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   7576篇
  免费   347篇
  国内免费   154篇
耳鼻咽喉   27篇
儿科学   115篇
妇产科学   545篇
基础医学   842篇
口腔科学   42篇
临床医学   379篇
内科学   1330篇
皮肤病学   82篇
神经病学   1029篇
特种医学   67篇
外科学   508篇
综合类   473篇
预防医学   135篇
眼科学   58篇
药学   2176篇
中国医学   107篇
肿瘤学   162篇
  2023年   55篇
  2022年   76篇
  2021年   128篇
  2020年   125篇
  2019年   173篇
  2018年   203篇
  2017年   182篇
  2016年   152篇
  2015年   149篇
  2014年   305篇
  2013年   686篇
  2012年   256篇
  2011年   389篇
  2010年   319篇
  2009年   300篇
  2008年   348篇
  2007年   321篇
  2006年   309篇
  2005年   297篇
  2004年   285篇
  2003年   262篇
  2002年   249篇
  2001年   212篇
  2000年   224篇
  1999年   174篇
  1998年   184篇
  1997年   199篇
  1996年   183篇
  1995年   172篇
  1994年   146篇
  1993年   125篇
  1992年   125篇
  1991年   91篇
  1990年   87篇
  1989年   64篇
  1988年   66篇
  1987年   61篇
  1986年   60篇
  1985年   80篇
  1984年   54篇
  1983年   53篇
  1982年   46篇
  1981年   24篇
  1980年   17篇
  1979年   17篇
  1978年   12篇
  1977年   9篇
  1976年   9篇
  1975年   4篇
  1973年   3篇
排序方式: 共有8077条查询结果,搜索用时 15 毫秒
61.
A multicentre, randomized, double-blind, placebo-controlled,parallel-group trial was undertaken in 135 patients to determinewhether 4 weeks of treatment with long-acting nisoldipine coat-core(20 mg once a day) could alter diastolic function in patientswith a recent myocardial infarction and with mild left ventriculardysfunction as indicated by a left ventricular ejection fraction50%. The primary endpoint was the change in diastolic fillingparameters assessed by Doppler and two-dimensional echocardiography. The mean time of admission to the study was 20 days (range 7–35)after myocardial infarction. Mean left ventricular ejectionfraction was 41%. The drug increased early diastolic peak velocityat the tips of the mitral leaflet by 0·06 m . s–1(95% confidence intervals (CI): 0·01, 0·11). Thetime velocity integral was increased by 1·2 cm (95% CI:0·16, 2·27). These findings are indicative ofincreased early diastolic flow across the mitral valve. An importantdeterminant appeared to be a reduced isovolumic relaxation time(by 14·7 ms, 95% CI: -22·5, -6·9). As therewas no change in heart rate, systolic and diastolic blood pressureor cardiac output, after load reduction appeared unlikely asan explanation. Peak workload on exercise was 12 watts higherin the group on nisoldipine (95% CI: 0·8, 23·3).Thus, nisoldipine was shown to improve indices of diastolicventricular function, as well as exercise capacity, in thisgroup of patients. The observed effects of nisoldipine may reflectan anti-ischaemic effect or be due to improved relaxation ofthe myocardium.  相似文献   
62.
Plasma concentrations of metoprolol after acute and repetitive administration of R/S-metoprolol to healthy volunteers were measured by a -adrenoceptor subtype-specific radioreceptor assay (RRA) and by an enantiospecific high-performance liquid chromatographic (HPLC) method. In the RRA, R/S-metoprolol showed a 20-fold 1-subtype selectivity: the S-( – )-enantiomer was 35-fold more potent than the R-( + )-enantiomer. A comparison between S-( – )-metoprolol concentrations detected in the plasma samples by HPLC and those detected by RRA yielded a 1/1 relationship, indicating that active metabolites are not present to a significant extent. These results were independent of the widely scattering metabolic clearance of metoprolol (with the potential of differences in the rate and extent of formation of active metabolites) in the volunteers. In general, HPLC methods can be validated by comparison with RRA in order to clarify whether active metabolites are present and—on the basis of the Ki value from RRA—whether the detection limit of the physicochemical procedure is sufficient to cover the therapeutically relevant range.  相似文献   
63.
