全文获取类型
收费全文 | 47588篇 |
免费 | 16405篇 |
国内免费 | 5篇 |
出版年
2023年 | 95篇 |
2022年 | 145篇 |
2021年 | 680篇 |
2020年 | 2404篇 |
2019年 | 3974篇 |
2018年 | 4195篇 |
2017年 | 4385篇 |
2016年 | 4650篇 |
2015年 | 5026篇 |
2014年 | 4770篇 |
2013年 | 5453篇 |
2012年 | 3539篇 |
2011年 | 3145篇 |
2010年 | 4083篇 |
2009年 | 2715篇 |
2008年 | 1955篇 |
2007年 | 1605篇 |
2006年 | 1423篇 |
2005年 | 1424篇 |
2004年 | 1365篇 |
2003年 | 1261篇 |
2002年 | 1238篇 |
2001年 | 509篇 |
2000年 | 401篇 |
1999年 | 277篇 |
1998年 | 290篇 |
1997年 | 186篇 |
1996年 | 185篇 |
1995年 | 166篇 |
1994年 | 153篇 |
1993年 | 151篇 |
1992年 | 167篇 |
1991年 | 147篇 |
1990年 | 150篇 |
1989年 | 117篇 |
1988年 | 115篇 |
1987年 | 112篇 |
1986年 | 100篇 |
1985年 | 86篇 |
1984年 | 95篇 |
1983年 | 101篇 |
1982年 | 78篇 |
1981年 | 68篇 |
1980年 | 53篇 |
1979年 | 68篇 |
1978年 | 80篇 |
1977年 | 56篇 |
1976年 | 64篇 |
1975年 | 74篇 |
1974年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
The plasmodial slime molds is the largest group in the phylum Amoebozoa. Its life cycle includes the plasmodial trophic stage and the spore‐bearing fruiting bodies. However, only a few species have their complete life cycle known in details so far. This study is the first reporting the morphogenesis of Didymium laxifilum and Physarum album. Spores, from field‐collected sporangia, were incubated into hanging drop cultures for viewing germination and axenic oat agar plates for viewing plasmodial development and sporulation. The spores of D. laxifilum and P. album germinated by method of V‐shape split and minute pore, respectively. The amoeboflagellates, released from spores, were observed in water film. The phaneroplasmodia of two species developed into a number of sporangia by subhypothallic type on oat agar culture. The main interspecific difference of morphogenesis was also discussed. 相似文献
3.
Pelagostrobilidium liui n. sp. (Ciliophora,Choreotrichida) from the Coastal Waters of Northeastern Taiwan and an Improved Description of Pelagostrobilidium minutum Liu et al., 2012 下载免费PDF全文
Po‐Cheng Chen Kuo‐Ping Chiang Sheng‐Fang Tsai 《The Journal of eukaryotic microbiology》2017,64(5):579-587
The number of somatic kineties in Pelagostrobilidium ranges from 4 to 6 according to the present state of knowledge. This study investigates Pelagostrobilidium liui n. sp. using live observation, protargol stain, and small subunit rDNA data sequencing. Pelagostrobilidium liui n. sp. is characterized by having a spherical‐shaped body, four somatic kineties, with kinety 2 spiraled around the left side of body, about six elongated external membranelles, and invariably no buccal membranelle. It differs from its most similar congener, Pelagostrobilidium minutum Liu et al., 2012 , in (i) cell shape; (ii) macronucleus width; (iii) oral apparatus; (iv) anterior orientation of kinety 2; (v) location where kinety 2 commences; (vi) arrangement of kinety 1; (vii) distance between the anterior cell end and the locations where kineties commence; and (viii) the presence of 12 different bases (including two deletions) in the small subunit rDNA sequences. The diagnosis of P. minutum Liu et al., 2012 is also improved to include the following new characteristics: invariably four somatic kineties; kineties 2 and 4 alone commence at the same level; kinety 2 originates from right anterior cell half on ventral side, extends sinistrally posteriorly, over kinety 1, around left posterior region, terminates near posterior cell end on dorsal side; kinety 1 commences below anterior third of kinety 2. 相似文献
4.
Selective method for identification and quantification of Bifidobacterium animalis subspecies lactis BB‐12 (BB‐12) from the gastrointestinal tract of healthy volunteers ingesting a combination probiotic of BB‐12 and Lactobacillus rhamnosus GG 下载免费PDF全文
5.
