首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   7257篇
  免费   402篇
  国内免费   21篇
  2024年   11篇
  2023年   95篇
  2022年   258篇
  2021年   368篇
  2020年   348篇
  2019年   492篇
  2018年   393篇
  2017年   270篇
  2016年   368篇
  2015年   403篇
  2014年   495篇
  2013年   639篇
  2012年   576篇
  2011年   585篇
  2010年   318篇
  2009年   263篇
  2008年   299篇
  2007年   299篇
  2006年   261篇
  2005年   216篇
  2004年   158篇
  2003年   120篇
  2002年   102篇
  2001年   20篇
  2000年   17篇
  1999年   20篇
  1998年   22篇
  1997年   20篇
  1996年   15篇
  1995年   7篇
  1994年   10篇
  1993年   13篇
  1992年   6篇
  1991年   16篇
  1990年   6篇
  1989年   11篇
  1988年   9篇
  1987年   15篇
  1986年   13篇
  1985年   19篇
  1984年   12篇
  1983年   13篇
  1982年   8篇
  1981年   6篇
  1980年   9篇
  1978年   5篇
  1976年   4篇
  1975年   4篇
  1974年   11篇
  1972年   5篇
排序方式: 共有7680条查询结果,搜索用时 15 毫秒
111.
Potato late blight, caused by the oomycete pathogen Phytophthora infestans, significantly hampers potato production. Recently, a new Resistance to Phytophthora infestans (Rpi) gene, Rpi-amr1, was cloned from a wild Solanum species, Solanum americanum. Identification of the corresponding recognized effector (Avirulence or Avr) genes from P. infestans is key to elucidating their naturally occurring sequence variation, which in turn informs the potential durability of the cognate late blight resistance. To identify the P. infestans effector recognized by Rpi-amr1, we screened available RXLR effector libraries and used long read and cDNA pathogen-enrichment sequencing (PenSeq) on four P. infestans isolates to explore the untested effectors. Using single-molecule real-time sequencing (SMRT) and cDNA PenSeq, we identified 47 highly expressed effectors from P. infestans, including PITG_07569, which triggers a highly specific cell death response when transiently coexpressed with Rpi-amr1 in Nicotiana benthamiana, suggesting that PITG_07569 is Avramr1. Here we demonstrate that long read and cDNA PenSeq enables the identification of full-length RXLR effector families and their expression profile. This study has revealed key insights into the evolution and polymorphism of a complex RXLR effector family that is associated with the recognition by Rpi-amr1.  相似文献   
112.
113.
114.
115.
Recent studies have demonstrated that chemerin participates in the regulation of female reproductive function at the level of the ovaries. Due to the lack of data concerning the presence of the chemerin system (chemerin and its receptors: CMKLR1, GPR1, CCRL2) in the ovaries of pigs, one of the most economically important livestock species, the aim of this study was to investigate the expression and localization of chemerin and its receptors in the ovaries of prepubertal and mature gilts. We also aimed to examine the concentrations of chemerin in the follicular fluid of prepubertal and mature animals. In the present study, we have demonstrated the expression patterns of chemerin system components in the porcine follicles of different sizes of prepubertal and mature animals, as well as in corpora lutea of mature gilts during the estrous cycle and early pregnancy. The obtained results suggest that the expression of chemerin system components is influenced by the reproductive stage, cell type, and the hormonal status of gilts (the estrous cycle/pregnancy). We have also presented the localization of the chemerin system components in various ovarian structures, and also showed changes in the concentration of chemerin in the follicular fluid of pigs. The presented findings not only confirm that chemerin is produced locally in the porcine ovary but they also demonstrate that chemerin directly affects ovarian cells, as confirmed by the presence of chemerin receptors in all ovarian structures. Therefore, chemerin appears to be an important intra‐ovarian factor that could regulate ovary function in pigs.  相似文献   
116.
