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   15883篇
  免费   1303篇
  国内免费   491篇
耳鼻咽喉   172篇
儿科学   285篇
妇产科学   376篇
基础医学   2086篇
口腔科学   323篇
临床医学   1852篇
内科学   2881篇
皮肤病学   308篇
神经病学   1080篇
特种医学   641篇
外国民族医学   3篇
外科学   1932篇
综合类   1148篇
一般理论   2篇
预防医学   1029篇
眼科学   442篇
药学   1397篇
  4篇
中国医学   335篇
肿瘤学   1381篇
  2024年   30篇
  2023年   170篇
  2022年   415篇
  2021年   595篇
  2020年   320篇
  2019年   430篇
  2018年   425篇
  2017年   376篇
  2016年   388篇
  2015年   539篇
  2014年   633篇
  2013年   691篇
  2012年   1131篇
  2011年   1199篇
  2010年   715篇
  2009年   596篇
  2008年   872篇
  2007年   847篇
  2006年   817篇
  2005年   767篇
  2004年   693篇
  2003年   596篇
  2002年   519篇
  2001年   464篇
  2000年   400篇
  1999年   396篇
  1998年   151篇
  1997年   151篇
  1996年   176篇
  1995年   146篇
  1994年   108篇
  1993年   86篇
  1992年   195篇
  1991年   182篇
  1990年   156篇
  1989年   134篇
  1988年   128篇
  1987年   107篇
  1986年   105篇
  1985年   103篇
  1984年   77篇
  1983年   70篇
  1982年   56篇
  1981年   55篇
  1980年   47篇
  1979年   60篇
  1978年   50篇
  1977年   33篇
  1975年   27篇
  1974年   43篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Dietary polyphenols, including anthocyanins, are suggested to be involved in the protective effects of fruits and vegetables against cancer. However, anticancer effects of peonidin 3-glucoside have not been clearly demonstrated, with only limited studies being available concerning the inhibitory effect of cyanidin 3-glucoside for tumor cell growth. Therefore, in this study, we have isolated and identified the two bioactive compounds, peonidin 3-glucoside and cyanidin 3-glucoside, from Oryza sativa L. indica, to treat various cancer cells. The results showed that, among analyzed cell lines, HS578T was the most sensitive to peonidin 3-glucoside and cyanidin 3-glucoside. Treatment with peonidin 3-glucoside or cyanidin 3-glucoside resulted in a strong inhibitory effect on cell growth via G2/M arrest. Regarding cell cyclerelated proteins, peonidin 3-glucoside treatment resulted in down-regulation of protein levels of cyclin-dependent kinase (CDK)-1, CDK-2, cyclin B1, and cyclin E, whereas cyanidin 3-glucoside could decrease the protein levels of CDK-1, CDK-2, cyclin B1, and cyclin D1. In addition, cyanidin 3-glucoside or peonidin 3-glucoside also induced caspase-3 activation, chromatin condensation, and cell death. Furthermore, anthocyanins from O. sativa L. indica were evidenced by their inhibition on the growth of Lewis lung carcinoma cells in vivo.  相似文献   
992.
BACKGROUND: Sparse published data exist on outcomes in daclizumab-treated cardiac transplant patients. One trial observed an increased mortality risk 6 and 12 months posttransplant in patients receiving daclizumab plus mycophenolate mofetil (MMF), cyclosporine, and steroids. This study further investigates the safety profile of daclizumab with this same immunosuppressive regimen from a large registry. METHODS: Data obtained at hospital discharge on all adult cardiac transplants performed in the USA between January 1998 and October 2003 for patients receiving MMF plus cyclosporine and steroids were accessed from the Scientific Registry of Transplant Recipients. Patients were selected based on induction treatment: daclizumab (n = 684) or no induction (n = 2525). Outcomes were evaluated at 6 months, 12 months, and 3 years posttransplant. Univariate Kaplan-Meier and multivariate Cox models were used to evaluate the effect of treatment on outcomes. Patient survival and infectious death were the primary endpoints. Secondary endpoints included rejection within the first year posttransplant (acute rejection; AR) and total rejection episodes over time. The two treatment groups shared similar demographics and transplant procedure details. RESULTS: Daclizumab (vs no induction) patients had no increased risk of patient death nor infectious death. Daclizumab patients had a lower incidence of AR at 6 months (P = .005) and 12 months (P < .001); the adjusted risk for AR at 12 months (hazards ratio [HR] = 0.77; P = .89) and over 3 years (HR 0.83, P = .006) was also lower in daclizumab-treated patients. CONCLUSIONS: In cardiac transplant patients, daclizumab (vs no induction) does not result in increased mortality or infectious death, and is associated with a lower incidence of AR.  相似文献   
993.
