全文获取类型
收费全文 | 11685篇 |
免费 | 1241篇 |
国内免费 | 2844篇 |
出版年
2024年 | 32篇 |
2023年 | 155篇 |
2022年 | 314篇 |
2021年 | 523篇 |
2020年 | 453篇 |
2019年 | 551篇 |
2018年 | 499篇 |
2017年 | 408篇 |
2016年 | 512篇 |
2015年 | 760篇 |
2014年 | 906篇 |
2013年 | 865篇 |
2012年 | 1179篇 |
2011年 | 1069篇 |
2010年 | 766篇 |
2009年 | 695篇 |
2008年 | 856篇 |
2007年 | 777篇 |
2006年 | 748篇 |
2005年 | 649篇 |
2004年 | 531篇 |
2003年 | 554篇 |
2002年 | 425篇 |
2001年 | 268篇 |
2000年 | 253篇 |
1999年 | 240篇 |
1998年 | 140篇 |
1997年 | 120篇 |
1996年 | 92篇 |
1995年 | 66篇 |
1994年 | 69篇 |
1993年 | 47篇 |
1992年 | 41篇 |
1991年 | 38篇 |
1990年 | 22篇 |
1989年 | 25篇 |
1988年 | 16篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 18篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1978年 | 4篇 |
1971年 | 2篇 |
1966年 | 2篇 |
1965年 | 3篇 |
1962年 | 3篇 |
1961年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Wu‐Xia Qiu Xiao‐Li Ma Xiao Lin Fan Zhao Di‐Jie Li Zhi‐Hao Chen Ke‐Wen Zhang Ru Zhang Pai Wang Yun‐Yun Xiao Zhi‐Ping Miao Kai Dang Xiao‐Yang Wu Ai‐Rong Qian 《Journal of cellular and molecular medicine》2020,24(1):317-327
Microtubule actin cross‐linking factor 1 (Macf1) is a spectraplakin family member known to regulate cytoskeletal dynamics, cell migration, neuronal growth and cell signal transduction. We previously demonstrated that knockdown of Macf1 inhibited the differentiation of MC3T3‐E1 cell line. However, whether Macf1 could regulate bone formation in vivo is unclear. To study the function and mechanism of Macf1 in bone formation and osteogenic differentiation, we established osteoblast‐specific Osterix (Osx) promoter‐driven Macf1 conditional knockout mice (Macf1f/fOsx‐Cre). The Macf1f/fOsx‐Cre mice displayed delayed ossification and decreased bone mass. Morphological and mechanical studies showed deteriorated trabecular microarchitecture and impaired biomechanical strength of femur in Macf1f/fOsx‐Cre mice. In addition, the differentiation of primary osteoblasts isolated from calvaria was inhibited in Macf1f/fOsx‐Cre mice. Deficiency of Macf1 in primary osteoblasts inhibited the expression of osteogenic marker genes (Col1, Runx2 and Alp) and the number of mineralized nodules. Furthermore, deficiency of Macf1 attenuated Bmp2/Smad/Runx2 signalling in primary osteoblasts of Macf1f/fOsx‐Cre mice. Together, these results indicated that Macf1 plays a significant role in bone formation and osteoblast differentiation by regulating Bmp2/Smad/Runx2 pathway, suggesting that Macf1 might be a therapeutic target for bone disease. 相似文献
142.
