全文获取类型
收费全文 | 7145篇 |
免费 | 771篇 |
国内免费 | 7篇 |
专业分类
耳鼻咽喉 | 128篇 |
儿科学 | 203篇 |
妇产科学 | 159篇 |
基础医学 | 1068篇 |
口腔科学 | 184篇 |
临床医学 | 854篇 |
内科学 | 1466篇 |
皮肤病学 | 123篇 |
神经病学 | 533篇 |
特种医学 | 242篇 |
外科学 | 951篇 |
综合类 | 197篇 |
预防医学 | 723篇 |
眼科学 | 189篇 |
药学 | 387篇 |
中国医学 | 4篇 |
肿瘤学 | 512篇 |
出版年
2021年 | 117篇 |
2020年 | 62篇 |
2019年 | 94篇 |
2018年 | 121篇 |
2017年 | 103篇 |
2016年 | 113篇 |
2015年 | 128篇 |
2014年 | 162篇 |
2013年 | 220篇 |
2012年 | 365篇 |
2011年 | 329篇 |
2010年 | 203篇 |
2009年 | 194篇 |
2008年 | 291篇 |
2007年 | 329篇 |
2006年 | 276篇 |
2005年 | 263篇 |
2004年 | 265篇 |
2003年 | 248篇 |
2002年 | 217篇 |
2001年 | 230篇 |
2000年 | 223篇 |
1999年 | 220篇 |
1998年 | 92篇 |
1997年 | 101篇 |
1996年 | 90篇 |
1995年 | 70篇 |
1994年 | 71篇 |
1993年 | 71篇 |
1992年 | 156篇 |
1991年 | 164篇 |
1990年 | 166篇 |
1989年 | 172篇 |
1988年 | 160篇 |
1987年 | 132篇 |
1986年 | 156篇 |
1985年 | 144篇 |
1984年 | 122篇 |
1983年 | 132篇 |
1982年 | 69篇 |
1981年 | 51篇 |
1980年 | 65篇 |
1979年 | 84篇 |
1978年 | 71篇 |
1977年 | 52篇 |
1976年 | 58篇 |
1974年 | 68篇 |
1973年 | 54篇 |
1971年 | 56篇 |
1970年 | 50篇 |
排序方式: 共有7923条查询结果,搜索用时 15 毫秒
81.
Sixty-three normal subjects and 94 abnormal patients, most of whom had glaucoma, were tested in the central visual field using a threshold-related, eccentricity-compensated, spatially adaptive suprathreshold screening program and a full-threshold program on the Humphrey field analyzer. The initial stimulus locations on the screening test were identical to those of the threshold test; additional screening stimuli were presented surrounding each missed initial stimulus. Surprisingly, this spatial enhancement strategy did not improve sensitivity or specificity rates of the screening beyond that achieved by considering the initial stimulus locations alone. Points missed during screening often showed a depressed sensitivity rate (measured threshold greater than 6 dB below the age-corrected normal reference value) in the same area of the threshold field. This was true in fields from abnormal and normal subjects. This finding of persistent shallow defects in the same test session among otherwise normal persons has disturbing implications for the importance of "confirmed" defects in the diagnosis of disease. 相似文献
82.
Studies of the human placental vasculature suggest a low resistance circulation. Using wire myography, endothelial-dependent relaxation of human chorionic plate arteries has been difficult to demonstrate with any consistency. However, histamine has been suggested to relax placental vessels in the perfused organ in vitro. Here we aimed to demonstrate endothelial-dependent relaxation to histamine under physiological conditions of stretch and oxygenation. Histamine administration to pre-contracted arteries induced a triphasic response; an initial contraction followed by a dilatation which stabilized to a significant relaxation compared to time control arteries. Relaxation was partially inhibited by blockers of endothelial-dependent relaxation pathways. The initial contraction was abolished by H(1)-receptor blockade with mepyramine. The relaxation was significantly reduced by H(2)-receptor blockade with famotidine but only abolished in the presence of both H(1)- and H(2)-receptor antagonists. In conclusion, histamine induced contraction and relaxation of human chorionic plate arteries. Our data suggest that contraction is mediated by activation of H(1)-receptors. Relaxation occurs directly, via activation of H(2)-receptors on vascular smooth muscle cells, and indirectly via H(1)-receptor stimulation of endothelial-dependent relaxation. 相似文献
83.
