全文获取类型
收费全文 | 23858篇 |
免费 | 2069篇 |
国内免费 | 10篇 |
出版年
2023年 | 140篇 |
2022年 | 352篇 |
2021年 | 635篇 |
2020年 | 359篇 |
2019年 | 451篇 |
2018年 | 528篇 |
2017年 | 433篇 |
2016年 | 798篇 |
2015年 | 1322篇 |
2014年 | 1415篇 |
2013年 | 1713篇 |
2012年 | 2034篇 |
2011年 | 1827篇 |
2010年 | 1198篇 |
2009年 | 1004篇 |
2008年 | 1384篇 |
2007年 | 1372篇 |
2006年 | 1237篇 |
2005年 | 1152篇 |
2004年 | 1120篇 |
2003年 | 975篇 |
2002年 | 942篇 |
2001年 | 184篇 |
2000年 | 131篇 |
1999年 | 176篇 |
1998年 | 246篇 |
1997年 | 170篇 |
1996年 | 156篇 |
1995年 | 137篇 |
1994年 | 105篇 |
1993年 | 117篇 |
1992年 | 98篇 |
1991年 | 85篇 |
1990年 | 86篇 |
1989年 | 88篇 |
1988年 | 76篇 |
1987年 | 81篇 |
1986年 | 69篇 |
1985年 | 78篇 |
1984年 | 100篇 |
1983年 | 60篇 |
1982年 | 72篇 |
1981年 | 85篇 |
1980年 | 73篇 |
1979年 | 50篇 |
1978年 | 62篇 |
1977年 | 48篇 |
1976年 | 57篇 |
1974年 | 67篇 |
1973年 | 59篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Caitlin M. Cossaboom Laura Córdoba Dianjun Cao Yan-Yan Ni Xiang-Jin Meng 《Journal of virology》2012,86(23):13124-13125
Hepatitis E virus (HEV) is a single-strand positive-sense RNA virus in the family Hepeviridae. The disease caused by HEV, hepatitis E, is an important public health problem in developing countries of Asia and Africa and is also endemic in many industrialized countries, including the United States. HEV has been identified from several other animal species in addition to humans, including the pig, chicken, mongoose, deer, rabbit, ferret, bat, and fish. Here we report the complete genome sequence of the first strain of HEV from rabbits in the United States. Sequence and phylogenetic analyses revealed that the U.S. rabbit HEV is a distant member of the zoonotic genotype 3 HEV, thus raising a concern for potential zoonotic human infection. A unique 90-nucleotide insertion within the X domain of the ORF1 was identified in the rabbit HEV, and this insertion may play a role in the species tropism of HEV. 相似文献
12.
Molecular dynamics (MD) simulations of phosphatidylinositol (4,5)-bisphosphate (PIP2) and phosphatidylinositol (3,4,5)-trisphosphate (PIP3) in 1-palmitoyl 2-oleoyl phosphatidylcholine (POPC) bilayers indicate that the inositol rings are tilted ∼40° with respect to the bilayer surface, as compared with 17° for the P-N vector of POPC. Multiple minima were obtained for the ring twist (analogous to roll for an airplane). The phosphates at position 1 of PIP2 and PIP3 are within an Ångström of the plane formed by the phosphates of POPC; lipids in the surrounding shell are depressed by 0.5-0.8 Å, but otherwise the phosphoinositides do not substantially perturb the bilayer. Finite size artifacts for ion distributions are apparent for systems of ∼26 waters/lipid, but, based on simulations with a fourfold increase of the aqueous phase, the phosphoinositide positions and orientations do not show significant size effects. Electrostatic potentials evaluated from Poisson-Boltzmann (PB) calculations show a strong dependence of potential height and ring orientation, with the maxima on the −25 mV surfaces (17.1 ± 0.1 Å for PIP2 and 19.4 ± 0.3 Å for PIP3) occurring near the most populated orientations from MD. These surfaces are well above the background height of 10 Å estimated for negatively charged cell membranes, as would be expected for lipids involved in cellular signaling. PB calculations on microscopically flat bilayers yield similar maxima as the MD-based (microscopically rough) systems, but show less fine structure and do not clearly indicate the most probable regions. Electrostatic free energies of interaction with pentalysine are also similar for the rough and flat systems. These results support the utility of a rigid/flat bilayer model for PB-based studies of PIP2 and PIP3 as long as the orientations are judiciously chosen. 相似文献
13.
Margaret Jacobi 《BMJ (Clinical research ed.)》1981,283(6304):1444-1445
14.
15.
16.
17.
Laura W. Pomeroy Jacob M. Aaronson Samuel Handelman Jori Hardman Kevin Kawalec Thomas Bitterman Ward C. Wheeler 《Cladistics : the international journal of the Willi Hennig Society》2012,28(5):483-488
We have reported previously on use of a web‐based application, Supramap ( http://supramap.org ) for the study of biogeographic, genotypic, and phenotypic evolution. Using Supramap we have developed maps of the spread of drug‐resistant influenza and host shifts in H1N1 and H5N1 influenza and coronaviruses such as SARS. Here we report on another zoonotic pathogen, H7 influenza, and provide an update on the implementation of Supramap as a web service. We find that the emergence of pathogenic strains of H7 is labile with many transitions from high to low pathogenicity, and from low to high pathogenicity. We use Supramap to put these events in a temporal and geospatial context. We identify several lineages of H7 influenza with biomarkers of high pathogenicity in regions that have not been reported in the scientific literature. The original implementation of Supramap was built with tightly coupled client and server software. Now we have decoupled the components to provide a modular web service for POY ( http://poyws.org ) that can be consumed by a data provider to create a novel application. To demonstrate the web service, we have produced an application, Geogenes ( http://geogenes.org ). Unlike in Supramap, in which the user is required to create and upload data files, in Geogenes the user works from a graphical interface to query an underlying dataset. Geogenes demonstrates how the web service can provide underlying processing for any sequence and metadata database. © The Willi Hennig Society 2012. 相似文献
18.
19.
20.
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