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   19451篇
  免费   1258篇
  国内免费   54篇
耳鼻咽喉   231篇
儿科学   563篇
妇产科学   337篇
基础医学   2721篇
口腔科学   520篇
临床医学   1858篇
内科学   3745篇
皮肤病学   550篇
神经病学   1675篇
特种医学   1028篇
外国民族医学   25篇
外科学   2375篇
综合类   158篇
一般理论   6篇
预防医学   2135篇
眼科学   203篇
药学   1606篇
中国医学   56篇
肿瘤学   971篇
  2022年   140篇
  2021年   261篇
  2020年   170篇
  2019年   236篇
  2018年   303篇
  2017年   240篇
  2016年   291篇
  2015年   350篇
  2014年   429篇
  2013年   625篇
  2012年   823篇
  2011年   859篇
  2010年   494篇
  2009年   515篇
  2008年   801篇
  2007年   781篇
  2006年   815篇
  2005年   773篇
  2004年   702篇
  2003年   689篇
  2002年   653篇
  2001年   574篇
  2000年   622篇
  1999年   532篇
  1998年   269篇
  1997年   207篇
  1996年   187篇
  1995年   205篇
  1994年   246篇
  1993年   295篇
  1992年   645篇
  1991年   558篇
  1990年   487篇
  1989年   343篇
  1988年   341篇
  1987年   313篇
  1986年   260篇
  1985年   288篇
  1984年   240篇
  1983年   166篇
  1982年   143篇
  1981年   145篇
  1979年   170篇
  1978年   146篇
  1977年   135篇
  1976年   149篇
  1975年   152篇
  1974年   184篇
  1973年   164篇
  1971年   144篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Bonfanti  R; Furie  BC; Furie  B; Wagner  DD 《Blood》1989,73(5):1109-1112
PADGEM protein (PADGEM), also known as GMP140, is a platelet alpha- granule membrane protein that is translocated to the external membrane after platelet activation. Although the biosynthesis of this protein was originally thought to be confined to megakaryocytes, the synthesis of PADGEM in endothelial cells was recently demonstrated (McEver et al: Blood 70:1974a, 1987). We now describe the subcellular localization of this protein in endothelial cells. Immunofluorescence staining of permeabilized human umbilical vein endothelial cells with KC4, a well characterized monoclonal antibody to PADGEM, showed positively stained elongated structures similar in distribution and shape to Weibel-Palade bodies. Their identity as Weibel-Palade bodies was confirmed by double label immunofluorescence using KC4 and a polyclonal antiserum to von Willebrand factor (vWf), a protein known to be specifically stored in these organelles. All Weibel-Palade bodies were found to contain PADGEM. In contrast to strong perinuclear staining produced with anti- vWf antibodies, no significant perinuclear staining was obtained with KC4, indicating that relatively little PADGEM is present in the endoplasmic reticulum and in the Golgi apparatus. In endothelial cells treated with secretagogues that stimulate vWf release the elongated structures positive for PADGEM disappeared, further identifying these structures as Weibel-Palade bodies. This observation extends the parallels between Weibel-Palade bodies and alpha-granules and suggests a possible functional association between vWf and PADGEM.  相似文献   
12.
Two new naphtho-pyrone glycosides, 9-[(beta-D-glucopyranosyl-(1----6)-O-beta-D-glucopyranosyl)oxy]-10- hydroxy-7-methoxy-3-methyl-1H-naphtho[2,3-c]pyran-1 -one (5) and 6-[(alpha-apiofuranosyl-(1----6)-O-beta-D-glucopyranosyl)oxy]- rubrofusarin (6), together with cassiaside (3) and rubrofusarin-6-beta-gentiobioside (4) were isolated from the seeds of Cassia tora L. Their structures were elucidated on the basis of chemical and spectral data. The naphtho-gamma-pyrone glycosides (3, 4, and 6) were found to have significant hepato-protective effects against galactosamine damage, which were higher than that of silybin from Silybum marianum.  相似文献   
13.
Abstract:  In Sweet's syndrome, the essential features are the characteristic morphology of the lesions, their histologic appearance, the dramatic response to corticosteroids and the absence of scarring. We report an 8-month-old infant in whom Sweet's syndrome was diagnosed and who developed acquired cutis laxa in the skin lesions.  相似文献   
14.
Transcranial Magnetic Stimulation (TMS) induces electrical currents in the brain to stimulate neural tissue. This article reviews our present understanding of TMS methodology, focusing on its biophysical foundations. We concentrate on how the laws of electromagnetic induction apply to TMS; addressing issues such as the location, area (i.e., focality), depth, and mechanism of TMS. We also present a review of the present limitations and future potential of the technique.  相似文献   
15.
16.
