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   3919篇
  免费   270篇
  国内免费   19篇
耳鼻咽喉   35篇
儿科学   145篇
妇产科学   82篇
基础医学   537篇
口腔科学   106篇
临床医学   393篇
内科学   837篇
皮肤病学   65篇
神经病学   509篇
特种医学   117篇
外科学   394篇
综合类   10篇
预防医学   296篇
眼科学   99篇
药学   242篇
中国医学   2篇
肿瘤学   339篇
  2023年   37篇
  2022年   69篇
  2021年   131篇
  2020年   83篇
  2019年   105篇
  2018年   121篇
  2017年   128篇
  2016年   130篇
  2015年   122篇
  2014年   157篇
  2013年   199篇
  2012年   304篇
  2011年   281篇
  2010年   155篇
  2009年   138篇
  2008年   246篇
  2007年   268篇
  2006年   237篇
  2005年   276篇
  2004年   224篇
  2003年   183篇
  2002年   186篇
  2001年   39篇
  2000年   31篇
  1999年   31篇
  1998年   36篇
  1997年   30篇
  1996年   22篇
  1995年   25篇
  1994年   18篇
  1993年   10篇
  1992年   12篇
  1991年   7篇
  1990年   5篇
  1989年   10篇
  1988年   14篇
  1987年   7篇
  1986年   8篇
  1985年   8篇
  1984年   7篇
  1983年   13篇
  1982年   5篇
  1979年   8篇
  1978年   6篇
  1972年   11篇
  1971年   5篇
  1970年   6篇
  1969年   4篇
  1961年   4篇
  1956年   4篇
排序方式: 共有4208条查询结果,搜索用时 30 毫秒
101.
Water frogs, Pelophylax perezi, that are introduced in the Azores, were screened for parasites using PCR primers known to amplify Apicomplexa parasites, and using nematode-specific primers. With the former, three different organisms were detected: Hepatozoon, a trichodinid protozoan ciliate and a possible Stramenopile. Using the latter set of primers, a single unknown spirurid nematode was also detected. Phylogenetic analyses indicate that Hepatozoon detected within amphibian hosts appear to form a clade, although relationships of these parasites do not match the vertebrate intermediate host phylogeny. Regarding the possible Stramenopile, it is unclear whether this organism was actually present on the amphibian or in the water on the surface of the tissue sample. Our findings highlight that many different organisms can be detected with these primers and that they can be used to screen introduced host populations to detect parasites that have been brought with them.  相似文献   
102.
103.
BACKGROUND: Efflux pumps situated on the plasma membrane, such as P-glycoprotein (Pgp) and the multidrug resistance related-protein 1 (MRP-1), have been shown to extrude HIV protease inhibitors from the cell. MRP-1 is present on many barrier sites throughout the body, such as the blood-brain and blood-testis interfaces and could reduce the concentration of protease inhibitors in these sanctuary sites for HIV-1 replication. Factors that modulate efflux pump function in vivo are poorly defined. OBJECTIVE: To analyze the inhibitory potential of the anti-retroviral drugs indinavir, amprenavir, ritonavir, lamivudine or zidovudine to modulate MRP-1 function. METHODS: Effect of anti-HIV drugs on the efflux pump activity of MRP-1 was evaluated in the presence of increasing concentrations of human plasma, using UMCC-1/VP cells which stably over-express MRP-1. MRP-1 activity was abrogated by probenecid. The potential of blocking MRP-1 function for an extended (3 day) time period, was also examined in MRP-1 over-expressing cells cultured with either probenecid or the anti-retroviral drugs and a cytotoxic compound (etoposide) that is transported by MRP-1. RESULTS: Ritonavir inhibited the functional activity of MRP-1 similarly to probenecid, as demonstrated by re-sensitization of MRP-1 over-expressing cells to cytotoxic effects of etoposide. Inhibition by ritonavir was inversely related to the concentration of human plasma added to the cells (r2 = 0.89). Other anti-HIV drugs didn't affect the MRP-1 mediated efflux of etoposide. CONCLUSIONS: These data may be exploitable to further improve sanctuary site concentrations of anti-HIV or anti-cancer drugs by using ritonavir as a lead compound to develop more potent MRP-1 inhibitors.  相似文献   
104.
105.
BACKGROUND & AIMS: A population-based cohort from Copenhagen County comprising 1160 patients diagnosed with ulcerative colitis between 1962 and 1987 was followed-up until 1997 to describe survival and cause-specific mortality. METHODS: Observed vs. expected deaths were presented as standardized mortality ratio (SMR) with exact 95% confidence intervals (CI) calculated by using individually registered person-years at risk and Danish 1995 mortality rates. Cumulative survival curves were calculated. RESULTS: A total of 261 deaths occurred, not significantly different from the expected number of 249 (SMR, 1.05; 95% CI, 0.92-1.19). The median age at death among men was 70 years (range, 6-96 years) and among women 74 years (range, 25-96 years). Twenty-five deaths (9.6%) were caused by complications to ulcerative colitis, mostly infectious and cardiovascular postoperative complications. Patients older than 50 years of age at diagnosis and with extensive colitis showed an increased mortality within the first 2 years because of ulcerative colitis-associated causes. The mortality from colorectal cancer was not increased and that of cancer in general was significantly lower than expected: 50 vs. 71 (SMR, 0.70; 95% CI, 0.52-0.93). A significantly increased mortality from pulmonary embolism and pneumonia was found. Among women only, death from genitourinary tract diseases and suicide was significantly increased. CONCLUSIONS: Despite an overall normal life expectancy for patients with ulcerative colitis, patients >50 years of age and with extensive colitis at diagnosis had increased mortality within the first 2 years after diagnosis, owing to colitis-associated postoperative complications and comorbidity.  相似文献   
106.
107.

