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   12702篇
  免费   1468篇
  国内免费   38篇
耳鼻咽喉   104篇
儿科学   356篇
妇产科学   330篇
基础医学   1734篇
口腔科学   326篇
临床医学   1562篇
内科学   2326篇
皮肤病学   170篇
神经病学   1222篇
特种医学   667篇
外国民族医学   1篇
外科学   1780篇
综合类   202篇
一般理论   6篇
预防医学   1487篇
眼科学   201篇
药学   792篇
中国医学   15篇
肿瘤学   927篇
  2023年   90篇
  2022年   98篇
  2021年   188篇
  2020年   134篇
  2019年   174篇
  2018年   233篇
  2017年   186篇
  2016年   196篇
  2015年   260篇
  2014年   368篇
  2013年   495篇
  2012年   595篇
  2011年   580篇
  2010年   311篇
  2009年   354篇
  2008年   560篇
  2007年   547篇
  2006年   542篇
  2005年   533篇
  2004年   506篇
  2003年   446篇
  2002年   405篇
  2001年   378篇
  2000年   407篇
  1999年   360篇
  1998年   184篇
  1997年   207篇
  1996年   189篇
  1995年   151篇
  1994年   164篇
  1993年   135篇
  1992年   272篇
  1991年   240篇
  1990年   283篇
  1989年   292篇
  1988年   254篇
  1987年   247篇
  1986年   238篇
  1985年   248篇
  1984年   180篇
  1983年   148篇
  1982年   140篇
  1981年   125篇
  1980年   106篇
  1979年   151篇
  1978年   127篇
  1977年   109篇
  1976年   107篇
  1974年   102篇
  1973年   108篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
BACKGROUND: Unsedated office-based laser surgery (UOLS) of the larynx and trachea has significantly improved the treatment options for patients with laryngotracheal pathology including recurrent respiratory papillomas, granulomas, leukoplakia, and polypoid degeneration. UOLS delivered by flexible endoscopes has dramatically impacted office-based surgery by reducing the time, costs, and morbidity of surgery. OBJECTIVES: To review our experience with 443 laryngotracheal cases treated by UOLS. METHODS: The laser logbooks at the Center for Voice and Swallowing Disorders were reviewed for UOLS, and the medical and laryngological histories were detailed, as were the treatment modalities, frequencies, and complications. RESULTS: Of the 443 cases, 406 were performed with the pulsed-dye laser, 10 with the carbon-dioxide laser, and 27 with the thulium: yttrium-aluminum-garnet laser. There were no significant complications in this series. A review of indications and wavelength selection criteria is presented. CONCLUSION: Unsedated, office-based, upper aerodigestive tract laser surgery appears to be a safe and effective treatment option for many patients with laryngotracheal pathology.  相似文献   
92.
93.
94.
Twenty-five patients, 16 with gastric cancer and nine with colonic cancer, received TNO-6 30 mg m-2 every four weeks. No objective tumour response was recorded. Nausea and vomiting occurred in 21 patients and was severe in 17. Severe marrow suppression developed in five patients. Renal function was unaffected in all but one patient who developed renal failure, probably as a result of septicaemia. However, the renal tubular enzyme N-acetyl-beta-D-glucosaminidase was measured in six patients and showed a rise in all. In this study TNO-6 had no anti-tumour activity in gastrointestinal malignancy, but produced significant renal tubular damage.  相似文献   
95.
This paper examines medical malpractice law as it applies to medically necessary oral health care. The basic legal concepts and reported cases involving medically necessary oral health care are reviewed. It is concluded that dental professionals and consumer advocates must advance their educational and legislative advocacy efforts so that health professional colleagues and the public will become aware of the importance of these services and insurers will routinely include coverage of medically necessary oral health care in their medical and dental policies. While failure to provide medically necessary oral health care can be violative of patient rights and legally actionable, medical malpractice litigation should always be the behavior modifier of last resort.  相似文献   
96.
