全文获取类型
收费全文 | 3494篇 |
免费 | 327篇 |
国内免费 | 378篇 |
专业分类
4199篇 |
出版年
2024年 | 17篇 |
2023年 | 52篇 |
2022年 | 111篇 |
2021年 | 218篇 |
2020年 | 136篇 |
2019年 | 165篇 |
2018年 | 158篇 |
2017年 | 108篇 |
2016年 | 150篇 |
2015年 | 191篇 |
2014年 | 261篇 |
2013年 | 253篇 |
2012年 | 322篇 |
2011年 | 292篇 |
2010年 | 196篇 |
2009年 | 167篇 |
2008年 | 175篇 |
2007年 | 154篇 |
2006年 | 139篇 |
2005年 | 131篇 |
2004年 | 130篇 |
2003年 | 111篇 |
2002年 | 100篇 |
2001年 | 93篇 |
2000年 | 73篇 |
1999年 | 73篇 |
1998年 | 42篇 |
1997年 | 26篇 |
1996年 | 24篇 |
1995年 | 28篇 |
1994年 | 21篇 |
1993年 | 18篇 |
1992年 | 9篇 |
1991年 | 12篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1955年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有4199条查询结果,搜索用时 0 毫秒
991.
The two in vivo bleeding techniques currently in use in our laboratory to diagnose a hematopoietic neoplasm in Mya arenaria are: (1) phase-contrast microscopy with fresh unstained hemocytes, and (2) bright-field microscopy with Giemsa-stained hemocytes. All in vivo diagnoses were checked by histopathological studies on tissues of the same mollusc. For both methods the correct diagnosis (true + or true ?) was made in 94 out of 100 clams examined. A gradation of tissue involvement was observed in the diseased clams and the accuracy of the in vivo diagnosis is related to the disease severity. There is a positive correlation between the degree of tissue involvement and the number of circulating neoplastic cells. For this reason the more extensive the neoplasm the better is the ability to diagnose the neoplasm by the in vivo bleeding techniques. Depending on the percentage of neoplastic cells present in the hemolymph, the neoplasm was graded from level 1 to 5, with 5 being the most severe. In general, at level 1, the accuracy of a single in vivo diagnosis varied from 66 to 71% and at level 2, the accuracy of diagnosis varied from 76 to 93%, while at all other levels the accuracy was 100%. The percentage of diseased clams detected by the in vivo bleeding technique was 89–91% and the percentage of nondiseased clams detected was 95%. These values can be further improved by combining the two tests and/or through multiple bleedings. Between the two types of in vivo tests, the Giemsa-stained hemocytes provided better precision of diagnosis than the fresh unstained cells, although the differences were slight. 相似文献
992.
993.
994.
Xiaosheng Wu Hao Wang Danping Zhu Yixia Chai Jing Wang Weiyu Dai Yizhi Xiao Weimei Tang Jiaying Li Linjie Hong Miaomiao Pei Jieming Zhang Zhizhao Lin Jide Wang Aimin Li Side Liu 《Cell death & disease》2022,13(1)
As an important regulator of intracellular protein degradation, the mechanism of the deubiquitinating enzyme family in tumour metastasis has received increasing attention. Our previous study revealed that USP3 promotes tumour progression and is highly expressed in gastric cancer (GC). Herein, we report two critical targets, COL9A3 and COL6A5, downstream of USP3, via the isobaric tags for relative and absolute quantification technique. Mechanistically, we observed that USP3 interacted with and stabilised COL9A3 and COL6A5 via deubiquitination in GC. Importantly, we found that COL9A3 and COL6A5 were essential mediators of USP3-modulated oncogenic activity in vitro and in vivo. Examination of clinical samples confirmed that elevated expression of USP3, concomitant with increased COL9A3 and COL6A5 abundance, correlates with human GC progression. These data suggest that USP3 promotes GC progression and metastasis by deubiquitinating COL9A3 and COL6A5. These findings identify a mechanism of GC metastasis regarding USP3-mediated deubiquitinating enzyme activity and suggest potential therapeutic targets for GC management.Subject terms: Gastric cancer, Ubiquitylation 相似文献
995.
A low pH extraction medium with high salts, which avoids ionization and subsequent oxidation of phenolic compounds during tissue grinding and precipitation of large amounts of materials, were successfully used to obtain total DNA from Cathaya argyrophylla Chun et Kuang, Paeonia suffruticosa var. spontanea, Cimici fuga nanchuanensis Hsiao, Adenophora potaninii (Congeneric species with A. lobophylla) etc. The DNA yields, quality and purity were characterized. These isolated DNA could be used directly for RFLP and RAPD analysis which are useful as molecular genetic markers without sedimentation in cesium chloride gradient or column chromatography. A fast, inexpensive and reliable procedure has been developed for detecting the genetic diversity of endangered plants. 相似文献
996.
