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   3892篇
  免费   450篇
  国内免费   76篇
耳鼻咽喉   16篇
儿科学   52篇
妇产科学   62篇
基础医学   241篇
口腔科学   48篇
临床医学   638篇
内科学   711篇
皮肤病学   66篇
神经病学   248篇
特种医学   179篇
外国民族医学   1篇
外科学   712篇
综合类   334篇
现状与发展   1篇
预防医学   379篇
眼科学   26篇
药学   473篇
  6篇
中国医学   67篇
肿瘤学   158篇
  2024年   5篇
  2023年   85篇
  2022年   159篇
  2021年   195篇
  2020年   203篇
  2019年   209篇
  2018年   188篇
  2017年   198篇
  2016年   147篇
  2015年   201篇
  2014年   267篇
  2013年   394篇
  2012年   236篇
  2011年   215篇
  2010年   187篇
  2009年   171篇
  2008年   136篇
  2007年   103篇
  2006年   95篇
  2005年   113篇
  2004年   89篇
  2003年   104篇
  2002年   85篇
  2001年   83篇
  2000年   83篇
  1999年   56篇
  1998年   52篇
  1997年   46篇
  1996年   46篇
  1995年   24篇
  1994年   35篇
  1993年   27篇
  1992年   30篇
  1991年   19篇
  1990年   30篇
  1989年   15篇
  1988年   16篇
  1987年   3篇
  1986年   16篇
  1985年   13篇
  1984年   9篇
  1983年   9篇
  1982年   7篇
  1981年   5篇
  1980年   6篇
  1979年   2篇
  1976年   1篇
排序方式: 共有4418条查询结果,搜索用时 32 毫秒
31.
Dual labelling methods were applied to localize simultaneously neuropeptide Y (NPY) and glutamate decarboxylase (GAD) immunoreactivities on ultrathin sections of the rat caudate-putamen (CP). By means of a double peroxidase-anti-peroxidase technique, using 3,3'-diaminobenzidine and benzidine dihydrochloride as chromogens in animals with no colchicine pretreatment, GAD immunoreactivity was found to be present in terminals only whereas NPY immunoreactivity was detected in neurons displaying the features of aspiny type cells and processes. With this approach, we observed numerous synaptic associations of the symmetrical type between GAD-immunoreactive (-Ir) axonal boutons and NPY-Ir cell bodies and dendrites. By combining immunoperoxidase and radioimmunocytochemical labelling in animals pretreated with colchicine, NPY was again detected in a single population of aspiny type neurons whereas GAD immunoreactivity was observed in neurons which could be classified as aspiny and spiny on the basis of their ultrastructural characteristics. All the cells of the aspiny type displaying clear-cut NPY immunoreactivity were also found to be GAD-positive. Some other neurons of both the aspiny and the spiny type were found to be immunoreactive to GAD alone. GAD/NPY dually labelled terminals were also observed and some axo-axonic appositions between GAD- and NPY-Ir terminals were also detected. All in all, these data show that NPY aspiny type neurons of the rat CP receive GABAergic afferents and provide morphological support for two hypotheses: that NPY is co-localized with GABA in some cell bodies, dendrites and axons, and that presynaptic interactions may occur between NPY and GABAergic neuronal systems.  相似文献   
32.
Dual chamber pacing (DDD) maintains atrioventricular (AV) sequence; AV delay programmability modifies the relationship between atrial and ventricular contraction. To evaluate the hemodynamic effects of such a modification, ten patients with a DDD unit for complete AV block were studied by time-motion (M-mode) and Doppler echocardiography during inhibited ventricular pacing (VVI), atrial-triggered ventricular pacing (VDD) and atrioventricular sequential pacing (DVI) at different AV delay (90, 140, 190, 240 msec). A significant improvement in stroke volume (SV) (15%-20%, P less than 0.05) was seen during DDD versus VVI pacing; no changes, however, were observed in the same patient with different AV delay or during DVI versus VDD pacing. These data suggest that programming of AV delay does not affect systolic performance at rest; longer diastolic filling times recorded during DDD pacing with "short" AV delay (90-140 msec) do not seem to be a hemodynamically relevant epi-phenomenon of PM programming.  相似文献   
33.
