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211.
表面粗糙度的激光在线测量 总被引:3,自引:0,他引:3
为了克服现有方法在表面粗糙度测量范围和抗震动等方面的不足,分析了最近发展起来的几种动态表面粗糙度测量方法的优缺点,提出采用被测表面激光反射图的暗区比来实现运动表面粗糙度的实时测量。该方法的测量范围可达30倍跨度,即可测量的表面粗糙度为0.05μm到1.6μm或0.4μm到12.5μm。分析了试样的运动速度和初试平均光强对暗区比的影响,该方法的测量结果与Telyer-soft表面形貌测量仪的测量结果很吻合。 相似文献
212.
建立起适合厚片材料测试的非线性介电测试系统和相应的数据处理方法;测得了在不同场强和温度下PZT/P[VDF(77)TrFE(23)]03 型铁电复合物厚片的二阶非线性介电系数;根据Yamada 模型拟合(一阶) 介电系数的电场和温度依赖关系得到了退极化场系数Lz,并由此计算了在各电场和温度下作用于陶瓷粒子的局域场;结果说明在介电系数测试过程中,未预极化复合物试样的二阶非线性介电系数起源于分散相陶瓷粒子在局域场作用下发生的部分极化反转. 相似文献
213.
Xinmin Li Wangfun Fong Pengfei Kwok Mengsu Yang Patrick C. L. Wong Jiazuan Ni 《科学通报(英文版)》1999,44(4):331-331
Effects of La3+ and Gd3+ on Ca2+ influx were investigated in rat hepatoma H-35 cells by measuring the initial rate of45Ca2+ uptake. It was found that the maximum initial rate of Ca2+ uptake was increased six-to ten-fold at low concentrations of La3+ and Gd3+. Kinetic analyses by measuring the initial rate of Ca2+ influx at different external Ca2+ concentrations indicated the existence of two intracellular exchangeable components in the basal Ca2+ system, with low and high affinities for Ca2+, and only one class of Ca2+ binding sites was observed in the La3+-or Gd3+-treated cells. For high affinity, La3+ and Gd3+ increased both kinetic parametersK
m andV
max of basai Ca2+ influx. La3+ and Gd3+ compete directly with Ca2+ for Ca2+ binding site for low affinity. The kinetics is competitive. 相似文献
214.
基于荧光(或磷光)猝灭的氧传感器的研制(Ⅰ)——指示剂的合成及筛选 总被引:4,自引:1,他引:3
金属有机络合物被波长合适的光激发可发射荧光或磷光,这种发射光能被氧气猝灭,现合成了13种金属有机络合物,详尽地研究了它们的光谱特性及氧猝灭特性,总结了关联氧浓度(分压)和发射光强度关系的数学模型,从中筛选了两种灵敏度高、测量范围宽、光学稳定性好的氧感应指示剂,即[Ru(bathophen)3](ClO4)2和Pt(TFPP),用[Ru(bathophen)3](ClO4)2-Cab-O-Sil-Silicone膜和Pt(TFPP)-Silicone膜进行猝灭实验,证明改进的Stern-Volmer方程计算结果与猝灭数据非常一致,可以作为传感器的标定方程。 相似文献
215.
Kai Song Hao Wu H. N. Ashiqur Rahman Yunzhou Dong Aiyun Wen Megan L. Brophy Scott Wong Sukyoung Kwak Diane R. Bielenberg Hong Chen 《Cellular and molecular life sciences : CMLS》2017,74(3):393-398
VEGF-driven tumor angiogenesis has been validated as a central target in several tumor types deserving of continuous and further considerations to improve the efficacy and selectivity of the current therapeutic paradigms. Epsins, a family of endocytic clathrin adaptors, have been implicated in regulating endothelial cell VEGFR2 signaling, where its inactivation leads to nonproductive leaky neo-angiogenesis and, therefore, impedes tumor development and progression. Targeting endothelial epsins is of special significance due to its lack of affecting other angiogenic-signaling pathways or disrupting normal quiescent vessels, suggesting a selective modulation of tumor angiogenesis. This review highlights seminal findings on the critical role of endothelial epsins in tumor angiogenesis and their underlying molecular events, as well as strategies to prohibit the normal function of endogenous endothelial epsins that capitalize on these newly understood mechanisms. 相似文献
216.
