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   33229篇
  免费   2513篇
  国内免费   465篇
耳鼻咽喉   689篇
儿科学   561篇
妇产科学   697篇
基础医学   4616篇
口腔科学   514篇
临床医学   2720篇
内科学   7430篇
皮肤病学   970篇
神经病学   2393篇
特种医学   1733篇
外科学   4600篇
综合类   553篇
现状与发展   1篇
一般理论   19篇
预防医学   1408篇
眼科学   1003篇
药学   2879篇
中国医学   370篇
肿瘤学   3051篇
  2023年   198篇
  2022年   138篇
  2021年   913篇
  2020年   561篇
  2019年   898篇
  2018年   1063篇
  2017年   756篇
  2016年   961篇
  2015年   1329篇
  2014年   1563篇
  2013年   1800篇
  2012年   2610篇
  2011年   2705篇
  2010年   1632篇
  2009年   1398篇
  2008年   1995篇
  2007年   1918篇
  2006年   1722篇
  2005年   1653篇
  2004年   1375篇
  2003年   1347篇
  2002年   1200篇
  2001年   768篇
  2000年   699篇
  1999年   654篇
  1998年   233篇
  1997年   216篇
  1996年   189篇
  1995年   189篇
  1994年   162篇
  1993年   106篇
  1992年   329篇
  1991年   238篇
  1990年   278篇
  1989年   265篇
  1988年   253篇
  1987年   213篇
  1986年   195篇
  1985年   172篇
  1984年   148篇
  1983年   120篇
  1982年   86篇
  1981年   80篇
  1980年   77篇
  1979年   134篇
  1978年   91篇
  1977年   71篇
  1975年   63篇
  1974年   56篇
  1972年   53篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Interval breast cancers (those diagnosed between recommended mammography screens) generally have poorer outcomes and are more common among women with dense breasts. We aimed to develop a risk model for interval breast cancer. We conducted a nested case–control study within the Melbourne Collaborative Cohort Study involving 168 interval breast cancer patients and 498 matched control subjects. We measured breast density using the CUMULUS software. We recorded first-degree family history by questionnaire, measured body mass index (BMI) and calculated age-adjusted breast tissue aging, a novel measure of exposure to estrogen and progesterone based on the Pike model. We fitted conditional logistic regression to estimate odds ratio (OR) or odds ratio per adjusted standard deviation (OPERA) and calculated the area under the receiver operating characteristic curve (AUC). The stronger risk associations were for unadjusted percent breast density (OPERA = 1.99; AUC = 0.66), more so after adjusting for age and BMI (OPERA = 2.26; AUC = 0.70), and for family history (OR = 2.70; AUC = 0.56). When the latter two factors and their multiplicative interactions with age-adjusted breast tissue aging (p = 0.01 and 0.02, respectively) were fitted, the AUC was 0.73 (95% CI 0.69–0.77), equivalent to a ninefold interquartile risk ratio. In summary, compared with using dense breasts alone, risk discrimination for interval breast cancers could be doubled by instead using breast density, BMI, family history and hormonal exposure. This would also give women with dense breasts, and their physicians, more information about the major consequence of having dense breasts—an increased risk of developing an interval breast cancer.  相似文献   
73.
Stereotactic body radiotherapy has emerged as one of the preferred treatments for patients with spine metastases, with the potential for long‐term control from lesion irradiation. Post‐treatment vertebral compression fractures are a known complication of this therapy, contributing to worsening pain and reduced quality of life, sometimes requiring surgical intervention. This review explores the current knowledge of post‐radiotherapy fractures, in terms of the rates and associated predictive factors. A search of databases including Medline, Embase and the Cochrane Library was conducted using keywords such as ‘vertebral compression fracture’, ‘stereotactic body radiotherapy’ and ‘spine metastases’. The search was limited to published studies up to March 2019, reporting clinical outcomes including both the post‐treatment fracture rate and statistical identification of associated risk factors. Rates of post‐treatment fractures ranged from 4 to 39%. A variety of factors were found to increase the risk, including the appearance of lytic vertebral disease, degree of pre‐existing compression, spinal malalignment, increased dose per fraction and a Spinal Instability Neoplastic Score >6. This knowledge can enable clinicians to counsel patients when considering management options for spine metastases, maintaining the balance between local tumour control and the risk of subsequent fracture.  相似文献   
74.
ABSTRACT

