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   5285篇
  免费   215篇
  国内免费   49篇
耳鼻咽喉   21篇
儿科学   160篇
妇产科学   96篇
基础医学   681篇
口腔科学   113篇
临床医学   320篇
内科学   1411篇
皮肤病学   134篇
神经病学   274篇
特种医学   214篇
外科学   928篇
综合类   38篇
一般理论   1篇
预防医学   133篇
眼科学   42篇
药学   398篇
中国医学   62篇
肿瘤学   523篇
  2024年   6篇
  2023年   39篇
  2022年   75篇
  2021年   136篇
  2020年   66篇
  2019年   88篇
  2018年   108篇
  2017年   74篇
  2016年   124篇
  2015年   113篇
  2014年   160篇
  2013年   188篇
  2012年   315篇
  2011年   303篇
  2010年   208篇
  2009年   173篇
  2008年   345篇
  2007年   359篇
  2006年   343篇
  2005年   348篇
  2004年   338篇
  2003年   395篇
  2002年   417篇
  2001年   68篇
  2000年   42篇
  1999年   82篇
  1998年   105篇
  1997年   70篇
  1996年   51篇
  1995年   49篇
  1994年   53篇
  1993年   57篇
  1992年   27篇
  1991年   25篇
  1990年   33篇
  1989年   20篇
  1988年   21篇
  1987年   19篇
  1986年   15篇
  1985年   10篇
  1984年   16篇
  1983年   11篇
  1982年   18篇
  1981年   9篇
  1980年   9篇
  1978年   6篇
  1977年   2篇
  1976年   2篇
  1975年   2篇
  1974年   3篇
排序方式: 共有5549条查询结果,搜索用时 15 毫秒
991.
The tight junction is not a constitutional junctional apparatus in endothelial cells, but develops in a particular lineage of endothelia, such as the capillary endothelia in the brain and retina, and thus is considered to be pivotal for the maintenance of the blood-tissue barrier. Occludin is an integral membrane component of tight junctions, but the role of occludin in the endothelial cell function remains to be elucidated. We have cloned and transfected rat full-length occludin cDNA into a rat endothelial cell line (RLE) that expressed only a trace amount of occludin with no fine circumferential actin bundles at the cell border in native conditions. Occludin was expressed at the cell border of RLE cells, and circumferential fine actin bundles developed in close relation to the sites of occludin localization. Even under subconfluent culture conditions, fine circumferential actin bundles were formed at the sites where occludin-positive cell-cell contact was achieved. In immunoelectron microscopy, occludin was localized at distinct areas of the plasma membrane, always in association with the cytoplasmic actin filaments. On the other hand, actin bundles were not seen in occludin-negative juxtaposing plasma membranes. Collectively, these data strongly suggested a possible determinant function of occludin for the organization of actin in endothelial cells.  相似文献   
992.
We report a case of postoperative recurrence of adenoid cystic carcinoma in the left parotid gland treated with radiotherapy and arterial infusion chemotherapy. A 52-year-old woman had a history of surgical resection for an adenoid cystic carcinoma arising from the left parotid gland 25 years before. Despite two reoperations for local recurrence after the initial surgery, she had a third local recurrence in the remnant of the left parotid gland. The patient was treated with a concurrent combination of radiotherapy (60 Gy/30F) and intraarterial infusion chemotherapy with carboplatin (750 mg/30 days) from which she obtained a complete response. The patient has remained free of local progression 54 months after treatment. Radiotherapy and arterial infusion chemotherapy is effective treatment for local recurrence of adenoid cystic carcinoma in the head and neck.  相似文献   
993.
The endogenous hallucinogen, N,N-dimethyltryptamine (DMT), was labeled with carbon-11 and its regional distribution in rat brain studied. [11C]DMT showed higher accumulation in the cerebral cortex, caudate putamen, and amygdaloid nuclei. Studies of the subcellular distribution of [11C]DMT revealed the specific localization in the fractions enriched with serotonin receptors only when a very low dose was injected into rats. The proportions of the radioactivity in receptor-rich fractions were greatly enhanced by pretreatment with the monoamine oxidase inhibitor, pargyline. Specific binding of [11C]DMT to serotonin receptors in dog brain was demonstrated by a positron emission tomographic study in which 5-methoxy-N,N-dimethyltryptamine caused approximately 20% displacement of the radioligand from the receptors.  相似文献   
994.

