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931.
The soybean aphid is an invasive pest in the midwest United States, with frequent population outbreaks. Previous work has shown that aphid population densities are higher on potassium-deficient soybean than on healthy soybean. The experiments reported here test the hypotheses that the potassium nutrition of the host plant affects the forms of phloem nitrogen available to soybean aphids, and subsequently, their abundance. In field surveys and an exclusion cage study when aphid populations were high, soybean plants with potassium deficiency symptoms had a higher density of soybean aphids than plants without deficiency symptoms. In clip cage experiments, this effect was caused by earlier aphid reproduction and higher numbers of aphid nymphs per mother on plants growing in lower-potassium soil. In phloem exudation samples, the percentage of asparagine, an important amino acid for aphid nutrition, increased with decreasing soil potassium, perhaps because of potassium's role in the nitrogen use of the plant. Taken together, these results show that soybean potassium deficiency can lead to higher populations of soybean aphid through a bottom-up effect. A possible mechanism for this relationship is that soybean potassium deficiency improves the nitrogen nutrition of these N-limited insects. By releasing these herbivores from N limitation, host plant potassium deficiency may allow soybean aphid populations to reach higher levels more rapidly in the field. 相似文献
932.
Obara MT da Rosa JA Ceretti W Urbinatti PR Quintero LO Barata JM Galvão C Jurberg J 《Memórias do Instituto Oswaldo Cruz》2007,102(4):463-468
The aim of this study was to analyze the external morphology of the scutellum through optical microscopy and scanning electron microscopy (SEM) in male specimens of Triatoma costalimai, T. delpontei, T. eratyrusiformis, T. matogrossensis, T. infestans melanosoma, T. sherlocki, T. tibiamaculata, and T. vandae. A total of 30 photographs of the scutellum were made. Magnification varied from 50X to 750X. Regarding depth and forms of the central depression, the heart-shaped form was predominant, with some exceptions, so that this shape appears to be a common characteristic for species of genus Triatoma Laporte, 1832. In T. eratyrusiformis, a kind of sensillum with important taxonomic value was observed. The different sizes and shapes of the designs found on the posterior process of the scutellum were also of important taxonomic interest. The study of the scutellum based on SEM showed valuable characteristics, allowing the use of this structure to aid the diagnosis of triatomine species. Thus, more specimens in subsequent studies and analyses of morphometric parameters should contribute to agreement on phylogenetic aspects in this genus. A Key to eight species of Triatoma based on male scutellar morphology is presented. 相似文献
933.
We recently performed a molecular epidemiology survey of human immunodeficiency virus type 1 (HIV-1) infection in Miracema, a small city in Southeast Brazil, and found multiple monophyletic clusters, consistent with independent introductions and spread of different viral lineages in the city. Here we apply Bayesian coalescent-based methods to the two largest subtype B clusters and estimate that the most recent common ancestors that gave rise to these two transmission chains were in circulation around 1991-1992. The finding that HIV-1 spread in this Brazilian small city was already taking place at a time Aids was considered a problem restricted to large urban centers may have important public health implications. 相似文献
934.
As part of an ongoing study on the features of AIDS spread towards small cities and rural areas, we present a molecular survey of human immunodeficiency virus type 1 (HIV-1) polymerase sequences recovered between 2004 and 2006 from 71 patients receiving care in the city of Saquarema, inner state of Rio de Janeiro. Phylogenetic reconstructions found the two prevalent lineages in the state (subtypes B [59 strains, 83.1%], F1 [6 strains; 8.4%], and BF1 recombinants [four strains; 5.6%]), as well as two (2.8%) CRF02_AG strains, which seems to be an emerging lineage in the capital. These CRF02_AG sequences were recovered from a married heterosexual couple who never traveled abroad, thus providing the first molecular evidence of autochthonous horizontal transmission of this lineage of major global importance. Also, three phylogenetic clusters of strains recovered from a total of 18.3% of the cohort were uncovered. Their close genetic relatedness suggests they were recovered from patients who probably took part in the same chain of viral spread. In conjunction with our previous surveys from inner Rio de Janeiro, these results suggest that although small cities harbor unique molecular features of HIV-1 infection, they also clearly reflect and may rapidly absorb the diversity recorded in large urban centers. 相似文献
935.
Radice F Orlandi V Massa V Battini V Bertoni G Reineke W Barbieri P 《Applied microbiology and biotechnology》2007,75(5):1111-1118
An Arthrobacter strain, able to utilize 4-chlorobenzoic acid as the sole carbon and energy source, was isolated and characterized. The first step of the catabolic pathway was found to proceed via a hydrolytic dehalogenation that leads to the formation of 4-hydroxybenzoic acid. The dehalogenase encoding genes (fcb) were sequenced and found highly homologous to and organized as those of other 4-chlorobenzoic acid degrading Arthrobacter strains. The fcb genes were cloned and successfully expressed in the heterologous host Pseudomonas putida PaW340 and P. putida KT2442 upper TOL, which acquired the ability to grow on 4-chlorobenzoic acid and 4-chlorotoluene, respectively. The cloned dehalogenase displayed a high specificity for para-substituted haloaromatics with affinity Cl > Br > I > F, in the order. 相似文献
936.
Analysis of actin remodeling in live cells and tissues has become an increasingly important tool to study actin-dependent cellular processes. To facilitate these experiments in the mouse we have generated a GFP-actin-expressing line (huGE) by knock-in of the GFP-actin gene into the profilin 1 locus. Here we show that GFP-actin is expressed throughout embryonic development and in all tissues except skeletal muscle, in a pattern similar to profilin 1. Particularly high expression of GFP-actin was observed in bone marrow and all blood cells. The GFP-actin fusion protein is functional as shown by its co-localization with endogenous actin in F-actin-rich structures. Therefore, the huGE mouse line provides a novel tool to monitor actin dynamics in mouse embryos and a wide range of organs. 相似文献
937.
