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排序方式: 共有392条查询结果,搜索用时 31 毫秒
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A. Tyagi J. Hermans J. Steppuhn Ch. Jansson F. Vater R. G. Herrmann 《Molecular & general genetics : MGG》1987,207(2-3):288-293
Summary Several cDNA clones encoding the 33 kDa protein associated with the photosynthetic water oxidation activity of spinach were sequenced. A 1208 bp insert of one of the clones encodes the entire 331 amino acid residues of the precursor protein including 84 amino acids (8.5 kDa) of the amino-terminal transit peptide, 49 bp of the 5 and 111 bp of the 3 untranslated segment of the mRNA. The 3 poly(A) tail starts 19 bp downstream from a putative polyadenylation signal, TATAAA. The hydrophilic mature protein consists of 247 amino acid residues corresponding to an Mr of 26.5 kDa, which is 6.5 kDa smaller than the value determined by SDS-polyacrylamide gel electrophoresis (33–34 kDa), and shows a certain degree of conservation with the putative Mn-complexing active sites of bacterial Mn-dependent superoxide dismutases. The anatomy of the unusually long transit sequence is discussed with regard to current concepts of protein import into and protein routein within the organelle. 相似文献
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J. T. Keltjens J. M. H. Hermans G. J. F. A. Rijsdijk C. Van der Drift G. D. Vogels 《Antonie van Leeuwenhoek》1988,54(3):207-220
F430 is the prosthetic group of the methylcoenzyme M reductase of methanogenic bacteria. The compound isolated from Methanosarcina barkeri appears to be identical to the one obtained from the only distinctly related Methanobacterium thermoautotrophicum. F430 is thermolabile and in the presence of acetonitrile or C10
in4
sup-
two epimerization products are obtained upon heating; in the absence of these compounds F430 is oxidized to 12, 13-didehydro-F430. The latter is stereoselectively reduced under H2 atmosphere to F430 by cell-free extracts of M. barkeri or M. thermoautotrophicum. H2 may be replaced by the reduced methanogenic electron carrier coenzyme F420.Abbreviations CH3S-CoM
methylcoenzyme M, 2-methylthioethanesulfonic acid
- HS-CoM
coenzyme M, 2-mercaptoethanesulfonic acid
- F430
Ni(II) tetrahydro-(12, 13)-corphin with a uroporphinoid (III) ligand skeleton
- 13-epi-F430 and 12,13-di-epi-F430
the 12, 13- and 12, 13-derivatives of F430
- 12, 13-didehydro-F430
F430 oxidized at C-12 and C-13
- coenzyme F420
7,8-didemethyl-8-hydroxy-5-deazaflavin derivative
- coenzyme F420H2
reduced coenzyme F420
- MV+
methylviologen semiquinone
- HPLC
high-performance liquid chromatography 相似文献
6.
Jochen Tittgen Jürgen Hermans Johannes Steppuhn Thomas Jansen Christer Jansson Bertil Andersson Rachel Nechushtai Nathan Nelson Reinhold G. Herrmann 《Molecular & general genetics : MGG》1986,204(2):258-265
Summary Spinach cDNA libraries, made from polyadenylated seedling RNA, have been constructed in pBR322 and the expression vector gt11. Recombinant plasmids or phage for 14 intrinsic and peripheral thylakoid membrane proteins and one stromal protein have been identified. They encode components containing antigenic determinants against the lysine-rich 34 kd, the 23 kd and 16 kd proteins all associated with the water-splitting apparatus of the photosystem II reaction center, the ATP synthase subunits gamma, delta and CFo-II, the Rieske Fe/S protein of the cytochrome b/f complex, subunits 2, 3, 5 and 6 of the photosystem I reaction center, plastocyanin, ferredoxin oxidoreductase, chlorophyll a/b-binding apoproteins of the lightharvesting complex associated with photosystem II, and the small subunit of the stromal enzyme ribulose bisphosphate corboxylase/oxygenase. The cDNA inserts lack complementarity to plastid DNA but hybridize to restricted nuclear DNA as well as to discrete poly A+-mRNA species. The precursor products obtained after translation of hybrid selected RNA fractions in a wheat germ assay are imported and processed by isolated unbroken spinach chloroplasts. The imported components comigrate with the respective authentic proteins. 相似文献
7.
