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   128785篇
  免费   11276篇
  国内免费   6625篇
耳鼻咽喉   1224篇
儿科学   1958篇
妇产科学   2930篇
基础医学   13447篇
口腔科学   2677篇
临床医学   15980篇
内科学   20152篇
皮肤病学   1590篇
神经病学   6395篇
特种医学   4199篇
外国民族医学   40篇
外科学   13343篇
综合类   19309篇
现状与发展   20篇
一般理论   18篇
预防医学   9428篇
眼科学   3442篇
药学   13461篇
  115篇
中国医学   6538篇
肿瘤学   10420篇
  2024年   347篇
  2023年   1716篇
  2022年   4017篇
  2021年   5438篇
  2020年   4055篇
  2019年   3668篇
  2018年   3940篇
  2017年   3705篇
  2016年   3308篇
  2015年   5236篇
  2014年   6733篇
  2013年   6945篇
  2012年   10123篇
  2011年   10871篇
  2010年   7481篇
  2009年   6151篇
  2008年   7783篇
  2007年   7726篇
  2006年   7317篇
  2005年   6690篇
  2004年   4840篇
  2003年   4401篇
  2002年   3653篇
  2001年   3090篇
  2000年   2847篇
  1999年   2643篇
  1998年   1311篇
  1997年   1220篇
  1996年   986篇
  1995年   949篇
  1994年   885篇
  1993年   504篇
  1992年   889篇
  1991年   801篇
  1990年   668篇
  1989年   569篇
  1988年   525篇
  1987年   450篇
  1986年   357篇
  1985年   284篇
  1984年   184篇
  1983年   167篇
  1982年   95篇
  1981年   93篇
  1979年   140篇
  1978年   111篇
  1977年   83篇
  1974年   94篇
  1973年   72篇
  1972年   87篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
To investigate the relationship between age and renal vascular resistance and to establish nomative data of the systolic/diastolic ratio (S/D ratio), pulsatility index (PI), and resistant index (RI) of the renal artery in the normal pediatric population, we studied 252 normal children aged newborn to 13 years (a total of 449 kidneys) with a color Doppler unit. After the normality of the kidney was established, color flow mapping was performed to localize the segmental portion of the renal artery. Flow velocity waveforms were then obtained by pulsed Doppler, and S/D ratio, PI, and RI were calculated. Multiple regression analysis confirmed the age dependence of the S/D ratio, PI, and RI of the renal artery in normal children. Renal vascular resistance continuously declines after birth and stabilizes at the age of 102 – 130 months. Normative data for S/D ratio, PI, and RI of the renal artery in normal children were established for each age group. Since renal vascular resistance decreases with age and stabilizes at 8 – 10 years, we suggest using different normal ranges for each age group when studying renal vascular resistance in pediatric patients. Received October 5, 1995; received in revised form and accepted April 24, 1996  相似文献   
92.
Clinically significant contact lens induced corneal warpage is seen in a small proportion of soft and rigid contact lens wearers. Previous studies using the keratometer have found no correlation between the fit of the lens and the induced topographic changes. In this study, using computer-assisted topographic analysis, seven eyes (four patients) with rigid contact lens-induced corneal warpage were noted to have topographic abnormalities that correlated with the decentered resting position of the contact lens on the cornea. The warpage topography for each of these corneas was characterized by a relative flattening of the cornea underlying the resting position of the contact lens. Lenses that rode high, for example, produced flattening superiorly and resulted in a relatively steeper contour inferiorly that simulated the topography of early keratoconus patients who had not worn contact lenses. After discontinuing contact lenses the corneal topography returned to a normal pattern in five eyes. Two eyes retained asymmetry that is not characteristic of normal corneas. Up to 6 months was required for the corneas to return to a stable topography after contact lens wear was discontinued.  相似文献   
93.
本文应用透射电镜观察比较日本血吸虫尾蚴和皮肤型童虫的体壁、腺体和消化道的超微结构。结果表明,从尾蚴至皮肤型童虫转变过程,其体壁和钻腺的超微结构发生明显改变,但头腺及消化道则未见明显变化。这些变化与其相应的微环境密切相关。  相似文献   
94.
