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   616篇
  免费   11篇
  国内免费   3篇
儿科学   16篇
妇产科学   239篇
基础医学   75篇
临床医学   26篇
内科学   62篇
皮肤病学   1篇
神经病学   4篇
特种医学   2篇
外科学   68篇
综合类   44篇
预防医学   38篇
药学   38篇
肿瘤学   17篇
  2024年   1篇
  2022年   3篇
  2021年   2篇
  2020年   9篇
  2019年   9篇
  2018年   15篇
  2017年   12篇
  2016年   15篇
  2015年   8篇
  2014年   35篇
  2013年   54篇
  2012年   21篇
  2011年   29篇
  2010年   27篇
  2009年   13篇
  2008年   24篇
  2007年   24篇
  2006年   21篇
  2005年   28篇
  2004年   28篇
  2003年   24篇
  2002年   14篇
  2001年   7篇
  2000年   15篇
  1999年   13篇
  1998年   5篇
  1997年   11篇
  1996年   11篇
  1995年   9篇
  1994年   8篇
  1993年   8篇
  1992年   8篇
  1991年   9篇
  1990年   8篇
  1989年   9篇
  1988年   10篇
  1987年   5篇
  1986年   3篇
  1985年   16篇
  1984年   12篇
  1983年   11篇
  1982年   7篇
  1981年   9篇
  1980年   6篇
  1979年   7篇
  1978年   4篇
  1977年   2篇
  1976年   1篇
排序方式: 共有630条查询结果,搜索用时 31 毫秒
1.
Using JEG-3 and BeWo cells, we examined the effect of “real life” mixtures of polycyclic aromatic hydrocarbons (PAHs), at doses reported in maternal blood (Mix I) and in placental tissue (Mix II), on human chorionic gonadotropin (hCG), placental lactogen (hPL) and placental growth factor (hPLGF) secretion, protein expression and immunolocalization. Additionally, the action of PAH mixtures on basal and hormone-stimulated matrix metalloproteinase-2 (MMP-2), MMP-9 and vascular endothelial growth factor (VEGF) protein expression was evaluated. Under basal conditions, the PAH mixtures increased hCG and decreased hPLGF levels in both cell lines, while hPL expression was stimulated in JEG-3 and inhibited in BeWo. There was no effect on the MMP-2/MMP-9 ratio or VEGF expression. In hormone-stimulated cells, PAH mixtures changed the MMP-2/MMP-9 ratio in JEG-3 cells in favor of MMP-9, while in BeWo MMP-2 was favored. The effect on VEGF expression was cell specific and dependent on the mixture. In hCG-treated cells, only Mix II inhibited VEGF expression in JEG-3 cells. Neither PAH mixtures affected this protein in BeWo cells. In hPL-treated cells, Mix I had a stimulatory effect in JEG-3 cells, while Mix II exerted an inhibitory effect in BeWo cells. In hPLGF-treated cells, Mix II decreased in JEG-3 cells, but in BeWo cells, both mixtures increased VEGF expression. Considering that the evaluated protein hormones play crucial roles in angiogenesis and neovascularization in the placenta, “real life” PAH mixtures by disrupting protein hormones levels, the MMP-2/MMP-9 ratio and VEGF expression can lead to insufficiency and many pregnancy-related disorders.  相似文献   
2.
3.
4.
ObjectiveTo review laparoscopy in patients with disorders of sex development (DSD) in order to clarify its usefulness in diagnosis, devising subsequent therapeutic strategies and managing patients with various conditions.Patients and methodsBetween April 1992 and December 2012, 29 laparoscopic surgeries were performed in 25 DSD patients. Among them, ten were diagnostic laparoscopy including gonadal biopsy, and 19 were therapeutic laparoscopy. Surgical procedures and complications were evaluated.ResultsFor diagnostic laparoscopy, laparoscopic gonadal biopsy was performed in three patients. Inspection, with or without open gonadal biopsy, was performed on four out of seven patients with 46XY DSD or mixed gonadal dysgenesis (MGD). Additional surgery was planned and performed based on diagnostic laparoscopic findings in six out of seven patients. In the three patients with ovotesticular DSD, the gonadal pathology was diagnosed as: testis/ovary in one, testis/ovotestis in one and ovary/ovotestis in one – this was from the laparoscopic inspection and/or gonadal biopsy. However, the final diagnoses were bilateral ovotestis in two patients and ovary/ovotestis in one patient.For therapeutic laparoscopy, surgical procedures were: gonadectomy in 17 patients (bilateral in 13, unilateral in three, partial in two); hysterectomy in two patients; orchiopexy in one; and sigmoid vaginoplasty in one patient (included multiple procedures). There were no severe perioperative complications. In the four patients with a history of diagnostic laparoscopy, no severe intra-abdominal adhesions that would disturb therapeutic laparoscopic surgery were observed.ConclusionWhile diagnostic laparoscopy was helpful in devising a therapeutic surgical strategy in most of the patients with DSD who were suspected as having complex gonadal status or Müllerian duct derivatives, attention must be paid to precisely diagnosing the gonadal status in ovotesticular DSD. On the other hand, therapeutic laparoscopic surgeries were valuable procedures in treating DSD patients, even with a history of previous diagnostic laparoscopy.  相似文献   
5.
Abstract