Müller H Schweitzer N Jöhren O Dominiak P Raasch W 《American journal of physiology. Endocrinology and metabolism》2007,293(3):E802-E810
The HPA axis is hyperactive under conditions of leptin and insulin resistance as well as after ANG II administration. We hypothesized that a hyperreactivity of the HPA axis to ANG contributes to an impaired glucose utilization in obesity, since leptin resistance and an overactive renin-angiotensin-aldosterone system are features of obesity. Zucker rats were treated with ANG via subcutaneous minipumps (0, 0.9, and 9.0 mug/h; 4 wk). PA axis reactivity and glucose homeostasis were characterized after CRH treatment and during an oral glucose tolerance test (OGTT). The elevated plasma profile of corticosterone after CRH stimulation in saline-treated OZR compared with LZR confirmed that the sensitization of the PA axis depended on leptin resistance. Irrespective of the rat strain, circulating ANG levels and blood pressure were selectively increased after administration of 9 mug/h ANG (high ANG). Only high ANG induced an elevation of the corticosterone and glucose response after CRH stimulation in OZR but did not affect the ACTH secretion. During OGTT, corticosterone and consequently glucose increased in OZR after high ANG, whereas the insulin secretion was decreased. In the adrenal glands of OZR, AT(1A) receptor mRNA levels increased after high ANG. We conclude that the impairment of glucose utilization after ANG stimulation is potentiated in leptin-resistant rats as a result of a hyperreactive PA axis, thereby confirming the functional importance of a dysregulation within the HPA axis in metabolic syndrome or obesity. The ACTH-independent stimulation of corticosterone release and the selective increase of AT(1A) receptor mRNA in the adrenals of OZR indicated a sensitization of adrenals toward ANG, causing a stimulation of the PA axis. 相似文献
938.
939.
The heat shock protein HSP70 promotes mouse NK cell activity against tumors that express inducible NKG2D ligands 总被引:4,自引:0,他引:4
Elsner L Muppala V Gehrmann M Lozano J Malzahn D Bickeböller H Brunner E Zientkowska M Herrmann T Walter L Alves F Multhoff G Dressel R 《Journal of immunology (Baltimore, Md. : 1950)》2007,179(8):5523-5533
The stress-inducible heat shock protein (HSP) 70 is known to function as an endogenous danger signal that can increase the immunogenicity of tumors and induce CTL responses. We show in this study that HSP70 also activates mouse NK cells that recognize stress-inducible NKG2D ligands on tumor cells. Tumor size and the rate of metastases derived from HSP70-overexpressing human melanoma cells were found to be reduced in T and B cell-deficient SCID mice, but not in SCID/beige mice that lack additionally functional NK cells. In the SCID mice with HSP70-overexpressing tumors, NK cells were activated so that they killed ex vivo tumor cells that expressed NKG2D ligands. In the tumors, the MHC class I chain-related (MIC) A and B molecules were found to be expressed. Interestingly, a counter selection was observed against the expression of MICA/B in HSP70-overexpressing tumors compared with control tumors in SCID, but not in SCID/beige mice, suggesting a functional relevance of MICA/B expression. The melanoma cells were found to release exosomes. HSP70-positive exosomes from the HSP70-overexpressing cells, in contrast to HSP70-negative exosomes from the control cells, were able to activate mouse NK cells in vitro to kill YAC-1 cells, which express NKG2D ligands constitutively, or the human melanoma cells, in which MICA/B expression was induced. Thus, HSP70 and inducible NKG2D ligands synergistically promote the activation of mouse NK cells resulting in a reduced tumor growth and suppression of metastatic disease. 相似文献
940.
Genetic engineering of the major timothy grass pollen allergen, Phl p 6, to reduce allergenic activity and preserve immunogenicity 总被引:1,自引:0,他引:1
Vrtala S Focke M Kopec J Verdino P Hartl A Sperr WR Fedorov AA Ball T Almo S Valent P Thalhamer J Keller W Valenta R 《Journal of immunology (Baltimore, Md. : 1950)》2007,179(3):1730-1739
On the basis of IgE epitope mapping data, we have produced three allergen fragments comprising aa 1-33, 1-57, and 31-110 of the major timothy grass pollen allergen Phl p 6 aa 1-110 by expression in Escherichia coli and chemical synthesis. Circular dichroism analysis showed that the purified fragments lack the typical alpha-helical fold of the complete allergen. Superposition of the sequences of the fragments onto the three-dimensional allergen structure indicated that the removal of only one of the four helices had led to the destabilization of the alpha helical structure of Phl p 6. The lack of structural fold was accompanied by a strong reduction of IgE reactivity and allergenic activity of the three fragments as determined by basophil histamine release in allergic patients. Each of the three Phl p 6 fragments adsorbed to CFA induced Phl p 6-specific IgG Abs in rabbits. However, immunization of mice with fragments adsorbed to an adjuvant allowed for human use (AluGel-S) showed that only the Phl p 6 aa 31-110 induced Phl p 6-specific IgG Abs. Anti-Phl p 6 IgG Abs induced by vaccination with Phl p 6 aa 31-110 inhibited patients' IgE reactivity to the wild-type allergen as well as Phl p 6-induced basophil degranulation. Our results are of importance for the design of hypoallergenic allergy vaccines. They show that it has to be demonstrated that the hypoallergenic derivative induces a robust IgG response in a formulation that can be used in allergic patients. 相似文献