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   7635篇
  免费   540篇
  国内免费   714篇
  8889篇
  2024年   27篇
  2023年   100篇
  2022年   259篇
  2021年   409篇
  2020年   303篇
  2019年   349篇
  2018年   323篇
  2017年   267篇
  2016年   358篇
  2015年   500篇
  2014年   562篇
  2013年   612篇
  2012年   764篇
  2011年   644篇
  2010年   363篇
  2009年   366篇
  2008年   390篇
  2007年   328篇
  2006年   288篇
  2005年   238篇
  2004年   206篇
  2003年   175篇
  2002年   152篇
  2001年   151篇
  2000年   115篇
  1999年   100篇
  1998年   68篇
  1997年   71篇
  1996年   71篇
  1995年   54篇
  1994年   49篇
  1993年   31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   5篇
  1981年   3篇
  1980年   2篇
  1979年   1篇
  1966年   1篇
  1965年   2篇
排序方式: 共有8889条查询结果,搜索用时 0 毫秒
51.
52.
Abstract

Background: Platinum compounds are commonly used for lung cancer treatment. However, the severe side effects and relatively poor prognosis limit their therapeutic effect. Therefore, developing novel platinum derivative and treatment strategy are critical for current lung cancer therapy.

Methods: Flow cytometry, HMGB1 and ATP release, and immunoblotting were performed to evaluate the Oxaliplatin-induced immunogenic cell death (ICD) in two lung carcinoma cells. Vaccination approach and subcutaneous tumor models were created to analyze the tumor regression effect of Oxaliplatin. PD-L1 mRNA and protein levels were detected in LLC (Lewis lung carcinoma). Enhanced therapeutic efficacy of LLC was assessed by co-administration Oxaliplatin and aPD-L1 in murine lung tumor model.

Results: Oxaliplatin induced robust ICD in LLC cells, activated dendritic cells (DCs, CD80+CD86+) and enhanced cytotoxic T cells (CD8+) in LLC tumor tissues, which resulted in tumor regression. Co-administration of Oxaliplatin and checkpoint inhibitor, aPD-L1, could enhance the therapeutic efficacy of LLC in murine lung carcinoma.

