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181.
Color vision models: Some simulations,a general n‐dimensional model,and the colourvision R package 下载免费PDF全文
Felipe M. Gawryszewski 《Ecology and evolution》2018,8(16):8159-8170
The development of color vision models has allowed the appraisal of color vision independent of the human experience. These models are now widely used in ecology and evolution studies. However, in common scenarios of color measurement, color vision models may generate spurious results. Here I present a guide to color vision modeling (Chittka (1992, Journal of Comparative Physiology A, 170, 545) color hexagon, Endler & Mielke (2005, Journal Of The Linnean Society, 86, 405) model, and the linear and log‐linear receptor noise limited models (Vorobyev & Osorio 1998, Proceedings of the Royal Society B, 265, 351; Vorobyev et al. 1998, Journal of Comparative Physiology A, 183, 621)) using a series of simulations, present a unified framework that extends and generalize current models, and provide an R package to facilitate the use of color vision models. When the specific requirements of each model are met, between‐model results are qualitatively and quantitatively similar. However, under many common scenarios of color measurements, models may generate spurious values. For instance, models that log‐transform data and use relative photoreceptor outputs are prone to generate spurious outputs when the stimulus photon catch is smaller than the background photon catch; and models may generate unrealistic predictions when the background is chromatic (e.g. leaf reflectance) and the stimulus is an achromatic low reflectance spectrum. Nonetheless, despite differences, all three models are founded on a similar set of assumptions. Based on that, I provide a new formulation that accommodates and extends models to any number of photoreceptor types, offers flexibility to build user‐defined models, and allows users to easily adjust chromaticity diagram sizes to account for changes when using different number of photoreceptors. 相似文献
182.
Background and objective
One of the important applications of non-invasive respiration monitoring using ECG signal is the detection of obstructive sleep apnea (OSA). ECG-derived respiratory (EDR) signals, contribute to useful information about apnea occurrence. In this paper, two EDR extraction methods are proposed, and their application in automatic OSA detection using single-lead ECG is investigated.Methods
EDR signals are extracted based on new respiration-related features in ECG beats morphology, such as ECG variance () and phase space reconstruction area (). After evaluating the EDRs by comparing them to a reference respiratory signal, they are used in an automatic OSA detection application. Fantasia and Apnea-ECG database from PhysioNet are used for EDRs assessments and OSA detection, respectively. The final performance of our OSA detection is tested on an independent test data which is also compared with results of other techniques in the literature.Results
The extracted EDRs, and show correlations of 72% and 70% with reference respiration, which outperform the other state-of-the-art EDR methods. After feature extraction from EDRs and RR intervals series, the combination of RR and feature sets achieved 100% accuracy in subject-based apnea detection on independent test data, and also minute-based apnea detection is done with accuracy, sensitivity and specificity of 90.9%, 89.6% and 91.8%, which is better than other automatic algorithms in the literature.Conclusions
Our OSA detection system using EDRs features yields better independent test results compared with other state-of-the-art automatic apnea detection methods. The results indicate that ECG-based OSA detection system can classify OSA events with high accuracy and suggest a promising, non-invasive and efficient method for apnea detection. 相似文献183.
Neal R. Pellis Thomas J. Goodwin Diana Risin Bradley W. McIntyre Roland P. Pizzini David Cooper Tacey L. Baker Glenn F. Spaulding 《In vitro cellular & developmental biology. Animal》1997,33(5):398-405
Summary Immunity relies on the circulation of lymphocytes through many different tissues including blood vessels, lymphatic channels,
and lymphoid organs. The ability of lymphocytes to traverse the interstitium in both nonlymphoid and lymphoid tissues can
be determined in vitro by assaying their capacity to locomote through Type I collagen. In an attempt to characterize potential causes of microgravity-induced
immunosuppression, we investigated the effects of simulated microgravity on human lymphocyte function in vitro using a specialized rotating-wall vessel culture system developed at the Johnson Space Center. This very low shear culture
system randomizes gravitational vectors and provides an in vitro approximation of microgravity. In the randomized gravity of the rotating-wall vessel culture system, peripheral blood lymphocytes
did not locomote through Type I collagen, whereas static cultures supported normal movement. Although cells remained viable
during the entire culture period, peripheral blood lymphocytes transferred to unit gravity (static culture) after 6 h in the
rotating-wall vessel culture system were slow to recover and locomote into collagen matrix. After 72 h in the rotating-wall
vessel culture system and an additional 72 h in static culture, peripheral blood lymphocytes did not recover their ability
to locomote. Loss of locomotory activity in rotating-wall vessel cultures appears to be related to changes in the activation
state of the lymphocytes and the expression of adhesion molecules. Culture in the rotating-wall vessel system blunted the
ability of peripheral blood lymphocytes to respond to polyclonal activation with phytohemagglutinin. Locomotory response remained
intact when peripheral blood lymphocytes were activated by anti-CD3 antibody and interleukin-2 prior to introduction into
the rotating-wall vessel culture system. Thus, in addition to the systemic stress factors that may affect immunity, isolated
lymphocytes respond to gravitational changes by ceasing locomotion through model interstitium. These in vitro investigations suggest that microgravity induces non-stress-related changes in cell function that may be critical to immunity.
