全文获取类型
收费全文 | 625篇 |
免费 | 13篇 |
国内免费 | 2篇 |
专业分类
化学 | 460篇 |
晶体学 | 7篇 |
力学 | 8篇 |
数学 | 34篇 |
物理学 | 131篇 |
出版年
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 12篇 |
2018年 | 9篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 10篇 |
2013年 | 39篇 |
2012年 | 21篇 |
2011年 | 32篇 |
2010年 | 24篇 |
2009年 | 24篇 |
2008年 | 34篇 |
2007年 | 31篇 |
2006年 | 31篇 |
2005年 | 33篇 |
2004年 | 22篇 |
2003年 | 24篇 |
2002年 | 34篇 |
2001年 | 17篇 |
2000年 | 10篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 10篇 |
1994年 | 11篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1974年 | 7篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1969年 | 4篇 |
1967年 | 2篇 |
1966年 | 3篇 |
排序方式: 共有640条查询结果,搜索用时 31 毫秒
81.
Terai T Maki E Sugiyama S Takahashi Y Matsumura H Mori Y Nagano T 《Chemistry & biology》2011,18(10):1261-1272
Biotin-(strept)avidin complex is widely used in biotechnology because of its extremely high binding constant, but there is no report describing spatiotemporally controlled formation of the complex in live cells. Here, based on X-ray crystal structure analysis and calorimetric data, we designed and synthesized photoreleasable biotins, which show greatly reduced affinity for (strept)avidin, but recover native affinity after UV irradiation. For application at the cell surface, we introduced an amine-reactive moiety into these "caged" biotin molecules. Specific fluorescence imaging of live cells that had been labeled with these agents and then UV-irradiated, was accomplished by addition of streptavidin conjugated with a fluorophore. We also demonstrated the applicability of these compounds for UV-irradiated-cell-specific drug delivery by using caged-biotin-labeled cells, a prodrug, and streptavidin conjugated with a prodrug-activating enzyme. 相似文献
82.
An efficient route toward the central ABC system of jiadifenin has been developed using two key Pd-catalyzed cyclizations. A protic solvent-activated Mizoroki-Heck reaction was used to construct the C(9) quaternary carbon and the A ring. A cascading Tsuji-Trost cyclization/lactonization sequence was employed to establish the BC ring system and the C(5,6) stereochemistry. 相似文献
83.
The HIJKLM ring system of ciguatoxin CTX3C was synthesized in a convergent manner. The key steps were a conjugate addition/alkylation sequence, spiroacetalization, intramolecular allylation, ring-closing metathesis, and hydrogenation to form the 36-α-methyl substituent. 相似文献
84.
Kitamura C Takenaka A Kawase T Kobayashi T Naito H 《Chemical communications (Cambridge, England)》2011,47(23):6653-6655
Tetracene octaesters, which were prepared by twofold [2+2+2] cocyclization, were isolated as red, orange, and orange-yellow solids for the methyl, ethyl, and propyl ester derivatives, respectively. X-Ray crystallographic analysis reveals that the difference in solid-state color arises owing to differences in molecular packing. 相似文献
85.
In this article, the structural characterization of chemical vapor deposition (CVD) nickel metal foam is presented. Scanning
electron microscope and post image processing were used to carefully analyze the surface of the nickel metal foams. Data on
foam unit cell, ligament thickness, projected pore diameter, and averaged porosity was obtained. Unit cell and projected pore
diameters of CVD nickel metal foam possess Gaussian-like distribution. Characteristics of pore structure and its effect on
permeability in Darcian flow regime were analyzed. The relations between the permeability, pore size, and porosity are presented.
Present and previous data are compared with these relations. Measurement results indicate that the permeability or the viscous
conductivity of the CVD processed metal foam is affected not only by the pore size, and porosity but also by the ligament
structure. 相似文献
86.
Summary Indirect conductimetric detection of nonelectrolytes was investigated in microcolumn liquid chromatography. The mobile phase contained an electrolytic substance which maintained a high background and analytes were indirectly detected owing to a depression of the background signal. The dynamic reserve, defined as the ratio of the background to its noise level, was 9.3×104, and the detection limits at S/N=3 were 10–32 ng for alcohols examined. 相似文献
87.
Acetyl 29-methyl-29-methylidene-D:C-friedoolean-8-en-3beta-o1 (2), derived from bryonolic acid (D:C-friedoolean-8-en-3beta-ol-29-oic acid) (1), was crystallographically analyzed. Rings A-E of 2 adopted chair, half-chair, half-chair, boat (with bow and stern at C-13 and C-16), boat (with bow and stem at C-19 and C-22) conformations, respectively. Good agreement was found between the structures from X-ray crystallography and that from MM2 calculations. 相似文献
88.
The mechanism of GMR effects in La(Mn1–x
Fe
x
)O3 (x=0, 0.01, 0.03) oxides has been investigated by means of magnetic measurements, resistivity measurements in magnetic field and Mössbauer spectroscopy. For the x=0.01 sample, the GMR behavior is similar to that of the conventional (La, A)MnO3 (A: divalent cations) oxides. For the x=0.03 sample, even though the temperature dependence of the Mössbauer spectra was similar to that of the x=0.01 sample, the mechanism for the occurrence of the GMR effect seems to be different. The x=0 sample shows a similar behavior to the x=0.03 sample. A thermal stabilization of spin fluctuation is proposed for the x=0 and x=0.03 sample. 相似文献
89.
Hideaki Hioki Mizuki Fukutaka Miwa Kubo Mitsuaki Kodama Keiko Ideta 《Tetrahedron》2005,61(45):10643-10651
A new traceless linker was developed to synthesize a library of 42 compounds possessing an azomethine linkage using combinatorial solid-phase parallel synthesis. The loading of the substrates on a solid support and cleavage from the solid support were performed by an imine synthesis and by imine-exchanged process under mild conditions, respectively. Thioesters with a hydroxy group on the central core exhibited liquid crystalline properties with the widest transition temperatures in the library. 相似文献
90.
Ei-ichi Nishizawa Leenawaty Limantara Noriyuki Nanjou Hiroyoshi Nagae Tomisaburo Kakuno Yasushi Koyama 《Photochemistry and photobiology》1994,59(2):229-236
The frequency of BChl that was bound to the light-harvesting complex (LHC) of Rhodobacter sphaeroides R26 was found to be 1598 cm-1 , a result which suggests that a pair of BChl molecules form a dimer in the LHC in the T1 state. 相似文献