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51.
Evolutionary biology of parasitic platyhelminths: The role of molecular phylogenetics 总被引:4,自引:0,他引:4
As our appreciation of the diversity within the flatworms has grown, so too has our curiosity about the ways in which these varied creatures are related to one another. In particular, the parasitic groups (trematodes, cestodes and monogeneans have been the focus of enquiry. Until recently, morphology, anatomy and life histories have provided the raw data for building hypotheses on relationships. Now, ultrastructural evidence, and most recently, molecular data from nucleic acid sequences, have been brought to bear on the topic. Here, David Blair, Andrés Campos, Michael Cummings and Juan Pedro Laclette discuss the ways in which molecular data, in particular, are helping us recognize the various lineages of flatworms. 相似文献
52.
A covalently bound photoisomerizable agonist. Comparison with reversibly bound agonists at electrophorus electroplaques 下载免费PDF全文
HA Lester ME Krouse MM Nass NH Wassermann BF Erlanger 《The Journal of general physiology》1980,75(2):207-232
After disulphide bonds are reduced with dithiothreitol, trans-3- (α-bromomethyl)-3’-[α- (trimethylammonium)methyl]azobenzene (trans-QBr) alkylates a sulfhydryl group on receptors. The membrane conductance induced by this “tethered agonist” shares many properties with that induced by reversible agonists. Equilibrium conductance increases as the membrane potential is made more negative; the voltage sensitivity resembles that seen with 50 [mu]M carbachol. Voltage- jump relaxations follow an exponential time-course; the rate constants are about twice as large as those seen with 50 μM carbachol and have the same voltage and temperature sensitivity. With reversible agonists, the rate of channel opening increases with the frequency of agonist-receptor collisions: with tethered trans-Qbr, this rate depends only on intramolecular events. In comparison to the conductance induced by reversible agonists, the QBr-induced conductance is at least 10-fold less sensitive to competitive blockade by tubocurarine and roughly as sensitive to “open-channel blockade” bu QX-222. Light-flash experiments with tethered QBr resemble those with the reversible photoisomerizable agonist, 3,3’,bis-[α-(trimethylammonium)methyl]azobenzene (Bis-Q): the conductance is increased by cis {arrow} trans photoisomerizations and decreased by trans {arrow} cis photoisomerizations. As with Bis-Q, ligh-flash relaxations have the same rate constant as voltage-jump relaxations. Receptors with tethered trans isomer. By comparing the agonist-induced conductance with the cis/tans ratio, we conclude that each channel’s activation is determined by the configuration of a single tethered QBr molecule. The QBr-induced conductance shows slow decreases (time constant, several hundred milliseconds), which can be partially reversed by flashes. The similarities suggest that the same rate-limiting step governs the opening and closing of channels for both reversible and tethered agonists. Therefore, this step is probably not the initial encounter between agonist and receptor molecules. 相似文献
53.
Contrasting Effects of Fire on Arboreal and Ground‐Dwelling Ant Communities of a Neotropical Savanna
Ants are a dominant group in tropical savannas and here we examined the responses of the arboreal and ground‐dwelling ant fauna to a fire in a Neotropical savanna (cerrado) reserve in Central Brazil. Ants were collected using pitfall traps and baits placed in trees and on the ground beneath each tree. Of the 36 trees marked along two transects, half (from each transect) were burned and half not. The same trees were sampled 1 wk before and again 3 and 12 mo after the fire. Rarefaction curves and ordination analyses using data from all trees from each side of each transect indicated that overall ant species richness and composition did not change after fire. Fire, however, reduced the mean number of ant species per tree, and increased the mean number of species on the ground. Fire increased the average abundance of specialist predators, Camponotini, and opportunistic species, and decreased that of arboreal specialists. Changes in the ground‐dwelling fauna were only detected 12 mo after the fire, while those in the arboreal fauna occurred earlier and were no longer apparent 12 mo after the fire. We suggest that these contrasting results represent mainly an indirect response of the ant communities to fire‐induced changes in vegetation. Given the temporary and small scale nature of the effects detected and the overall resilience of the ant fauna, our results indicate that a single fire in the cerrado vegetation does not greatly impact the structure of ant communities in the short term. 相似文献
54.
Prof. Renato Meduri Emilio Campos Lucia Scorolli Caterina De Vinci Giancarlo Pizza Dimitri Viza 《Biotherapy》1996,9(1-3):61-66
Recurrent ocular herpes is an insoluble problem for the clinician. As cellular immunity plays an important role in controlling
herpes relapses, and other studies have shown the efficacy of HSV-specific transfer factor (TF) for the treatment of herpes
patients, an open clinical trial was undertaken in 134 patients (71 keratitis, 29 kerato-uveitis, 34 uveitis) suffering from
recurrent ocular herpetic infections. The mean duration of the treatment was 358 days, and the entire follow-up period 189121
before, and 64062 days after TF treatment. The cell-mediated immune response to the viral antigens, evaluated by the lymphocyte
stimulation test (LST) and the leucocyte migration test (LMT) (P<0.001), was significantly increased by the TF treatment.
The total number of relapses was decreased significantly during/after TF treatment, dropping from 832 before, to 89 after
treatment, whereas the cumulative relapse index (RI) dropped, during the same period, from 13.2 to 4.17 (P<0.0001). No side
effects were observed. It is concluded that patients with relapsing ocular herpes can benefit from treatment with HSV-specific
TF. 相似文献
55.
56.
