全文获取类型
收费全文 | 17926篇 |
免费 | 1425篇 |
国内免费 | 1591篇 |
专业分类
20942篇 |
出版年
2024年 | 42篇 |
2023年 | 227篇 |
2022年 | 608篇 |
2021年 | 1002篇 |
2020年 | 659篇 |
2019年 | 794篇 |
2018年 | 763篇 |
2017年 | 524篇 |
2016年 | 750篇 |
2015年 | 1119篇 |
2014年 | 1336篇 |
2013年 | 1392篇 |
2012年 | 1667篇 |
2011年 | 1476篇 |
2010年 | 901篇 |
2009年 | 821篇 |
2008年 | 905篇 |
2007年 | 800篇 |
2006年 | 729篇 |
2005年 | 671篇 |
2004年 | 524篇 |
2003年 | 474篇 |
2002年 | 370篇 |
2001年 | 300篇 |
2000年 | 279篇 |
1999年 | 272篇 |
1998年 | 172篇 |
1997年 | 158篇 |
1996年 | 181篇 |
1995年 | 138篇 |
1994年 | 154篇 |
1993年 | 98篇 |
1992年 | 114篇 |
1991年 | 109篇 |
1990年 | 79篇 |
1989年 | 75篇 |
1988年 | 48篇 |
1987年 | 57篇 |
1986年 | 38篇 |
1985年 | 28篇 |
1984年 | 37篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1971年 | 2篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
143.
144.
The espins are a family of multifunctional actin cytoskeletal proteins. They are present in hair cell stereocilia and are the target of mutations that cause deafness and vestibular dysfunction. Here, we demonstrate that the different espin isoforms are expressed in complex spatiotemporal patterns during inner ear development. Espin 3 isoforms were prevalent in the epithelium of the otic pit, otocyst and membranous labyrinth as they underwent morphogenesis. This espin was down-regulated ahead of hair cell differentiation and during neuroblast delamination. Espin also accumulated in the epithelium of branchial clefts and pharyngeal pouches and during branching morphogenesis in other embryonic epithelial tissues, suggesting general roles for espins in epithelial morphogenesis. Espin reappeared later in inner ear development in differentiating hair cells. Its levels and compartmentalization to stereocilia increased during the formation and maturation of stereociliary bundles. Late in embryonic development, espin was also present in a tail-like process that emanated from the hair cell base. Increases in the levels of espin 1 and espin 4 isoforms correlated with stereocilium elongation and maturation in the vestibular system and cochlea, respectively. Our results suggest that the different espin isoforms play specific roles in actin cytoskeletal regulation during epithelial morphogenesis and hair cell differentiation. 相似文献
145.
Yu Hua Tong Tie Pei Zhu Ze Lin Zhao Hai Jing Zhan Fang Zheng Jiang Heng Li Lian 《PloS one》2015,10(12)
Objectives
In this study, we develop a microdensitometry method using full width at half maximum (FWHM) analysis of the retinal vascular structure in a spectral-domain optical coherence tomography (SD-OCT) image and present the application of this method in the morphometry of arteriolar changes during hypertension.Methods
Two raters using manual and FWHM methods measured retinal vessel outer and lumen diameters in SD-OCT images. Inter-rater reproducibility was measured using coefficients of variation (CV), intraclass correlation coefficient and a Bland-Altman plot. OCT images from forty-three eyes of 43 hypertensive patients and 40 eyes of 40 controls were analyzed using an FWHM approach; wall thickness, wall cross-sectional area (WCSA) and wall to lumen ratio (WLR) were subsequently calculated.Results
Mean difference in inter-rater agreement ranged from -2.713 to 2.658 μm when using a manual method, and ranged from -0.008 to 0.131 μm when using a FWHM approach. The inter-rater CVs were significantly less for the FWHM approach versus the manual method (P < 0.05). Compared with controls, the wall thickness, WCSA and WLR of retinal arterioles were increased in the hypertensive patients, particular in diabetic hypertensive patients.Conclusions
The microdensitometry method using a FWHM algorithm markedly improved inter-rater reproducibility of arteriolar morphometric analysis, and SD-OCT may represent a promising noninvasive method for in vivo arteriolar morphometry. 相似文献146.
