全文获取类型
收费全文 | 1133篇 |
免费 | 87篇 |
国内免费 | 71篇 |
专业分类
系统科学 | 71篇 |
丛书文集 | 28篇 |
教育与普及 | 7篇 |
理论与方法论 | 1篇 |
现状及发展 | 8篇 |
研究方法 | 13篇 |
综合类 | 1161篇 |
自然研究 | 2篇 |
出版年
2024年 | 8篇 |
2023年 | 14篇 |
2022年 | 23篇 |
2021年 | 35篇 |
2020年 | 23篇 |
2019年 | 20篇 |
2018年 | 21篇 |
2017年 | 22篇 |
2016年 | 34篇 |
2015年 | 49篇 |
2014年 | 68篇 |
2013年 | 57篇 |
2012年 | 63篇 |
2011年 | 90篇 |
2010年 | 75篇 |
2009年 | 83篇 |
2008年 | 70篇 |
2007年 | 72篇 |
2006年 | 77篇 |
2005年 | 37篇 |
2004年 | 45篇 |
2003年 | 50篇 |
2002年 | 62篇 |
2001年 | 40篇 |
2000年 | 37篇 |
1999年 | 25篇 |
1998年 | 11篇 |
1997年 | 12篇 |
1996年 | 14篇 |
1995年 | 6篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1965年 | 1篇 |
排序方式: 共有1291条查询结果,搜索用时 93 毫秒
71.
提出了一种高精度表面粗糙度非接触式轮廓仪.该仪器在6JA干涉显微镜的基础上,采用相移干涉技术、外同步技术和有效算法,以消除背景光强不均匀、人眼瞄准误差、数值孔径等因素的影响,并在条纹对比度很低的情况下也能获得良好的结果.实验结果表明,测量精度比原仪器提高10倍,测量时间仅需3s,垂直分辨率和重复测量精度优于1nm. 相似文献
72.
Krakow D Robertson SP King LM Morgan T Sebald ET Bertolotto C Wachsmann-Hogiu S Acuna D Shapiro SS Takafuta T Aftimos S Kim CA Firth H Steiner CE Cormier-Daire V Superti-Furga A Bonafe L Graham JM Grix A Bacino CA Allanson J Bialer MG Lachman RS Rimoin DL Cohn DH 《Nature genetics》2004,36(4):405-410
The filamins are cytoplasmic proteins that regulate the structure and activity of the cytoskeleton by cross-linking actin into three-dimensional networks, linking the cell membrane to the cytoskeleton and serving as scaffolds on which intracellular signaling and protein trafficking pathways are organized (reviewed in refs. 1,2). We identified mutations in the gene encoding filamin B in four human skeletal disorders. We found homozygosity or compound heterozygosity with respect to stop-codon mutations in autosomal recessive spondylocarpotarsal syndrome (SCT, OMIM 272460) and missense mutations in individuals with autosomal dominant Larsen syndrome (OMIM 150250) and the perinatal lethal atelosteogenesis I and III phenotypes (AOI, OMIM 108720; AOIII, OMIM 108721). We found that filamin B is expressed in human growth plate chondrocytes and in the developing vertebral bodies in the mouse. These data indicate an unexpected role in vertebral segmentation, joint formation and endochondral ossification for this ubiquitously expressed cytoskeletal protein. 相似文献
73.
Thibault ST Singer MA Miyazaki WY Milash B Dompe NA Singh CM Buchholz R Demsky M Fawcett R Francis-Lang HL Ryner L Cheung LM Chong A Erickson C Fisher WW Greer K Hartouni SR Howie E Jakkula L Joo D Killpack K Laufer A Mazzotta J Smith RD Stevens LM Stuber C Tan LR Ventura R Woo A Zakrajsek I Zhao L Chen F Swimmer C Kopczynski C Duyk G Winberg ML Margolis J 《Nature genetics》2004,36(3):283-287
With the availability of complete genome sequence for Drosophila melanogaster, one of the next strategic goals for fly researchers is a complete gene knockout collection. The P-element transposon, the workhorse of D. melanogaster molecular genetics, has a pronounced nonrandom insertion spectrum. It has been estimated that 87% saturation of the approximately 13,500-gene complement of D. melanogaster might require generating and analyzing up to 150,000 insertions. We describe specific improvements to the lepidopteran transposon piggyBac and the P element that enabled us to tag and disrupt genes in D. melanogaster more efficiently. We generated over 29,000 inserts resulting in 53% gene saturation and a more diverse collection of phenotypically stronger insertional alleles. We found that piggyBac has distinct global and local gene-tagging behavior from that of P elements. Notably, piggyBac excisions from the germ line are nearly always precise, piggyBac does not share chromosomal hotspots associated with P and piggyBac is more effective at gene disruption because it lacks the P bias for insertion in 5' regulatory sequences. 相似文献
74.
