全文获取类型
收费全文 | 17441篇 |
免费 | 1343篇 |
国内免费 | 12篇 |
出版年
2022年 | 150篇 |
2021年 | 289篇 |
2020年 | 158篇 |
2019年 | 199篇 |
2018年 | 272篇 |
2017年 | 281篇 |
2016年 | 418篇 |
2015年 | 677篇 |
2014年 | 767篇 |
2013年 | 984篇 |
2012年 | 1165篇 |
2011年 | 1086篇 |
2010年 | 739篇 |
2009年 | 672篇 |
2008年 | 956篇 |
2007年 | 983篇 |
2006年 | 912篇 |
2005年 | 901篇 |
2004年 | 846篇 |
2003年 | 846篇 |
2002年 | 771篇 |
2001年 | 214篇 |
2000年 | 186篇 |
1999年 | 272篇 |
1998年 | 250篇 |
1997年 | 198篇 |
1996年 | 172篇 |
1995年 | 167篇 |
1994年 | 162篇 |
1993年 | 153篇 |
1992年 | 163篇 |
1991年 | 161篇 |
1990年 | 163篇 |
1989年 | 138篇 |
1988年 | 144篇 |
1987年 | 80篇 |
1986年 | 102篇 |
1985年 | 114篇 |
1984年 | 136篇 |
1983年 | 104篇 |
1982年 | 134篇 |
1981年 | 118篇 |
1980年 | 98篇 |
1979年 | 79篇 |
1978年 | 85篇 |
1977年 | 86篇 |
1976年 | 78篇 |
1975年 | 77篇 |
1974年 | 80篇 |
1973年 | 77篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
The ultrasonic calls produced by three day old mice when separated from the nest mother and siblings increase in number when naloxone is injected. 相似文献
12.
Alain Dejean Arthur Compin Jacques H. C. Delabie Frdric Azmar Bruno Corbara Maurice Leponce 《Ecological Entomology》2019,44(4):560-570
1. Ants are widespread in tropical rainforests, including in the canopy where territorially dominant arboreal species represent the main part of the arthropod biomass. 2. By mapping the territories of dominant arboreal ant species and using a null model analysis and a pairwise approach this study was able to show the presence of an ant mosaic on the upper canopy of a primary Neotropical rainforest (c. 1 ha sampled; 157 tall trees from 28 families). Although Neotropical rainforest canopies are frequently irregular, with tree crowns at different heights breaking the continuity of the territories of dominant ants, the latter are preserved via underground galleries or trails laid on the ground. 3. The distribution of the trees influences the structure of the ant mosaic, something related to the attractiveness of tree taxa for certain arboreal ant species rather than others. 4. Small‐scale natural disturbances, most likely strong winds in the area studied (presence of canopy gaps), play a role by favouring the presence of two ant species typical of secondary formations: Camponotus femoratus and Crematogaster levior, which live in parabiosis (i.e. share territories and nests but lodge in different cavities) and build conspicuous ant gardens. In addition, pioneer Cecropia myrmecophytic trees were recorded. 相似文献
13.
Corine Vialas Geneviève Pratviel Jean Bernadou Bernard Meunier 《Nucleosides, nucleotides & nucleic acids》2013,32(4-5):1061-1063
Abstract Mn TMPyP in the presence of sulfite/O2 catalyses the oxidation of dG into dIz as selectively but slower and less efficiently than in the presence of KHSO5. 相似文献
14.
Céline Fouquet Bénédicte M. Babayan Aurélie Watilliaux Bruno Bontempi Christine Tobin Laure Rondi-Reig 《PloS one》2013,8(6)
We investigated the neural bases of navigation based on spatial or sequential egocentric representation during the completion of the starmaze, a complex goal-directed navigation task. In this maze, mice had to swim along a path composed of three choice points to find a hidden platform. As reported previously, this task can be solved by using two hippocampal-dependent strategies encoded in parallel i) the allocentric strategy requiring encoding of the contextual information, and ii) the sequential egocentric strategy requiring temporal encoding of a sequence of successive body movements associated to specific choice points. Mice were trained during one day and tested the following day in a single probe trial to reveal which of the two strategies was spontaneously preferred by each animal. Imaging of the activity-dependent gene c-fos revealed that both strategies are supported by an overlapping network involving the dorsal hippocampus, the dorsomedial striatum (DMS) and the medial prefrontal cortex. A significant higher activation of the ventral CA1 subregion was observed when mice used the sequential egocentric strategy. To investigate the potential different roles of the dorsal hippocampus and the DMS in both types of navigation, we performed region-specific excitotoxic lesions of each of these two structures. Dorsal hippocampus lesioned mice were unable to optimally learn the sequence but improved their performances by developing a serial strategy instead. DMS lesioned mice were severely impaired, failing to learn the task. Our data support the view that the hippocampus organizes information into a spatio-temporal representation, which can then be used by the DMS to perform goal-directed navigation. 相似文献
15.
Bruno Jirgensons 《Journal of Protein Chemistry》1982,1(1):71-84
The factors determining the onset and extent of reconstructive denaturation of proteins were considered by comparing circular dichroism (CD) data of seven proteins and previously published findings. The effects of sodium dodecyl sulfate (SDS) on the conformation of the following proteins were tested: lysozyme, the mitogens fromPhytolacca americana (fractions Pa2 and Pa4), lectin fromWistaria floribunda, ovine lutropin, a Bence Jones protein, and histone H2B. While the helix content of lysozyme was raised by SDS slightly, in the Bence Jones protein andW. floribunda lectin it increased from near zero to about 25–30%. In histone H2B the helix content was raised by SDS even to about 48%. However, no clear indication of helix formation could be observed in the mitogens and lutropin, even at low pH or 2.0–2.5. The tertiary structure of the proteins was perturbed by SDS. It was concluded that the reorganization of secondary structure of the proteins was favored by the following factors: (1) presence of helicogenic amino acid sequences in the protein, (2) availability of positively charged sites of the basic amino acids for interactions with the dodecyl ion, (3) absence of a large surplus of negatively charged sites on the surface of protein, and (4) absence of extensive disulfide cross-linking within the macromolecule. Both hydrophobic and electrostatic interactions occur in reconstructive denaturation, and the newly formed helices are stabilized by hydrophobic shielding by the alkyl chains of the alkyl sulfate. 相似文献
16.
Surface Plasmodium sugar-binding components evidenced by fluorescent neoglycoproteins 总被引:2,自引:0,他引:2
J Schrevel M Philippe F Bernard M Monsigny 《Biology of the cell / under the auspices of the European Cell Biology Organization》1986,56(1):49-55
A sugar-binding component was shown to be present at the surface of endoerythrocytic Plasmodium berghei and P. chabaudi stages and merozoites by means of a panel of neoglycoproteins using fluorescence microscopy and flow cytofluorometry. The protein nature of this material was ascertained by the loss of sugar-binding capacity upon trypsin treatment. This lectin-like protein primarily bound neoglycoprotein-borne N-acetylglucosamine and secondarily bound neoglycoprotein-borne alpha-D-glucose, beta-D-galactose and alpha-L-fucose. These results suggest the presence of at least one type of lectin-like protein with an extended binding site accomodating several sugar units, and define its localization on the parasite surface. 相似文献
17.
18.
19.
20.