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   9825篇
  免费   697篇
  国内免费   857篇
  11379篇
  2024年   19篇
  2023年   137篇
  2022年   366篇
  2021年   635篇
  2020年   363篇
  2019年   473篇
  2018年   468篇
  2017年   321篇
  2016年   455篇
  2015年   695篇
  2014年   805篇
  2013年   795篇
  2012年   935篇
  2011年   864篇
  2010年   508篇
  2009年   458篇
  2008年   507篇
  2007年   418篇
  2006年   330篇
  2005年   266篇
  2004年   233篇
  2003年   242篇
  2002年   197篇
  2001年   147篇
  2000年   113篇
  1999年   128篇
  1998年   72篇
  1997年   69篇
  1996年   63篇
  1995年   50篇
  1994年   36篇
  1993年   25篇
  1992年   39篇
  1991年   22篇
  1990年   21篇
  1989年   37篇
  1988年   14篇
  1987年   8篇
  1986年   9篇
  1985年   21篇
  1984年   4篇
  1983年   7篇
  1982年   2篇
  1981年   2篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
In order to investigate the differences in the chemical composition of Dendrobium officinale at different altitudes, we collected Dendrobium officinale from different altitudes in Guizhou Province, China, and firstly determined its polysaccharide content by using a sulfuric acid-phenol color development method with reference to the Chinese Pharmacopoeia, and further determined its metabolites by using widely targeted metabolomics, and explored the differences in the chemical composition of Dendrobium officinale at different altitudes using multivariate statistical analysis. We found that the polysaccharide content was higher in plants growing at 1122 m, a total of 902 secondary metabolites were detected by wildly targeted metabolomics, and amino acids and their derivatives were more highly expressed at 1122 m, while other metabolites were more highly expressed at 835 m. Furthermore, we found that the phenolic acid compound nerugein was only present in plants at 835 m, and two lipid compounds, namely Lyso PE 20 : 4 and its isomer, were only present at 1122 m. Taken together, these results may provide a basis for the selection and clinical application of D. officinale cultivated at different altitudes.  相似文献   
992.
993.
The drug resistance of single-target therapy has gradually become an intractable clinical problem. Combination therapy may be an effective treatment to overcome or postpone drug resistance in cancer. Herein, we discussed the synergistic effect of transforming acidic coiled-coil containing protein 3 (TACC3) suppression and cyclin-dependent kinase 1 (CDK1) in hepatocellular carcinoma (HCC). The Cancer Genome Atlas database and bioinformatics methods were implemented to analyze the expression of CDK1 and TACC3, and predict the biological function of TACC3-related genes in HCC. In addition, in vitro experiments, including cell counting kit 8, transwell and flow cytometry were utilized to evaluate cell proliferation, migration, invasion, cell cycle arrest and apoptosis of HCC cells. Our results demonstrated that TACC3 is an unfavorable and independent prognostic factor to predict poor overall survival (OS) in HCC patients. Genetic inhibition of TACC3 exhibited a remarkable antineoplastic activity of HCC cell lines. Bioinformatic prediction proposed that CDK1 may be the main regulator of TACC3-related genes in HCC. In vitro experimental measurements suggested that a combination of si-TACC3 and CDK1 inhibitor synergistically inhibited cell proliferation and migration, and induced G2 cell cycle arrest and apoptosis of HepG2 or MHCC97H cells. In conclusion, our results revealed a prospective dual-target, TACC3 and CDK1, therapeutic strategy to improve the treatment of HCC.  相似文献   
994.
995.
Jia  Kaixuan  Zhang  Xiaoling  Meng  Yijiang  Liu  Shuqi  Liu  Xiaoqing  Yang  Taixin  Wen  Chunxiu  Liu  Lingdi  Ge  Shujun 《Journal of plant research》2023,136(1):139-156
Journal of Plant Research - Aster tataricus (L.) is an important medicinal plant in China. Its roots are rich in flavonoids, the main medicinal components. However, the molecular basis of flavonoid...  相似文献   
996.
997.
The silk gland of the silkworm Bombyx mori undergoes programmed cell death (PCD) during pupal metamorphosis. On the basis of their morphological changes and the occurrence of a DNA ladder, the tissue cells were categorized into three groups: intact, committed, and dying. To identify the proteins involved in this process, we conducted a comparative proteomic analysis. Protein expression changes among the three different cell types were examined by two-dimensional gel electrophoresis. Among approximately 1000 reproducibly detected protein spots on each gel, 43 were down-regulated and 34 were up-regulated in PCD process. Mass spectrometry identified 17 differentially expressed proteins, including some well-studied proteins as well as some novel PCD related proteins, such as caspases, proteasome subunit, elongation factor, heat shock protein, and hypothetical proteins. Our results suggest that these proteins may participate in the silk gland PCD process of B. mori and, thus, provide new insights for this mechanism.  相似文献   
998.
Gold nanoparticles (GNPs) were modified with glutathione (GSH) to form GSH-capped GNPs, which have carboxyl groups on the surface of these nanoparticles. Then folic acid (FA) was conjugated with GNPs through the reaction between amino group of FA and carboxyl group of GSH. These folic acid-conjugated nanoparticles (FA-GSH-GNPs) were stable in aqueous solution over a broad range of pH and ionic strength values. The targeting of FA-GSH-GNPs in human cervices carcinoma cells (HeLa cells) with high-level folate receptor expression was confirmed by transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). No cellular uptake of these nanoparticles was observed in A549 cells lack of folate receptor. HeLa cells and mouse fibroblasts incubated with FA-GSH-GNPs were assayed by measuring the relative absorbance of the supernatant collected at low-speed centrifugation. Based on this simple spectroscopic method, HeLa cells have been detected with a detection limit of 102 cells/mL.  相似文献   
999.
Wan YJ  Zhang YL  Zhou ZR  Jia RX  Li M  Song H  Wang ZY  Wang LZ  Zhang GM  You JH  Wang F 《Theriogenology》2012,78(3):583-592
The objective was to investigate the effects of the transgenic donor cell synchronization method, oocyte sources, and other factors, on production of hLF-gene nucleus transfer dairy goats. Three transfected cell lines from ear biopsies from three 3-mo-old Saanen dairy goats (designated Number 1, Number 2, and Number 3, respectively) were selected as karyoplast donors for somatic cell nuclear transfer (SCNT) after detailed identification (including PCR and sequencing of PCR products). In donor cell cycle synchronization studies, the apoptosis rate of hLF transgenic fibroblasts was not different (P > 0.05) after 3 days of serum starvation or 2 days of contact inhibition. Additionally, there was no effect (P > 0.05) on developmental capacity of reconstructed embryos; however, the kidding rate of recipients in the serum starvation group was higher than that in the contact inhibition group (18 vs. 0%, respectively). The production efficiency of the transgenic cloned goats using donor cells from the Number 1 dairy goat cell line was higher than those using the Number 2 and the Number 3 cell lines (kidding rates were 18, 2, and 0%, respectively, P < 0.05). The oocyte source did not significantly affect the pregnancy rate of hLF-transgenic cloned dairy goats, but more fetuses were aborted when using in vitro matured oocytes compared to in vivo matured oocytes. In summary, utilizing transfected 3-mo-old dairy goat fibroblasts as donor cells, seven live offspring were produced, and the hLF gene was successfully integrated. This study provided additional insights into preparation of donor cells and recipient oocytes for producing transgenic cloned goats through SCNT.  相似文献   
1000.
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