全文获取类型
收费全文 | 7271篇 |
免费 | 439篇 |
国内免费 | 9篇 |
出版年
2023年 | 20篇 |
2022年 | 62篇 |
2021年 | 130篇 |
2020年 | 76篇 |
2019年 | 111篇 |
2018年 | 165篇 |
2017年 | 143篇 |
2016年 | 165篇 |
2015年 | 281篇 |
2014年 | 290篇 |
2013年 | 426篇 |
2012年 | 512篇 |
2011年 | 570篇 |
2010年 | 331篇 |
2009年 | 302篇 |
2008年 | 481篇 |
2007年 | 471篇 |
2006年 | 456篇 |
2005年 | 395篇 |
2004年 | 387篇 |
2003年 | 356篇 |
2002年 | 353篇 |
2001年 | 90篇 |
2000年 | 66篇 |
1999年 | 95篇 |
1998年 | 103篇 |
1997年 | 34篇 |
1996年 | 53篇 |
1995年 | 39篇 |
1994年 | 38篇 |
1993年 | 33篇 |
1992年 | 55篇 |
1991年 | 49篇 |
1990年 | 57篇 |
1989年 | 36篇 |
1988年 | 33篇 |
1987年 | 26篇 |
1986年 | 27篇 |
1985年 | 36篇 |
1984年 | 28篇 |
1983年 | 19篇 |
1982年 | 31篇 |
1981年 | 18篇 |
1979年 | 21篇 |
1978年 | 18篇 |
1975年 | 26篇 |
1974年 | 22篇 |
1973年 | 16篇 |
1971年 | 16篇 |
1967年 | 17篇 |
排序方式: 共有7719条查询结果,搜索用时 15 毫秒
71.
Junqi Liu Jin Zhang Narasimha M. Beeraka Kuo Chen Mikhail Y. Sinelnikov Prasath Manogaran Gurupadayya Bannimath Vladimir N. Nikolenko Ruitai Fan 《Pigment cell & melanoma research》2023,36(3-4):268-287
Several research reports delineated the significant role of miRNAs in cancer proliferation, and their modulatory role in cancer mitigation, and drug resistance. Melanoma cells have been acquiring stemness to several chemotherapeutic agents through drug efflux proteins, epigenetic modulation, and DNA repair. miRNAs could be applied as novel therapeutic modalities for treating several kinds of cancers to modulate these mechanisms involved in stemness. Nanocarriers to carry these tumor-targeting miRNAs to modulate stemness are a prominent strategy to overcome their low penetrability, minimal stability, and nonspecificity. We have searched several public databases such as PubMed, Medline, Google scholar, and NLM and obtained the information pertinent to the miRNA-based nanocarrier systems to target stemness through epigenetic modulation in melanomas. This review delineates that various miRNAs can modulate the stemness in melanomas by specific intricate epigenetic signaling, and other cell-based signaling mechanisms. Specific nanocarrier formulations with specific miRNAs are optimal methods to deliver these miRNAs in order to achieve significant entrapment efficiency, loading efficiency, and stability. Furthermore, the combinatorial regimen of FDA-approved chemotherapeutic molecules with tumor-targeting miRNAs and chemotherapy combined with nanocarriers can efficiently deliver the utmost therapeutic window by targeting tumor matrix, invasion, metastasis, and angiogenesis in melanomas. Substantial research should focus on the clinical application of this gene therapy in melanomas using these low immunogenic, highly degradable, and biocompatible combinatorial nanotherapeutic regimens. 相似文献
72.
Marina S. Trofimova Inna M. Zhestkova Valentina P. Kholodova Igor M. Andreev Evgeny M. Sorokin Anna G. Kruglova Vladimir V. Kuznetsov 《Physiologia plantarum》2003,118(2):232-239
The osmotic water permeability ( P os ) of cell membranes isolated from leaves of 40-, 50- and 60-day-old Mesembryanthemum crystallinum plants was estimated by measuring light-scattering kinetics using stopped-flow spectrophotometry. The measurements were performed on the plasma membrane (PM), purified tonoplast (TP), and TP-enriched vesicles. The PM and TP-enriched vesicles were obtained by partitioning the microsomal fraction in an aqueous polymer two-phase system, whereas the purified TP vesicles were prepared by microsomal vesicle flotation on a sucrose cushion. The P os of isolated membranes declined with plant age. The kinetic experiments showed that there was no difference between the P os of the PM and TP isolated from plants of all ages. A 24-h exposure of plants to 400 m M NaCl caused a decline in the P os as well. These findings suggest that, during M. crystallinum transition to CAM, which was induced by plant ageing or salinity, plant osmoregulatory responses included changes in the P os of the leaf-cell membranes. These variations in the P os are discussed in the context of adaptive mechanisms responsible for the maintenance of the water balance in the common ice plant. 相似文献
73.
The sialic acid content of electronegative low density lipoprotein (LDL) and LDL isolated from human aortic intima was measured. Sialic acid level in electronegative LDL of healthy subjects was 1.7-fold lower than in native LDL. Sialic acid content in electronegative LDL of coronary atherosclerosis patients was 3-fold lower than in native LDL. Lipoproteins isolated from grossly normal human aortic intima and from fatty streaks contained 20-56% less sialic acid as compared to blood plasma LDL. A negative correlation was established between the ability of electronegative and aortic LDL to stimulate lipid accumulation in cells cultured from uninvolved human aortic intima and lipoprotein sialic acid content. The results obtained indicate that electronegative and aortic LDLs have a low sialic acid content, i.e., are desialylated lipoproteins. Considered together with the fact that all known atherogenic LDLs have similar characteristics, our findings suggest that modified LDLs are the same lipoprotein particles subjected to multiple modification. 相似文献
74.
