全文获取类型
收费全文 | 2388篇 |
免费 | 175篇 |
国内免费 | 8篇 |
专业分类
耳鼻咽喉 | 6篇 |
儿科学 | 104篇 |
妇产科学 | 40篇 |
基础医学 | 294篇 |
口腔科学 | 39篇 |
临床医学 | 211篇 |
内科学 | 536篇 |
皮肤病学 | 18篇 |
神经病学 | 274篇 |
特种医学 | 168篇 |
外科学 | 305篇 |
综合类 | 35篇 |
预防医学 | 286篇 |
眼科学 | 12篇 |
药学 | 131篇 |
中国医学 | 2篇 |
肿瘤学 | 110篇 |
出版年
2021年 | 25篇 |
2020年 | 12篇 |
2019年 | 13篇 |
2018年 | 29篇 |
2017年 | 33篇 |
2016年 | 24篇 |
2015年 | 35篇 |
2014年 | 40篇 |
2013年 | 69篇 |
2012年 | 70篇 |
2011年 | 90篇 |
2010年 | 51篇 |
2009年 | 59篇 |
2008年 | 79篇 |
2007年 | 83篇 |
2006年 | 83篇 |
2005年 | 104篇 |
2004年 | 86篇 |
2003年 | 80篇 |
2002年 | 77篇 |
2001年 | 84篇 |
2000年 | 59篇 |
1999年 | 72篇 |
1998年 | 58篇 |
1997年 | 78篇 |
1996年 | 61篇 |
1995年 | 51篇 |
1994年 | 46篇 |
1993年 | 33篇 |
1992年 | 58篇 |
1991年 | 62篇 |
1990年 | 45篇 |
1989年 | 47篇 |
1988年 | 58篇 |
1987年 | 46篇 |
1986年 | 51篇 |
1985年 | 64篇 |
1984年 | 50篇 |
1983年 | 46篇 |
1982年 | 35篇 |
1981年 | 27篇 |
1980年 | 25篇 |
1979年 | 33篇 |
1978年 | 29篇 |
1977年 | 23篇 |
1976年 | 23篇 |
1975年 | 20篇 |
1974年 | 28篇 |
1971年 | 12篇 |
1969年 | 17篇 |
排序方式: 共有2571条查询结果,搜索用时 31 毫秒
1.
Intracranial circulation: pulse-sequence considerations in three- dimensional (volume) MR angiography 总被引:2,自引:0,他引:2
The technique and feasibility of magnetic resonance (MR) angiography of intracranial vessels were studied in 35 healthy volunteers. Variations in image orientation, repetition time (TR), and flip angle were evaluated to determine their effects on flow-related enhancement. Gradient modifications--including echo time (TE), motion compensation, bandwidth, and field of view--were also studied in an effort to reduce motion-induced phase shifts. Results indicated that a FISP (fast imaging with steady precession) sequence with a TR of 50 msec, TE of 15 msec, velocity compensation in the read and section-select directions, acceleration compensation in the read direction, anisotropic volume, and a 1.25-mm partition thickness produced three-dimensional angiographic MR images that were accurate and reproducible in the depiction of the major intracranial vessels. Difficulties with field of view, persistent signal void secondary to higher-order motion, and spatial resolution remain major problems requiring additional study. 相似文献
2.
U. Meyding-Lamadé K. Rieke D. Krieger W. Hacke Michael Forsting Klaus Sartor Christian Sommer 《Journal of neurology》1995,242(5):335-343
Acute ischaemia of the vertebrobasilar circulation leads to a variety of clinical manifestation and is mostly due to cardiogenic or artery-to-artery embolism. We describe four neurological emergency situations involving vertebrobasilar artery aclusion of other origins: basilar migraine, extrinsic compression by rheumatoid inflammatory tissue, generalized vasculitis in subacute rheumatic fever and basilar artery dissection. The differential diagnosis of acute vertebrobasilar artery occlusion may have an important impact on patient management. 相似文献
3.