We examined the internal jugular veins in three groups of patients who had undergone (1) a functional neck dissection and radiotherapy, (2) a functional neck dissection alone, or (3) radiotherapy alone, using a noninvasive color Doppler ultrasound scan. The internal jugular veins were ultrasonically bilaterally normal in 18% of patients who had undergone a functional neck dissection and radiotherapy, in 88% of patients who had undergone a functional neck dissection alone, and in 57% of patients who had undergone radiotherapy alone. The combination of a functional neck dissection and radiotherapy significantly affected the internal jugular vein when compared with a functional neck dissection alone.  相似文献   
97.
98.
Tumor vascular signals in renal masses: detection with Doppler US   总被引:3,自引:0,他引:3  
Ramos  IM; Taylor  KJ; Kier  R; Burns  PN; Snower  DP; Carter  D 《Radiology》1988,168(3):633-637
The vascularity of 49 renal masses (26 malignant and 23 benign lesions) was investigated with duplex Doppler ultrasound. Doppler signals obtained at the margins of renal masses were defined as "tumor signals" when the Doppler-shifted frequency of the lesion exceeded the frequency shift in the ipsilateral main renal artery. These exceeded 2.5 kHz with a 3-MHz insonating frequency. Among the 26 renal masses that subsequently proved to be malignant, tumor signals were obtained in 15 of 18 (83%) untreated renal cell carcinomas, in three of four Wilms tumors, and in two patients with metastases to the kidney, but not in the one patient with lymphoma. None of the 23 benign renal masses demonstrated tumor signals. Tumor vascularity in malignant lesions gives rise to abnormal, high-velocity, Doppler-shifted signals that can help in the differential diagnosis of renal masses.  相似文献   
99.
100.
We have previously described regions of steric bulk tolerance in the aromatic-ring binding site of phenylethanolamine N-methyltransferase (PNMT, EC 2.1.1.28) for phenylethanolamine substrates and alpha-methylbenzylamine inhibitors. For bound substrates, this region is located in the vicinity of the para position of the aromatic ring, while for bound alpha-methylbenzylamine inhibitors, it is located in the region complementary to the meta position. In the present study, we sought to determine the preferred conformation of the biaryl portion of (m-phenylphenyl)- and (p-phenylphenyl)ethanolamine (4 and 5, respectively) as well as for m-phenyl- and p-phenyl-alpha-methylbenzylamine (7 and 8, respectively) for PNMT active site interactions. Planar derivatives of 4, 5, 7, and 8 were obtained through the synthesis of 2-(1-fluorenyl)-2-hydroxyethylamine (9), 2-(2-fluorenyl)-2-hydroxyethylamine (10), 1-(1-fluorenyl)ethylamine (11), and 1-(2-fluorenyl)ethylamine (12). The four fluorene derivatives were examined for in vitro activity as substrates and inhibitors of the PNMT-catalyzed reaction. As in the case of 4, 5, 7, and 8, we have observed a positional preference for the alkylamine side chain with respect to the biphenyl skeleton present in 9-12. Thus, fluorenylethanolamine 10 ("p-biphenyl") displays a Michaelis constant (Km = 26 microM) that is approximately 10 times lower than that for 9 ("m-biphenyl", Km = 297 microM); in the alpha-methylbenzylamine inhibitors, fluorenyl derivative 11 ("m-biphenyl", Ki = 4.14 microM) is approximately 40 times better than 12 ("p-biphenyl", Ki = 185 microM) for in vitro inhibition of PNMT. In each case, conformational restriction of the biaryl system present in 4, 5, 7, and 8, such that the aromatic rings are coplanar, resulted in enhanced affinity for the PNMT active site. Thus, conformational restriction of ethanolamine 5 (Km = 82 microM) as in 10 (Km = 26 microM) and alpha-methylbenzylamine 7 (Ki = 89 microM) as in 11 (Ki = 4.14 microM) leads, in each case, to a stronger enzyme-ligand dissociable complex. These results, in conjunction with others from these laboratories, indicate that the PNMT active site beyond the zone that interacts with the central aromatic ring portion of phenylethanolamine substrates and alpha-methylbenzylamine inhibitors is essentially a flat, hydrophobic pocket.  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