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   2018384篇
  免费   153791篇
  国内免费   7279篇
耳鼻咽喉   26298篇
儿科学   65841篇
妇产科学   53462篇
基础医学   289109篇
口腔科学   56794篇
临床医学   181782篇
内科学   401937篇
皮肤病学   48130篇
神经病学   161180篇
特种医学   80522篇
外国民族医学   346篇
外科学   310277篇
综合类   44216篇
现状与发展   4篇
一般理论   591篇
预防医学   155247篇
眼科学   44482篇
药学   145465篇
  8篇
中国医学   4444篇
肿瘤学   109319篇
  2018年   22058篇
  2017年   17476篇
  2016年   20714篇
  2015年   22325篇
  2014年   30343篇
  2013年   46556篇
  2012年   58398篇
  2011年   62728篇
  2010年   38183篇
  2009年   35816篇
  2008年   59169篇
  2007年   63152篇
  2006年   64071篇
  2005年   61592篇
  2004年   59269篇
  2003年   57444篇
  2002年   55161篇
  2001年   97452篇
  2000年   100843篇
  1999年   82638篇
  1998年   24032篇
  1997年   21133篇
  1996年   21878篇
  1995年   21698篇
  1994年   20241篇
  1993年   18868篇
  1992年   65566篇
  1991年   64148篇
  1990年   62008篇
  1989年   59820篇
  1988年   55097篇
  1987年   54035篇
  1986年   51007篇
  1985年   49009篇
  1984年   37035篇
  1983年   31205篇
  1982年   19016篇
  1981年   17102篇
  1980年   16186篇
  1979年   33358篇
  1978年   24073篇
  1977年   20387篇
  1976年   18984篇
  1975年   20133篇
  1974年   23596篇
  1973年   22516篇
  1972年   20885篇
  1971年   19344篇
  1970年   17953篇
  1969年   16728篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Adenoviruses are commonly used as vectors in human clinical gene therapy trials. High doses of intravenous adenovirus vectors have been associated with development of thrombocytopenia of undetermined origin. Viral internalization requires the presence cell surface integrins, alpha(v)beta(3) or alpha(v)beta(5), that can blind ligands with a arginine-glycine-aspartic acid (RGD) sequence. This sequence is found in the adenovirus penton base. Platelets express the alpha(v)beta(3) integrin and other integrins that bind the RGD sequence of ligands such as fibrinogen, laminin, vitronectin, and von Willebrand factor (vWF). Platelet aggregation is mediated, in part, by the binding of the RGD sequence of fibrinogen to a platelet surface integrin, glycoprotein IIb/IIIa (GP IIb/IIIa). We investigated whether adenovirus particles could interfere with or potentiate agonist-induced platelet aggregation. Incubation of platelet-rich plasma with adenovirus under stirred conditions did not promote spontaneous aggregation. The addition of physiological platelet agonists, ADP, collagen, or epinephrine, induced platelet aggregation. However, the presence of adenovirus in a wide range of concentrations did not inhibit or potentiate agonist-induced aggregation. These results suggest that the adenovirus-associated thrombocytopenia observed in vivo is independent of a direct effect of the virus on platelet aggregation.  相似文献   
992.
BACKGROUND: The efficacy of nasal continuous positive airway pressure (nCPAP) as a prophylactic method for preventing cardiopulmonary complications after major vascular surgery has not been investigated. PATIENTS/METHODS: In a prospective randomized trial, 204 patients undergoing elective midline laparotomy for vascular surgery were randomized to receive standard therapy ( n=105) or additional prophylactic nCPAP ( n=99) for the first postoperative night. Postoperative oxygenation, incidence of severe cardiac, and pulmonary complications, length of intensive care surveillance and length of total postoperative hospital stay (LOS) were compared. RESULTS: Prophylactic nCPAP significantly reduced the number of patients with severe oxygenation disturbances defined as paO(2) < 70 mmHg with FiO(2) > or = 0.7 (5 versus 17, P=.01). There were no differences with respect to death, cardiac and pulmonary complications, length of intensive care surveillance or LOS. CONCLUSION: Prophylactic 12 h nCPAP significantly reduces the occurrence of postoperative oxygenation disturbances but has no effect on cardiac or pulmonary complications, need for intensive care, LOS or mortality after major vascular surgery.  相似文献   
993.
Interest in inguinal hernia surgery has increased significantly with the introduction of new operating techniques during the past decade. This multicenter study compared short-term results in patients treated by the laparoscopic transabdominal preperitoneal patch technique (TAPP; n=518) and the Shouldice technique (n=524). We evaluated demographics, operative data, complications, hospital stay, postoperative pain, use of analgesics, functional status, sick leave, and complaints up to 3 months postoperatively. The median operating time was shorter in the Shouldice group (55 vs. 65 min), but there were no significant differences in complication rates, and major complications were rare. The hospital stay was 1 day or less in over 98% of cases in both groups, but more operations were performed on outpatient basis in the Shouldice group. In the TAPP group postoperative pain and analgesic consumption were less, postoperative functional status was better, and sick leave was shorter (10 vs. 14 days). These results show that the two methods are equally safe and have few major complications. The TAPP operation is associated with less postoperative pain, better postoperative functional status, and shorter sick leave, but at the price of a longer operating time. Electronic Publication  相似文献   
994.
995.
996.
Salmus is a product of Salvia sclarea technology that is widely used in balneary practice. It is established that the analytical characteristics of salmus substance, as stipulated in the temporal pharmacopoeial article VFS 42-1530-85, are not objective and should not be used for evaluating the quality of the ready-to-use preparation and for monitoring the process of its manufacturing. TLC data show that salmus contains all components of sage oil (Russian State Standard GOST 3171-76) except for linalyl acetate. Qualitative specific color reactions on Silufol TLC plates showed for the first time the presence of flavonoids such as kaempferol, quercetin, juglanin, quercitrin, and rungioside and revealed one previously unknown substance, probably, of a flavonoid nature. The TLC data also showed the presence of condensed tannins and chlorophylls. It is suggested to perform quantitative analysis and identification of biologically active substances in salmus using methods for determining the content of reducing sugars (carbohydrates) and oxidizable components. New procedures for determining the sum of essential oils and flavonoids using the total content of extractable components have been developed and verified. It is suggested that these substances are among the main therapeutic components of salmus. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 39, No. 8, pp. 33 – 36, August, 2005.  相似文献   
997.
Tc-99m HMPAO was used to evaluate cerebral perfusion in a patient with tuberous sclerosis. The SPECT images demonstrated reduced HMPAO uptake in regions corresponding with MRI-confirmed locations of cortical tubers. These results indicate that the lesions are characterized by vascular perfusion deficits and support the hypothesis that cortical tubers result from developmental abnormalities of the embryonic central nervous system.  相似文献   
998.
999.
Esophageal pH monitoring is the accepted standard for the investigation of gastroesophageal reflux (GER) in adults. A postal questionnaire was sent to 912 United Kingdom paediatric physicians & surgeons. Five hundred forty-seven (61%) replied, with 124 (22.7%) currently using the technique, mostly in conjunction with barium swallow and/or esophagoscopy. The use of pH monitoring to quantify GER was also accepted in principal as being the best determinant of reflux by a further 186 (34%), but as yet was unavailable in their hospitals. Pediatricians were also questioned as to their management of children with GER. The majority were treated medically with a variety of antireflux medication, with only 237 (42%) referring cases for surgery.  相似文献   
1000.
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