全文获取类型
收费全文 | 101559篇 |
免费 | 6854篇 |
国内免费 | 16篇 |
出版年
2023年 | 665篇 |
2022年 | 821篇 |
2021年 | 1614篇 |
2020年 | 1328篇 |
2019年 | 1509篇 |
2018年 | 2826篇 |
2017年 | 2605篇 |
2016年 | 3444篇 |
2015年 | 4441篇 |
2014年 | 4701篇 |
2013年 | 6327篇 |
2012年 | 7409篇 |
2011年 | 6847篇 |
2010年 | 4416篇 |
2009年 | 3685篇 |
2008年 | 5385篇 |
2007年 | 5099篇 |
2006年 | 4768篇 |
2005年 | 4053篇 |
2004年 | 4040篇 |
2003年 | 3629篇 |
2002年 | 3329篇 |
2001年 | 2371篇 |
2000年 | 2278篇 |
1999年 | 1845篇 |
1998年 | 953篇 |
1997年 | 726篇 |
1996年 | 711篇 |
1995年 | 680篇 |
1994年 | 573篇 |
1993年 | 529篇 |
1992年 | 1003篇 |
1991年 | 900篇 |
1990年 | 832篇 |
1989年 | 828篇 |
1988年 | 766篇 |
1987年 | 724篇 |
1986年 | 660篇 |
1985年 | 675篇 |
1984年 | 587篇 |
1983年 | 507篇 |
1982年 | 433篇 |
1981年 | 366篇 |
1979年 | 479篇 |
1978年 | 407篇 |
1975年 | 389篇 |
1974年 | 466篇 |
1973年 | 450篇 |
1972年 | 363篇 |
1969年 | 354篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Ivonne J. Garzn‐Ordua Shaun L. Winterton Yunlan Jiang Laura C.V. Breitkreuz Peter Duelli Michael S. Engel Norman D. Penny Catherine A. Tauber Atsushi Mochizuki Xingyue Liu 《Systematic Entomology》2019,44(3):499-513
We present a time‐calibrated phylogeny of the charismatic green lacewings (Neuroptera: Chrysopidae). Previous phylogenetic studies on the family using DNA sequences have suffered from sparse taxon sampling and/or limited amounts of data. Here we combine all available previously published DNA sequence data and add to it new DNA sequences generated for this study. We analysed these data in a supermatrix using Bayesian and maximum likelihood methods and provide a phylogenetic hypothesis for the family that recovers strong support for the monophyly of all subfamilies and resolves relationships among a large proportion of chrysopine genera. Chrysopinae tribes Leucochrysini and Belonopterygini were recovered as monophyletic sister clades, while the species‐rich tribe Chrysopini was rendered paraphyletic by Ankylopterygini. Relationships among the subfamilies were resolved, although with relatively low statistical support, and the topology varied based on the method of analysis. Greatest support was found for Apochrysinae as sister to Nothochrysinae and Chrysopinae, which is in contrast to traditional concepts that place Nothochrysinae as sister to the rest of the family. Divergence estimates suggest that the stem groups to the various subfamilies diverged during the Triassic‐Jurassic, and that stem groups of the chrysopine tribes diverged during the Cretaceous. 相似文献
32.
H Vaer?y F Nyberg H Franzén L Terenius 《Biochemical and biophysical research communications》1987,148(1):24-30
Enzyme activity capable of converting the glycine-extended substance P precursor, substance P-Gly12, into substance P was purified from human cerebrospinal fluid. The conversion reaction was monitored by radioimmunoassay measurement of substance P formation. The chemical identity of the product was verified by reversed-phase HPLC. The enzyme reaction was stimulated by Cu(II) ion and ascorbic acid and inhibited by the presence of diethyldithiocarbamate. By HPLC molecular sieving, the major enzyme activity appeared as a protein of 26,000 molecular weight. 相似文献
33.
34.
L Chrobák D Radochová K Smetana F Mat?ja M Kout J Polák P Dít? J Pribrosky I Dvorácková 《Folia haematologica (Leipzig, Germany : 1928)》1980,107(4):628-640
These siblings of a Czech family aged 21, 19 and 6 years, respectively, with congenital dyserythropoietic anemia, type II, (HEMPAS) are reported. In two elder siblings ferrokinetic studies revealed a rapid plasma 59Fe clearance, markedly decreased erythrocyte incorporation and shortened 51Cr red-cell survival. Direct anti-globulin test was found positive in one of them. Further investigations revealed low values of blood plasma cholesterol, total lipids, beta-lipoproteins, beta-carotine and vitamin E and A as well as low values of the prothrombin complex. Liver biopsy demonstrated siderosis and disseminated intravascular coagulation in the liver in both patients. The possible reasons for these humoral aberrations are discussed. 相似文献
35.
36.
37.
Petronela Weisová Ujval Anilkumar Caitriona Ryan Caoimhín G. Concannon Jochen H.M. Prehn Manus W. Ward 《BBA》2012,1817(5):744-753
The preconditioning response conferred by a mild uncoupling of the mitochondrial membrane potential (Δψm) has been attributed to altered reactive oxygen species (ROS) production and mitochondrial Ca2 + uptake within the cells. Here we have explored if altered cellular energetics in response to a mild mitochondrial uncoupling stimulus may also contribute to the protection. The addition of 100 nM FCCP for 30 min to cerebellar granule neurons (CGNs) induced a transient depolarization of the Δψm, that was sufficient to significantly reduce CGN vulnerability to the excitotoxic stimulus, glutamate. On investigation, the mild mitochondrial ‘uncoupling’ stimulus resulted in a significant increase in the plasma membrane levels of the glucose transporter isoform 3, with a hyperpolarisation of Δψm and increased cellular ATP levels also evident following the washout of FCCP. Furthermore, the phosphorylation state of AMP-activated protein kinase (AMPK) (Thr 172) was increased within 5 min of the uncoupling stimulus and elevated up to 1 h after washout. Significantly, the physiological changes and protection evident after the mild uncoupling stimulus were lost in CGNs when AMPK activity was inhibited. This study identifies an additional mechanism through which protection is mediated upon mild mitochondrial uncoupling: it implicates increased AMPK signalling and an adaptive shift in energy metabolism as mediators of the preconditioning response associated with FCCP-induced mild mitochondrial uncoupling. 相似文献
38.
39.
40.