Xiuxiang Liu Jinjin Wu Chenying Zhu Jie Liu Xiaoli Chen Tao Zhuang Yashu Kuang Yanfang Wang Hao Hu Ping Yu Huimin Fan Yuzhen Zhang Zhongmin Liu Lin Zhang 《Journal of cellular and molecular medicine》2020,24(2):2013-2026
Cardiac vascular microenvironment is crucial for cardiac remodelling during the process of heart failure. Sphingosine 1‐phosphate (S1P) tightly regulates vascular homeostasis via its receptor, S1pr1. We therefore hypothesize that endothelial S1pr1 might be involved in pathological cardiac remodelling. In this study, heart failure was induced by transverse aortic constriction (TAC) operation. S1pr1 expression is significantly increased in microvascular endothelial cells (ECs) of post‐TAC hearts. Endothelial‐specific deletion of S1pr1 significantly aggravated cardiac dysfunction and deteriorated cardiac hypertrophy and fibrosis in myocardium. In vitro experiments demonstrated that S1P/S1pr1 praxis activated AKT/eNOS signalling pathway, leading to more production of nitric oxide (NO), which is an essential cardiac protective factor. Inhibition of AKT/eNOS pathway reversed the inhibitory effect of EC‐S1pr1‐overexpression on angiotensin II (AngII)‐induced cardiomyocyte (CM) hypertrophy, as well as on TGF‐β‐mediated cardiac fibroblast proliferation and transformation towards myofibroblasts. Finally, pharmacological activation of S1pr1 ameliorated TAC‐induced cardiac hypertrophy and fibrosis, leading to an improvement in cardiac function. Together, our results suggest that EC‐S1pr1 might prevent the development of pressure overload‐induced heart failure via AKT/eNOS pathway, and thus pharmacological activation of S1pr1 or EC‐targeting S1pr1‐AKT‐eNOS pathway could provide a future novel therapy to improve cardiac function during heart failure development. 相似文献
143.
Wei Wu Xiao‐Hui Jia Sha Zhang Chun‐Mao Dong Feng‐Hua Kang Zhen‐Xing Zou Kang‐Ping Xu 《化学与生物多样性》2020,17(6)
Two new abietane diterpenoids, (3S,5R,10S)‐3‐hydroxy‐12‐O‐demethyl‐11‐deoxy‐19(4→3)‐abeo‐cryptojaponol, 12,19‐dihydroxyabieta‐8,11,13‐trien‐7‐one, were isolated from Selaginella moellendorffii Hieron., together with one known abietane diterpenoid and four known tetracyclic triterpenoids. Their structures were characterized by their 1D‐ and 2D‐NMR, ECD and mass spectral studies. All compounds were tested for their inhibitory effects on proliferation of three human cancer cells (human non‐small‐cell lung carcinoma cell lines A549 and human breast adenocarcinoma cell lines MDA‐MB‐231 and MCF‐7) in vitro. Among them, three compounds displayed modest cytotoxic activities against the above three human cancer cell lines with IC50 values ranging from 16.28 to 40.67 μM. 相似文献
144.
Zhan Yijing Zhu Ping Liang Jinfeng Xu Zheng Feng Xiaohai Liu Yi Xu Hong Li Sha 《Bioprocess and biosystems engineering》2020,43(1):75-84
Bioprocess and Biosystems Engineering - A safe, efficient, environmentally friendly process for producing isomaltulose is needed. Here, the biocatalyst, sucrose isomerase (SIase) from Erwinia... 相似文献
145.
目的:探讨不同剂量舒芬太尼对心脏瓣膜置换术患者应激反应、炎性因子及心肌损伤的影响。方法:根据随机数字表法将100例行心脏瓣膜置换术的患者分为低剂量组(n=33,舒芬太尼剂量为1.0μg/kg)、中剂量组(n=33,舒芬太尼剂量为1.5μg/kg)以及高剂量组(n=34,舒芬太尼剂量为2.0μg/kg),比较三组患者应激反应、炎性因子、心肌损伤等指标的变化以及围术期指标情况。结果:中剂量组、高剂量组麻醉诱导后(T1)、插管后1 min(T2)、插管后5 min(T3)、插管后10 min(T4)时间点心率(HR)、平均动脉压(MAP)均低于低剂量组同时间点,且高剂量组低于中剂量组(P<0.05)。与低剂量组比较,中剂量组、高剂量组阻断后30 min(T6)、开主动脉后2h(T7)以及术后1d(T8)时间点白介素-6(IL-6)、肿瘤坏死因子-α(TNF-α)均降低(P<0.05)。与低剂量组比较,中剂量组、高剂量组体外循环停机2h(T9)、体外循环停机8h(T10)、体外循环停机24h(T11)、体外循环停机48h(T12)时间点心肌肌钙蛋白I(cTnI)、肌酸磷酸激酶同工酶(CK-MB)均降低(P<0.05)。低剂量组、中剂量组重症监护室(ICU)滞留时间、拔管时间显著短于高剂量组(P<0.05),而三组心血管不良事件发生率比较差异无统计学意义(P>0.05)。结论:给予1.0μg/kg舒芬太尼麻醉的患者应激反应小,1.5μg/kg、2.0μg/kg舒芬太尼可更好地控制心脏瓣膜置换术患者炎性反应,同时对患者心肌损伤有一定的保护作用,但2.0μg/kg舒芬太尼会延长患者ICU滞留时间、拔管时间。 相似文献
146.