Introduction

As the human immunodeficiency virus (HIV)-positive population ages, issues concerning sexuality and fertility, among others, are becoming relevant. HIV is still surrounded by stigma and taboos, and there have been few studies conducted in industrialized settings concerning these questions. We therefore wanted to investigate the perception of sexuality and fertility in women living with HIV (WLWH) in an industrialized setting, using a questionnaire.

Methods

WLWH were recruited at their regular outpatient clinic visits, at the major Departments of Infectious Diseases in Denmark and Finland, from January 2012 to October 2013. A questionnaire was developed, study participants were informed of the nature of study and, if they agreed to participate and signed a consent form, they filled in the questionnaire. Demographic information on the participants was obtained from patient files (in Finland) or from a national HIV cohort (in Denmark). Statistical analysis was performed using STATA®, version 11.

Results

In total, 560 women were included in the study. The median age was 44 years. The majority were of white European origin, with fully suppressed HIV viral load, CD4 cell count >350 µL and mild or no symptoms of their HIV infection. A total of 62% were sexually active, stating condom use as their sole form of contraception. Of the sexually inactive women, one-third were in steady relationships. Eighty percent reported prior pregnancies, of which the majority had one or more children. Most children were born prior to the women''s HIV diagnosis and the mode of conception was predominantly natural. One-quarter of the participating women desired pregnancy, while more than half did not. The remaining quarter either stated that they already had the desired number of children or chose not to answer the question. Fourteen percent stated that their HIV diagnosis ended their wish for children; of these women, the median time of diagnosis was between 1995 and 1996. Pregnancy had been attempted unsuccessfully in one-quarter of study participants. The final question inquired what the risk of mother-to-child transmission was, with all precautions taken. Fifteen percent estimated the risk to be above two percent.

Conclusions

In conclusion, the majority of WLWH in industrialized settings in Denmark and Finland have few HIV-related symptoms, are sexually active and have a strong desire for children.  相似文献   
108.
The prevalence of preterm delivery is considerably elevated in women with type 1 diabetes. The aim of the study was to evaluate haemoglobin A(1c) (HbA(1c)) as a predictor of preterm delivery. Two hundred thirteen consecutive pregnant women with type 1 diabetes and normal urinary albumin excretion were included prospectively. HbA(1c) was analyzed at 10, 20 and 28 weeks of gestation. Seventy-one women (33%) delivered pre term and 142 at term. At 10 weeks of gestation, HbA(1c) was 7.3% (S.D. 1.0) vs. 6.9% (S.D. 0.9) (P<.01), at 20 weeks of gestation 6.6% (S.D. 0.7) vs. 6.1% (S.D. 0.7) (P<.001) and at 28 weeks of gestation 6.7% (S.D. 0.8) vs. 6.1% (S.D. 0.7) (P<.001). When comparing HbA(1c) at 10, 20 and 28 weeks of gestation, HbA(1c) at 28 weeks of gestation (P<.001) was the best predictor of preterm delivery. The adjusted odds ratio per 1% increment in HbA(1c) at 28 weeks of gestation was 2.8 (95% CI 1.7-4.4). HbA(1c) at 28 weeks of gestation was a clinical significant predictor of preterm delivery in type 1 diabetes.  相似文献   
109.
OBJECTIVE: To investigate hand problems in patients with systemic lupus erythematosus (SLE) and to explore consequences on the ability to perform daily activities. METHODS: One hundred nine patients with SLE completed a questionnaire assessing hand problems in terms of deficits in body structures, e.g., joints, and body functions including pain, grip force, and other physiologic functions of the hand, the Health Assessment Questionnaire (HAQ), and the Simple hand test. Patients who stated problems in hand function answered questions about performance of daily activities and to what extent different deficits in body structures and body functions interfered. RESULTS: Seventy-three percent of patients experienced hand problems and 42% reported interference with performance of daily activities. Problems from body structures of the hand were distributed relatively evenly over joints and tendons/muscles. Reduced grip force and activity-induced pain were the most commonly reported problems in body functions. The most affected activity area was productivity, namely household tasks, work at home, work/study, and child care; least affected was self-care. Reduced grip force followed by fumbling and pain were the most frequently reported body functions to create difficulties in performing daily activities. When comparing patients with and without difficulties in performing daily activities, there were significant differences in problems from tendons/muscles, joints in the thumb, reduced force, stiffness, fumbling, numbness/tingling, and the HAQ. CONCLUSION: A majority of the study group had hand problems and almost half of the group experienced difficulties in performing daily activities due to SLE. The most affected activity area was productivity, where reduced grip force, fumbling, and pain were the most interfering body functions.  相似文献   
110.
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