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   3065篇
  免费   199篇
  国内免费   7篇
  2024年   5篇
  2023年   11篇
  2022年   43篇
  2021年   54篇
  2020年   43篇
  2019年   63篇
  2018年   97篇
  2017年   60篇
  2016年   127篇
  2015年   166篇
  2014年   189篇
  2013年   205篇
  2012年   273篇
  2011年   314篇
  2010年   174篇
  2009年   147篇
  2008年   184篇
  2007年   196篇
  2006年   134篇
  2005年   119篇
  2004年   111篇
  2003年   91篇
  2002年   87篇
  2001年   62篇
  2000年   55篇
  1999年   38篇
  1998年   27篇
  1997年   29篇
  1996年   16篇
  1995年   16篇
  1994年   12篇
  1993年   12篇
  1992年   10篇
  1991年   10篇
  1990年   14篇
  1989年   19篇
  1988年   12篇
  1987年   7篇
  1986年   6篇
  1985年   4篇
  1984年   7篇
  1979年   5篇
  1978年   2篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1972年   2篇
  1971年   3篇
  1969年   2篇
  1968年   1篇
排序方式: 共有3271条查询结果,搜索用时 15 毫秒
211.

Background/Objective

There have been several operative techniques for adenoidectomy and their efficacy and morbidity are different according to the technique. This prospective multicenter study was aimed to compare the efficacy and morbidity of coblation adenoidectomy (CA) with those of power-assisted adenoidectomy.

Study Design

Prospective multi-institutional study.

Methods

Children who underwent CA, power-assisted adenoidectomy with cauterization (PAA+C) or without cauterization (PAA-C) due to adenoid hypertrophy were enrolled from 13 hospitals between July 2013 and June 2014. Mean operation time, degree of intraoperative bleeding and postoperative bleeding rate were evaluated.

Results

A total of 388 children (mean age ± standard deviation = 6.6 ± 2.5 years; 245 males and 143 females) were included. According to the adenoidectomy technique, the children were classified into 3 groups: (1) CA (n = 116); (2) PAA+C (n = 153); and (3) PAA-C (n = 119). Significant differences were not found in age and sex among three groups. In the CA group, mean operation time was significantly shorter (P < 0.001) and degree of intraoperative bleeding was significantly less (P < 0.001) compared to PAA+C or PAA-C group. Delayed postoperative bleeding rate of PAA-C group was significantly higher than that of CA or PAA+C group (P = 0.016).

Conclusions

This prospective multicenter study showed that CA was superior to PAA in terms of mean operation time and degree of intraoperative bleeding.  相似文献   
212.
Human sperm have to undergo a maturational process called capacitation in the female reproductive tract. Capacitation confers upon the sperm an ability to gain hypermotility and undergo acrosome reaction. Previous studies have suggested that seminal plasma proteins induce the capacitation of sperm in the female reproductive tract for the successful fertilization of the oocyte. However, the function of seminal plasma proteins in capacitation remains largely unclear. To the end, we found that soluble CD38 (sCD38) in seminal plasma increases the capacitation of sperm via specific interactions between sCD38 and the CD31 on the sperm. Upon the association of sCD38 with CD31, tyrosine kinase Src phosphorylates CD31, a process blocked by Src inhibitors. Shc, SHP-2, Grb2, and SOS, as well as Src kinase were found to associate with the phosphorylated CD31. The sCD38-induced phosphorylation of CD31 initiates a cascade reaction through the phosphorylation of Erk1/2, which results in the acrosome reaction, and sperm hypermotility. These processes were prevented by Src, Ras and MEK inhibitors. Taken together, these data indicate that the sCD38 present in seminal plasma plays a critical role in the capacitation of sperm.  相似文献   
213.

Objective

To evaluate the efficacy and safety of sorafenib for Korean patients with metastatic renal cell carcinoma (mRCC).

Methods

A total of 177 mRCC patients using sorafenib as first- (N = 116), second- (N = 43), and third-line (N = 18) therapies were enrolled from 11 Korean centers between 2006 and 2012. The patient characteristics, therapy duration, tumor response, disease control rate, and tolerability were assessed at baseline and at routine follow-ups, and the progression-free survival (PFS) and overall survival (OS) times and rates were analyzed.

Results

Among all patients, 18 (10.2%) stopped sorafenib treatment for a median of 1.7 weeks, including 15 (8.5%) who discontinued the drug, while 40 (22.6%) and 12 (6.8%) patients required dose reductions and drug interruptions, respectively. Severe adverse events (AEs) or poor compliance was observed in 64 (36.2%) patients, with 118 (7.4%) ≥grade 3 AEs. During the treatment, one myocardial infarction was observed. The number of ≥grade 3 AEs in the first-line sorafenib group was 71 (6.8% of the total 1048 AEs). During a median follow-up of 17.2 months, the radiologically confirmed best objective response rate, disease control rate, median PFS, and median OS were 22.0%, 53.0%, 6.4 months (95% confidence interval [CI], 5.2–8.9), and 32.6 months (95% CI, 27.3–63.8) for the total 177 sorafenib-treated patients, respectively, and 23.2%, 56.0%, 7.4 months (95% CI, 5.5–10.5), and not reached yet (95% CI, 1.0–31.1) for the first-line sorafenib group, respectively.