Failed oocyte activation has been observed in unexplained infertile (UI) and asthenoteratozoospermic (AT) men. The deficiency of phospholipase C‐zeta (PLCζ) could be a possible reason for such failures and has not been studied yet. We investigated the expression and localization of PLCζ protein in the sperms of patients with UI and AT conditions. The relationships between PLCζ‐related parameters with male age, sperm characteristics, DNA integrity, and cellular maturity were assessed. Semen samples were collected from fertile (n = 40), UI (n = 40), and AT (n = 40) men. Subsequently, semen analysis, DNA fragmentation, hyaluronic acid‐binding ability, and PLCζ level along with its distribution were evaluated using computer‐assisted sperm analyzer, sperm chromatin structure assay (SCSA), hyaluronic acid‐binding assay (HBA), western blot analysis and immunofluorescence microscopy, respectively. Unlike SCSA, the values of HBA, and PLCζ expression were significantly reduced in UI and AT patients compared to fertile men, whereas no significant differences were observed among the experimental groups in terms of PLCζ localization patterns. The regression analysis also showed that HBA is the only variable associated with PLCζ levels. Furthermore, the correlation of male age with PLCζ localization in postacrosomal, equatorial, and acrosomal+postacrosomal+equatorial (A+PA+E) patterns, as well as the relation of normal morphology, with the (A+PA+E) pattern, remained in the regression model. Our findings indicated that reduced PLCζ level along with the increased DNA fragmentation and impaired maturation may be possible etiologies of decreased fertilization in the studied subjects.  相似文献   
117.
Russian Journal of Bioorganic Chemistry - Pyridazines hold considerable interest relative to pharmacologically active molecules. The pyridazine compounds are exhibited different types of...  相似文献   
118.
In the present work, a novel biocompatible scaffold was fabricated for the DNA aptamer immobilization. For the first time, amino‐functionalized dendritic fibrous nanosilica (KCC‐1‐nPr‐NH2) and gold nanoparticle supported by chitosan (AuNPs‐CS) were synthesized and electrodeposited successfully on the surface of the glassy carbon electrode by chronoamperometry technique. Unique oligonucleotide of aflatoxin M1 (5′‐ATC CGT CAC ACC TGC TCT GAC GCT GGG GTC GAC CCG GAG AAA TGC ATT CCC CTG TGG TGT TGG CTC CCG TAT) labeled by toluidine blue was immobilization on the prepared interface. Hence, a novel aptamer‐based bioassay was formed for highly sensitive quantitation of AFM1 using cyclic voltammetry and differential plus voltammetry. The structure and morphology of GQDs‐CS/KCC‐1‐nPr‐NH2 were investigated by Fourier‐transform infrared spectroscopy, X‐ray diffraction, atomic force, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy. The achieved low limit of quantification of apta‐assay for detection of AFM1 was 10fM. Also, calibration curve was linear from 0.1μM to 10fM in real samples. The proposed apta‐assay has acceptable long‐term stability. Designed aptasensor has a lot of remarkable advantages including excellent selectivity, sensitivity, and stability that could be used as facile bio‐device for the determination of AFM1 in milk samples.  相似文献   
119.
In this study, a novel electroconductive interface was prepared based on Fe3O4 magnetic nanoparticle and cysteamine functionalized gold nanoparticle. The engineered interface was used as signal amplification substrate in the electrochemical analysis of antibody‐antigen binding. For this purpose, biotinilated‐anti‐prostate‐specific antigen (PSA) antibody was bioconjugated with iron oxide magnetic nanoparticles (Fe3O4) and drop‐casted on the surface of glassy carbon electrode (GCE). Also, secondary antibody (HRP‐Ab2) encapsulated on gold nanoparticles caped by cysteamine was immobilized on the surface of GCE modified electrode. A transmission electron microscopy images shows that a sandwich immunoreaction was done and binding of Ab1 and Ab2 performed successfully. Various parameters of immunoassay, including the loading of magnetic nanoparticles, the amount of gold nanoparticle conjugate, and the immunoreaction time, were optimized. The detection limit of 0.001 μg. L?1 of PSA was obtained under optimum experimental conditions. It is found that such magneto‐bioassay could be readily used for simultaneous parallel detection of multiple proteins by using multiple inorganic metal nanoparticle tracers and are expected to open new opportunities for early stage diagnosis of cancer in near future.  相似文献   
120.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号