全文获取类型
收费全文 | 401篇 |
免费 | 13篇 |
专业分类
414篇 |
出版年
2022年 | 8篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 8篇 |
2016年 | 11篇 |
2015年 | 16篇 |
2014年 | 28篇 |
2013年 | 30篇 |
2012年 | 21篇 |
2011年 | 14篇 |
2010年 | 17篇 |
2009年 | 15篇 |
2008年 | 9篇 |
2007年 | 18篇 |
2006年 | 13篇 |
2005年 | 11篇 |
2004年 | 10篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 12篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1992年 | 12篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1971年 | 5篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有414条查询结果,搜索用时 15 毫秒
41.
Dhillon H Ge Y Minter RM Prima V Moldawer LL Muzyczka N Zolotukhin S Kalra PS Kalra SP 《Regulatory peptides》2000,92(1-3):97-105
42.
Auxin-calcium interaction has been studied to understand their involvement in adventitious root initiation from the hypocotyl explants of sunflower (Helianthus annuus L.). When hypocotyl explants were cultured on MS medium (containing calcium), 1 mg l-1 IAA was found to be optimal for root induction. However, the hypocotyl explants washed in EGTA (10-5M) solution for the removal of extracellular calcium, when cultured on medium containing IAA and calcium, exhibited enhanced rooting response. When EGTA-washed explants were cultured on the medium supplemented with lanthanum chloride (10-6 and 10-5M), it resulted in the inhibition of the rooting response and this inhibitory effect could be alleviated by the simultaneous addition of IAA. Similar observations have been made by using calcium channel blockers, verapamil and TMB-8, and also a calmodulin inhibitor, trifluoperazine. A net influx of extracellular calcium in the differentiating cells is thus presumed to accompany the auxin-induced response. These results have been discussed in light of initial lack of polarity in the decapitated hypocotyl segments subjected to auxin treatment. 相似文献
43.
Palwinder Singh Jatinder Kaur Bhawna Yadav Sneha Sudha Komath 《Bioorganic & medicinal chemistry》2009,17(11):3973-3979
In order to search for MDR modulators, rationally designed acridone derivatives were investigated for their effect on influx or efflux of Rhodamine6G (R6G) in CAI4 cells. Results of these investigations indicate that in presence of compound 12, inhibition of growth of CAI4 cells and also an increased influx/efflux of R6G in CAI4 cells have been observed. This seems to be occurring due to the cell wall rupturing of Candida albicans. Compound 12 may be a suitable candidate for candidiasis therapy. 相似文献
44.
Goutham Mylavarapu Shanmugam Murugappan Mihai Mihaescu Maninder Kalra Sid Khosla Ephraim Gutmark 《Journal of biomechanics》2009,42(10):1553-1559
An anatomically accurate human upper airway model was constructed from multiple magnetic resonance imaging axial scans. This model was used to conduct detailed Computational Fluid Dynamics (CFD) simulations during expiration, to investigate the fluid flow in the airway regions where obstruction could occur. An identical physical model of the same airway was built using stereo lithography. Pressure and velocity measurements were conducted in the physical model. Both simulations and experiments were performed at a peak expiratory flow rate of 200 L/min. Several different numerical approaches within the FLUENT commercial software framework were used in the simulations; unsteady Large Eddy Simulation (LES), steady Reynolds-Averaged Navier-Stokes (RANS) with two-equation turbulence models (i.e. k?ε, standard k?ω, and k?ω Shear Stress Transport (SST)) and with one-equation Spalart–Allmaras model. The CFD predictions of the average wall static pressures at different locations along the airway wall were favorably compared with the experimental data. Among all the approaches, standard k?ω turbulence model resulted in the best agreement with the static pressure measurements, with an average error of ~20% over all ports. The highest positive pressures were observed in the retroglossal regions below the epiglottis, while the lowest negative pressures were recorded in the retropalatal region. The latter is a result of the airflow acceleration in the narrow retropalatal region. The largest pressure drop was observed at the tip of the soft palate. This location has the smallest cross section of the airway. The good agreement between the computations and the experimental results suggest that CFD simulations can be used to accurately compute aerodynamic flow characteristics of the upper airway. 相似文献
45.
46.
We investigated the role of cuticular lipids, body melanisation and body size in conferring contrasting levels of desiccation
resistance in latitudinal populations of Drosophila melanogaster and Drosophila ananassae on the Indian subcontinent. Contrary to the well known role of cuticular lipids in water proofing in diverse insect taxa,
there is lack of geographical variations in the amount of cuticular lipids per fly in both the species. In D. ananassae, quite low levels of body melanisation are correlated with lower desiccation resistance. By contrast, increased levels of
desiccation resistance are correlated with quite high melanisation in D. melanogaster. Thus, species specific cuticular melanisation patterns are significantly correlated with varying levels of desiccation resistance
within as well as between populations and across species. Role of body melanisation in desiccation resistance is further supported
by the fact that assorted dark and light flies differ significantly in cuticular water loss, hemolymph and dehydration tolerance.