Talia Dan‐Cohen 《The journal of the Royal Anthropological Institute》2017,23(2):285-301
Distinctions between the ‘simple’ and the ‘complex’ have enjoyed a long and varied career in anthropology. Simplicity was once part of a collective fantasy about what life was like elsewhere, tingeing studies of tribal life with human longing for simpler ways of being. With the reflexive turn and the rise of cultural critique, simplicity has been all but excommunicated in favour of widespread diagnoses of complexity. In this article, I tease out some transformations in the uses of complexity in anthropology, and weave in some critical responses to these uses, spanning many decades, from within the discipline. I pay special attention to recent critiques by anthropologists who are beginning to grow weary of complexity as both an end‐in‐itself for scholarship and an empirical diagnosis. For these critics, complexity is deeply entwined with anthropological methods and knowledge practices. Drawing on these critical views, I suggest that complexity may be an epistemological artefact, rather than something that can be diagnosed ‘out there’, and offer a way of reframing complexity as a ‘dominant problematic’ in anthropology and beyond. 相似文献
6.
Phenylephrine enhances glutamate release in the medial prefrontal cortex through interaction with N‐type Ca2+ channels and release machinery 下载免费PDF全文
Fei Luo Si‐hai Li Hua Tang Wei‐ke Deng Yu Zhang Ying Liu 《Journal of neurochemistry》2015,132(1):38-50
α1‐adrenoceptors (α1‐ARs) stimulation has been found to enhance excitatory processes in many brain regions. A recent study in our laboratory showed that α1‐ARs stimulation enhances glutamatergic transmission via both pre‐ and post‐synaptic mechanisms in layer V/VI pyramidal cells of the rat medial prefrontal cortex (mPFC). However, a number of pre‐synaptic mechanisms may contribute to α1‐ARs‐induced enhancement of glutamate release. In this study, we blocked the possible post‐synaptic action mediated by α1‐ARs to investigate how α1‐ARs activation regulates pre‐synaptic glutamate release in layer V/VI pyramidal neurons of mPFC. We found that the α1‐ARs agonist phenylephrine (Phe) induced a significant enhancement of glutamatergic transmission. The Phe‐induced potentiation was mediated by enhancing pre‐synaptic glutamate release probability and increasing the number of release vesicles via a protein kinase C‐dependent pathway. The mechanisms of Phe‐induced potentiation included interaction with both glutamate release machinery and N‐type Ca2+ channels, probably via a pre‐synaptic Gq/phospholipase C/protein kinase C pathway. Our results may provide a cellular and molecular mechanism that helps explain α1‐ARs‐mediated influence on PFC cognitive functions.
7.
8.
9.
Richard Ward Christos Pliotas Emma Branigan Christian Hacker Akiko Rasmussen Gregor Hagelueken Ian R. Booth Samantha Miller John Lucocq James H. Naismith Olav Schiemann 《Biophysical journal》2014
Mechanosensitive channel proteins are important safety valves against osmotic shock in bacteria, and are involved in sensing touch and sound waves in higher organisms. The mechanosensitive channel of small conductance (MscS) has been extensively studied. Pulsed electron-electron double resonance (PELDOR or DEER) of detergent-solubilized protein confirms that as seen in the crystal structure, the outer ring of transmembrane helices do not pack against the pore-forming helices, creating an apparent void. The relevance of this void to the functional form of MscS in the bilayer is the subject of debate. Here, we report PELDOR measurements of MscS reconstituted into two lipid bilayer systems: nanodiscs and bicelles. The distance measurements from multiple mutants derived from the PELDOR data are consistent with the detergent-solution arrangement of the protein. We conclude, therefore, that the relative positioning of the transmembrane helices is preserved in mimics of the cell bilayer, and that the apparent voids are not an artifact of detergent solution but a property of the protein that will have to be accounted for in any molecular mechanism of gating. 相似文献
10.
Walter Maetzler Maren Ellerbrock Tanja Heger Christian Sass Daniela Berg Ralf Reilmann 《PloS one》2015,10(4)
Motor symptoms in Parkinson’s disease (PD) are usually assessed with semi-quantitative tests such as the Unified PD Rating Scale (UPDRS) which are limited by subjectivity, categorical design, and low sensitivity. Particularly bradykinesia as assessed e.g. with speeded index finger tapping exhibits low validity measures. This exploratory study set out to (i) assess whether force transducer-based objective and quantitative analysis of motor coordination in index finger tapping is able to distinguish between PD patients and controls, and (ii) assess longitudinal changes. Sixteen early-stage and 17 mid-stage PD patients as well as 18 controls were included in the cross-sectional part of the study; thirteen, 16 and 16 individuals of the respective groups agreed in a reassessment 12 months later. Frequency, force, rhythmicity, regularity and laterality of speeded and metronome paced tapping were recorded by digitomotography using a quantitative motor system ("Q-Motor"). Analysis of cross-sectional data revealed most consistent differences between PD patients and controls in variability of tap performance across modalities assessed. Among PD patients, variability of taps and the ability to keep a given rhythm were associated with UPDRS motor and finger tapping scores. After 12 months, laterality parameters were reduced but no other parameters changed significantly. This data suggests that digitomotography provides quantitative and objective measures capable to differentiate PD from non-PD in a small cohort, however, the value of the assessment to track PD progression has to be further evaluated in larger cohorts of patients. 相似文献