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   2560篇
  免费   128篇
  国内免费   12篇
耳鼻咽喉   62篇
儿科学   122篇
妇产科学   130篇
基础医学   192篇
口腔科学   101篇
临床医学   203篇
内科学   587篇
皮肤病学   56篇
神经病学   97篇
特种医学   65篇
外国民族医学   1篇
外科学   410篇
综合类   58篇
预防医学   131篇
眼科学   78篇
药学   260篇
中国医学   10篇
肿瘤学   137篇
  2023年   26篇
  2022年   87篇
  2021年   125篇
  2020年   67篇
  2019年   104篇
  2018年   116篇
  2017年   75篇
  2016年   75篇
  2015年   87篇
  2014年   103篇
  2013年   129篇
  2012年   211篇
  2011年   185篇
  2010年   92篇
  2009年   87篇
  2008年   115篇
  2007年   126篇
  2006年   110篇
  2005年   105篇
  2004年   75篇
  2003年   67篇
  2002年   55篇
  2001年   41篇
  2000年   21篇
  1999年   24篇
  1998年   21篇
  1997年   11篇
  1996年   25篇
  1995年   15篇
  1994年   7篇
  1992年   16篇
  1991年   21篇
  1990年   10篇
  1989年   17篇
  1988年   26篇
  1987年   27篇
  1986年   15篇
  1985年   10篇
  1984年   11篇
  1983年   7篇
  1979年   14篇
  1978年   10篇
  1977年   12篇
  1976年   18篇
  1975年   9篇
  1974年   11篇
  1973年   9篇
  1972年   9篇
  1967年   6篇
  1966年   10篇
排序方式: 共有2700条查询结果,搜索用时 15 毫秒
91.
PTEN is a tumor suppressor gene that is frequently mutated in type I endometrioid endometrial carcinomas (EECs), and is involved in the control of cell proliferation, differentiation, and apoptosis. In this study, we aimed to assess the relationship between PTEN expression and estrogen, progesterone receptors (PRs), other apoptosis-related proteins, such as bcl-2 and bax, and apoptotic index (AI) in EEC, its precursor lesion hyperplasia, and cyclical endometrium. We also evaluated the relationship between PTEN expression and clinicopathologic parameters. PTEN, estrogen receptor (ER), PR, and bcl-2 and bax expressions were evaluated immunohistochemically, and AI was evaluated in hematoxylin and eosin (HE)-stained slides in 23 cyclical and 37 hyperplastic endometria and in 35 EECs. PTEN expression was higher in cyclical endometrium than in the carcinomas (p<0.05). The PTEN expression level was significantly higher in non-atypical hyperplasias than in EEC, but there were no differences between atypical complex hyperplasia (ACH) and EEC and between hyperplasias. In the carcinomas, there was a negative correlation between grade and PTEN expression (r=-0.338, p=0.047). In conclusion, we presume that PTEN is involved in the early phases of endometrial tumorigenesis, and it can be speculated that decreased PTEN expression with loss of differentiation in carcinoma can contribute to the emergence of tumors with a more aggressive phenotype.  相似文献   
92.
Potassium bromate (KBrO3) is a food additive which is used primarily as a maturing agent for flour. It is proved as a toxic agent with significant reduction in the activities of antioxidant capacity. The therapeutic efficacy of vitamin C as antioxidant may provide a possible solution to KBrO3 mediated oxidative damage. Twenty four adult male albino rats were used to evaluate the protective role of vitamin C against KBrO3 induced hepatotoxicity and divided into four groups; Group 1 (control), Group 2: received 30 mg/Kg/day vitamin C orally for 4 weeks, Group 3: received 20 mg/Kg/dose KBrO3 orally twice weekly for 4 weeks and Group 4: received both KBrO3 and vitamin C. Liver specimens were processed for histological study by light and electron microscopes and stained immunohistochemically to detect glial fibriller acidic protein (GFAP). Serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were estimated as well as the levels of malondialdehyde (MDA), glutathione (GSH) and superoxide dismutase (SOD) activities in all dissected tissues were determined. KBrO3 induced histological alterations in the form of degeneration, cellular infiltration and significant increase in collagen deposition in portal tracts with a significant increase in immunoexpression of GFAP. Significant rise in serum levels of AST, ALT, and MDA in liver tissues were recorded. However, levels of GSH and SOD were significantly decreased. Most of these changes were improved by vitamin C treatment. In conclusion, vitamin C ameliorates the histological and biochemical alterations of the liver induced by KBrO3. Anat Rec, 299:1256–1269, 2016. © 2016 Wiley Periodicals, Inc.  相似文献   
93.
Summary: The equilibrium swelling degree, modulus of elasticity and the spatial inhomogeneity of poly(N,N‐dimethylacrylamide) (PDMAAm) hydrogels were investigated over the entire range of the initial monomer concentration. The degree of dilution of the networks after their preparation was denoted by ν, the volume fraction of crosslinked polymer after the gel preparation. The linear swelling ratio of the gels increased linearly with increasing ν. Depending on the value of ν, three different gel regimes were observed: (1) For ν < 0.3, increasing ν decreases the extent of cyclization during crosslinking so that the effective crosslink density of gels increases with rising ν. (2) For 0.3 < ν < 0.7, increasing ν reduces the accessibility of the pendant vinyl groups during crosslinking due to steric hindrance at high polymer concentrations. As a result, the effective crosslink density of gels decreases with increasing ν. (3) For ν > 0.7, the modulus of elasticity increases sharply with increasing ν due to the increasing extent of chain entanglements in this high concentration regime. Static light scattering measurements on the gels show that the degree of spatial gel inhomogeneity in PDMAAm gels attains a maximum value at ν = 0.06. The appearance of a maximum as well as the ν‐dependence of scattered light intensities from gels was successfully reproduced by the theory proposed by Panyukov and Rabin.