Ri-Sheng Tang Jian-Chu Zheng Zhi-Qing Jin Da-Dong Zhang Yi-Hong Huang Liu-Gen Chen 《Plant Growth Regulation》2008,54(1):37-43
In order to explore the possible physiological mechanism of high temperature induced sterility in rice, we examined the floret
sterility and endogenous plant growth regulator contents in pollens of two hybrid rice cultivars Shanyou63 and Teyou559 that
are tolerant and susceptible to high temperature, respectively. Indexes of floret sterility, pollen activity, and variation
of endogenous indole-3-acetic acid (IAA), gibberellic acids (GAs), abscisic acid (ABA), free proline and soluble proteins
in anthers were measured. We found that during the course of high temperature treatment, both cultivars exhibited a marked
decrease in pollen activity, pollen germination and floret fertility; however, the high temperature tolerant Shanyou63 showed
a much slower rate of decrease than the high temperature susceptible Teyou559. In addition, anthers of both cultivars displayed
a decrease in the contents of IAA, GAs, free proline and soluble proteins but an increase in the ABA content. Yet compared
to Teyou559, Shanyou63 retained significantly higher levels of free praline and GAs and a lower level of ABA, along with higher
pollen vigour and pollen germination rate even after prolonged high temperature treatment. Our study suggests a possible correlation
between pollen viability/floret sterility and high temperature-caused changes in IAA, GAs, ABA, free proline and soluble protein
contents. The severity in these changes may reflect the variation of rice cultivars in their heat stress sensitivities for
floret development. 相似文献
147.
运动后尿液蛋白质分子量与等电点的变化特征 总被引:1,自引:0,他引:1
通过对9名男性受试者在分别完成100-200m,400-800m和1 500-3 000m跑步间歇训练后尿蛋白分子量和等电点的测定发现:①运动时尿液高、低分子量蛋白质排泄率均较运动前明显增加,但以高分子量蛋白质排泄为主;②运动时尿液高、低分子量蛋白质排泄率均以400-800m间歇训练时最高,100-200m间歇训练时次之,1 500-3 000m间歇训练时最低;③运动时尿液排出的蛋白质以负离子为主 相似文献
148.
149.
Qingxia Fang Ting Liu Chenhuan Yu Xiuli Yang Yanfei Shao Jiana Shi Xiaolan Ye Xiaochun Zheng Jieping Yan Danfeng Xu Xiaozhou Zou 《Journal of cellular and molecular medicine》2020,24(6):3678-3691
The current study was designed to explore the role and underlying mechanism of lncRNA taurine up-regulated gene 1 (TUG1) in cardiac hypertrophy. Mice were treated by transverse aortic constriction (TAC) surgery to induce cardiac hypertrophy, and cardiomyocytes were treated by phenylephrine (PE) to induce hypertrophic phenotype. Haematoxylin-eosin (HE), wheat germ agglutinin (WGA) and immunofluorescence (IF) were used to examine morphological alterations. Real-time PCR, Western blots and IF staining were used to detect the expression of RNAs and proteins. Luciferase assay and RNA pull-down assay were used to verify the interaction. It is revealed that TUG1 was up-regulated in the hearts of mice treated by TAC surgery and in PE-induced cardiomyocytes. Functionally, overexpression of TUG1 alleviated cardiac hypertrophy both in vivo and in vitro. Mechanically, TUG1 sponged and sequestered miR-34a to increase the Dickkopf 1 (DKK1) level, which eventually inhibited the activation of Wnt/β-catenin signalling. In conclusion, the current study reported the protective role and regulatory mechanism of TUG1 in cardiac hypertrophy and suggested that TUG1 may serve as a novel molecular target for treating cardiac hypertrophy. 相似文献
150.
The high-molecular-weight (HMW) prolamines subunits and their coding sequences from wheat-related diploid species Crithopsis delileana were investigated. Only one HMW prolamine subunit with the similar electrophoresis mobility to the y-type HMW glutenin subunit of hexaploid wheat was observed in two accessions of C. delileana by SDS-PAGE analyses of the total storage protein fractions. It was confirmed by sequencing and expression analysis that this prolamine subunit was an x-type subunit. The amino acid sequence of this subunit had the similar typical structure to those of x-type HMW glutenin genes previously described in wheat. An in-frame stop codon was found in the coding sequences of y-type prolamine subunits. It was found by specifically extraction of HMW prolamines and sequence analysis that the coding regions of Ky prolamine subunit gene is very likely to be not expressed as a full-length protein. Phylogenetic analysis indicated that the Kx subunit could be clustered together with 1Ax1 subunit by an interior paralleled branch, and Ky subunit (inactive) was most closely related to the 1Ay subunit. The coding sequences of Kx subunit could successfully be expressed in bacterial expression system, and the expressed protein had the same electrophoresis mobility as the Kx subunit from the seed of C. delileana. It was the first time that the HMW prolamines subunits encoded by K genome of C. delileana were characterized. 相似文献