. Fullerenes with a shorter interfullerene center-to-center distance of 10.031(2) ? form spiral chains arranged along the lattice c axis. The convolution consists of four fullerene molecules. Dimerization realized in 1 within the spiral chains below 135 K manifests a strong dependence on the cooling rate. The "frozen" monomeric phase was obtained upon instant quenching of 1. This phase is stable below 95 K for a long time but slowly converted to the dimeric phase at T > 95 K. It exhibits a weak antiferromagnetic interaction of spins below 95 K (the Weiss temperature is -4 K), which results in the splitting of the electron paramagnetic resonance (EPR) signal into two components below 10 K. A disordered phase containing both C(60)(?-) monomers and singly bonded (C(60)(-))(2) dimers with approximately 0.5/0.5 occupancies is formed at an intermediate cooling rate (for 20 min). The position of each fullerene in this phase is split into three positions slightly shifted relative to each other. The central position corresponds to nonbonded fullerenes with interfullerene center-to-center distances of 9.94-10.00 ?. Two other positions are coincided to dimeric fullerenes formed with the right and left fullerene neighbors within the spiral chain. This intermediate phase is paramagnetic with nearly zero Weiss temperature due to isolation of C(60)(?-) by diamagnetic species and exhibits a strongly asymmetric EPR signal below 20 K. A diamagnetic phase containing ordered singly bonded (C(60)(-))(2) dimers can be obtained only upon slow cooling of the crystal for 6 h. 相似文献
48.
49.
50.
Keiko Takahashi Hiroshi Narita Megumi Oh-Hashi Akihiro Yokoyama Tsutomu Yokozawa 《Journal of inclusion phenomena and macrocyclic chemistry》2004,50(1-2):121-127
A complete assignment of proton resonances for N(N-formyl d-phenylalanyl)-deoxyamino--cyclodextrin (1d) was performed by means of 1D and 2D NMR,1H–^1H-COSY, 1H–^13C-COSY, TOCSYand NOESY spectroscopy. Based on 2D-NMR ROESY and circular dichroism spectroscopy, the conformation of 1d was determined; the phenyl group stays inside the distorted cyclodextrin (CyD) cavity forming a self-inclusion complex, which is almost the same as N(N-formyl l-phenylalanyl)-deoxyamino--CyD (1l). The remarkable diastereomeric difference was observed in the chemical shifts of H(5) and H(6) protons at the narrow rim of the CyD cavity and induced circular dichroism spectra. These results suggest the existence of hydrogen bonds between the hydroxyl group on CyD and the amide groups on the arms, which provides the difference in the molecular recognition properties. 相似文献