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   73篇
  免费   3篇
基础医学   4篇
口腔科学   1篇
临床医学   16篇
内科学   12篇
皮肤病学   5篇
神经病学   3篇
特种医学   14篇
外科学   12篇
预防医学   2篇
药学   3篇
中国医学   2篇
肿瘤学   2篇
  2023年   1篇
  2021年   1篇
  2018年   3篇
  2017年   4篇
  2016年   4篇
  2015年   1篇
  2014年   2篇
  2013年   2篇
  2012年   8篇
  2011年   4篇
  2010年   4篇
  2009年   5篇
  2008年   4篇
  2007年   4篇
  2006年   9篇
  2005年   5篇
  2004年   3篇
  1999年   3篇
  1998年   2篇
  1997年   2篇
  1996年   1篇
  1994年   1篇
  1993年   1篇
  1985年   1篇
  1984年   1篇
排序方式: 共有76条查询结果,搜索用时 31 毫秒
1.
2.
Y chromosome deletions encompassing the AZFc region have been reported in 13% of azoospermic men and 7% of severely oligozoospermic men. We examined the impact of these Y deletions on the severity of testicular defects in 51 azoospermic men undergoing intracytoplasmic sperm injection (ICSI) after testicular sperm extraction (TESE) and 30 men with severe oligozoospermia undergoing ICSI after ejaculation of spermatozoa. In addition, five azoospermic patients shown previously to have Y chromosome deletions underwent histological evaluation of their previously obtained testis biopsy specimens. A further 27 azoospermic men underwent TESE-ICSI, but not Y chromosome DNA testing. Ten of 51 azoospermic men (20%) who underwent TESE-ICSI and Y-DNA testing were found to be deleted for portions of the Y chromosome AZFc region. Of these 10, five had spermatozoa retrievable from the testis, and in two cases the wives became pregnant. Of the 41 azoospermic men with no Y chromosome deletion, 22 (54%) had spermatozoa retrievable from the testis, and in 12 cases (29%) the wives became pregnant. Four of 30 (13%) severely oligozoospermic patients were found to be deleted for AZFc and in three (75%) of these pregnancy was achieved. The other 26 severely oligozoospermic couples who had no AZFc deletions underwent ICSI, and 12 (46%) have an ongoing or delivered pregnancy. The embryo implantation rate was not significantly different for azoospermic (22%), oligozoospermic (16%), Y-deleted (14%) or Y-intact (18%) men. Of the total of 19 infertile men who had Y chromosome deletions, 14 had deletions within Y chromosome intervals 6D-6F, in the AZFc region. Twelve of those 14 had some spermatozoa (however few in number) in the ejaculate or testis. Five of the Y-deleted men had deletions that extended more proximally on the Y chromosome, and in none of these could any spermatozoa be observed in either ejaculate or testis. These results support the concept that, in azoospermic or oligozoospermic men with Y chromosome deletions limited to intervals 6D-6F (AZFc), there are generally very small numbers of testicular or ejaculated spermatozoa. Larger Y deletions, including and extending beyond the AZFc region and encompassing more Y genes, tend to be associated with a total absence of testicular spermatozoa. In those cases where spermatozoa were retrieved, the presence of Y deletions had no obvious impact on fertilization or pregnancy rate.   相似文献   
3.
Interlocking nailing is a widely accepted and performed treatment for tibial shaft fractures. The addition of percutaneously placed transfixation screws increases the stabilisation provided by intramedullary nailing; however, the technical complexity associated with the procedure has introduced new potential complications. We report a pseudoaneurysm of the anterior tibial artery caused by a proximal interlocking screw after intramedullary nailing surgery to repair a tibial shaft fracture. The patient experienced complete relief of symptoms following removal of the nail and the screws, excision of the proximal fibula, resection of the pseudoaneurysm, and ligation of the anterior tibial artery. We recommend the oblique placement of the proximal interlocking screws to prevent this rare complication.  相似文献   
4.
The prevalence and pattern of parasitic infestation among 80 HIV/AIDS patients with diarrhea in Madurai, south India, was studied by microscopy. Eighty HIV-negative patients were used as controls. Intestinal parasites were detected in 31 HIV/AIDS patients (38.7%) and in 14 (17.5%) HIV-negative patients, a difference that was statistically significant (P < 0.05). In HIV/AIDS patients with diarrhea, protozoa accounted for the majority of diarrhea cases (Entamoeba spp. 37.5%, Cryptosporidium parvum 28.7%). It is therefore suggested that enteric infections are more common in HIV-infected patients than in HIV-negative persons in south India, and this may be due to differences in immunological profile, susceptibility as well as factors related to sanitation and the environment.  相似文献   
5.
An eight-rung, 3T degenerate birdcage coil (DBC) was constructed and evaluated for accelerated parallel excitation of the head with eight independent excitation channels. Two mode configurations were tested. In the first, each of the eight loops formed by the birdcage was individually excited, producing an excitation pattern similar to a loop coil array. In the second configuration a Butler matrix transformed this "loop coil" basis set into a basis set representing the orthogonal modes of the birdcage coil. In this case the rung currents vary sinusoidally around the coil and only four of the eight modes have significant excitation capability (the other four produce anticircularly polarized (ACP) fields). The lowest useful mode produces the familiar uniform B(1) field pattern, and the higher-order modes produce center magnitude nulls and azimuthal phase variations. The measured magnitude and phase excitation profiles of the individual modes were used to generate one-, four-, six-, and eightfold-accelerated spatially tailored RF excitations with 2D and 3D k-space excitation trajectories. Transmit accelerations of up to six-fold were possible with acceptable levels of spatial artifact. The orthogonal basis set provided by the Butler matrix was found to be advantageous when an orthogonal subset of these modes was used to mitigate B(1) transmit inhomogeneities using parallel excitation.  相似文献   
6.

