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   5296篇
  免费   443篇
  国内免费   355篇
  2024年   6篇
  2023年   54篇
  2022年   106篇
  2021年   240篇
  2020年   167篇
  2019年   216篇
  2018年   196篇
  2017年   118篇
  2016年   230篇
  2015年   322篇
  2014年   360篇
  2013年   381篇
  2012年   467篇
  2011年   479篇
  2010年   281篇
  2009年   268篇
  2008年   311篇
  2007年   285篇
  2006年   235篇
  2005年   188篇
  2004年   167篇
  2003年   162篇
  2002年   126篇
  2001年   94篇
  2000年   89篇
  1999年   65篇
  1998年   30篇
  1997年   43篇
  1996年   54篇
  1995年   30篇
  1994年   27篇
  1993年   25篇
  1992年   48篇
  1991年   29篇
  1990年   22篇
  1989年   18篇
  1988年   24篇
  1987年   21篇
  1986年   13篇
  1985年   13篇
  1984年   8篇
  1983年   17篇
  1982年   10篇
  1981年   8篇
  1980年   5篇
  1977年   4篇
  1975年   4篇
  1974年   3篇
  1973年   3篇
  1965年   3篇
排序方式: 共有6094条查询结果,搜索用时 15 毫秒
951.
为了确定粗纤维调节素(Un) 是否具有促进成纤维细胞Ⅰ型胶原合成的作用, 我们采用地高辛原位杂交和斑点杂交技术, 观察了Un 对小鼠成纤维细胞(NIH/3T3) Ⅰ型前胶原m RNA转录的影响; 结果发现Un 对体外培养的3T3 细胞Ⅰ型前胶原基因转录具有促进作用; 提示Un 不仅作为一种细胞外基质而存在, 并且还有促进胶原合成的功能。  相似文献   
952.
型两用核不育系水稻的育性转换是受光周期及温度所调控,光周期和温度的变化会引起水稻一系列的生理生化特性的改变,为此,不少研究者通过研究光温诱导产生的生理生化等的变化与育性表达的关系来探讨两用稻的育性转换的机理。蛋白质是基因表达的稳定产物,也是生物体内许...  相似文献   
953.
Thyroglobulin (Tg)-specific Abs occur commonly in thyroid disease, but it is not clear to what extent they affect Tg processing and presentation to T cells. Here we show that generation of the nondominant pathogenic Tg epitope (2549-2560), containing thyroxine (T4) at position 2553 (T4(2553)), is augmented by Tg-specific IgG mAbs that facilitate FcR-mediated internalization of Tg. However, other mAbs of the same (IgG1) subclass enhanced Tg uptake by APC but had no effect on the generation of this peptide. Treatment of APC with chloroquine or glutaraldehyde abrogated enhanced generation of T4(2553). The boosting effect was selective, since the enhancing mAbs did not facilitate generation of the neighboring cryptic (2495-2511) peptide, which is also pathogenic in mice. When Tg was simultaneously complexed to a mAb reactive with T4(2553) and to a mixture of boosting mAbs, the presentation of this epitope was totally suppressed. These results suggest that Tg-specific Abs alter Tg processing and may boost or suppress the presentation of nondominant pathogenic determinants during the course of disease.  相似文献   
954.
香椿离体快繁技术研究   总被引:5,自引:3,他引:2  
6~7月取香棒当年生半木质化、具腋芽的茎段为外植体,诱导腋芽萌发,进行繁殖培养。通过大量试验,筛选出各阶段适宜的培养基组成。萌芽诱导阶段培养在MS+6-BA0.2mg/L中,腋芽萌发早,生长快;在继代和增殖培养中以MS+6-BA0.2mg/L效果较好,MS+ZT0.2mg/L+GA32.0mg/L次之。培养30天繁殖倍数3.1~4.0,在仅含MS有机元素。铁盐减半、蔗糖15g/L的固体培养基中,附  相似文献   
955.
开封沙地试验区不同作物种植方式的综合效益评价   总被引:9,自引:0,他引:9  
开封沙区地处河南省沙区腹地,风沙灾害严重,旱涝灾害频繁,地力瘠薄,严重障碍着沙区农牧业生产的发展。因此,自1983年在国家科技攻关的基础上建立了开封沙地试验区,探索平原沙区农业生产的发展模式。尤其是“八五”攻关期间,深化农林牧复合生态系统的优化研究,...  相似文献   
956.
