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121.
The peak interval (PI) procedure is commonly used to evaluate animals' ability to produce timed intervals. It consists of presenting fixed interval (FI) schedules in which some of the trials are replaced by extended non-reinforced trials. Responding will often resume (resurge) at the end of the non-reinforced trials unless precautions are taken to prevent it. Response resurgence was replicated in rats and pigeons. Variation of the durations of the FI and the non-reinforced probe trials showed it to be dependent on the time when reinforcement is expected. Timing of both the normal time to reinforcement, and the subsequent time to reinforcement during the probe trials followed Weber's law. A quantitative model of resurgence is described, suggesting how animals respond to the signaling properties of reinforcement omission. Model results were simulated using a stochastic binary counter. 相似文献
122.
Juvenile reef fish communities represent an essential component of coral reef ecosystems in the current focus of fish population
dynamics and coral reef resilience. Juvenile fish survival depends on habitat characteristics and is, following settlement,
the first determinant of the number of individuals within adult populations. The goal of this study was to provide methods
for mapping juvenile fish species richness and abundance into spatial domains suitable for micro and meso-scale analysis and
management decisions. Generalized Linear Models predicting juvenile fish species richness and abundance were developed according
to spatial and temporal environmental variables measured from 10 m up to 10 km in the southwest lagoon of New Caledonia. The
statistical model was further spatially generalized using a 1.5-m resolution, independently created, remotely sensed, habitat
map. This procedure revealed that : (1) spatial factors at 10 to 100-m scale explained up to 71% of variability in juvenile
species richness, (2) a small improvement (75%) was gained when a combination of environmental variables at different spatial
and temporal scales was used and (3) the coupling of remotely sensed data, geographical information system tools and point-based
ecological data showed that the highest species richness and abundance were predicted along a narrow margin overlapping the
coral reef flat and adjacent seagrass beds. Spatially explicit models of species distribution may be relevant for the management
of reef communities when strong relationships exist between faunistic and environmental variables and when models are built
at appropriate scales. 相似文献
123.
John L. Lewin David E. Heppner Christopher J. Cramer 《Journal of biological inorganic chemistry》2007,12(8):1221-1234
The bis(μ-oxo)/μ-η2:η2-peroxo equilibria for seven supported Cu2O2 cores were studied with different hybrid and nonhybrid density functional theory models, namely, BLYP, mPWPW, TPSS, TPSSh,
B3LYP, mPW1PW, and MPW1K. Supporting ligands 3,3′-iminobis(N,N-dimethylpropylamine), N,N,N′,N′,N″-pentamethyldipropylenetriamine, N-[2-(pyridin-2-yl)ethyl]-N,N,N′-trimethylpropane-1,3-diamine, bis[2-(2-pyridin-2-yl)ethyl]methylamine, bis[2-(4-methoxy-2-pyridin-2-yl)ethyl]methylamine,
bis[2-(4-N,N-dimethylamino-2-pyridin-2-yl)ethyl]methylamine, and 1,4,7-triisopropyl-1,4,7-triazacyclononane were chosen on the basis of
the availability of experimental data for comparison. Density functionals were examined with respect to their ability accurately
to reproduce experimental properties, including, in particular, geometries and relative energies for the bis(μ-oxo) and side-on
peroxo forms. While geometries from both hybrid and nonhybrid functionals were in good agreement with experiment, the incorporation
of Hartree–Fock (HF) exchange in hybrid density functionals was found to have a large, degrading effect on predicted relative
isomer energies. Specifically, hybrid functionals predicted the μ-η2:η2-peroxo isomer to be too stable by roughly 5–10 kcal mol−1 for each 10% of HF exchange incorporated into the model. Continuum solvation calculations predict electrostatic effects to
favor bis(μ-oxo) isomers by 1–4 kcal mol−1 depending on ligand size, with larger ligands having smaller differential solvation effects. Analysis of computed molecular
partition functions suggests that nonzero measured entropies of isomerization are likely to be primarily associated with interactions
between molecular solutes and their first solvation shell.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
124.
The generality of habitat suitability models: A practical test with two insect groups 总被引:1,自引:0,他引:1
Silke Hein Birgit Binzenhfer Hans-Joachim Poethke Robert Biedermann Josef Settele Boris Schrder 《Basic and Applied Ecology》2007,8(4):310-320
For the design and declaration of conservation areas as well as for planning habitat management it is important to quantitatively know the habitat preferences of the focal species. To take into account the requirements of as many species as possible, it would be of great advantage if one would either (i) find one or several species whose habitat requirements cover those of a large number of other species or if one could (ii) identify a common set of habitat parameters that is important for the occurrence of many species. Ideally such common habitat parameters should be easy to measure. Only then they may be of practical value in applied conservation biology.In this study, we compared the habitat preferences of different insect species (grasshoppers, bush crickets, butterflies, moths) in the same region by applying identical methods. To identify common explanatory variables that predict the occurrence probability of these species, we first tested the transferability of the specific ‘species models’ to other species within the same insect group. We tested how well the incidence of one species can be predicted by the occurrence probability of another species. The ‘best’ models within each group were then tested for transferability between the different groups. Additionally, we tested the predictive power of the predictor variable ‘habitat type’ as an easy and often available measure for conservation practice.Although in the different ‘species models’ different key factors determine habitat suitability, some models were successfully transferred and were able to reasonably predict the distribution of other species. The habitat preferences of the burnet moth Zygaena carniolica were particularly well suited for the prediction of suitable habitats for all other species. In addition, the predictor variable ‘habitat type’ played a dominant role in all models. Models using this aggregated predictor variable may well predict suitable habitat for all species. 相似文献
125.