Introduction

Public health initiatives to immunize children and adults have effectively reduced the number of tetanus cases in the USA. However, in the Third National Health and Nutrition Examination Survey (NHANES III), immigrants from Mexico had a 67% nonprotective anti-tetanus antibody (ATA) level. Less work has been conducted among other vulnerable populations such as human immunodeficiency virus (HIV)-infected patients. The objective of this study was to measure ATA levels among the HIV immigrant population compared with US-born HIV-infected patients.

Methods

A convenience sample of 158 HIV-infected individuals was recruited to determine the levels of ATA. A nonprotective level of ATA was defined as below 0.15 IU/ml.

Results

Among the HIV-infected patients, 72% (114/158) were born in the USA. A total of 17% (27/158) lacked protective levels of ATA. A total of 6.1% (7/114) of those born in the USA lacked protection, compared to 45% (20/44) born outside the USA (p?Conclusion The results illustrate that the country of birth is an important predictor of ATA protection, even among HIV-infected patients.  相似文献   
7.
Objective: To prospectively evaluate psychological stress reactions among residents in an emergency medicine (EM) rotation during a 4-week period.
Methods: Pre- and postrotation psychological distress levels were assessed over a 4-week EM rotation. Subjects were evaluated by several psychometric measures. These included the assessment of anxiety, depressive, and other psychological symptoms by the Brief Symptom Inventory (BSI), and the occurrence of traumatic anxiety via the Dissociative Experience Scale (DES). Also assessed were the Impact of Events Scale and the Holmes Social Readjustment Ratings Scale (Holmes), a baseline life-change measure. Demographic data were obtained. The study occurred in a university-affiliated teaching hospital ED. The 45 EM residents and 27 non-EM residents were analyzed as a group, followed by subgroup analysis comparing EM vs non-EM residents.
Results: An increase in psychological distress over the 4-week rotation was found in the non-EM group, but not in the EM group. For the non-EM residents, all 10 BSI scales worsened and 3 of 4 DES scales worsened (p = 0.002), indicative of increased psychological distress. In contrast, analysis of the 45 EM residents showed improvement in 8 of 10 BSI scales and 3 of 4 DES scales (p = 0.057).
Conclusion: A significant increase in psychologic distress was found among the non-EM residents during an EM rotation. The EM residents showed a trend for a decrease in psychological distress over the same 4-week period.  相似文献   
8.

Purpose:

To develop a simple correction approach to mitigate shading in 3 Tesla (T) breast MRI.

Materials and Methods:

A slightly modified breast receive (Rx) array, which we termed field shaping array (FSA), was shown to mitigate breast shading at 3T. In this FSA, one Rx element was selectively unblocked and tuned off the Larmor frequency during the transmit (Tx) phase. The current flowing in this element during Tx created a secondary transmit field; the vector addition of this field and the one created directly by the body coil resulted in a more uniform excitation profile over the entire breast area. The receive Rx element was returned to its intended tuning during the Rx phase, ensuring unperturbed signal reception.

Results:

Using the FSA, improved Tx field uniformity, better fat suppression, increased image homogeneity and reduced power deposition was seen in all volunteers studied.

Conclusion:

A simple modification of a standard breast Rx array, converting it to a field shaping array, was shown to mitigate breast shading in all volunteers studied. J. Magn. Reson. Imaging 2012;36:865–872. © 2012 Wiley Periodicals, Inc.  相似文献   
9.
10.
Spatially selective RF waveforms were designed and demonstrated for parallel excitation with a dedicated eight-coil transmit array on a modified 3T human MRI scanner. Measured excitation profiles of individual coils in the array were used in a low-flip-angle pulse design to achieve desired spatial target profiles with two- (2D) and three-dimensional (3D) k-space excitation with simultaneous transmission of RF on eight channels. The 2D pulse excited a high-resolution spatial pattern in-plane, while the 3D trajectory produced high-quality slice selection with a uniform in-plane excitation despite the highly nonuniform individual spatial profiles of the coil array. The multichannel parallel RF excitation was used to accelerate the 2D excitation by factors of 2-8, and experimental results were in excellent agreement with simulations based on the measured coil maps. Parallel RF transmission may become critical for robust and routine human studies at very high field strengths where B(1) inhomogeneity is commonly severe.  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