全文获取类型
收费全文 | 2900篇 |
免费 | 319篇 |
国内免费 | 2篇 |
出版年
2023年 | 10篇 |
2022年 | 19篇 |
2021年 | 79篇 |
2020年 | 33篇 |
2019年 | 70篇 |
2018年 | 76篇 |
2017年 | 59篇 |
2016年 | 97篇 |
2015年 | 149篇 |
2014年 | 156篇 |
2013年 | 175篇 |
2012年 | 229篇 |
2011年 | 195篇 |
2010年 | 170篇 |
2009年 | 129篇 |
2008年 | 168篇 |
2007年 | 173篇 |
2006年 | 145篇 |
2005年 | 122篇 |
2004年 | 118篇 |
2003年 | 91篇 |
2002年 | 115篇 |
2001年 | 40篇 |
2000年 | 48篇 |
1999年 | 34篇 |
1998年 | 41篇 |
1997年 | 22篇 |
1996年 | 23篇 |
1995年 | 23篇 |
1994年 | 21篇 |
1993年 | 22篇 |
1992年 | 30篇 |
1991年 | 27篇 |
1990年 | 25篇 |
1989年 | 24篇 |
1988年 | 17篇 |
1987年 | 15篇 |
1986年 | 19篇 |
1985年 | 17篇 |
1984年 | 17篇 |
1983年 | 10篇 |
1980年 | 10篇 |
1977年 | 17篇 |
1976年 | 10篇 |
1974年 | 8篇 |
1973年 | 9篇 |
1972年 | 10篇 |
1971年 | 9篇 |
1969年 | 9篇 |
1967年 | 9篇 |
排序方式: 共有3221条查询结果,搜索用时 203 毫秒
71.
Nora M. Bello Juan P. Steibel Robert J. Tempelman 《Biometrical journal. Biometrische Zeitschrift》2010,52(3):297-313
Bivariate mixed effects models are often used to jointly infer upon covariance matrices for both random effects ( u ) and residuals ( e ) between two different phenotypes in order to investigate the architecture of their relationship. However, these (co)variances themselves may additionally depend upon covariates as well as additional sets of exchangeable random effects that facilitate borrowing of strength across a large number of clusters. We propose a hierarchical Bayesian extension of the classical bivariate mixed effects model by embedding additional levels of mixed effects modeling of reparameterizations of u‐ level and e ‐level (co)variances between two traits. These parameters are based upon a recently popularized square‐root‐free Cholesky decomposition and are readily interpretable, each conveniently facilitating a generalized linear model characterization. Using Markov Chain Monte Carlo methods, we validate our model based on a simulation study and apply it to a joint analysis of milk yield and calving interval phenotypes in Michigan dairy cows. This analysis indicates that the e ‐level relationship between the two traits is highly heterogeneous across herds and depends upon systematic herd management factors. 相似文献
72.
Akchheta Karki Joachim Vollbrecht Alexander J. Gillett Philipp Selter Jaewon Lee Zhengxing Peng Nora Schopp Alana L. Dixon Max Schrock Vojtech Ndady Franz Schauer Harald Ade Bradley F. Chmelka Guillermo C. Bazan Richard H. Friend Thuc‐Quyen Nguyen 《Liver Transplantation》2020,10(29)
Even though significant breakthroughs with over 18% power conversion efficiencies (PCEs) in polymer:non‐fullerene acceptor (NFA) bulk heterojunction organic solar cells (OSCs) have been achieved, not many studies have focused on acquiring a comprehensive understanding of the underlying mechanisms governing these systems. This is because it can be challenging to delineate device photophysics in polymer:NFA blends comprehensively, and even more complicated to trace the origins of the differences in device photophysics to the subtle differences in energetics and morphology. Here, a systematic study of a series of polymer:NFA blends is conducted to unify and correlate the cumulative effects of i) voltage losses, ii) charge generation efficiencies, iii) non‐geminate recombination and extraction dynamics, and iv) nuanced morphological differences with device performances. Most importantly, a deconvolution of the major loss processes in polymer:NFA blends and their connections to the complex BHJ morphology and energetics are established. An extension to advanced morphological techniques, such as solid‐state NMR (for atomic level insights on the local ordering and donor:acceptor π? π interactions) and resonant soft X‐ray scattering (for donor and acceptor interfacial area and domain spacings), provide detailed insights on how efficient charge generation, transport, and extraction processes can outweigh increased voltage losses to yield high PCEs. 相似文献
73.
74.
Fuentes Antón S. Reyes E. Sánchez de la Cruz D. Rodríguez Sánchez A. García Dávila I. Sánchez J. Sánchez 《Aerobiologia》2021,37(4):809-824
Aerobiologia - The purpose of this study is to contribute to the knowledge about fungal spores in the atmosphere of the city of Salamanca (Middle West Spain), through the comparative study of... 相似文献
75.
76.
77.
Ctia Monteiro Huiru Li Nora Diehl Jonas Colln Sandra Heinrich Kai Bischof Inka Bartsch 《Phycological Research》2021,69(1):48-57
The sugar kelp Saccharina latissima experiences a wide range of environmental conditions along its geographical and vertical distribution range. Temperature and salinity are two critical drivers influencing growth, photosynthesis and biochemical composition. Moreover, interactive effects might modify the results described for single effects. In shallow water coastal systems, exposure to rising temperatures and low salinity are expected as consequence of global warming, increased precipitation and coastal run‐off. To understand the acclimation mechanisms of S. latissima to changes in temperature and salinity and their interactions, we performed a mechanistic laboratory experiment in which juvenile sporophytes from Brittany, France were exposed to a combination of three temperatures (0, 8 and 15°C) and two salinity levels (20 and 30 psu (practical salinity units)). After a temperature acclimation of 7 days, sporophytes were exposed to low salinity (20 psu) for a period of 11 days. Growth, and maximal quantum yield of photosystem II (Fv/Fm), pigments, mannitol content and C:N ratio were measured over time. We report for the first time in S. latissima a fivefold increase in the osmolyte mannitol in response to low temperature (0°C) compared to 8 and 15°C that may have ecological and economic implications. Low temperatures significantly affected all parameters, mostly in a negative way. Chlorophyll a, the accessory pigment pool, growth and Fv/Fm were significantly lower at 0°C, while the de‐epoxidation state of the xanthophyll cycle was increased at both 0 and 8°C compared to 15°C. Mannitol content and growth decreased with decreased salinity; in contrast, pigment content and Fv/Fm were to a large extent irresponsive to salinity. In comparison to S. latissima originating from an Arctic population, despite some reported differences, this study reveals a remarkably similar impact of temperature and salinity variation, reflecting the large degree of adaptability in this species. 相似文献
78.
79.
80.
Stefan Rüttermann Taina Trellenkamp Nora Bergmann Thomas Beikler Helmut Ritter Ralf Janda 《PloS one》2013,8(11)