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   2330篇
  免费   246篇
  国内免费   49篇
耳鼻咽喉   7篇
儿科学   128篇
妇产科学   23篇
基础医学   316篇
口腔科学   117篇
临床医学   285篇
内科学   532篇
皮肤病学   40篇
神经病学   179篇
特种医学   239篇
外科学   253篇
综合类   25篇
一般理论   1篇
预防医学   155篇
眼科学   32篇
药学   177篇
中国医学   4篇
肿瘤学   112篇
  2021年   22篇
  2020年   15篇
  2019年   25篇
  2018年   72篇
  2017年   45篇
  2016年   39篇
  2015年   41篇
  2014年   52篇
  2013年   81篇
  2012年   67篇
  2011年   82篇
  2010年   69篇
  2009年   68篇
  2008年   76篇
  2007年   113篇
  2006年   71篇
  2005年   120篇
  2004年   154篇
  2003年   88篇
  2002年   59篇
  2001年   62篇
  2000年   57篇
  1999年   65篇
  1998年   63篇
  1997年   67篇
  1996年   59篇
  1995年   44篇
  1994年   41篇
  1993年   47篇
  1992年   44篇
  1991年   40篇
  1990年   44篇
  1989年   68篇
  1988年   64篇
  1987年   59篇
  1986年   46篇
  1985年   43篇
  1984年   23篇
  1983年   33篇
  1982年   24篇
  1981年   18篇
  1980年   20篇
  1979年   22篇
  1978年   20篇
  1977年   31篇
  1976年   17篇
  1975年   22篇
  1974年   15篇
  1973年   10篇
  1972年   10篇
排序方式: 共有2625条查询结果,搜索用时 0 毫秒
71.
Integrin α(X)β(2) functions as complement receptor for iC3b and mediates recognition and phagocytosis of pathogens. We used negative-stain EM to examine the α(X)β(2) interaction with iC3b. EM class averages of α(X)β(2) in complex with iC3b define the binding sites on both the integrin and iC3b. iC3b contains C3c and thioester domain moieties linked by a long flexible linker. The binding site is on the key ring of the C3c moiety, at the interface between the MG3 and MG4 domains. Similar complexes are seen between α(X)β(2) and the C3c fragment. α(X)β(2) binds through the α(X) αI domain, on the face known to bear the metal ion-dependent adhesion site, at the opposite end of the αI domain from its site of insertion in the β-propeller domain.  相似文献   
72.
Many different materials are proposed for reconstruction of traumatic orbital floor defects. Donor-site morbidity of autologous transplants and infections or extrusions of nonresorbable implants lead to a widespread use of resorbable, alloplastic materials such as polydioxanone (PDS). The goal of this study was to evaluate the prevalence of orbital floor fracture-related problems after surgical treatment using PDS. Ophthalmologic and clinical examinations were performed at 194 patients before orbital floor reconstruction, 14 days and 6 months after surgery (approximate defect sizes: <1 cm2, n=50; 1-2 cm2, n=97; >2 cm2, n=47). Clinical findings including the ocular motility, the sensibility of the infraorbital nerve, and the position of the globe were evaluated. For statistical analysis of categorical data, confidence intervals of percentages were determined. Linear relationships between 2 variables were assessed with Pearson correlation analysis. A reduced ocular motility was diagnosed in 60 patients (31%) before surgery; in 14 patients (7%), 2 weeks; and in 10 patients (5%), 6 months after surgery. Infraorbital hypesthesia was found in 120 patients (62%) before surgery; in 47 patients (24%), 2 weeks; and in 35 patients (18%), 6 months after surgery. An enophthalmos was present in 10 patients (5%) before surgery, and in 4 patients (2%), 6 months after surgery. Our data suggest that PDS is a suitable implant for orbital floor reconstruction with acceptable low rates of infraorbital hypesthesia, bulbus motility disturbances, and enophthalmos. Polydioxanone can also be used for orbital floor defects exceeding 2 cm2.  相似文献   
73.
Zhou YF  Eng ET  Zhu J  Lu C  Walz T  Springer TA 《Blood》2012,120(2):449-458
In the present study, we re-annotated von Willebrand factor (VWF), assigned its entire sequence to specific modules, and related these modules to structure using electron microscopy (EM). The D domains are assemblies of smaller modules visible as lobes in EM. Modules in the D-domain assemblies include von Willebrand D, 8-cysteine, trypsin inhibitor-like, E or fibronectin type 1-like domains, and a unique D4N module in D4. The D1-D2 prodomain shows 2 large connected assemblies, each containing smaller lobes. The previous B and C regions of VWF are re-annotated as 6 tandem von Willebrand C (VWC) and VWC-like domains. These 6 VWC domains correspond to 6 elongated domains that associate in pairs at acidic pH in the stem region of VWF dimeric bouquets. This correspondence is demonstrated by binding of integrin α(IIb)β(3) to the fourth module seen in EM, VWC4, which bears the VWF Arg-Gly-Asp motif. The C-terminal cystine knot domain dimerizes end-to-end in a manner predicted by homology to TGF-β and orients approximately perpendicular to the VWC domains in dimeric bouquets. Homologies of domains in VWF to domains in other proteins allow many disulfide bonds to be tentatively assigned, which may have functional implications.  相似文献   
74.
75.
76.