Median estimation of chemical constituents for sampling on two occasions under a log‐normal model 下载免费PDF全文
Athanassios Kondylis 《Biometrical journal. Biometrische Zeitschrift》2015,57(5):914-929
Sampling from a finite population on multiple occasions introduces dependencies between the successive samples when overlap is designed. Such sampling designs lead to efficient statistical estimates, while they allow estimating changes over time for the targeted outcomes. This makes them very popular in real‐world statistical practice. Sampling with partial replacement can also be very efficient in biological and environmental studies where estimation of toxicants and its trends over time is the main interest. Sampling with partial replacement is designed here on two occasions in order to estimate the median concentration of chemical constituents quantified by means of liquid chromatography coupled with tandem mass spectrometry. Such data represent relative peak areas resulting from the chromatographic analysis. They are therefore positive‐valued and skewed data, and are commonly fitted very well by the log‐normal model. A log‐normal model is assumed here for chemical constituents quantified in mainstream cigarette smoke in a real case study. Combining design‐based and model‐based approaches for statistical inference, we seek for the median estimation of chemical constituents by sampling with partial replacement on two time occasions. We also discuss the limitations of extending the proposed approach to other skewed population models. The latter is investigated by means of a Monte Carlo simulation study. 相似文献
126.
127.
Substrate removal mechanism in aerobic activated sludge processes was lately modeled using the simultaneous storage and growth (SSAG) phenomenon. The SSAG model was further refined with titrimetric components and successfully calibrated using both respirometric and titrimetric measurements for common substrate acetate. However, the improved SSAG model calibration was not verified with other organic substrates. Furthermore, very few studies are available in the literature on surfactant bio-kinetics, which generally use off-line experimental measurements with limited model-based interpretation. Therefore, the aim of this paper is to demonstrate its applicability for surfactant biodegradation using on-line measurements. Batch experiments were conducted using sodium dodecyl sulfate (SDS) as a test surfactant. Model calibration was done successfully for three different SDS concentrations using respirometric, titrimetric and combined respirometric-titrimetric measurement approaches. The parameter estimation results from all three stated combinations were statistically evaluated and found to be very close validating the model. 相似文献
128.
The high similarity between pigs and humans makes pigs a good gastrointestinal (GI) model for humans. Recently an epithelial cell line originating from the jejunum of pig (IPEC-J2) became available. Once validated, this model can be used to investigate the complex interactions occurring in the intestine. The advantages of using IPEC-J2 as in vitro model of the GI tract are the high resemblance between humans and pigs, and the ease of extrapolating in vitro to in vivo characteristics. In this study, the IPEC-J2 cells were functionally characterized by measuring the trans-epithelial electrical resistance (TEER), and by histological and ultrastructural studies. IPEC-J2 cells grown on six different permeable support systems, were investigated. The Transwell®-COL collagen-coated membrane (1.12 cm2) showed the best results concerning time efficiency and TEER values. The optimum seeding density of 12 × 105 cells/mL ensured that after 9 days of differentiation a confluent monolayer was formed. The decrease in TEER values after a maximum had been reached, coincided with the ultrastructural development of apical microvilli. We conclude that IPEC-J2 cells grown on collagen-coated membranes represent a valuable in vitro model system for the small intestinal epithelium which can be of great interest for intestinal research. 相似文献
129.
目的 了解医院是否存在规模经济及适宜床位规模大小。方法 利用浙江省500张床及以上综合性医院数据,用主、客观结合的方式和效率回归调整模型筛选评价指标,用数据包络分析方法和Tobit回归模型进行实证分析。结果 所有决策单元的总体效率和纯技术效率、规模效率平均得分均大于0.93;36%的单元为总体有效,65%的单元为纯技术有效,43%的单元为规模有效;43%的单元处于规模报酬不变区间,42%的单元处于报酬递增区间,15%的单元处于报酬递减区间;全要素生产率平均呈下降;效率的影响因素主要有床位、药品收入比重、设备数量、医院等级、诊次床位比、业务收支比、每床卫技数、每床固定资产、所在地区千人医生数和经济水平等。结论 多数医院存在规模经济。医院床位数在800~1 300张较为合适。提高医院经营效率可采取以下措施:合理控制床位;控制药品收入比重,注重医疗技术的提高;提高管理水平,控制固定资产过度投入;提高地区卫生资源水平和经济发展水平。 相似文献
130.
心力衰竭是一种复杂的临床症候群,它是各种心脏病的终末阶段,发病率及病死率均较高,严重危害着人类健康,为了广泛深入地研究和治疗心力衰竭,迫切需要建立该病的动物模型。本综述复习了近年来文献,介绍目前较为成熟的心力衰竭动物模型的应用,同时比较之间的优缺点。 相似文献