全文获取类型
收费全文 | 1553篇 |
免费 | 51篇 |
国内免费 | 15篇 |
专业分类
化学 | 1203篇 |
晶体学 | 9篇 |
力学 | 13篇 |
数学 | 117篇 |
物理学 | 277篇 |
出版年
2023年 | 8篇 |
2022年 | 11篇 |
2021年 | 16篇 |
2020年 | 6篇 |
2019年 | 32篇 |
2018年 | 23篇 |
2017年 | 10篇 |
2016年 | 25篇 |
2015年 | 40篇 |
2014年 | 35篇 |
2013年 | 103篇 |
2012年 | 97篇 |
2011年 | 100篇 |
2010年 | 66篇 |
2009年 | 65篇 |
2008年 | 100篇 |
2007年 | 114篇 |
2006年 | 119篇 |
2005年 | 97篇 |
2004年 | 89篇 |
2003年 | 60篇 |
2002年 | 68篇 |
2001年 | 21篇 |
2000年 | 24篇 |
1999年 | 18篇 |
1998年 | 10篇 |
1997年 | 11篇 |
1996年 | 21篇 |
1995年 | 11篇 |
1994年 | 9篇 |
1993年 | 13篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 15篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 20篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 13篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1975年 | 5篇 |
1973年 | 11篇 |
排序方式: 共有1619条查询结果,搜索用时 15 毫秒
31.
Pd(II)-SPRIX catalyst coupled with an environmentally benign molecular oxygen as the sole oxidant successfully exploited the construction of pyrrolizines/pyrroloindoles, imperative scaffolds of bio-potent molecules through intramolecular C-N and C-C bond forming reactions in good yields with appreciable enantioselectivities. 相似文献
32.
A Permselective CeOx Coating To Improve the Stability of Oxygen Evolution Electrocatalysts 下载免费PDF全文
Keisuke Obata Prof. Kazuhiro Takanabe 《Angewandte Chemie (International ed. in English)》2018,57(6):1616-1620
Highly active NiFeOx electrocatalysts for the oxygen evolution reaction (OER) suffer gradual deactivation with time owing to the loss of Fe species from the active sites into solution during catalysis. The anodic deposition of a CeOx layer prevents the loss of such Fe species from the OER catalysts, achieving a highly stable performance. The CeOx layer does not affect the OER activity of the catalyst underneath but exhibits unique permselectivity, allowing the permeation of OH? and O2 through while preventing the diffusion of redox ions through the layer to function as a selective O2‐evolving electrode. The use of such a permselective protective layer provides a new strategy for improving the durability of electrocatalysts. 相似文献
33.
34.
35.
Masaaki Kitano Kazuhiro Iyatani Ebrahimi Afsin Yu Horiuchi Masato Takeuchi So-Hye Cho Masaya Matsuoka Masakazu Anpo 《Research on Chemical Intermediates》2012,38(6):1249-1259
Visible light-responsive TiO2 (Vis-TiO2) thin films able to absorb UV and visible light in wavelength regions of 250–600 nm were successfully developed by applying
a radio-frequency magnetron sputtering deposition method. These Vis-TiO2 thin films exhibited high activity for the photocatalytic oxidation of 2-propanol diluted in water even under visible light
irradiation (λ ≥ 450 nm). The photocatalytic activity of Vis-TiO2 thin films was dramatically enhanced by the deposition of Pt particles on the surface. Secondary ion mass spectrometry measurements
revealed that Pt particles are distributed from the top surface to the deep bulk of Vis-TiO2 thin films with a columnar structure. The unique columnar structure of Vis-TiO2 thin films plays an important role in the high photocatalytic performance. 相似文献
36.