BACKGROUND: There is an increased rate of apoptosis of peripheral blood mononuclear cells (PBMCs) in patients undergoing hemodialysis (HD), but little is known about how different dialysis membranes may contribute to the process. We, therefore, studied the influence of two different dialysis membranes on apoptotic markers during HD. METHODS: 8 healthy controls and 8 patients on regular HD 3 times per week were enrolled in this cross-controlled study. Patients received HD using polysulfone and then regenerated cellulose dialysis membranes for one week each, sequentially. Serum was collected for C-reactive protein (CRP) detection; flow cytometry with dual antibody staining was used to measure the apoptotic markers Fas (CD95), FasL (CD 178) and TNF-R2 (CD120b) in T cells (CD3+), B cells (CD19+), and monocytes (CD14+) at 0, 15, 120 and 240 min after starting HD. We also measured total leukocyte numbers and differential white cell counts. RESULTS: Hemodialysis patients revealed lymphocytopenia, monocytopenia, higher CRP levels and higher Fas and TNF-R2 expression on lymphocytes and monocytes at baseline when compared with normal controls. Leukocyte numbers, including neutrophils, lymphocytes and monocytes, dropped significantly after 15 min of dialysis. There were no significant differences in Fas levels during hemodialysis on T and B lymphocytes or on monocytes. T lymphocyte FasL (CD 178) levels remained unchanged throughout the process. There was a significantly lower overall level of CD120b at 15 min of HD, whereas this marker was higher on monocytes after dialysis. There were no significant differences in the levels of apoptotic markers between the two membranes. CONCLUSION: Our results suggest that uremia itself contributes to PBMC apoptosis. The two different dialysis membranes used in this study did not influence apoptotic markers on PBMCs significantly, but increased TNF-R2 expression on monocytes during a single dialysis session.  相似文献   
994.
Chu XX  Hou M  Zhu YY  Peng J  Ji XB  Zhang F  Wang L 《中华医学杂志》2005,85(49):3464-3468
目的研究特发性血小板减少性紫癜(ITP)患者血小板膜糖蛋白(GP)特异性IgG抗体及其片段的免疫活性及对血小板聚集功能的影响.方法用改良单克隆抗体特异性俘获血小板抗原技术(MAIPA)检测84例慢性ITP患者血浆中抗GPⅡb/Ⅲa、GPⅠb/Ⅸ及GPⅥ自身抗体,比浊法血小板聚集试验筛选出自身抗体阳性并能抑制血小板聚集的患者,用蛋白A柱纯化其血浆IgG抗体并用胃蛋白酶制备F(ab')2片段.检测纯化的IgG抗体及其酶切片段与血小板GP的结合活性及对正常人血小板聚集功能的影响.结果 (1)84例ITP患者血浆中,48例(57.1%)抗GPⅡb/Ⅲa和/或GPⅠb/Ⅸ和/或GPⅥ自身抗体阳性,其中7例(14.6%)明显抑制了二磷酸腺苷、瑞斯托霉素或胶原诱导的血小板聚集;(2)纯化的IgG及F(ab')2片段具有与相应血小板GP的结合活性;(3)4例患者纯化IgG及F(ab')2片段具有抑制血小板聚集的功能.结论 F(ab')2片段是IgG自身抗体的功能片段,它不但保留了良好的抗原结合活性且可部分抑制血小板聚集功能,为人源化血小板糖蛋白特异性抗体的制备奠定了基础.  相似文献   
995.
OBJECTIVES: Although endoscopic totally extraperitoneal inguinal hernioplasty (TEP) confers superior early outcomes compared to those of open repair, the requirement of general anesthesia has been held as an argument against the application of TEP by opponents of laparoscopic surgery. To date, the literature on TEP performed under spinal anesthesia remains scarce. The present study reports our early experience performing TEP under spinal anesthesia in selected patients who were medically unfit for general anesthesia. METHODS: Between March 2003 and March 2004, 6 male patients underwent attempted TEP under spinal anesthesia. Selection criteria for the procedure included reducibility of the inguinal hernia and concomitant medical conditions precluding general aesthesia, such as impaired lung function. Informed consent was obtained in all patients. RESULTS: All patients were conscious and able to communicate verbally during the operation. TEP was successfully completed in 4 patients, with a mean operative time of 33 minutes. All 4 patients were asymptomatic and experienced no pain throughout the procedure. Conversion to open repair was required in 2 patients because of uncooperative movement in one, and inadequate neural blockade by spinal anesthesia in the other. Intraoperative cardiorespiratory parameters were stable in all patients. Postoperative urinary retention occurred in 1 patient. The mean length of follow-up exceeded 3 months, and no seroma or recurrence was detected clinically. CONCLUSION: Successful performance of TEP under spinal anesthesia requires the combined efforts of an experienced anesthesiologist, a skilled surgeon, and a cooperative patient. Our initial experience of TEP under spinal anesthesia appeared promising. TEP under spinal anesthesia may have a role in selected patients who are medically unfit for general anesthesia but are otherwise suitable for TEP.  相似文献   
996.
