全文获取类型
收费全文 | 205篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 120篇 |
力学 | 3篇 |
数学 | 25篇 |
物理学 | 60篇 |
出版年
2020年 | 2篇 |
2013年 | 37篇 |
2012年 | 2篇 |
2011年 | 7篇 |
2010年 | 2篇 |
2008年 | 6篇 |
2007年 | 11篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 3篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1996年 | 10篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 11篇 |
1991年 | 2篇 |
1989年 | 5篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1977年 | 3篇 |
1973年 | 1篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1968年 | 2篇 |
1961年 | 5篇 |
1960年 | 1篇 |
1958年 | 2篇 |
1957年 | 3篇 |
1956年 | 2篇 |
1954年 | 3篇 |
1951年 | 1篇 |
1948年 | 2篇 |
1947年 | 2篇 |
1942年 | 1篇 |
1941年 | 1篇 |
1939年 | 3篇 |
1937年 | 2篇 |
1935年 | 3篇 |
1934年 | 2篇 |
1928年 | 1篇 |
排序方式: 共有208条查询结果,搜索用时 0 毫秒
81.
82.
83.
S. A. Liebman D. H. Ahlstrom W. H. Starnes JR. F. C. Schilling 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):935-950
This study compares the use of pyrolysis hydrogenation gas chromatography (PHGC) and 13C Fourier transform nuclear magnetic resonance (FTNMR) methods for the analysis of reference polyethylene (PE) samples, ethylene-α-olefin copolymers, and specially prepared poly(vinyl chloride) (PVC) samples which were reduced to their PE skeletal structures. The nature and relative quantities of the short branches along the polymer chains were determined using both techniques. Improved high-resolution PHGC data, obtained with a fused silica capillary separation column, gave results which were in satisfactory agreement with the 13C FTNMR data. This approach confirms that detailed microstructural information can be obtained with these methods by using carefully controlled experimental conditions and appropriate reference systems. 相似文献
84.
A. Thiel G. Schulz G. Coch H. Baggesgaard-Rasmussen und F. Reimers 《Fresenius' Journal of Analytical Chemistry》1935,100(5-6):198-199
Ohne Zusammenfassung 相似文献
85.
86.
87.
Hughes JM Hutter MC Reimers JR Hush NS 《Journal of the American Chemical Society》2001,123(35):8550-8563
Site-directed mutagenesis has been employed by a number of groups to produce mutants of bacterial photosynthetic reaction centers, with the aim of tuning their operation by modifying hydrogen-bond patterns in the close vicinity of the "special pair" of bacteriochlorophylls P identical with P(L)P(M). Direct X-ray structural measurements of the consequences of mutation are rare. Attention has mostly focused on effects on properties such as carbonyl stretching frequencies and midpoint potentials to infer indirectly the induced structural modifications. In this work, the structures of 22 mutants of Rhodobacter sphaeroides have been calculated using a mixed quantum-mechanical molecular-mechanical method by modifying the known structure of the wild type. We determine (i) the orientation of the 2a-acetyl groups in the wild type, FY(M197), and FH(M197) series mutants of the neutral and oxidized reaction center, (ii) the structure of the FY(M197) mutant and possible water penetration near the special pair, (iii) that significant protein chain distortions are required to assemble some M160 series mutants (LS(M160), LN(M160), LQ(M160), and LH(M160) are considered), (iv) that there is competition for hydrogen-bonding between the 9-keto and 10a-ester groups for the introduced histidine in LH(L131) mutants, (v) that the observed midpoint potential of P for HL(M202) heterodimer mutants, including one involving also LH(M160), can be correlated with the change of electrostatic potential experienced at P(L), (vi) that hydrogen-bond cleavage may sometimes be induced by oxidation of the special pair, (vii) that the OH group of tyrosine M210 points away from P(M), and (viii) that competitive hydrogen-bonding effects determine the change in properties of NL(L166) and NH(L166) mutants. A new technique is introduced for the determination of ionization energies at the Koopmans level from QM/MM calculations, and protein-induced Stark effects on vibrational frequencies are considered. 相似文献
88.
Alves GA Amato S Anjos JC Appel JA Astorga J Bernard T Bracker SB Cremaldi LM Darling CL Dixon RL Errede D Gay C Green DR Jedicke R Karchin PE Kwan S Lueking LJ de Mello Neto JR Metheny J Milburn RH de Miranda JM da Motta Filho H Napier A Passmore D Rafatian A dos Reis AC Ross WR Santoro AF Sheaff M Souza MH Spalding WJ Stoughton C Streetman ME Summers DJ Takach SF Wallace A Wu Z 《Physical review letters》1994,72(6):812-815
89.
90.