全文获取类型
收费全文 | 1300篇 |
免费 | 72篇 |
国内免费 | 56篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 69篇 |
妇产科学 | 9篇 |
基础医学 | 138篇 |
口腔科学 | 23篇 |
临床医学 | 181篇 |
内科学 | 296篇 |
皮肤病学 | 51篇 |
神经病学 | 70篇 |
特种医学 | 301篇 |
外科学 | 73篇 |
综合类 | 26篇 |
预防医学 | 62篇 |
眼科学 | 8篇 |
药学 | 61篇 |
中国医学 | 2篇 |
肿瘤学 | 57篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 14篇 |
2020年 | 10篇 |
2019年 | 11篇 |
2018年 | 21篇 |
2017年 | 5篇 |
2016年 | 8篇 |
2015年 | 15篇 |
2014年 | 15篇 |
2013年 | 48篇 |
2012年 | 29篇 |
2011年 | 29篇 |
2010年 | 37篇 |
2009年 | 62篇 |
2008年 | 24篇 |
2007年 | 62篇 |
2006年 | 33篇 |
2005年 | 30篇 |
2004年 | 22篇 |
2003年 | 21篇 |
2002年 | 22篇 |
2001年 | 19篇 |
2000年 | 24篇 |
1999年 | 28篇 |
1998年 | 71篇 |
1997年 | 83篇 |
1996年 | 102篇 |
1995年 | 63篇 |
1994年 | 60篇 |
1993年 | 54篇 |
1992年 | 18篇 |
1991年 | 16篇 |
1990年 | 23篇 |
1989年 | 42篇 |
1988年 | 38篇 |
1987年 | 36篇 |
1986年 | 46篇 |
1985年 | 43篇 |
1984年 | 8篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1975年 | 15篇 |
1967年 | 2篇 |
排序方式: 共有1428条查询结果,搜索用时 15 毫秒
991.
The potential for improved pulmonary nodule detection with scanning equalization radiography (SER) was evaluated by means of observer performance testing during the interpretation of posteroanterior conventional radiographs and SER images of an anthropomorphic chest phantom with simulated nodules. A test set of 200 conventional and 200 SER radiographs of phantoms containing either one nodule or none was interpreted by four radiologists attempting to detect a nodule and indicate a confidence value. Their ability to detect nodules positioned over the lung was slightly improved with SER compared with conventional radiography (sensitivity, .56 vs .70); for nodules over the mediastinum or diaphragmatic areas, it was much improved (sensitivity, .29 vs .64). The results were also analyzed with receiver-operating characteristic methods, which revealed a significant improvement in lesion detect-ability over the thicker body parts with SER images. The capability of equalized chest radiographs to provide improved lesion detectability suggests that SER may set a new standard for film-based chest radiography and have a large clinical application. 相似文献
992.
Fetal hyaloid artery: timing of regression with US 总被引:2,自引:0,他引:2
Large-aperture, dynamically focused ultrasonic imaging permits noninvasive, anatomic study of the eye at the millimeter level in the second and third trimesters of pregnancy. The authors report their observations of the hyaloid artery in 210 of 219 fetuses examined with this technique. This vessel is seen in fetuses of 20 weeks gestational age or less and regresses spontaneously at the start of the third trimester. The 210 subjects included 100 who were examined at gestational ages of 16-32 weeks or more and 85 healthy fetuses and 25 with pathologic findings at birth who were examined at 34 weeks gestational age to term. The presence of the hyaloid artery in the mid third trimester was uncommon in healthy subjects (less than 1%) and was not seen in any beyond 29.9 weeks gestational age. However, in nine of the 25 fetuses with abnormalities (five with trisomy syndromes), the vessel was seen at 30.8-36.8 weeks gestational age. The temporarily delayed regression of the hyaloid artery may occur with trisomy 21 syndrome and other forms of retarded brain development. 相似文献
993.
994.
