全文获取类型
收费全文 | 1718篇 |
免费 | 39篇 |
国内免费 | 14篇 |
专业分类
化学 | 1327篇 |
晶体学 | 21篇 |
力学 | 13篇 |
数学 | 53篇 |
物理学 | 357篇 |
出版年
2021年 | 19篇 |
2020年 | 11篇 |
2019年 | 26篇 |
2018年 | 16篇 |
2017年 | 10篇 |
2016年 | 20篇 |
2015年 | 25篇 |
2014年 | 31篇 |
2013年 | 91篇 |
2012年 | 66篇 |
2011年 | 102篇 |
2010年 | 53篇 |
2009年 | 44篇 |
2008年 | 102篇 |
2007年 | 92篇 |
2006年 | 85篇 |
2005年 | 84篇 |
2004年 | 74篇 |
2003年 | 61篇 |
2002年 | 59篇 |
2001年 | 46篇 |
2000年 | 50篇 |
1999年 | 40篇 |
1998年 | 20篇 |
1997年 | 18篇 |
1996年 | 28篇 |
1995年 | 32篇 |
1994年 | 19篇 |
1993年 | 12篇 |
1992年 | 24篇 |
1991年 | 25篇 |
1990年 | 18篇 |
1989年 | 19篇 |
1988年 | 15篇 |
1987年 | 22篇 |
1986年 | 19篇 |
1985年 | 44篇 |
1984年 | 36篇 |
1983年 | 18篇 |
1982年 | 18篇 |
1981年 | 8篇 |
1980年 | 15篇 |
1979年 | 24篇 |
1978年 | 26篇 |
1977年 | 14篇 |
1976年 | 14篇 |
1975年 | 14篇 |
1974年 | 13篇 |
1973年 | 7篇 |
1971年 | 10篇 |
排序方式: 共有1771条查询结果,搜索用时 156 毫秒
111.
112.
113.
Takuya Hashimoto 《Tetrahedron letters》2010,51(4):761-8145
FeCl3/AgOTf-catalyzed hydroarylation of propiolic acid with electron-rich arenes such as mesitylene, tetramethylbenzene, and pentamethylbenzene in trifluoroacetic acid proceeded to give 3-arylpropenoic acids in moderate to high yields. The same reactions with anisole and 1,4-dimethoxybenzene afforded double hydroarylation products, 3,3-diarylpropionic acids. 相似文献
114.
115.
Akiko Hashimoto Takehiro Yamanaka Takeji Takamura-Enya 《Journal of nanoparticle research》2017,19(12):402
Fullerene is a well-known carbon nanomaterial, which can be potentially used for drug manufacture or delivery. Despite several successful examples of utilizing fullerene derivatives as drug candidate materials, their low water solubility under physiological conditions negatively affects the cell penetration efficiency after treatment. In this work, we successfully synthesized two fullerene derivatives with covalently attached fluorescein and boron dipyrromethene (BODIPY) fluorophore moieties, which exhibited cellular uptake and intracellular localization. While both fluorophores decreased their fluorescence intensity in the vicinity of fullerene, the cellar uptake of the fluorescein-modified fullerene was detected via fluorescence microscopy observations. Moreover, decreases in the fluorescence intensities of the intact fluorescein and BODIPY species were observed when both fluorophores and fullerene coexisted in aqueous media. 相似文献
116.
Fujikawa Y Akiyama K Nagao T Sakurai T Lagally MG Hashimoto T Morikawa Y Terakura K 《Physical review letters》2002,88(17):176101
The structure of Ge(105)-(1 x 2) grown on Si(105) is examined by scanning tunneling microscopy (STM) and first-principles calculations. The morphology evolution with an increasing amount of Ge deposited documents the existence of a tensile surface strain in Si(105) and its relaxation with increasing coverage of Ge. A detailed analysis of high-resolution STM images and first-principles calculations produce a new stable model for the Ge(105)-(1 x 2) structure formed on the Si(105) surface that includes the existence of surface strain. It corrects the model developed from early observations of the facets of "hut" clusters grown on Si(001). 相似文献
117.
