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51.
The diterpene forskolin stimulated rat cardiac adenylate cyclase activity at least 20-fold and potentiated the effect of NaF. The stimulatory effect of forskolin was reduced in the presence of Gpp(NH)p. Ethanol markedly reduced the stimulation of adenylate cyclase by forskolin while potentiating NaF and Gpp(NH)p stimulation. The inhibitory effect of ethanol on forskolin stimulation appeared to be of a mixed type with both a competitive and a non-competitive component. Three other short-chain linear alcohols (methanol, propanol, butanol) also inhibited forskolin-stimulation, this effect being proportional to the number of carbon atoms. 相似文献
52.
Isolated muscle cells from adult rat heart have been used to study the relationship between myocardial glucose transport and the activity of the Na+/K+ pump. 86Rb+-uptake by cardiac cells was found to be linear up to 2 min with a steady-state reached by 40–60 min, and was used to monitor the activity of the Na+/K+ pump. Ouabain (10?3 mol/I) inhibited the steady-state uptake of 86Rb+ by more than 90%. Both, the ouabain-sensitive and ouabain-insensitive 86Rb+-uptake by cardiac cells were found to be unaffected by insulin treatment under conditions where a significant stimulation of 3-O-methylglucose transport occurred. 86Rb+-uptake was markedly reduced by the presence of calcium and/or magnesium, but remained unresponsive towards insulin treatment. Inhibition of the Na+/K+ pump activity by ouabain and a concomitant shift in the intracellular Na+:K+ ratio did not affect basal or insulin stimulated rates of 3-O-methylglucose transport in cardiac myocytes. The data argue against a functional relationship between the myocardial Na+/K+ pump and the glucose transport system. 相似文献
53.
Summary Inward-rectifier channels in cardiac cells (I
K1) stabilize the resting membrane potential near the K equilibrium potential. Here we investigate the role ofI
K1 in the regulation of action potentials and link this to the influx of Ca during beating. Inward Ca current alters the open-channel probability of outwardI
K1 current. Thus Ca ions depolarize cells not only by carrying an inward current but also by blocking an outward current. 相似文献
54.
The interactions of Heterodera glycines at four egg inoculum levels (0, 100, 1,000, and 10,000 per pot) and three cyst levels (0, 100, and 200 per pot) and Calonectria crotalariae at 500, 5,000, and 50,000 microsclerotia per pot were evaluated on soybean. At the two lowest nematode egg levels, the presence of C. crotalariae did not affect nematode reproduction. At 10,000 eggs per pot, however, nematode reproduction was increased significantly at each microsclerotial level. The increase in nematode reproduction was stepwise at 500 and 5,000 microsclerotia per pot but declined at 50,000 microsclerotia per pot. Similar results were obtained when cysts rather than eggs were used as nematode inoculum. The nematode x fungus interaction significantly affected 60-day plant growth parameters of both Lee 74 and Centennial soybean. The nematode x fungus interaction was antagonistic to plant roots and significantly influenced root injury ratings. The presence of C. crotalariae in tissues of stock plants or plants used as race differentials did not alter the analysis of this population as race 3. 相似文献
55.
The increase in bare patch of cereals associated with minimum tillage practices prompted an investigation of the relationship between soil compaction and saprophytic growth of Rhizoctonia solani. In soils wetter than 10 kPa there was a greater density of hyphae in compacted than in non-compacted soil. In relatively dry soil, however, there was wider exploration by hyphae in non-compacted than in compacted soil. The implications of these findings for disease management are discussed. 相似文献
56.
We studied the hexose transporter protein of the frontal and temporal neocortex, hippocampus, putamen, cerebellum, and cerebral microvessels (which constitute the blood-brain barrier) in Alzheimer disease and control subjects by reversible and covalent binding with [3H]cytochalasin B and by immunological reactivity. In Alzheimer disease subjects, we found a marked decrease in the hexose transporter in brain microvessels and in the cerebral neocortex and hippocampus, regions that are most affected in Alzheimer disease, but there were no abnormalities in the putamen or cerebellum. Hexose transporter reduction in cerebral microvessels of Alzheimer subjects is relatively specific because other enzyme markers of brain endothelium were not significantly altered. The low density of the hexose transporter at the blood-brain barrier and in the cerebral cortex in Alzheimer disease may be related to decreased in vivo measurements of cerebral oxidative metabolism. 相似文献
57.
