全文获取类型
收费全文 | 3034篇 |
免费 | 224篇 |
国内免费 | 2篇 |
专业分类
3260篇 |
出版年
2023年 | 14篇 |
2022年 | 32篇 |
2021年 | 59篇 |
2020年 | 29篇 |
2019年 | 35篇 |
2018年 | 76篇 |
2017年 | 52篇 |
2016年 | 75篇 |
2015年 | 132篇 |
2014年 | 124篇 |
2013年 | 199篇 |
2012年 | 211篇 |
2011年 | 235篇 |
2010年 | 152篇 |
2009年 | 147篇 |
2008年 | 189篇 |
2007年 | 153篇 |
2006年 | 142篇 |
2005年 | 157篇 |
2004年 | 153篇 |
2003年 | 138篇 |
2002年 | 118篇 |
2001年 | 42篇 |
2000年 | 37篇 |
1999年 | 38篇 |
1998年 | 34篇 |
1997年 | 30篇 |
1996年 | 37篇 |
1995年 | 29篇 |
1994年 | 25篇 |
1993年 | 26篇 |
1992年 | 28篇 |
1991年 | 18篇 |
1990年 | 20篇 |
1989年 | 16篇 |
1988年 | 16篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 17篇 |
1984年 | 23篇 |
1983年 | 17篇 |
1982年 | 19篇 |
1981年 | 22篇 |
1980年 | 20篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1976年 | 16篇 |
1975年 | 8篇 |
1974年 | 6篇 |
排序方式: 共有3260条查询结果,搜索用时 10 毫秒
51.
Cortés-Sarabia Karen Bautista-Santos Isabel Cisneros-Sarabia Alondra Parra-Rojas Isela Estrada-Moreno Ana Karen Flores-Alfaro Eugenia Fernández-Tilapa Gloria Ramírez-Peralta Arturo Vences-Velázquez Amalia 《International journal of peptide research and therapeutics》2021,27(1):413-420
International Journal of Peptide Research and Therapeutics - Gardnerella vaginalis produces vaginolysin (VLY), a cholesterol-dependent cytolysin, responsible of the cellular lysis and epithelial... 相似文献
52.
Calabria G Dolgova O Rego C Castañeda LE Rezende EL Balanyà J Pascual M Sørensen JG Loeschcke V Santos M 《Journal of evolutionary biology》2012,25(4):691-700
Theory predicts that geographic variation in traits and genes associated with climatic adaptation may be initially driven by the correlated evolution of thermal preference and thermal sensitivity. This assumes that an organism's preferred body temperature corresponds with the thermal optimum in which performance is maximized; hence, shifts in thermal preferences affect the subsequent evolution of thermal-related traits. Drosophila subobscura evolved worldwide latitudinal clines in several traits including chromosome inversion frequencies, with some polymorphic inversions being apparently associated with thermal preference and thermal tolerance. Here we show that flies carrying the warm-climate chromosome arrangement O(3+4) have higher basal protein levels of Hsp70 than their cold-climate O(st) counterparts, but this difference disappears after heat hardening. O(3+4) carriers are also more heat tolerant, although it is difficult to conclude from our results that this is causally linked to their higher basal levels of Hsp70. The observed patterns are consistent with the thermal co-adaptation hypothesis and suggest that the interplay between behaviour and physiology underlies latitudinal and seasonal shifts in inversion frequencies. 相似文献
53.
Maria V.T. Lobo Rafael G. Santander Gloria M. Cuadrado F. Javier M. Alonso 《The Histochemical journal》1999,31(6):347-355
Myoblast fusion is a Ca2+-dependent process. The aim of this report was to study the localization of Ca2+ in prefusion myoblasts from the brachial somites of chick embryos (51–108h of incubation), using the potassium pyroantimonate cytochemical method. When observed under a transmission electron microscope, electron-dense precipitates of Ca2+-antimonate were found in the basement membrane of the myotome, which separates the myotome from the adjacent mesenchyma. Within myoblasts, triads and sarcoplasmic reticulum associated with the first newly formed sarcomeres were observed, but a T-tubule network was not found. Moreover, Ca2+-antimonate precipitates were not observed in structures resembling T-tubules or sarcoplasmic reticulum. The results suggest that sarcomerogenesis and sarcoplasmic reticulum development occur simultaneously and that prefusion myoblasts have neither a T-tubule network nor Ca2+ deposits on sarcoplasmic reticulum. Small Ca2+ pools were found in the myoblast nuclei, cytoplasmic vesicles and mitochondrias. Ca2+-antimonate precipitates periodically distributed at the cell periphery, close to the cell membrane, were observed. These precipitates could represent internal Ca2+ stores located in the peripheral couplings and it is proposed that these pools of Ca2+ could be mobilized before fusion, leading to the increase in free intracellular Ca2+ that precedes myoblast fusion. 相似文献
54.
The rate of hexose transport was approximately 60% lower for both the high- and the low-affinity components of hexose uptake
when a glucose-6-phosphate isomerase mutant ofSaccharomyces cerevisiae was preincubated with glucose, as compared with preincubation with water. Similarly theJ
max value of the high-affinity system of the mutant was 25–35 % of the correspondingJ
max value for normal cells incubated with glucose. Accumulation of glucose 6-phosphate or of some other metabolite, such as fructose
6-phosphate or trehalose, may be responsible for this striking inhibition. 相似文献
55.