Allan I. Levey Sharon M. Edmunds Steven M. Hersch Ronald G. Wiley Craig J. Heilman 《The Journal of comparative neurology》1995,351(3):339-356
The m2 muscarinic acetylcholine receptor gene is expressed at high levels in basal forbrain, but the paucity of information about localization of the encoded receptor protein has limited the understanding of cellular and subcellular mechanisms involved in cholinergic actions in this region. The present study sought to determine the cellular localization of m2 protein, its relationship to cholinergic neurons, and its pre-and postsynaptic distribution in the rat medial septum-diagonal band complex using immunocytochemistry with polyclonal rabbit antibodies and a newly developed rat monoclonal antibody specific to the m2 receptor. Light microscopic colocalization studies demonstrated that m2 was present in a subset of choline acetyltransferase immunoreactive neurons, in choline acetyltransferase-negative neurons, and in more neuropil elements than was choline acetyltransferase. Intraventricular injections of 192 IgG-saporin, an immunotoxin directed to the low-affinity nerve growth factor receptor, resulted in depletion of choline acetyltransferase-immunoreactive neurons in the medial septum-diagonal band complex, whereas m2 immunoreactivity in neurons and in the neuropil was unchanged. By electron microscopy, m2 receptor in medial septum-diagonal band complex was localized to the plasmalemma of a small population of small to medium-sized neurons, and it was also found in dendrites, axons, and axon terminals in the neuorpil Neurons expressing m2 immunoreactivity recived synaptic contacts from unlabelled axon terminals. A small distinct subpopulation of large neurons, unlabelled by m2 immunoreactivity, received synaptic contacts from m2-immunoreactive terminals. Thus, m2 receptor is situated to mediate the local effects of acetylcholine on basal forebrain cholinergic and noncholinergic neurons and, also, at both pre-and postsynaptic sites. © 1995 Willy-Liss, Inc. 相似文献
995.
996.
997.
Hairy cells (HCs) and some activated B cells express high levels of macrophage colony-stimulating factor (M-CSF) (CSF-1) receptor, but the functional effects of the cytokine on B cells have not been previously identified. Using video microscopy, image analysis, and migration assays, M-CSF was shown to induce chemokinetic and chemotactic movement of HCs. This movement response involved transition to a highly mobile, rounded cell form and was accompanied by distinctive changes in F-actin polymerization and distribution. Furthermore, the M-CSF-induced motility was substantially modified by the adhesive protein used as a substratum and involved qualitative changes in the function of the alpha v beta 3 integrin of HCs. It is suggested that the findings are relevant to the pathophysiology of hairy-cell leukemia (HCL) in particular, and to the biology of B-cell migration in general. 相似文献
998.
Modulation of spontaneous B-cell differentiation in macroglobulinemia by retinoic acid 总被引:2,自引:0,他引:2
We previously showed that clonal blood B cells from patients with macroglobulinemia spontaneously differentiate in vitro to plasma cells. This process is dependent on an interleukin (IL)-6 autocrine pathway. We investigate here whether all-trans-retinoic acid (RA) interferes with B-cell differentiation either in patients with IgM gammapathy of undetermined significance (MGUS) or Waldenstrom's macroglobulinemia (WM). RA at a concentration of 10(-5) to 10(-8) mol/L inhibited by 50% to 80% the in vitro differentiation of purified B cells from four of five patients with MGUS and from one of five patients with WM as assessed by the IgM content of day 7 culture supernatants. We next determined whether this effect could be related to an inhibition of IL- 6 secretion by cultured B cells and/or a downregulation of the IL-6 receptor (IL-6R), which was constitutively expressed on patients' blood B cells. A 50% to 100% (mean, 80%) inhibition of IL-6 production was found in seven of 10 patients (five with MGUS and two with WM). The IL- 6R was no more detectable on cells from patients with MGUS after 2 days of treatment with RA and slightly downregulated in patients with WM. It was of interest that B cells susceptible to the action of RA belonged mostly to patients with IgM MGUS, which reinforces our previous data showing distinct requirements for IL-6-dependent differentiation of blood B cells from patients with VM or IgM MGUS. 相似文献
999.
1000.