Conclusions

Sorafenib produced tolerable safety, with a ≥grade 3 AE rate of 7.4% and an acceptable disease control rate (53.0%) in Korean mRCC patients.  相似文献   
214.
Ionizing radiation has different biological effects according to dose and dose rate. In particular, the biological effect of low-dose radiation is unclear. Low-dose whole-body gamma irradiation activates immune responses in several ways. However, the effects and mechanism of low-dose radiation on allergic responses remain poorly understood. Previously, we reported that low-dose ionizing radiation inhibits mediator release in IgE-mediated RBL-2H3 mast cell activation. In this study, to have any physiological relevance, we investigated whether low-dose radiation inhibits allergic responses in activated human mast cells (HMC-1(5C6) and LAD2 cells), mouse models of passive cutaneous anaphylaxis and the late-phase cutaneous response. High-dose radiation induced cell death, but low-dose ionizing radiation of <0.5 Gy did not induce mast cell death. Low-dose ionizing radiation that did not induce cell death significantly suppressed mediator release from human mast cells (HMC-1(5C6) and LAD2 cells) that were activated by antigen-antibody reaction. To determine the inhibitory mechanism of mediator released by low-dose ionizing radiation, we examined the phosphorylation of intracellular signaling molecules such as Lyn, Syk, phospholipase Cγ, and protein kinase C, as well as the intracellular free Ca2+ concentration ([Ca2+]i). The phosphorylation of signaling molecules and [Ca2+]i following stimulation of FcεRI receptors was inhibited by low dose ionizing radiation. In agreement with its in vitro effect, ionizing radiation also significantly inhibited inflammatory cells infiltration, cytokine mRNA expression (TNF-α, IL-4, IL-13), and symptoms of passive cutaneous anaphylaxis reaction and the late-phase cutaneous response in anti-dinitrophenyl IgE-sensitized mice. These results indicate that ionizing radiation inhibits both mast cell-mediated immediate- and delayed-type allergic reactions in vivo and in vitro.  相似文献   
215.
A Gram-negative, strictly aerobic, non-flagellated and rod-shaped bacterial strain, designated MA-E2-3T, was isolated from an ascidian (Halocynthia roretzi) collected from the South Sea, South Korea. Strain MA-E2-3T was found to grow optimally at 30 °C, at pH 7.0–8.0 and in the presence of 2.0–3.0 % (w/v) NaCl. A neighbour-joining phylogenetic tree based on 16S rRNA gene sequences revealed that strain MA-E2-3T fell within the clade comprising Ruegeria species, clustering consistently with the type strain of Ruegeria halocynthiae, with which it exhibited 98.2 % sequence similarity. Sequence similarities to the type strains of the other recognized Ruegeria species were 94.7–97.7 %. Strain MA-E2-3T was found to contain Q-10 as the predominant ubiquinone and C18:1 ω7c as the predominant fatty acid. The major polar lipids of strain MA-E2-3T were identified as phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, one unidentified aminolipid and one unidentified lipid. The DNA G+C content of strain MA-E2-3T was determined to be 58.0 mol%. Mean DNA–DNA relatedness values between strain MA-E2-3T and the type strains of four phylogenetically closely related Ruegeria species were in the range of 13–23 %. The differential phenotypic properties, together with the phylogenetic and genetic distinctiveness, revealed that strain MA-E2-3T is separated from other Ruegeria species. On the basis of the data presented, strain MA-E2-3T (=KCTC 32450T = CECT 8411T) represents a novel species of the genus Ruegeria, for which the name Ruegeria meonggei sp. nov. is proposed.  相似文献   
216.
We recently isolated a polypeptide from the earthworm Lumbricus terrestris that is structurally similar to defensin, a well-known antibacterial peptide. An 11-mer antibacterial peptide (NH2-RNRRWCIDQQA), designated Lumbricusin, was synthesized based on the amino acid sequence of the isolated polypeptide. Since we previously reported that CopA3, a dung beetle peptide, enhanced neuronal cell proliferation, we here examined whether Lumbricusin exerted neurotropic and/or neuroprotective effects. Lumbricusin treatment induced a time-dependent increase (∼51%) in the proliferation of human neuroblastoma SH-SY5Y cells. Lumbricusin also significantly inhibited the apoptosis and decreased viability induced by treatment with 6-hydroxy dopamine, a Parkinson’s disease-mimicking agent. Immunoblot analyses revealed that Lumbricusin treatment increased ubiquitination of p27Kip1 protein, a negative regulator of cell-cycle progression, in SH-SY5Y cells, and markedly promoted its degradation. Notably, adenoviral-mediated over-expression of p27Kip1 significantly blocked the antiapoptotic effect of Lumbricusin in 6-hydroxy dopamine-treated SH-SY5Y cells. These results suggest that promotion of p27Kip1 degradation may be the main mechanism underlying the neuroprotective and neurotropic effects of Lumbricusin.  相似文献   
217.
Matrix metalloproteinases (MMPs) are extracellular matrix (ECM) degrading enzymes and have complex and specific regulation networks. This includes activation interactions, where one MMP family member activates another. ECM degradation and MMP activation can be initiated by several different stimuli including changes in ECM mechanical properties or intracellular contractility. These mechanical stimuli are known enhancers of metastatic potential. MMP-14 facilitates local ECM degradation and is well known as a major mediator of cell migration, angiogenesis and invasion. Recently, function blocking antibodies have been developed to specifically block MMP-14, providing a useful tool for research as well as therapeutic applications. Here we utilize a selective MMP-14 function blocking antibody to delineate the role of MMP-14 as an activator of other MMPs in response to changes in cellular contractility and ECM stiffness. Inhibition using function blocking antibodies reveals that MMP-14 activates soluble MMPs like MMP-2 and -9 under various mechanical stimuli in the pancreatic cancer cell line, Panc-1. In addition, inhibition of MMP-14 abates Panc-1 cell extension into 3D gels to levels seen with non-specific pan-MMP inhibitors at higher concentrations. This strengthens the case for MMP function blocking antibodies as more potent and specific MMP inhibition therapeutics.  相似文献   
218.
219.
220.
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