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   24220篇
  免费   2682篇
  国内免费   1791篇
耳鼻咽喉   200篇
儿科学   271篇
妇产科学   201篇
基础医学   2871篇
口腔科学   448篇
临床医学   3247篇
内科学   3352篇
皮肤病学   182篇
神经病学   1150篇
特种医学   841篇
外国民族医学   13篇
外科学   2420篇
综合类   4524篇
现状与发展   4篇
一般理论   2篇
预防医学   1789篇
眼科学   644篇
药学   2917篇
  20篇
中国医学   1719篇
肿瘤学   1878篇
  2024年   75篇
  2023年   459篇
  2022年   810篇
  2021年   1329篇
  2020年   1014篇
  2019年   919篇
  2018年   927篇
  2017年   874篇
  2016年   801篇
  2015年   1119篇
  2014年   1384篇
  2013年   1319篇
  2012年   1796篇
  2011年   2079篇
  2010年   1247篇
  2009年   1057篇
  2008年   1293篇
  2007年   1186篇
  2006年   1203篇
  2005年   1214篇
  2004年   872篇
  2003年   910篇
  2002年   830篇
  2001年   663篇
  2000年   570篇
  1999年   572篇
  1998年   350篇
  1997年   352篇
  1996年   223篇
  1995年   207篇
  1994年   162篇
  1993年   120篇
  1992年   127篇
  1991年   130篇
  1990年   113篇
  1989年   82篇
  1988年   61篇
  1987年   53篇
  1986年   47篇
  1985年   50篇
  1984年   33篇
  1983年   17篇
  1982年   6篇
  1981年   11篇
  1980年   4篇
  1979年   9篇
  1974年   3篇
  1968年   2篇
  1922年   1篇
  1920年   1篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
21.
The significance of hepatobiliary scintigraphy (HBS) for hepatic graft function assessment was established mostly on retrospective studies and was not widely recognized due to the lack of quantitative data and variation in accuracy. This prospective study was performed to investigate the effectiveness of quantitative HBS for assessing hepatocyte dysfunction and biliary complication in liver transplant recipients.In 57 recipients who had undergone orthotopic liver transplantation, a total of 67 dynamic 99mTc-EHIDA scans were performed and quantitative parameters including the hepatocyte extraction fraction (HEF), time to maximum hepatic radioactivity (Tmax), and time for peak activity to decrease by 50% (T1/2) were calculated. The scintigraphic results based on the 3 parameters were compared against the final diagnosis. A ROC curve analysis was carried out to identify the cutoff value of Tmax for diagnosis of biliary stricture. Correlation between the parameters of postoperative HBS and conventional biochemical liver function indices were also analyzed.Quantitative 99mTc-EHIDA HBS had an overall sensitivity of 94.12% (16/17), specificity of 93.33% (42/45), and diagnostic accuracy of 93.55% (58/62) for detecting hepatocyte dysfunction and biliary complication in liver transplant recipients. The recommended cutoff value of Tmax for diagnosis of post-transplant biliary stricture was set at 15.75 min with a sensitivity of 100.0% and a specificity of 94.0%. The scintigraphic parameters (HEF, Tmax) were statistically significantly associated with the conventional liver function parameters.Quantitative 99mTc-EHIDA HBS offers a noninvasive imaging modality with high sensitivity and specificity to diagnose hepatocyte dysfunction as well as distinguish between patients with or without biliary stricture following liver transplantation. Furthermore, HEF and Tmax values obtained from dynamic HBS show good correlation with conventional liver function parameters.  相似文献   
22.
颈肩背轴型反流皮瓣修复儿童颏颈瘢痕挛缩   总被引:2,自引:1,他引:1  
目的探讨修复儿童颏颈瘢痕挛缩一种实用而较理想的方法.方法以颈横动脉浅支为蒂,利用其与旋肩胛动脉皮支的丰富吻合,反流形成超长的轴型皮瓣,向前旋转修复瘢痕松解后的颈前创面.结果采用本皮瓣修复30例儿童颏颈瘢痕挛缩,其中18例随访2年,颈部活动自如,颌骨发育无明显异常,皮瓣色泽良好,效果令人满意.结论本皮瓣轴型血管恒定,反流灌注动脉压高有保证,供瓣面积充足,供区多可直接拉拢缝合,是修复儿童颏颈瘢痕挛缩的较理想方法.  相似文献   
23.
回顾性分析了5例本院发生的产科急性弥漫性血管内凝血(D IC)的临床资料。抢救产科D IC的关键为及时去除病因,产前D IC应积极解决分娩问题,产后大出血不止者应果断进行次全子宫切除或全子宫切除。  相似文献   
24.
皮瓣展平法在耳廓再造时扩张皮瓣感染中的应用   总被引:1,自引:0,他引:1  
目的探索耳廓再造时扩张皮瓣感染的处理方法。方法分析中国协和医科大学整形外科医院外耳冉造中心2003年1月~2005年12月耳廓再造时耳后扩张皮瓣发生感染,经皮瓣展平法处理,感染控制后进行耳再造的12例(12耳)患者的治疗情况。结果12例(12耳)患者手术顺利,术后恢复好,再造耳效果与无感染者无明显差异。结论皮瓣展平法是耳廓再造时扩张皮瓣感染较理想的处理方法。  相似文献   
25.
