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   35975篇
  免费   1617篇
  国内免费   297篇
耳鼻咽喉   266篇
儿科学   654篇
妇产科学   412篇
基础医学   4777篇
口腔科学   1002篇
临床医学   2101篇
内科学   8951篇
皮肤病学   854篇
神经病学   2447篇
特种医学   1253篇
外科学   6434篇
综合类   145篇
一般理论   1篇
预防医学   988篇
眼科学   630篇
药学   2079篇
中国医学   123篇
肿瘤学   4772篇
  2024年   25篇
  2023年   203篇
  2022年   537篇
  2021年   879篇
  2020年   450篇
  2019年   648篇
  2018年   845篇
  2017年   655篇
  2016年   774篇
  2015年   800篇
  2014年   1077篇
  2013年   1370篇
  2012年   2227篇
  2011年   2607篇
  2010年   1474篇
  2009年   1213篇
  2008年   2229篇
  2007年   2464篇
  2006年   2303篇
  2005年   2480篇
  2004年   2392篇
  2003年   2391篇
  2002年   2398篇
  2001年   355篇
  2000年   296篇
  1999年   426篇
  1998年   575篇
  1997年   454篇
  1996年   431篇
  1995年   370篇
  1994年   323篇
  1993年   297篇
  1992年   208篇
  1991年   187篇
  1990年   182篇
  1989年   165篇
  1988年   144篇
  1987年   107篇
  1986年   100篇
  1985年   87篇
  1984年   104篇
  1983年   85篇
  1982年   71篇
  1981年   87篇
  1980年   82篇
  1979年   59篇
  1978年   41篇
  1977年   29篇
  1976年   24篇
  1975年   23篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
To study the effects of intra- and extrahepatic portal-systemic shunts on insulin degradation, 11 patients with liver cirrhosis and 7 noncirrhotic patients with liver disease were studied with percutaneous transhepatic catheterization. Insulin levels in portal and peripheral blood were measured simultaneously for 1-2 hr after intravenous administration of glucose. The degrees of intra- and extrahepatic portal-systemic shunting were measured with this technique using 131I-macroaggregated albumin and 99mTc-macroaggregated albumin. The amount of insulin secreted and insulin degraded were assessed from the areas under blood concentration curves for portal and peripheral blood. Insulin degradation was significantly reduced in cirrhotics compared to noncirrhotics with liver disease, although there was no difference in the amount of insulin secreted between these two groups. It was also correlated significantly with the degree of intrahepatic shunting but not with the degree of extrahepatic shunting. These results suggest that intrahepatic shunting plays an important role in the reduction of insulin degradation in cirrhosis.  相似文献   
993.
One hundred and thirty-four patients with vasoocclusive diseases were retrospectively tested for three kinds of antiphospholipid antibody (aPL). The mean age at onset of the disease in 58 patients with aPL was 43 years old. Seventeen, 11, and 9 patients were positive for the aCL IgA, IgM, and IgG isotypes, respectively. The rates of anti-phospholipid syndrome (APS) in patients with arterial (n=94), venous (n= 31), or both arterial and venous (n=9) occlusion were 45%, 29%, and 78%, respectively.The rates of APS in patients with autoimmune disease (n=13), thromboangiitis obliterans (TAO) (n= 36), arteriosclerosis obliterans (ASO) with lower leg involvement (n=8) or aortic arch syndrome (n=5), Raynaud's syndrome (n=15), aortitis syndrome (n= 13), ischemic heart disease (IHD) with young onset (n =12), and bilateral leg deep venous thrombosis (DVT) (n=10) were 77%, 46%, 13%, 80%, 40%, 62%, 33%, and 70%, respectively. The cumulative patency rate for reconstructive surgery in patients (n=13) with aCL was found to be considerably lower than that in those without aCL (n=13). From these results it was concluded that IgA was the most valuable aCL isotype for the diagnosis of APS and that aPL should be examined in patients with double-vessel occlusion, autoimmune disease, bilateral leg DVT, aortic arch syndrome, TAO, Raynaud's syndrome, or IHD with young onset. Furthermore, prophylaxis for graft failure is more strongly recommended for patients with aCL than for those without it.  相似文献   
994.
Neurofibromas in the small intestine are usually accompanied by von Recklinghausen's disease (neurofibromatosis), and usually originate in the intramuscular plexus of Auerbach. We present here a solitary neurofibroma, which caused an ileocolic intussusception, originating in the submucosal plexus of Meissner in a non-neurofibromatosis patient. To our knowledge, there is no previous report of a neurofibroma originating in the plexus of Meissner. This condition was clearly confirmed by macroscopic and microscopic evaluation.  相似文献   
995.
