全文获取类型
收费全文 | 63143篇 |
免费 | 5416篇 |
国内免费 | 17篇 |
出版年
2023年 | 317篇 |
2022年 | 388篇 |
2021年 | 871篇 |
2020年 | 550篇 |
2019年 | 648篇 |
2018年 | 1296篇 |
2017年 | 1230篇 |
2016年 | 1509篇 |
2015年 | 1736篇 |
2014年 | 1925篇 |
2013年 | 3092篇 |
2012年 | 4487篇 |
2011年 | 4825篇 |
2010年 | 2621篇 |
2009年 | 1884篇 |
2008年 | 3918篇 |
2007年 | 3974篇 |
2006年 | 3668篇 |
2005年 | 3334篇 |
2004年 | 3129篇 |
2003年 | 2941篇 |
2002年 | 2898篇 |
2001年 | 1666篇 |
2000年 | 1881篇 |
1999年 | 1081篇 |
1998年 | 581篇 |
1997年 | 482篇 |
1996年 | 523篇 |
1995年 | 458篇 |
1994年 | 485篇 |
1993年 | 444篇 |
1992年 | 468篇 |
1991年 | 401篇 |
1990年 | 359篇 |
1989年 | 327篇 |
1988年 | 325篇 |
1987年 | 312篇 |
1986年 | 270篇 |
1985年 | 387篇 |
1984年 | 461篇 |
1983年 | 390篇 |
1982年 | 384篇 |
1981年 | 362篇 |
1980年 | 324篇 |
1979年 | 335篇 |
1978年 | 311篇 |
1977年 | 297篇 |
1976年 | 307篇 |
1975年 | 354篇 |
1974年 | 260篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
41.
42.
Comparative analysis of the cattle and human genomes: detection of ZOO-FISH and gene mapping-based chromosomal homologies 总被引:6,自引:0,他引:6
Comparative chromosome painting with individual human chromosome-specific libraries (CSLs) on cattle metaphase chromosomes
delineated 46 homologous chromosomal segments between the two species. Continuous arrangement of these segments on individual
cattle chromosomes demonstrates a nearly complete coverage of the bovine karyotype and shows physical boundaries of bovine
chromosomal segments homologous to individual human chromosomes. Alignment of the available comparative gene mapping data
with the homologous segments strongly supports the detected gross homologies between the karyotypes of the two species. In
addition to cattle, four human CSLs were hybridized to sheep metaphase chromosomes also, to further verify the known karyotype
homology within the Bovidae. Besides its application to karyotype evolution research, the comparative knowledge provides for
rapid expansion of the much needed Type I locus-based bovine gene map.
Received: 9 September 1995 / Accepted: 4 December 1995 相似文献
43.
44.
Fazile Nur Ekinci Akdemir Berna Karagöz Recep Soslu Saleh H. Alwasel 《Journal of enzyme inhibition and medicinal chemistry》2016,31(6):114-118
AbstractThe antioxidant effects of ellagic acid (EA) and hesperidin (HES) against skeletal muscle ischemia/reperfusion injury (I/R) were performed. Hindlimb ischemia has been induced by tourniquet occlusion for 2?h on left hindlimb. At the end of ischemia, the tourniquate has been removed and initiated reperfusion for 2?h. EA (100?mg/kg) has been applied orally before ischemia/reperfusion in the EA?+?I/R group. HES (100?mg/kg) has been given orally in the HES?+?I/R group. The left gastrocnemius muscle has been harvested and stored immediately at??80?°C until assessed for the levels of MDA and antioxidant enzymes activities. MDA level has statistically increased in I/R group (p?<?0.05) compared to other groups. The muscle tissue antioxidant enzymes activities were lower than the other groups in the I/R group (p?<?0.05). EA and HES treatments significantly reversed the damage level in I/R, also activity of tissue SOD increased in the EA?+?I/R and HES?+?I/R groups. 相似文献
45.
46.
Se-Chan Kim Alexander Ghanem Heidi Stapel Klaus Tiemann Pascal Knuefermann Andreas Hoeft Rainer Meyer Christian Grohé Anne A Knowlton Georg Baumgarten 《BMC physiology》2007,7(1):5
Backgound
It has been reported that Toll-like receptor 4 (TLR4) deficiency reduces infarct size after myocardial ischemia/reperfusion (MI/R). However, measurement of MI/R injury was limited and did not include cardiac function. In a chronic closed-chest model we assessed whether cardiac function is preserved in TLR4-deficient mice (C3H/HeJ) following MI/R, and whether myocardial and systemic cytokine expression differed compared to wild type (WT). 相似文献47.
48.
Rasika Sunnadeniya Alexander Bean Matthew Brown Neda Akhavan Gregory Hatlestad Antonio Gonzalez V. Vaughan Symonds Alan Lloyd 《PloS one》2016,11(2)
Yellow and red-violet betalain plant pigments are restricted to several families in the order Caryophyllales, where betacyanins play analogous biological roles to anthocyanins. The initial step in betalain biosynthesis is the hydroxylation of tyrosine to form L-DOPA. Using gene expression experiments in beets, yeast, and Arabidopsis, along with HPLC/MS analysis, the present study shows that two novel cytochrome P450 (CYP450) enzymes, CYP76AD6 and CYP76AD5, and the previously described CYP76AD1 can perform this initial step. Co-expressing these CYP450s with DOPA 4,5-dioxygenase in yeast, and overexpression of these CYP450s in yellow beets show that CYP76AD1 efficiently uses L-DOPA leading to red betacyanins while CYP76AD6 and CYP76AD5 lack this activity. Furthermore, CYP76AD1 can complement yellow beetroots to red while CYP76AD6 and CYP76AD5 cannot. Therefore CYP76AD1 uniquely performs the beet R locus function and beets appear to be genetically redundant for tyrosine hydroxylation. These new functional data and ancestral character state reconstructions indicate that tyrosine hydroxylation alone was the most likely ancestral function of the CYP76AD alpha and beta groups and the ability to convert L-DOPA to cyclo-DOPA evolved later in the alpha group. 相似文献
49.
Ohne ZusammenfassungProceedings of the Meetings of Saturday September 26, 1908.Die vorliegende Übersetzung, zu der Herr Prof. Went mich gütigst autorisierte, rechtfertigt sich durch die in theoretischer, ganz besonders aber in methodologischer Hinsicht überaus wichtigen Ergebnisse Blaauws. Die Untersuchung bestätigt zunächst ein Gesetz, das der Übersetzer für die Abhängigkeit der Präsentationszeit von der Lichtintensität festgestellt hat (die diesbezügliche Abhandlung war Herrn Prof. Went zur Zeit, als er dieses Referat schrieb, noch nicht zu Gesicht gekommen), verfolgt aber diese Gesetzmäßigkeit innerhalb wesentlich weiterer Grenzen. Die Feststellung ganz besonders, daß bei entsprechend intensiver Beleuchtung die Präsentationszeit bis auf 1/1000 Sekunde sinkt, zusammengehalten mit den Tatsachen der feinen Unterschiedsempfind-lichkeit der Pflanzen (Wiesner) und der außerordentlich kurzen Perzeptions-zeit (Fitting), muß die reizphysiologische Methodik reformieren und sie zu ebenso exaktem Arbeiten anspornen, wie es bei psychophysischen Experimenten längst der Fall ist. 相似文献
50.