全文获取类型
收费全文 | 4198篇 |
免费 | 389篇 |
国内免费 | 411篇 |
出版年
2023年 | 116篇 |
2022年 | 91篇 |
2021年 | 104篇 |
2020年 | 161篇 |
2019年 | 165篇 |
2018年 | 153篇 |
2017年 | 152篇 |
2016年 | 163篇 |
2015年 | 163篇 |
2014年 | 236篇 |
2013年 | 308篇 |
2012年 | 220篇 |
2011年 | 197篇 |
2010年 | 161篇 |
2009年 | 171篇 |
2008年 | 195篇 |
2007年 | 216篇 |
2006年 | 165篇 |
2005年 | 141篇 |
2004年 | 129篇 |
2003年 | 133篇 |
2002年 | 99篇 |
2001年 | 133篇 |
2000年 | 127篇 |
1999年 | 109篇 |
1998年 | 71篇 |
1997年 | 81篇 |
1996年 | 73篇 |
1995年 | 66篇 |
1994年 | 77篇 |
1993年 | 61篇 |
1992年 | 59篇 |
1991年 | 57篇 |
1990年 | 44篇 |
1989年 | 35篇 |
1988年 | 32篇 |
1987年 | 32篇 |
1986年 | 32篇 |
1985年 | 31篇 |
1984年 | 28篇 |
1983年 | 20篇 |
1982年 | 23篇 |
1981年 | 19篇 |
1980年 | 27篇 |
1979年 | 16篇 |
1978年 | 18篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1973年 | 13篇 |
1971年 | 12篇 |
排序方式: 共有4998条查询结果,搜索用时 15 毫秒
1.
Benjamin C. Blum Weiwei Lin Matthew L. Lawton Qian Liu Julian Kwan Isabella Turcinovic Ryan Hekman Pingzhao Hu Andrew Emili 《Molecular & cellular proteomics : MCP》2022,21(1):100189
Metabolism is recognized as an important driver of cancer progression and other complex diseases, but global metabolite profiling remains a challenge. Protein expression profiling is often a poor proxy since existing pathway enrichment models provide an incomplete mapping between the proteome and metabolism. To overcome these gaps, we introduce multiomic metabolic enrichment network analysis (MOMENTA), an integrative multiomic data analysis framework for more accurately deducing metabolic pathway changes from proteomics data alone in a gene set analysis context by leveraging protein interaction networks to extend annotated metabolic models. We apply MOMENTA to proteomic data from diverse cancer cell lines and human tumors to demonstrate its utility at revealing variation in metabolic pathway activity across cancer types, which we verify using independent metabolomics measurements. The novel metabolic networks we uncover in breast cancer and other tumors are linked to clinical outcomes, underscoring the pathophysiological relevance of the findings. 相似文献
2.
Ewa A. Czy Carla Guilln Escrib Hendrik Wulf Andrew Tedder Meredith C. Schuman Fabian D. Schneider Michael E. Schaepman 《Ecology and evolution》2020,10(14):7419-7430
- The growing pace of environmental change has increased the need for large‐scale monitoring of biodiversity. Declining intraspecific genetic variation is likely a critical factor in biodiversity loss, but is especially difficult to monitor: assessments of genetic variation are commonly based on measuring allele pools, which requires sampling of individuals and extensive sample processing, limiting spatial coverage. Alternatively, imaging spectroscopy data from remote platforms may hold the potential to reveal genetic structure of populations. In this study, we investigated how differences detected in an airborne imaging spectroscopy time series correspond to genetic variation within a population of Fagus sylvatica under natural conditions.
- We used multi‐annual APEX (Airborne Prism Experiment) imaging spectrometer data from a temperate forest located in the Swiss midlands (Laegern, 47°28'N, 8°21'E), along with microsatellite data from F. sylvatica individuals collected at the site. We identified variation in foliar reflectance independent of annual and seasonal changes which we hypothesize is more likely to correspond to stable genetic differences. We established a direct connection between the spectroscopy and genetics data by using partial least squares (PLS) regression to predict the probability of belonging to a genetic cluster from spectral data.
- We achieved the best genetic structure prediction by using derivatives of reflectance and a subset of wavebands rather than full‐analyzed spectra. Our model indicates that spectral regions related to leaf water content, phenols, pigments, and wax composition contribute most to the ability of this approach to predict genetic structure of F. sylvatica population in natural conditions.
- This study advances the use of airborne imaging spectroscopy to assess tree genetic diversity at canopy level under natural conditions, which could overcome current spatiotemporal limitations on monitoring, understanding, and preventing genetic biodiversity loss imposed by requirements for extensive in situ sampling.
3.
Semiparametric Regression in Size-Biased Sampling 总被引:1,自引:0,他引:1
Ying Qing Chen 《Biometrics》2010,66(1):149-158
Summary . Size-biased sampling arises when a positive-valued outcome variable is sampled with selection probability proportional to its size. In this article, we propose a semiparametric linear regression model to analyze size-biased outcomes. In our proposed model, the regression parameters of covariates are of major interest, while the distribution of random errors is unspecified. Under the proposed model, we discover that regression parameters are invariant regardless of size-biased sampling. Following this invariance property, we develop a simple estimation procedure for inferences. Our proposed methods are evaluated in simulation studies and applied to two real data analyses. 相似文献
4.