We report a child with a retained welded tracheal stent scheduled for removal developing refractory bradycardia and cardiac arrest during attempt to remove the stent. Cardiac massage and pacing were necessary to reestablish circulation. The same type of arrhythmia occurred three times in the postanesthetic care unit after tracheal suction or coughing.  相似文献   
997.
BACKGROUND: Avascular necrosis (AVN) of the femoral head is perceived to be a rare complication of short-term steroid therapy for neurosurgical conditions but its precise risk is unknown. METHODS: Retrospective review of hospital records between 1994 and 2001. RESULTS: The risk of developing AVN of the femoral head is 0.3% with an incidence of one per one thousand patients per year. CONCLUSIONS: It would be advisable to minimize both the dosage and the duration of steroid treatment where possible.  相似文献   
998.
999.
BACKGROUND: The Hispanic population is increasing and heterogeneous (Hispanic refers to persons of Spanish, Hispanic, or Latino descent). The objective was to examine immunization rates among Hispanic ancestry for the 4:3:1:3:3 series (> or = 4 doses diphtheria, tetanus toxoids, and pertussis vaccine; > or = 3 doses poliovirus vaccine; > or = 1 doses measles-containing vaccine; > or = 3 doses Haemophilus influenzae type b vaccine; and > or = 3 doses hepatitis B vaccine). METHODS: The National Immunization Survey measures immunization coverage among 19- to 35-month-old U.S. children. Coverage was compared from combined 2001-2003 data among Hispanics and non-Hispanic whites using t-tests, and among Hispanic ancestry using a chi-square test. Hispanics were categorized as Mexican, Mexican American, Central American, South American, Puerto Rican, Cuban, Spanish Caribbean (primarily Dominican Republic), other, and multiple ancestry. RESULTS: Children of Hispanic ancestry increased from 21% in 1999 to 25% in 2003. These Hispanic children were less well immunized than non-Hispanic whites (77.0%, +/-2.1% [95% confidence interval] compared to 82.5%, +/-1.1% (95% CI) > in 2003). Immunization coverage did not vary significantly among Hispanics of varying ancestries (p=0.26); however, there was substantial geographic variability. In some areas, immunization coverage among Hispanics was significantly higher than non-Hispanic whites. CONCLUSIONS: Hispanic children were less well immunized than non-Hispanic whites; however, coverage varied notably by geographic area. Although a chi-square test found no significant differences in coverage among Hispanic ancestries, the range of coverage, 79.2%, +/-5.1% for Cuban Americans to 72.1%, +/-2.4% for Mexican descent, may suggest a need for improved and more localized monitoring among Hispanic communities.  相似文献   
1000.
Chu NF  Shen MH  Wu DM  Lai CJ 《Obesity research》2005,13(11):2014-2020
OBJECTIVE: Adiponectin, a novel adipokine with antiinflammatory and insulin-sensitizing properties, has an important role in glucose metabolism and is negatively correlated with body fat amount in adults. The purpose of this study was to evaluate the association of plasma adiponectin level with metabolic risk profiles and insulin resistance status among Taiwanese children. RESEARCH METHODS AND PROCEDURES: We enrolled 1,248 children (608 boys and 640 girls) to ascertain their demographic, anthropometric, and cardiovascular risk factors distribution in Taipei. We measured plasma insulin, adiponectin, and leptin levels by radioimmunoassay (Linco Research Inc, St. Charles, MO). We calculated an insulin resistance index (IRI) using the Homeostasis Model Assessment model and also calculated an insulin resistance syndrome (IRS) summary score for each individual by adding the quartile ranks from the distribution of systolic blood pressure, serum triglyceride, high-density lipoprotein-cholesterol (HDL-C) (inverse), and insulin levels. RESULTS: In general, the boys had larger BMI, higher systolic blood pressure, serum total cholesterol, and triglyceride, and lower plasma leptin and adiponectin levels than girls. Plasma adiponectin levels were correlated negatively with BMI, leptin, insulin, IRI, and IRS summary score but positively correlated with HDL-C in both boys and girls. In multivariate regression analyses, adiponectin was negatively associated with insulin (girls only), IRI (girls only), and IRS score, and positively associated with HDL-C in both genders even after adjusting for age, BMI, plasma leptin level, and other potential confounders. DISCUSSION: These data suggest that plasma adiponectin levels were negatively associated with metabolic risk profiles that may have played a protective role in the development of insulin resistance among Taiwanese school children.  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