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   211173篇
  免费   17210篇
  国内免费   6377篇
耳鼻咽喉   1584篇
儿科学   3336篇
妇产科学   2559篇
基础医学   28197篇
口腔科学   3421篇
临床医学   21312篇
内科学   23617篇
皮肤病学   1799篇
神经病学   8199篇
特种医学   7094篇
外国民族医学   49篇
外科学   23552篇
综合类   32981篇
现状与发展   14篇
一般理论   25篇
预防医学   13347篇
眼科学   4457篇
药学   20487篇
  46篇
中国医学   9428篇
肿瘤学   29256篇
  2024年   430篇
  2023年   2488篇
  2022年   5538篇
  2021年   7512篇
  2020年   6729篇
  2019年   6556篇
  2018年   6642篇
  2017年   6588篇
  2016年   6918篇
  2015年   7050篇
  2014年   11779篇
  2013年   12395篇
  2012年   10739篇
  2011年   12311篇
  2010年   10383篇
  2009年   10564篇
  2008年   10791篇
  2007年   11756篇
  2006年   10683篇
  2005年   10108篇
  2004年   8874篇
  2003年   7792篇
  2002年   6023篇
  2001年   5835篇
  2000年   4807篇
  1999年   4296篇
  1998年   3213篇
  1997年   2848篇
  1996年   2789篇
  1995年   2615篇
  1994年   2337篇
  1993年   2024篇
  1992年   1727篇
  1991年   1497篇
  1990年   1224篇
  1989年   1156篇
  1988年   1056篇
  1987年   841篇
  1986年   623篇
  1985年   763篇
  1984年   724篇
  1983年   458篇
  1982年   587篇
  1981年   497篇
  1980年   431篇
  1979年   348篇
  1978年   284篇
  1977年   223篇
  1976年   250篇
  1975年   159篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Two cultivars of Japanese parsley were harvested in different seasons; their antioxidant capacities were evaluated by oxygen radical absorbance capacity (ORAC) methods, and the contents of hydrophilic and lipophilic antioxidants were compared. Japanese parsley possessed potent antioxidant capacities both in hydrophilic and lipophilic extracts when evaluated by ORAC methods. LC/MS/MS analyses revealed that chlorogenic acid and four kinds of quercetin glycosides were major antioxidants in the hydrophilic extract. Lutein was the main contributor to the antioxidant capacity of the lipophilic extract. Antioxidant capacities of the hydrophilic extracts of both cultivars tended to be higher in winter because of the increase in the contents of chlorogenic acid and quercetin glycosides. An obvious trend in the lipophilic antioxidant capacities or lutein contents was not observed irrespective of the cultivar.  相似文献   
52.
HER2-positive (HER2+) breast cancer (BC) is a heterogenous and multifaceted disease, with interesting therapeutic implications. First, all intrinsic molecular subtypes can be identified in HER2+ tumors, with the HER2-enriched being the most frequent. Such subtypes do not differ much from their counterparts in HER2-negative disease, apart for the high expression of genes in/near the HER2 amplicon on chromosome 17. Intrinsic subtyping, along with the quantification of ERBB2 mRNA levels, is associated with higher rates of pathologic complete response across neoadjuvant trials of dual HER2 blockade and might help select patients for de-escalation and escalation treatment strategies. Secondly, HER2+ tumors have a broad range of DNA alterations. ERBB2 mutations and alterations in the PI3K/Akt/mTOR pathway are among the most frequent and might predict benefit from potent pan-HER, PI3K and mTOR inhibitors. Moreover, HER2+ tumors are usually infiltrated by lymphocytes. These tumor infiltrating-lymphocytes (TILs) predict response to neoadjuvant anti-HER2-based treatment and exert a prognostic role. PD-L1, detected in ∼42 % of HER2+ BC, might also be useful to define patients responding to novel anti-PD1/PD-L1 immunotherapies. New multiparametric clinicopathologic and genomic tools accounting for this complexity, such as HER2DX, are under development to define more tailored treatment approaches. Finally, HER2-targeted antibody-drug conjugates (ADC) such as trastuzumab deruxtecan might be active in tumors with low expression of HER2. Overall, there is a need to molecularly characterize and develop novel targeted therapies for HER2+ disease.  相似文献   
53.

Background

Despite significant pain relief following total hip arthroplasty (THA) in patients with ankylosing spondylitis, a small subset of patients presenting with extra-articular extension contracture of hips remains unsatisfied.