Sung WK Zheng H Li S Chen R Liu X Li Y Lee NP Lee WH Ariyaratne PN Tennakoon C Mulawadi FH Wong KF Liu AM Poon RT Fan ST Chan KL Gong Z Hu Y Lin Z Wang G Zhang Q Barber TD Chou WC Aggarwal A Hao K Zhou W Zhang C Hardwick J Buser C Xu J Kan Z Dai H Mao M Reinhard C Wang J Luk JM 《Nature genetics》2012,44(7):765-769
To survey hepatitis B virus (HBV) integration in liver cancer genomes, we conducted massively parallel sequencing of 81 HBV-positive and 7 HBV-negative hepatocellular carcinomas (HCCs) and adjacent normal tissues. We found that HBV integration is observed more frequently in the tumors (86.4%) than in adjacent liver tissues (30.7%). Copy-number variations (CNVs) were significantly increased at HBV breakpoint locations where chromosomal instability was likely induced. Approximately 40% of HBV breakpoints within the HBV genome were located within a 1,800-bp region where the viral enhancer, X gene and core gene are located. We also identified recurrent HBV integration events (in ≥ 4 HCCs) that were validated by RNA sequencing (RNA-seq) and Sanger sequencing at the known and putative cancer-related TERT, MLL4 and CCNE1 genes, which showed upregulated gene expression in tumor versus normal tissue. We also report evidence that suggests that the number of HBV integrations is associated with patient survival. 相似文献
217.
218.
Haiman CA Patterson N Freedman ML Myers SR Pike MC Waliszewska A Neubauer J Tandon A Schirmer C McDonald GJ Greenway SC Stram DO Le Marchand L Kolonel LN Frasco M Wong D Pooler LC Ardlie K Oakley-Girvan I Whittemore AS Cooney KA John EM Ingles SA Altshuler D Henderson BE Reich D 《Nature genetics》2007,39(5):638-644
After the recent discovery that common genetic variation in 8q24 influences inherited risk of prostate cancer, we genotyped 2,973 SNPs in up to 7,518 men with and without prostate cancer from five populations. We identified seven risk variants, five of them previously undescribed, spanning 430 kb and each independently predicting risk for prostate cancer (P = 7.9 x 10(-19) for the strongest association, and P < 1.5 x 10(-4) for five of the variants, after controlling for each of the others). The variants define common genotypes that span a more than fivefold range of susceptibility to cancer in some populations. None of the prostate cancer risk variants aligns to a known gene or alters the coding sequence of an encoded protein. 相似文献
219.
Essential role for oncogenic Ras in tumour maintenance. 总被引:30,自引:0,他引:30
L Chin A Tam J Pomerantz M Wong J Holash N Bardeesy Q Shen R O'Hagan J Pantginis H Zhou J W Horner C Cordon-Cardo G D Yancopoulos R A DePinho 《Nature》1999,400(6743):468-472
Advanced malignancy in tumours represents the phenotypic endpoint of successive genetic lesions that affect the function and regulation of oncogenes and tumour-suppressor genes. The established tumour is maintained through complex and poorly understood host-tumour interactions that guide processes such as angiogenesis and immune sequestration. The many different genetic alterations that accompany tumour genesis raise questions as to whether experimental cancer-promoting mutations remain relevant during tumour maintenance. Here we show that melanoma genesis and maintenance are strictly dependent upon expression of H-RasV12G in a doxycycline-inducible H-Ras12G mouse melanoma model null for the tumour suppressor INK4a. Withdrawal of doxycycline and H-RasV12G down-regulation resulted in clinical and histological regression of primary and explanted tumours. The initial stages of regression involved marked apoptosis in the tumour cells and host-derived endothelial cells. Although the regulation of vascular endothelial growth factor (VEGF) was found to be Ras-dependent in vitro, the failure of persistent endogenous and enforced VEGF expression to sustain tumour viability indicates that the tumour-maintaining actions of activated Ras extend beyond the regulation of VEGF expression in vivo. Our results provide genetic evidence that H-RasV12G is important in both the genesis and maintenance of solid tumours. 相似文献
220.
Neurotransmitter release at many central synapses is initiated by an influx of calcium ions through P/Q-type calcium channels, which are densely localized in nerve terminals. Because neurotransmitter release is proportional to the fourth power of calcium concentration, regulation of its entry can profoundly influence neurotransmission. N- and P/Q-type calcium channels are inhibited by G proteins, and recent evidence indicates feedback regulation of P/Q-type channels by calcium. Although calcium-dependent inactivation of L-type channels is well documented, little is known about how calcium modulates P/Q-type channels. Here we report a calcium-dependent interaction between calmodulin and a novel site in the carboxy-terminal domain of the alpha1A subunit of P/Q-type channels. In the presence of low concentrations of intracellular calcium chelators, calcium influx through P/Q-type channels enhances channel inactivation, increases recovery from inactivation and produces a long-lasting facilitation of the calcium current. These effects are prevented by overexpression of a calmodulin-binding inhibitor peptide and by deletion of the calmodulin-binding domain. Our results reveal an unexpected association of Ca2+/calmodulin with P/Q-type calcium channels that may contribute to calcium-dependent synaptic plasticity. 相似文献