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   3052篇
  免费   247篇
  国内免费   6篇
耳鼻咽喉   29篇
儿科学   141篇
妇产科学   90篇
基础医学   467篇
口腔科学   110篇
临床医学   346篇
内科学   534篇
皮肤病学   88篇
神经病学   319篇
特种医学   149篇
外科学   353篇
综合类   44篇
一般理论   3篇
预防医学   243篇
眼科学   44篇
药学   192篇
中国医学   1篇
肿瘤学   152篇
  2023年   27篇
  2022年   26篇
  2021年   55篇
  2020年   31篇
  2019年   60篇
  2018年   72篇
  2017年   51篇
  2016年   50篇
  2015年   70篇
  2014年   76篇
  2013年   122篇
  2012年   153篇
  2011年   173篇
  2010年   107篇
  2009年   104篇
  2008年   178篇
  2007年   166篇
  2006年   138篇
  2005年   119篇
  2004年   118篇
  2003年   95篇
  2002年   95篇
  2001年   66篇
  2000年   74篇
  1999年   83篇
  1998年   44篇
  1997年   46篇
  1996年   53篇
  1995年   50篇
  1994年   41篇
  1993年   33篇
  1992年   50篇
  1991年   42篇
  1990年   43篇
  1989年   55篇
  1988年   50篇
  1987年   31篇
  1986年   36篇
  1985年   41篇
  1984年   38篇
  1983年   30篇
  1982年   19篇
  1980年   23篇
  1979年   21篇
  1977年   20篇
  1976年   24篇
  1974年   23篇
  1973年   19篇
  1972年   20篇
  1970年   19篇
排序方式: 共有3305条查询结果,搜索用时 15 毫秒
41.
42.
43.
Team Reach Out Biloxi is a nursing student-initiated service-learning project with the goal of providing ongoing assistance to the victims of Hurricane Katrina. On 6 different occasions from 2005 to 2008, Purdue nursing students integrated their leadership skills with application of public health knowledge, compassion, and concern as they worked in partnership with the Gulfport region Coastal Family Health Clinics (CFHC). This article reviews the service-learning framework, course planning, and implementation of a 3-year posthurricane disaster project.  相似文献   
44.
Team Reach Out started as a student-initiated service-learning project with the goal of providing on-going assistance to the victims of Hurricane Katrina. Four years after Hurricane Katrina, Team Reach Out refocused efforts to Cape Town, South Africa, where 4 senior nursing students and 1 science student integrated their leadership skills with the application of public health knowledge, compassion, and concern to work in partnership with several international health agencies. This article reviews the service-learning framework, course planning, and implementation of a recent service-learning project.  相似文献   
45.
γ-去氢骆驼蓬碱等咔啉类生物碱的辐射防护作用   总被引:8,自引:0,他引:8  
γ- Harmine(Ⅰ),’harmine(Ⅱ )and harmaline(Ⅲ )were isolated from PeganumHarmala L.( Zygophylaceae).Tests were conducted with mice to detect whether γ- harmine( a newcompound), harmine,harmof(Ⅳ)and harmalol(Ⅴ) are effective radioprotective compounds againstγ-ray irradiation, Intraperitoneal injection of the hydrochlorides of the four alkaloids 50~80mg·kg-1×1 in NIH male mice 30~45 minutes before 8.6~9. 7 Gy whole body 60Co irradiationsignificantly increased the survival effects(1. 33~2. 61)and 30-day survivai rate in comparison withcontrol mice.The results indicatethat γ- harmine exhibited relatively good radioprotective effect.γ-harmine is the first alkaloid isolated from a plant having ptotective effects against whole-body lethal irradiation in mice.  相似文献   
46.
The purpose of this study was to test whether successful cryopreservation of osteochondral tissue is possible and whether, with the appropriate surgical procedure, it can be used for the successful repair of focal articular defects within joints. Fresh (nonfrozen) and snap-frozen (plunged in liquid nitrogen and thawed in a water bath at 37 degrees C, repeated three times) autografts were used as positive and negative controls, respectively. Snap-frozen, frozen (fresh tissue placed in a freezer at -80 degrees C), and cryopreserved (immersed in 10% dimethyl sulfoxide for 30 minutes and then frozen at 1 degrees C/min to -80 degrees C) allografts were transplanted into the knees of adult sheep. Outcomes were evaluated 3, 6, and 12 months after transplantation. The morphological, histological, biochemical, and biomechanical behaviors and characteristics of the graft cartilage, the host cartilage adjacent to the grafts, and the opposing tibial cartilage were assessed. Freezing protocols that yielded poor chondrocyte recovery after thawing (frozen and snap-frozen) resulted in poor overall graft outcome. The cryopreservation protocol, however, resulted in intermediate recovery (50%) of chondrocytes and in intermediate overall graft outcome compared with fresh autografts. The membrane integrity of the allograft chondrocytes immediately following cryopreservation was identified as the most reliable predictor of long-term outcome of the graft. Further improvements in cryopreservation technique may lead to an effective method of banking osteochondral tissue for successful transplantation for the repair of focal defects and larger joint reconstructions.  相似文献   
47.

Purpose

The aim of the study was to verify the ability of nanoparticulate bioactive glass (BAG) to infiltrate into the porous titanium (Ti) layer on Ti-based implants to promote osseointegration.

Methods

The porous titanium layer on Ti-based implants was impregnated with nanoparticulate BAG. The implants without or with BAG were implanted bilaterally in tibial holes of ten New Zealand white rabbits. The rabbits were sacrificed after ten weeks for examinations. Beside histological examination, EDXS analysis of polished cross-sections of explanted implants was also performed with the aim to quantitatively evaluate the bone-to-pore contact and bone-in-pore ratio.

