全文获取类型
收费全文 | 6358篇 |
免费 | 419篇 |
专业分类
6777篇 |
出版年
2021年 | 50篇 |
2019年 | 61篇 |
2018年 | 63篇 |
2017年 | 65篇 |
2016年 | 97篇 |
2015年 | 119篇 |
2014年 | 147篇 |
2013年 | 365篇 |
2012年 | 303篇 |
2011年 | 230篇 |
2010年 | 161篇 |
2009年 | 152篇 |
2008年 | 274篇 |
2007年 | 283篇 |
2006年 | 288篇 |
2005年 | 254篇 |
2004年 | 296篇 |
2003年 | 305篇 |
2002年 | 294篇 |
2001年 | 241篇 |
2000年 | 222篇 |
1999年 | 184篇 |
1998年 | 82篇 |
1997年 | 69篇 |
1996年 | 64篇 |
1995年 | 44篇 |
1994年 | 64篇 |
1993年 | 65篇 |
1992年 | 149篇 |
1991年 | 122篇 |
1990年 | 142篇 |
1989年 | 148篇 |
1988年 | 119篇 |
1987年 | 110篇 |
1986年 | 105篇 |
1985年 | 87篇 |
1984年 | 80篇 |
1983年 | 64篇 |
1982年 | 54篇 |
1981年 | 51篇 |
1980年 | 42篇 |
1979年 | 79篇 |
1978年 | 58篇 |
1977年 | 54篇 |
1976年 | 42篇 |
1975年 | 41篇 |
1974年 | 44篇 |
1973年 | 41篇 |
1972年 | 47篇 |
1970年 | 36篇 |
排序方式: 共有6777条查询结果,搜索用时 15 毫秒
71.
72.
73.
Molecular chain conformations of poly-γ-methyl-L -glutamate, poly-γ-methyl-D -glutamate, and poly-γ-methyl-D ,L -glutamate in membranes prepared by using mainly trifluoroacetic acid and formic acid as solvents were investigated by infrared, X-ray diffraction, and optical rotatory dispersion measurements. It was pointed that these polymers exist in the α-helix form in membranes cast from trifluoroacetic acid solutions, but in the β-chain form in membrances swollen in formic acid. The β-chain structure was also observed in crystals precipitated from dilute solutions including formic acid. The formation of the β-chain structure was discussed. 相似文献
74.
Simple approximate expressions have been derived from the theory of Zimm and Bragg for use in the analysis of experimental data on the helix-coil transition in polypeptide. On the basis of the resulting expressions practical procedures are proposed to determine two basic parameters characterizing a thermally induced transition, i.e., helix initiation parameter σ and enthalpy change for helix formation, ΔH. They have been applied to the data for poly(β-benzyl L -aspartate) (PBLA) with the result: σ = 1.6 × 10?4 and ΔH = ?450 cal/mole for PBLA in m-cresol; σ = 0.6 × 10?4 and ΔH = 260 cal/mole for PBLA in chloroform containing 5.7 vol-% of dichloroacetic acid. This result gives evidence that σ may change not only from one polypeptide to another but also for a given polypeptide in different solvents. The change in limiting viscosity number [η] accompanying the transition was measured in the same solvents. The curve of [η] versus helical content had a relatively monotonic shape for the chloroformdichloroacetic acid solutions as compared with that for the m-cresol solutions, indicating that [η] depended largely on σ. Provided that [η] is a direct measure of the mean-square radius of gyration, 〈S2〉, the results are consistent with the theoretical predictions of Nagai and of Miller and Flory for 〈S2〉. 相似文献
75.
Y Namba K Yoshizawa A Ejima T Hayashi T Kaneda 《The Journal of biological chemistry》1969,244(16):4437-4447
76.
77.
78.
79.
Teru Hayashi 《The Journal of general physiology》1967,50(6):119-133
The molecular basis for the mechanism of contraction in striated muscle, with primary emphasis on the interaction between the thick and thin filaments and the role of the thin (actin) filaments, is the theme presented. Recent information relating to actin-myosin interaction points up the fact that definitive statements cannot be made regarding the molecular interaction(s) that lead to contraction. Nevertheless, the properties of actin indicate that (a) actin in the monomeric state has properties differing markedly from actin in the polymer (filament) state; (b) these property differences may be significant in the contractile process, for they include changes in the reactivity of the bound nucleotide and actin-myosin complex formation; (c) the bound nucleotide seems to be required in the contraction process. For these, and other, reasons discussed, the tentative hypothesis is advanced that the contraction reaction involves local changes in the actin filament providing local monomer or monomer-like actin units in the reaction with myosin. 相似文献
80.
K Hayashi T Kodaira K Baba K Kikuchi 《Nihon saikingaku zasshi. Japanese journal of bacteriology》1966,21(10):633-639