全文获取类型
收费全文 | 62911篇 |
免费 | 17519篇 |
国内免费 | 16篇 |
出版年
2023年 | 236篇 |
2022年 | 605篇 |
2021年 | 1287篇 |
2020年 | 2634篇 |
2019年 | 4274篇 |
2018年 | 4637篇 |
2017年 | 4751篇 |
2016年 | 5262篇 |
2015年 | 5857篇 |
2014年 | 5641篇 |
2013年 | 6845篇 |
2012年 | 5027篇 |
2011年 | 4586篇 |
2010年 | 4874篇 |
2009年 | 3391篇 |
2008年 | 3007篇 |
2007年 | 2553篇 |
2006年 | 2284篇 |
2005年 | 2128篇 |
2004年 | 1986篇 |
2003年 | 1913篇 |
2002年 | 1745篇 |
2001年 | 550篇 |
2000年 | 392篇 |
1999年 | 428篇 |
1998年 | 391篇 |
1997年 | 260篇 |
1996年 | 257篇 |
1995年 | 237篇 |
1994年 | 235篇 |
1993年 | 223篇 |
1992年 | 143篇 |
1991年 | 149篇 |
1990年 | 149篇 |
1989年 | 116篇 |
1988年 | 101篇 |
1987年 | 94篇 |
1986年 | 71篇 |
1985年 | 98篇 |
1984年 | 96篇 |
1983年 | 72篇 |
1982年 | 83篇 |
1981年 | 80篇 |
1980年 | 80篇 |
1979年 | 72篇 |
1978年 | 40篇 |
1977年 | 52篇 |
1975年 | 38篇 |
1974年 | 36篇 |
1973年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Alexandre Suire Lynne A. Isbell Laura R. Bidner Yushin Shinoda Munemitsu Akasaka Akiko Matsumoto‐Oda 《American journal of primatology》2021,83(1)
For diurnal nonhuman primates, shifting among different sleeping sites may provide multiple benefits such as better protection from predators, reduced risk of parasitic infection, and closer proximity to spatially and temporally heterogeneous food and water. This last benefit may be particularly important in sleeping site selection by primates living in savanna‐woodlands where rainfall is more limited and more seasonally pronounced than in rainforests. Here, we examined the influence of rainfall, a factor that affects food and water availability, on the use of sleeping sites by anubis baboons (Papio anubis) over two 13‐month study periods that differed in rainfall patterns. We predicted that during wet periods, when food and water availability should be higher, the study group would limit the number of sleeping sites and would stay at each one for more consecutive nights than during dry periods. Conversely, we predicted that during dry periods the group would increase the number of sleeping sites and stay at each one for fewer consecutive nights as they searched more widely for food and water. We also predicted that the group would more often choose sleeping sites closer to the center of the area used during daytime (between 07:00 and 19:00) during wet months than during dry months. Using Global Positioning System data from collared individuals, we found that our first prediction was not supported on either monthly or yearly timescales, although past monthly rainfall predicted the use of the main sleeping site in the second study period. Our second prediction was supported only on a yearly timescale. This study suggests that baboons’ choice of sleeping sites is fluid over time while being sensitive to local environmental conditions, one of which may be rainfall. 相似文献
72.
73.
P. Cruz C. H. Mejia‐Ruiz R. Perez‐Enriquez A. M. Ibarra 《Molecular ecology resources》2002,2(3):239-241
Five polymorphic microsatellite loci were characterized for Penaeus (Litopenaeus) vannamei. Loci were isolated using a partial Sau3A1 genomic library by the sequencing of randomly selected clones and by a biotinylated (CT)10 and (GT)10 probes screening procedure. The last strategy resulted in the most useful data. About 40% of the clones showed a previously reported satellite/microsatellite (PVS1), reducing the chance of finding new microsatellite regions. Whereas two of the microsatellite loci with more than 10 alleles will be useful for mating analysis in a breeding program, the others might prove useful for population genetic studies. 相似文献
74.
75.
Daneen Schaeffer Filipa Pereira Reis Sean J. Johnson Cec��lia Maria Arraiano Ambro van Hoof 《Nucleic acids research》2012,40(18):9298-9307
The 10-subunit RNA exosome is involved in a large number of diverse RNA processing and degradation events in eukaryotes. These reactions are carried out by the single catalytic subunit, Rrp44p/Dis3p, which is composed of three parts that are conserved throughout eukaryotes. The exosome is named for the 3′ to 5′ exoribonuclease activity provided by a large C-terminal region of the Rrp44p subunit that resembles other exoribonucleases. Rrp44p also contains an endoribonuclease domain. Finally, the very N-terminus of Rrp44p contains three Cys residues (CR3 motif) that are conserved in many eukaryotes but have no known function. These three conserved Cys residues cluster with a previously unrecognized conserved His residue in what resembles a metal-ion-binding site. Genetic and biochemical data show that this CR3 motif affects both endo- and exonuclease activity in vivo and both the nuclear and cytoplasmic exosome, as well as the ability of Rrp44p to associate with the other exosome subunits. These data provide the first direct evidence that the exosome-Rrp44p interaction is functionally important and also provides a molecular explanation for the functional defects when the conserved Cys residues are mutated. 相似文献
76.
77.
78.
79.
80.
T. Phanitchat C. Apiwathnasorn S. Sungvornyothin Y. Samung S. Dujardin J.‐P. Dujardin S. Sumruayphol 《Medical and veterinary entomology》2019,33(4):476-484
Wing geometry helps to identify mosquito species, even cryptic ones. On the other hand, temperature has a well‐known effect on insect metric properties. Can such effects blur the taxonomic signal embedded in the wing? Two strains of Aedes albopictus (laboratory and field strain) were examined under three different rearing temperatures (26, 30 and 33 °C) using landmark‐ and outline‐based morphometric approaches. The wings of each experimental line were compared with Aedes aegypti. Both approaches indicated similar associations between wing size and temperature. For the laboratory strain, the wing size significantly decreased as the temperature increased. For the field strain, the largest wings were observed at the intermediate temperature. The two morphometric approaches describing shape showed different sensibilities to temperature. For both strains and sexes, the landmark‐based approach disclosed significant wing shape changes with temperature changes. The outline‐based approach showed lesser effects, detecting significant changes only in laboratory females and in field males. Despite the size and shape changes induced by temperature, the two strains of Ae. albopictus were always distinguished from Ae. aegypti. The present study confirms the lability of size. However, it also suggests that, despite environmentally‐induced variation, the architecture of the wing still provides a strong taxonomic signal. 相似文献