996.
Background: Several studies on left ventricular relaxation have been undertaken in the past: however, left atrial (LA) relaxation has not been fully evaluated. Hypothesis: The purpose of this study was to assess abnormalities in LA relaxation by evaluating pulmonary venous flow velocity and interatrial septal motion using transesophageal echocardiography. Methods: The subjects were 56 untreated patients in sinus rhythm, including 25 with previous myocardial infarction, 9 with hypertrophic cardiomyopathy, 11 with dilated cardiomyopathy, as well as 11 with chest pain syndrome as controls. Peak first systolic velocity (PVS1), peak atrial systolic velocity (PVA), and their time-velocity integrals (PVS1-I and PVA-I, respectively) were calculated from the pulmonary venous flow velocity. Results: The PVS1 and PVS1-I correlated negatively with the maximum LA dimension and mean pulmonary capillary wedge pressure, and correlated positively with the amplitude of the interatrial septal motion during LA relaxation and percent fractional LA relaxation. The PVA and PVA-I did not correlate with the mean pulmonary capillary wedge pressure. There was a weak positive correlation between PVA and PVS1, and a close positive correlation between the ratio of PVA to PVS1 and mean pulmonary capillary wedge pressure. Multiple regression analysis indicated that the PVS1 was most closely related to percent fractional LA relaxation, followed by mean pulmonary capillary wedge pressure. Conclusion: The PVS1 determined from the pulmonary venous flow velocity is closely related to parameters of LA relaxation which may be determined by transesophageal M-mode echocardiography, and the ratio of PVA to PVS1 is useful for noninvasive evaluation of LA pressure..  相似文献   
997.
998.
BACKGROUND/AIMS: Minimally invasive surgery, with its advantages of early return to normal activity and good cosmetic results, is an important goal in the treatment of patients with mucosal ulcerative colitis. The aim of this study was to compare outcomes utilizing a mini-laparotomy approach to total abdominal colectomy for mucosal ulcerative colitis with those of the conventional approach. METHODOLOGY: Eleven patients scheduled to undergo the first (total abdominal colectomy) of a 2 or 3-stage operation for mucosal ulcerative colitis via a mini-laparotomy between 1999 and 2001 were prospectively studied. The mini-laparotomy described here involves total abdominal colectomy performed through a skin incision shorter than 7 cm. Seven similar patients who underwent conventional laparotomy between 1995 and 1998 served as the control group. RESULTS: The mini-laparotomy approach was accomplished in 9 patients (81.8%). Patient characteristics between cases and controls were similar. Postoperative intervals until standing, walking, flatus, urinary catheter removal, and tolerance of solid diet were significantly shorter in the mini-laparotomy group (P = 0.031, P = 0.023, P = 0.0033, P = 0.0093, and P = 0.023, respectively). CONCLUSIONS: A mini-laparotomy approach to total abdominal colectomy appears feasible and safe in selected patient with mucosal ulcerative colitis and poses an attractive alternative to conventional laparotomy in patients similar to those presented here.  相似文献   
999.
Two new triterpenoids, 20(21)-dehydrolucidenic acid A (1) and methyl 20(21)-dehydrolucidenate A (2), and five new 20-hydroxylucidenic acids, 20-hydroxylucidenic acid D(2) (3), 20-hydroxylucidenic acid F (4), 20-hydroxylucidenic acid E(2) (5), 20-hydroxylucidenic acid N (6), and 20-hydroxylucidenic acid P (7), were isolated from the fruiting body of the fungus Ganoderma ludicum, and their structures were established on the basis of spectroscopic methods.  相似文献   
1000.
Eleven new indole alkaloids, in addition to the previously reported rhazinal (1), and 14 other known alkaloids, were obtained from the Malayan Kopsia singapurensis, viz., kopsiloscines A-F (2-7), 16-epikopsinine (8), kopsilongine- N-oxide (9), 16-epiakuammiline (10), aspidophylline A (11), and vincophylline (12). The structures of these alkaloids were determined using NMR and MS analyses. Rhazinal (1), rhazinilam (17), and rhazinicine (18) showed appreciable cytotoxicity toward drug-sensitive as well as vincristine-resistant KB cells, while kopsiloscines A (2), B (3), and D (5) and aspidophylline A (11) were found to reverse drug-resistance in drug-resistant KB cells.  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