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   1906篇
  免费   125篇
  国内免费   43篇
儿科学   2篇
妇产科学   223篇
基础医学   256篇
口腔科学   1篇
临床医学   90篇
内科学   28篇
皮肤病学   10篇
神经病学   9篇
特种医学   33篇
外科学   923篇
综合类   219篇
预防医学   111篇
眼科学   1篇
药学   85篇
中国医学   76篇
肿瘤学   7篇
  2024年   3篇
  2023年   12篇
  2022年   13篇
  2021年   67篇
  2020年   51篇
  2019年   52篇
  2018年   48篇
  2017年   41篇
  2016年   61篇
  2015年   58篇
  2014年   91篇
  2013年   99篇
  2012年   87篇
  2011年   87篇
  2010年   98篇
  2009年   80篇
  2008年   76篇
  2007年   88篇
  2006年   111篇
  2005年   73篇
  2004年   66篇
  2003年   71篇
  2002年   50篇
  2001年   51篇
  2000年   39篇
  1999年   32篇
  1998年   21篇
  1997年   28篇
  1996年   37篇
  1995年   34篇
  1994年   39篇
  1993年   20篇
  1992年   21篇
  1991年   34篇
  1990年   34篇
  1989年   30篇
  1988年   21篇
  1987年   14篇
  1986年   18篇
  1985年   15篇
  1984年   20篇
  1983年   17篇
  1982年   6篇
  1981年   19篇
  1980年   11篇
  1979年   13篇
  1978年   7篇
  1975年   3篇
  1974年   2篇
  1972年   2篇
排序方式: 共有2074条查询结果,搜索用时 15 毫秒
31.
A retrospective study was conducted in a large population to determine whether sperm quality has changed in Northeastern Spain between 1960 and 1996. From a total initial population of 22,759 men, two separate groups were studied: men with spermatozoa (n = 20,411) and those with azoospermia (n = 1364). After adjustment for age and sexual abstinence, multiple linear regression analyses were used to assess changes in semen parameters over time. A 0.2% decline was observed in semen volume in the spermatozoa group (P < 0.001). No significant increase (0.04%) in sperm count (x 10(6)/ml) was observed in the spermatozoa group. There was a 0.4% increase in motile spermatozoa in the spermatozoa group (P < 0.001). There was a statistically significant decline in normal spermatozoa (3.6%) in the spermatozoa group (P < 0.001). Of the total population, 1364 men had azoospermia (6.0%). The changes observed in the semen parameters analysed in this large population showed no evidence of a deteriorating sperm quality, although a statistically significant decline was observed in the percentage of normal spermatozoa.  相似文献   
32.
Following interferon therapy, a chronic hepatitis B (HBV) carrier lost all serum markers of active viral replication and became anti-HBe positive but remained positive for free and replicative HBV-DNA in semen, saliva, urine, and liver four months later. At 12 months, when he also developed anti-HBs, urine and saliva analysed for free HBV-DNA were positive. Despite histological remission and loss of HBV-DNA from serum, the potential for transmission of HBV and reactivation of disease remain.  相似文献   
33.
Sperm penetration assay (SPA) scores obtained from cryobanked semen were correlated with therapeutic insemination (TI) fecundity in a group of established sperm donors, thereby evaluating the efficacy of the SPA in screening donors for sperm banking. While the SPA has been used to separate fertile from infertile males, we altered assay conditions to use frozen semen and to distinguish performance among fertile donors. Three frozen ejaculates from 11 pregnancy-proven donors were analysed. Of 905 TI cycles, 275 recipients achieved 95 pregnancies. There were no significant relationships between fecundity and donor semen, washed sperm parameters, sperm recoveries or recipient age. A significant relationship was revealed between mean SPA scores (range 8.7-66.6 penetrations/ovum) and donor fecundity (range 0.04-0.16, P < 0.03). Sperm concentration was varied in an effort to establish the most sensitive test condition. Using 0.25x10(6) motile spermatozoa/ml, a highly significant relationship was observed (P < 0.002). The four donors with the lowest SPA scores achieved the four lowest fecundities. It is concluded that a modified SPA can be used on frozen donor semen to estimate donor fertility potential. If applied routinely in donor semen banking, poor quality applicants could be excluded, thereby increasing pregnancy rates while decreasing donor screening costs.  相似文献   
34.
BACKGROUND: Studies have suggested that the quality of human semen has been declining over recent decades, presumably because of lifestyle or environmental factors. METHODS: Polychlorinated biphenyls and organochlorine pesticides were analysed in the plasma of 25 men with poor semen quality, 20 men with normal semen quality and idiopathic subfertility and 27 men with normal semen quality and female factor subfertility. Samples of seminal fluid were also analysed to assess the relationship between the levels in blood and semen. RESULTS: The results indicate no difference in the levels of organochlorines between the groups. The levels of organochlorines in seminal fluid were proportional to the levels in plasma, but approximately 40 times lower. Men with poor semen quality were three times more likely to be obese than men with normal semen quality. There was also a significant negative correlation between semen quality parameters and body mass index among men with normal semen quality. The prevalence of sedentary work was lowest among men with the best semen quality. CONCLUSIONS: Poor semen quality was found to be associated with sedentary work and obesity but not with plasma levels of persistent organochlorines. More research is needed to assess whether sedentary lifestyle and obesity are causal factors in the decline of semen quality.  相似文献   
35.