Ralph G. Mills 《The Journal of experimental medicine》1919,30(5):505-529
The testicular changes in pneumonia are without clinical manifestations, are non-specific, focal in character, independent of the infecting organisms or the antecedent disease, and vary in severity directly with the total length of the illness. The process is a continuous one, divisible into stages in which the following features are recognizable: (1) cessation of spermatogenesis; (2) degeneration of preformed spermatocytes, spermatids, and spermatozoa; (3) desquamation of altered cells and fragments of the same; (4) formation of giant cells in the tubule walls with subsequent liberation into the lumen; (5) disappearance of all desquamated cells and all those derived from the spermatogonia by mitosis; (6) in some instances thickening of the hyaline layer of the basement membrane. Older lesions are frequently found which continue the structural alteration of the tubules by hyalinosis and destruction of cells until they ultimately disappear. These lesions are not believed to be connected with the present illness. Edema may represent the acute injury in another form, and round cell infiltration suggests that possibly other factors than toxins may have a part in the tissue alterations. In the absence of definite evidence to the contrary, the cause is assumed to be circulating toxins, as Wolbach (12) claims for influenzal cases. The hemolytic streptococcus produced more extensive changes, both epithelial and interstitial, in primary pneumonia occurring during the measles epidemic than when pneumonia followed as a secondary infection; in the latter cases the pulmonary complications covered a relatively shorter period. Measles and epidemic influenza had little apparent effect upon the testes, except that the former caused mild inhibition of spermatogenesis; evidence regarding the latter is inconclusive. The Pfeiffer bacillus was always associated with other organisms, in primary infections and in those following measles. It occurred alone in a few cases after epidemic influenza, but the testicular lesion was not distinctive. The pneumococcus when alone in primary infections or after an epidemic disease produced a uniformly mild picture which was not intensified when associated with the influenza bacillus. Giant cells were much more frequent after influenzal pneumonia regardless of its cause and were associated with large numbers of other desquamated cells. They are formed in the walls of tubules by futile mitotic effort and incomplete protoplasmic separation, the abnormality of the process being further suggested by the early severing of cytoplasmic attachments and rapid desquamation. The series is unique in its uniformity, in the care exercised in the bacteriological examinations, and in the relative freedom from complicating factors. 相似文献
84.
In 80 women who had reversal of sterilisation, a study was made of their clinical features at the time of sterilisation and of the factors related to successful outcome. Compared with controls at the time of sterilisation, the women requesting reversal were younger, of lower social class and of higher parity; in addition they were more likely to have an unstable relationship and to have been sterilised following a recent pregnancy. After reversal, intrauterine pregnancy occurred in 26/80 (32.5%) and ectopic pregnancy in 6/80 (7.5%), the majority of successful pregnancies occurring in younger women within one year of reversal following a non-destructive method of tubal occlusion. There was no evidence that techniques of management, including the use of an operating microscope, significantly influenced outcome, and controlled trials will be required to establish their efficacy. 相似文献
85.
Angela B. Echeverria Bernardino C. Branco Kay R. Goshima John D. Hughes Joseph L. Mills Sr. 《American journal of surgery》2014,208(6):974-980
Background
Thoracic aortic emergencies account for 10% of thoracic-related admissions in the United States and remain associated with high morbidity and mortality rates. Open repair has declined owing to the emergence of thoracic endovascular aortic repair (TEVAR), but data on emergency TEVAR use for acute aortic pathology remain limited. We therefore reviewed our experience.Methods
We retrospectively evaluated emergency descending thoracic aortic endovascular interventions performed at a single academic level 1 trauma center between January 2005 and August 2013 including all cases of traumatic aortic injury, ruptured descending thoracic aneurysm, penetrating atherosclerotic ulcer, aortoenteric fistula, and acute complicated type B dissection. Demographics, clinical data, and outcomes were extracted. Stepwise logistic regression was used to identify independent risk factors for death.Results
During the study period, 51 patients underwent TEVAR; 22 cases (43.1%) were performed emergently (11 patients [50.0%] traumatic aortic injury; 4 [18.2%] ruptured descending thoracic aneurysm; 4 [18.2%] complicated type B dissection; 2 [9.1%] penetrating aortic ulcer; and 1 [4.5%] aortoenteric fistula). Overall, 72.7% (n = 16) were male with a mean age of 54.8 ± 15.9 years. Nineteen patients (86.4%) required only a single TEVAR procedure, whereas 2 (9.1%) required additional endovascular therapy, and 1 (4.5%) open thoracotomy. Four traumatic aortic injury patients required exploratory laparotomy for concomitant intra-abdominal injuries. During a mean hospital length of stay of 18.9 days (range, 1 to 76 days), 3 patients (13.6%) developed major complications. In-hospital mortality was 27.2%, consisting of 6 deaths from traumatic brain injury (1); exsanguination in the operating room before repair could be achieved (2); bowel ischemia (1) and multisystem organ failure (1); and family withdrawal of care (1). A stepwise logistic regression model identified 24-hour packed red blood cell requirements ≥4 units, admission mean arterial pressure <60 mm Hg, and 24-hour fresh frozen plasma to packed red blood cell (pRBC) ratio <1:1.5 as independent risk factors for death in this cohort. During a mean follow-up of 369 days (range, 35 to 957 days), no subsequent major complications or deaths occurred. All patients underwent serial computed tomographic angiography surveillance, and no device-related problems were identified during intermediate follow-up.Conclusions
Thoracic aortic emergencies remain challenging. Our experience in a moderate-volume center supports the utilization of TEVAR in the acute setting. Twenty-four-hour pRBC requirements ≥4 units, admission mean arterial pressure <60 mm Hg, and 24 hour fresh frozen plasma to pRBC ratio <1:1.5 were independently associated with death. 相似文献86.