Ayenew Ejigou 《Biometrical journal. Biometrische Zeitschrift》1987,29(8):981-991
The odds ratio is known to closely approximate the relative risk when the disease is rare. Logistic regression models are often used to estimate such odds ratios, but here a different model is used which avoids the assumptions implicit in logistic modelling; it also has the advantage of providing a test of homogeneity for odds rat os in situations where the logistic model cannot. 相似文献
5.
6.
《Animal : an international journal of animal bioscience》2020,14(6):1120-1127
In order to map quantitative trait loci (QTLs) for allometries of body compositions and metabolic traits in chicken, we phenotypically characterize the allometric growths of multiple body components and metabolic traits relative to BWs using joint allometric scaling models and then establish random regression models (RRMs) to fit genetic effects of markers and minor polygenes derived from the pedigree on the allometric scalings. Prior to statistically inferring the QTLs for the allometric scalings by solving the RRMs, the LASSO technique is adopted to rapidly shrink most of marker genetic effects to zero. Computer simulation analysis confirms the reliability and adaptability of the so-called LASSO-RRM mapping method. In the F2 population constructed by multiple families, we formulate two joint allometric scaling models of body compositions and metabolic traits, in which six of nine body compositions are tested as significant, while six of eight metabolic traits are as significant. For body compositions, a total of 14 QTLs, of which 9 dominant, were detected to be associated with the allometric scalings of drumstick, fat, heart, shank, liver and spleen to BWs; while for metabolic traits, a total of 19 QTLs also including 9 dominant be responsible for the allometries of T4, IGFI, IGFII, GLC, INS, IGR to BWs. The detectable QTLs or highly linked markers can be used to regulate relative growths of the body components and metabolic traits to BWs in marker-assisted breeding of chickens. 相似文献
7.
Robert Biedermann 《Global Ecology and Biogeography》2003,12(5):381-387
Aim This paper tests firstly for the existence of a general relationship between body size of terrestrial animals and their incidence across habitat patches of increasing size, and secondly for differences in this relationship between insects and vertebrates. Location The analysis was based on the occupancy pattern of 50 species from 15 different landscapes in a variety of ecosystems ranging from Central European grassland to Asian tropical forest. Methods The area‐occupancy relationship was described by incidence functions that were calculated using logistic regression. A correlation analysis between body size of the species and the patch area referring to the two given points of the incidence function was performed. In order to test for an effect of taxon (insects vs. vertebrates), an analysis of covariance was conducted. Results In all species, the incidence was found to increase with increasing patch area. The macroecological analysis showed a significant relationship between the incidence in habitat patches and the body size of terrestrial animals. The area requirement was found to increase linearly with increasing body size on a log‐log scale. This relationship did not differ significantly between insects and vertebrates. Conclusions The approach highlighted in this paper is to associate incidence functions with body size. The results suggest that body size is a general but rather rough predictor for the area requirements of animals. The relationship seems valid for a wide range of body sizes of terrestrial animals. However, further studies including isolation of habitats as well as additional species traits into the macroecological analysis of incidence functions are needed. 相似文献
8.
The red-striped soft scale insect Pulvinaria tenuivalvata (Newstead) (Hemiptera: Coccidae) started to infest sugarcane plants (Saccharum officinarum L.) in different districts in Egypt during the last decade. The percentage of infestation was recorded in El-Wakf area, Qena Governorate (Naghhamadi mill zone) Upper Egypt in some fields. There are three levels of infestation, low, intermediate and high. From these fields, samples were selected for physical and chemical studies. The results obtained show that the stalks of infested plants decreased in weight, the sugar content (glucose and sucrose) drastically reduced and as the percentage of infestation increased the percentage of glucose and sucrose content significantly decreased. The primary and secondary humidity and the cellulose content also increased in the healthy plants compared to the infested ones. All the physical character of the infested plants was significantly affected in comparison with the healthy ones. 相似文献
9.
Erkki P. Liski 《Biometrical journal. Biometrische Zeitschrift》1989,31(3):313-316
Conditions for superiority of the minimum dispersion estimator over another with respect to the covariance matrix are derived when the vector parameter of a regression model is subject to competing stochastic restrictions. The restrictions may also consist both of a deterministic part and a stochastic part. 相似文献
10.
Effect of pea bacterial blight (Pseudomonas syringae pv. pisi) on the yield of spring sown combining peas (Pisum sativum) 总被引:1,自引:0,他引:1
S J ROBERTS K PHELPS B M McKEOWN M C HEATH V COCKERELL 《The Annals of applied biology》1995,126(1):61-73
Field trials to examine the effect of pea bacterial blight (Pseudomonas syringae pv. pisi) (Psp) on the yield of combining peas were carried out at five sites (HRI Wellesbourne, ADAS Rosemaund, ADAS Terrington, PGRO, SASA East Craigs) in the UK in 1990, 1991 and 1992. Healthy seed, cv. Solara, and seed naturally infected with Psp Race 2 was sown in large plots (c. 200 m2) in the open or under nets to prevent bird damage by pigeons. Despite relatively low disease severity levels (< 15% leaf area) and separation by at least 12 m of cv. Consort (resistant to Race 2) between plots there was considerable spread of disease into plots sown with healthy seed. Regression analysis demonstrated a significant relationship between yield and disease. Of the disease measurements examined, disease severity on the leaves (stipules) at growth stage 208 was found to be the best predictor of yield. A model containing environmental and bird damage terms, in addition to disease, suggested that a yield loss of 0.98 t/ha would be expected for a disease severity score of 1, equivalent to 5% leaf area affected, at growth stage 208. 相似文献