Preliminary analysis of locomotion in true microgravity revealed a substantial inhibition of cellular movement in Type I collagen.
Thus, the rotating-wall vessel culture system provides a model for analyzing the microgravity-induced inhibition of lymphocyte
locomotion and the investigation of the mechanisms related to lymphocyte movement. 相似文献
184.
Predicting the impacts of climate change on the distribution of species: are bioclimate envelope models useful? 总被引:12,自引:1,他引:12
Modelling strategies for predicting the potential impacts of climate change on the natural distribution of species have often focused on the characterization of a species’ bioclimate envelope. A number of recent critiques have questioned the validity of this approach by pointing to the many factors other than climate that play an important part in determining species distributions and the dynamics of distribution changes. Such factors include biotic interactions, evolutionary change and dispersal ability. This paper reviews and evaluates criticisms of bioclimate envelope models and discusses the implications of these criticisms for the different modelling strategies employed. It is proposed that, although the complexity of the natural system presents fundamental limits to predictive modelling, the bioclimate envelope approach can provide a useful first approximation as to the potentially dramatic impact of climate change on biodiversity. However, it is stressed that the spatial scale at which these models are applied is of fundamental importance, and that model results should not be interpreted without due consideration of the limitations involved. A hierarchical modelling framework is proposed through which some of these limitations can be addressed within a broader, scale‐dependent context. 相似文献
185.
【目的】通过菌落测试片提取菌落并计数,在农业、食品业、医疗卫生等领域中是一项常用且重要的工作。目前,菌落自动计数算法大都是以菌落培养皿为主要工作对象,对菌落测试片适用性较差。另外,目前相关技术在常规的粘连物体分割中有着较好的效果,但在菌落分割计数中,由于菌落本身的形态特征,对粘连菌落分割计数的效果尚不够精准。【方法】为解决此类问题,本文提出一种基于目标颜色基及梯度方向匹配的菌落分割计数算法。首先利用图像中菌落的颜色特征作为基,将图像转换到基空间内,以增强菌落与背景之间的差异,其次利用菌落图像的梯度幅值特征对梯度方向进行滤波,然后通过梯度方向进行匹配,进而将粘连的菌落分割,最后利用非极大值抑制的方法筛选出菌落并计数。【结果】经试验,本研究算法的计数精度可达98.00%,能够满足实际需求。【结论】在针对菌落的目标分割计数中,本研究算法不仅计数精度高,而且具有较好的鲁棒性,在对不同厂家的菌落总数测试片菌落分割计数中均有优异效果;然而在对大面积目标的检测分割中算法的准确率会有所下降,因此,该算法更适合于菌落等小目标的检测分割。 相似文献
186.
187.
2010年3—10月,沿城市发展梯度选取了合肥市3个区域(城市、城郊和农村),进行蝴蝶调查。共采集蝴蝶1484只,隶属7科28属34种。结果表明:研究区域优势种蝶类为菜粉蝶(Pieris rapae)、酢浆灰蝶(Pseudozizeeria maha)、黄钩蛱蝶(Polygonia c-aureum);合肥不同城市化区域蝶类多样性存在差异,其多样性指数变化趋势为农村城郊城市;农村和城郊的多样性指数和丰富度指数在7月最高,城市8月最高;城市和城郊的优势度指数在8月最高,农村7月最高;3种不同城市化区域的均匀度指数均是8月最高。在快速城市化过程中,应根据不同城市化水平、不同生境类型采取不同的措施,保护和促进城市生物多样性。 相似文献
188.
