全文获取类型
收费全文 | 1309篇 |
免费 | 25篇 |
国内免费 | 6篇 |
专业分类
化学 | 953篇 |
晶体学 | 22篇 |
力学 | 16篇 |
数学 | 59篇 |
物理学 | 290篇 |
出版年
2021年 | 10篇 |
2020年 | 14篇 |
2019年 | 12篇 |
2018年 | 9篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 13篇 |
2014年 | 29篇 |
2013年 | 53篇 |
2012年 | 68篇 |
2011年 | 70篇 |
2010年 | 22篇 |
2009年 | 34篇 |
2008年 | 101篇 |
2007年 | 70篇 |
2006年 | 61篇 |
2005年 | 77篇 |
2004年 | 74篇 |
2003年 | 60篇 |
2002年 | 63篇 |
2001年 | 42篇 |
2000年 | 20篇 |
1999年 | 18篇 |
1998年 | 15篇 |
1997年 | 18篇 |
1996年 | 20篇 |
1995年 | 19篇 |
1994年 | 17篇 |
1993年 | 15篇 |
1992年 | 18篇 |
1991年 | 15篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 15篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 18篇 |
1978年 | 15篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1975年 | 16篇 |
1974年 | 10篇 |
1973年 | 15篇 |
1971年 | 5篇 |
排序方式: 共有1340条查询结果,搜索用时 15 毫秒
11.
K. Matsuishi T. Anzaki S. Onari T. Arai 《International Journal of Infrared and Millimeter Waves》1989,10(7):745-750
Far infrared absorption spectra of amorphous (As2S3)1–x(Sb2S3)x system (x=0.00.6) were measured in the wavenumber region 725 cm–1 with Lamellar grating far infrared Fourier Transform Spectrometer, and the spatial fluctuation of charges and its correlation range were estimated with charge fluctuation model. The charge fluctuation of (As2S3)1–x(Sb2S3)x system increases with Sb2S3 concentration x. On the other hand, the correlation length of the charge fluctuation decreases from 7 A to 4.5 A with an increase in x. As a result, it can be found that the medium range order of As2S3 changes drastically with an incease in Sb2S3 concentration x. 相似文献
12.
A fluorimetric determination method for N-arachidonoylethanolamine (anandamide) was developed using a precolumn fluorescence derivatization followed by coupled-column high-performance liquid chromatography (HPLC). Anandamide extracted from the rat brain tissue was derivatized with 4-N-chloroformylmethyl-N-methylamino-7-N, N-dimethylaminosulfonyl-2,1,3-benzoxadiazole (DBD-COCl), purified by a solid-phase extraction (Emporetrade mark), and assayed by the coupled-column HPLC. The HPLC consisted of phenyl (100 x 4.6 mm i.d. ) and octadecylsilica columns (250 x 4.6 mm i.d.), both connected by a six-port valve. The concentration of anandamide in rat brain was 3. 37 +/- 0.73 pmol/g with 6.47 and 3.57% of intra- and inter-day precisions, respectively. Using this method, we investigated the alteration of anandamide concentration in rat brain 30 min after administration of anandamide (2 mg/kg, i.p.) to rats pretreated with or without phenylmethylsulfonyl fluoride (PMSF; 30 mg/kg, i.p.), an inhibitor of amidohydrolase. In rats pretreated with PMSF, the brain concentration of anandamide was approx. 16-fold higher than that of rats without PMSF (p < 0.01). 相似文献
13.
Kuniaki Tatsuta Yoshiya Amemiya Yoshinobu Kanemura Hideaki Takahashi Mitsuhiro Kinoshita 《Tetrahedron letters》1982,23(33):3375-3378
Tylosin has been synthesized byregio- and stereoselective introduction of the amino disaccharide moiety and D-mycinose onto the previously synthesized 16-membered-ring aglycone. 相似文献
14.
15.