Effective crosslink density νe of the hydrogels shown as a function of ν.  相似文献   

94.
Cerebrospinal fluid gamma interferon (IFN-γ) and interleukin-10 levels in 39 patients with tuberculous meningitis were serially measured. Cytokine levels did not predict intracranial granuloma (IG) development, but IFN-γ levels in the top quartile after 1 month of therapy were highly associated (odds ratio = 18) with detection of an IG by computed tomography scanning.  相似文献   
95.
DNA fingerprinting of Candida dubliniensis isolates using the species-specific probe Cd25 previously showed that this species consists of two distinct groups, termed Cd25 group I and Cd25 group II. The present study investigated the population structure of 30 C. dubliniensis oral isolates from Saudi Arabia and Egypt using Cd25 fingerprinting and rRNA gene internal transcribed spacer region-based genotyping. Cd25 fingerprinting analysis of these isolates revealed two distinct populations, the first of which consisted of 10 closely related genotype 1 isolates (average similarity coefficient [S(AB)] value, 0.86). The second population of 20 isolates was much more heterogeneous (average S(AB) value, 0.35) and consisted of two distinct subpopulations, one of which consisted of genotype 3 isolates (n = 13) and the other of genotype 4 isolates (n = 7). A mixed dendrogram generated from the fingerprint data from the 30 Saudi Arabian and Egyptian isolates, 5 Israeli isolates, and 51 previously characterized international isolates (32 of Cd25 group I and 19 of Cd25 group II) revealed the presence of three distinct main clades. The first corresponded to the previously described Cd25 group I and contained all the Saudi Arabian, Egyptian, and Israeli genotype 1 isolates mixed with international isolates. The second clade corresponded to the previously described Cd25 group II and contained three Israeli isolates, one genotype 2 isolate, one genotype 3 isolate, and a genotype 4 variant isolate, which were mixed with international isolates. The third clade has not been described before and consisted solely of the 20 Saudi Arabian and Egyptian genotype 3 and 4 isolates identified in this study and a previously described genotype 4 Israeli isolate. All 20 Cd25 group III isolates exhibited high-level resistance to 5-flucytosine (MIC > or = 128 microg/ml), whereas all Cd25 group I and Cd25 group II isolates tested (10 Saudi Arabian and Egyptian, 16 Israeli, and 24 international) were susceptible to 5-flucytosine (MIC < or = 0.125 microg/ml). The results of this study show for the first time the presence of a novel 5-flucytosine-resistant clade of C. dubliniensis (Cd25 group III) that is predominant among isolates from Saudi Arabia and Egypt and absent from a previously characterized international collection of 98 isolates from 15 countries.  相似文献   
96.
Longitudinal growth data for infants in Qatar were compared to growth standards published by the CDC and WHO. 300 randomly selected full-term normal infants (150 males, 150 females) in Qatar were followed-up and weight and length were sequentially recorded at 2 months, 4 months, 6 months, 12 months and 18 months age. The mean length for age of girls was higher than those published by the CDC and WHO at 12 and 18 months of age. Using the CDC standard for weight for length detected more wasted infants (9.0% and 6.5%) compared to using WHO standards (6.27% and 6.0%) for males and females, respectively. When WHO and CDC standards are compared, more infants were identified as overweight when the former were used. The WHO standards are preferable because they are based on a leaner breastfed reference and because overweight is likely to be a greater problem in Qatar in the future.  相似文献   
97.
Objective: To assess and compare the effectiveness and safety of single IV polus dose of carbetocin, versus IV oxytocin infusion in the prevention of PPH in obese nulliparous women undergoing emergency Cesarean Delivery.

Methods: A double-blinded randomized-controlled trial was conducted on 180 pregnant women with BMI >30. Women were randomized to receive either oxytocin or carbetocin during C.S. The primary outcome measure was major primary PPH >1000?ml within 24?h of delivery as per the definition of PPH by the World Health Organization Secondary outcome measures were hemoglobin and hematocrit changes pre- and post-delivery, use of further ecobolics, uterine tone 2 and 12-h postpartum and adverse effects.

Results: A significant difference in the amount of estimated blood loss or the incidence of primary postpartum haemorrhage (>1000?ml) in both groups. Haemoglobin levels before and 24-h postpartum was similar. None from the carbetocin group versus 71.5% in oxytocin group needed additional utrotonics (p?<?0.01). The uterine contractility was better in the carbetocin group at 2, and 12-h postpartum (p?<?0.05).

