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   1269779篇
  免费   99753篇
  国内免费   1980篇
耳鼻咽喉   18405篇
儿科学   44239篇
妇产科学   34996篇
基础医学   180913篇
口腔科学   33560篇
临床医学   110612篇
内科学   256151篇
皮肤病学   28004篇
神经病学   99708篇
特种医学   51164篇
外国民族医学   660篇
外科学   195736篇
综合类   27022篇
现状与发展   1篇
一般理论   377篇
预防医学   95138篇
眼科学   27794篇
药学   94521篇
  2篇
中国医学   2336篇
肿瘤学   70173篇
  2018年   13125篇
  2017年   9961篇
  2016年   10896篇
  2015年   12372篇
  2014年   17162篇
  2013年   26209篇
  2012年   36016篇
  2011年   38053篇
  2010年   22798篇
  2009年   21807篇
  2008年   36634篇
  2007年   39243篇
  2006年   39500篇
  2005年   38437篇
  2004年   37589篇
  2003年   36388篇
  2002年   35702篇
  2001年   63889篇
  2000年   66320篇
  1999年   56060篇
  1998年   14355篇
  1997年   12987篇
  1996年   13405篇
  1995年   13383篇
  1994年   12718篇
  1993年   11725篇
  1992年   44501篇
  1991年   43454篇
  1990年   42205篇
  1989年   40089篇
  1988年   36865篇
  1987年   36218篇
  1986年   33591篇
  1985年   32263篇
  1984年   24118篇
  1983年   20215篇
  1982年   11682篇
  1981年   10638篇
  1980年   9459篇
  1979年   21299篇
  1978年   14785篇
  1977年   12489篇
  1976年   11667篇
  1975年   12600篇
  1974年   14643篇
  1973年   14101篇
  1972年   12938篇
  1971年   11714篇
  1970年   11039篇
  1969年   10012篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
61.
An unprecedented mortality crisis befell the former socialist countries between 1989 and 1995, representing one of the greatest demographic shocks of the period after the Second World War. While it is likely that country‐level variation in the post‐socialist mortality crisis in Eastern Europe can be explained by a constellation of political and socio‐economic factors, no comprehensive review of the existing scholarly attempts at explaining these factors exists. We review 39 cross‐national multi‐variable peer reviewed studies of social determinants of mortality in post‐socialist Europe in order to assess the social factors behind the post‐socialist mortality crisis, determine the gaps in the existing literature and to make suggestions for future research. We propose a novel methodology to determine the relative importance of variables based on the ratio of significant to insignificant findings for each variable. The literature identifies inequality, welfare payments, religious composition, democracy, economic performance and unemployment as the leading factors that have a significant influence on mortality outcomes. Existing cross‐country studies fail to establish a definitive connection between mortality and diets, drinking patterns, liberalisation, trust, health expenditure and war. We also point out that the level of analysis is not a neutral methodological choice but might influence the results themselves.  相似文献   
62.
Journal of Neuro-Oncology - Primary central nervous system lymphoma (PCNSL) is a subtype of non-Hodgkin’s lymphoma that involves the brain, spinal cord, or leptomeninges, without evidence of...  相似文献   
63.
The aim of the study is to investigate the influence of patient characteristics, age and body mass index (BMI), on pharmacokinetics of enzalutamide, and to study the relationships between drug exposure and enzalutamide efficacy and toxicity, in mCRPC patients. Data were collected in a longitudinal cohort study (ANDROPS) and a prospective observational study (ILUMINATE), both in mCRPC patients treated with enzalutamide. To investigate the influence of age and BMI on exposure, enzalutamide and N-desmethylenzalutamide levels were compared by ANOVA. To investigate the relation of exposure versus time to progression (TTP), the sum plasma levels were divided into quartiles and compared by Kaplan–Meier analysis. To assess the relation of exposure with fatigue, plasma levels in patients experiencing fatigue vs. no fatigue were compared by and independent t test. Data of 68 mCRPC patients were included for analysis. Plasma levels were not different for age or BMI. No difference in TTP between both studies was observed (383 days (95% CI 287–859), and 567 days (95% CI 351–NR), p = 0.36). Kaplan–Meier analysis of quartiles of sum levels showed no difference for TTP. Fatigue was reported by 22 patients, no difference in sum plasma levels was observed between patients with and without fatigue. We observed that age and BMI did not influence systemic exposure in patients treated with enzalutamide. No relation of exposure with efficacy or fatigue was observed. Further research using enzalutamide at a lower dose is needed to understand the relation of enzalutamide exposure and fatigue.  相似文献   
64.
Brain metastases are the most prevalent intracranial malignancy. Patient outcome is poor and treatment options are limited. Hence, new avenues must be explored to identify potential therapeutic targets. Inflammation is a known critical component of cancer progression. Intratumoral inflammation drives progression and leads to the release of circulating tumor cells (CTCs). Inflammation at distant sites promotes adhesion of CTCs to the activated endothelium and then initiates the formation of metastases. These interactions mostly involve cell adhesion molecules expressed by activated endothelial cells. For example, the vascular cell adhesion molecule-1 (VCAM-1) is known to promote transendothelial migration of cancer cells in different organs. However, it is unclear whether a similar mechanism occurs within the specialized environment of the brain. Our objective was therefore to use molecular imaging to assess the potential role of VCAM-1 in promoting the entry of CTCs into the brain. First, magnetic resonance imaging (MRI) and histological analyses revealed that cerebrovascular inflammation induced by intracranial injection of lipopolysaccharide significantly increased the expression of VCAM-1 in the Balb/c mouse brain. Next, intracardiac injection of 4T1 mammary carcinoma cancer cells in animals with cerebrovascular inflammation yielded a higher brain metastasis burden than in the control animals. Finally, blocking VCAM-1 prior to 4T1 cells injection prevented this increased metastatic burden. Here, we demonstrated that by contributing to CTCs adhesion to the activated cerebrovascular endothelium, VCAM-1 improves the capacity of CTCs to form metastatic foci in the brain.  相似文献   
65.
Obesity is a risk factor for colorectal cancer. Yet, some research indicates that weight-reducing bariatric surgery also increases colorectal cancer risk. Our study was undertaken because current evidence examining bariatric surgery and risk of colorectal cancer is limited and inconsistent. This population-based cohort study included adults with a documented obesity diagnosis in Denmark, Finland, Iceland, Norway or Sweden in 1980–2015. The incidence of colorectal cancer in participants with obesity who had and had not undergone bariatric surgery was compared to the incidence in the corresponding background population by calculating standardized incidence ratios (SIR) with 95% confidence intervals (CI). Additionally, operated and nonoperated participants with obesity were compared using multivariable Cox regression, providing hazard ratios (HR) with 95% CIs adjusted for confounders. Among 502,772 cohort participants with an obesity diagnosis, 49,931(9.9%) underwent bariatric surgery. The overall SIR of colon cancer was increased after bariatric surgery (SIR 1.56; 95% CI 1.28–1.88), with higher SIRs ≥10 years postsurgery. The overall HR of colon cancer in operated compared to nonoperated participants was 1.13 (95% CI 0.92–1.39) and 1.55 (95% CI 1.04–2.31) 10–14 years after bariatric surgery. Bariatric surgery did not significantly increase the risk of rectal cancer (SIR 1.14, 95% CI 0.83–1.52; HR 1.08, 95% CI 0.79–1.49), but the risk estimates increased with longer follow-up periods. Our study suggests that bariatric surgery is associated with an increased risk of colon cancer, while the support for an increased risk of rectal cancer was weaker.  相似文献   
66.
67.
68.
Patients with melanoma brain metastases (MBM) still have a very poor prognosis. Several treatment modalities have been investigated in an attempt to improve the management of MBM. This review aimed to evaluate the impact of current treatments for MBM on patient- and tumor-related outcomes, and to provide treatment recommendations for this patient population. A literature search in the databases PubMed, Embase, Web of Science and Cochrane was conducted up to January 8, 2019. Original articles published since 2010 describing patient- and tumor-related outcomes of adult MBM patients treated with clearly defined systemic therapy were included. Information on basic trial demographics, treatment under investigation and outcomes (overall and progression-free survival, local and distant control and toxicity) were extracted. We identified 96 eligible articles, comprising 95 studies. A large variety of treatment options for MBM were investigated, either used alone or as combined modality therapy. Combined modality therapy was investigated in 71% of the studies and resulted in increased survival and better distant/local control than monotherapy, especially with targeted therapy or immunotherapy. However, neurotoxic side-effects also occurred more frequently. Timing appeared to be an important determinant, with the best results when radiotherapy was given before or during systemic therapy. Improved tumor control and prolonged survival can be achieved by combining radiotherapy with immunotherapy or targeted therapy. However, more randomized controlled trials or prospective studies are warranted to generate proper evidence that can be used to change the standard of care for patients with MBM.  相似文献   
69.
70.
Willeke  V. M.  Anderson  M. P.  Mahadevan  A.  Rojas  R.  Bhadelia  R.  Thomas  A. J.  Kasper  E. M. 《Journal of neuro-oncology》2020,147(2):247-260
Purpose