Chau Jin Hu Ryuichi Oshima Yuji Arai Manabu Sen
《Journal of polymer science. Part A, Polymer chemistry》1988,26(9):2423-2433
Copolymers containing an intramolecular electron donor-acceptor (EDA) complex were synthesized by free radical copolymerization of 2-N-carbazolylethyl acrylate and 2-(3,5-dinitrobenzoyloxy)ethyl methacrylate. Glass transition temperatures show a positive deviation from the weight-average values of copolymers, indicating the presence of the specific EDA interaction in copolymers in the solid state. Photoinduced “memory effect,” which is defined as the percentage of the difference of the surface potential given by corona charging before and after irradiation of light on polymer films, was 30% for the copolymer with 5 mol% of acceptor content. Memory effect increased to 70% for a 8 μm film by doping with 2 wt% of trichloroacetic acid (TCAA), and leveled off at 5 wt% of TCAA content. Memory effect was also enhanced by increasing the thickness of polymer films and irradiation time. The largest value of memory effect (85%) was obtained from the film of the copolymer with 5 mol% acceptor content doped with 1 wt% TCAA and with thickness larger than 14 μm. 相似文献
16.
17.
Nishimiya N Yamaguchi Y Ohrui Y Suzuki M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(3):493-504
The mirror gap of a Fabry-Perot interferometer was stabilized with two laser diodes; one locked to the line frequency 385,243,555.14445 MHz of the F=3<--1 in 5D(3/2)<--5S(1/2) (87Rb) and the other to the 385,284,566.3663 MHz of the F=4<--2 in 5D(5/2)<--5S(1/2) (87Rb) [Opt. Commun. 102 (1993) 432]. The length of the mirror gap was adjusted to generate the zero-cross points simultaneously at both of the two line positions. The fringe signals obtained from an interferometer thus stabilized can be used as frequency markers having accuracies of the order of 10(10) depending on the finesse of the interferometer used. Based on measurement using Cs D1 hyperfine lines reported by Udem et al. [Phys. Rev. Lett. 82 (1999) 3568], the uncertainty of markers in the region 50 THz apart from the reference lines is +/- 5 MHz. 相似文献
18.
Kozo Arai Atsushi Matsunaga Masaru Yoneyama Shoji Takigami Yoshio Nakamura Haydn E. Edwards Glyn O. Phillips 《Journal of polymer science. Part A, Polymer chemistry》1993,31(1):249-258
The reactions of heparin with 2,4,6-trinitrobenzenesulfonic acid (TNBS) were studied spectrometrically. Seven different commercial heparins were used in this study. The amino groups react with TNBS to form equimolar amounts of trinitrophenylated (TNP) amino groups and bisulfite ions. The TNP-amino groups further react with bisulfite ions to form the monosubstituted anionic sigma complex. The absorption spectrum with two maxima at approximately 350 nm and approximately 420 nm, characteristic of either the TNP-amino groups or the complex, was analyzed for the reaction of TNBS with heparin. It was shown that the reactivities of TNBS with amino groups from α-amino acid and hexosamine residues are greatly different. By combining the results of the reaction kinetics and the reaction of heparin with Sanger's reagent, the number of the α-amino groups and the free amino groups in hexosamine residues were determined. These data have been performed with a range of heparins from different commercial sources, of different activities and physical characteristics. No correlation was found between the free amino contents of these heparins and biological potency. © 1993 John Wiley & Sons, Inc. 相似文献
19.
The third generation of novel photo-responsive water-soluble stilbene dendrimer (trans- and cis-G3 WSD) undergoes unusual one-way trans-to-cis isomerization to give 100% of cis isomer at the photostationary state on UV irradiation in water. 相似文献
20.
Watanabe M Sue K Adschiri T Inomata H Smith RL Arai K 《Chemical communications (Cambridge, England)》2001,(21):2270-2271
In supercritical water the rate of methanol oxidation was controlled by ionic behavior as follows: the oxidation rate of methanol decreased with increasing proton and hydroxide ion concentration, possibly due to stabilization of the reactant, while that of CO was suppressed by added protons and enhanced by added hydroxide ions. 相似文献