Conclusion: This study reveals Oxaliplatin can induce robust ICD in tumor tissues and suppress tumor growth by activating DCs and enhancing T-cell infiltration. Notably, the Oxaliplatin-induced ICD provides an immunogenic microenvironment, which enhances the checkpoint inhibitor therapeutic efficacy of LLC.  相似文献   
53.
54.
Dickkopf-1 (DKK1) is an inhibitor of the Wnt/β-catenin signaling pathway. However, the role of DKK1 in the progression of non small cell lung cancer (NSCLC) is not fully understood. In this study, RT-PCR and Western blot were used to examine the expression of DKK1 in a panel of ten human NSCLC cell lines and NSCLC tissues. DKK1 expression was highly transactivated in the great majority of these cancer lines. The expression of DKK1 was upregulated on both mRNA and protein levels in NSCLC tissues compared with the adjacent normal lung tissues. Immunohistochemistry and immunofluoresence revealed that DKK1 was mainly distributed in the cytoplasm in both carcinoma tissues and cell lines. DKK1 protein expression was also evaluated in paraffin sections from 102 patients with NSCLC by immunohistochemistry, and 65(63.73%)tumors were DKK1 positive. Relative analysis showed a significant relationship between DKK1 positive expression and lymph node metastasis(P<0.05). Patients with DKK1-positive tumors had poorer DFS than those with negative ESCC (5-year DFS; 15.4% versus 27%, P = 0.007). To further explore the biological effects of DKK1 in NSCLC cells, we over-expressed DKK1 in NSCLC 95C cell using eukaryotic expression vector pCMV-Tab-2b and performed a knockdown of DKK1 in LTEP-a-2 cell using a short hairpin RNA expression vector pSilencer 5.1. DKK1 did not have any effect on proliferation, but seemed to play a role in migration and invasion capability. Overexpression of DKK1 promotes migratory and invasive activity of 95C, while DKK1 knockdown resulted in the suppression of migration and invasion potentials of LTEP-a-2 cell. Taken together, these results indicate that DKK1 may be a crucial regulator in the progression of NSCLC. DKK1 might be a potential therapeutic target in NSCLC.  相似文献   
55.
This study aims to evaluate the effects of Remifemin (isopropanolic extract of Cimicifuga Racemosa) on postmenopausal osteoporosis. 120 female Sprague-Dawley rats were randomly assigned to four groups: sham surgery with vehicle, ovariectomy with vehicle, ovariectomy with estradiol valerate, or ovariectomy with Remifemin. Daily oral administrations of the vehicle, estradiol valerate, or Remifemin began 2 weeks after surgery and lasted to 4, 8, or 12 weeks. Ten rats in each group were sacrificed at each timestep with assessment of bone mineral density, trabecular bone structure, and biomechanical parameters of the femur and lumbar vertebra. Bone turnover markers were evaluated 12 weeks after surgery. Both drugs prevented bone density loss in the distal end of the femur and preserved the trabecular bone structure in both the lumbar vertebra and distal end of the femur following ovariectomy. Both drugs protected bone stiffness at the tested regions and reduced bone reabsorption in ovariectomized rats. The preventive effects of Remifemin against bone-loss can rival those of estradiol valerate if treatment duration is adequately extended. In conclusion, Remifemin may demonstrate equivalent effects to estradiol valerate in terms of preventing postmenopausal osteoporosis.  相似文献   
56.
Male sterility induced by a chemical hybridization agent (CHA) is an important tool for utilizing crop heterosis. Monosulphuron ester sodium (MES), a new acetolactate synthase-inhibitor herbicide belonging to the sulphonylurea family, has been developed as an effective CHA to induce male sterility in rapeseed (Brassica napus L.). To understand MES-induced male sterility in rapeseed better, comparative cytological and proteomic analyses were conducted in this study. Cytological analysis indicated that defective tapetal cells and abnormal microspores were gradually generated in the developing anthers of MES-treated plants at various development stages, resulting in unviable microspores and male sterility. A total of 141 differentially expressed proteins between the MES-treated and control plants were revealed, and 131 of them were further identified by MALDI-TOF/TOF MS. Most of these proteins decreased in abundance in tissues of MES-treated rapeseed plants, and only a few increased. Notably, some proteins were absent or induced in developing anthers after MES treatment. These proteins were involved in several processes that may be crucial for tapetum and microspore development. Down-regulation of these proteins may disrupt the coordination of developmental and metabolic processes, resulting in defective tapetum and abnormal microspores that lead to male sterility in MES-treated plants. Accordingly, a simple model of CHA-MES-induced male sterility in rapeseed was established. This study is the first cytological and dynamic proteomic investigation on CHA-MES-induced male sterility in rapeseed, and the results provide new insights into the molecular events of male sterility.  相似文献   
57.

Background

With a wide range of applications, titanium dioxide (TiO2) nanoparticles (NPs) are manufactured worldwide in large quantities. Recently, in the field of nanomedicine, intravenous injection of TiO2 nanoparticulate carriers directly into the bloodstream has raised public concerns on their toxicity to humans.

Methods

In this study, mice were injected intravenously with a single dose of TiO2 NPs at varying dose levels (0, 140, 300, 645, or 1387 mg/kg). Animal mortality, blood biochemistry, hematology, genotoxicity and histopathology were investigated 14 days after treatment.

Results

Death of mice in the highest dose (1387 mg/kg) group was observed at day two after TiO2 NPs injection. At day 7, acute toxicity symptoms, such as decreased physical activity and decreased intake of food and water, were observed in the highest dose group. Hematological analysis and the micronucleus test showed no significant acute hematological or genetic toxicity except an increase in the white blood cell (WBC) count among mice 645 mg/kg dose group. However, the spleen of the mice showed significantly higher tissue weight/body weight (BW) coefficients, and lower liver and kidney coefficients in the TiO2 NPs treated mice compared to control. The biochemical parameters and histological tissue sections indicated that TiO2 NPs treatment could induce different degrees of damage in the brain, lung, spleen, liver and kidneys. However, no pathological effects were observed in the heart in TiO2 NPs treated mice.