目的:探讨食道癌组织微小RNA-21(miR-21)、微小RNA-182(miR-182)表达与临床病理特征及预后的关系。方法:选取2011年4月到2013年7月期间在我院接受手术治疗的食道癌患者84例,取患者的癌组织和癌旁正常组织作为检验标本,比较癌组织和癌旁正常组织中miR-21、mi R-182的表达水平,并分析食道癌组织中mi R-182、mi R-21的表达与临床病理特征及预后的关系。结果:癌组织中mi R-21、mi R-182的相对表达量明显高于癌旁正常组织,差异有统计学意义(P<0.05)。食道癌组织中mi R-21的表达与淋巴结转移、临床分期有关(P<0.05),与性别、年龄、分化程度、肿瘤大小无关(P>0.05);食道癌患者癌组织中miR-182的表达与年龄、性别、肿瘤大小无关(P>0.05),与分化程度、临床分期、淋巴结转移有关(P<0.05)。食道癌癌组织中miR-21、miR-182高表达患者的中位生存时间均低于低表达患者,差异有统计学意义(P<0.05)。结论:食道癌组织mi R-21、mi R-182表达与患者的部分临床病理特征及预后有关,两者有望成为食道癌新的治疗靶点。 相似文献
147.
目的:探究ZLA对神经元型AChE的抑制活性及其对中枢胆碱能神经功能障碍导致的学习记忆功能减退的改善作用。方法:通过体外实验观察ZLA对神经元型AChE活性的影响;通过ex vivo实验观察ZLA体内AChE抑制活性;利用Morris水迷宫行为学实验探讨ZLA对东莨菪碱诱发的小鼠学习记忆功能障碍的改善作用。结果:ZLA明显抑制人SH-SY5Y神经元细胞和小鼠海马神经元来源的AChE活性。另外,ZLA腹腔注射后以剂量依赖性方式抑制小鼠脑内AChE活性。Morris水迷宫实验结果显示,ZLA显著改善东莨菪碱引起的学习和记忆功能障碍。结论:ZLA能够抑制神经元型AChE活性并具有促智作用。 相似文献
148.
目的:探讨胃癌组织长链非编码RNA(lncRNA)DHHC型锌指蛋白8假基因1(ZDHHC8P1)、母系表达基因3(MEG3)、牛磺酸上调基因1(TUG1)表达与临床病理特征和预后的关系。方法:选取2013年1月至2016年1月我院病理科收集的83例胃癌患者经手术切除或胃镜活检的癌组织及癌旁组织石蜡标本,检测胃癌和癌旁组织中ZDHHC8P1、MEG3、TUG1表达。分析ZDHHC8P1、MEG3、TUG1表达与胃癌临床病理特征的关系。随访所有患者,分析ZDHHC8P1、MEG3、TUG1表达与患者预后的关系。结果:胃癌组织中ZDHHC8P1、TUG1表达量均高于癌旁组织(P0.05),MEG3表达量低于癌旁组织(P0.05)。ZDHHC8P1表达与肿瘤直径、分化程度、浸润深度、TNM分期、淋巴结转移、远处转移有关(P0.05),MEG3、TUG1表达与分化程度、浸润深度、淋巴结转移有关(P0.05)。Kaplan-Meier生存曲线分析结果显示ZDHHC8P1、TUG1高表达患者无疾病进展生存(PFS)率、总生存(OS)率低于ZDHHC8P1、TUG1低表达患者(P0.05),MEG3低表达患者PFS、OS率低于MEG3高表达患者(P0.05)。Cox风险回归分析结果显示淋巴结转移、ZDHHC8P1高表达、TUG1高表达、MEG3低表达是胃癌患者不良预后的危险因素(HR=1.613、1.956、2.512、-0.824,P0.05)。结论:胃癌组织中ZDHHC8P1、TUG1呈高表达,MEG3呈低表达,ZDHHC8P1、TUG1、MEG3表达均与胃癌临床病理特征和预后有关,可作为胃癌患者预后评估的辅助指标。 相似文献
149.