By decreasing plaque burden, atherectomy provides an alternative to angioplasty and stenting as a means of revascularizing patients with peripheral arterial disease. A new atherectomy device (SilverHawk) has recently been approved by the Food and Drug Administration, but the results with its use are unclear. We analyzed a series of consecutive patients undergoing atherectomy. We retrospectively reviewed the charts of 35 patients undergoing infrainguinal (IF) atherectomy in 38 limbs. The Trans-Atlantic Inter-Society Consensus (TASC) classification and Society of Vascular Surgery runoff scores were calculated. Time to event analysis was performed using Kaplan-Meier estimates. Risk factors affecting patency were analyzed with a multivariate Cox model. Mean patient age was 70 +/- 9.6 years. Indications for intervention were claudication (26%), rest pain (21%), and tissue loss (53%). Femoropopliteal (FP) atherectomy was performed in 68% and tibial atherectomy in 32%. For FP lesions, the TASC distribution was A, 42%; B, 23%; C, 4%; and D, 15%. The average lesion treatment length was 9.4 +/- 10.6 cm (range 1-40), and the runoff score was 5.1 +/- 3.5. For tibial lesions, the TASC distribution was A, 0%; B, 17%; C, 8%; and D, 75%. The average lesion treatment length was 9.2 +/- 6.0 cm (range 2-20), with a runoff score of 5.4 +/- 2.4. A total of 39% of patients had prior IF interventions. Adjunctive angioplasty of the atherectomized lesion was performed in 55% of cases, stenting in 0%, and adjunctive therapy for tandem lesions in 39%. The postoperative ankle-brachial index increased by 0.30 +/- 0.14 and toe pressures increased by 40 +/- 32.4 mm Hg. Mean follow-up was 10 +/- 8 months (range 0.3-23). During the studied period, seven patients required major limb amputation and five open surgical revascularization. Total primary and secondary patency rates were 66% and 70% at 1 year, respectively. Primary and secondary patency rates for FP atherectomy were 68% and 73% at 1 year, respectively. The limb salvage rate was 74% at 6 months. Patients with prior interventions in the atherectomized segment had an almost 10-fold decrease in primary patency. Atherectomy produces acceptable results, similar to those in reported series of conventional balloon angioplasty/stenting. Patients with prior IF interventions had a nearly 10-fold decrease in primary patency. A greater than sixfold decrease in patency rates was noted in patients who underwent simultaneous inflow or outflow procedures, but this finding did not reach statistical significance (p = 0.082). Future studies should focus on cost comparisons with other treatments such as angioplasty and stenting, and prospective randomized trials should be performed to compare these treatment alternatives. 相似文献
87.
88.
89.
Jennifer Mills Nicole Burton Norine Schmidt Oscar Salinas John Hembling Alberto Aran Michele Shedlin Patricia Kissinger 《Journal of immigrant and minority health / Center for Minority Public Health》2013,15(3):606-613
High rates of sex and drug risk behaviors have been documented among Latino migrant men in the US. Whether these behaviors were established in the migrants’ home countries or were adopted in the US has not been described and has implications for prevention strategies. Quarterly surveys were conducted to gather information on selected sex and drug risk practices of Latino migrant men who arrived in New Orleans after Hurricane Katrina seeking work. Both kappa scores and McNemar’s tests were performed to determine if practice of these behaviors in home country was similar to practice post-emigration to the US. Female sex worker (FSW) patronage, same sex encounters (MSM), and crack cocaine use was more likely to occur post- rather than pre-emigration. Of those who ever engaged in these selected behaviors, most adopted the behavior in the US (i.e., 75.8 % of FSW patrons, 72.7 % of MSM participants, and 85.7 % of crack cocaine users), with the exception of binge drinking (26.8 %). Men who were living with a family member were less likely to adopt FSW patronage OR = 0.27, CI = 0.10–0.76, whereas men who earned >$465 per week were more likely to adopt crack cocaine use OR = 6.29 CI = 1.29, 30.57. Interventions that facilitate the maintenance of family cohesion and provide strategies for financial management may be useful for reducing sex and drug risk among newly arrived migrants. 相似文献
90.