AIDS, policy analysis, and the electorate: the role of schools of public health. 总被引:2,自引:2,他引:0 下载免费PDF全文
Current debates concerning appropriate policy to combat the epidemic of acquired immunodeficiency syndrome (AIDS) have raised critical questions regarding the role that schools of public health and individual public health professionals should play, if any, in AIDS-related policy analysis and social advocacy. In the summer of 1986, the School of Public Health at the University of California at Berkeley initiated a telegram sent by the Deans of all 23 schools of public health to protest US Department of Justice AIDS policy and, in the subsequent fall, the school expanded its public educational role in an unprecedented manner by initiating and issuing, with California's other three schools of public health, a policy analysis of Proposition 64, the LaRouche AIDS Quarantine Initiative. That analysis exposed the proposition's fallacious claims regarding casual transmission of AIDS and served to educate the electorate on the likely public health impact of this deleterious legislation. Based on these experiences, and in light of ongoing national controversy regarding AIDS, we believe schools of public health have an important role to play in policy analysis, and individual public health professionals have a role to play in social advocacy. 相似文献
4.
Paediatric dacryocystorhinostomy 总被引:1,自引:0,他引:1
KN Hakin FRCS FRCOphth TJ Sullivan FRACO FRACS A Sharma FCOphth † RAN Welham FRCS FCOphth † 《Clinical & experimental ophthalmology》1994,22(4):231-235
Of 258 cases of dacryocystorhinostomy performed on children in the period September 1981 to September 1991, 130 were for simple, unresolved congenital nasolacrimal duct obstruction. Other indications for surgery included punctal agenesis, lacrimal fistula, post-traumatic and post-inflammatory canalicular obstruction. Of 177 children without canalicular pathology, 171 (96%) were relieved of symptoms with one operation, without canalicular intubation. Of 81 cases with canalicular disease, 55 of 70 (79%) who underwent DCR plus canalicular intubation, and 10 of 11 who underwent DCR plus Lester-Jones tube, were substantially improved with one operation. No child required peroperative or postoperative blood transfusion. Dacryocystorhinostomy in childhood, in experienced surgical hands, is a safe procedure, achieving relief of symptoms in most cases, particularly in the absence of canalicular disease. 相似文献
5.
6.
7.
Nancy S Krieger Kevin K Frick Kelly LaPlante Strutz Anne Michalenka David A Bushinsky 《Journal of bone and mineral research》2007,22(6):907-917
Chronic metabolic acidosis induces net Ca efflux from bone; this osteoclastic bone resorption is mediated by increased osteoblastic prostaglandin synthesis. Cyclooxygenase, the rate-limiting enzyme in prostaglandin synthesis, is present in both constitutive (COX-1) and inducible (COX-2) forms. We report here that acidosis increases both osteoblastic RNA and protein levels for COX-2 and that genetic deficiency or pharmacologic inhibition of COX-2 significantly reduces acid-induced Ca efflux from bone. INTRODUCTION: Incubation of neonatal mouse calvariae in medium simulating physiologic metabolic acidosis induces an increase in osteoblastic prostaglandin E2 (PGE2) release and net calcium (Ca) efflux from bone. Increased PGE2 is necessary for acid-induced bone resorption, because inhibition of cyclooxygenase activity with indomethacin significantly decreases not only PGE2 production but also Ca release. Cyclooxygenase is present in both constitutive (COX-1) and inducible (COX-2) forms. Because COX-2 activity has been implicated in several forms of pathological bone resorption, we tested the hypothesis that COX-2 is critical for acid-induced, cell-mediated bone Ca efflux. MATERIALS AND METHODS: To determine the effect of metabolic acidosis on COX-2 RNA and protein, primary cells isolated from neonatal CD-1 mouse calvariae were cultured in neutral (Ntl) or physiologically acidic medium (Met). RNA levels for COX-2 and COX-1 were measured by quantitative real-time PCR. Levels of COX-2 and COX-1 protein were measured by immunoblot analysis. To determine the effect of acidosis on bone Ca efflux in genetically deficient COX-2 mice, mice heterozygous for the COX-2 knockout (strain B6;129S7-Ptgs2(tm1Jed)/J) were used as breeders, and neonatal calvariae were cultured in Ntl or Met. To determine the effects of the specific COX-2 inhibitor, NS398, on acid-induced bone resorption, CD-1 calvariae were incubated in Ntl or Met with or without NS398 (1 microM). Medium PGE2 was assayed by ELISA. RESULTS: Incubation of mouse calvarial cells in Met significantly increased COX-2 RNA and protein levels without a change in COX-1. Increased COX-2 protein levels in response to Met were also observed in cultured calvariae. Acid-induced, cell-mediated Ca efflux from B6;129S7-Ptgs2(tm1Jed)/J calvariae was dependent on genotype. From 0 to 24 h, when physicochemical Ca efflux predominates, Met significantly increased net Ca efflux in all genotypes. After 24 h, when cell-mediated Ca efflux predominates, Met induced greater Ca efflux from (+/+) than from (+/-), and there was no increase from (-/-). In calvariae from CD-1 mice, NS398 significantly inhibited both the acid-induced increase in PGE2 and Ca release. CONCLUSIONS: The specific acid-induced increase in COX-2 RNA and protein levels and the dependency of the increased Ca efflux on COX-2 activity, as determined by both genetic deficiency and pharmacologic inhibition, show that COX-2 is critical for acid-induced, cell-mediated bone resorption. 相似文献
8.
