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Serotonin Inhibits Acetylcholine Release from Rat Striatum Slices: Evidence for a Presynaptic Receptor-Mediated Effect 总被引:4,自引:2,他引:2
Rat brain striatum slices were incubated with [3H]choline, perfused with a physiological buffer, and stimulated by perfusion with a K+-enriched buffer for 2 min. The tritium overflow evoked by K+ was decreased by 5-hydroxytryptamine (serotonin, 5-HT) (maximal inhibition 10(-6) M). This effect of 5-HT was mimicked by several agonists (5-methoxytryptamine, N,N-dimethyl-tryptamine, bufotenin) and blocked by serotonergic antagonists (methiothepin, methysergide, cinanserin) but not by haloperidol; methiothepin and methysergide alone slightly increased the K+-evoked overflow of tritium (3H). Inhibition of the tritium release by 5-HT was not suppressed in the presence of tetrodotoxin (TTX) (10(-6) M). These results suggest that 5-HT tonically inhibits acetylcholine (ACh) release from striatal cholinergic neurons by acting on a presynaptic receptor localized on cholinergic terminals. 相似文献
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Selection in plant populations of effectively infinite size. V. Biallelic models of trioecy 下载免费PDF全文
A one-locus two-allele model of trioecy (presence of hermaphrodites, males and females in one population) is considered, in order to study the conditions for the persistence of this system. All possible assignments of the three sex types to the three genotypes are considered. This leads to three different modes of inheritance of trioecy, namely (a) females heterozygous, (b) males heterozygous and (c) hermaphrodites heterozygous, where in each mode each of the remaining two sex types is homozygous for one of the alleles. For mode (c) trioecy is always persistent, and the dependence of the sex ratio (for the three sex types) on the ovule and pollen fertilities and on the hermaphrodite selfing rate is specified. For the other two modes, (a) and (b), trioecy is not protected, i.e., it may not persist for any fertilities, viabilities or selfing rates. Thus, in this situation it is important to study the conditions under which the "marginal" systems of sexuality of trioecy, i.e., hermaphroditism, dioecy and gynodioecy in mode (a), and hermaphroditism, dioecy and androdioecy in mode (b), may become established. The results show that each marginal system may evolve from each other via trioecy. The evolution of dioecy is easier in mode (a) than in (b), so that female heterogamety would be expected to occur more often than male heterogamety in the present model. Under some conditions the breeding system obtained in equilibrium populations may depend on the initial genotype frequencies.—The necessity of considering modes of inheritance for sexual polymorphisms is demonstrated by comparing our results with those obtained from an evolutionary stable strategy (ESS) analysis of a purely phenotypic model. 相似文献
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Résumé A la suite de recherches antérieures intéressant la vascularisation de la trompe utérine et celle de l'ovaire, la présente étude concerne la microvascularisation de la muqueuse vaginale chez la Femme et se fonde sur l'examen de dix vagins humains prélevés chez des sujets en période d'activité génitale, vagins dont le système vasculaire est injecté à l'encre de Chine gélosée.L'étude de l'angioarchitectonie de la muqueuse vaginale en général laisse apparaître un dispositif vasculaire spécifique de cette dernière et représenté au niveau du chorion par des artérioles superficielles qui s'arborisent en de multiples branches se résolvant en un réseau capillaire sous-muqueux; ce dernier est constitué d'une part, d'un dense réseau capillaire à mailles ovalaires ou polygonales, étalé sous la couche basale de l'épithélium malpighien, d'autre part, d'anses capillaires intra-papillaires, sensiblement perpendiculaires à l'épithélium malpighien et se répétant à intervalles réguliers. Ce réseau capillaire est draîné par un plexus veineux étendu que résument de volumineuses veines au calibre irrégulier.Les variations de cette angioarchitectonie au cours des diverses phases du cycle ovarien sont essentiellement marquées au cours de la 2e phase de ce cycle où elles se caractérisent par une augmentation de calibre des artérioles comme des capillaires et surtout par l'accroissement de la hauteur et de la spiralisation des anses capillaires.
The angioarchitectony of the submucous network of the human vagina and its variations during the ovarian cycle
Summary The microvascularization of the vaginal mucosa has been investigated on 10 human vaginae taken from autopsies of women having been in their sexual active period, the vascular system of the vaginae being injected with solutions of China ink and gelose.The angioarchitectony of the vaginal mucosa shows a specific vascular pattern. The latter is represented at the level of the stroma by superficial arterioles which divide into multiple branches giving rise to the submucous capillary network. This network consists on one hand of a thick capillary plexus with ovale or polygonal stitches, spread under the basal layer of the malpighian epithelium, and on the other hand of intrapapillary capillary creeks arranged in regular intervals and perpendicularly oriented to the malpighian epithelium. This capillary network is drained by a wide spread venous plexus connected with big veins of irregular calibre.The variations of this angioarchitectony are especially pronounced during the second part of the menstrual period, when the calibre of the arterioles as well as that of the capillaries creeks grow in height and become spiralized.相似文献
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Summary Exchange isotherms of Cu2+
vs Zn2+-ions were performed on the cell wall of a fresh water alga,Nitella flexilis. The relevant thermodynamic parameters are calculated. The cell wall absorbs copper selectively. The selectivity is explained
by a stronger chelation of the cupric ion, due to the Jahn-Teller effect. The wall acts like a two-site model, based on the
nature of the ligands: a first group of aminesites reacts exothermically and a second of hydroxylic-carboxylic sites of lower
affinity, reacts endothermically. 相似文献