Results

After ten weeks, EDXS analyses of cross-sections of the explanted implants confirmed that bioactive glass was fully resorbed and that the pores throughout the thickness of the porous titanium layer were to a large extent filled with a new bone. In the absence of bioactive glass, only the outer part of the porous layer was filled with bone. The implants without BAG in the porous Ti-layer exhibited similar bone-to-pore contact, while significant improvement of bone ingrowth into the pores was observed for the implants with BAG (38%), as opposed to those without it (22%).

Conclusion

This study confirmed that the nanoparticulate bioactive glass within the porous titanium surface layer on implants promotes osseointegration and stimulates the formation of bone within the pores.  相似文献   
48.
BACKGROUND: Sera of patients with IgA nephropathy (IgAN) contain circulating immune complexes (CIC) composed of galactose-deficient IgA1 complexed with antiglycan antibodies. The role of these CIC in the pathogenesis of IgAN is not known. METHODS: We studied how proliferation of cultured mesangial cells (MC) is affected by CIC prepared from sera of IgAN patients and healthy control subjects using size-exclusion chromatography. CIC-containing fractions were added to serum-starved MC in culture, and cell proliferation was measured using (3)H-thymidine incorporation. The results were confirmed by staining MC using an antibody against proliferating cell nuclear antigen. RESULTS: The incubation of starved MC with serum fractions with M(r) 800 to 900 kD, rich with galactose-deficient IgA1, stimulated proliferation, while fractions with smaller complexes were inhibitory. Furthermore, CIC-containing larger molecular mass fractions isolated from serum of an IgAN patient collected during an episode of macroscopic hematuria stimulated MC proliferation more than CIC obtained during a subsequent quiescent phase. To examine the role of IgA, we removed IgA1 from serum before fractionation. The resultant IgA1-depleted fractions were devoid of stimulatory IgA-CIC. Sera of IgAN patients were also fractionated after addition of desialylated galactose-deficient polymeric IgA1 to form additional immune complexes. Supplementation with a small quantity of this IgA1 increased cellular proliferation in assays using serum fractions of M(r)>/=800 to 900 kD; uncomplexed IgA1 did not affect MC proliferation significantly. In contrast, supplementation with a larger quantity of this IgA1 inhibited cellular proliferation in assays using serum fractions of M(r) 700 to 800 kD. CONCLUSION: Overall, these findings suggest that CIC containing aberrantly glycosylated IgA1 affect proliferation of MC in vitro and, thus, likely play a role in the pathogenesis of IgAN.  相似文献   
49.
OBJECTIVE: To determine the benefit of screening for blunt carotid arterial injuries (BCI) in patients who are asymptomatic. SUMMARY BACKGROUND DATA: Blunt carotid arterial injuries have the potential for devastating complications. Published studies report 23% to 28% mortality rates, with 48% to 58% of survivors having permanent severe neurologic deficits. Most patients have neurologic deficits when the injury is diagnosed. The authors hypothesized that screening patients who are asymptomatic and instituting early therapy would improve neurologic outcome. METHODS: The Trauma Registry of the author's Level I Trauma Center identified patients with BCI from 1990 through 1997. Beginning in August 1996, the authors implemented a screening for BCI. Arteriography was used for diagnosis. Patients without specific contraindications were anticoagulated. Endovascular stents were deployed in the setting of pseudoaneurysms. RESULTS: Thirty-seven patients with BCI were identified among 15,331 blunt-trauma victims (0.24%). During the screening period, 25 patients were diagnosed with BCI among 2902 admissions (0.86%); 13 (52%) were asymptomatic. Overall, eight patients died, and seven of the survivors had permanent severe neurologic deficits. Excluding those dying of massive brain injury and patients admitted with coma and brain injury, mortality associated with BCI was 15%, with severe neurologic morbidity in 16% of survivors. The patients who were asymptomatic at diagnosis had a better neurologic outcome than those who were symptomatic. Symptomatic patients who were anticoagulated showed a trend toward greater neurologic improvement at the time of discharge than those who were not anticoagulated. CONCLUSIONS: Screening allows the identification of asymptomatic BCI and thereby facilitates early systemic anticoagulation, which is associated with improved neurologic outcome. The role of endovascular stents in the treatment of blunt traumatic pseudoaneurysms remains to be defined.  相似文献   
50.
The purpose of this study was to investigate the primary operative procedures that are performed by hand surgeons for cubital tunnel syndrome and their reported satisfaction with these procedures. The survey consisted of 22 questions regarding primary operative treatment of cubital tunnel syndrome and demographics and was sent by email to the 459 active members of the American Association for Hand Surgery. One hundred sixty-four surgeons completed the survey (36% response rate). The total sample included 154 hand surgeons (143 males, 11 females) who operated on cubital tunnel syndrome and the majority of surgeons were in private practice (n = 100) followed by academic practice (n = 50). The most prevalent factors that influence the decision to operate include evidence of muscle atrophy (84%), abnormal nerve conduction studies (51%), and failed non-operative treatment (49%). Most surgeons (n = 133) reported using more than one operative procedure for their patients with cubital tunnel syndrome. Factors that influenced the operative procedure selected included the degree of nerve compression (60%), medical comorbidities (30%), patient's occupation (28%), and obesity (22%). Following carpal tunnel surgery, 88% of the surgeons were "very satisfied" with their patient outcome and following surgery for cubital tunnel syndrome, only 44% were "very satisfied" with their patient outcome. Most surgeons use more than one operative procedure in their treatment of patients with cubital tunnel syndrome and the selection of the operative procedure is influenced by patient factors and surgeon preference.  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