目的 探讨螺旋CT双期扫描对肝脏占位性病变的诊断价值。方法 对98例肝内占位性病变的病人进行螺旋CT双期增强扫描。结果 98例病人中肝癌48例,肝转移瘤19例,肝血管瘤31例。结论 螺旋CT扫描速度快,在动脉期和门静脉期分别完成全肝扫描,弥补了一般动态扫描的缺点,对肝内病灶的检出和定性有重要价值。  相似文献   
34.
We studied the characteristics of bone mineral density (BMD) and soft tissue composition in obese Japanese women using dual-energy X-ray absorptiometry. Eighty-nine women, aged 45–85 years, were divided into three groups according to their body mass index (BMI): a thin group (n = 38; BMI < 21), a standard weight group (n = 31; BMI, 21–25), and an obese group (n = 20; BMI ≥ 25). The mean BMD of the second to fourth lumbar vertebrae and BMD of the lumbar spine, thoracic spine, pelvis, legs, and ribs of the thin group were significantly lower than those of the standard weight group or the obese group (P < 0.05), whereas no significant difference in total body BMD was observed among the three groups. There was a significant difference in total and regional fat mass among the three groups (P < 0.05). Lean mass of legs and total lean mass showed a significant difference between the thin group and the obese group (P < 0.05). The results showed that obesity was associated with higher BMD of weight bearing-bones and ribs, high total and regional fat mass, and high lean mass of bilateral legs and total lean mass. We suggest that obesity may contribute to the prevention of bone loss of weight-bearing bones and ribs and muscular atrophy of the legs. Received: Sept. 30, 1998 / Accepted: Dec. 10, 1998  相似文献   
35.
Adachi S  Takeda T  Fukao K 《Surgery today》1999,29(4):301-306
Conducting the qualitative evaluation of reconstruction methods is difficult because of their complexity. The aim of the present study was to compare esophageal bile and food reflux by performing gastrointestinal and hepatobiliary dual scintigraphy (GHDS) after various methods of reconstruction following total gastrectomy. Of 17 patients studied, 4 had undergone Roux-en-Y anastomoses (R-Y); 6, jejunal pouch-Y anastomoses (P-Y); and 7, jejunal pouch interposition (P-I). GHDS was performed 1 year after surgery using111In-diethylene triamine pentaacetic acid administered orally, and99mTc-pyridoxyl-5-methyl tryptophan administered intravenously. Imaging data from a gamma camera were stored in and processed by a data analyzer. Three patients who had undergone R-Y and one who had undergone P-I complained of heartburn, while one who had undergone R-Y, two who had undergone P-Y, and three who had undergone P-I complained of a feeling of fullness. Esophageal bile reflux was confirmed by GHDS in four of the patients who had undergone R-Y, one who had undergone P-Y, and four who had undergone P-I. Moreover, GHDS demonstrated food retention in two patients who had undergone R-Y, five who had undergone P-Y, and four who had undergone P-I. Weight loss was closely related to the esophageal reflux of bile or food which can be accurately detected by GHDS. Despite the absence of heartburn, patients diagnosed as having bile reflux by GHDS showed poor recovery of body weight.  相似文献   
36.
陈军  陈燕华  刁雨辉  李俐 《中国药房》2003,14(6):362-363
目的 :用双波长分光光度法测定复方间苯二酚洗剂中间苯二酚的含量。方法 :以水为溶剂 ,在273 5nm和266 1nm波长处测定吸收度并计算差值。结果 :间苯二酚在20 32~60 96μg/ml浓度范围内线性关系良好 (r=0 9998) ;平均回收率为99 59 % ,RSD=0 45% (n=9)。结论 :本方法简便、快捷 ,测定结果准确  相似文献   
37.
