首页 | 官方网站   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   3182篇
  免费   168篇
  国内免费   15篇
医药卫生   3365篇
  2024年   1篇
  2023年   52篇
  2022年   94篇
  2021年   144篇
  2020年   95篇
  2019年   146篇
  2018年   136篇
  2017年   103篇
  2016年   159篇
  2015年   127篇
  2014年   161篇
  2013年   215篇
  2012年   284篇
  2011年   265篇
  2010年   138篇
  2009年   129篇
  2008年   165篇
  2007年   200篇
  2006年   180篇
  2005年   170篇
  2004年   147篇
  2003年   81篇
  2002年   80篇
  2001年   11篇
  2000年   7篇
  1999年   9篇
  1998年   8篇
  1997年   8篇
  1996年   5篇
  1995年   5篇
  1994年   6篇
  1993年   3篇
  1992年   4篇
  1991年   3篇
  1990年   2篇
  1989年   2篇
  1988年   3篇
  1987年   3篇
  1986年   1篇
  1985年   1篇
  1984年   3篇
  1983年   2篇
  1980年   1篇
  1974年   1篇
  1973年   1篇
  1971年   2篇
  1960年   1篇
  1958年   1篇
排序方式: 共有3365条查询结果,搜索用时 15 毫秒
1.
Infertility represents a major medical, economic, and psychological problem. Stem cells therapy for infertility has a great interest nowadays especially for cancer survivors at pre-reproductive and reproductive age.

 Thirty-two adult male albino rats were used, divided equally into four groups; Group I (Control group) received isotonic saline intraperitoneally (i.p.) as vehicle. Group II (Cisplatin-treated group) received Cisplatin (i.p.) at a single dose of 7 mg/kg, and then were sacrificed after 5 days. Group III (Stem-cell-treated group) received Cisplatin (i.p.) at a single dose of 7 mg/kg, then after 5 days received adipose-derived mesenchymal stem cells (ADMSCs) (1 × 106). Cells were injected in the rete testis, then after 60 days, the animals were sacrificed. Group IV (Auto healing group) received Cisplatin (i.p.) at a single dose of 7 mg/kg, and then left for 65 days then the animals were sacrificed. Cisplatin administration resulted in degenerative changes in the testicular architecture in the form of thickened irregular BM of seminiferous tubules. The germinal epithelium showed disorganization and marked reduction in the thickness, associated with Sertoli cells preservation. Features of apoptosis assured by elevated caspase-3 expression were noticed. The interstitium showed cellular infiltration and distorted Leydig cells. Injection of (ADMSCs) resulted in great improvement of testicular architecture and increase in the testosterone level associated with strong immune reaction of the CD-44. ADMSCs are recommended as a new treatment modality for male infertility.

Abbreviation: i.p.: intraperitoneally; BM: basement membrane; ADMSCs: adipose-derived mesenchymal stem cells; WHO: World Health Organization; MSCs: mesenchymal stem cells; DMEM: Dulbecco modified eagles media; PBS: phosphate-buffered saline; FACS: fluorescence-activated cell sorting; ELISA: enzyme-linked immunosorbent assay; CP: Cisplatin; ROS: reactive oxygen species; CAT: catalase; SOD: superoxide dismutase; OS: oxidative stress; SSCs: spermatogonia stem cells; GCs: germ cells; UCMSCs: umblical cord mesenchymal stem cells; TGFb1: transforming growth factor beta-1; BMP4: Bone morphogenic protein 4; BMP8b: bone morphogenic protein 8b.  相似文献   

