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81.
82.
Elena Gonella Rosemarie Tedeschi Elena Crotti Alberto Alma 《Entomologia Experimentalis et Applicata》2019,167(3):171-185
Some pathogenic phloem‐limited bacteria are a major threat for worldwide agriculture due to the heavy economic losses caused to many high‐value crops. These disease agents – phytoplasmas, spiroplasmas, liberibacters, and Arsenophonus‐like bacteria – are transmitted from plant to plant by phloem‐feeding Hemiptera vectors. The associations established among pathogens and vectors result in a complex network of interactions involving also the whole microbial community harboured by the insect host. Interactions among bacteria may be beneficial, competitive, or detrimental for the involved microorganisms, and can dramatically affect the insect vector competence and consequently the spread of diseases. Interference is observed among pathogen strains competing to invade the same vector specimen, causing selective acquisition or transmission. Insect bacterial endosymbionts are another pivotal element of interactions between vectors and phytopathogens, because of their central role in insect life cycles. Some symbionts, either obligate or facultative, were shown to have antagonistic effects on the colonization by plant pathogens, by producing antimicrobial substances, by stimulating the production of antimicrobial substances by insects, or by competing for host infection. In other cases, the mutual exclusion between symbiont and pathogen suggests a possible detrimental influence on phytopathogens displayed by symbiotic bacteria; conversely, examples of microbes enhancing pathogen load are available as well. Whether and how bacterial exchanges occurring in vectors affect the relationship between insects, plants, and phytopathogens is still unresolved, leaving room for many open questions concerning the significance of particular traits of these multitrophic interactions. Such complex interplays may have a serious impact on pathogen spread and control, potentially driving new strategies for the containment of important diseases. 相似文献
83.
Hammond Hammond Stacy Denise Viehmannova Iva Zamecnik Jiri Panis Bart Hlasna Cepkova Petra 《Plant Cell, Tissue and Organ Culture》2019,138(3):559-570
Plant Cell, Tissue and Organ Culture (PCTOC) - Slow-growth is a biotechnological tool for medium-term conservation of plant germplasm under in vitro conditions. In the present study, we assessed... 相似文献
84.
In studies investigating adverse reproductive outcomes associated with video display terminal (VDT) usage, amounts of time spent in front of a VDT or magnetic field (MF) levels in front of the VDT are used as surrogate measures of subject's MF exposure. However, the relevance of such surrogates to actual exposures has not been demonstrated, and the validity of the use of such measures as a surrogate for the actual MF exposure is only speculative. This study examines 1) measurements of MFs at frequencies of approximately 30–1000 Hz at a fixed distance from the VDTs, 2) reported hours of VDT use, and 3) reported distance between the VDT and the subject's waist as surrogate measures for the average MF exposure level of a VDT user during one 8 h workday. The results showed a weak correlation between the average exposure level of a VDT user and the MF 46 cm from a VDT (R = 0.52, n = 67, P < 0.001). This study showed no association between self-reported hours of VDT usage, or self-reported distance between waist and VDT, and the average MF exposures. Moreover, individuals' average MF exposures did not seem to be affected by other variables, such as position of a VDT on the desk, hours of desk use, and the VDT type (color vs. monochrome). These findings indicate that VDT exposures within office settings are complex and cannot be easily predicted by surrogates. © 1996 Wiley-Liss, Inc. 相似文献
85.
The activities of alkaline phosphatase and phosphoamino acid phosphatases were measured in normal and cancerous regions of the human larynx. For each larynx, alkaline phosphatase and phosphotyrosine phosphatase activities were higher in the tumor than in the corresponding normal tissue. Phosphothreonine and phosphoserine phosphatase activities were relatively low and there were no consistent trends. The increased alkaline phosphatase activity in the tumors supports histological observations that ossification of cartilage seems to occur at the site of invasion; the phosphatase acting on phosphotyrosine could serve as a regulator of cell differentiation during tumorigenesis. 相似文献
86.
