全文获取类型
收费全文 | 2086篇 |
免费 | 220篇 |
国内免费 | 1篇 |
出版年
2023年 | 21篇 |
2022年 | 20篇 |
2021年 | 98篇 |
2020年 | 49篇 |
2019年 | 54篇 |
2018年 | 71篇 |
2017年 | 63篇 |
2016年 | 97篇 |
2015年 | 137篇 |
2014年 | 146篇 |
2013年 | 128篇 |
2012年 | 198篇 |
2011年 | 165篇 |
2010年 | 83篇 |
2009年 | 72篇 |
2008年 | 99篇 |
2007年 | 65篇 |
2006年 | 64篇 |
2005年 | 64篇 |
2004年 | 58篇 |
2003年 | 51篇 |
2002年 | 54篇 |
2001年 | 29篇 |
2000年 | 19篇 |
1999年 | 16篇 |
1998年 | 8篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1994年 | 9篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 13篇 |
1989年 | 18篇 |
1988年 | 7篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1984年 | 18篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1977年 | 7篇 |
1974年 | 8篇 |
1973年 | 7篇 |
1969年 | 9篇 |
1968年 | 14篇 |
1964年 | 8篇 |
1963年 | 9篇 |
1960年 | 9篇 |
1959年 | 8篇 |
1958年 | 8篇 |
1957年 | 7篇 |
排序方式: 共有2307条查询结果,搜索用时 187 毫秒
51.
Hirschstein Zall Novakovic Zachary M. Grasso Patricia 《International journal of peptide research and therapeutics》2020,26(4):1981-1990
International Journal of Peptide Research and Therapeutics - In addition to its roles in regulating energy balance and glucose homeostasis, leptin greatly influences hippocampal learning and... 相似文献
52.
Kelly O. Maloney Kevin P. Krause Claire Buchanan Lauren E. Hay Gregory J. McCabe Zachary M. Smith Terry L. Sohl John A. Young 《Global Change Biology》2020,26(4):2251-2269
Land‐use and climate change are significantly affecting stream ecosystems, yet understanding of their long‐term impacts is hindered by the few studies that have simultaneously investigated their interaction and high variability among future projections. We modeled possible effects of a suite of 2030, 2060, and 2090 land‐use and climate scenarios on the condition of 70,772 small streams in the Chesapeake Bay watershed, United States. The Chesapeake Basin‐wide Index of Biotic Integrity, a benthic macroinvertebrate multimetric index, was used to represent stream condition. Land‐use scenarios included four Special Report on Emissions Scenarios (A1B, A2, B1, and B2) representing a range of potential landscape futures. Future climate scenarios included quartiles of future climate changes from downscaled Coupled Model Intercomparison Project ‐ Phase 5 (CMIP5) and a watershed‐wide uniform scenario (Lynch2016). We employed random forests analysis to model individual and combined effects of land‐use and climate change on stream conditions. Individual scenarios suggest that by 2090, watershed‐wide conditions may exhibit anywhere from large degradations (e.g., scenarios A1B, A2, and the CMIP5 25th percentile) to small degradations (e.g., scenarios B1, B2, and Lynch2016). Combined land‐use and climate change scenarios highlighted their interaction and predicted, by 2090, watershed‐wide degradation in 16.2% (A2 CMIP5 25th percentile) to 1.0% (B2 Lynch2016) of stream kilometers. A goal for the Chesapeake Bay watershed is to restore 10% of stream kilometers over a 2008 baseline; our results suggest meeting and sustaining this goal until 2090 may require improvement in 11.0%–26.2% of stream kilometers, dependent on land‐use and climate scenario. These results highlight inherent variability among scenarios and the resultant uncertainty of predicted conditions, which reinforces the need to incorporate multiple scenarios of both land‐use (e.g., development, agriculture, etc.) and climate change in future studies to encapsulate the range of potential future conditions. 相似文献
53.