Epstein Barr virus (EBV)-associated smooth muscle tumors (SMT) in the central nervous system are rare tumors. EBV-associated SMT mainly occur in patient with compromised immune status. We report on a case of a HIV positive patient, who developed multiple EBV-SMTs, intracranially and in the spine. We systematically review the literature on the topic.

Case report

A 46 years old female with HIV was imaged for complaints of headaches for 2 years, when an intracranial lesion was found. The patient was followed with sequential MRI scans before an excision was performed 5 years later. Pathology revealed an EBV-associated SMT. Multiple other lesions appearing in the brain and in the spine over years were treated by stereotactic radiosurgery or by surgery. At the time of this report, the patient is alive under HARRT treatment without recurrence.

Methods

A systematic PRISMA guided literature research was conducted on the topic reviewing multiple databases for EBV-associated SMT located in brain or spine. We identified 52 patients from the literature and performed a pooled analysis.

Results

All patients in this cohort except one were immuno-suppressed from HIV, post-transplant therapy or because of CIS. Female predominance and a median age of 35 years was identified as was frequent multifocality. Therapeutic strategies varied but were mostly multidisciplinary with surgery.

Conclusion

Based on our results, EBV-associated SMT should be included in the differential diagnosis of intracranial lesions mimicking meningiomas in immuno-suppressed patients. Stereotactic radiosurgery can be offered as an alternate treatment option for suitable lesions. Long-term surveillance via MRI scanning is recommended for follow up.

  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