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   69786篇
  免费   7340篇
  国内免费   4861篇
耳鼻咽喉   744篇
儿科学   823篇
妇产科学   539篇
基础医学   5958篇
口腔科学   1236篇
临床医学   8462篇
内科学   7645篇
皮肤病学   695篇
神经病学   2917篇
特种医学   2847篇
外国民族医学   24篇
外科学   7433篇
综合类   16775篇
现状与发展   20篇
一般理论   3篇
预防医学   6614篇
眼科学   1302篇
药学   7557篇
  90篇
中国医学   5619篇
肿瘤学   4684篇
  2024年   859篇
  2023年   1134篇
  2022年   2940篇
  2021年   3452篇
  2020年   2797篇
  2019年   1889篇
  2018年   2084篇
  2017年   2245篇
  2016年   1994篇
  2015年   3278篇
  2014年   4043篇
  2013年   4280篇
  2012年   6187篇
  2011年   6725篇
  2010年   5212篇
  2009年   4581篇
  2008年   4815篇
  2007年   4661篇
  2006年   4132篇
  2005年   3501篇
  2004年   2388篇
  2003年   1920篇
  2002年   1489篇
  2001年   1212篇
  2000年   996篇
  1999年   682篇
  1998年   400篇
  1997年   370篇
  1996年   263篇
  1995年   259篇
  1994年   173篇
  1993年   137篇
  1992年   142篇
  1991年   142篇
  1990年   114篇
  1989年   74篇
  1988年   86篇
  1987年   80篇
  1986年   66篇
  1985年   47篇
  1984年   34篇
  1983年   12篇
  1982年   16篇
  1981年   12篇
  1980年   5篇
  1979年   15篇
  1978年   9篇
  1974年   10篇
  1972年   6篇
  1969年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
目的研究体内成熟与体外成熟卵母细胞的纺锤体位置及其与胚胎发育的关系。方法对134个体内成熟卵母细胞在卵母细胞胞质内单精子注射法(ICSI)操作时用纺锤体实时观察仪进行纺锤体位置的观察,体内成熟卵母细胞来自单纯因男性不育而进行ICSI治疗的患者15例(体内成熟组)。另外对45个体外成熟的卵母细胞观察纺锤体位置,体外成熟卵母细胞来自因多囊卵巢综合征致不孕而进行治疗的患者5例(体外成熟组)。纺锤体的位置按照其与第一极体之间的角度不同分为Ⅰ、Ⅱ、Ⅲ、Ⅳ和Ⅴ级。并观察两组成熟卵母细胞的受精及其胚胎发育情况。结果体内成熟组和体外成熟组患者的卵母细胞中可观察到纺锤体的分别占83.6%(112/134)和82.2%(37/45)。体内成熟组患者卵母细胞纺锤体的位置Ⅰ、Ⅱ、Ⅲ、Ⅳ和Ⅴ级分别为22.4%、55.2%、3.O%、3.O%、16.4%,体外成熟组则分别为17.8%、51.1%、8.9%、4.4%、17.8%,两组各级间分别比较,差异均无统计学意义(P〉0.05)。在体内成熟组卵母细胞中,纺锤体离第一极体较近(Ⅰ级)者受精率较高(93.3%),显著高于其他各级(分别为73.0%、2/4、1/4、63.6%,P〈0.05)。结论体内成熟与体外成熟卵母细胞间纺锤体位置未见显著差异;纺锤体的位置与卵母细胞受精率有一定相关性。  相似文献   
993.

Aim of the study

Nymphaea stellata willd. flowers (NSF) are used as a traditional medicine in India and Nepal to treat diabetic disease. Different works have demonstrated that NSF extract showed antihyperglycemic effect on alloxan-induced diabetic rats. In the present work we evaluated in vitro intestinal α-glucosidase inhibition as the possible mode of action of NSF extract on suppressing postprandial hyperglycemia for curing diabetic mellitus. In addition, NSF extract was studied to assess its possible acute oral toxicity and genotoxicity.

Materials and methods

Rat intestinal crude enzyme preparation and Caco-2 monolayer were used to evaluate α-glucosidase inhibitory activity of NSF extract. The main α-glucosidase inhibitors were detected by HPLC. For acute toxicity test, NSF extract was administered at doses of 2000, 5000 and 10,000 mg/kg body to three groups of 10 ICR mice each, and then clinical symptoms including mortality, clinical sign and gross findings were observed once a day for 14 days. In Ames test, histidine-dependent auxotrophic mutants of Salmonella typhimurium (strains TA97, TA98, TA100, TA102 and TA1535) were used and incubated in the presence and absence of S9 metabolic activation using NSF extract with concentrations of 150-5000 μg/plate. The chromosome aberration test was conducted with Chinese hamster lung (CHL) cells treated with NSF extract at doses of 150-5000 μg/ml in the presence and absence of S9 metabolic activation. In the in vivo mouse micronucleus assay, 9-week-old male and female ICR mice (n = 90, 25-30 g) were administered daily by oral gavage at doses of 2.5, 5.0 and 10.0 g/kg body for 1 or 2 days. Bone marrow smears were prepared from each treatment group 24 h after last administration and then polychromatic erythrocytes (PCEs) and normochromatic erythrocytes (NCEs) were identified.