Tumor markers are often heterogeneous substances that may be present in elevated concentrations in the serum of cancer patients. Typically measured by immunoassay, they contribute to clinical management, particularly in screening, case-finding, prognostic assessment, and post-treatment monitoring. Data both from external quality assessment (EQA) schemes and clinical studies demonstrate significant variation in tumor marker results obtained for the same specimen using different methods. Between-method between-laboratory coefficients of variation (CV) reported by EQA schemes generally reflect the complexity of the measurand, ranging from <5% for the structurally relatively simple α-fetoprotein (AFP) to >25% for the complex mucinous cancer antigen 19-9 (CA19-9). Improving the standardization of tumor marker measurements is particularly important for three reasons. The primary use of tumor markers is in monitoring cancer patients over long periods of time. Clinical interpretation of trends may consequently be affected if results are obtained in different laboratories using different methods or if a laboratory has to change method. Differences in results may have major implications for adoption of area-wide decision cut-offs and make implementation of these difficult. Method-related differences also make it difficult to compare clinical studies. Improving comparability of tumor marker results requires broad international agreement about which molecular forms of the measurand have clinical utility, identifying and adopting pure molecular forms as calibrants, and defining antibody specificities for their optimal detection. These aims have been achieved to varying extents for the most frequently measured serum tumor markers as described in this paper.  相似文献   
6.
A thorough understanding of nanoparticle bio-distribution at the feto-maternal interface will be a prerequisite for their diagnostic or therapeutic application in women of childbearing age and for teratologic risk assessment. Therefore, the tissue interaction of biocompatible dendritic polyglycerol nanoparticles (dPG-NPs) with first- trimester human placental explants were analyzed and compared to less sophisticated trophoblast-cell based models. First-trimester human placental explants, BeWo cells and primary trophoblast cells from human term placenta were exposed to fluorescence labeled, ~5?nm dPG-NPs, with differently charged surfaces, at concentrations of 1 µM and 10?nM, for 6 and 24?h. Accumulation of dPGs was visualized by fluorescence microscopy. To assess the impact of dPG-NP on trophoblast integrity and endocrine function, LDH, and hCG releases were measured. A dose- and charge-dependent accumulation of dPG-NPs was observed at the early placental barrier and in cell lines, with positive dPG-NP-surface causing deposits even in the mesenchymal core of the placental villi. No signs of plasma membrane damage could be detected. After 24?h we observed a significant reduction of hCG secretion in placental explants, without significant changes in trophoblast apoptosis, at low concentrations of charged dPG-NPs. In conclusion, dPG-NP’s surface charge substantially influences their bio-distribution at the feto-maternal interface, with positive charge facilitating trans-trophoblast passage, and in contrast to more artificial models, the first-trimester placental explant culture model reveals potentially hazardous influences of charged dPG-NPs on early placental physiology.  相似文献   
7.
Objective. The purpose of this investigation was to improve a rankit ordinal model for evaluating and validating dichotomized tests in a prospective Nordic project. Material and methods. The model is based on the assumption that the S‐shaped curve of fractions of positive for increasing concentrations can be de‐convoluted to a histogram and thereby used to calculate the parameters for a ln‐Gaussian distribution. In a Nordic survey, four urine samples with known concentrations of hCG (human chorionic gonadotrophin) and nitrites were distributed to more than 2500 practitioners' offices. Results. The results are presented as parameters (geometric mean and CV) for the components urine‐hCG and urine‐nitrites, together with fractions of positive for clinical critical values (5 and 40?IU/L for hCG), for which fractions should be below 0.01 and above 0.99, respectively, and 7?µmol/L for nitrites. Furthermore, the concentration intervals of varying fractions of positive from 0.01 to 0.99 are estimated as grey zones. The parameters and grey zones for different kits are compared. No urine‐hCG kit fulfilled the low clinical criterion, whereas all fulfilled the high criterion. Seven of the eight nitrites kits had fractions of positive above 0.9 for the company confirmation limit, but varying fractions for the clinically important limit of 7?µmol/L (fractions from 0.06 to 0.83). Conclusions. The present model makes it easy to estimate parameters for the kits, and also to estimate the fractions of measured positives for specified concentrations. It is thus suited for external quality assessment as well as for manufacturers' method validation.  相似文献   
8.
9.
Purpose: To assess the mid-trimester triple test biomarkers among women diagnosed with vasa previa (VP).

