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   7653篇
  免费   548篇
  国内免费   705篇
  8906篇
  2024年   25篇
  2023年   99篇
  2022年   257篇
  2021年   409篇
  2020年   301篇
  2019年   347篇
  2018年   323篇
  2017年   268篇
  2016年   360篇
  2015年   500篇
  2014年   565篇
  2013年   614篇
  2012年   763篇
  2011年   643篇
  2010年   362篇
  2009年   371篇
  2008年   388篇
  2007年   330篇
  2006年   291篇
  2005年   240篇
  2004年   206篇
  2003年   175篇
  2002年   152篇
  2001年   151篇
  2000年   115篇
  1999年   101篇
  1998年   69篇
  1997年   72篇
  1996年   72篇
  1995年   56篇
  1994年   49篇
  1993年   32篇
  1992年   42篇
  1991年   20篇
  1990年   25篇
  1989年   19篇
  1988年   16篇
  1987年   16篇
  1986年   11篇
  1985年   18篇
  1984年   9篇
  1983年   6篇
  1982年   7篇
  1981年   3篇
  1980年   2篇
  1979年   1篇
  1977年   2篇
  1966年   1篇
  1965年   2篇
排序方式: 共有8906条查询结果,搜索用时 12 毫秒
991.
A recent report showed that reversine treatment could induce murine myoblasts dedifferentiation into multipotent progenitor cells and inhibit proliferation of some tumors, and other reports showed that apoptosis of lung adenocarcinoma cells could be induced by aspirin. The aim of the present study was to evaluate the synergistic antitumor effects of reversine and aspirin on cervical cancer. The inhibition rate of reversine and aspirin on cervical cancer cell lines’ (HeLa and U14) was determined by MTT method, cell cycle of HeLa and U14 cells was analyzed by FACS, mitochondrial membrane potential of HeLa and U14 was detected using a JC-1 kit. HeLa and U14 colony formation was analyzed by soft agar colony formation assay. The expression of caspase-3, Bcl-2/Bax, cyclin D1 and p21 was detected by qRT-PCR and Western Blotting. Moreover, tumor weight and tumor volume was assessed using a murine model of cervical cancer with U14 cells subcutaneously (s.c.) administered into the neck, separately or combined with drug administration via the intraperitoneal (i.p.) route. The inhibition rate of cells in the combination group (10 μmol/L reversine, 10 mmol/L aspirin) increased significantly in comparison to that when the drugs were used alone (P < 0.05); moreover, this combination could synergistically inhibit the proliferation of five cervical cancer cell lines (HeLa, U14, Siha, Caski and C33A). In the therapeutic mouse model, tumor weight and tumor volume of cervical cancer bearing mice was more reduced when compared with the control agents (P < 0.05) in tumor-bearing mice. The combination of reversine and aspirin exerts synergistic growth inhibition and apoptosis induction on cervical cancers cells.  相似文献   
992.
993.
This study compared the ultrastructural differences of term placentae from human pregnancies resulting from assisted reproductive technology (ART) with term placentae from spontaneous human pregnancies. Term placentae were taken from women who had undergone an ART procedure (n = 8) and matched with term placentae from women who had had a spontaneous pregnancy (controls, n = 15). Using light microscopy (LM) and transmission-electron microscopy (TEM), terminal villi were evaluated with respect to the placental blood barrier, fetal capillaries, villous stroma, as well as cytotrophoblasts and syncytiotrophoblasts (ST) along with their substructures. No obvious differences were found between the ART-derived and control placentae when LM was used. With TEM, however, differences in the ultrastructural features were seen in the ART-derived placentae, specifically degenerative alterations of the terminal villi, mainly in ST, including a thicker placental barrier, decreased apical microvilli, and increased multiple vacuoles. The results demonstrate that some ultrastructural differences exist between ART-derived and control placentae with respect to the placental blood barrier, which may suggest maternofetal traffic downregulation following ART treatment. Further studies are required to understand the ultrastructural changes and their potential functional aspects in ART pregnancies.  相似文献   
994.
995.
Flatfish metamorphosis denotes the extraordinary transformation of a symmetric pelagic larva into an asymmetric benthic juvenile. This unique process involves eye migration, a 90° rotation in posture, and asymmetrical pigmentation for adaptation to a benthic lifestyle. In the present study, we used genetics to map a metamorphosis-related locus (q-10M) in the male linkage group (LG10M), a small interval of 0.9 cM corresponding to a 1.8 M-bp physical area in chromosome 9 in the Chinese tongue sole (Cynoglossus semilaevis). Combined with single-marker analysis, ribosomal protein S6 kinase 2 (rps6kb2) a member of the family of AGC kinases was identified as a novel metamorphosis-related candidate gene. Its expression pattern during metamorphosis was determined by quantitative RT-PCR and whole-mount in situ hybridization analysis. rps6kb2 gene was significantly expressed in metamorphic climax stage larvae and distributed in all the tissues transforming during metamorphosis, including tail, jaw, eye and skin of larvae. The results suggest that rps6kb2 has a general role in tissue transformations during flatfish metamorphosis including tail changes, skull remodeling, eye migration, and asymmetrical pigmentation.  相似文献   
996.
997.
每日盐度波动对真盐生植物盐地碱蓬种内相互作用沿盐度梯度的影响 土壤盐度的异质性是河口潮间带的一个突出的环境特征,影响植物的生长和盐沼中生物相互作用的转变。本研究旨在探究盐度梯度和盐度波动对一种真盐生植物的种内相互作用的交互影响。  相似文献   
998.
Eicosanoids are crucial downstream signals in the insect immune responses. Phospholipase A2 (PLA2) catalyzes phospholipids, the initial step in eicosanoid biosynthesis. In mammals, the biological roles of Ca2+-independent Phospholipase A2 (iPLA2) have been extensively studied; however, only a few studies have attempted to explore iPLA2 functions in insects. In this study, we identified two iPLA2 genes (designated as BmiPLA2A and BmiPLA2B) in the silkworm, Bombyx mori. BmiPLA2A had a 2427 base pair (bp) open reading frame (ORF) that coded for a protein with 808 amino acids. In contrast, BmiPLA2B had a 1731 bp ORF that coded for a protein with 576 amino acids. Domain analysis revealed that BmiPLA2A had six ankyrin repeat domains, but BmiPLA2B lacks these domains. BmiPLA2A and BmiPLA2B were transcribed widely in various tissues and developmental stages with different expression patterns. The administration of 20-hydroxyecdysone increased their expression levels in the epidermis and hemocytes. Furthermore, challenged with virus, fungus, Gram-negative bacteria, and Gram-positive bacteria induced the expression of BmiPLA2A and BmiPLA2B with variable degrees along with different time points. Our findings imply that BmiPLA2A and BmiPLA2B may have important biological roles in the development and innate immunity of B. mori.  相似文献   
999.