PURPOSE: To investigate whether balloon angioplasty of the superficial femoral artery (SFA) increases serum levels of C5a and whether C5a predicts risk of restenosis. METHODS: C5a antigen was measured at baseline and 8 hours after intervention in 131 consecutive patients (76 women; median age 72 years) with intermittent claudication who underwent successful primary SFA balloon angioplasty. Patients were followed for a median 10 months [interquartile range (IQR) 6 to 14] for the occurrence of >50% restenosis by duplex ultrasound. RESULTS: Median C5a levels increased significantly from 39.7 ng/mL (IQR 27.8 to 55.0) at baseline to 53.8 ng/mL (IQR 35.6 to 85.1, p<0.001) 8 hours post intervention. During the follow-up period, 70 (53%) patients developed restenosis. Increasing levels of C5a (quartiles) at baseline were significantly associated with an increased risk for restenosis (p=0.0092). Adjusted hazard ratios (95% confidence intervals) for restenosis with increasing quartiles of baseline serum C5a levels were 1.24 (0.60 to 2.58), 1.93 (0.95 to 3.93), and 2.08 (1.02 to 4.21), respectively, compared to the lowest quartile. This effect was independent of nonspecific inflammation as reflected by plasma levels of C-reactive protein. CONCLUSION: Inflammatory mechanisms play a major role in the development of restenosis after angioplasty. The complement component C5a exerts strong chemotactic and proinflammatory effects. Enhanced complement activation prior to PTA, as measured by higher levels of C5a, was significantly associated with restenosis after SFA balloon angioplasty. Pathways of complement inhibition thus may be worth investigating with respect to improving patency rates.  相似文献   
17.
Rupture of the Achilles tendon is typically associated with sportive activities with increasing tendency; it occurs most commonly in the third to fourth decade of life with a male-to-female ratio of 5–10:1. Ruptures are caused predominantly by a sudden, unexpected overextension of the tendon while direct trauma is less frequent. The recommended treatment of the injury remains controversial. In Germany, due to the good functional results, the open surgical repair represents the standard therapy since many years. The open suture technique offers the advantage of a lower re-rupture rate but is associated with the risk of wound-related complications including infection. By percutaneous suture techniques a significant decrease in the rate of infections and complications in wound healing could be achieved by minimal-access with reduced soft tissue trauma; on the other hand an increased rate of lesions of the sural nerve is reported. Dynamic imaging assessment of ultrasound or MRI allows a more accurate localisation of the ruptured ends of the tendons which is the prerequisite for the non-operative primary functional treatment of Achilles tendon ruptures. This conservative treatment regime is recommended when adaptation of the ends of the ruptured tendon is possible in 20° plantar flexion of the foot. Moreover, the desired level of daily activity and the patients’ degree of compliance has to be considered. Operative management should be avoided in the elderly patient or patients with risk factors like immunosuppressive therapy, diabetes mellitus, steroid use or failure to comply.  相似文献   
18.
OBJECTIVE: Prospectively to compare lymphatic drainage after ultrasonic dissection, an electrocoagulation technique and sharp dissection in the groin during surgery for recurrent sapheno-femoral incompetence. DESIGN: Prospective, randomised study comparing three surgical techniques. METHODS: Thirty-six consecutive patients undergoing surgery for recurrent sapheno-femoral incompetence were randomised. Twelve patients underwent dissection with ultrasound, 12 with electrocoagulation and 12 controls had sharp dissection with ligation of scar and lymphatic tissue using absorbable suture material. RESULTS: The mean drain output per patient was 13.5 ml in the ultrasonic group, 15.4 ml in the electrocoagulation group and 8.3 ml in the suture ligation group. Six minor cases of lymphatic leakage occurred in the ultrasonic group. This resulted in no clinical problem. There were no other significant differences between the three groups. CONCLUSIONS: There is no detectable advantage for the use of ultrasound or electrocoagulation in recurrent saphenous high ligation compared to sharp dissection.  相似文献   
19.
Peripheral chemoreceptors (carotid bodies) are the main sensing organs for hypoxaemia. During carotid surgery, the carotic body in the bifurcation of the common carotid artery is often involved and damaged or destroyed. Animals lose their ability to adapt to high altitude after experimental denervation of the carotid bodies. The objective of our study was to evaluate the ability of human patients to adapt to moderate altitude after single side carotid surgery. Blood gas analysis at rest at 171 m and after car and cable car transport to 1600 m before and after carotid surgery was performed. Mean(s.d.) paO2 decreased insignificantly from 74.8(3.56) at 171 m altitude to 71.6(2.07) at 1600 m (P = n.s.), means(s.d.) paCO2 decreased significantly from 36.2(2.86) to 31.4(2.7) mmHg (P < 0.05) before carotid surgery. Months after surgery, a significant drop in paO2 occurred after identical passive exposure to moderate altitude: mean(s.d.) paCO2 at 171 m 74.4(3.65) mmHg, at 1600 m 65.8(3.70) mmHg (P < 0.01), paCO2 did not change significantly. Mean(s.d.) paCO2 at 171 m: 36.0(2.35), at 1600 m 36.2(2.86) mmHg (P = n.s.). Although the sample investigated was small, after single side carotid surgery patients seem to lose their ability for satisfactory ventilatory response to acute exposure to moderate altitude. This is of possible alpine medical importance.  相似文献   
20.
Background. Extensive questioning of patients with a wide variety of skin disorders led to the impression that nocturnal overheating was probably an important factor in the initiation and the perpetuation of many skin disorders. Methods. In order to test the hypothesis, 12 “clean-skinned” subjects (6M/6F) aged 18 to 45 years were monitored electronically every 30 seconds during an 8 hour sleep period (2300 to 0700 hours), sleeping under a standard 10 tog duvet. Results. All the subjects were too hot by 3 to 4°C. All showed changes in their EEG patterns with reduced REM sleep, increased awakenings, and all showed changes in their sleep stage patterns. In addition, they all showed evidence of increased sweating in the “heat-sink” area. Conclusions. The mechanisms where by such changes could be implicated in the precipitation and perpetuation of skin disease are discussed. “Lifestyle” modification as a very effective, noninvasive, therapeutic regime is recommended. Further research along these lines would probably be very valuable and instructive.  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