BACKGROUND: We aimed to assess the efficacy of a GnRH antagonist in intrauterine insemination (IUI) cycles to increase number of mature ovulatory follicles and pregnancy rates. METHODS: Prospective randomized study. Women (18-38 years old) with primary/secondary infertility were included. Eighty-two patients were randomly assigned to controlled ovarian stimulation (COS) consisting of rFSH + GnRH antagonist or rFSH alone. RESULTS: A non-significant increase in the total amount of rFSH was seen in the GnRH antagonist group (707+/-240 IU) with respect to the control group (657+/-194 IU). The number of mature follicles (> or =16 mm) was significantly higher in the GnRH antagonist group than in the control group (2.4+/-1.4 versus 1.7+/-1.2, P<0.05). Pregnancy rates were significantly increased in the group of patients receiving the GnRH antagonist (38%) compared to the control group (14%). The only non-single pregnancy (triplets) occurred in the antagonist group. CONCLUSIONS: In this preliminary study, adding the GnRH antagonist to the COS protocol for IUI cycles significantly increased pregnancy rates. Nevertheless, these results may not be associated directly with the antagonist itself but with the fact that more mature ovulatory follicles are present by the day of the hCG. Finally, the risk for multiple gestations needs to be carefully evaluated.  相似文献   
64.
65.
背景:陶瓷材料因具有优良的机械性能、与口腔组织良好的生物相容性及高度美观性广泛应用于口腔修复领域,良好的磨损性能对修复体临床应用有重要意义。目的:综述口腔修复陶瓷材料磨损性能机制及临床研究,以期为临床选择适宜的陶瓷材料提供思路。方法:应用计算机在PubMed和Web of Science数据库检索在2016年1月至2021年4月期间涉及口腔修复陶瓷材料磨损性能的相关研究。英文检索词为“dental ceramic material,wear property”,最终共纳入36篇文献进行分析。结果与结论:①全瓷材料自身耐磨性均高于树脂陶瓷复合材料,全瓷材料中氧化锆陶瓷磨损性能最佳,美学性能较弱。②玻璃陶瓷中氧化锆加强型硅酸锂玻璃陶瓷磨损性能较好,但应用时间较短,长期疗效还有待更多的研究证实。③树脂陶瓷复合材料中树脂纳米陶瓷材料磨损性能优于聚合物渗透陶瓷。④在后牙区全冠修复可选择氧化锆陶瓷,前牙区全冠修复可以根据患者的美学需求选择高透性氧化锆陶瓷或玻璃陶瓷。⑤贴面、嵌体和高嵌体修复可选择长石瓷、玻璃陶瓷和树脂陶瓷复合材料,但树脂陶瓷复合材料耐磨性差,需避免用于高应力承载区。⑥对牙本质暴露、氟斑牙和牙齿酸蚀症患者可考虑树脂纳米陶瓷材料,但这类患者适宜的陶瓷材料相关研究较少。⑦表面粗糙度对陶瓷材料的磨损性能有显著影响,临床口腔修复应用中采用良好的抛光表面可提高陶瓷材料磨损性能,而且对修复体进行定期复查也至关重要。  相似文献   
66.
Journal of Clinical Immunology - The objective of this study was to characterize interleukin-1 receptor antagonist (IL-1ra) and interleukin-1β (IL-1β) production by human peripheral blood...  相似文献   
67.
68.
