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By treating the nonlinear model as if it were linear in the parameterization θ in the neighbourhood of the least squares estimate θ, we construct two-sided nominally-q-prediction intervals by applying the usual linear model theory. The derivation of the truncated series expansion of the expected coverage of the prediction intervals at a feasible value of the parameter vector is described. The quadratic approximation of the expected coverage is then obtained for a two-parameter nonlinear model. Finally we show how we may construct the prediction intervals when a certain type of nonlinear transformation of the parameter vector has been applied.  相似文献   
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Hybridization of natural products has high potential to further improve their activities and may produce synergistic effects between linked pharmacophores. Here we report synthesis of nine new hybrids of natural products egonol, homoegonol, thymoquinone and artemisinin and evaluation of their activities against P. falciparum 3D7 parasites, human cytomegalovirus, sensitive and multidrug-resistant human leukemia cells. Most of the new hybrids exceed their parent compounds in antimalarial, antiviral and antileukemia activities and in some cases show higher in vitro efficacy than clinically used reference drugs chloroquine, ganciclovir and doxorubicin. Combined, our findings stress the high potency of these hybrids and encourages further use of the hybridization concept in applied pharmacological research.  相似文献   
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Use of single-sample genetic methods to estimate effective population size has skyrocketed in recent years. Although the underlying models assume discrete generations, they are widely applied to age-structured species. We simulated genetic data for 21 iteroparous animal and plant species to evaluate two untested hypotheses regarding performance of the single-sample method based on linkage disequilibrium (LD): (1) estimates based on single-cohort samples reflect the effective number of breeders in one reproductive cycle (Nb), and (2) mixed-age samples reflect the effective size per generation (Ne). We calculated true Ne and Nb, using the model species’ vital rates, and verified these with individual-based simulations. We show that single-cohort samples should be equally influenced by Nb and Ne and confirm this with simulated results: N^b was a linear (r2 = 0.98) function of the harmonic mean of Ne and Nb. We provide a quantitative bias correction for raw N^b based on the ratio Nb/Ne, which can be estimated from two or three simple life history traits. Bias-adjusted estimates were within 5% of true Nb for all 21 study species and proved robust when challenged with new data. Mixed-age adult samples produced downwardly biased estimates in all species, which we attribute to a two-locus Wahlund effect (mixture LD) caused by combining parents from different cohorts in a single sample. Results from this study will facilitate interpretation of rapidly accumulating genetic estimates in terms of both Ne (which influences long-term evolutionary processes) and Nb (which is more important for understanding eco-evolutionary dynamics and mating systems).  相似文献   
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Summary Genetic variation in an isolated northern metapopulation of the pool frog (Rana lessonae) in Sweden was compared to that of Central European populations using enzyme electrophoresis and literature data. Of the 31 loci scored, two (EST-2 andIDH-2) were polymorphic while no variation occurred in seven of the eight loci which are polymorphic in Central European populations.The heterozygosity level of the Swedish pool frogs is very low compared to that of other anuran populations, but their mean proportion of fertilized eggs within egg masses (97.5%) was not lower than in more heterozygous species, and their body size-specific fecundity did not differ from that of Polish conspecifics. The low genetic variability of the Swedish pool frogs is discussed in relation to features of the local populations such as size (N), calculated effective size (N e ) reproductive success and probable history. It is concluded that long-term strong fluctuations in population size caused by reporductive failure in cold years have contributed more to the low genetic variability than could a single founder event due to a recent introduction by man.  相似文献   
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基于TM NDVI的武功山山地草甸植被覆盖度时空变化研究   总被引:2,自引:0,他引:2  
