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   1820篇
  免费   83篇
  国内免费   33篇
耳鼻咽喉   28篇
儿科学   70篇
妇产科学   26篇
基础医学   185篇
口腔科学   35篇
临床医学   159篇
内科学   540篇
皮肤病学   119篇
神经病学   118篇
特种医学   211篇
外科学   176篇
综合类   33篇
预防医学   107篇
眼科学   7篇
药学   62篇
中国医学   4篇
肿瘤学   56篇
  2021年   20篇
  2020年   9篇
  2019年   30篇
  2018年   24篇
  2017年   17篇
  2016年   21篇
  2015年   33篇
  2014年   38篇
  2013年   82篇
  2012年   43篇
  2011年   41篇
  2010年   74篇
  2009年   76篇
  2008年   51篇
  2007年   52篇
  2006年   52篇
  2005年   53篇
  2004年   37篇
  2003年   37篇
  2002年   38篇
  2001年   37篇
  2000年   27篇
  1999年   34篇
  1998年   89篇
  1997年   80篇
  1996年   81篇
  1995年   52篇
  1994年   63篇
  1993年   52篇
  1992年   23篇
  1991年   26篇
  1990年   32篇
  1989年   48篇
  1988年   49篇
  1987年   40篇
  1986年   37篇
  1985年   29篇
  1984年   25篇
  1983年   13篇
  1982年   22篇
  1981年   19篇
  1980年   15篇
  1979年   17篇
  1978年   16篇
  1977年   18篇
  1976年   17篇
  1975年   12篇
  1974年   10篇
  1973年   16篇
  1972年   10篇
排序方式: 共有1936条查询结果,搜索用时 15 毫秒
81.
Objective.?The aim of the study was to investigate the impact of the climacterium (before and after menopause) on platelet activation.

Background.?Platelet activation has been associated to the risk of cardiovascular disease. There is much speculation about the relationship between platelet function and sex steroids, due to peculiarities of platelet action between the genders, including concerns about the influence of low estradiol status in menopausal women.

Methods.?By means of a cross-sectional study design, 37 female patients divided into two groups were compared. Group A consisted of ten women, mean age 43.9 years, in the premenopausal period, with normal estrogen levels; and Group B comprised 27 patients, mean age 53.0 years, who had all reached menopause. Platelet activation markers, namely P-selectin and glycoprotein IIb–IIIa complex (GPIIb–IIIa), were evaluated by flow cytometry with monoclonal antibodies. A binding index was calculated for both parameters (percentage of positive platelets?×?mean fluorescence of positive platelets). Also, thromboxane A2 was quantified by means of its main plasma metabolite, thromboxane B2, by enzyme immunoassay.

Results.?P-selectin and GPIIb–IIIa expression results revealed lower platelet activation status after menopause, as there was a decrease in both the percentage of P-selectin?+? platelets and of GPIIb–IIIa mean fluorescence of positive platelets, lowering both binding indices. P-selectin binding index differed significantly between Group A (12.3?±?3, n?=?10) and Group B (6.2?±?2.9, n?=?27; mean?±?standard deviation (SD), p?<?0.001). GPIIb–IIIa binding index also differed significantly between both groups (Group A: 18.8?±?2.3, n?=?10 vs. Group B: 16.2?±?3.1, n?=?27; mean?±?SD, p?<?0.0018). Plasma concentration of thromboxane B2 was 1.07?±?0.5?pg/well before menopause (Group A, n?=?10) and 1.9?±?4.1?pg/well after menopause (Group B, n?=?27), not significantly different (mean?±?SD, baseline?×?therapy, p?=?0.85).

Conclusions.?After the menopause, climacteric women – whose estradiol status is low – have a decreased activation platelet status compared with premenopausal women. Nevertheless, further studies on a larger sample are necessary for conclusive data regarding cardiovascular disease.  相似文献   
82.
Objective: To determine whether inflammatory bowel disease (IBD) is associated with increased risk for adverse perinatal outcome.

Methods: A case–control study of 116 singleton pregnancies with IBD compared to 56?398 singleton controls delivered between 1986 and 2001.

Results: Patients with IBD were slightly older (32.8 vs. 30.6 years, p <?0.001), more likely to be Caucasian or Asian than Black or Latino (92% vs. 57%, p <?0.001) and have private health insurance (33% vs. 3%, p <?0.001). IBD was associated with an increased risk for labor induction (32% vs. 24%, p?=?0.002), chorioamnionitis (7% vs. 3%, p?=?0.04) and Cesarean section (32% vs. 22%, p?=?0.007), but there were no differences in neonatal outcomes. Subgroup analysis demonstrated an increased risk for low birth weight (LBW) in the ulcerative colitis group vs. the Crohn's disease group (19% vs. 0%, p?=?0.002). Patients with prior surgery for IBD had a lower incidence of LBW (0% vs. 12%, p?=?0.03). Flares during pregnancy were associated with an increased risk for preterm delivery (27% vs. 8%, p?=?0.02) and LBW (32% vs. 3%, p?=?0.003).