Results

NSF extract showed potent rat intestinal α-glucosidase inhibitory activity for maltose hydrolysis with ED50 value of 0.1 mg/ml. In Caco-2 monolayer, α-glucosidase activity for the maltose hydrolysis was down-regulated by NSF extract at a concentration of 0.05 mg/well level, showing 74% inhibition compared to the saline treated control. NSF was rich in phenol contents and the main α-glucosidase inhibitor, 1,2,3,4,6-penta-O-galloyl-β-d-glucose, was identified together with two phenolic compounds of gallic acid and corilagin. In acute toxicity test, NSF extract did not produce any toxic signs or deaths and the LD50 value of this extract could be greater than 10,000 mg/kg body weight. These results of genotoxicity assessment showed that NSF extract did not cause genotoxic effects in Ames test, in the in vitro chromosomal aberration assay and in the in vivo micronucleus assay.

Conclusion

The current study shows that the extract from Nymphaea stellata flowers exhibits significant intestinal α-glucosidase inhibitory activity, without showing any acute toxicity or genotoxicity, which may be useful in suppressing postprandial hyperglycemia in diabetics. The results presented here suggest that the use of NSF in folk medicine as a natural antidiabetic treatment could be safe as well as beneficial.  相似文献   
994.
Violet laser acupuncture using a wavelength of 405 nm has been investigated in only a few scientific studies. The aim of this study was to provide selective evidence of a specific effect of violet laser acupuncture on mean cerebral blood flow velocity using a Doppler ultrasound technique. A transcranial Doppler sonography construction was developed especially for this study to monitor blood flow profiles in the basilar and middle cerebral arteries simultaneously and continuously. The acupuncture point Dazhui on the upper back was tested in a controlled study with 10 healthy volunteers (24.9 ± 3.3 years, mean age ± SD; 5 females, 5 males). In addition to an on/off-effect, violet laser stimulation increased the blood flow velocity in the basilar artery significantly (p < 0.001) compared with the reference interval before laser acupuncture. In the middle cerebral artery, only minimal, nonsignificant changes in blood flow velocity were seen. Metal needle acupuncture at the same point intensified the effects; however, blood flow profiles did not change significantly during and after stimulation with a deactivated violet laser.  相似文献   
995.
Zhang F  Zhang T  Qu Y  Jiang T  Cao YX  Li C  Fan L  Mei QB 《Oncology reports》2010,24(5):1297-1305
Docetaxel is a member of the taxane anti-microtubule class of chemotherapeutic agents, which are currently widely used in clinical cancer therapy. However, the anti-tumor mechanisms of docetaxel are not fully understood. Herein we show that docetaxel induces dose-dependent apoptosis in non-small cell lung cancer A549 cells, as detected by Annexin-V positive cells and PARP cleavage, which is via mitochondrial pathway and dependent on caspase-3 activation. Our study on the mechanisms confirms that docetaxel induces dose-dependent accumulation of cells in M phase and acetylation of α-tubulin, marker of tubulin stablization. Furthermore, docetaxel induces replication-dependent γ-H2AX formation which plays a crucial role in docetaxel-triggered apoptosis. The DNA polymerase inhibitor aphidicolin dose-dependently prevents docetaxel-induced γ-H2AX formation, as well as apoptosis. Notably, 0.6 μM APC almost completely blocked docetaxel-induced γ-H2AX formation and apoptosis. In addition, wortmannin pretreatment caused elevated γ-H2AX level, which was accompanied with increased apoptosis. This effect was due to the inhibition of DNA repair process by wortmannin, as down regulation of p21Waf1/Cip1 and DNA repair proteins such as Ku70, Ku80, DNA-PKcs and Rad50, were detected. These data show, for the first time, that the induction of apoptosis by docetaxel requires DNA replication, and replication-mediated DSBs are critical triggers of docetaxel-induced apoptosis.  相似文献   
996.
Tanaka T  Bai T  Yukawa K 《Oncology reports》2010,24(5):1401-1405
Targeted knockdown of the death-associated protein kinase (DAPK) expression in the endometrial adenocarcinoma HHUA cells reportedly induces cell death by enhancing the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis in an autocrine/paracrine manner. This suggests that endogenous DAPK is a potential candidate for a molecularly targeted anticancer therapy for patients with endometrial adenocarcinoma. To investigate the role of endogenous DAPK in anticancer drug sensitivity, we examined effects on cellular anticancer drug sensitivities of transfections with 5 different specific DAPK small-interfering RNAs (siRNAs) into HHUA cells. DAPK siRNA transfections strongly enhanced 5-fluorouracil (5FU)-sensitivity, but not etoposide-sensitivity, of HHUA cells compared with control siRNA-transfected cells. These results indicate that etoposide-stimulated cell death signals may share or include TRAIL-mediated apoptotic signals, and that 5FU-stimulated cell death signals may be independent from TRAIL-mediated apoptotic signals induced by DAPK siRNA transfections. Moreover, 5FU-combined chemotherapy with DAPK siRNA transfection may show stronger anticancer effects on patients with endometrial adenocarcinoma than does chemotherapy alone.  相似文献   
997.
He XD  Liu W  Tao LY  Cai L  Zhou L  Qu Q 《The American surgeon》2010,76(11):1269-1274
The aim of this study was to elucidate gender-specific markers for postresectional long-term survival of gallbladder cancer (GBC) based on a cohort of Chinese patients. Clinicopathological records of 81 patients (27 males and 54 females) after surgical resection for GBC were reviewed retrospectively. The influence of each variable on survival was determined using the Kaplan-Meier method and log-rank test. For females, Cox regression analysis was also adopted. Univariate analysis showed that the absence of lymph node and distant metastases, differentiation grade, and curative resection were associated with prolonged survival for all males, whereas tumor size, differentiation grade, and the presence of lymph node metastases influenced the overall or disease-free survival of patients after curative resection (all P < 0.05). On the other hand, Nevin stage was an independent marker for both overall survival for all females and overall and disease-free survival for female patients who underwent curative resection. Additionally, resection type and differentiation grade were of independent prognostic significance for different subgroups of females (all P < 0.05). Our data suggested that tumor-related factors affect prognosis of both male and female patients with GBC after resection. Of these factors, tumor differentiation status might be more significant for males, but Nevin stage had a stronger predictive potential for females.  相似文献   
998.