Wildland fires (WF) are linked to adverse health impacts related to poor air quality. The cardiovascular impacts of emissions from specific biomass sources are however unknown. The purpose of this study was to assess the cardiovascular impacts of a single exposure to peat smoke, a key regional WF air pollution source, and relate these to baroreceptor sensitivity and inflammation. Three-month-old male Wistar-Kyoto rats, implanted with radiotelemeters for continuous monitoring of heart rate (HR), blood pressure (BP), and spontaneous baroreflex sensitivity (BRS), were exposed once, for 1-hr, to filtered air or low (0.38 mg/m3 PM) or high (4.04 mg/m3) concentrations of peat smoke. Systemic markers of inflammation and sensitivity to aconitine-induced cardiac arrhythmias, a measure of latent myocardial vulnerability, were assessed in separate cohorts of rats 24 hr after exposure. PM size (low peat = 0.4–0.5 microns vs. high peat = 0.8–1.2 microns) and proportion of organic carbon (low peat = 77% vs. high peat = 65%) varied with exposure level. Exposure to high peat and to a lesser extent low peat increased systolic and diastolic BP relative to filtered air. In contrast, only exposure to low peat elevated BRS and aconitine-induced arrhythmogenesis relative to filtered air and increased circulating levels of low-density lipoprotein cholesterol, complement components C3 and C4, angiotensin-converting enzyme (ACE), and white blood cells. Taken together, exposure to peat smoke produced overt and latent cardiovascular consequences that were likely influenced by physicochemical characteristics of the smoke and associated adaptive homeostatic mechanisms.  相似文献   
75.
76.
AIM: To observe the characteristics of iridociliary cysts in myopic patients and evaluate the influences on the position and safety of implantable collamer lens (ICL) after surgery.METHODS: Totally 270 eyes of 135 patients who underwent ICL surgery for the correction of myopia were included in this study. We observed preoperative and postoperative morphology of iridociliary cysts in ultrasonic biomicroscopy (UBM) image.RESULTS: A total of 138 iridociliary cysts were found in 88 eyes of 50 patients among 270 eyes of 135 patients before surgery (37%). Twenty-five patients had cysts in one eye (50%) and 25 had cysts in both eyes (50%). The prevalence of iridociliary cysts was negatively correlated with age, but no gender difference (P>0.05). The incidence of iridociliary cysts was much less in eyes with myopia greater than -9.00 D (P<0.05). The diameter of the largest cyst was 1.96 mm and the smallest cyst was 0.24 mm, with a majority within the range of 0.5 to 1.0 mm. Most of the cysts were located in the inferior temporal quadrant. One year after ICL implantation, 51 iridociliary cysts (37%) remained unchanged, 47 cysts (34%) decreased in size, and 40 cysts (29%) disappeared. Most of cysts that changed after surgery were smaller than 1.0 mm (P<0.05) and located in the nasal and temporal sides around the haptics of implantable lens. All the implantable lens were in their original position.CONCLUSION: Iridociliary cysts are commonly seen in myopic eyes. The cysts have no impact on the safety of ICL surgery. Some cysts may decrease in size or disappear after ICL implantation.  相似文献   
77.
1.?Xenobiotics are metabolized and eliminated through the coordinated interplay of their metabolizing enzymes and transporters. However, these two activities in vitro are measured separately, with the addition of ATP as a pre-requisite.

2.?We propose a human renal cell-line model which integrates the sulfate and glutathione conjugation of xenobiotics with the efflux of their respective conjugates. Sulfation and glutathionylation represent two major Phase II detoxification of xenobiotics in man. The reactions are catalyzed, respectively, by phenolsulfotransferase and glutathione-S-transferase followed by extrusion of their respective conjugates.

3.?Using Ko-143, a specific inhibitor of breast cancer resistance protein (BCRP), an ATP-binding cassette (ABC) transporter, we identified this transporter to be responsible for the efflux of p-cresol sulfate, harmol sulfate and the glutathione conjugate of 1-chloro-2,4-dinitrobenzene.

4.?The conjugation-cum-efflux was inhibited by oligomycin and uncouplers, which highlights the role of cellular mitochondria in providing ATP for the biosynthesis of their conjugating agents, 3′-phosphoadenosine-5′-phosphosulfate (PAPS) and reduced glutathione as well as for the transport function of BCRP.

5.?The human 786-O renal cell-line provides a “3-in-1” system linking ATP biosynthesis to metabolism of xenobiotics and their ultimate transport and elimination by BCRP; this integrated system was not apparent in other human cell-lines examined.  相似文献   
78.
79.
80.
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