Methods: The study included 43 singleton pregnancies diagnosed with vasa previa between the years 1988 and 2011. The mid-gestation screening test for Down syndrome was calculated from the combination of triple serum markers and maternal age, and expressed as a multiple of the gestation specific normal mean (MoM). Reference MoM values were calculated from the local population. The levels of mid-gestation maternal serum alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and unconjugated estriol (uE3) of patients with VP were compared with control reference group.

Results: The mean hCG and αFP levels of women diagnosed with VP was significantly higher compared to control reference group (1.42 versus 0.99 MoM; p?p?3 levels between these two groups (0.99 versus 0.98 MoM; p?=?.71).

Conclusions: Our findings suggest that increased mid-gestation hCG and AFP were found among pregnancies complicated with VP. Clinicians should consider targeted scanning of pregnant women with risk factors for VP, including unexplained high maternal levels of hCG and αFP of the triple test, while conducting mid-gestation anomaly scan.  相似文献   
10.

Objective

This study sought to examine the effect of changing TSH threshold recommendations from 2.5 to 4 mIU/L before fertility therapy on the prevalence of early gestational subclinical hypothyroidism (SCH) (TSH2 >2.5 mIU/L) and to evaluate implications on progression to clinical pregnancy (defined as detection of cardiac activity on ultrasound).

Methods

A retrospective chart review was performed in an academic fertility clinic on all patients with a measured pre-treatment TSH (TSH1) and positive beta-human chorionic gonadotropin following fertility treatment. The study assessed the effect of TSH2 on ongoing pregnancy, both in patients newly diagnosed with SCH and in patients previously receiving LT4, stratified by initial TSH.

Results

Of 482 women included in the study, baseline TSH (TSH1) was <2.5 mIU/L in 333 women (69%) and 2.5–4 mIU/L in 64 women (13.2%). Eighty-five women were taking LT4 at baseline (17.6%). Among women with a TSH1 between 2.5 and 4 mIU/L, the corresponding TSH in early pregnancy (TSH2) was <2.5 mIU/L in 35 women (55%). Overall, there was no difference in progression to clinical pregnancy between women with a TSH2 of 2.5–4 mIU/L compared with women with a TSH2 <2.5 mIU/L (OR 0.70; 95% CI 0.44–1.09). Similarly, when excluding women taking LT4 at baseline, there was no difference in progression to clinical pregnancy (OR 0.90; 95% CI 0.28–2.86).

Conclusion

Rate of progression to clinical pregnancy was equivalent between women with an early pregnancy TSH (TSH2)?<2.5 and women with a TSH2 of 2.5–4.0 mIU/L. Our findings support initiating LT4 in early pregnancy, as opposed to pre-pregnancy if the TSH remains above cut-off because there does not appear to be a difference in in early pregnancy outcomes if treatment is delayed.  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