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I. Wanner Stephan L. Baader Manfred Brich John Oberdick K. Schilling 《Histochemistry and cell biology》1997,108(4-5):345-357
27.
Wolfgang Stephan 《Journal of mathematical biology》1995,34(1):95-109
A population genetic two-locus model with additive, directional selection and recombination is considered. It is assumed that recombination is weaker than selection; i.e., the recombination parameter r is smaller than the selection coefficients. This assumption is appropriate for describing the effects of two-locus selection at the molecular level. The model is formulated in terms of ordinary differential equations (ODES) for the gamete frequencies x = (x
1, x
2, x
3, x
4), defined on the simplex S
4. The ODEs are analyzed using first a regular pertubation technique. However, this approach yields satisfactory results only if r is very small relative to the selection coefficients and if the initial values x(0) are in the interior part of S
4. To cope with this problem, a novel two-scale perturbation method is proposed which rests on the theory of averaging of vectorfields. It is demonstrated that the zeroth-order solution of this two-scale approach approximates the numerical solution of the model well, even if recombination rate is on the order of the selection coefficients. 相似文献
28.
Cyanopeptolin S, a sulfate-containing depsipeptide from a water bloom of Microcystis sp. 总被引:1,自引:0,他引:1
Clemens Jakobi Lukas Oberer Charles Quiquerez Wilfried A. König Jürgen Weckesser 《FEMS microbiology letters》1995,129(2-3):129-133
Abstract A new sulfated, cyclic depsipeptide, called cyanopeptolin S, from Microcystis sp. was isolated from a water bloom in the Auensee/Leipzig (Germany). The depsipeptide had a relative molecular mass of 925 and contained l-arginine, l-threonine, l-isoleucine, N-methyl-l-phenylalanine, a l-glutamic acid-δ-aldehyde ring system and a sulfated d-configurated glyceric acid as a side chain. The structure was elucidated by means of two-dimensional 1 H and 13 C nuclear magnetic resonance spectroscopy, fast atom bombardment mass spectroscopy, Fourier transformed infrared spectroscopy and combined gas-liquid chromatography/mass spectrometry. Cyanopeptolin S inhibited trypsin with an IC50 ≤ 0.2 μg ml−1 . 相似文献
29.
Differential kinetics of changes in the state of phosphorylation of ribosomal protein S6 and in the rate of protein synthesis in MPC 11 cells during tonicity shifts 总被引:6,自引:0,他引:6 下载免费PDF全文
Mouse myeloma (MPC 11) cells respond rapidly to hypertonic conditions by shutting down protein synthesis at the level of polypeptide chain initiation. Translational activity recovers equally quickly upon a return to isotonicity. Disaggregation and reformation of polysomes occur in parallel to the changes in protein synthesis. Ribosomal protein S6 becomes dephosphorylated under hypertonic conditions and rephosphorylated when isotonic conditions are restored. The kinetics with which these changes occur are, however, too slow to account for the changes in protein synthesis. Treatment of the cells with a low concentration of cycloheximide allows reformation of polysomes under hypertonic conditions; conversely, puromycin prevents the restoration of polysomes which otherwise occurs on return to isotonicity. Neither inhibitor prevents the changes in S6 phosphorylation resulting from the tonicity shifts. We conclude that the overall extent of phosphorylation of S6 neither regulates nor is determined by the rate of protein synthesis and is not obligatorily related to the proportion of ribosomes in polysomes. 相似文献
30.
Robert P. Casey Clemens Broger Marcus Thelen Angelo Azzi 《Journal of bioenergetics and biomembranes》1981,13(5-6):219-228
We report here studies which characterize further the interaction ofN,N-dicyclohexylcarbodiimide with cytochromec oxidase leading to inhibition of H+ translocation by the enzyme. Further evidence is presented to show that the inhibition results from a real interaction of DCCD with the enzyme and cannot be accounted for by uncoupling and, contrary to recent criticisms, this interaction occurs specifically with subunit III of the enzyme even at relatively high inhibitor-to-enzyme stoichiometries. Use of a spin-label analogue of DCCD has enabled us to demonstrate that the carbodiimide-binding site is highly apolar and may not lie on the pathway of electron transfer.Abbreviations DCCD
N,N-dicyclohexylcarbodiimide
- NCCD
N-(2, 2, 6, 6-tetramethylpiperidyl-1-oxyl)-N-(cyclohexyl)carbodiimide
- Hepes
2-(N-2-hydroxyethylpiperazin-N-yl) ethane sulfonate
- TMPD
N,N,N,N-tetramethylphenylenediamine 相似文献