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31.
Demonstration of the ascorbate dependence of membrane-bound dopamine beta-monooxygenase in adrenal chromaffin granule ghosts 总被引:1,自引:0,他引:1
H H Herman K Wimalasena L C Fowler C A Beard S W May 《The Journal of biological chemistry》1988,263(2):666-672
Chromaffin granule ghosts from bovine adrenal medullae have been used to examine the ability of membrane-bound dopamine beta-monooxygenase to interact directly with intravesicular ascorbate and to investigate vectorial electron transfer from external ascorbate across the ghost membrane. Ghosts prepared by a modification of published procedures were shown to be fully active in both dopamine uptake and norepinephrine production. Dopamine uptake is dependent on the presence of a magnesium and ATP ionic complex, is abolished by reserpine, and reaches a steady-state level in the presence of dopamine beta-monooxygenase, ascorbate, catalase, and fumarate. Omission of ascorbate either inside or outside the ghosts greatly enhances dopamine accumulation, which reaches levels of approximately 30 nmol/mg under these conditions. Correspondingly, in the presence of all components, norepinephrine production reached approximately 100 nmol/mg in 30 min of incubation. Norepinephrine production was strictly magnesium-ATP-dependent, inhibited by either reserpine or dopamine beta-monooxygenase inactivation, and was markedly reduced when ascorbate was omitted from either inside or outside the ghosts. In the presence of limiting amounts of internal ascorbate, rapid norepinephrine production occurred which corresponded to the amount of initial ascorbate present, followed by a much slower endogenous norepinephrine production observable after complete depletion of internal ascorbate. The endogenous rate of norepinephrine production likely represents epinephrine-supported dopamine beta-monooxygenase turnover. Taken together, the data demonstrate that facile norepinephrine production by membrane-bound dopamine beta-monooxygenase occurs only when internal ascorbate is present, terminates upon depletion of internal ascorbate, and can only be sustained at a significant rate when reducing equivalents from external ascorbate are available. 相似文献
32.
Selected pairs of protonated ribosomal proteins were reconstituted into deuterated 50S subunits from Escherichia coli ribosomes. The rRNA of the deuterated ribosomal matrix was derived from cells grown in 76% D2O, the deuterated protein moiety from cells grown in 84% D2O. This procedure warrants that the coherent neutron scattering of deuterated proteins and rRNA is nearly the same and equals that of a D2O solution of approximately 90%. The neutron scattering is recorded in a reconstitution buffer containing approximately 90% D2O. The result is a significant improvement of the coherent signal:noise ratio over traditional methods; due to this dilute solutions can be used, thus preventing unfavorable inter-particle effects. From the diffraction pattern the distance between the mass centers of gravity of the two protonated proteins can be deduced. In this way, 50 distances between proteins within the large subunit have been determined which provide a basis for future models of the large ribosomal subunit describing the spatial distribution of the ribosomal proteins. A model containing seven ribosomal proteins is presented. 相似文献
33.
We have cloned and sequenced the p53-encoding cDNA of rainbow trout (Salmo gairdneri). The encoded product contains the characteristics found in all p53 proteins: (i) the five highly conserved domains, (ii) an acidic N terminus, (iii) a hydrophilic C terminus, and (iv) a penultimate serine residue. Furthermore, we demonstrate that the rainbow trout p53 is able to specifically interact with the SV40 large T antigen. 相似文献
34.
R M Anderson R M May T W Ng J T Rowley 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1992,336(1277):135-155
A mathematical model of the transmission of HIV-1 within heterosexual populations in Sub-Saharan Africa is described and its properties analysed. The model incorporates epidemiological and demographic processes and extends previous work in this area via the inclusion of age and sex dependency in rates of sexual partner change, and sexual partner choice dependent on age. Parameter assignments are made on the basis of current data on the transmission dynamics of HIV-1 and the demography of human populations in Africa. Both age-dependent rates of sexual activity and the sexual contact of males with females younger than themselves act to enhance the predicted demographic impact. With realistic parameter values, the model suggests AIDS is able to reverse the sign of population growth rates from positive to negative values over a timescale of a few decades. The sensitivity of this prediction is examined in relation to changes in the pattern of sexual contact between different age classes of females and males, different patterns of change in the age-dependent rate of sexual partner change, different assumptions concerning the doubling time of the epidemic in its early stages, and the relative efficiencies of viral transmission between men and women, and vice versa. The impact AIDS is predicted to have on the number of young and elderly persons as a fraction of the number of productive adults (the dependancy ratio) is examined under various assumptions concerning the weighting to be applied to mirror the burden imposed by the care of those with AIDS. The paper includes an assessment of the influence of the timing of changes in sexual behaviour, or the promotion of the use of condoms, on the predicted course of the epidemic. The paper concludes with a discussion of data needs and the model refinements required to more accurately mirror current understanding of the epidemiology of HIV-1. 相似文献
35.
Hans Fricke Karen Hissmann Jürgen Schauer Olaf Reinicke Lutz Kasang Raphael Plante 《Environmental Biology of Fishes》1991,32(1-4):287-300
Synopsis In 1987 and 1989 coelacanths were observed for the first time in their natural habitat with the help of submersibles. Coelacanths were found between 150–253 m depth, their preferential depth seems to be around 200 m; the water temperature ranged between 16.5–22.8° C. During the day coelacanths aggregate in small non-aggressive groups in sheltered lava-caves. Caves might be a limiting factor for distribution. At night they leave the caves for hunting by drifting singly along the steep lava slopes. They migrate between different caves located within a large home range covering more than 8 km coastline. Coelacanths are site-attached, some for a period of at least 2 years. Our own observations and earlier catch records show that only the west coast of Grand Comoro is a suitable coelacanth habitat with more structural complexity and prey fish abundance than other coastlines of the island. From our survey we estimated a total coelacanth population off Grand Comoro to be 150–210 individuals; a saturated population would be 370–510 individuals. This small relict population seems to be stable. International protection of coelacanths against commercial interests is needed 相似文献
36.
Intranuclear distribution of SV40 large T-antigen and transformation-related protein p53 in abortively infected cells 总被引:2,自引:0,他引:2
The intranuclear localization of SV40 T-antigen (T-Ag) and the cellular protein p53 was studied in SV40 abortively infected baby mouse kidney cells using two complementary methods of ultrastructural immunocytochemistry in combination with preferential staining of nuclear RNP components and electron microscope autoradiography. Both proteins were revealed in association with peri- and interchromatin RNP fibrils containing the newly synthesized hnRNA. In addition, T-Ag and p53 remained bound, at least in part, to the residual internal nuclear matrix following nuclease and salt extractions of infected cells. The localization of T-Ag was different in SV40 lytically infected monkey kidney cells since, in addition to hnRNP fibrils, the viral protein was also associated with cellular chromatin. However, when lytic infection was performed in conditions of blocked viral DNA replication, T-Ag was no longer associated with the cellular chromatin but remained bound to the hnRNP fibrils. We conclude that the transforming and lytic functions of T-Ag can be distinguished by different subnuclear distributions. The significance of the association of T-Ag and p53 with hnRNP fibrils and the internal nuclear matrix is discussed in relation to the role of these structures in the control of cellular mRNA biogenesis. 相似文献
37.
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40.
Prostaglandin E2 regulates macrophage-derived tumor necrosis factor gene expression 总被引:42,自引:0,他引:42
S L Kunkel M Spengler M A May R Spengler J Larrick D Remick 《The Journal of biological chemistry》1988,263(11):5380-5384