However, similar patterns of body size variation do not account for contrasting levels of desiccation resistance in these
two Drosophila species. Climatic selection is evidenced by multiple regression analysis with seasonal amplitude of thermal and humidity
changes (Tcv and RHcv) along latitude on the Indian subcontinent. Finally, the contrasting levels of species specific distribution
patterns are negatively correlated with RHcv of sites of origin of populations i.e. a steeper negative slope for D. ananassae corresponds with its desiccation sensitivity as compared with D. melanogaster. Thus, evolutionary changes in body melanisation impact desiccation resistance potential as well as distribution patterns
of these two Drosophila species on the Indian subcontinent. 相似文献
47.
Thermotolerance traits vary across geographical gradients but there is a lack of clinal variation in some Drosophila species. Thus, it is not clear whether thermotolerance or other correlated traits are the target of natural selection. In order to test selection responses, we investigated body melanization and thermotolerance traits in six altitudinal populations of Drosophila melanogaster . Based on rearing different geographical populations under uniform growth conditions at 21 °C (common garden experiments), clinal variations for cold resistance are in the direction opposite to heat resistance along an altitudinal gradient, that is darker flies from highland populations evidenced higher levels of cold resistance while lowland populations showed higher heat resistance. Phenotypic plastic responses for body melanization at 17–28 °C showed significant correlations with thermotolerance traits. At 17 °C, regression coefficients as a function of altitude are highly significant and positive for cold resistance but negative for heat knockdown. However, for flies reared at 28 °C, there is no elevational change in melanization as well as thermotolerance traits. Thus, both genetic and plastic changes of body melanization and thermotolerance traits suggest a correlated selection response. Further, within-population analyses of body melanization (based on dark, intermediate and light color phenotypes) showed significant associations with thermotolerance traits. Correlated variations in body melanization and thermal tolerances are associated with climatic thermal variability ( T cv ) but not with T min. or T max. along an altitudinal gradient. 相似文献
48.
Illegal hunting has been a major threat for the survival of wildlife fauna, including the three crocodile species that India harbours: Crocodylus palustris, Crocodylus porosus and Gavialis gangeticus. Although law prevents trade on these species, illicit hunting for trade continues to threaten the survival of these endangered species; conservation strategies therefore require a rapid molecular identification technique for Indian crocodiles. A multiplex polymerase chain reaction (PCR) assay with species-specific primers, considered as one of the most effective molecular techniques, is described herein. The primers were designed to yield species-specific sized amplicons. The assay discriminates the three Indian crocodile species unambiguously within a short time period using only simple agarose gel electrophoresis. We recommend this multiplex PCR assay to be used in the identification of Indian crocodile species. 相似文献
49.
Jinjoo Kang Swapnika Ramu Sunju Lee Berenice Aguilar Sathish Kumar Ganesan Jaehyuk Yoo Vijay K. Kalra Young-Kwon Hong 《Analytical biochemistry》2009,386(2):251-75
Although various nonviral transfection methods are available, cell toxicity, low transfection efficiency, and high cost remain hurdles for in vitro gene delivery in cultured primary endothelial cells. Recently, unprecedented transfection efficiency for primary endothelial cells has been achieved due to the newly developed nucleofection technology that uses a combination of novel electroporation condition and specific buffer components that stabilize the cells in the electrical field. Despite superior transfection efficiency and cell viability, high cost of the technology has discouraged cardiovascular researchers from liberally adopting this new technology. Here we report that a phosphate-buffered saline (PBS)-based nucleofection method can be used for efficient gene delivery into primary endothelial cells and other types of cells. Comparative analyses of transfection efficiency and cell viability for primary arterial, venous, microvascular, and lymphatic endothelial cells were performed using PBS. Compared with the commercial buffers, PBS can support equally remarkable nucleofection efficiency to both primary and nonprimary cells. Moreover, PBS-mediated nucleofection of small interfering RNA (siRNA) showed more than 90% knockdown of the expression of target genes in primary endothelial cells. We demonstrate that PBS can be an unprecedented economical alternative to the high-cost buffers or nucleofection of various primary and nonprimary cells. 相似文献
50.
beta-amyloid-induced migration of monocytes across human brain endothelial cells involves RAGE and PECAM-1 总被引:8,自引:0,他引:8
Giri R Shen Y Stins M Du Yan S Schmidt AM Stern D Kim KS Zlokovic B Kalra VK 《American journal of physiology. Cell physiology》2000,279(6):C1772-C1781
In patients withamyloid -related cerebrovascular disorders, e.g., Alzheimer'sdisease, one finds increased deposition of amyloid peptide (A) andincreased presence of monocyte/microglia cells in the brain. However,relatively little is known of the role of A in the trafficking ofmonocytes across the blood-brain barrier (BBB). Our studies show thatinteraction of A1-40 with monolayer of human brainendothelial cells results in augmented adhesion and transendothelialmigration of monocytic cells (THP-1 and HL-60) and peripheral bloodmonocytes. The A-mediated migration of monocytes was inhibited byantibody to A receptor (RAGE) and platelet endothelial cell adhesionmolecule (PECAM-1). Additionally, A-induced transendothelialmigration of monocytes were inhibited by protein kinase C inhibitor andaugmented by phosphatase inhibitor. We conclude that interaction ofA with RAGE expressed on brain endothelial cells initiates cellularsignaling leading to the transendothelial migration of monocytes. Wesuggest that increased diapedesis of monocytes across the BBB inresponse to A present either in the peripheral circulation or in thebrain parenchyma may play a role in the pathophysiology of A-relatedvascular disorder. 相似文献