Andrea Gloria‐Soria Diego Ayala Ambicadutt Bheecarry Olger Calderon‐Arguedas Dave D. Chadee Marina Chiappero Maureen Coetzee Khouaildi Bin Elahee Ildefonso Fernandez‐Salas Hany A. Kamal Basile Kamgang Emad I. M. Khater Laura D. Kramer Vicki Kramer Alma Lopez‐Solis Joel Lutomiah Ademir Martins Jr Maria Victoria Micieli Christophe Paupy Alongkot Ponlawat Nil Rahola Syed Basit Rasheed Joshua B. Richardson Amag A. Saleh Rosa Maria Sanchez‐Casas Gonçalo Seixas Carla A. Sousa Walter J. Tabachnick Adriana Troyo Jeffrey R. Powell 《Molecular ecology》2016,25(21):5377-5395
Mosquitoes, especially Aedes aegypti, are becoming important models for studying invasion biology. We characterized genetic variation at 12 microsatellite loci in 79 populations of Ae. aegypti from 30 countries in six continents, and used them to infer historical and modern patterns of invasion. Our results support the two subspecies Ae. aegypti formosus and Ae. aegypti aegypti as genetically distinct units. Ae. aegypti aegypti populations outside Africa are derived from ancestral African populations and are monophyletic. The two subspecies co‐occur in both East Africa (Kenya) and West Africa (Senegal). In rural/forest settings (Rabai District of Kenya), the two subspecies remain genetically distinct, whereas in urban settings, they introgress freely. Populations outside Africa are highly genetically structured likely due to a combination of recent founder effects, discrete discontinuous habitats and low migration rates. Ancestral populations in sub‐Saharan Africa are less genetically structured, as are the populations in Asia. Introduction of Ae. aegypti to the New World coinciding with trans‐Atlantic shipping in the 16th to 18th centuries was followed by its introduction to Asia in the late 19th century from the New World or from now extinct populations in the Mediterranean Basin. Aedes mascarensis is a genetically distinct sister species to Ae. aegypti s.l. This study provides a reference database of genetic diversity that can be used to determine the likely origin of new introductions that occur regularly for this invasive species. The genetic uniqueness of many populations and regions has important implications for attempts to control Ae. aegypti, especially for the methods using genetic modification of populations. 相似文献
56.
Multiple residues specify external tetraethylammonium blockade in voltage-gated potassium channels. 总被引:3,自引:2,他引:3
We have mapped residues in the carboxyl half of the P region of a voltage-gated K+ channel that influence external tetraethylammonium (TEA) block. Fifteen amino acids were substituted with cysteine and expressed in oocytes from monomeric or heterodimeric cRNAs. From a total of six mutant channels with altered TEA sensitivity, three were susceptible to modification by extracellularly applied charged methanethiosulfonates (MTSX). Another residue did not affect TEA block but was protected from MTSX by TEA. MTSX modification of position Y380C, thought to form the TEA binding site, affected TEA affinity only moderately, and this effect could be reversed by additional charge transfer from an oppositely charged MTSX analog. The results show that TEA block is modulated from multiple sites, including residues located deep in the pore and that several side chains besides that of Y380 are exposed at the TEA receptor. 相似文献
57.
Elliot Meyerowitz the Biology Department, Caltech, and a member of the Board of Directors of the ISPMB, has been named Fellow of the American
Academy of Arts and Science. 相似文献
58.
59.
Juan Del Coso Javier Portillo Gloria Muñoz Javier Abián-Vicén Cristina Gonzalez-Millán Jesús Muñoz-Guerra 《Amino acids》2013,44(6):1511-1519
The aim of this study was to determine the effects of a caffeine-containing energy drink on physical performance during a rugby sevens competition. A second purpose was to investigate the post-competition urinary caffeine concentration derived from the energy drink intake. On two non-consecutive days of a friendly tournament, 16 women from the Spanish National rugby sevens Team (mean age and body mass = 23 ± 2 years and 66 ± 7 kg) ingested 3 mg of caffeine per kg of body mass in the form of an energy drink (Fure®, ProEnergetics) or the same drink without caffeine (placebo). After 60 min for caffeine absorption, participants performed a 15-s maximal jump test, a 6 × 30 m sprint test, and then played three rugby sevens games against another national team. Individual running pace and instantaneous speed during the games were assessed using global positioning satellite (GPS) devices. Urine samples were obtained pre and post-competition. In comparison to the placebo, the ingestion of the energy drink increased muscle power output during the jump series (23.5 ± 10.1 vs. 25.6 ± 11.8 kW, P = 0.05), running pace during the games (87.5 ± 8.3 vs. 95.4 ± 12.7 m/min, P < 0.05), and pace at sprint velocity (4.6 ± 3.3 vs. 6.1 ± 3.4 m/min, P < 0.05). However, the energy drink did not affect maximal running speed during the repeated sprint test (25.0 ± 1.5 vs. 25.0 ± 1.7 km/h). The ingestion of the energy drink resulted in a higher post-competition urine caffeine concentration than the placebo (3.3 ± 0.7 vs. 0.2 ± 0.1 μg/mL; P < 0.05). In summary, 3 mg/kg of caffeine in the form of a commercially available energy drink considerably enhanced physical performance during a women’s rugby sevens competition. 相似文献
60.