全文获取类型
收费全文 | 2025篇 |
免费 | 213篇 |
专业分类
2238篇 |
出版年
2022年 | 25篇 |
2021年 | 46篇 |
2020年 | 17篇 |
2019年 | 26篇 |
2018年 | 36篇 |
2017年 | 29篇 |
2016年 | 48篇 |
2015年 | 65篇 |
2014年 | 76篇 |
2013年 | 109篇 |
2012年 | 158篇 |
2011年 | 138篇 |
2010年 | 96篇 |
2009年 | 83篇 |
2008年 | 102篇 |
2007年 | 128篇 |
2006年 | 105篇 |
2005年 | 116篇 |
2004年 | 109篇 |
2003年 | 86篇 |
2002年 | 92篇 |
2001年 | 28篇 |
2000年 | 26篇 |
1999年 | 25篇 |
1998年 | 17篇 |
1997年 | 21篇 |
1996年 | 18篇 |
1995年 | 18篇 |
1994年 | 12篇 |
1992年 | 31篇 |
1991年 | 22篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 15篇 |
1987年 | 17篇 |
1986年 | 17篇 |
1985年 | 10篇 |
1984年 | 18篇 |
1983年 | 19篇 |
1982年 | 12篇 |
1981年 | 15篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1975年 | 9篇 |
1974年 | 19篇 |
1973年 | 13篇 |
1971年 | 14篇 |
1968年 | 10篇 |
排序方式: 共有2238条查询结果,搜索用时 15 毫秒
1.
Jeff A Johnson Heather RL Lerner Pamela C Rasmussen David P Mindell 《BMC evolutionary biology》2006,6(1):65-12
Background
Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis. 相似文献2.
Olga Maslova Oleg Fedevych Nadiia Shuvalova Olena Deryabina Volodymyr Zhovnir Miroslav Novak Peter Kruzliak 《Cell and tissue banking》2016,17(2):335-339
The need for selection of the optimal material for the manufacturing of cardio-patches can be resolved by the use of cryostored autologous pericardial tissue. This short communication is a concise fragment of a large-scale research and demonstrates only the efficiency of cell culturing before and after pericardial preservation in the low temperature conditions. 相似文献
3.
4.
Human globin genes can be transferred into mouse and human erythroid cells in culture, and can be appropriately expressed at the mRNA level in these cells. A plasmid containing a human beta globin gene is expressed in mouse erythroleukemia cells (MELC), and another containing a human epsilon or gamma gene is expressed in human erythroleukemia (K562) cells. A neomycin resistance (neoR) gene on the plasmids has been used to select for those cells containing the transferred globin genes; this selection may favor the expression of the globin genes by providing chromosomal positions requiring neoR expression. Analyzing clones resistant to G418, a neomycin analogue, demonstrated globin mRNA expression and induction. Retroviral vectors have also been used to transfer and appropriately express human beta genes in MELC. In addition, a plasmid containing a dihydrofolate reductase (DHFR) gene as well as neoR and beta globin genes has been used to amplify and express beta globin mRNA in MELC. These experiments suggest that high level appropriate expression of human beta globin genes is feasible and provides potentially useful approaches to the long-range goal of gene therapy for sickle cell anemia and beta thalassemia. 相似文献
5.
6.
Electron microscopic observations of epidermal and cortical cells of the root tips of barley (Hordeum vulgare L.) grown in 192 mm NaCl and aged in 192 mm NaCl + 0.2 mm CaSO4 revealed marked condensation of chromatin in the nuclei which was not observed in freshly cut tissue grown in the presence of 192 mM NaCl. Other changes due to salinity were observed, such as the increase of the number of ribosomes and of mitochondria and the appearance of translucent areas in slightly swollen mitochondria. The mechanism by which the nuclear changes occurred or their meaning for cell function are not understood. 相似文献
7.
Ricardo Gonzalez-Mendez David Wemmer George Hahn Norma Wade-Jardetzky Oleg Jardetzky 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1982,720(3):274-280
A continuous-flow NMR culture system for mammalian cells has been developed on which 31P-NMR experiments under complete and strictly physiologic conditions have been performed. Observations on the response of the cellular metabolism to stresses such as starvation, low temperature and changes in environmental pH monitored by 31P-NMR are reported. The response of the intracellular pH relative to the external pH of the growth medium is studied. We find that under the experimental conditions used there exists a ΔpH varying between less than 0.2 and more than 0.6 pH units. These results are compatible with those obtained using other techniques. 相似文献
8.
9.
Adaptation to salinity at the plant cell level 总被引:3,自引:0,他引:3
H. R. Lerner 《Plant and Soil》1985,89(1-3):3-14
Summary Various mechanisms of adaptation of plant cells to salinity are reviewed: (1) protection of enzymes and maintenance of turgor by organic solutes; (2) prevention of ion toxicity by compartmentation; and (3) energization of solute transport by the proton pump. All these mechanisms seem to play a role in adaptation. The particular advantages of using salt-adapted cells in suspension culture to identify mechanisms of adaptation are pointed out. 相似文献
10.
J Tyedmers M Kruse M Lerner J Demand J H?hfeld J Solsbacher J Volkmer R Zimmermann 《European journal of biochemistry》2000,267(12):3575-3582
Heterodimeric luciferase from Vibrio harveyi had been established as a unique model enzyme for direct measurements of the effects of molecular chaperones and folding catalysts on protein folding and subunit assembly after de novo synthesis of subunits in rabbit reticulocyte lysate. It was observed that luciferase assembly can be separated in time from synthesis of the two subunits and that under these post-translational conditions assembly was inhibited by either ATP depletion or inhibition of peptidylprolyl cis/trans isomerases, that is, by addition of cyclosporin A or FK506. Furthermore, it was observed that the inhibitory effect of FK506 on luciferase assembly can be suppressed by addition of purified cyclophilin, thereby providing the first direct evidence for the involvement of peptidylprolyl cis/trans isomerases in protein biogenesis in the eukaryotic cytosol. Here the ATP requirement in luciferase assembly has been characterized. Depletion of either Hsp90 or CCT from reticulocyte lysate did not interfere with luciferase assembly. However, addition of purified Hsc70 stimulated luciferase assembly. While addition of purified Hsp40 did not have any effect on luciferase assembly, the stimulatory effect of Hsc70 was further increased by Hsp40. Thus, after synthesis of the two subunits in reticulocyte lysate assembly of heterodimeric luciferase involves Hsc70 and its co-chaperone Hsp40. Therefore, Hsc70 aids protein biogenesis in the eukaryotic cytosol not only at the levels of nascent polypeptide chains and precursor proteins that have to be kept competent for transport into cell organelles, but also at the level of subunits that have to be kept competent for assembly. 相似文献