Conclusion: IBD was an independent risk factor for Cesarean section but there was no increase in adverse perinatal outcome. Crohn's disease, prior IBD surgery and quiescent disease were associated with a lower risk for LBW.  相似文献   
83.
84.
This study reviews the demographic, radiologic, and histologic characteristics of 13 cases of an important primary skeletal neoplasm, giant cell tumor of bone, occurring in an uncommon location, the scapula. that eight of 13 patients presented prior to 20 years of age contrasts significantly with the typical age distribution (between 20–40 years) encountered in giant cell tumors arising in long bones. As it does elsewhere in the skeleton, giant cell tumor of the scapula frequently demonstrates cystic and/or telangiectatic components on histologic examination. The radiologic appearances of giant cell tumor in the scapula and in more typical locations are similar and include: (1) well-defined (geographic) margins, occasionally with a delicate sclerotic rim, (2) prominent trabeculations, (3) expanded bone contour, (4) frequent extension to the subchondral plate, and (5) absence of internal mineralization. Tumor sites within the scapula included: coracoid process, acromion, and body (three cases each); glenoid (two cases); and superior and inferior angles (one case each).The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army, the Department of Defense, or the Uniformed Services University of the Health Sciences.  相似文献   
85.
A prospective evaluation of color flow mapping and real-time ultrasound was performed to determine if pseudoaneurysms could be distinguished from other causes of masses surrounding vascular grafts of the lower extremities. Twelve palpable pulsatile masses were imaged. Diagnoses were confirmed at angiography (n = 11), computed tomography (n = 7), aspiration biopsy (n = 5), and operative intervention (n = 6). A swirling pattern of blood flow was seen in six of seven cases of pseudoaneurysm. Lack of flow signals was noted in four of the five collections representing hematoma (n = 2) or infection (n = 2). The seventh case was later shown to be an infected, thrombosed pseudoaneurysm. The single false-positive diagnosis was made early in the series when the flow signals detected were due to transmitted arterial pulsations. The authors conclude that color Doppler flow imaging is useful in the differential diagnosis of pulsatile masses associated with prosthetic grafts. Prosthetic graft pseudoaneurysms have a specific appearance of swirling blood flow arising from a wide neck and are distinguishable from traumatic or iatrogenic pseudoaneurysms of the native vascular tree.  相似文献   
86.
Sequelae of acute renal infections: CT evaluation   总被引:1,自引:0,他引:1  
Soulen  MC; Fishman  EK; Goldman  SM 《Radiology》1989,173(2):423-426
Seventeen patients with upper urinary tract infection who underwent 51 computed tomographic studies (two to five per patient; mean, three) were retrospectively evaluated. Five to 10 days after the initial examination, there was little change in parenchymal abnormalities, but perirenal inflammation worsened and then subsided over 2-8 weeks. Enlargement of the affected kidney, present initially in 12 patients, persisted up to 6 weeks and resolved by 10-16 weeks. Abnormalities of parenchymal contrast material enhancement persisted for 1-2 months. New cortical scars appeared in six of 12 patients with an initially normal renal contour and in one of five patients who had scars initially. Three patients with a renal abscess developed a new calyceal diverticulum, presumably by rupture of the abscess into the collecting system. The present study shows that abnormalities of renal size and enhancement persist for weeks to months after clinical signs of infection resolve and that scarring in adults with urinary tract infection occurs more frequently than was previously realized.  相似文献   
87.
88.
Allan C. Harrington  MD    Jason M. Cheyney  MPAS  PA-C  LT  BSC  USAF    Tina Kinsley-Scott  MD  CAPT  MSC  USAF    Robert J. Willard  MD  MAJ  MC  USA 《Dermatologic surgery》2004,30(7):1065-1067
Background. Surgery of the digit is facilitated with adequate hemostasis for visualization of the operative field. Several types of tourniquets have been used for this purpose, including glove fingers, Penrose drains, Marmed digital tourniquets, and standard pneumatic tourniquets.
Objective. To present a novel method to achieve hemostasis during surgery of the digit.
Materials. A slightly oversized sterile glove, a hemostat, and a pair of scissors.
Conclusion. We present a novel method to achieve hemostasis using a sterile glove and a hemostat, that allows the surgeon to methodically titrate the amount of compression necessary to attain a bloodless field while minimizing the risks of excessive pressures.
Surgery of the digit is facilitated with adequate hemostasis for visualization of the operative field. Several types of tourniquets have been used for this purpose, including glove fingers, Penrose drains, Marmed digital tourniquets, and standard pneumatic tourniquets. We present a novel method to achieve hemostasis using a sterile glove and a hemostat that allows the surgeon to methodically titrate the amount of compression necessary to attain a bloodless field while minimizing the risks of excessive pressures.  相似文献   
89.
90.
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