26.
OBJECTIVE: To prospectively determine the sonographic findings of nodular hyperplasia of the thyroid, to compare these with reported findings associated with malignancy, and to assess interobserver reliability. METHODS: Seventy thyroid nodules were scanned, and then biopsies of the nodules were performed under sonographic guidance with fine-needle cytologic analysis; in all cases images were reviewed by 2 experienced radiologists without knowledge of clinical outcome. Findings reported associated with malignancy were specifically assessed. Interobserver agreement between the expert and secondary readers for each finding was calculated by the kappa or weighted kappa statistic and the Fisher exact test of independence. RESULTS: There were 68 benign and 2 malignant nodules in a population of 63 female and 7 male patients. The mean benign nodule size was 2.9 cm; 60% were solid; 54% were hypoechoic; 59% were microlobulated or macrolobulated; 47% had central vascularity; 24% contained calcifications; and 82% were elliptical in shape. There was very good interobserver reliability for the presence of calcium (kappa = 0.91) and good agreement for the presence and location of vascularity (kappa = 0.75) and the amount of cystic components (kappa = 0.62; all P < .01). CONCLUSIONS: Sixty-nine percent of benign nodules had at least 1 finding reported previously as associated with malignancy. The interobserver reliability of the sonographic findings was good to very good for 3 of the 5 findings assessed.  相似文献   
27.
从土藿香根中得到两个二萜化合物,藿香酚(2)及异藿香酚(3)。经光谱解析(IR,UV,HRMS及NMR谱),确定它们的结构分别为11,14dihydroxy12methoxy19(4→3)abeoabieta4,(18),8,11,13tetraen7one(2)和11,14dihydroxy12methoxy19(4→3)abeoabieta3,8,11,13tetraen7one(3)藿香酚(2)为一新的化合物,而异藿香酚(3)系首次从天然界分离得到,二者为一对异构体。  相似文献   
28.
The 2.0-Å resolution x-ray crystal structure of a novel trimeric antibody fragment, a “triabody,” has been determined. The trimer is made up of polypeptides constructed in a manner identical to that previously described for some “diabodies”: a VL domain directly fused to the C terminus of a VH domain—i.e., without any linker sequence. The trimer has three Fv heads with the polypeptides arranged in a cyclic, head-to-tail fashion. For the particular structure reported here, the polypeptide was constructed with a VH domain from one antibody fused to the VL domain from an unrelated antibody giving rise to “combinatorial” Fvs upon formation of the trimer. The structure shows that the exchange of the VL domain from antibody B1-8, a Vλ domain, with the VL domain from antibody NQ11, a Vκ domain, leads to a dramatic conformational change in the VH CDR3 loop of antibody B1-8. The magnitude of this change is similar to the largest of the conformational changes observed in antibody fragments in response to antigen binding. Combinatorial pairing of VH and VL domains constitutes a major component of antibody diversity. Conformationally flexible antigen-binding sites capable of adapting to the specific CDR3 loop context created upon VH–VL pairing may be employed by the immune system to maximize the structural diversity of the immune response.  相似文献   
29.
本实验复制了莱姆病实验家兔模型,对血液生化23项进行了动态观察。结果表明,血液中谷丙转氨酶、γ-谷氨酰转肽酶、乳酸脱氢酶、谷草转氨酶、β-羟丁酸脱氢酶、磷酸肌酸激酶、胆固醇、尿素氮随病情加重而升高。葡萄糖、尿酸、磷随病情加重而减低。  相似文献   
30.
项红军  赵佐庆  李纪鹏  张志培 《医学争鸣》2002,23(21):1974-1977
目的:研究大鼠小肠缺血再灌注后后血中一氧化氮(NO),超氧化物歧化酶(SOD)的浓度变化以及肺组织中Bax,Bcl-2的表达,探讨小肠缺血再灌注后对肺组织的损伤,方法:建立小肠缺血再灌注模型,分对照 ,再灌注后0,30min,1,2h,1,3,7d共8组,于各时点检测血中Bax,Bcl-2的表达情况。结果:大鼠小肠缺血再灌注后NO浓度0min明显升高,2h时降低,随后升高,7d时达高峰,SOD浓度0min明显下降,2h 时升高,随后下降,7d时达最低,Bax,Bcl-2免疫阳性细胞主要位于肺组织中血管内皮细胞和肺泡上皮细胞,再灌注0min,Bax,Bcl-2阳性细胞率增多,30min时Bax,Bcl-2阳性细胞率均升高分别为17.1%和78.1%,Bcl-2表达高于Bax,两者差别显著(P<0.01),2h时降低,其后升高,7d时阳性细胞率达高峰分别为94.1%和83.4%,Bax表达明显高于Bcl-2,两者差异显著(P<0.01)。结论:大鼠小肠缺血再灌注后可引起血中NO,SOD的浓度变化和Bax及Bcl-2阳性细胞在肺组织中的表达改变并可能引起肺组织细胞凋亡和损伤。  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