以江西省武功山山地草甸为研究区,基于4期TM(Thematic Mapper,专题测图仪)卫星遥感影像,提取NDVI(Normalized Difference Vegetation Index,归一化植被指数),采用像元二分模型,运用ENVI 5.1和Arc GIS 10.0软件计算得到武功山山地草甸的植被覆盖度分布格局及动态变化。研究结果表明:(1)研究期间山地草甸面积减少了9.72%,呈递减趋势。20年来随着武功山风景区成立—旅游业发展—山地草甸生态修复,山地草甸植被覆盖度增加和减少交替,总体呈上升趋势;(2)山地草甸植被覆盖度呈现东南高西北低的空间分布特征。低覆盖度草甸区集中在武功山山脉的西北侧坡面的崖壁和部分山脊线上,而高覆盖度草甸区多分布在武功山山脉的东南坡面;(3)研究区山地草甸退化与改善并存,山地草甸最北端和白鹤峰-九龙山区域的东南坡、南坡低海拔处植被总体呈退化特征;发云界南部的东坡植被总体呈现改善特征。研究期间山地草甸退化面积比改善面积多出1.78%。(4)山地草甸植被覆盖度的分布格局和地形因子存在较高的相关性(P0.05):植被覆盖度随着坡向的变化而呈规律性的变化,总体上山地草甸植被覆盖度的分布为阳坡平坡阴坡;植被覆盖度先是随着坡度的上升而升高,在坡度15°—25°时达到峰值,然后随坡度的上升而下降,在45°—90°最低;植被覆盖度随海拔升高呈波浪式下降,1000—1200m最高,在主峰山顶海拔1800—1918.3m最低。遥感解译检验结果证明采用此方法对大面积山地草甸覆盖度分布及变化进行反演可行而准确;在后续研究中将采用不同季相的多期影像数据提取NDVI对研究区植被覆盖度进行长期监测,以便更准确可靠地分析山地草甸演化过程和趋势。  相似文献   
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Growth in the pharmaceutical industry has led to an increasing demand for rapid characterization of therapeutic monoclonal antibodies. The current methods for antibody sequence confirmation (e.g., N-terminal Edman sequencing and traditional peptide mapping methods) are not sufficient; thus, we developed a fast method for sequencing recombinant monoclonal antibodies using a novel digestion-on-emitter technology. Using this method, a monoclonal antibody can be denatured, reduced, digested, and sequenced in less than an hour. High throughput and satisfactory protein sequence coverage were achieved by using a non-specific protease from Aspergillus saitoi, protease XIII, to digest the denatured and reduced monoclonal antibody on an electrospray emitter, while electrospray high voltage was applied to the digestion mixture through the emitter. Tandem mass spectrometry data was acquired over the course of enzyme digestion, generating similar information compared to standard peptide mapping experiments in much less time. We demonstrated that this fast protein sequencing method provided sufficient sequence information for bovine serum albumin and two commercially available monoclonal antibodies, mouse IgG1 MOPC21 and humanized IgG1 NISTmAb. For two monoclonal antibodies, we obtained sequence coverage of 90.5–95.1% for the heavy chains and 98.6–99.1% for the light chains. We found that on-emitter digestion by protease XIII generated peptides of various lengths during the digestion process, which was critical for achieving sufficient sequence coverage. Moreover, we discovered that the enzyme-to-substrate ratio was an important parameter that affects protein sequence coverage. Due to its highly automatable and efficient design, our method offers a major advantage over N-terminal Edman sequencing and traditional peptide mapping methods in the identification of protein sequence, and is capable of meeting an ever-increasing demand for monoclonal antibody sequence confirmation in the biopharmaceutical industry.  相似文献   
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Butana and Kenana breeds from Sudan are part of the East African zebu Bos indicus type of cattle. Unlike other indigenous zebu cattle in Africa, they are unique due to their reputation for high milk production and are regarded as dairy cattle, the only ones of their kind on the African continent. In this study, we sequenced the complete mitochondrial DNA (mtDNA) D‐loop of 70 animals to understand the maternal genetic variation, demographic profiles and history of the two breeds in relation to the history of cattle pastoralism on the African continent. Only taurine mtDNA sequences were identified. We found very high mtDNA diversity but low level of maternal genetic structure within and between the two breeds. Bayesian coalescent‐based analysis revealed different historical and demographic profiles for the two breeds, with an earlier population expansion in the Butana vis a vis the Kenana. The maternal ancestral populations of the two breeds may have diverged prior to their introduction into the African continent, with first the arrival of the ancestral Butana population. We also reveal distinct demographic history between the two breeds with the Butana showing a decline in its effective population size (Ne) in the recent past ~590 years. Our results provide new insights on the early history of cattle pastoralism in Sudan indicative of a large ancient effective population size.  相似文献   
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专属引种植物的物候及生长研究能够掌握特定物候相在专属水平上的阈值,并为评估引种专属的适应潜力提供参考。通过对中国科学院植物研究所北京植物园内引种多年的9种荚蒾(Viburnum)的花期及2种荚蒾的生长动态进行观测,分析讨论了花期对冬春两季异常低温的响应及营养与生殖生长的关联机制。结果表明:2009–2010年冬春异常低温后,荚蒾始花期的整体延迟是由春季环境热量供应不及时所致,种间延迟程度的差异则与原产地的气候有紧密联系:分布于寒温带地区的欧洲绣球(V.opulus)和修枝荚蒾(V.burejaeticum)延迟天数最少(分别为10和12天),分布于我国亚热带的琼花(V.macrocephalum)和桦叶荚蒾(V.betulifolium)延迟天数最多(分别为21和26天)。荚蒾花前有效积温介于39–368°C之间。经历异常低温后,花前有效积温呈上升和下降两种格局,与物种冷量和热量的内在需求有关。荚蒾属植物的生殖与营养生长呈现两种关联方式,早花种类开花座果伴随着营养生长的竞争,晚花种类花后即出现营养生长的支持,对果实发育的保障性较强。  相似文献   
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