Mar Pérez José M. Valpuesta Miguel Medina Esteban Montejo de Garcini Jesús Avila 《Journal of neurochemistry》1996,67(3):1183-1190
Abstract: Paired helical filaments isolated from the brains of patients with Alzheimer's disease are composed of a major protein component, the microtubule-associated protein termed τ, together with other nonprotein components, including heparan, a glycosaminoglycan, the more extensively sulfated form of which is heparin. As some of these nonprotein components may modulate the assembly of τ into filamentous structures, we have analyzed the ability of the whole τ protein or some of its fragments to self-assemble in the presence of heparin. Different τ fragments, all of them containing some sequences of the tubulin-binding motif, can assemble in vitro into filaments. We have also found formation of polymers with the 18-residue-long peptide corresponding to the third tubulin-binding motif of τ. This suggests that the ability of τ for self-assembly could be localized in a short sequence of amino acids present in the tubulin-binding repeats of the τ molecule. 相似文献
58.
† Ken-ichiro Fukuchi †Tauni Ohman Nocthao Dang Anetta C. Smith ‡Clement E. Furlong George M. Martin 《Journal of neurochemistry》1996,66(5):2201-2204
Abstract: P19 is a C3H mouse-derived line of multipotent embryonic carcinoma cells that differentiate into neural cells. P19 cell clones overexpressing the three major forms of β-amyloid precursor protein from their cDNA constructs were established. Unlike a previous study in which P19-derived neurons had a limited α-secretase activity, all of these clones produced significant amounts of secreted β-amyloid precursor protein. When treated with retinoic acid, these transformed lines differentiated into neurons and survived better than did nontransformed parental P19 cells. Furthermore, P19-derived neurons survived better in medium conditioned by the transformed P19 line, and survival was reduced by immunoabsorption with an antibody to β-amyloid precursor protein. These results suggest neurotrophic effects of secreted β-amyloid precursor protein and contrast with a previous report in which overexpression of a full-length cDNA for β-amyloid precursor protein led to degeneration of P19-derived neurons. Western blot analysis suggested that this difference might result from different levels of expression of putative neurotoxic C-terminal fragments of β-amyloid precursor protein; moreover, P19-derived neurons differ from P19 stem cells in the processing of these C-terminal fragments. 相似文献
59.
60.
Mary Jeanne Kreek 《Neurochemical research》1996,21(11):1469-1488
The early history of research on the possible existence of specific opioid receptors and on developing a new form of pharmacotherapy
for the treatment of heroin addiction in New York City, from 1960–1973, along with the special relationships between two leading
scientists conducting these research efforts, Dr. Eric Simon and Dr. Vincent P. Dole Jr., are presented in a historical perspective.
The linkage of these early efforts and the subsequent identification and the elucidation of the effects of exogenous opiates
acting at specific opiate receptors in human physiology, including some findings from perspective studies of heroin addicts
at time of entry to and during methadone maintenance treatment, are presented in the context of the important clues which
thereby were provided concerning the possible roles of the endogenous opioids in normal mammalian physiology. From many of
these early clinical research findings and studies in animal models, the hypothesis that the endogenous opioids system may
play an important role in stress responsivity was formulated along with the related hypothesis, first presented in the early
1970s, that an atypical responsivity to stress and stressors might be involved in the acquisition and persistence of, and
relapse to specific addictive diseases, including heroin addiction, cocaine dependency and alcoholism. More recent studies
of the possible involvement of the specific opioid receptors in these three addictive diseases—heroin addiction, cocaine addiction
and alcoholism—from our laboratory are discussed in a historical perspective of the development of these ideas from the early
research findings of not only Dr. Eric Simon, but his numerous colleagues in opioid research in the United States and throughout
the world.
Special issue dedicated to Dr. Eric J. Simon. 相似文献