全文获取类型
收费全文 | 2843篇 |
免费 | 145篇 |
出版年
2023年 | 14篇 |
2022年 | 38篇 |
2021年 | 74篇 |
2020年 | 48篇 |
2019年 | 43篇 |
2018年 | 65篇 |
2017年 | 61篇 |
2016年 | 74篇 |
2015年 | 76篇 |
2014年 | 128篇 |
2013年 | 159篇 |
2012年 | 215篇 |
2011年 | 179篇 |
2010年 | 117篇 |
2009年 | 111篇 |
2008年 | 143篇 |
2007年 | 137篇 |
2006年 | 105篇 |
2005年 | 104篇 |
2004年 | 93篇 |
2003年 | 79篇 |
2002年 | 86篇 |
2001年 | 74篇 |
2000年 | 75篇 |
1999年 | 54篇 |
1998年 | 20篇 |
1997年 | 16篇 |
1996年 | 33篇 |
1995年 | 18篇 |
1994年 | 18篇 |
1993年 | 18篇 |
1992年 | 48篇 |
1991年 | 33篇 |
1990年 | 26篇 |
1989年 | 33篇 |
1988年 | 25篇 |
1987年 | 28篇 |
1986年 | 18篇 |
1985年 | 31篇 |
1984年 | 25篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 22篇 |
1979年 | 26篇 |
1978年 | 27篇 |
1977年 | 17篇 |
1975年 | 12篇 |
1974年 | 13篇 |
1973年 | 17篇 |
1972年 | 13篇 |
排序方式: 共有2988条查询结果,搜索用时 15 毫秒
121.
122.
Vivek Khanna Manish Jain Vishal Singh Jitendra S. Kanshana Prem Prakash Manoj K. Barthwal Puvvada S. R. Murthy Madhu Dikshit 《PloS one》2013,8(10)
Effect of long term cholesterol diet withdrawal on accelerated atherosclerosis in iliac artery of New Zealand White (NZW) rabbits has not been explored so far. Atherosclerosis was thus induced in rabbits by a combination of balloon injury and atherogenic diet (AD) (1% cholesterol and 6% peanut oil) feeding for 8 weeks (baseline) followed by chow diet (CD) feeding for 4, 8, 16, 32, 50 and 64 weeks. The plaque characterization was done using histology, real time RT-PCR and vasoreactivity studies. Significant elevation in plasma lipids with AD feeding was normalized following 16 weeks of CD feeding. However, baseline comparison showed advanced plaque features even after 8 weeks of CD period with significant elevation in intima/media thickness ratio and plaque area later showing reduction at 50 and 64 weeks CD periods. Lesion lipid accumulation and CD68 positivity was maintained till 16 weeks of CD feeding which significantly reduced from 32 to 64 weeks CD periods. Baseline comparison showed significant increase in ground substance, MMP-9 and significant decrease in α-actin and collagen content at 8 weeks CD period indicating features of unstable plaque. These features regressed up to 64 weeks of CD. Partial restoration of functional vasoconstriction and vasorelaxation was seen after 64 weeks of CD feeding. mRNA expression of MCP-1, VCAM-1, collagen type I and III, MMP-9, TIMP-1, IFN-γ, TNF-α, IL-10 and eNOS supported the above findings. The study thus reveals insights into initial plaque instability and subsequent regression on AD withdrawal in this model. These results are suggestive of an appropriate window for drug intervention for plaque stability/regression and restenosis as well as improves understanding of plaque regression phenomenon in this model. 相似文献
123.
Taste buds are composed of a variety of taste receptor cell types that develop from tongue epithelium and are regularly replenished under normal homeostatic conditions as well as after injury. The characteristics of cells that give rise to regenerating taste buds are poorly understood. Recent studies have suggested that Lgr5 (leucine-rich repeat-containing G-protein coupled receptor 5) identifies taste bud stem cells that contribute to homeostatic regeneration in adult circumvallate and foliate taste papillae, which are located in the posterior region of the tongue. Taste papillae in the adult anterior region of the tongue do not express Lgr5. Here, we confirm and extend these studies by demonstrating that Lgr5 cells give rise to both anterior and posterior taste buds during development, and are capable of regenerating posterior taste buds after injury induced by glossopharyngeal nerve transection. 相似文献
124.
125.