Transarterial left ventricular assist devices (LVADs), such as the Hemopump, IABP, and PUCA-pump, are meant to be introduced into the body via the femoral or axillary artery without major surgery. For certain applications, introduction is performed directly into the aorta via an open thorax procedure. A prototype of a vascular access device has been realized that allows direct access into the aorta as an alternative for the common surgical graft anastomosis suturing technique. The device consists of a metal tube acting as a circular knife to cut a hole in the aortic wall, a screw to store the removed part of the aortic wall, and a plastic tube that is introduced through the hole and tightly connected to the aortic wall. The device could be placed without aortic clamping. The device has been tested on a slaughterhouse porcine aorta. A low-pressurized aorta appeared to be the worst case; thus, two animal experiments in the low-pressurized pulmonary artery were performed. No leakage occurred for pressures between 40 and 300 mm Hg.  相似文献   
38.
The ubiquity of human cytomegalovirus (CMV) and human herpesvirus-7 (HHV-7), as well as activation of these viruses during immunosuppression, allows the suggestion that both viruses could participate in the development of 'CMV disease' in patients after renal transplantation (RT). The aim of our research was to study the prevalence of latent CMV and HHV-7 infections in patients before RT, to determine interaction between these viruses in dual infection and possible association of their reactivation with the progression of 'CMV disease' after RT. Peripheral blood samples were collected from 49 patients before and up to 10-12 wk after RT. The methods used for diagnostics of viral infections were: serology, nested polymerase chain reaction (nPCR) analysis of peripheral blood leukocytes (PBL) and plasma, and virus isolation in cell cultures (morphological changes, nPCR analysis of cellular and cell-free samples, indirect immunofluorescence analysis). Before RT, CMV and HHV-7 DNAs were detected in PBL but not in the plasma samples, which indicates the presence of latent viral infection in patients. Latent dual (CMV + HHV-7) infection was prevalent (51.0%) in 49 patients, while CMV and HHV-7 infections alone were detected in 26.5 and 12.2% of patients, respectively. Risk of viral disease after RT, for recipients with latent dual infection before RT, was 12- and 2.2-fold higher in comparison with CMV and HHV-7 infections alone, respectively. Frequency of dual infection in 18 recipients with 'viral syndrome' or 'CMV disease' after RT was reliably higher (13/18, 81.3%) than CMV (1/18, 6.2%) (p < 0.025) and HHV-7 (2/18, 12.5%) (p < 0.025) infections alone. HHV-7 reactivation preceded CMV reactivation in 77.0% of the cases of dual infection in the recipients with viral disease and reactivation of both viruses preceded the development of viral disease. Severe 'CMV disease' developed in 2 out of 2 recipients with CMV primary infection and 'viral syndrome' in 1 recipient with CMV reinfection. The reactivation of CMV was detected in all recipients prior to onset of the disease. Correlation was shown between reactivation of latent HHV-7 infection and development of febrile syndrome in 2 out of 2 recipients with HHV-7 infection alone. Taking into account that dual infection is an increased risk factor for 'viral syndrome' and 'CMV disease' development, screening diagnostic should include testing for both viral infections in transplant donors as well as in recipients before and after RT.  相似文献   
39.
The aim of this study was to evaluate the improvement in patient comfort and field positional accuracy provided by a new pelvic stabilization system when delivering multiple field radiotherapy to the pelvis. The Pelvic Cradle (BEHTS Manufacturing, Brisbane, Qld, Australia) is a stabilization device that provides reproducible patient positioning and levelling. Ninety patients were randomized into three groups. The first group was treated using the Pelvic Cradle, the second group was treated using current stabilization practices, and the third group was treated using the Pron Pillo (Chattanooga Pharmacal Company, USA) and current stabilization practices. Port films were assessed for field displacement in the lateral and cranio-caudal directions. A patient survey was used to evaluate the patient's perception of comfort while receiving treatment. When compared to the control group, the pelvic cradle group demonstrated a 48% improvement in the mean lateral deviation from 3.8 mm to 2.0 mm (P < 0.001) and a 36% improvement in the mean cranio-caudal deviation from3.9 mm to 2.5 mm (P < 0.001). The Pelvic Cradle was found to provide an improved level of field positional accuracy while maintaining patient comfort.  相似文献   
40.
王颖  石晓研 《医疗设备信息》2005,20(7):19-19,84
本文介绍在域中如何实现系统远程控制,具体说明了如何配置Pcanywhere、域中实现远程安装、以及能够实现的一些功能。  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