Maurecilne Lemes da Silva Daniela Lopes Paim Pinto Miguel Pedro Guerra Eny Iochevet Segal Floh Cláudio Horst Bruckner Wagner Campos Otoni 《Plant Cell, Tissue and Organ Culture》2009,99(1):47-54
The objective of the present work was to induce somatic embryogenesis from zygotic embryos of Passiflora cincinnata Masters. Zygotic embryos formed calli on media with different concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) and
4.5 μM benzyladenine (BA) after 30 days of in vitro culture. A concentration of 18.1 μM 2,4-D resulted in the largest number
of somatic embryos. Embryogenic calli were yellowish and friable, forming whitish proembryogenic masses. Morphologically,
embryogenic cells were small and had large nuclei and dense cytoplasm, whereas non-embryogenic cells were elongated, with
small nuclei and less dense cytoplasm. Calli cultured under white light on basal Murashige and Skoog’s medium with activated
charcoal produced embryos in all developmental stages. There were differences among the treatments, with some leading to the
production of calli with embryos and some only to callus formation. Some abnormalities were associated with somatic embryos,
including fused axes, fused cotyledons and polycotyledonary embryos. Production of secondary somatic embryos occurred in the
first cycle of primary embryo development. Secondary embryos differentiated from the surface of the protodermal layer of primary
embryos with intense cell proliferation, successive mitotic divisions in the initial phase of embryoid development, and a
vascular system formed with no connection to the parental tissue. This secondary embryogenic system of P. cincinnata is characterized by intense proliferation and maintenance of embryogenic competence after successive subcultures. This reproducible
protocol opens new prospects for massive propagation and is an alternative to the current organogenesis-based transformation
protocol. 相似文献
57.
Amanda Ferreira da Silva Mendes Luciana Cardoso Cidade Maria Luiza Peixoto de Oliveira Wagner Campos Otoni Walter Dos Santos Soares-Filho Marcio Gilberto Cardoso Costa 《Plant Cell, Tissue and Organ Culture》2009,97(3):331-336
Identification of beta-lactam antibiotics that have negligible effects on plant regeneration is a critical step towards the
establishment of a reliable Agrobacterium-mediated transformation protocol for perennial trees. In the present report, we have evaluated the effects of the novel beta-lactam
antibiotics meropenem and timentin on plant regeneration of a perennial woody fruit plant, Citrus sinensis, in comparison with the commonly used beta-lactam cefotaxime. It was observed that, in contrast to cefotaxime, meropenem
and timentin had a positive or no detrimental effect on the shoot regeneration from epicotyl explants. Residual effects of
the beta-lactams from shoot regeneration medium also affected the subsequent ability of the roots to elongate. The addition
of meropenem and/or timentin in the rooting medium mostly improved or did not affect the rooting ability of the adventitious
shoots. These data indicated that meropenem and timentin can positively replace cefotaxime in Agrobacterium-mediated transformation of C. sinensis. 相似文献
58.
Hélia Guerra Cardoso Maria Catarina Campos Maria Salomé Pais Augusto Peixe 《In vitro cellular & developmental biology. Plant》2010,46(6):499-508
Somatic embryogenesis induction from in vitro cultured stamens and carpels is highly dependent on explants’ inoculation at specific developmental stages. To establish
good correlations between measurable morphometric parameters of flowers or flower buds and developmental stages of micro-
and macrosporogenesis, this procedure is the easiest way to simplify the in vitro culture procedures. These correlations were established here for the most important Iberian grapevine cultivar, the “Aragonez”,
named “Tempranillo” in Spain and “Tinta Roriz” in the north of Portugal, and were based in floral buds and anther measurements.
The anther length, with a correlation coefficient of 0.90, proved to be the best morphometric parameter to follow microsporogenesis
evolution. A correlation between micro- and macrosporogenesis evolutionary stages was also positively established, allowing
the use of morphometric parameters for tracking ovule evolution as well. Carpels in several evolutionary stages were in vitro cultured to evaluate the aging effect on the capacity for somatic embryogenesis induction. Explants inoculated in the earliest
stages of macrosporogenesis presented the best results. Media culture formulations were also tested for ovary culture, with
the best results being achieved with a 5:1 auxin/cytokinin ratio. 相似文献
59.
Peregrin S Jurado-Pueyo M Campos PM Sanz-Moreno V Ruiz-Gomez A Crespo P Mayor F Murga C 《Current biology : CB》2006,16(20):2042-2047
p38 Mitogen-activated protein kinases (MAPK) are a family of Ser/Thr kinases that regulate important cellular processes such as stress responses, differentiation, and cell-cycle control . Activation of MAPK is achieved through a linear signaling cascade in which upstream kinases (MAPKKs) dually phosphorylate MAPKs at a conserved 3-amino-acid motif (Thr-X-Tyr) . G-protein-coupled receptor kinases (GRKs) are known to selectively phosphorylate G-protein-coupled receptors (GPCRs) and thus trigger desensitization . We report that GRK2 is a novel inactivating kinase of p38MAPK. p38 associates with GRK2 endogenously and is phosphorylated by GRK2 at Thr-123, a residue located at its docking groove. Mimicking phosphorylation at this site impairs the binding and activation of p38 by MKK6 and diminishes the capacity of p38 to bind and phosphorylate its substrates. Accordingly, p38 activation is decreased or increased when cellular GRK2 levels are enhanced or reduced, respectively. Changes in GRK2 levels and activity can modify p38-dependent processes such as differentiation of preadipocytic cells and LPS-induced cytokine release, enhanced in macrophages from GRK2(+/-) mice. Phosphorylation of p38 at a region key for its interaction with different partners uncovers a new mechanism for the regulation of this important family of kinases. 相似文献