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   3897640篇
  免费   298282篇
  国内免费   6660篇
耳鼻咽喉   56378篇
儿科学   124080篇
妇产科学   105489篇
基础医学   560212篇
口腔科学   112218篇
临床医学   358605篇
内科学   742612篇
皮肤病学   83343篇
神经病学   316790篇
特种医学   151104篇
外国民族医学   1277篇
外科学   588412篇
综合类   89278篇
现状与发展   13篇
一般理论   1601篇
预防医学   314632篇
眼科学   93493篇
药学   293091篇
  12篇
中国医学   7310篇
肿瘤学   202632篇
  2018年   42141篇
  2017年   31978篇
  2016年   35675篇
  2015年   40297篇
  2014年   57639篇
  2013年   87687篇
  2012年   119238篇
  2011年   126770篇
  2010年   75401篇
  2009年   71368篇
  2008年   119350篇
  2007年   127165篇
  2006年   128373篇
  2005年   124772篇
  2004年   119976篇
  2003年   115225篇
  2002年   112838篇
  2001年   174699篇
  2000年   180003篇
  1999年   151653篇
  1998年   42782篇
  1997年   37568篇
  1996年   37151篇
  1995年   38045篇
  1994年   35502篇
  1993年   33321篇
  1992年   121343篇
  1991年   118550篇
  1990年   115178篇
  1989年   110949篇
  1988年   102796篇
  1987年   100972篇
  1986年   95334篇
  1985年   91617篇
  1984年   69096篇
  1983年   58887篇
  1982年   35611篇
  1981年   31841篇
  1979年   64803篇
  1978年   45934篇
  1977年   38474篇
  1976年   36719篇
  1975年   38956篇
  1974年   47544篇
  1973年   45290篇
  1972年   42827篇
  1971年   40077篇
  1970年   37295篇
  1969年   35097篇
  1968年   32243篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
The Dutch Drug Rediscovery Protocol (DRUP) and the Australian Cancer Molecular Screening and Therapeutic (MoST) Program are similar nonrandomized, multidrug, pan-cancer trial platforms that aim to identify signals of clinical activity of molecularly matched targeted therapies or immunotherapies outside their approved indications. Here, we report results for advanced or metastatic cancer patients with tumors harboring cyclin D-CDK4/6 pathway alterations treated with CDK4/6 inhibitors palbociclib or ribociclib. We included adult patients that had therapy-refractory solid malignancies with the following alterations: amplifications of CDK4, CDK6, CCND1, CCND2 or CCND3, or complete loss of CDKN2A or SMARCA4. Within MoST, all patients were treated with palbociclib, whereas in DRUP, palbociclib and ribociclib were assigned to different cohorts (defined by tumor type and alteration). The primary endpoint for this combined analysis was clinical benefit, defined as confirmed objective response or stable disease ≥16 weeks. We treated 139 patients with a broad variety of tumor types; 116 with palbociclib and 23 with ribociclib. In 112 evaluable patients, the objective response rate was 0% and clinical benefit rate at 16 weeks was 15%. Median progression-free survival was 4 months (95% CI: 3-5 months), and median overall survival 5 months (95% CI: 4-6 months). In conclusion, only limited clinical activity of palbociclib and ribociclib monotherapy in patients with pretreated cancers harboring cyclin D-CDK4/6 pathway alterations was observed. Our findings indicate that monotherapy use of palbociclib or ribociclib is not recommended and that merging data of two similar precision oncology trials is feasible.  相似文献   
82.
The mechanisms linking tumor microenvironment acidosis to disease progression are not understood. Here, we used mammary, pancreatic, and colon cancer cells to show that adaptation to growth at an extracellular pH (pHe) mimicking acidic tumor niches is associated with upregulated net acid extrusion capacity and elevated intracellular pH at physiological pHe, but not at acidic pHe. Using metabolic profiling, shotgun lipidomics, imaging and biochemical analyses, we show that the acid adaptation-induced phenotype is characterized by a shift toward oxidative metabolism, increased lipid droplet-, triacylglycerol-, peroxisome content and mitochondrial hyperfusion. Peroxisome proliferator-activated receptor-α (PPARA, PPARα) expression and activity are upregulated, at least in part by increased fatty acid uptake. PPARα upregulates genes driving increased mitochondrial and peroxisomal mass and β-oxidation capacity, including mitochondrial lipid import proteins CPT1A, CPT2 and SLC25A20, electron transport chain components, peroxisomal proteins PEX11A and ACOX1, and thioredoxin-interacting protein (TXNIP), a negative regulator of glycolysis. This endows acid-adapted cancer cells with increased capacity for utilizing fatty acids for metabolic needs, while limiting glycolysis. As a consequence, the acid-adapted cells exhibit increased sensitivity to PPARα inhibition. We conclude that PPARα is a key upstream regulator of metabolic changes favoring cancer cell survival in acidic tumor niches.  相似文献   
83.
Evidence suggests that aspirin use reduces the occurrence of colorectal neoplasia. Few studies have investigated the association among Black Americans, who are disproportionately burdened by the disease. We assessed aspirin use in relation to colorectal adenoma among Black women. The Black Women's Health Study is a prospective cohort of self-identified Black American women established in 1995. Participants reported regular aspirin use on baseline and follow-up questionnaires. Beginning in 1999, participants reported undergoing a colonoscopy or sigmoidoscopy, the only procedures through which colorectal adenomas can be diagnosed. Multivariable logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) for associations between aspirin use and colorectal adenoma among 34 397 women who reported at least 1 colonoscopy or sigmoidoscopy. From 1997 through 2018, 1913 women were diagnosed with an adenoma. Compared to nonaspirin users, regular users had 14% (OR = 0.86, 95% CI: 0.78-0.95) lower odds of adenoma. The odds of adenoma decreased with increasing duration of aspirin use (≥10 years: OR = 0.80, 95% CI: 0.66-0.96). Initiating aspirin at a younger age was associated with a reduced adenoma occurrence (age < 40 years at initiation: OR = 0.69, 95% CI: 0.55-0.86). Regular aspirin use was associated with a decreased odds of colorectal adenoma in our study of Black women. These findings support evidence demonstrating a chemopreventive impact of aspirin on colorectal neoplasia and suggest that aspirin may be a useful prevention strategy among US Black women.  相似文献   
84.