Photo-assisted ion batteries demonstrate remarkable potential for portable and decentralized solar energy utilization, due to their profound capacity enhancement under irradiation accompanied by promoted discharge voltages. However, ion batteries in practice are highly compact with limited surface area for irradiation. Overcoming the size limit for irradiation is a challenge. Herein, an irradiation spillover effect in photo-assisted ion batteries is demonstrated, that is the impact of irradiation on the battery is not restrained within the irradiated area but can spillover the whole electrode. This phenomenon is a consequence of the light-induced potential difference between irradiated and unirradiated regions, leading to selective ion insertion. Irradiated regions favored H+ insertion due to light-induced proton-coupled electron transfer, while unirradiated regions preferred Zn2+ insertion. Consequently, the capacity enhancement remains unaffected by halving the irradiated area. This study overcomes the irradiation size limit for photo-assisted ion batteries and encourages highly integrated photo-assisted ion batteries for practice application.  相似文献   
957.
Sodium-ion batteries (SIBs), based on hard carbon anodes and Na+-intercalation compound cathodes, have gained significant attention. Nonetheless, hard carbon anodes involve the storage of Na+ at a low potential, typically below 0.1 V (vs Na/Na+), which increases the risk of dendritic Na growth on the anode surface during overcharging. Herein, a safe organic/inorganic composite anode containing tetrasodium 3,4,9,10-perylenetetracarboxylate (Na4PTC) and Metallic bismuth (Bi) with a weight ratio of 7:2, which exhibits an average potential of 0.7 V (vs Na+/Na) and a capacity of 150 mAh g−1 is proposed. The electrode reaction involves a reversible coordination reaction within the organic host and alloying reactions within the metallic Bi component. Importantly, the organic component efficiently buffers the volume changes in Bi during the alloying reaction, while the metallic Bi enhances the electronic conductivity of the organic material. As a result, this composite anode shows high cycle stability and rate performance, even under high mass loadings ranging from 10 to 50 mg cm−2. Furthermore, it is demonstrated that the Na-ion full cell, consisting of the composite anode and the Na3V2O2(PO4)2F cathode, exhibits minimal capacity degradation over 100 cycles while maintaining a high areal capacity of 1.1 mA cm−2.  相似文献   
958.
Soybean(Glycine max) is a major source of plant protein and oil.Soybean breeding has benefited from advances in functional genomics.In particular,the release of soybean reference genomes has advanced our understanding of soybean adaptation to soil nutrient deficiencies,the molecular mechanism of symbiotic nitrogen(N) fixation,biotic and abiotic stress tolerance,and the roles of flowering time in regional adaptation,plant architecture,and seed yield and quality.Nevertheless,many challenges remain...  相似文献   
959.
960.
Chronic pancreatitis (CP) is described as progressive inflammatory fibrosis of pancreas, accompanied with irreversible impaired endocrine and exocrine insufficiency. Pancreatic stellate cells (PSCs) are widely distributed in the stroma of the pancreas and PSCs activation has been shown as one of the leading causes for pancreatic fibrosis. Our previous study has revealed that autophagy is dramatically activated in CP tissues, which facilitates PSCs activation and pancreatic fibrosis. Long non-coding RNAs (LncRNAs) have been recognized as crucial regulators for fibrosis-related diseases. LncRNAs interact with RNA binding protein or construct competitive endogenous RNA (ceRNA) hypothesis which elicited the fibrotic processes. Until now, the effects of lncRNAs on PSCs activation and pancreatic fibrosis have not been clearly explored. In this study, a novel lncRNA named Lnc-PFAR was found highly expressed in mouse and human CP tissues. Our data revealed that Lnc-PFAR facilitates PSCs activation and pancreatic fibrosis via RB1CC1-induced autophagy. Lnc-PFAR reduces miR-141 expression by suppressing pre-miR-141 maturation, which eventually upregulates the RB1CC1 and fibrosis-related indicators expression. Meanwhile, Lnc-PFAR enhanced PSCs activation and pancreatic fibrosis through trigging autophagy. Our study interrogates a novel lncRNA-induced mechanism in promoting the development of pancreatic fibrosis, and Lnc-PFAR is suggested to be a prospective therapeutic target in clinical scenarios.Subject terms: RNAi, Diagnostic markers, Chronic pancreatitis  相似文献   
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