Purpose

Squamous cell cancer (SCC) of the pharyngoesophageal junction area has a poor prognosis mainly due to late symptom manifestation and diagnosis. Treatment of choice is still pharyngolaryngoesophagectomy, substantially affecting quality of life. Limited surgical procedures have been adopted as well. The aim of this retrospective study was to evaluate whether the extent of resection influences postoperative safety and mortality.

Methods

From 1984 to 2006, 66 patients were operated at a single tertiary referral center. Nineteen patients (28.8 %) had SCC of the hypopharynx and 47 patients (71.2 %) had SCC of the cervical and cervicothoracic esophagus. Thirty-five patients (53.0 %) underwent cervical esophageal resection (CE) and 31 underwent total esophagectomy (TE). In 39 patients (59.1 %), the larynx was preserved. Thirteen patients (19.7 %) underwent multimodal treatment.

Results

Overall postoperative morbidity was 69.7 % and reoperation rate reached 28.8 %. TE (P?=?0.03) and larynx preservation (P?=?0.02) were followed by a higher rate of non-lung infections compared with CE and pharyngolaryngectomy, respectively. Pulmonary complications have been observed more frequently after larynx preservation (P?=?0.02). Hospital mortality was 9.1 %. Four patients died after TE (12.9 %) and two patients died after CE (5.7 %). In all of them, the larynx had been preserved (15.4 %). Overall, 53 patients (80.3 %) died until follow-up. One-year and 5-year survival in patients with the major tumor burden at the cervicothoracic site was 35.7 and 0 %.

Conclusions

CE can be recommended as long as R0 resection is warranted. The advantage of larynx preservation is gained by higher morbidity and mortality rates and may not be recommended as standard procedure. Surgery may not be appropriate for advanced SCC in the cervicothoracic region.  相似文献   
77.
Abstract

The traditional PACE approach was compared with a modified PACE approach, which incorporated a semantic classification task for the training of lexical-semantic difficulties. In a cross-over design, four patients were treated over a period of five weeks. The modified PACE approach was found to have a more effective impact on the improvement of both verbal naming and general communicative behaviour.  相似文献   
78.
Bundesgesundheitsblatt - Gesundheitsforschung - Gesundheitsschutz - In den letzten Jahren konnte der immense Vorteil der Muttermilchernährung für Frühgeborene belegt werden: in Bezug...  相似文献   
79.

Background

Although loggers in Alaska are at high risk for occupational injury, no comprehensive review of such injuries has been performed since the mid‐1990s. We investigated work‐related injuries in the Alaska logging industry during 1991‐2014.

Methods

Using data from the Alaska Trauma Registry and the Alaska Occupational Injury Surveillance System, we described fatal and nonfatal injuries by factors including worker sex and age, timing and geographic location of injuries, and four injury characteristics. Annual injury rates and associated 5‐year simple moving averages were calculated.

Results

We identified an increase in the 5‐year simple moving averages of fatal injury rates beginning around 2005. While injury characteristics were largely consistent between the first 14 and most recent 10 years of the investigation, the size of logging companies declined significantly between these periods.

Conclusions

Factors associated with declines in the size of Alaska logging companies might have contributed to the observed increase in fatal injury rates.
  相似文献   
80.
When humans observe a face, the eyes, mouth and nose regions are the preferred targets of the centre of gaze, with the outlines of eye position recordings approximating a triangle with vertices located in the centre of the eyes and mouth [31]. We studied the significance of cutaneous asymmetries inside and outside the Yarbus triangle on the basis of the assessment of digitally-manipulated images by 201 independent judges. We show that certain facial variations (such as naevi) are more attractive when asymmetrical than symmetrical (p<?0,001). They appear more attractive when located laterally rather than medially, particularly so when located outside the Yarbus triangle as compared to inside it (p<?0,001). The significance of facial symmetry increases significantly when approaching the Yarbus triangle or the midline, respectively.  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