Methods

We retrospectively evaluated the patients with ankylosing spondylitis who underwent simultaneous bilateral THA and had extensor tightness of both hips preoperatively. They were managed with modified Z-plasty of iliotibial band. Patients with windswept deformity, commonly seen in bilateral hip arthritis caused by ankylosing spondylitis, were excluded.

Results

Between July 2011 and June 2015, out of 148 patients with bilateral hip involvement, 10 patients (20 hips) had extension contracture of both hips that was addressed during surgery. All patients were followed up for a minimum of 2 years. They could sit comfortably on a chair of height 18 inches with hips and knees flexed to at least 90°. The mean postoperative sum range of motion was 144.6° with an average hip flexion of 95° (range, 90°-105°). None of them had recurrence of extension contracture. There was significant improvement in range of motion and hence ambulation and function. No radiolucent lines exceeding 2 mm were seen in any of the zones around either of the components as evaluated in latest X-rays.

Conclusion

Extension contracture of hip although rare is a noticeable problem and needs to be addressed during THA. Modified Z-plasty technique of iliotibial band is a reliable method in managing these patients.  相似文献   
54.
Purpose: Mouse double-stranded DNA-dependent protein kinase (DNA-PK) activity is heat sensitive. Recovery of heat-inactivated DNA repair activity is a problem after combination therapy with radiation and heat. We investigated the mechanism of recovery of heat-inactivated DNA-PK activity.

Methods: Hybrid cells containing a fragment of human chromosome 8 in scid cells (RD13B2) were used. DNA-PK activity was measured by an in vitro assay. Immunoprecipitation of the nuclear extract was performed with an anti-Ku80 antibody. Proteins co-precipitated with Ku80 were separated by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis and detected by Western blotting using anti-heat shock protein (HSP)72 and anti-heat shock cognate protein (HSC)73 antibodies. HSC73 was overexpressed with the pcDNA3.1 vector. Short hairpin (sh)RNA was used to downregulate HSC73 and HSP72.

Results: The activity of heat-inactivated DNA-PK recovered to about 50% of control during an additional incubation at 37?°C after heat treatment at 44?°C for 15?min in the presence of cycloheximide (which inhibits de novo protein synthesis). Maximal recovery was observed within 3?h of incubation at 37?°C after heat treatment. Constitutively expressed HSC73, which folds newly synthesized proteins, reached maximal levels 3?h after heat treatment using a co-immunoprecipitation assay with the Ku80 protein. Inhibiting HSC73, but not HSP72, expression with shRNA decreased the recovery of DNA-PK activity after heat treatment.

Conclusions: These results suggest that de novo protein synthesis is unnecessary for recovery of some heat-inactivated DNA-PK. Rather, it might be reactivated by the molecular chaperone activity of HSC73, but not HSP72.  相似文献   