Background

Despite the availability of multiple treatment strategies, patients with advanced colon carcinoma (CC) have poor prognoses. The aim of this study was to evaluate the efficacy and safety of natural killer (NK) cell therapy in combination with chemotherapy in patients with locally advanced CC.

Methods

We assessed the cytotoxicity of NK cells to CC cells (CCs) and CC stem cells (CSCs) pre-treated with 5-fluorouracil or oxaliplatin in vitro. Then, an open-label cohort study was conducted with locally advanced CC patients who had received radical resection. Patients received either NK cell therapy combined with chemotherapy (NK cell group, 27 patients) or pure chemotherapy (control group, 33 patients). Progression-free survival (PFS), overall survival (OS) and adverse effects were investigated.

Results

Chemotherapy sensitized CCs and CSCs to NK cell cytotoxicity through regulation of NK cell–activating/inhibitory receptor ligands. Poorly differentiated CCs were more susceptible to NK cells than well-differentiated ones. In the cohort study, the 5-year PFS and OS rates in the NK cell group were significantly higher than those in the control group (51.1% versus 35%, P?=?0.044; 72.5% versus 51.6%, P?=?0.037, respectively). Among patients with poorly differentiated carcinomas and low expression of human leukocyte antigen (HLA)-1, the median PFS in the NK cell group versus the control group was 23.5 versus 12.1 months (P?=?0.0475) and 33.1 versus 18.5 months (P?=?0.045), respectively. No significant adverse reactions were reported.

Conclusion

NK cell therapy in combination with chemotherapy in locally advanced CC prevented recurrence and prolonged survival with acceptable adverse effects, especially for poorly differentiated carcinomas.  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