Discerning the mechanisms responsible for membrane excitation and ionic control in Paramecium has been facilitated by the availability of genetic mutants that are defective in these pathways. Such mutants typically are selected on the basis of behavioral anomalies or resistance to ions. There have been few attempts to isolate ion-sensitive strains, despite the insights that might be gained from studies of their phenotypes. Here, we report isolation of "magbane," an ion-sensitive strain that is susceptible to Mg2+. Whereas the wild type tolerated the addition of > or =20 mm MgCl2 to the culture medium before growth was slowed and ultimately suppressed (at >40 mm), mgx mutation slowed growth at 10 mm. Genetic analysis indicated that the phenotype resulted from a recessive single-gene mutation that had not been described previously. We additionally noted that a mutant that was well described previously (restless) is also highly sensitive to Mg2+. This mutant is characterized by an inability to control membrane potential when extracellular K+ concentrations are lowered, due to inappropriate regulation of a Ca2+-dependent K+ current. However, comparing the mgx and rst mutant phenotypes suggested that two independent mechanisms might be responsible for their Mg2+ lethality. The possibility that mgx mutation may adversely affect a transporter that is required for maintaining low intracellular Mg2+ is considered. 相似文献
87.
Tian L Duncan RR Hammond MS Coghill LS Wen H Rusinova R Clark AG Levitan IB Shipston MJ 《The Journal of biological chemistry》2001,276(11):7717-7720
Alternative exon splicing and reversible protein phosphorylation of large conductance calcium-activated potassium (BK) channels represent fundamental control mechanisms for the regulation of cellular excitability. BK channels are encoded by a single gene that undergoes extensive, hormonally regulated exon splicing. In native tissues BK channels display considerable diversity and plasticity in their regulation by cAMP-dependent protein kinase (PKA). Differential regulation of alternatively spliced BK channels by PKA may provide a molecular basis for the diversity and plasticity of BK channel sensitivities to PKA. Here we demonstrate that PKA activates BK channels lacking splice inserts (ZERO) but inhibits channels expressing a 59-amino acid exon at splice site 2 (STREX-1). Channel activation is dependent upon a conserved C-terminal PKA consensus motif (S869), whereas inhibition is mediated via a STREX-1 exon-specific PKA consensus site. Thus, alternative splicing acts as a molecular switch to determine the sensitivity of potassium channels to protein phosphorylation. 相似文献
88.
Single-chain antibody displayed on a recombinant measles virus confers entry through the tumor-associated carcinoembryonic antigen 下载免费PDF全文
Hammond AL Plemper RK Zhang J Schneider U Russell SJ Cattaneo R 《Journal of virology》2001,75(5):2087-2096
To redirect the tropism of the vaccine strain of measles virus (MV), Edmonston B, to a targeted cell population, we displayed on the viral hemagglutinin (H) a single-chain antibody (scAb) specific for the tumor-associated carcinoembryonic antigen (CEA). We generated H fusion proteins with three forms of the scAb appended, differing in the lengths of the linkers separating the VH and VL domains and thus in the oligomerization states of the scAbs. All proteins were stable, appeared properly folded, and were transported to the cell surface, but only H displaying the long-linker form of scAb was functional in supporting cell-cell fusion. This protein induced extensive syncytia in cells expressing the normal virus receptor CD46 and also in CD46-negative cells expressing the targeted receptor, human CEA. Replication-competent MV with H replaced by H displaying the long-linker form of scAb was recovered and replicated efficiently in both CD46-positive and CD46-negative, CEA-positive cells. Thus, MV not only tolerates the addition of a scAb on its H protein but also infects cells via a novel interaction between the scAb and its targeted receptor. 相似文献
89.
Goulder PJ Addo MM Altfeld MA Rosenberg ES Tang Y Govender U Mngqundaniso N Annamalai K Vogel TU Hammond M Bunce M Coovadia HM Walker BD 《Journal of virology》2001,75(3):1339-1347
Human immunodeficiency virus (HIV)-specific cytotoxic T lymphocytes (CTL) play a major role in control of viral replication. To understand the contribution of this antiviral response, an initial step is to fully define the specific epitopes targeted by CTL. These studies focused on CTL responses restricted by HLA-A*3002, one of the HLA-A molecules most prominent in African populations. To avoid the time-consuming effort and expense involved in culturing CTL prior to defining epitopes and restricting alleles, we developed a method combining Elispot assays with intracellular gamma interferon staining of peripheral blood mononuclear cells to first map the optimal epitopes targeted and then define the HLA restriction of novel epitopes. In two A*3002-positive subjects whose CTL responses were characterized in detail, the strongest response in both cases was to an epitope in p17 Gag, RSLYNTVATLY (residues 76 to 86). Using this method, CTL epitopes for which there were no motif predictions were optimized and the HLA restriction was established within 48 to 72 h of receipt of blood. This simple and convenient approach should prove useful especially in the characterization of CTL responses specific to HIV and other viruses, particularly in localities where performing cytotoxicity assays would be problematic. 相似文献
90.