Anukool Vaishnav Shekhar Jain Amrita Kasotia Sarita Kumari Rajarshi Kumar Gaur Devendra Kumar Choudhary 《Archives of microbiology》2013,195(8):571-577
To understand protective roles of nitric oxide against salt stress, the effects of exogenous sodium nitroprusside on activities of lipoxygenase, peroxidase, phenylalanine ammonialyase, catalase, superoxide dismutase enzymes, proline accumulation, and distribution of sodium in soybean plants under salt were determined. Application of sodium nitroprusside + bacterium enhanced plant growth-promotion characteristics, activities of different enzymes, and proline accumulation in the presence of sodium nitroprusside under salt stress. Treatment with NaCl at 200 mM and sodium nitroprusside (0.1 mM) reduced Na+ levels but increased K+ levels in leaves in comparison with the NaCl-treated plants. Correspondingly, the plants treated with exogenous sodium nitroprusside and NaCl maintained a lower ratio of [Na+]/[K+] in NaCl-stressed plants. 相似文献
126.
A role for HflX in 50S-biogenesis was suggested based on its similarity to other GTPases involved in this process. It possesses a G-domain, flanked by uncharacterized N- and C-terminal domains. Intriguingly, Escherichia coli HflX was shown to hydrolyze both GTP and adenosine triphosphate (ATP), and it was unclear whether G-domain alone would explain ATP hydrolysis too. Here, based on structural bioinformatics analysis, we suspected the possible existence of an additional nucleotide-binding domain (ND1) at the N-terminus. Biochemical studies affirm that this domain is capable of hydrolyzing ATP and GTP. Surprisingly, not only ND1 but also the G-domain (ND2) can hydrolyze GTP and ATP too. Further; we recognize that ND1 and ND2 influence each other’s hydrolysis activities via two salt bridges, i.e. E29-R257 and Q28-N207. It appears that the salt bridges are important in clamping the two NTPase domains together; disrupting these unfastens ND1 and ND2 and invokes domain movements. Kinetic studies suggest an important but complex regulation of the hydrolysis activities of ND1 and ND2. Overall, we identify, two separate nucleotide-binding domains possessing both ATP and GTP hydrolysis activities, coupled with an intricate inter-domain regulation for Escherichia coli HflX. 相似文献
127.
Phosphatidylinositol-3,4,5-triphosphate (PIP3) and phosphatidylinositol-4,5-biphosphate (PIP2) are two well-known membrane bound polyphosphoinositides. Diabetes is associated with impaired glucose metabolism. Using a 3T3L1 adipocyte cell model, this study investigated the role of PIP3 and PIP2 on insulin stimulated glucose metabolism in high glucose (HG) treated cells. Exogenous PIP3 supplementation (1, 5, or 10 nM) increased the phosphorylation of AKT and PKCζ/λ, which in turn upregulated GLUT4 total protein expression as well as its surface expression, glucose uptake, and glucose utilization in cells exposed to HG (25 mM); however, PIP2 had no effect. Comparative signal silencing studies with antisense AKT2 and antisense PKCζ revealed that phosphorylation of PKCζ/λ is more effective in PIP3 mediated GLUT4 activation and glucose utilization than in AKT phosphorylation. Supplementation with PIP3 in combination with insulin enhanced glucose uptake and glucose utilization compared to PIP2 with insulin, or insulin alone, in HG-treated adipocytes. This suggests that a decrease in cellular PIP3 levels may cause impaired insulin sensitivity in diabetes. PIP3 supplementation also prevented HG-induced MCP-1 and resistin secretion and lowered adiponectin levels. This study for the first time demonstrates that PIP3 but not PIP2 plays an important role in GLUT4 upregulation and glucose metabolism mediated by AKT/PKCζ/λ phosphorylation. Whether PIP3 levels in blood can be used as a biomarker of insulin resistance in diabetes needs further investigation. 相似文献
128.
129.
Abstract The effect of 2, 4-dinitrophenol (DNP) on the extracelluar polysaccharides (EPS), cell surface charge, and the hydrophobicity of six marine bacterial cultures was studied, and its influence on attachment of these bacteria to glass and polystyrene was evaluated. DNP treatment did not influence cell surface charge and EPS production, but had a significant effect on hydrophobicity of both hydrophilic (p = 0.05) and hydrophobic (p = 0.01) cultures. Significant reduction in the attachment of all the six cultures to glass (p = 0.02) and polystyrene (p = 0.03) was observed after DNP treatment. Moreover, hydrophobicity but not the cell surface charge or EPS production influenced bacterial cell attachment to glass and polystyrene. From this study, it was evident that DNP treatment influenced bacterial cell surface hydrophobicity, which in turn, reduced bacterial adhesion to surfaces. 相似文献
130.