全文获取类型
收费全文 | 759366篇 |
免费 | 86812篇 |
国内免费 | 371篇 |
出版年
2016年 | 8387篇 |
2015年 | 11548篇 |
2014年 | 13512篇 |
2013年 | 20009篇 |
2012年 | 21849篇 |
2011年 | 22485篇 |
2010年 | 15273篇 |
2009年 | 14082篇 |
2008年 | 19973篇 |
2007年 | 20879篇 |
2006年 | 19554篇 |
2005年 | 18798篇 |
2004年 | 18538篇 |
2003年 | 18192篇 |
2002年 | 17727篇 |
2001年 | 32586篇 |
2000年 | 32824篇 |
1999年 | 26213篇 |
1998年 | 9431篇 |
1997年 | 10181篇 |
1996年 | 9591篇 |
1995年 | 9052篇 |
1994年 | 8810篇 |
1993年 | 9011篇 |
1992年 | 22707篇 |
1991年 | 22455篇 |
1990年 | 21915篇 |
1989年 | 21628篇 |
1988年 | 20050篇 |
1987年 | 19140篇 |
1986年 | 17852篇 |
1985年 | 18305篇 |
1984年 | 15265篇 |
1983年 | 13178篇 |
1982年 | 10193篇 |
1981年 | 9105篇 |
1980年 | 8675篇 |
1979年 | 14606篇 |
1978年 | 11468篇 |
1977年 | 10677篇 |
1976年 | 10176篇 |
1975年 | 11071篇 |
1974年 | 11811篇 |
1973年 | 11665篇 |
1972年 | 10725篇 |
1971年 | 9760篇 |
1970年 | 8330篇 |
1969年 | 8143篇 |
1968年 | 7462篇 |
1967年 | 6553篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
861.
862.
Jonathan D. Nickels Joseph E. Curtis Hugh O’Neill Alexei P. Sokolov 《Journal of biological physics》2012,38(3):497-505
Recent studies have discovered strong differences between the dynamics of nucleic acids (RNA and DNA) and proteins, especially at low hydration and low temperatures. This difference is caused primarily by dynamics of methyl groups that are abundant in proteins, but are absent or very rare in RNA and DNA. In this paper, we present a hypothesis regarding the role of methyl groups as intrinsic plasticizers in proteins and their evolutionary selection to facilitate protein dynamics and activity. We demonstrate the profound effect methyl groups have on protein dynamics relative to nucleic acid dynamics, and note the apparent correlation of methyl group content in protein classes and their need for molecular flexibility. Moreover, we note the fastest methyl groups of some enzymes appear around dynamical centers such as hinges or active sites. Methyl groups are also of tremendous importance from a hydrophobicity/folding/entropy perspective. These significant roles, however, complement our hypothesis rather than preclude the recognition of methyl groups in the dynamics and evolution of biomolecules. 相似文献
863.
864.
Human long-latency auditory evoked potentials were studied during simulation with variable-amplitude pulse sequences from a sound source moving to and from the subject. The N1 peak parameters were shown to depend on an accurate estimate of the direction of the change in the distance to the sound source. Differences in the processing of signals that simulated the approaching and/or distancing of the sound source were found in the N1 and P2 component parameters of on- and off-responses as was a more pronounced long negative potential shift in the evoked response to the approaching source as compared to the distancing source. 相似文献
865.
J. Dierschke T. Krüger F. Hüttmann F. Bairlein Kerstin Müller G. Scheiffarth H. -W. Helb W. Irsch W. Lantermann B. Haubitz W. Winkel und J. Haffer 《Journal of Ornithology》2003,144(4):484-498
Ohne Zusammenfassung 相似文献
866.
Simon D X Chuong Robert T Mullen Douglas G Muench 《The Journal of biological chemistry》2002,277(4):2419-2429
The control of subcellular mRNA localization and translation is often mediated by protein factors that are directly or indirectly associated with the cytoskeleton. We report the identification and characterization of a rice seed protein that possesses both RNA and microtubule binding activities. In vitro UV cross-linking assays indicated that this protein binds to all mRNA sequences tested, although there was evidence for preferential binding to RNAs that contained A-C nucleotide sequence motifs. The protein was purified to homogeneity using a two-step procedure, and amino acid sequencing identified it as the multifunctional protein (MFP), a peroxisomal enzyme known to possess a number of activities involved in the beta-oxidation of fatty acids. The recombinant version of this rice MFP binds to RNA in UV cross-linking and gel mobility shift experiments, co-sediments specifically with microtubules, and possesses at least two enzymatic activities involved in peroxisomal fatty acid beta-oxidation. Taken together these data suggest that MFP has an important role in mRNA physiology in the cytoplasm, perhaps in regulating the localization or translation of mRNAs through an interaction with microtubules, in addition to its peroxisomal function. 相似文献
867.
Conventional amperometric alcohol electrodes were constructed with oxygen- and hydrogen peroxide-base sensors and a much improved electrode was designed by placing a hydrophobic, gas-permeable membrane over the conventional hydrogen peroxide-based alcohol electrode. The immobilization of alcohol oxidase with glutaraldehyde was also studied and optimized. The upper linear ranges of the conventional and newly designed alcohol electrodes were 0.02 and 0.5% ethanol, respectively. The hydrophobic membrane of the new design eliminated the classical electrochemical interferences of hydrogen peroxide-based electrodes and the typical pH dependence of enzymatic systems. 相似文献
868.
869.
870.
K Scheuch W D Pietruschka E Hentschel P Winiecki G Gruber 《Activitas nervosa superior》1988,30(3):169-173
Biochemical and immunological parameters, physical and mental performance, subjective complaints and behavioural characteristics were compared before and after 14 final examinations undertaken by 64 students during a three-month examination period. A decrease in cholesterol, triglycerides, HDL-cholesterol, physical performance and an increase in LDL/HDL cholesterol quotient, lactate level, mental performance were accompanied by a lower frequency of mental complaints and higher frequency of physical complaints. From the multidimensional variance and discriminant analysis 17 of the 44 variables discriminated between the state prior to and after the examination period. The results are interpreted in terms of the psychophysiological adaptation to adequate mental stress. 相似文献