Objective

Explore the perceived benefits of a Veterans Health Administration (VHA) geriatric specialty telemedicine service (GRECC Connect) among rural, older patients and caregivers to contribute to an assessment of its quality and value.

Data Sources

In Spring 2021, we interviewed a geographically diverse sample of rural, older patients and their caregivers who participated in GRECC Connect telemedicine visits.

Study Design

A cross-sectional qualitative study focused on patient and caregiver experiences with telemedicine, including perceived benefits and challenges.

Data Collection

We conducted 30 semi-structured qualitative interviews with rural, older (≥65) patients enrolled in the VHA and their caregivers via videoconference or phone. Interviews were recorded, transcribed, and analyzed using a rapid qualitative analysis approach.

Principal Findings

Participants described geriatric specialty telemedicine visits focused on cognitive assessments, tailored physical therapy, medication management, education on disease progression, support for managing multiple comorbidities, and suggestions to improve physical functioning. Participants reported that, in addition to prescribing medications and ordering tests, clinicians expedited referrals, coordinated care, and listened to and validated both patient and caregiver concerns. Perceived benefits included improved patient health; increased patient and caregiver understanding and confidence around symptom management; and greater feelings of empowerment, hopefulness, and support. Challenges included difficulty accessing some recommended programs and services, uncertainty related to instructions or follow-up, and not receiving as much information or treatment as desired. The content of visits was well aligned with the domains of the Age-Friendly Health Systems and Geriatric 5Ms frameworks (Medication, Mentation, Mobility, what Matters most, and Multi-complexity).

Conclusions

Alignment of patient and caregiver experiences with widely-used models of comprehensive geriatric care indicates that high-quality geriatric care can be provided through virtual modalities. Additional work is needed to develop strategies to address challenges and optimize and expand access to geriatric specialty telemedicine.  相似文献   
85.
86.
87.
Graefe's Archive for Clinical and Experimental Ophthalmology - To describe and present results after a technique for cataract surgery combined with explantation of an iris-fixated phakic...  相似文献   
88.
Base catalysed exchange with sodium hydroxide, calcium oxide or N,N,N,N-tetramethylguanidine in deuterium oxide is a viable procedure for the preparation of terminally deuterated alkynes for those alkynes stable to strong base. The use of silver perchlorate as a catalyst is an alternative practical option when labelling alkynes which are sensitive to base or contain functionalities which would lead to labelling elsewhere in the molecule. Labelling with this catalyst takes place smoothly at ambient temperature in a mixture of N,N-dimethylformamide and deuterium oxide.  相似文献   
89.
90.
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