Jun‐Xia Su Cong‐Cong Dong Yan‐Ting Niu Li‐Min Lu Chao Xu Bing Liu Shi‐Liang Zhou An‐Ming Lu Yu‐Ping Zhu Jun Wen Zhi‐Duan Chen 《植物分类学报:英文版》2020,58(5):710-724
Species concept and delimitation are fundamental to taxonomic and evolutionary studies. Both inadequate informative sites in the molecular data and limited taxon sampling have often led to poor phylogenetic resolution and incorrect species delineation. Recently, the whole chloroplast genome sequences from extensive herbarium specimen samples have been shown to be effective to amend the problem. Stachyuraceae are a small family consisting of only one genus Stachyurus of six to 16 species. However, species delimitation in Stachyurus has been highly controversial because of few and generally unstable morphological characters used for classification. In this study, we sampled 69 individuals of seven species (each with at least three individuals) covering the entire taxonomic diversity, geographic range, and morphological variation of Stachyurus from herbarium specimens for genome‐wide plastid gene sequencing to address species delineation in the genus. We obtained high‐quality DNAs from specimens using a recently developed DNA reconstruction technique. We first assembled four whole chloroplast genome sequences. Based on the chloroplast genome and one nuclear ribosomal DNA sequence of Stachyurus, we designed primers for multiplex polymerase chain reaction and high throughput sequencing of 44 plastid loci for species of Stachyurus. Data of these chloroplast DNA and nuclear ribosomal DNA internal transcribed spacer sequences were used for phylogenetic analyses. The phylogenetic results showed that the Japanese species Stachyurus praecox Siebold & Zucc. was sister to the rest in mainland China, which indicated a typical Sino‐Japanese distribution pattern. Based on diagnostic morphological characters, distinct distributional range, and monophyly of each clade, we redefined seven species for Stachyurus following an integrative species concept, and revised the taxonomy of the family based on previous reports and specimens, in particular the type specimens. Furthermore, our divergence time estimation results suggested that Stachyuraceae split from its sister group Crossosomataceae from the New World at ca. 54.29 Mya, but extant species of Stachyuraceae started their diversification only recently at ca. 6.85 Mya. Diversification time of Stachyurus in mainland China was estimated to be ca. 4.45 Mya. This research has provided an example of using the herbarium specimen‐based phylogenomic approach in resolving species boundaries in a taxonomically difficult genus. 相似文献
150.
Ba Limin Wang Zhenbao Liu William J Wu Dongxun Xiang Wangzhen Qi Peng Dong Chunna Hu Yanxin Lu Ping Xiao Jin Yu Changyuan 《中国科学:生命科学英文版》2020,63(10):1604-1607
正Dear Editor,Swine major histocompatibility complex (MHC) is a highly polymorphic gene in pigs and is also called swine leukocyte antigen (SLA)(Fan et al., 2018). SLA is divided into three major categories, SLA Ⅰ (SLA-1,-2,-3), SLA Ⅱ, and SLA Ⅲ(Smith et al., 2005). SLA Ⅰ plays an important role in cellular immunity which can eliminate viruses and other foreign 相似文献