Conclusions: A single 100-µg IV carbetocin is more effective than IV oxytocin infusion for maintaining adequate uterine tone and preventing postpartum bleeding in obese nulliparous women undergoing emergency cesarean delivery, both has similar safety profile and minor hemodynamic effect.  相似文献   
98.
Objectives: Preeclampsia is associated with significant morbidity and mortality especially in high-risk groups. Impairment of endogenous nitric oxide has been shown to be associated with the disease and prophylactic therapy may ameliorate this condition and improve pregnancy outcome. This study valuated nitric oxide donors prophylactic treatment for preeclampsia in high-risk teenage primigravidae.

Methods: The study included three hundred primigravidae aged?≤?20 years with singleton pregnancy. Abdominal pulsed color Doppler ultrasound was done at 24 weeks gestation and pregnancies with uterine artery diastolic notch were randomly allocated to a control group received placebo vaginal tablets and a study group received isosorbid mononitrate 20?mg tablet once daily applied vaginally until delivery.

Outcomes: Incidence of preeclampsia and maternal, fetal, and neonatal outcome in both groups.

Results: The study group had significant lower incidence of preeclampsia, preterm birth, intrauterine growth restriction and of neonatal admission to the intensive care (p?<?0.05).

Conclusions: Nitric oxide donors prophylactic treatment for preeclampsia in high-risk teenage pregnancies decrease the incidence of preeclampsia and improve maternal, fetal, and neonatal outcomes. Further studies on larger sample size are required to confirm these results.  相似文献   
99.
We measured serum concentrations of insulin like growth factor-I (IGF-I) in 20 thalassemic males with short stature (height SDS <-2) and/or slow growth velocity (GV <-1 SD) throughout their childhood and adolescence, compared these data with normal reference data validated in our lab, and evaluated their growth hormone secretion in response to clonidine and glucagon stimulation. We also performed IGF-I generation test on 26 patients with beta thalassemia major (BTM) before and after blood transfusion to evaluate the effect of increased hemoglobin (Hb) on IGF-I and its response to GH. We obtained the following results. 1) No statistical difference in age, HSDS, target height SDS or bone age was observed between BTM patients with growth hormone deficiency (GHD) compared to those with normal GH secretion (GHS). 2) The age-related levels in serum total IGF-I in thalassemic males were significantly decreased from early childhood to 18 years of age compared to normal subjects. Thalassemic males with GHD did not show any significant peak of IGF-I levels until 18 years of age, whereas thalassemic males with normal GH response to provocation (GHS) achieved a significant peak level of IGF-I that was attenuated and late compared to normal males. The basal serum IGF-I concentrations at different ages did not differ between the GHD and GHS groups until the age of 12 years. After 12 years of age, IGF-I levels were significantly higher in thalassemic children with GHS. A significant increase in the circulating basal IGF-I concentrations from 53 +/-35 ug/l to 82.6 +/- 39 ug/L was achieved with increasing Hb concentration after blood transfusion. The serum total IGF-I levels increased significantly with the administration of human growth hormone (hGH) for 4 days, both before and after blood transfusion. The peak IGF-I response to GH injections did not differ before compared to after blood transfusion. The percent increment of IGF-I levels generated after GH injections was higher in thalassemic children with GHD as compared to those with GHS both before and after blood transfusion. In conclusion, our results showed that agerelated serum IGF-I concentrations were significantly lower in short thalassemic patients, with and without GHD, during childhood and adolescence, compared to normal standards. Correction of anemia significantly increased serum concentration of IGF-I but does not affect the increase of IGF-I in response to GH stimulation.  相似文献   
100.

In this research we have used different cytokines and progesterone to enhance the immunomodulatory capacity of placental-derived stem cells (PLSCs) prior to their encapsulation. We assessed the effect of microencapsulation of the cells without (control) or after 3-day treatment with interferon gamma (INFγ), interleukin10 (IL-10), or progesterone (P4). Treated PLSCs demonstrated strong immunosuppressive effects on phytohemagglutinin (PHA)-activated peripheral blood mononuclear cells (PBMNCs). INFγ treatment resulted in the strongest immune inhibition among the treated groups. The treatments enhanced soluble human leukocyte antigen (sHLAG) secretion compared to control. The IL-10-treated group showed the highest effect on HLAG secretion compared to other groups. Alginate encapsulation of PLSCs did not affect cell viability, or sHLAG secretion. Also, after treatment the encapsulated PLSCs inhibited PHA-activated PBMNCs in the same manner as unencapsulated cells. We studied two groups of encapsulated PLSCs, one without perm-selective poly-l-ornithine (PLO)-coating and the other with PLO-coating, and measured levels of sHLAG secreted. We found no difference in sHLAG secretion between both groups. In summary, our data show that immunomodulatory function of the PLSC is not affected by encapsulation. These findings provide good promise for potential use of encapsulated PLSCs for immunomodulation treatment of disease by stem cell therapy.

  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