Conclusions

Intravenous injection of TiO2 NPs at high doses in mice could cause acute toxicity effects in the brain, lung, spleen, liver, and kidney. No significant hematological or genetic toxicity was observed.  相似文献   
58.
A meta-analysis was performed to assess the association between the PAI-1 -675 4G/5G polymorphism and susceptibility to diabetes mellitus (DM), diabetic nephropathy (DN), diabetic retinopathy (DR) and diabetic coronary artery disease (CAD). A literature-based search was conducted to identify all relevant studies. The fixed or random effect pooled measure was calculated mainly at the allele level to determine heterogeneity bias among studies. Further stratified analyses and sensitivity analyses were also performed. Publication bias was examined by the modified Begg’s and Egger’s test. Twenty published articles with twenty-seven outcomes were included in the meta-analysis: 6 studies with a total of 1,333 cases and 3,011 controls were analyzed for the PAI-1 -675 4G/5G polymorphism with diabetes risk, 7 studies with 1,060 cases and 1,139 controls for DN risk, 10 studies with 1,327 cases and 1,557 controls for DR and 4 studies with 610 cases and 1,042 controls for diabetic CAD risk respectively. Using allelic comparison (4G vs. 5G), the PAI-1 -675 4G/5G polymorphism was observed to have no significant association with diabetes (REM OR 1.07, 95% CI 0.96, 1.20), DN (REM OR 1.10, 95% CI 0.98, 1.25), DR (REM OR 1.09, 95% CI 0.97, 1.22) or diabetic CAD risk (REM OR 1.07, 95% CI 0.81, 1.42), and similar results were obtained in the dominant, recessive and co-dominant models. Our meta-analyses suggest that the PAI-1 -675 4G/5G polymorphism might not be a risk factor for DM, DN, DR or diabetic CAD risk in the populations investigated. This conclusion warrants confirmation by further studies.  相似文献   
59.
Fomitopsis cana sp. nov. and F. subtropica sp. nov. are described from southern China based on morphological and molecular characters. Both species have annual, effused-reflexed basidiomata with several small imbricate pilei protruding from a large resupinate part. F. cana is characterized by its mouse-grey to dark grey basidiomata, pores 5–8 per mm, and small cylindrical to oblong-ellipsoid basidiospores (5–6.2?×?2.1–3 μm). F. subtropica is characterized by its white, cream, straw-yellow to more or less flesh-pink basidiomata which was easily separable from the substrate, smaller pores (6–9 per mm) and smaller basidiospores (3.2–4?×?1.8–2.1 μm), and presence of yellowish oil-like substances in trama. Phylogenetic analysis based on combined ITS and nLSU sequences suggest that the two new species belong in the Fomitopsis sensu stricto group within the Antrodia clade.  相似文献   
60.
Covalently bound lipids cover the wool surface and make enzymatic degradation of wool scales very difficult. In this paper, methanolic potassium hydroxide (MPH) pretreatment was used prior to enzymatic treatment of wool with protease, aiming at hydrolyzing the outmost lipids on the wool surface and promoting the subsequent proteolytic reaction. The efficacy of lipid removal from the fiber surface and the properties of the protease‐treated wool were evaluated. The results indicated that mild MPH pretreatment with 0.10 mol/L MPH for 10 min improved the wettability of the wool without adverse impacts on its mechanical properties. The wetting time and area shrinkage of the wool fabric reached 0.5 s and 5.6%, respectively, and the strength loss was within the acceptable range. Pretreatment with high concentrations of MPH for longer times led to significant damage to the wool fibers and caused heavy strength loss, without improving the antifelting properties after protease treatment. Thus, the combination of mild MPH and protease treatments endowed the wool with desirable properties in contrast to the treatment with protease alone.  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