首页 | 官方网站   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   209078篇
  免费   15564篇
  国内免费   741篇
医药卫生   225383篇
  2023年   754篇
  2022年   825篇
  2021年   3436篇
  2020年   2106篇
  2019年   3391篇
  2018年   3967篇
  2017年   3210篇
  2016年   3410篇
  2015年   4066篇
  2014年   6095篇
  2013年   8823篇
  2012年   13123篇
  2011年   14321篇
  2010年   8096篇
  2009年   7304篇
  2008年   13588篇
  2007年   14424篇
  2006年   13918篇
  2005年   14396篇
  2004年   13806篇
  2003年   12900篇
  2002年   12437篇
  2001年   1878篇
  2000年   1461篇
  1999年   2054篇
  1998年   2830篇
  1997年   2439篇
  1996年   2208篇
  1995年   1954篇
  1994年   1756篇
  1993年   1657篇
  1992年   1216篇
  1991年   1150篇
  1990年   1055篇
  1989年   956篇
  1988年   1017篇
  1987年   1028篇
  1986年   1004篇
  1985年   1084篇
  1984年   1484篇
  1983年   1463篇
  1982年   1815篇
  1981年   1607篇
  1980年   1517篇
  1979年   778篇
  1978年   927篇
  1977年   905篇
  1976年   807篇
  1975年   662篇
  1974年   656篇
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
101.
Prostatitis and male infertility are frequent disorders, and the role of prostatitis in male infertility has been under discussion for more than 30 years. Many researchers have shown relevant links between the two. Although a causal relationship has not been definitely demonstrated, increasing evidence shows that chronic prostatitis has a relevant negative impact on male fertility potential, at least in certain subgroups. In the following review, we focus on the present state of knowledge on the role of chronic prostatitis as an etiologic factor in male infertility.  相似文献   
102.
PURPOSE: The aim of this study was to determine the reproducibility of measurements made using the Sonogage Corneo-Gage Plus 2 (Cleveland, Ohio) ultrasound pachymeter of total corneal and corneal epithelial thickness in 5 different regions of the cornea. METHODS: Twenty-seven subjects at the New England College of Optometry (NECO) and 20 subjects at the Southern College of Optometry (SCO) were enrolled in this study. Measurements were taken of the central cornea as well as the nasal and temporal regions of the midperipheral and peripheral regions of the right cornea of each subject. Identical measurements were again taken in these subjects 1 week later at approximately the same time of day. Within-subject variations were then assessed using paired t tests. RESULTS: The only significant measurement differences that were found between visits were for full corneal thickness at both the nasal and temporal midperipheral locations. The mean differences for these locations were 13.5 microm and 13.7 microm, respectively. CONCLUSIONS: Epithelial corneal thickness and central and peripheral total corneal thickness measurements using the Corneo-Gage Plus 2 pachymeter were reproducible; however, midperipheral total corneal thickness measurements showed poor reproducibility.  相似文献   
103.
Hepatitis C virus (HCV)-specific impairments in host immunity have been described at multiple levels of the innate and adaptive response, which may lead to viral persistence in the majority of infections. Understanding of HCV-associated immune defects could lead to novel therapeutic advances. Natural killer (NK) cells, the major effector cells of the innate immune system, are functionally impaired in chronic HCV infection. It has been suggested that this phenotype is a result of virus-specific defects in antigen-presenting cells (APCs) that regulate NK cell activity, as normal NK function is restored when they are stimulated ex vivo. In this study, we used human NK cell cytotoxicity assays to evaluate the activation-induced effects of NK cells on the HCV replicon-containing hepatic cells. We found that cytokine-activated NK cells were capable of inducing an HCV-associated, perforin/granzyme-dependent lysis of human hepatoma cells and that this required direct cellular contact and was independent of MHC class I expression levels. In contrast, on removal of cytokine stimulation, NK cells failed to exert any direct cytolytic effect on replicon targets. These findings suggest an important underlying mechanism by which NK cells control HCV infection and, with appropriate understanding of HCV-associated immune defects, could lead to novel therapeutic advances.  相似文献   
104.
105.
106.