Summary
Azotobacter chroococcum was grown in continuous culture at two temperatures (30 °C and 20 °C) and different dissolved oxygen tensions (DOT) (30 % to 40 % and 70 % to 80 % of air saturation), respectively. At the temperature of 30 °C and low DOT a relatively high volumetric productivity and efficiency of nitrogen fixation were obtained. After lowering the temperature to 20 °C, an intensive formation of cysts was observed associated with a drastic decrease of the bacterial growth. Bacteria in the form of cysts kept their physiological activity for a long period of time depending on temperature and preparation. 相似文献
75.
Jonathan H. Davis David A. Agard Tracy M. Handel Vladimir J. Basus 《Journal of biomolecular NMR》1997,10(1):21-27
-Lytic protease, a bacterial serine protease of 198 aminoacids (19800 Da), has been used as a model system for studies of catalyticmechanism, structure–function relationships, and more recently forstudies of pro region-assisted protein folding. We have assigned thebackbones of the enzyme alone, and of its complex with the tetrahedraltransition state mimic N-tert-butyloxycarbonyl-Ala-Pro-boroVal, usingdouble- and triple-resonance 3D NMR spectroscopy on uniformly15N- and 13C/15N-labeled protein.Changes in backbone chemical shifts between the uncomplexed and inhibitedform of the protein are correlated with distance from the inhibitor, thedisplacement of backbone nitrogens, and change in hydrogen bond strengthupon inhibitor binding (derived from previously solved crystal structures).A comparison of the solution secondary structure of the uninhibited enzymewith that of the X-ray structure reveals no significant differences.Significant line broadening, indicating intermediate chemical exchange, wasobserved in many of the active site amides (including three broadened toinvisibility), and in a majority of cases the broadening was reversed uponaddition of the inhibitor. Implications and possible mechanisms of this linebroadening are discussed. 相似文献
76.
G. V. Mukamolova N. D. Yanopolskaya T. V. Votyakova V. I. Popov A. S. Kaprelyants D. B. Kell 《Archives of microbiology》1995,163(5):373-379
Changes in the biochemical properties of Micrococcus luteus cells were studied during the transition to a dormant state after incubation in an extended stationary phase. The overall DNA content after 150 days of starvation was similar to its initial level, while the RNA content decreased by 50%. Total lipids and protein, phospholipids and membrane proteins declined rapidly within the first 1–10 days of starvation. After 180 days of starvation, cells contained 43% of the protein and 35% of the lipid initially present. Starvation for 120 days resulted in the loss of phosphatidylglycerol and, to some extent, of phosphatidylinositol, giving a membrane whose phospholipids consisted mainly of cardiolipin. The membrane fluidity declined during starvation, as judged by diphenyl hexatriene fluorescence anisotropy measurements. Oxidase activities declined to zero within the first 20–30 days of starvation, while the dehydrogenases and cytochromes were more stable. The activities of some cytoplasmic enzymes were lost very rapidly, while NADPH-linked isocitrate dehydrogenase had 30% of its initial activity after 120 days of starvation. For all parameters tested there were significant fluctuations during the first 10–20 days of starvation, which may reflect cryptic growth in the culture.Abbreviations
MPN
Most probable number
-
DPH
Diphenyl hexatriene 相似文献
77.
78.
Peter A. Nickerson Mirjana Hristić Prof. Dr. Vladimir Pantić 《Cell and tissue research》1978,189(2):277-286
Maternal adrenalectomy at 7 or 14 days of gestation produced increased cell necrosis within zona reticularis cells on the day of birth and at 24 or 48 h after birth. Small remnants or large portions of adrenocortical cells were present within macrophages. In otherwise normal adrenocortical cells, lipid droplets were incorporated within some mitochondria. Autophagocytosis of single mitochondria was observed within adrenocortical cells. Undoubtedly ultrastructural changes represent stimulation of adrenocortical cells in neonatal rats in response to maternal adrenalectomy. 相似文献
79.
80.
Cloning of bacteriophage T5 promoters 总被引:3,自引:0,他引:3
Vladimir N. Ksenzenko Tatjana P. Kamynina Nina M. Pustoshilova Valentine M. Kryukov A. A. Bayev 《Molecular & general genetics : MGG》1982,185(3):520-522
Summary Bacteriophage T5 was subjected to combined hydrolysis with the restriction endonuclease PstI and HindIII and the resulting fragments were inserted into the plasmid pBR322. Selection of transformants for Aps-Tcr-phenotype made it possible to screen the hybrid plasmids that contained promoter sequences in the cloned fragments.Two PstI/HindIII fragment, 720 bp (51% of the T5 DNA length) and 1,200 bp (70%) were cloned in this study. Tcr levels for these plasmids were as high as 18 g/ml and 75 g/ml, respectively. The presence of Escherichia coli RNA polymerase binding sites on both fragments was shown using the nitrocellulose filter assay. These binding sites are situated between 35 bp and 95 bp from the HindIII cleavage site on the 1,200 bp fragment; and within 420 bp from the HindIII site on the 720 bp fragment.Abbreviations Ap
ampicillin
- Tc
tetracycline
- bp
base pairs
- NTPs
nucleoside triphosphates
- PBB
polymerase binding buffer 相似文献