全文获取类型
收费全文 | 160196篇 |
免费 | 16350篇 |
国内免费 | 9047篇 |
专业分类
耳鼻咽喉 | 1557篇 |
儿科学 | 3045篇 |
妇产科学 | 1989篇 |
基础医学 | 15260篇 |
口腔科学 | 3388篇 |
临床医学 | 18893篇 |
内科学 | 22620篇 |
皮肤病学 | 1800篇 |
神经病学 | 7869篇 |
特种医学 | 6216篇 |
外国民族医学 | 46篇 |
外科学 | 17298篇 |
综合类 | 28961篇 |
现状与发展 | 24篇 |
一般理论 | 18篇 |
预防医学 | 13292篇 |
眼科学 | 4440篇 |
药学 | 17175篇 |
142篇 | |
中国医学 | 10157篇 |
肿瘤学 | 11403篇 |
出版年
2024年 | 636篇 |
2023年 | 2366篇 |
2022年 | 5711篇 |
2021年 | 7550篇 |
2020年 | 5866篇 |
2019年 | 4757篇 |
2018年 | 5004篇 |
2017年 | 4916篇 |
2016年 | 4572篇 |
2015年 | 6806篇 |
2014年 | 8540篇 |
2013年 | 9105篇 |
2012年 | 13118篇 |
2011年 | 13597篇 |
2010年 | 10162篇 |
2009年 | 8643篇 |
2008年 | 10037篇 |
2007年 | 9788篇 |
2006年 | 9060篇 |
2005年 | 7692篇 |
2004年 | 6490篇 |
2003年 | 5838篇 |
2002年 | 4893篇 |
2001年 | 3978篇 |
2000年 | 3127篇 |
1999年 | 2358篇 |
1998年 | 1119篇 |
1997年 | 1095篇 |
1996年 | 817篇 |
1995年 | 724篇 |
1994年 | 660篇 |
1993年 | 454篇 |
1992年 | 744篇 |
1991年 | 682篇 |
1990年 | 637篇 |
1989年 | 539篇 |
1988年 | 484篇 |
1987年 | 439篇 |
1986年 | 411篇 |
1985年 | 366篇 |
1984年 | 253篇 |
1983年 | 234篇 |
1982年 | 147篇 |
1981年 | 113篇 |
1980年 | 116篇 |
1979年 | 165篇 |
1978年 | 95篇 |
1977年 | 103篇 |
1976年 | 72篇 |
1974年 | 87篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
Ganapathy A Prasad Kenneth K Wang Lori S Lutzke Jason T Lewis Schuyler O Sanderson Navtej S Buttar Louis M Wong Kee Song Lynn S Borkenhagen Lawrence J Burgart 《Clinical gastroenterology and hepatology》2006,4(2):173-178
BACKGROUND & AIMS: The aim of this study was to assess the validity of frozen section analysis of endoscopic mucosal resection (EMR) specimens from Barrett's esophagus as compared with permanent sections for the detection of neoplasia. Frozen sections help to give immediate feedback for surgical procedures. It has not been determined whether EMR can be adequately interpreted by using frozen sections to aid endoscopists in completely resecting neoplastic lesions. METHODS: EMR specimens from Barrett's esophagus with high-grade dysplasia (HGD) and/or carcinoma were tested by frozen section. Pathologists evaluated EMR specimens for the depth of invasion as well as the appearance of clear margins of resection. The kappa statistic was calculated to assess the degree of agreement between the frozen section and permanent section diagnoses. RESULTS: Twenty-three consecutive patients underwent 30 EMRs with frozen section diagnosis. Frozen section revealed a carcinoma in 7 specimens (23%) and dysplasia in 20 (66%). Permanent sections found carcinoma in 8 specimens (26%), dysplasia in 19 specimens (63%), and normal or nondysplastic Barrett's esophagus in the remainder. The kappa statistic for the depth of invasion of EMR specimens was 0.93 (near perfect agreement). The kappa statistic for the margins of the EMR specimens was 0.80 (excellent agreement). CONCLUSIONS: This study indicated that frozen section analysis of esophageal EMR specimens is valid as compared with permanent section. This technique might allow rapid evaluation about the degree and depth of involvement of cancers. This allows physicians to make decisions regarding further therapy if margins are involved or decrease the use of EMR for histologically benign-appearing lesions. 相似文献
93.
关节镜下应用“微骨折”方法修复关节软骨缺损 总被引:3,自引:3,他引:0
目的:探讨关节镜下应用“微骨折”技术对膝关节全层关节软骨缺损修复的效果。方法:对68例全层关节软骨缺损患者进行随机分组:实验组(35例),男17例,女18例,平均年龄35.1岁,采用关节清理后应用“微骨折”技术进行处理,即利用骨刀设计的特性和适度的锤击力量造成软骨下的骨组织微小骨折,刺激软骨生长。对照组(33例),男17例,女16例,平均年龄31.6岁,仅作关节清理术。结果:术后随访6~18个月,平均8.6个月,按Lysholm评分标准,实验组明显优于对照组(P<0.01)。结论:关节镜下应用“微骨折”技术能够显著减轻关节疼痛,增加关节活动度,改善关节功能,是一种简单有效的修复全层关节软骨缺损方法。 相似文献
94.