Zachary P. Cohen Kristian Brevik Yolanda H. Chen David J. Hawthorne Benjamin D. Weibel Sean D. Schoville 《Molecular ecology》2021,30(1):237-254
Contextualizing evolutionary history and identifying genomic features of an insect that might contribute to its pest status is important in developing early detection and control tactics. In order to understand the evolution of pestiferousness, which we define as the accumulation of traits that contribute to an insect population's success in an agroecosystem, we tested the importance of known genomic properties associated with rapid adaptation in the Colorado potato beetle (CPB), Leptinotarsa decemlineata Say. Within the leaf beetle genus Leptinotarsa, only CPB, and a few populations therein, has risen to pest status on cultivated nightshades, Solanum. Using whole genomes from ten closely related Leptinotarsa species native to the United States, we reconstructed a high‐quality species tree and used this phylogenetic framework to assess evolutionary patterns in four genomic features of rapid adaptation: standing genetic variation, gene family expansion and contraction, transposable element abundance and location, and positive selection at protein‐coding genes. Throughout approximately 20 million years of history, Leptinotarsa species show little evidence of gene family turnover and transposable element variation. However, there is a clear pattern of CPB experiencing higher rates of positive selection on protein‐coding genes. We determine that these rates are associated with greater standing genetic variation due to larger effective population size, which supports the theory that the demographic history contributes to rates of protein evolution. Furthermore, we identify a suite of coding genes under positive selection that are putatively associated with pestiferousness in the Colorado potato beetle lineage. They are involved in the biological processes of xenobiotic detoxification, chemosensation and hormone function. 相似文献
54.
55.
56.
57.
Chua Fu Yee Novakovic Zachary M. Grasso Patricia 《International journal of peptide research and therapeutics》2021,27(4):2223-2230
International Journal of Peptide Research and Therapeutics - Oral delivery of MA-[d-Leu-4]-OB3 has been shown to significantly improve energy balance, glycemic control, dyslipidemia, and episodic... 相似文献
58.
Zachary J. Domire John H. Challis 《Computer methods in biomechanics and biomedical engineering》2013,16(6):693-699
The maximum velocity of shortening of a muscle is an important parameter in musculoskeletal models. The most commonly used values are derived from animal studies; however, these values are well above the values that have been reported for human muscle. The purpose of this study was to examine the sensitivity of simulations of maximum vertical jumping performance to the parameters describing the force–velocity properties of muscle. Simulations performed with parameters derived from animal studies were similar to measured jump heights from previous experimental studies. While simulations performed with parameters derived from human muscle were much lower than previously measured jump heights. If current measurements of maximum shortening velocity in human muscle are correct, a compensating error must exist. Of the possible compensating errors that could produce this discrepancy, it was concluded that reduced muscle fibre excursion is the most likely candidate. 相似文献
59.
Anneleen Daemen Obi L Griffith Laura M Heiser Nicholas J Wang Oana M Enache Zachary Sanborn Francois Pepin Steffen Durinck James E Korkola Malachi Griffith Joe S Hur Nam Huh Jongsuk Chung Leslie Cope Mary Jo Fackler Christopher Umbricht Saraswati Sukumar Pankaj Seth Vikas P Sukhatme Lakshmi R Jakkula Yiling Lu Gordon B Mills Raymond J Cho Eric A Collisson Laura J van’t Veer Paul T Spellman Joe W Gray 《Genome biology》2013,14(10):R110
60.
Hadar Ben-Gida Adam Kirchhefer Zachary J. Taylor Wayne Bezner-Kerr Christopher G. Guglielmo Gregory A. Kopp Roi Gurka 《PloS one》2013,8(11)
Wing flapping is one of the most widespread propulsion methods found in nature; however, the current understanding of the aerodynamics in bird wakes is incomplete. The role of the unsteady motion in the flow and its contribution to the aerodynamics is still an open question. In the current study, the wake of a freely flying European starling has been investigated using long-duration high-speed Particle Image Velocimetry (PIV) in the near wake. Kinematic analysis of the wings and body of the bird has been performed using additional high-speed cameras that recorded the bird movement simultaneously with the PIV measurements. The wake evolution of four complete wingbeats has been characterized through reconstruction of the time-resolved data, and the aerodynamics in the wake have been analyzed in terms of the streamwise forces acting on the bird. The profile drag from classical aerodynamics was found to be positive during most of the wingbeat cycle, yet kinematic images show that the bird does not decelerate. It is shown that unsteady aerodynamics are necessary to satisfy the drag/thrust balance by approximating the unsteady drag term. These findings may shed light on the flight efficiency of birds by providing a partial answer to how they minimize drag during flapping flight. 相似文献