Ana I. Soriano Dolors Vinyoles Carmen Maté 《Journal of applied animal welfare science : JAAWS》2016,19(1):49-61
The evaluation of enrichment programs is important to determine their effect on nonhuman animal welfare. The daily activity pattern and use of space of 3 brown bears (Ursus arctos) were used for long-term macroevaluation of enrichment to compare the baseline and enrichment phases. Focal sampling methods were used for data collection, and instantaneous scans were made at 2-min intervals during 15 sessions of 1 hr for each animal during the 2 study periods. The enrichment devices were categorized as feeding, occupational, and sensorial. The long-term macroevaluation in 3 bears showed statistically significant differences in some types of activity but not in others. There were also statistically significant differences for the use of space in 4 of the 8 zones in which the enclosures were divided. A more homogenous pattern in the use of space was only observed during the enrichment phase in the old female. The 3 brown bears followed different patterns concerning the enrichment program. 相似文献
189.
Red deer females collect on male clumps at mating areas 总被引:4,自引:1,他引:3
Mating strategies in mammalian herbivores are adapted to thedispersion of
females, and female dispersion is mainly determinedby resource dispersion,
although it is frequently unclear whetherfemales may also be influenced by
the location of males. Inthe red deer (Cervus elaphus) the
distribution of females beforethe rut predicts the places were males should
establish territoriesand even their relative success. However, the number of
femalesusing the mating areas in Doñana
increases during therut. We observed 20 areas of meadows, used by grazing
femalesbefore the rut. At the onset of the rut, the number of females
increasedin some of these areas and decreased in others, and the opposite
patternwas found after the rutting period. Changes in the vegetationat
mating and nonmating areas could not account for the changesin female
distribution; even some of the highest quality meadowswere vacated by females
during rut. In selecting the matingareas, females avoided isolated small
meadows within the scrubarea and preferred larger meadows where a number of
neighboringrutting males could be found. Females also avoided those areas
heavilyused by fallow deer (Dama dama), a competing sympatric
species.We found that females suffered less sexual harassment when inlarger
harems and when their harem was surrounded by other harems.Our results,
together with those in the literature about thispopulation, indicate that red
deer females collect during theearly rut in mating areas containing several
rutting males,although once there they may select particular sites based on
availabilityof food rather than based on the presence of a particular male.
Byjoining harems in large meadows they are less harassed, andat the same
time they probably increase their chances of matingwith highly competitive
males. The results from Doñanasupport the
idea that harassment avoidance may lead to femalemovements to areas with male
territories without lek breedingor female comparison of male phenotypes and
may bring an insightinto those factors leading to clumps of male territories
andleks. 相似文献
190.
It is hard to construct theories for the folding of globular proteins because they are large and complicated molecules having enormous numbers of nonnative conformations and having native states that are complicated to describe. Statistical mechanical theories of protein folding are constructed around major simplifying assumptions about the energy as a function of conformation and/or simplifications of the representation of the polypeptide chain, such as one point per residue on a cubic lattice. It is not clear how the results of these theories are affected by their various simplifications. Here we take a very different simplification approach where the chain is accurately represented and the energy of each conformation is calculated by a not unreasonable empirical function. However, the set of amino acid sequences and allowed conformations is so restricted that it becomes computationally feasible to examine them all. Hence we are able to calculate melting curves for thermal denaturation as well as the detailed kinetic pathway of refolding. Such calculations are based on a novel representation of the conformations as points in an abstract 12-dimensional Euclidean conformation space. Fast folding sequences have relatively high melting temperatures, native structures with relatively low energies, small kinetic barriers between local minima, and relatively many conformations in the global energy minimum's watershed. In contrast to other folding theories, these models show no necessary relationship between fast folding and an overall funnel shape to the energy surface, or a large energy gap between the native and the lowest nonnative structure, or the depth of the native energy minimum compared to the roughness of the energy landscape. Proteins 32:425–437, 1998. © 1998 Wiley-Liss, Inc. 相似文献