The current system in Britain for compensating victims of medical injury depends on an assessment of negligence. Despite the sporadic pressure on the government to adopt a "no fault" approach, such as exists in Sweden, the negligence system will probably remain for the immediate future. The cost of this system was estimated to be 52.3m pounds for England 1990-1. The problem for the future, however, is one of forecasting accuracy at provider level: too high a guess and current patient care will suffer; too low a guess and future patient care will suffer. The introduction of a mutual insurance scheme may not resolve these difficulties, as someone will have to set the rates. Moreover, the figures indicate that if a no fault scheme was introduced the cost might be four times that of the current system, depending on the type of scheme adopted. 相似文献
8.
I. J. Hermans 《Neurochemical research》1978,3(6):711-724
-Glucosidase activity has been determined in homogenate and in centrifugation fractions of 7-day-old and adult rat brain; maximum activity was found at pH 4 and pH 5. Of the adult brain, more than 50% of the activity was concentrated in the 800-g sediment fraction (P1), while in the brain of 7-day-old rat about 20% was found in the corresponding fraction. The activity maximum in all fractions after a 2% Triton X-100 treatment occurs at pH 5. Addition of Triton to adult brain homogenate enhances the activity, but this stimulation is less than the sum of the activities observed at pH 4 and pH 5 in the absence of Triton. Triton addition to brain homogenate of 7-day-old rat results in a fall in activity at pH 4 and in a maximum at pH 5. In rat brain homogenate subjected to sonication, a loss of activity is observed at pH 4, scarcely at pH 5; the activity loss is completely abolished and turned into an increase under the influence of Triton. This increase equals the level obtained when Triton is added to an untreated brain homogenate. Sonication of rat brain homogenate leads to changes in the distribution pattern; about 25% of the activity of the adult brain is found in the P1 fraction compared to 50% in the corresponding fraction of the untreated brain. Fractionation of a sonicated brain homogenate from adult rat reveals that at pH 4 most activity (52%) is concentrated in the 20,000-g pellet (P2), 23% in supernatant fluid (S2); at pH 5 the opposite is observed: most activity (49%) is found in the 20,000-g supernatant (S2) and 23% in the 20,000-g pellet (P2). In the presence of Triton the activity of the sonicated brain homogenate of adult rat increases; this stimulation roughly equals the sum of the corresponding activities measured at pH 4 and pH 5 in the absence of Triton. 相似文献
9.
A. van Rotterdam F. H. Lopes da Silva J. van den Ende M. A. Viergever A. J. Hermans 《Bulletin of mathematical biology》1982,44(2):283-305
A linear spatially distributed model of a chain of neurons and interneurons was investigated in relation to the generation
of propagated alpha rhythmic activity. It was assumed that the elements of the chain were interconnected by means of recurrent
collaterals and inhibitory fibres in such a way that the connectivity functions were assumed to be homogeneous and their strength
was an exponentially decreasing function of distance. It was found that such a neuronal chain shows propagation properties
for frequencies in the alpha band. The results obtained with the model are in agreement with the phase velocities encountered
experimentally. In this way, it was possible to estimate the length of the neural fibres responsible for the phenomenon of
propagated activity. The estimates obtained are in good agreement with recent quantitative neuroanatomical data on the circuitry
of the neocortex. 相似文献
10.
Characterization of the inhibition of fibrin assembly by fibrinogen fragment D. 总被引:2,自引:0,他引:2 下载免费PDF全文
Fragment D (Mr 100 000) prepared from a terminal plasmin digest of fibrinogen was isolated and used to study its effect on fibrin formation. Increasing amounts of fragment D added to a solution of fibrinogen and thrombin decrease the rigidity of the resultant gel (10% of control at 2 mol of fragment D/mol of fibrinogen). Half-maximal inhibition is achieved at 1 mol of fragment D/mol of fibrinogen for non-cross-linked clots and at 1/2 mol of fragment D/mol of fibrinogen for cross-linked clots. "Clottability' decreases concomitantly with the rigidity. Only small amounts of fragment D (less than 10% for non-cross-linked gels) are incorporated into the gel. Light-scattering shows an increase in the final fibre thickness at fragment D concentrations up to 2 mol of fragment D/mol of fibrinogen, from 60 molecules/cross-section for the control to 120 molecules/cross-section. Higher fragment D concentrations lead to a decrease in the final fibre thickness. The limit fibre thickness is 8 nm, with a length of 80 nm, which is equivalent to a fibrin trimer. On the basis of results of synthetic-substrate and fibrinopeptide-release assays, it is clear that thrombin inactivation is not responsible for this effect. These data suggest that fragment D may inhibit fibrin formation by blocking the bimolecular polymerization of activated fibrin monomer molecules to form protofibrils, although additional effects on subsequent assembly steps may also be involved. 相似文献