全文获取类型
收费全文 | 79126篇 |
免费 | 5494篇 |
国内免费 | 28篇 |
专业分类
84648篇 |
出版年
2023年 | 498篇 |
2022年 | 662篇 |
2021年 | 1296篇 |
2020年 | 1030篇 |
2019年 | 1253篇 |
2018年 | 2155篇 |
2017年 | 1869篇 |
2016年 | 2554篇 |
2015年 | 3260篇 |
2014年 | 3457篇 |
2013年 | 4641篇 |
2012年 | 5499篇 |
2011年 | 5310篇 |
2010年 | 3367篇 |
2009年 | 2852篇 |
2008年 | 4148篇 |
2007年 | 4017篇 |
2006年 | 3895篇 |
2005年 | 3238篇 |
2004年 | 3252篇 |
2003年 | 2912篇 |
2002年 | 2734篇 |
2001年 | 2083篇 |
2000年 | 2089篇 |
1999年 | 1570篇 |
1998年 | 807篇 |
1997年 | 600篇 |
1996年 | 581篇 |
1995年 | 564篇 |
1994年 | 460篇 |
1993年 | 443篇 |
1992年 | 859篇 |
1991年 | 810篇 |
1990年 | 702篇 |
1989年 | 701篇 |
1988年 | 622篇 |
1987年 | 628篇 |
1986年 | 548篇 |
1985年 | 556篇 |
1984年 | 453篇 |
1983年 | 415篇 |
1982年 | 337篇 |
1981年 | 276篇 |
1979年 | 434篇 |
1978年 | 296篇 |
1977年 | 267篇 |
1975年 | 282篇 |
1974年 | 339篇 |
1973年 | 331篇 |
1972年 | 292篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
B Alexandre F Thiébaut M Allary E Boschetti C Séné J Saint-Blancard 《Revue fran?aise de transfusion et immuno-hématologie》1987,30(1):57-66
In this work the human plasma fibronectin was purified by affinity chromatography using a tandem column system. The first affinity column was filled with gelatin-Trisacryl whereas the second one contained heparin-Trisacryl. This double affinity chromatography demonstrated its high efficiency in term of purity and yield. Several analytical methods (electrophoresis, immunoelectrophoresis, F.P.L.C. and adhesion assay on cultured eucaryotic cells) evidenced in fact the high purity of the preparation as well as its biological behaviour in term of cell adhesion and spreading. The performances of the sorbents used facilitate the scaling up when large quantities of FNP are needed. 相似文献
33.
R M Agüero G Picó E Guibert J L Corchs 《Comparative biochemistry and physiology. B, Comparative biochemistry》1987,86(1):7-10
The interaction of ANS with rat hepatocytes in time was studied by fluorescence spectroscopy. The intercept of the first linear portion of the time curve of interaction showed a positive value over all the ANS concentration range employed. This value was maintained after cellular disruption by homogenization. It was affected by ionic strength, pH, and divalent cation in the incubation medium, all conditions affecting the cellular surface. These data suggest that this phenomenon might be a binding of the compound to the hepatocytes surface. Due to the time constant and its disappearance after cellular disruption the other slower component of the curve seems to correspond to a process of translocation across the membrane. 相似文献
34.
35.
A Sólyom S Tóth I Holczinger J Vajda Z Tóth R Kálmánchey 《Applied neurophysiology》1985,48(1-6):222-225
Four thalamic and cortical recordings were carried out in 5 patients. The thalamic-evoked potentials were typical and revealed a triphasic complex, but their latencies showed a relatively high standard deviation. They could be divided into two groups according to their latencies, both of which had low SD. These data suggested that there could be two types of latency of thalamic SEP, because the 4 patients' body sizes were very similar. More detailed surface, cortical and depth recordings are needed to resolve these questions. 相似文献
36.
37.
M Górska 《Polski tygodnik lekarski (Warsaw, Poland : 1960)》1992,47(46-48):1069-1071
38.
39.
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
40.
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