Takahashi K Hasegawa Y Sakamoto R Nishikawa M Kume S Nishibori E Nishihara H 《Inorganic chemistry》2012,51(9):5188-5198
We previously reported that an Fe(II) complex ligated by two (Z)-2,6-di(1H-pyrazol-1-yl)-4-styrylpyridine ligands (Z-H) presented a solid state ligand-driven light-induced spin change (LD-LISC) upon one-way Z-to-E photoisomerization, although modulation of the magnetism was trivial at ambient temperatures (Chem. Commun.2011, 47, 6846). Here, we report the synthesis of new derivatives of Z-H, Z-CN and Z-NO(2), in which electron-withdrawing cyano and nitro substituents are introduced at the 4-position of the styryl group to attain a more profound photomagnetism at ambient temperatures. Z-CN and Z-NO(2) undergo quantitative one-way Z-to-E photochromism upon excitation of the charge transfer band both in acetonitrile and in the solid state, similar to the behavior observed for Z-H. In solution, these substituents stabilized the low-spin (LS) states of Z-CN and Z-NO(2), and the behavior was quantitatively analyzed according to the Evans equation. The photomagnetic properties in the solid state, on the other hand, cannot be explained in terms of the substituent effect alone. Z-CN displayed photomagnetic properties almost identical to those of Z-H. Z-CN preferred the high-spin (HS) state at all temperatures tested, whereas photoirradiated Z-CN yielded a lower χ(M)T at ambient temperatures. The behavior of Z-NO(2) was counterintuitive, and the material displayed surprising photomagnetic properties in the solid state. Z-NO(2) occupied the LS state at low temperatures and underwent thermal spin crossover (SCO) with a T(1/2) of about 270 K. The photoirradiated Z-NO(2) displayed a higher value of χ(M)T and the modulation of χ(M)T exceeded that of Z-H or Z-CN. Z-NO(2)·acetone, in which acetone molecules were incorporated into the crystal lattice, further stabilized the LS state (T(1/2) > 300 K), thereby promoting large modulations of the χ(M)T values (87% at 273 K and 64% at 300 K) upon Z-to-E photoisomerization. Single crystal X-ray structure analysis revealed that structural factors played a vital role in the photomagnetic properties in the solid state. Z-H and Z-CN favored intermolecular π-π stacking among the ligand molecules. The coordination sphere around the Fe(II) nucleus was distorted, which stabilized the HS state. In contrast, Z-NO(2)·acetone was liberated from such intermolecular π-π stacking and coordination distortion, resulting in the stabilization of the LS state. 相似文献
37.
We found that Br-/Br3- is more suitable than an I-/I3- couple in dye-sensitized solar cells in terms of higher open-circuit photovoltage (Voc) production and higher overall energy conversion efficiency (eta) if the dye sensitizer has a more positive potential than that of Br-/Br3-. Under simulated AM1.5 one sun, an eosin Y dye-sensitized solar cell containing 0.4 M LiBr + 0.04 M Br2 electrolyte in acetonitrile yielded a short-circuit photocurrent (Jsc) of 4.63 mA cm(-2), Voc of 0.813 V, and fill factor (FF) of 0.693, corresponding to 2.61% of eta. Under the same conditions except for the electrolyte 0.4 M LiI + 0.04 M I2 in acetonitrile instead, the device produced 1.67% of eta (Jsc = 5.15 mA cm(-2), Voc = 0.451 V, FF = 0.721). Replacement of I-/I3- with Br-/Br3- in eosin Y dye-sensitized solar cells yielded a significant increase in Voc offset by slight decreases in Jsc and FF, leading to an increase in eta by 56%. The significant gain in Voc was attributed to the enlarged energy level difference between the redox potential of the electrolyte and the Fermi level of TiO2 and the suppressed charge recombination as well. The rate for charge recombination between bromine and the injected electrons was determined to be first order in bromine. 相似文献
38.
Kazuhiro Marumo Manabu Itoh Sungmin Kang Koichi Sakajiri Junji Watanabe 《Liquid crystals》2013,40(2):234-238
Galactose derivatives were explored as chiral dopants, effective for inducing chiral nematic liquid crystal (LC) phases. Galactose bearing O-isopropylidene substituents at the C3 and C4 and butoxybiphenyl substituents at the C2 and C6 positions exhibits a high helical twisting power (HTP) value of ?74.4 μm?1. Such a high HTP value for the galactose derivative is attributed to (1) linkage of the C3 and C4 carbons with the O-isopropylidene substituent, which places the C2 and C6 substitutes in a skew arrangement at a large angle and (2) enhancement of the affinity with the host nematic LCs by incorporating aromatic substituents at the C2 and C6 positions that are similar to those in the host. 相似文献
39.
Selective Exo‐Enzymatic Labeling of N‐Glycans on the Surface of Living Cells by Recombinant ST6Gal I
40.
The reaction of 1-bromo-2-(1-isothiocyanatoalkyl)benzenes, which are easily derived from 2-bromophenyl ketones or (2-bromophenyl)methanamine, with butyllithium generates 1-(1-isothiocyanatoalkyl)-2-lithiobenzenes, which immediately underwent intramolecular cyclization to give rise to the corresponding 3-substituted and 3,3-disubstituted 2,3-dihydro-1H-isoindole-1-thiones in good yields. 相似文献