Background

Plasmakinetic enucleation of the prostate (PKEP) has recently been proved a safe and technically feasible procedure for benign prostatic hyperplasia (BPH). However, its long-term safety, efficacy, and durability in comparison with the gold-standard transurethral resection of the prostate (TURP) have not yet been reported.

Objective

To report the 3-yr follow-up results of a prospective, randomised clinical trial comparing PKEP with standard TURP for symptomatic BPH.

Design, setting, and participants

A total of 204 patients with bladder outflow obstruction (BOO) secondary to BPH were prospectively randomised 1:1 into either the PKEP group or the TURP group.

Intervention

The patients in each group underwent the procedure accordingly.

Measurements

All patients were assessed perioperatively and followed at 1, 3, 6, 12, 18, 24, and 36 mo postoperatively. The preoperative and postoperative parameters included International Prostate Symptom Score (IPSS), quality of life (QoL) scores, the International Index of Erectile Function (IIEF) questionnaire, maximum urinary flow rates (Qmax), transrectal ultrasound (TRUS)–assessed prostate volume, postvoid residual urine (PVRU) volume, and serum prostate-specific antigen (PSA) level. Patient baseline characteristics, perioperative data, and postoperative outcomes were compared. All complications were recorded.

Results and limitations

PKEP was significantly superior to TURP in terms of the drop in haemoglobin (0.74 ± 0.33 g/dl vs 1.88 ± 1.06 g/dl; p < 0.001), intraoperative irrigation volume (11.7 ± 4.5 l vs 15.4 ± 6.2 l; p < 0.001), postoperative irrigation volume and time (18.5 ± 7.6 l vs. 30.0 ± 11.4 l and 16.6 ± 5.2 h vs 25.3 ± 8.5 h; all p < 0.001), recovery room stay (67.3 ± 11.1 min vs 82.0 ± 16.4 min; p < 0.001), catheterisation time (51.7 ± 26.3 h vs 80.5 ± 31.6 h; p < 0.001), hospital stay (98.4 ± 20.4 h vs 134.2 ± 31.5 h; p < 0.001), and resected tissue (56.4 ± 12.8 g vs 43.8 ± 15.5 g; p < 0.001). There were no statistical differences in operation time and sexual function between the two groups. At 36 mo postoperatively, the PKEP group had a maintained and statistically significant improvement in IPSS (2.4 ± 2.2 vs 4.3 ± 2.9; p < 0.001), QoL (0.6 ± 0.5 vs 1.6 ± 1.4; p < 0.001), Qmax (28.8 ± 10.1 ml/s vs 25.1 ± 8.0 ml/s; p = 0.017), and TRUS volume (21.0 ± 7.3 ml vs 26.4 ± 6.8 ml; p < 0.001), with urodynamically proven deobstruction (Schäfer grade 0.2 ± 0.02 vs 0.8 ± 0.1; p < 0.001). More extensive clinical trials are required to validate these results.

Conclusions

PKEP is a safe and highly effective technique for relieving BOO. At 3-yr follow-up, the clinical efficacy of PKEP is durable and compares favourably with TURP.  相似文献   
999.
Transesophageal echocardiogram (TEE) guided perventricular cardiac intervention has gained popularity in recent years. We present a special case of perventricular closure conducted for a traumatic apical muscular ventricular septal defect (mVSD) under the guidance of three-dimensional (3D) TEE with an Amplatzer mVSD occluder and further discuss the important role of 3D TEE in perventricular cardiac intervention.  相似文献   
1000.
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