2.
3.
Coexistence of spondyloarthritis (SpA) and Takayasu’s arteritis is not a common finding, but such cases have been discussed, particularly in the context of choice of therapy. Inhibition of inflammation by tumor necrosis factor inhibitors (TNFi) is a key aspect of the treatment of SpA and also positive effects of such treatment in concomitant large vessel vasculitis have been reported. However, TNFi is also associated with the possibility of initiating vasculitis.The present article based on a case study and the available literature is an attempt to discuss coexistence of these two diseases and the impact of treatment with biological drugs from the anti-TNF group in the course of SpA with Takayasu’s arteritis.  相似文献   
4.
A convenient method for the preparation of imidazobenzimidazole3, imidazoimidazole5, imidazotriazole6 and pyrano [2, 3-c] oxazole7 derivatives is described. This depends on interaction of 2-methyl-4-arylidene-2-oxazolin-5-ones1 with o-diamines, thiosemicarbazide and/or ethylcyanoacetate. The effect of alcoholic potassium cyanide on oxazolinone1 was studied. Antibacterial activity of the obtained products was studied.  相似文献   
5.
AimTo determine the frequency of serological markers of RA in patients with anti‐β2 glycoprotein I antibodies (aβ2GPI) of IgA isotype.Material and MethodsA retrospective study was conducted on 67 patients with aβ2GPI‐IgA. Ninety healthy blood donors (HBD) were used as a control group. IgG anti‐cyclic citrullinated peptides antibodies (CCP‐Ab) and rheumatoid factors (RF) IgG, IgA, and IgM were detected by enzyme‐linked immunosorbent assay (ELISA).ResultsSeventeen patients and eight HBD had CCP‐Ab and/or RF (25.4% vs. 8.9%, p = 0.005, CI 95% [14.95; 35.79], odds ratio = 3.5). The frequency of CCP‐Ab was significantly higher in patients than in healthy subjects (14.9% vs. 3.3%, p = 0.009). IgA isotype of RF was significantly higher in patients than in controls (7.5% vs. 0%, p = 0.02). In male patients, CCP‐Ab and/or RF were more frequent than in healthy male subjects (37.5% vs. 11.8%, p = 0.02). In patients, no correlation was found between the levels of aβ2GPI‐IgA and CCP‐Ab (r = 0.082, p = 0.51). There was no correlation between the level aβ2GPI‐IgA and the level of the isotypes of RF (IgG, IgA, and IgM) in patients (r = 0.1, p = 0.37; r = 0.17, p = 0.17 and r = 0.07, p = 0.59 respectively).ConclusionFrequencies of CCP‐Ab and RF are high in patients with aβ2GPI‐IgA suggesting that these patients are susceptible to developing RA.  相似文献   
6.
Abstract

A receptor level interaction of etoposide with P-glycoprotein (P-gp) and subsequent intestinal efflux has an adverse effect on its oral absorption. The present work is aimed to enhance the bioavailability of etoposide by co-administering it with quercetin (a P-gp inhibitor) in dual-loaded polymeric nanoparticle formulation. Poly-lactic-co-glycolic acid (PLGA) nanoparticles were optimized for various parameters like o/w phase volume ratio, poly-vinyl alcohol concentration, PLGA concentration and sonication time. The cytotoxicity studies (MTT assay) revealed a 9- and 11-fold decrease in the IC 50 values for etoposide-loaded nanoparticles (ENP) and etoposide?+?quercetin dual-loaded nanoparticles (EQNP) when compared to that of free etoposide, respectively, and the results were further supported by florescent-activated cell sorter studies. The confocal imaging of the intestinal sections treated with ENP and EQNP containing fluorescent probe (rhodamine) showed the superiority of the EQNP to permeate deeper. Furthermore, pharmacokinetic studies on rats revealed that EQNP exhibited a 2.4-fold increase in bioavailability of etoposide than ENP with no quercetin. The developed loaded nanoparticles have the high potential to enhance the bioavailability of the etoposide and sensitize the resistant cells.  相似文献   
7.
Context We report the first ever chemical/biochemical study on Crocus mathewii Kerndorff (Iridaceae) – a Turkish endemic angiosperm. This plant has never been explored for its phytochemistry and bioactivities.