Purpose

To compare the effectiveness of microwave (MW) ablation with radiofrequency (RF) ablation for treating breast tissue in a nonperfused ex vivo model of healthy bovine udder tissue.

Materials and Methods

MW ablations were performed at power outputs of 25W, 35W, and 45W using a 915-MHz frequency generator and a 2-cm active tip antenna. RF ablations were performed with a bipolar RF system with 2- and 3-cm active tip electrodes. Tissue temperatures were continuously monitored during ablation.

Results

The mean short-axis diameters of the coagulation zones were 1.34 ± 0.14, 1.45 ± 0.13, and 1.74 ± 0.11 cm for MW ablation at outputs of 25W, 35W, and 45W. For RF ablation, the corresponding values were 1.16 ± 0.09 and 1.26 ± 0.14 cm with electrodes having 2- and 3-cm active tips, respectively. The mean coagulation volumes were 2.27 ± 0.65, 2.85 ± 0.72, and 4.45 ± 0.47 cm3 for MW ablation at outputs of 25W, 35W, and 45W and 1.18 ± 0.30 and 2.29 ± 0.55 cm3 got RF ablation with 2- and 3-cm electrodes, respectively. MW ablations at 35W and 45W achieved significantly longer short-axis diameters than RF ablations (P < 0.05). The highest tissue temperature was achieved with MW ablation at 45W (P < 0.05). On histological examination, the extent of the ablation zone in MW ablations was less affected by tissue heterogeneity than that in RF ablations.