55.
To provide policy recommendations for managing Coronavirus 19 (COVID-19) in skilled nursing facilities, a group of certified medical directors from several facilities in New York state with experience managing the disease used e-mail, phone, and video conferencing to develop consensus recommendations. The resulting document provides recommendations on screening, protection of staff, screening of residents, management of Coronavirus 19 positive and presumed positive cases, communication during an outbreak, management of admissions and readmissions, and providing emotional support for staff. These consensus guidelines have been endorsed by the Executive Board of the New York Medical Directors Association and the Board of the Metropolitan Area Geriatrics Society.  相似文献   
56.
目的:探讨老年人桡骨远端C型骨折的手术治疗与非手术治疗的疗效差异,评价两种方法的优缺点。方法回顾性分析2009-12—2011-12收治的老年桡骨远端C型骨折68例,按照治疗方法分为A组(手术组)及B组(非手术组),统计分析两组患者的临床资料。结果 A组33例, B组35例,平均随访21.5个月。两组患者的年龄、骨折类型均无差异(P>0.05);术后影像学指标A组优于B组,骨折愈合时间B组优于A组,治疗成本A组大于B组(P<0.05);Cooney评分早期A组优于B组,1年后两组无差异,两组的并发症无差异(P>0.05)。结论老年人桡骨远端C型骨折手术治疗较非手术治疗可获得更好的复位及早期功能,但远期功能恢复无差异。  相似文献   
57.
The chemical composition, structure and surface characteristics of biomaterials/scaffold can affect the adsorption of proteins, and this in turn influences the subsequent cellular response and tissue regeneration. With magnesium/calcium phosphate cements (MCPC) as model, the effects of magnesium (Mg) on the initial adhesion and osteogenic differentiation of bone marrow stromal cells (BMSCs) as well as the underlying mechanism were investigated. A series of MCPCs with different magnesium phosphate cement (MPC) content (0∼20%) in calcium phosphate cement (CPC) were synthesized. MCPCs with moderate proportion of MPC (5% and 10%, referred to as 5MCPC and 10MCPC) were found to effectively modulate the orientation of the adsorbed fibronectin (Fn) to exhibit enhanced receptor binding affinity, and to up-regulate integrin α5β1 expression of BMSCs, especially for 5MCPC. As a result, the attachment, morphology, focal adhesion formation, actin filaments assembly and osteogenic differentiation of BMSCs on 5MCPC were strongly enhanced. Further in vivo experiments confirmed that 5MCPC induced promoted osteogenesis in comparison to ot her CPC/MCPCs. Our results also suggested that the Mg on the underlying substrates but not the dissolved Mg ions was the main contributor to the above positive effects. Based on these results, it can be inferred that the specific interaction of Fn and integrin α5β1 had predominant effect on the MCPC-induced enhanced cellular response of BMSCs. These results provide a new strategy to regulate BMSCs adhesion and osteogenic differentiation by adjusting the Mg/Ca content and distribution in CPC, guiding the development of osteoinductive scaffolds for bone tissue regeneration.  相似文献   
58.
Classical Kaposi sarcoma (KS) usually appears on lower extremities accompanied or preceded by local lymphedema. However, the development in areas of chronic lymphedema of the arms following mastectomy, mimicking a Stewart–Treves syndrome, has rarely been described. We report an 81‐year‐old woman who developed multiple, erythematous to purple tumors, located on areas of post mastectomy lymphedema. Histopathological examination evidenced several dermal nodules formed by spindle‐shaped cells that delimitated slit‐like vascular spaces with some red cell extravasation. Immunohistochemically, the human herpesvirus type 8 (HHV‐8) latent nuclear antigen‐1 was detected in the nuclei of most tumoral cells confirming the diagnosis of KS. Lymphedema could promote the development of certain tumors by altering immunocompetence. Although angiosarcoma (AS) is the most frequent neoplasia arising in the setting of chronic lymphedema, other tumors such as benign lymphangiomatous papules (BLAP) or KS can also develop in lymphedematous limbs. It is important to establish the difference between AS and KS because their prognosis and treatment are very different. Identification by immunohistochemistry of HHV‐8 is useful for the distinction between KS and AS or BLAP.  相似文献   
59.
Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare congenital condition. It responds well to early diagnosis and treatment, but otherwise the prognosis is poor. We present our case series of 12 patients (mean age, 2 ± 2.58 yr; age range, 2 mo–8 yr), emphasizing the diagnostic process and discussing our surgical results. The diagnosis of ALCAPA should be suspected in infants who have dilated cardiomyopathy with electrocardiographic changes that suggest ischemia, and in older children who have isolated mitral regurgitation. When clinical suspicion is high, the results of 2-dimensional echocardiography combined with color-flow Doppler studies in expert hands can establish the diagnosis, thus avoiding angiography in critically ill infants. The treatment of choice in our patients was transfer and reimplantation of the left coronary artery onto the ascending aorta. There were 2 deaths: both were infants in extremis who underwent emergency surgery. An older child with severe ventricular dysfunction was given mechanical ventricular assistance and then heart transplantation. As of this report, all 10 survivors remained well and asymptomatic.  相似文献   
60.
目的:研究全麻复合硬膜外在高龄患者腹腔镜直肠癌根治术中的应用效果。方法:选择60岁以上择期行腹腔镜直肠癌根治术患者60例,随机分为G组和GA组,每组各30例。G组患者为单纯全麻组,GA组患者为硬膜外复合全麻组。GA组患者在诱导前取L1~2硬膜外穿刺置管,予0.5%罗哌卡因5 ml,术中每小时追加5~7 ml。两组患者诱导方法相同:即,咪哒唑仑0.04 mg/kg、舒芬太尼0.3~0.4μg/kg、顺阿曲库铵0.15~0.20 mg/kg、依托咪酯0.2~0.3 mg/kg。监测并记录患者血压(BP),心率(HR),心电图(ECG),术中全麻药用量及术后患者苏醒情况。结果:GA组患者气腹后、拔管前BP、HR明显低于G组(P<0.05),且全麻药用量明显低于G组(P<0.05)。结论:全麻复合硬膜外应用于老年腹腔镜直肠癌手术较单纯全麻用药量减少,术中循环更加稳定,是腹腔镜直肠癌根治术比较安全可行的麻醉方法。  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