提出了一种具有Mandelbrot-Julia混沌分形图谱的曼德布罗特(Mandelbrot)混沌分形时空观,对经典的逃逸时间算法加以改进,提出了旋转逃逸时间算法,构造了一系列由复映射变换f1(z)=zm+c(m≥2,m∈N)和f3(z)=zω+c(ω=α+iβ)所确定的广义Mandelbrot集(简称M-集或M-分形图)及其对应的Julia集(简称J-集或J-分形图),提供了对其深入研究的新现象、新图形和新规律"图中嵌图、形中镶形、拉压与折叠、统计自相似、无限周期有稠性、混沌分形有新序".算法利用面向WEB的Java Applet技术实现,提供了一种基于Internet的分布式混沌分形理论研究机制. 相似文献
75.
TRPV3 is a calcium-permeable temperature-sensitive cation channel 总被引:37,自引:0,他引:37
Xu H Ramsey IS Kotecha SA Moran MM Chong JA Lawson D Ge P Lilly J Silos-Santiago I Xie Y DiStefano PS Curtis R Clapham DE 《Nature》2002,418(6894):181-186
Transient receptor potential (TRP) proteins are cation-selective channels that function in processes as diverse as sensation and vasoregulation. Mammalian TRP channels that are gated by heat and capsaicin (>43 degrees C; TRPV1 (ref. 1)), noxious heat (>52 degrees C; TRPV2 (ref. 2)), and cooling (< 22 degrees C; TRPM8 (refs 3, 4)) have been cloned; however, little is known about the molecular determinants of temperature sensing in the range between approximately 22 degrees C and 40 degrees C. Here we have identified a member of the vanilloid channel family, human TRPV3 (hTRPV3) that is expressed in skin, tongue, dorsal root ganglion, trigeminal ganglion, spinal cord and brain. Increasing temperature from 22 degrees C to 40 degrees C in mammalian cells transfected with hTRPV3 elevated intracellular calcium by activating a nonselective cationic conductance. As in published recordings from sensory neurons, the current was steeply dependent on temperature, sensitized with repeated heating, and displayed a marked hysteresis on heating and cooling. On the basis of these properties, we propose that hTRPV3 is thermosensitive in the physiological range of temperatures between TRPM8 and TRPV1. 相似文献
76.
Localized mutations in the gene encoding the cytoskeletal protein filamin A cause diverse malformations in humans 总被引:18,自引:0,他引:18
Robertson SP Twigg SR Sutherland-Smith AJ Biancalana V Gorlin RJ Horn D Kenwrick SJ Kim CA Morava E Newbury-Ecob R Orstavik KH Quarrell OW Schwartz CE Shears DJ Suri M Kendrick-Jones J Wilkie AO;OPD-spectrum Disorders Clinical Collaborative Group 《Nature genetics》2003,33(4):487-491
Remodeling of the cytoskeleton is central to the modulation of cell shape and migration. Filamin A, encoded by the gene FLNA, is a widely expressed protein that regulates re-organization of the actin cytoskeleton by interacting with integrins, transmembrane receptor complexes and second messengers. We identified localized mutations in FLNA that conserve the reading frame and lead to a broad range of congenital malformations, affecting craniofacial structures, skeleton, brain, viscera and urogenital tract, in four X-linked human disorders: otopalatodigital syndrome types 1 (OPD1; OMIM 311300) and 2 (OPD2; OMIM 304120), frontometaphyseal dysplasia (FMD; OMIM 305620) and Melnick-Needles syndrome (MNS; OMIM 309350). Several mutations are recurrent, and all are clustered into four regions of the gene: the actin-binding domain and rod domain repeats 3, 10 and 14/15. Our findings contrast with previous observations that loss of function of FLNA is embryonic lethal in males but manifests in females as a localized neuronal migration disorder, called periventricular nodular heterotopia (PVNH; refs. 3-6). The patterns of mutation, X-chromosome inactivation and phenotypic manifestations in the newly described mutations indicate that they have gain-of-function effects, implicating filamin A in signaling pathways that mediate organogenesis in multiple systems during embryonic development. 相似文献
77.
本实验旨在观察急性运动后血清中氧自由基代谢水平的变化情况,本实验采用自身对照的方法,24名受试者于实验前和实验后各进行一次血清中MDA、SOD以及GSH-px的水平测试.运动方式为:以75%VO2max蹬功率自行车,持续1h.结果表明:急性较大强度运动后机体中产生了大量氧自由基,同时体内抗氧化酶的活性也明显增加,自由基生成与清除的动态平衡并未遭到破坏. 相似文献
78.
目的 探讨有氧健身运动对单纯性肥胖大学生心功能的影响;方法 选取西安工业大学25名单纯性肥胖男大学生,以有氧健身运动为原则,以心功能指标为评价系统,在安静状态下,采用MCA-4B心功测试系统测试单纯性肥胖男大学生有氧健身锻炼前后部分心功能指标;结果 有氧健身锻炼前后,心功能主要指标锻炼前后存在显著性差异;结论 有氧健身操可以很好地改善单纯性肥胖大学生的心功能. 相似文献
79.
80.