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   1869篇
  免费   113篇
  国内免费   9篇
耳鼻咽喉   12篇
儿科学   92篇
妇产科学   18篇
基础医学   203篇
口腔科学   40篇
临床医学   208篇
内科学   503篇
皮肤病学   30篇
神经病学   70篇
特种医学   253篇
外科学   142篇
综合类   64篇
预防医学   104篇
眼科学   20篇
药学   62篇
中国医学   9篇
肿瘤学   161篇
  2023年   6篇
  2022年   3篇
  2021年   16篇
  2020年   13篇
  2019年   22篇
  2018年   30篇
  2017年   17篇
  2016年   19篇
  2015年   38篇
  2014年   61篇
  2013年   77篇
  2012年   76篇
  2011年   66篇
  2010年   68篇
  2009年   94篇
  2008年   90篇
  2007年   109篇
  2006年   65篇
  2005年   63篇
  2004年   53篇
  2003年   51篇
  2002年   37篇
  2001年   27篇
  2000年   41篇
  1999年   36篇
  1998年   85篇
  1997年   55篇
  1996年   71篇
  1995年   47篇
  1994年   53篇
  1993年   47篇
  1992年   21篇
  1991年   24篇
  1990年   35篇
  1989年   46篇
  1988年   36篇
  1987年   40篇
  1986年   35篇
  1985年   25篇
  1984年   32篇
  1983年   26篇
  1982年   17篇
  1981年   24篇
  1980年   17篇
  1979年   18篇
  1978年   10篇
  1977年   19篇
  1976年   9篇
  1975年   11篇
  1973年   3篇
排序方式: 共有1991条查询结果,搜索用时 15 毫秒
11.
12.
13.
14.
Helms  CA; Kaban  LB; McNeill  C; Dodson  T 《Radiology》1989,172(3):817-820
Magnetic resonance (MR) imaging has been used in the temporomandibular joint (TMJ) primarily to define the disk position. This report examines altered morphology and signal intensity characteristics of the TMJ disk as they relate to the severity of internal derangement. Two hundred sixteen joints in 133 patients with a history of such derangement. were imaged with MR. Disk position, signal intensity, morphology, and the presence of osteoarthritis were determined for each joint. The normal disk was not anteriorly displaced and had a normal "bow-tie" shape. A grade 1 disk was anteriorly displaced and had a normal shape; a grade 2 disk was anteriorly displaced and had an abnormal shape. Forty (19%) joints were considered normal; none of these exhibited osteoarthritis. One hundred thirty-nine (64%) joints were grade 1; osteoarthritis was found in 17%. Thirty-seven (17%) were grade 2; osteoarthritis was found in 95%. All forty normal joints had high or intermediate signal intensity in the disk. Osteoarthritic joints had a higher percentage of disks with diminished intensity (P less than .0001). Severe or untreated osteoarthritis is known to be a complication of TMJ internal derangements; hence this grading system seems to correlate with the severity of internal derangement.  相似文献   
15.
16.
A study of the degree of progesterone support required for the maintenance of various stages of pregnancy was undertaken in mice. Mated females were ovariectomized at various stages of pregnancy and progesterone and oestradiol support provided by s.c. Silastic implants with known release characteristics. In the earliest stages of pregnancy (days 1-5), very low concentrations of progesterone (<25% of normal physiological values) were sufficient to maintain pre-implantation stages and allow implantation. In the immediate post-implantation period (days 5-9), the development of implantation sites and decidualization required considerably higher progesterone support. In mid-pregnancy (days 11-14), progesterone alone could not maintain pregnancy unless present in very high amounts; however, the presence of oestradiol during this period lowered the progesterone requirements to well within the physiological range. This effect of oestradiol started on day 11 but required the level of oestradiol support to be kept within strictly defined limits, with high concentrations inducing abortion. Progesterone alone was able to maintain pregnancy from day 15. These results indicate that the minimal progesterone support required for pregnancy in mice varies considerably at different stages of pregnancy and is at least partly modulated by oestradiol.   相似文献   
17.
In order to obtain heparin-binding polyurethanes, tertiary amino-groups have been introduced in the polymer backbone by attributing a key-role to the chain extender, i.e. substituting butanediol, commonly used in polyurethane synthesis, with a tailor-made diamino-diamide-diol. In this work a poly(ether-urethane-aminoamide) (PEU/PIME/al) was obtained with poly(oxytetramethylene) glycol 2000, 1,6-hexamethylene-diisocyanate and the new chain extender, in the molar ratio 1:2:1. The heparin binding capacity of PEU/PIME/al was evaluated with 125I labelled heparin, using for comparison the analogous polymer obtained with a diamide-diol (i.e. the poly(ether-urethane-amide) PEU/PIBLO/al), and two commercially available biomedical polyurethanes (Pellethane 2363 and Corethane). pH and ionic strength dependence of the heparin uptake were investigated by treating all the polyurethanes with solutions of 125I heparin into buffers from pH 4 to 9 or NaCl molarity from 0.0 to 1.0. The stability of the interaction with bound heparin was investigated by sequential washing treatments (PBS, 1 N NaOH, 2% SDS solution), then analysing the residual radioactivity on the materials. Results indicated that the heparin binding of PEU/PIME/al is significantly higher and more stable than that of the other polyurethanes, with a time-dependent kinetic. The interaction with heparin appears to be prevalently ionic, with the contribution of other electrostatic and hydrophobic interactions. Activated partial thromboplastin time (APTT), performed on human plasma with polyurethane-coated, heparinized test tubes, indicated that bound heparin maintains its biological activity after the adsorption.  相似文献   
18.
19.
Supravalvular aortic stenosis (SVAS) is an inherited obstructive vascular disease that affects the aorta, carotid, coronary and pulmonary arteries. Previous molecular genetic data have led to the hypothesis that SVAS results from mutations in the elastin gene, ELN. In these studies, the disease phenotype was linked to gross DNA rearrangements (35 and 85 kb deletions and a translocation) in three SVAS families. However, gross rearrangements of ELN have not been identified in most cases of autosomal dominant SVAS. To define the spectrum of ELN mutations responsible for this disorder, we refined the genomic structure of human ELN and used this information in mutational analyses. ELN point mutations co-segregate with the disease in four familial cases and are associated with SVAS in three sporadic cases. Two of the mutations are nonsense, one is a single base pair deletion and four are splice site mutations. In one sporadic case, the mutation arose de novo. These data demonstrate that point mutations of ELN cause autosomal dominant SVAS.   相似文献   
20.

Background  

We present our experience of therapeutic vaccination using dendritic cells (DC) pulsed with autologous tumor antigens in patients with advanced melanoma.  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