997.
Design and synthesis of amidino-tyrosine derivatives as non-peptide fibrinogen receptor antagonists.
T L Xu X T Jiang W Y Hua P Z Ni Y M Pei 《Bioorganic & medicinal chemistry letters》1999,9(14):1933-1936
The design, synthesis and antiaggregation activity of amidino-tyrosine derivatives based on Arg-Gly-Asp (RGD) tripeptide sequence as non-peptide fibrinogen receptor antagonists is described. Optimization of the spacer and the substituent at the C-terminal is reported. 相似文献
998.
我国D2-43病毒株PrM-E基因的重组SFV的制备及生物学鉴定 总被引:6,自引:0,他引:6
为构建含PrM E基因的重组SFV病毒 ,将含我国登革 2型病毒PrM E基因的SFV表达载体和辅助载体DNA线性化后 ,进行体外转录 .然后将获得的 2种RNA转录物共转染BHK2 1细胞 ,以RT PCR法证明转染后的细胞培养上清中含有重组SFV .进一步将该重组病毒经蛋白酶激活后可使BHK2 1细胞产生细胞病变 ,并且以间接免疫荧光法在感染细胞内可检测到登革 2型病毒所特有的蛋白 .含我国登革 2型病毒PrM E基因的重组SFV的获得 ,为进一步观察该重组病毒的免疫原性奠定了基础 ,从而为登革新型疫苗的研制提供新途径 相似文献
999.
Jun Zou Xuanzeng Pei Dan Xing Xiaojun Wu Shuai Chen 《Journal of cellular and molecular medicine》2021,25(20):9826-9836
Long non-coding RNAs (lncRNAs) biological functions and molecular mechanisms associated with pancreatic cancer (PC) remain to be poorly elucidated. We aimed to clarify the role of lncRNA LINC00261 (LINC00261) in PC and confirm its regulatory mechanisms. Bioinformatics analysis, RNA pull-down and RIP assays were performed to investigate relationship between LINC00261 and forkhead box P3 (FOXP3). Further, dual-luciferase reporter gene and ChIP assays were employed to confirm the relationship among LINC00261, FOXP3 and sterol carrier protein-2 (SCP2). PC cells were introduced with a series of vectors to verify the effects of LINC00261 and SCP2 on the viability, cell cycle progression, migration and angiogenesis of PC cells. Nude mice with the xenograft tumour were used to evaluate the effects LINC00261 on the tumourigenicity. LINC00261 was lowly expressed in PC tissues and cells. SCP2 was inhibited by LINC00261 through FOXP3. Functionally, upregulated LINC00261 or downregulated SCP2 led to reduced cell viability, migration, angiogenesis and tumourigenicity potentials. This study demonstrated the inhibitory role of LINC00261 in the angiogenesis and cell cycle progression of PC cells. It acts through the negative regulation of SCP2 via targeting FOXP3. Findings in this study highlight a potentially biomarker for PC treatment. 相似文献
1000.
Manman Shi Boli Li Mingyi Kang Peng Liu Xiaofeng Yang Meishan Pei Guangyou Zhang 《Luminescence》2024,39(5):e4773
Two Schiff base probes ( S1 and S2 ) were prepared and synthesized by incorporating thienopyrimidine into salicylaldehyde or 3-ethoxysalicylaldehyde individually, with the aim of detecting Ga3+ and Pd2+ sequentially. Upon chelation with Ga3+, S1 and S2 exhibited fluorescence enhancement in DMSO/H2O buffer. Both S1 –Ga3+ and S2 –Ga3+ were quenched by Pd2+. The limit of detection for S1 in response to Ga3+ and Pd2+ was 2.86 × 10−7 and 4.4 × 10−9 M, respectively. For S2 , the limit of detection for Ga3+ and Pd2+ was 4.15 × 10−8 and 3.0 × 10−9 M, respectively. Furthermore, the complexation ratios of both S1 and S2 with Ga3+ and Pd2+ were determined to be 1:2 through Job's plots, ESI-MS analysis, and theoretical calculations. Two molecular logic gates were constructed, leveraging the response behaviors of S1 and S2 . Moreover, the potential utility of S1 and S2 for monitoring Ga3+ and Pd2+ in domestic water was verified. 相似文献