B van der Loo E Krieger J Katavic S Spring V Rousson B Amann-Vesti R Koppensteiner 《European journal of vascular and endovascular surgery》2005,30(5):469-474
OBJECTIVE: To determine the relationship between carotid intima-media thickness (IMT), carotid wall shear stress (WSS) and restenosis after femoro-popliteal percutaneous transluminal angioplasty (PTA). PATIENTS AND METHODS: Thirty-one subjects (18 men, 13 women, median age 69 years) treated with femoro-popliteal PTA for symptomatic peripheral arterial occlusive disease were enrolled. On admission, IMT, internal diameter and blood velocity of the common carotid artery (CCA) were assessed by high-resolution ultrasonography. Blood viscosity was measured and carotid WSS was calculated. Patients were followed up for 6 months for the occurrence of significant restenosis (>50%) as documented by duplex ultrasonography. Two patients were lost to follow-up. RESULTS: Fourteen patients (48%) developed restenosis at 6 months. IMT and WSS were not different in patients without and with restenosis (IMT: 0.90 (0.85-0.97) vs. 0.89 (0.84-0.93) mm, p = 0.51; WSS: 14.1 (11.9-19.2) vs. 15.9 (12.8-21.5) dyne/cm2, p = 0.48). The hazard ratio of incident restenosis as estimated by Cox regression analysis was 0.04 for IMT (p = 0.23; 95% CI 0.0001-8.22) and 1.07 for WSS (p = 0.10; 95% CI 0.98-1.17). CONCLUSIONS: In this pilot study involving a limited number of patients, carotid IMT and carotid WSS are not significantly related to restenosis at 6 months after femoro-popliteal PTA. This might be the result of different underlying pathophysiology for atherosclerosis and restenosis. 相似文献
9.
Intracranial Angioplasty and Stenting in the Awake Patient 总被引:1,自引:0,他引:1
Alex Abou-Chebl MD Derk W. Krieger MD Christopher T. Bajzer MD Jay S. Yadav MD FACC 《Journal of neuroimaging》2006,16(3):216-223
BACKGROUND AND PURPOSE: Endovascular treatment for intracranial atherosclerosis is evolving, but complications remain an issue. Most interventions are performed under general anesthesia, preventing intraprocedural clinical evaluations. We describe our approach to intracranial angioplasty and stenting, using local rather than general anesthesia, and intraprocedural neurological assessment. METHODS: We prospectively collected procedural and outcome information on all patients undergoing intracranial angioplasty and stenting. Patients underwent interventions under local anesthesia with mild intravenous sedation or analgesia only if needed. Intraoperative neurological evaluations were performed, and symptomatology was used to guide the interventional technique. RESULTS: Forty-eight arteries in 40 patients with a mean age of 65.2 years were treated. Thirty-two anterior and 16 posterior circulation segments were treated. Technical success was achieved in 100% of patients with reduction of the mean pretreatment stenosis from 85 +/- 8.6% to 7 +/- 10.1%. Stents were deployed in 40 segments; five patients were treated with drug-eluting stents. The cobalt-chromium coronary stents were the easiest to deliver. Thirty-seven patients were treated under local anesthesia and, of those, 61.4% experienced intraprocedural symptoms that led to some alteration of the interventional technique. Headache was the most common symptom, and, when persistent, it heralded the occurrence of subarachnoid hemorrhage. There were seven total neurological complications, but only five (10.5%) led to permanent morbidity (4 strokes) or mortality (1 death). CONCLUSIONS: Intracranial angioplasty and stenting can be successfully performed using coronary techniques and equipment including drug-eluting stents. Local anesthesia permits neurological evaluations and often leads to the adjustment of the interventional technique, potentially making the procedure safer. 相似文献
10.
Factors influencing women to undergo screening mammography 总被引:2,自引:0,他引:2