Objective This study explores C. mathewii corm and aerial parts for the chemical and biological properties of hexane, ethyl acetate, methanol and water fractions of the extracts.

Material and methods Plant material (20 g) was extracted by methanol (250?mL?×?5, 3 days each) and fractioned into hexane, ethyl acetate, methanol and water. All fractions were subjected to β-carotene–linoleic acid, DPPH·, ABTS·+, CUPRAC, metal chelating and tyrosinase inhibition activities. Hexane fractions were submitted to GC–MS analysis.

Results Ethyl acetate fractions showed excellent IC50 values in DPPH· (aerial 36.21?±?0.76 and corm 33.87?±?0.02?mg/L) and ABTS·+ (aerial 33.01?±?0.79 and bulb 27.87?±?0.33?mg/L); higher than the IC50 of the standard α-tocopherol (DPPH 116.25?±?1.97; ABTS 52.64?±?0.37?mg/L), higher than BHA in DPPH (57.31?±?0.25?mg/L), but slightly lower in ABTS (19.86?±?2.73?mg/L). Methanol extract of aerial parts also showed higher activity than α-tocopherol in DPPH (85.56?±?11.51?mg/L) but slightly less (72.90?±?3.66?mg/L) than both the standards in ABTS. Linoleic (aerial 53.9%, corm 43.9%) and palmitic (aerial 22.2%, corm 18%) were found as the major fatty acids.

Discussion and conclusion Some fractions of C. mathewii showed higher antioxidant activities than the standards. There is a need to explore more about this plant.  相似文献   
8.
9.
Three new 28-norlupane triterpenes, 28-norlup-20(29)-en-3beta-hydroxy-17beta-hydroperoxide (1), 28-norlup-20(29)-en-3beta-hydroxy-17alpha-hydroperoxide (2), and 20 S-17beta,29-epoxy-28-norlupan-3beta-ol (3), were isolated from the leaves of Melaleuca ericifolia along with eight known pentacyclic triterpenes. The structures of the new compounds were elucidated by spectroscopic methods including 1D and 2D NMR spectroscopy and mass spectrometry. The isolated triterpenes were evaluated for antiproliferative activity against the malignant +SA mammary epithelial cell line.  相似文献   
10.

Objective

To assess trends in twinning over four decades using a population-based registry.

Design

Ecological study to conduct trend analysis of twin pregnancies in a geographically defined area over 40 years.

Setting

All pregnancies in the Cardiff and Vale of Glamorgan area of South Wales from 1965 to 2004, as recorded in the Cardiff Birth Survey (CBS) database.

Methods

Trends of the incidence of all twin pregnancies (≥18 weeks of gestation) were calculated in 5-year increments, beginning with 1965–1969 and ending in 2000–2004. Natural twinning rates could only be calculated for the terminal five time periods (i.e., 1980–1984, 1985–1989, 1990–1994, 1995–1999, and 2000–2004), when information regarding non-spontaneous (iatrogenic) twinning was first collected in the database. All results were adjusted for maternal age.

Results

The total twinning rate was 13.1 per 1000 pregnancies in the 1st time period (1965–1969). Subsequently, there was a gradual reduction in twinning, reaching a nadir of 10.3 per 1000 for the time period 1980–1985 (Z = 3.15, P value < 0.001). This was followed by a gradual increase in twinning, reaching a maximum of 15.7 per 1000 for both 1995–1999 and 2000–2004 (Z = −5.18, P value < 0.0001). After exclusion of the cases of iatrogenic pregnancies, the natural twinning rate showed a continuous and gradual increase from 10 per 1000 spontaneous pregnancies in 1980–1984 to 13.3 per 1000 in 2000–2004 (Z = −5.08, P value < 0.0001).

Conclusion

The data showed a gradual, continuous increase in natural twinning rates over the last two decades. Such an increase cannot be attributed to the rise in maternal age alone.  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-23

京公网安备 11010802026262号