全文获取类型
收费全文 | 194767篇 |
免费 | 1913篇 |
国内免费 | 614篇 |
专业分类
化学 | 107680篇 |
晶体学 | 3292篇 |
力学 | 7814篇 |
综合类 | 4篇 |
数学 | 18341篇 |
物理学 | 60163篇 |
出版年
2016年 | 2266篇 |
2015年 | 1679篇 |
2014年 | 2392篇 |
2013年 | 7820篇 |
2012年 | 5243篇 |
2011年 | 6606篇 |
2010年 | 4418篇 |
2009年 | 4354篇 |
2008年 | 5982篇 |
2007年 | 6149篇 |
2006年 | 5902篇 |
2005年 | 5400篇 |
2004年 | 4943篇 |
2003年 | 4419篇 |
2002年 | 4297篇 |
2001年 | 5772篇 |
2000年 | 4385篇 |
1999年 | 3511篇 |
1998年 | 2741篇 |
1997年 | 2777篇 |
1996年 | 2724篇 |
1995年 | 2515篇 |
1994年 | 2390篇 |
1993年 | 2284篇 |
1992年 | 2779篇 |
1991年 | 2662篇 |
1990年 | 2610篇 |
1989年 | 2637篇 |
1988年 | 2577篇 |
1987年 | 2584篇 |
1986年 | 2400篇 |
1985年 | 3265篇 |
1984年 | 3281篇 |
1983年 | 2712篇 |
1982年 | 2907篇 |
1981年 | 2843篇 |
1980年 | 2752篇 |
1979年 | 2893篇 |
1978年 | 3137篇 |
1977年 | 2958篇 |
1976年 | 2893篇 |
1975年 | 2753篇 |
1974年 | 2700篇 |
1973年 | 2715篇 |
1972年 | 1759篇 |
1971年 | 1466篇 |
1968年 | 1929篇 |
1967年 | 2129篇 |
1966年 | 1920篇 |
1965年 | 1497篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
H Toyoda T Ikei Y Demachi T Toida T Imanari 《Chemical & pharmaceutical bulletin》1992,40(10):2882-2884
The N-linked oligosaccharides from human urinary trypsin inhibitor were purified and their structures were investigated by compositional analysis, the two-dimensional sugar map method and 500 MHz 1H-NMR. The results revealed that they were composed of disialosyl, monosialosyl and asialosyl oligosaccharides, which have the common biantennary core structure; Gal1-4GlcNAc1-2Man1-3(Gal1-4GlcNAc1-2Man1-6)M an1-4GlcNAc1-4GlcNAc. 相似文献
992.
The polymerization of organic compounds in glow discharge (plasma polymerization) was investigated by using pulsed R.F. discharge (100 μsec on, 900 μsec off). The effects of pulsed discharge on polymer deposition rate, pressure change in plasma, ESR signals of free spins in both plasma polymer and substrate, and the contact angle of water on the plasma polymer surface were investigated for various organic compounds. The results are correlated to the mechanisms of polymer formation in plasma (plasma polymerization) which has been postulated as repeating processes of stepwise (propagation) reactions. The effect of the pulse is different from one group of organic compounds to another depending on whether or not they contain an olefinic double bond and/or a triple bond. The main difference seems to be the addition polymerization which can occur exclusively during the off-period of pulsed discharge. Ultraviolet emission from pulsed discharge is much less than from continuous discharge. Consequently, the fragmentation of the monomer and the free-radical formation in the substrate are less with the pulsed discharge. Properties of polymers from some organic compounds formed in continuous and in pulsed discharge were found to be significantly different, and the differences were postulated from the changes of polymerization mechanisms in the pulsed discharge. 相似文献
993.
We show that the two-photon resonances in the third-order susceptibility can be exploited to yield two-photon spectra of molecular gases at moderately high spectral resolution. This form of spectroscopy does not depend on the occurrence of processes (such as fluorescence of photoionization) leading to indirect methods of two-photon absorption. The method is direct and leads in principle to values for a two-photon cross section. Comparisons of two-photon and coherent anti-Stokes Raman resonances leads to ratios of Raman and two-proton cross sections independent of the laser powers and spatial characteristics. The technique is documented with rotationally resolved spectra of SO2 and NO. A value for |αxxαyy| of 1.5 × 10?52 cm6 was measured for the O12 (6) component of the (A)2Σ ← (X)2 Π transition of nitric oxide. 相似文献
994.
H. Freytag 《Fresenius' Journal of Analytical Chemistry》1956,150(4):272-273
Ohne Zusammenfassung 相似文献
995.
Beavan M. Zawadzki B. Dronicik R. Lawford H. Fein J. 《Applied biochemistry and biotechnology》1989,20(1):319-326
Applied Biochemistry and Biotechnology - Z.mobilis (ATCC 29191) produced ethanol in significantly greater yield thanS. cerevisiae, (0.49 vs 0.45 g ethanol/g glucose entering the system), in... 相似文献
996.
997.
Triphenylphosphane Nickel(0) Complexes with Isocyanide Ligands — [(RNC)nNi(PPh3)4–n] (n = 1–3) Synthesis and properties of the isocyanide triphenylphosphane nickel(0) complexes [(RNC)Ni(PPh3)3], [(RNC)2Ni(PPh3)2] and [(RNC)3Ni(PPh3)] (R = tBu, Cy, PhCH2, p-TosCH2) are described. I.r. and 31P n.m.r. spectra were recorded and the X-ray crystal structure of [(PhCH2NC)2Ni(PPh3)2] was determined. 相似文献
998.
W. Dölling K. Kischkies F. Heinemann H. Hartung 《Monatshefte für Chemie / Chemical Monthly》1993,124(6-7):707-719
Summary The new alkyl 2-(2-oxo-benzazoline-3-yl)-3-hydroxy dithiocrotonates and dithiocinnamates4 and the corresponding ketene dithioacetals2 and5 are obtained by dithiocarboxylation of the 3-acceptormethyl substituted benzazoline-2-ones1 or3. Alkylation at room temperature gives compounds4 whereas at higher alkylation temperature2 or5 are formed. The results of X-ray analyses performed for methyl 3-hydroxy-p-chloro-dithiocinnamate4d and of N-[1-(4-chloro-benzoyl)-2,2-bis(methylthio)-vinyl]-benzothiazoline-2-one5e are discussed. 相似文献
999.
1000.
Chen T Barton SC Binyamin G Gao Z Zhang Y Kim HH Heller A 《Journal of the American Chemical Society》2001,123(35):8630-8631