Abstract: Background: Identification of risk drinking in expectant fathers may be helpful as an important part of efforts to minimize maternal alcohol use, and as an opportunity to inform them about a problematic practice during a critical developmental stage for the couple. The purpose of this study was to evaluate the T‐ACE screening questionnaire, which asks about t olerance to alcohol, being a nnoyed by other's comments about drinking, attempts to c ut down, and having a drink first thing in the morning (“ e ye‐opener”), in the male partners of pregnant women who themselves were T‐ACE positive. Methods: Two hundred fifty‐four male partners were asked to complete the T‐ACE embedded in a health survey, the Alcohol Use Disorders Identification Test (AUDIT), and other questions about their alcohol use in the past 30 days when their pregnant partners had a median gestation of 11.5 weeks (T1). After delivery, male partners again completed the T‐ACE and quantity‐frequency questions (T2). The predictive ability of the T‐ACE and AUDIT was compared, using risk drinking (>4 drinks/day or >14 drinks/week) as the criterion standard. Results: A substantial minority of male partners had risk drinking, 31 percent at T1 and 25 percent at T2. Although the AUDIT was better than the T‐ACE as an independent predictor of risk drinking, the latter was most accurate when the tolerance threshold exceeded 2 drinks, the same established for pregnant women. The sensitivity (T1 = 84.6%, T2 = 82.8%) and specificity (T1 = 43.8%, T2 = 51.1%) of the T‐ACE at this threshold compared favorably with those of the AUDIT at the standard cut point of 8. Conclusions: The T‐ACE may be a practical way for clinicians to identify risk drinking in both pregnant women and expectant fathers. (BIRTH 33:2 June 2006)  相似文献   
107.
The present study demonstrates that alcohol-induced memory impairment can be attenuated by pretreatment with an oral tryptophan supplementation. These results provide support for the role of a brain serotonin deficit in this impairment and highlight the impact a dietary manipulation can have on a complex behavioral process.  相似文献   
108.
Background.Computers that collect data from patients and provide both patients and practitioners with printed feedback on a range of health risks are a tool for assisting general practitioners with preventive care. This study assessed the impact of computer-generated printed feedback on cervical screening among women who were underscreened for cervical cancer.Method.Female attenders at two Australian general practices were randomly allocated to Experimental or Control groups. Women in both groups completed a health risk survey on a touch screen computer prior to their consultation. Those in the Experimental group received printed pages summarizing their results, including their eligibility for cervical screening and last Pap test, for themselves and their doctor. The number and proportion of underscreened women who had a Pap test in the 6 months after completing the computer survey, as determined by pathology records, were examined.Results.Of the 679 participants, 139 were classified as underscreened on the basis of self-report (74 Experimental, 65 Control) and 272 on the basis of their pathology records (148 Experimental, 124 Control). Overall about one-third of women had a test in the 6-month period, and the differences between the groups were not significant for women overall (18–70 years) or for women 18–49 years. Among women 50–70 who were underscreened based on self-report, those receiving the printout were more likely to have a Pap test in the next 6 months (P< 0.05). This pattern was also evident, but did not reach statistical significance, for older women who were underscreened based on pathology records.Conclusions.We are unable to draw conclusions regarding the effectiveness of the computer system due to the modest proportions of women screened, the small numbers, and the fact that the computer survey may have created an intervention effect in the Control group. As the study suggests the computer system is acceptable to women and may be effective for encouraging screening among older women, further exploration of the system is desirable.  相似文献   
109.
Omeprazole is a member of a new class of substituted benzimidazoles. These agents inhibit the proton pump in the gastric parietal cell, blocking the final step in the gastric acid secretory pathway. Omeprazole has been investigated for the treatment of gastric ulcer, duodenal ulcer, gastroesophageal reflux, and various hypersecretory states. The prolonged inhibition of gastric acid secretion allows for once-daily dosing in patients with peptic ulcer disease and gastroesophageal reflux, and once- or twice-daily dosing in patients with Zollinger-Ellison syndrome. Compared with currently available therapies, omeprazole is well tolerated and demonstrates a more rapid ulcer healing rate. It is superior to conventional therapies in the treatment of Zollinger-Ellison syndrome. Side effects are infrequent when the drug is used for the short-term management of ulcers.  相似文献   
110.
Summary: This is the first report of the largest study of blood pressure measurement in pregnancy in a New Zealand population using standardized definitions and methodology. Over 3,800 women who delivered in an 8-month period in the Wellington region were included in the study. Blood pressure measurement and the presence of oedema and proteinuria were recorded from booking until delivery and in the puerperium. Only 2.7% of women were unable to be contacted after delivery for details on outcomes. The results established normal ranges for blood pressure throughout pregnancy. The data show that Mood pressure greater than 140/90 until 35 weeks' gestation is outside 2 standard deviations at all gestations and justifies using these measurements as the definition of hypertension in pregnancy. The fall in blood pressure in the 2nd trimester was less than 1 mm Ffg per week in both the systolic and diastolic pressures. This fall was smaller than previously recorded in other studies. Gestational hypertension was the commonest blood pressure abnormality occurring in 15.2% of the population. This represented 69% of the pregnant women with a hypertensive disorder. The overall incidence of both gestational hypertension and preeclampsia was 18.5% which is higher than reported in other parts of the world. In this study obesity was significantly associated with hypertensive disorders in pregnancy. An arm circumference of >33 cm, one of the measurements of obesity, was found in 6.8% of the study population. Even after the effect of arm circumference was taken into account, hypertensive disorders were also more common in Pacific Island women. Ankle oedema was significantly associated with the development of both gestational hypertension and preeclampsia but the incidence of oedema was noted in only 11.9% of the subjects.  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-23

京公网安备 11010802026262号