Expression of major histocompatibility complex class II antigens was investigated in the normal lungs and in lung allografts of mongrel dogs after single-lung transplantation. Cryostat sections were stained with an indirect immunoperoxidase technique that used B1F6 and 7.5.10.1 as anti-MHC class II monoclonal antibodies. In the normal lungs and native lungs of the recipient dogs after single-lung transplantation, only some cells of lymphoid tissue and macrophages/dendritic cells were MHC class II-positive. During acute rejection, increased infiltration with MHC class II-positive cells in perivascular, peribronchial, and interstitial areas and intraalveolar spaces was found in lung allografts. In addition, expression of MHC class II antigens was induced on the bronchial epithelium and vascular endothelium. Induced expression of MHC class II antigens on the bronchial epithelium and vascular endothelium in rejecting lung allografts was found as early as two days after single-lung transplantation. The intensity of MHC class II antigen expression on bronchial epithelium and vascular endothelium in graft lungs increased with the progression of rejection response and directly correlated with the bronchoalveolar lavage fluid (BALF) levels of biochemical markers, as tumor necrosis factor alpha, gamma-interferon (IFN-gamma), interleukin 2 (IL-2) and soluble interleukin 2 receptor (SIL-2R). Abnormal expression of MHC class II antigens on bronchial epithelium and vascular endothelium and abnormal elevation of BALF levels of the cytokines in lung allografts could be prevented by cyclosporine (CsA) treatment. Our results suggested that MHC class II antigen expression could be induced on the bronchial epithelium and vascular endothelium of canine lung allografts during acute rejection. This abnormal expression of MHC class II antigens on bronchial epithelium and vascular endothelium of graft lungs may serve as a specific index for diagnosis of lung allograft rejection when infection as an inducing factor can be excluded. Furthermore, bronchial epithelium and vascular endothelium of lung allografts have become MHC class II-positive, and are likely to be the targets for low-grade rejection, resulting in the development of bronchiolitis obliterans and occlusive vascular disease in lung allografts.  相似文献   
95.
目的:研究中国汉族群体中α艾杜糖苷酶基因D4S111位点的遗传多态性。方法:采用扩增片段长度多态性(AmpFLP)分析技术,检测了广州地区汉族无血缘关系健康个体97名。结果:D4S111位点,在97名无关个体中发现5个等位基因和9种基因型,等位基因片段长度为830~510bp,基因频率为00052~03608,PIC为05966,杂合性为078。结论:中国汉族群体中D4S111位点具有高度多态性,并与其它种族间存在差异性。  相似文献   
96.
真皮下血管网岛状皮瓣抗菌力的实验研究   总被引:2,自引:0,他引:2  
为研究真皮下血管网薄皮瓣用于感染创面的可行性,在家猪臀部两侧分别形成以旋髂深血管主干分支为蒂的传统岛状皮瓣和远侧50%修薄的真皮下血管网岛状皮瓣。用细菌计数、吖啶橙荧光染色测定白细胞吞噬指数和白细胞内杀菌率,应用激光多普勒、墨汁灌注、透明标本等方法,对两种皮瓣的抗菌力作自身对照研究。结果表明,真皮下血管网岛状皮瓣的抗菌力明显降低,可能与皮瓣修薄后血供减少,白细胞功能相应降低有关。  相似文献   
97.
98.
Elevation of prostaglandins and protein in the aqueous humor is an immediate response to Yag-laser anterior capsulotomy. There was a significant correlation between prostaglandins and thromboxane to the elevation of intraocular pressure. The elevation of protein concentration was proportional to the elevation of prostaglandin F1, but not to thromboxane. The biochemical changes in the aqueous humor were more severe as laser power was increased above 3 mj. While the role of prostaglandins in the elevation of intraocular pressure is uncertain, the present data recommend the selection of laser power below 3 mj to avoid pressure rise instead of inhibition of all prostaglandin synthesis by medication.  相似文献   
99.
本文作者比较了不同时期的纸质病案的使用率,讨论了旧病案的缺点,如难于保存,占用空间及实用价值不大.作者提出了改进保存病案的办法.  相似文献   
100.
目的 探讨手助腹腔镜肝部分切除术治疗原发性肝癌的方法和应用价值。方法 经临床筛选的第Ⅱ、Ⅲ、Ⅵ段或边缘型的原发性肝癌6例,在腹腔镜辅助下.应用手助器、超声刀、切割器等特殊器械进行腹腔镜下肝癌切除术。结果 6例患者均成功完成手术,包括肝Ⅱ、Ⅲ段切除,Ⅵ段切除及非规则性肝段切除术,手术时间80~130min,术后住院6~9d,手术出血150~700ml,无中转开腹手术,无并发症。术后随访6~15个月,2例分别于手术后3和4个月肝内复发,其余4例随访至今无复发。结论 在经过临床选择的病例中,手助腹腔镜下作肝部分切除术治疗原发性肝癌是安全、可行的手术方式。  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