Conclusion

MW ablation appears to be advantageous with respect to the volume of ablation and the shape of the margin of necrosis compared with RF ablation in an ex vivo bovine udder.  相似文献   
995.
There are some features for an approved soccer ball by Fédération Internationale de Football Association (FIFA), such as properties of the material, mass, pressure, stitches, etc. Many of these features up to now have been studied; nevertheless, the mechanical properties of the soccer balls to date have not been well reported. The chief purposes of the current research, hence, were to calculate the mechanical properties of the soccer balls, i.e., linear elastic, nonlinear hyperelastic, and viscoelastic, at two different sizes, including 4 and 5 which are using for football and futsal, respectively. To do this, compressive and stress-relaxation loading were applied to 38 approved soccer balls to quantify the stress–strain as well as reduced relaxation function of the balls. The strain/displacement of the balls was also measured via a high-speed camera using Digital Image Correlation (DIC) technique. The results revealed the mean elastic modulus of 66 and 67 kPa for the football and futsal balls, respectively. In addition, the maximum stresses of the football and futsal balls were 16 and 13 kPa, respectively. The nonlinear mechanical response of the soccer balls were analyzed using hyperelastic material models, i.e., Mooney-Rivlin and Ogden. A Finite Element (FE) model was also developed to verify the hyperelastic data compared to the experimental ones and, remarkably, the numerical data were in consistence with the experimental data. Finally, Prony- series was employed to quantify the viscoelastic properties of the balls. During the game, a soccer ball can reach to a speed of 210 km/h that can damage the human eye; however, the injury detail still has not been studied.  相似文献   
996.
Identification of the population origin of an individual is very useful for crime investigators who need to narrow down a suspect based on specimens left at a crime scene. Single nucleotide polymorphisms of the Y chromosome (Y-SNPs) are a class of markers of interest to forensic investigators because many of the markers indicate regional specificity, thus providing useful information about the geographic origin of a subject. We selected seven informative Y-SNPs (M168, M130, JST021355, M96, P126, P196, and P234) to differentiate the three major population groups (East Asian, European, and African) and used them to develop forensic application. SNP genotyping was carried out by multiplex PCR reaction and multiplex single base extension (MSBE) reaction followed by capillary electrophoresis of extension products. This method can be used to assign a haplogroup from both degraded male DNA samples and DNA samples containing a mixture of female and male DNA through PCR primers that generate small amplicons (less than about 150 bp) and are highly specific for targets on the Y chromosome. The allelic state of each marker was definitively determined from a total of 791 males from the three major population groups. As expected, samples from the three major population groups showed Y-haplogroups common in the region of provenance: Y haplogroups C, D, and O for East Asians; IJ and R1 for Europeans; and AB and E for Africans.  相似文献   
997.
Proteus syndrome is a rare, sporadic, hamartomatous disorder manifesting with multifocal overgrowth of tissue. The features seem to develop most often during childhood. Vertebral overgrowth with severe spinal canal stenosis is unusual, although scoliosis with abnormal vertebral bodies is one of the typical features of Proteus syndrome. We report a case of Proteus syndrome with severe spinal canal stenosis, scoliosis, cervical kyphosis, and thoracic deformity with airway obstruction because of asymmetrical overgrowth of vertebrae and ribs associated with a tethered cord, lipomas, strawberry hemangioma, flat nasal bridge, and bilateral hypoplasty of the first metatarsal bones with hyperplasty of soft tissue.  相似文献   
998.
Annals of Nuclear Medicine - The efficacy of low-dose radioiodine therapy (RIT) for intermediate-risk or high-risk differentiated thyroid cancer (DTC) patients is controversial. Because of the...  相似文献   
999.
The aim of this study was to retrospectively evaluate the safety and efficacy of polidocanol sclerotherapy in pain relief for painful venous malformations (VMs). Thirty-one patients with painful VMs underwent polidocanol sclerotherapy. Pain intensity was assessed with an 11-point verbal numerical rating scale. Sclerotherapy was technically successful in 58 (98.3%) of 59 sessions. Twenty-six (89.7%) out of 29 patients experienced an improvement in pain after sclerotherapy at follow-up, a mean of 46 months after treatment. The mean pain score improved from 6.6?±?2.5 before treatment to 2.4?±?2.9 after treatment (P <.001). The factors that significantly influenced the therapeutic effect were size of lesion (P?=?.008), margin of lesion (P?=?.006), and stasis of sclerosant (P?=?.032). Adverse events included hypotension and bradycardia during the procedure. No major complication occurred. Polidocanol sclerotherapy is safe and most efficacious in providing pain relief for patients with small VMs (equal to or less than 10 cm in diameter), VMs with a well-defined margin, and VMs with good stasis of sclerosant during sclerotherapy.  相似文献   
1000.
Treatment options for patients with adult T cell leukemia/lymphoma (ATLL) who have relapsed disease after allogeneic hematopoietic stem cell transplantation (allo‐HSCT) are limited. To clarify which patients with ATLL are likely to benefit from these treatment options and to define patient populations for novel treatments, we performed a nationwide retrospective analysis of 252 Japanese patients who had relapsed ATLL after allo‐HSCT. Some long‐term survivors remained after tapering and withdrawal of immunosuppressive agents. Thirty‐six patients who received donor lymphocyte infusion had a better overall survival (OS) in comparison to those who did not [hazard ratio (HR), 0.63; 95% confidence interval (CI), 0.43‐0.93; P = .02], suggesting the efficacy of a graft‐versus‐ATLL (GvATLL) effect even after relapse. Multivariate analysis demonstrated that skin lesions at initial relapse of ATLL were independently associated with higher OS (HR, 0.41; 95% CI, 0.22‐0.74; P = .003), indicating that the skin is a susceptible target organ of GvATLL. This study suggested that enhancement of a GvATLL effect is a potential therapeutic option for relapsed disease after allo‐HSCT. Further investigations of incorporation of immune‐based approaches with new molecular target drugs into the therapeutic options of patients with ATLL before and after transplantation are warranted.  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