Ovulation induction is the method for treating anovulatory infertility. For patients with hypogonadotrophic hypogonadism, the treatment involves administration of both FSH and LH, while HCG is injected for follicle rupture. Pulsatile GnRH has the same effectiveness as gonadotrophins and the advantage of the low multiple pregnancy rate. In polycystic ovary syndrome (PCOS), the first treatment choice is clomiphene citrate. With this drug, in properly selected patients, the cumulative pregnancy rate approaches that of normal women. Low-dose protocols of FSH are the second line of treatment, effective in inducing monofollicular development. Laparoscopic ovarian drilling can be an alternative but not as a first choice treatment in clomiphene-resistant patients. Other treatments, such as pulsatile GnRH and GnRH agonists, are hardly used today in PCOS. However, in obese women with PCOS, weight loss and exercise should be recommended as the first line of therapy. Newer agents including aromatase inhibitors and insulin sensitizers, although promising, need further evaluation.  相似文献   
69.
The chemokine receptors CCR5 and CXCR4 are an obvious target for HIV therapies. Two compounds, T-22 and AMD-3100, have been shown to inhibit infection of CXCR4-using HIV-1 isolates. The specificity of T-22 and AMD-3100 was further confirmed by their ability to block entry of HIV-1 in GHOST-CXCR4 transfected cells with no effect on viral entry in the GHOST-CCR5 cells. The ability of T-22 to block replication of diverse HIV-1 isolates (group M, subtypes A, B, D, E, and F as well as group O) and HIV-2 primary isolates with varying coreceptor specificities ranging from exclusive CCR5 usage to multiple coreceptor usage was examined in detail. T-22 was found to be highly effective (>90%) at blocking infection of diverse HIV-1 (subtypes A-F, and group O) and HIV-2 isolates that use multiple coreceptors in human PBMCs homozygous for a 32-bp deletion in CCR5 (CCR5-/-), but less effective in CCR5 +/+ PBMCs. Additionally, sequential primary HIV-1 isolates obtained from a longitudinal cohort who had switched from single coreceptor usage to a broad range of multiple receptors could be blocked effectively by both T-22 and AMD-3100 in CCR5-/- PBMCs. Our data suggest that CXCR4 antagonistic compounds are highly effective in blocking the entry of X4-tropic HIV-1, and that these compounds could be a useful additive to current anti-retroviral therapy for clinical management of HIV disease.  相似文献   
70.
Intravenous immunoglobulin (IVIG) is increasingly being used for the treatment of autoimmune diseases. In the present report, the role of IVIG on in vivo and in vitro production of IL-1 and IL-1 receptor antagonist (Ra) was studied in patients with pemphigus vulgaris (PV). Serum samples from 20 untreated patients with active PV prior to initiation of systemic therapy, 20 patients receiving IVIG treatment, 20 patients in clinical remission after conventional therapy, and 20 normal human controls were studied to determine the serum levels of IL-1alpha, IL-1beta, and IL-1Ra. The in vitro production of these cytokines was measured in the culture supernatant of peripheral blood mononuclear cells (PBMC) from 10 PV patients immediately before and after IVIG therapy and from age and sex-matched 10 healthy donors simultaneously. Elevated levels of IL-1alpha and IL-1beta were detected (i) in the serum of untreated PV patients with active disease prior to systemic therapy and (ii) before IVIG infusions in patients receiving IVIG therapy. These increased levels are statistically significant when compared to the levels in healthy controls (P < 0.01). A marked reduction of IL-1alpha and IL-1beta was detected (i) in the serum of patients in prolonged clinical remission and (ii) immediately after IVIG infusion in those patients on IVIG therapy. Increased level of IL-1Ra was detected in PV patients in prolonged clinical remission and after IVIG infusion in those receiving IVIG therapy. These differences were statistically significant when compared to the levels in normal controls and to the levels in the sera of patients with active disease (P < 0.01) or just before the beginning of IVIG infusion (P < 0.01). Similar differences in the levels of IL-1alpha, IL-1beta, and IL-1Ra were found in the culture supernatant of PBMC isolated from the PV patients pre and post IVIG therapy. These observations suggests that, compared to normal controls, patients with active PV have reversed levels of IL-1alpha, IL-1beta, and IL-1Ra. IVIG therapy may down-regulate production of IL-1alpha and IL-1beta and enhance production of IL-1Ra, in vivo and in vitro. This might be one of the important mechanisms by which IVIG produces its early therapeutic effects in pemphigus vulgaris.  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