Statin, a HMG-CoA reductase inhibitor, was shown to increase BMP-2 gene expression for bone formation, by blocking the mevalonate pathway in cholesterol production. We investigated the effect of naringin, a flavonoid available commonly in citrus fruits, which was also a HMG-CoA reductase inhibitor, in UMR 106 osteoblastic cell line in vitro. The control group consisted of cells cultured without any intervention for different time intervals (24 h, 48 h, and 72 h), whereas the experimental (naringin) group consisted of cells cultured with naringin of different concentrations (0.001 micromol/L, 0.01 micromol/L, and 0.1 micromol/L) for the same time intervals of the control. Colorimetric Tetrazolium (MTT) assay, total protein content assay, and alkaline phosphatase activity were used to measure the cellular activities. Results for the naringin group showed an increase in MTT assay compared with the control and the effect was dose dependent. At high concentration (0.1 micromol), the increases ranged from 60% to 80%. In the total protein content assay, naringin also showed an increase compared with control and the effect was also dose dependent. At high concentration (0.1 micromol), the increases ranged from 9% to 20%. In the alkaline phosphatase activity assay, naringin at high concentration (0.1 micromol) significantly increased the activity up to 20%. In conclusion, naringin significantly increased bone cell activities in vitro. This is the first study specifically attempted to investigate the effect of naringin on bone cell activities. Besides statin, this provided another example of mevalonate pathway blockage in the cholesterol production pathway by HMG-CoA reductase inhibition will increase the bone cell activities. 相似文献
95.
H Maezawa K H Wong M Urano 《International journal of radiation oncology, biology, physics》1992,24(3):533-541
A cultured line of murine skin epithelial cells was established to investigate the potential use of cultured cells as an alternative to animal use in radiation research. C3Hf/Sed newborn mouse skin cells have been successfully cultured in serum- and Ca(2+)-free medium with no terminal differentiation to keratinized cells. Presently, more than 25 passages have passed with no loss of stem cell capability. The radiosensitivity and repair of sublethal and potentially lethal radiation damages were investigated in this epithelial cell line. The population cell doubling time was 25 +/- 2.9 hr at 37 degrees C. The clonal growth of epithelial cells after irradiation was performed in the serum-free medium in the presence of lethally irradiated skin fibroblasts. Single dose survival curves of exponentially growing epithelial cells were investigated from the seventh to the twenty-third passages, and no significant changes in radiosensitivity and doubling time were found. The confluent epithelial cells also showed an identical sensitivity to radiation. The alpha/beta ratios of survival curves fitted by the linear quadratic model were 6.1 +/- 1.0 and 5.9 +/- 1.3 Gy for cells in exponential and confluent phases, respectively. The survival curve of epithelial cells left in confluence for 8 hr after irradiation showed a smaller beta value than that of cells plated immediately after irradiation with a resultant alpha/beta ratio of 9.5 +/- 3.8 Gy. This alpha/beta ratio was identical to those found in many animal experiments, suggesting a potential use of this cell line as an alternative to animal use. The magnitude of repair of sublethal damage following 6 Gy was greater than that following 3.9 Gy. Survival curves were also obtained following twice-a-day irradiations with no sign of rapid repopulation. These results are discussed by comparing with published in vivo and in vitro data. 相似文献
96.
97.
98.
Alex Zacharek Jieli Chen Xu Cui Ang Li Yi Li Cynthia Roberts Yifan Feng Qi Gao Michael Chopp 《Journal of cerebral blood flow and metabolism》2007,27(10):1684-1691
Bone marrow stromal cells (MSCs) increase vascular endothelial growth factor (VEGF) expression and promote angiogenesis after stroke. Angiopoietin-1 (Ang1) and its receptor Tie2 mediate vascular integrity and angiogenesis as does VEGF and its receptors. In this study, we tested whether MSC treatment of stroke increases Ang1/Tie2 expression, and whether Ang1/Tie2 with VEGF/ vascular endothelial growth factor receptor 2 (VEGFR2) (Flk1), in combination, induced by MSCs enhances angiogenesis and vascular integrity. Male Wistar rats were subjected to middle cerebral artery occlusion (MCAo) and treated with or without MSCs. Marrow stromal cell treatment significantly decreased blood-brain barrier (BBB) leakage and increased Ang1, Tie2, and occludin (a tight junction protein) expression in the ischemic border compared with MCAo control. To further test the mechanisms of MSC-induced angiogenesis and vascular stabilization, cocultures of MSCs with mouse brain endothelial cells (MBECs) or astrocytes were performed. Supernatant derived from MSCs cocultured with MBECs significantly increased MBEC expression of Ang1/Tie2 and Flk1 compared with MBEC alone. Marrow stromal cells cocultured with astrocytes also significantly increased astrocyte VEGF and Ang1/Tie2 expression compared with astrocyte culture alone. Conditioned media from MSCs alone, and media from cocultures of MSCs with astrocytes or MBECs, all significantly increased capillary tube-like formation of MBEC compared with control Dulbecco's modified Eagle's medium media. Inhibition of Flk1 and/or Ang1 significantly decreased MSC-induced MBEC tube formation. Knockdown of Tie2 expression in MBECs significantly inhibited MSC-induced tube formation. Our data indicate MSC treatment of stroke promotes angiogenesis and vascular stabilization, which is at least partially mediated by VEGF/Flk1 and Ang1/Tie2. 相似文献
99.
目的 探讨质子磁共振波谱(1HMRS)在诊断创伤后应激障碍(post traumatic stress disorder,PTSD)患者海马神经元异常中的价值。方法 对19例PTSD患者及19例健康对照组行常规MRI和1HMRS检查。结果 PTSD患者MRI检查未出现信号的异常。19例患者两侧海马均显示NAA/Cr明显减低,与健康对照组相比,差异有统计学意义(P〈0.01);而患者两侧海马的Cho/Cr与健康对照组相比,差异无统计学意义(P〉0.05)。结论 1HMRS揭示了PTSD时海马存在着神经元的丢失或功能紊乱,而这些改变是构成PTSD的神经生物学基础之一。 相似文献
100.