Kitajima M Hashimoto K Yokoya M Takayama H Aimi N Sakai SI 《Chemical & pharmaceutical bulletin》2000,48(10):1410-1412
A new gluco indole alkaloid, 3,4-dehydro-5-carboxystrictosidine, was obtained from Peruvian U?a de Gato (Cat's Claw, original plant: Uncaria tomentosa) together with two known gluco indole alkaloids. This compound was the first example of isolation of a gluco monoterpenoid indole alkaloid having a 3,4-dihydro-beta-carboline ring system from nature. A characteristic feature of the compound was the quick replacement of the methylene hydrogens on C-14 with deuterium that was observed when it was dissolved in CD3OD. We demonstrated a similar proton-deuterium exchange on a model compound, 1-methyl-3,4-dihydro-gamma-carboline, in CD3OD solution. 相似文献
118.
Hayashi M Hashimoto Y Yamamoto Y Usuki J Saigo K 《Angewandte Chemie (International ed. in English)》2000,39(3):631-633
Convenient access to cyclopentenones is provided by catalytic intra- and intermolecular Pauson - Khand reactions in the presence of octacarbonyldicobalt and tributylphosphane sulfide (see scheme). In contrast to other reactions of this type, they proceed under mild conditions (70 degrees C, 1 atm CO), and commercially available [Co(2)(CO)(8)] can be used without further purification. 相似文献
119.
The effect of a geometrical relationship between a grain boundary (GB) plane and a tensile axis on intergranular fatigue cracking along 3(1 1 2) twin boundaries has been investigated in Fe-30%Cr alloy crystals. Fatigue experiments were carried out on the three kinds of the specimens containing the 3(1 1 2) twin boundary. It was found that the fatigue cracking behavior was sensitive to the geometry of the GB plane. In a specimen where both the GB plane and a slip vector lying in the GB plane in adjacent grains are inclined to the tensile axis at 45°, the fatigue cracks were nucleated preferentially along the twin boundary at a stress amplitude of 170 MPa. The specimen with the GB plane normal to the tensile axis showed that the fatigue crack was initiated from a slip band formed within a constituent grain at a stress amplitude of 300 MPa. When the GB plane was inclined to the tensile axis but the slip vector lying in the GB plane was normal to the tensile axis, development of additional slips formed perpendicular to the GB plane were observed at a specific site of the GB. Initiation of intergranular fatigue cracks at the site was recognized at a stress amplitude of 250 MPa. It can be suggested that the GB plane normal to the tensile axis provides the highest fatigue performance among them. The difference in the cracking property among these specimens could be understood in terms of the effective Schmid factor derived from elastically incompatible stress. 相似文献
120.
Kazuhiko Saigo Yukihiko Hashimoto Kazushi Kinbara Atsushi Sudo 《Journal of Chemical Sciences》1996,108(6):555-573
The review describes the mechanism of chiral discrimination of racemic amines upon crystallization and the induction of chirality
in organic reactions by using them as chiral auxiliaries. In order to form conglomerates, which can be resolved into the two
enantiomers upon alternative seeding, both formation and packing of 21-columns are essentially very important. On the other hand, in order to achieve high efficiency in resolution through diastereomeric
salt formation, which is the most practical method, one of a pair of diastereomeric salts derived from a racemic amine and
an enantiomerically pure resolving agent should at least have two 21-columns and planar boundary surfaces in its crystal structure. On the basis of this knowledge, we developed several artificial
chiral auxiliaries such as erythro-2-amino-1,2-diphenylethanol,cis-2-amino-1-acenaphthenol, andcis-2-amino-3,3-dimethyl-1-indanol. These were found to be very efficient chiral auxiliaries in asymmetric inductions: alkylation
of chiral imines, catalytic borane-reduction, and alkylation of chiral N-acylated oxazolidinone. 相似文献