BACKGROUND: It has been suggested that finger length may correlate with function or disorders of the male reproductive system. This is based on the HOXA and HOXD genes' common embryological control of finger development and differentiation of the genital bud. The objective of this study was to explore the association between the ratio of 2nd to 4th finger length (2D:4D ratio) and testis function in a sample of young Danish men from the general population. METHODS: Semen samples and finger measurements were obtained from a total of 360 young Danish men in addition to blood samples for sex hormone analysis to describe the possible association between 2D:4D and semen and sex-hormone parameters. RESULTS: A statistically significant inverse association with the 2D:4D was found only in relation to hormone levels of FSH in the group of young men with a 2D:4D >1 (P = 0.036) and a direct association with the total sperm count in the group of young men with a 2D:4D < or = 1 (P = 0.045). CONCLUSION: The statistically significant results may be 'false positives' (type I error) rather than representing true associations. This relatively large study of young, normal Danish men shows no reliable association between 2D:4D finger ratio and testicular function. Measurements of finger lengths do not have the power to predict the testicular function of adult men.  相似文献   
36.
Clomiphene, a selective oestrogen receptor modulator, has been utilised in managing male sub-fertility since 1967. Numerous controlled and uncontrolled studies have been published regarding the efficacy of clomiphene citrate in male sub-fertility cohorts. Although the primary intention of treating men with clomiphene citrate is to improve sperm parameters and testosterone levels, some studies have reported paradoxical decline in semen parameters. The information available on decline in sperm parameters following treatment with clomiphene is sparse. We conducted a systemic review using PubMed, Embase, Cochrane Library and Scopus databases for original studies reporting adverse effects of clomiphene citrate therapy on sperm parameters. This systematic review includes 384 men from 11 different studies that reported adverse effects of clomiphene citrate therapy. Of the men included in these studies, 19%, 21%, 17% and 24% of clomiphene-treated men demonstrated a decrease in sperm count, concentration, motility and total motile sperm count respectively. In up to 17% of patients, deterioration of semen parameters did not recover following discontinuation of therapy. In the future, more studies should report on this aspect so the magnitude of this effect can be more clearly understood.  相似文献   
37.
The objective of this study was to compare semen quality (sperm density, progressive motility and spermia) between long-term childhood cancer survivors and a control group of males. The second objective was to correlate the semen analysis of the survivors with cancer treatment and endocrine status. The semen quality of 143 survivors (median age, 23.6 years) was compared to 200 men (median age, 27.9 years) who had not been diagnosed with cancer. The cancer-related risk factors and gonadotrophin levels were compared. Overall, 65% of the survivors had abnormal semen analysis compared to 26.5% of the controls (p < 0.0001). Survivors with nonaspermia had lower sperm density than the controls (p < 0.001). Other observed correlations were not significant. Survivors who were treated with alkylating agents were more likely to have abnormal semen analysis (p < 0.008). Follicle-stimulating hormone and luteinising hormone levels were significantly elevated (p < 0.0001) in survivors with abnormal semen analysis. The semen quality parameters, except for low sperm density, did not differ in survivors with nonaspermia compared to the controls. The risk factors included treatment with alkylating agents. Elevated gonadotrophin levels correlated with abnormal semen analysis. All cancer survivors should be made aware of the possibility of suffering from cancer treatment-related infertility.  相似文献   
38.
A proportion of men are infertile despite having normal medical history/physical examination and normal semen analysis. We aimed to assess whether normal sperm parameters per se account for male factor fertility. 1,957 infertile men were compared with 103 age-comparable fertile controls. Semen analysis was based on 2010 World Health Organization reference criteria. Of all, 12.1% of infertile men and 40.8% of fertile men presented with normal sperm parameters. Among fertile men, 36.9% had isolated sperm abnormalities and 22.3% men showed two or more concomitant sperm abnormalities. Serum total testosterone was higher in infertile men with normal sperm parameters compared to those with ≥2 sperm abnormalities or azoospermia, but similar to those with isolated sperm abnormalities (p ≤ .001). Circulating hormones were similar among sperm parameters groups in fertile men. At multivariable analyses, testicular volume (OR 1.12, p ≤ .001) and FSH (OR 0.8, p ≤ .001) were associated with normal sperm parameters. Overall, the longer the infertility period, the greater the number of sperm parameters abnormalities (p < .01). In conclusion, we found that 12% of infertile men and only 41% of fertile men present with normal sperm parameters. Normal sperm parameters per se do not reliably account for fertility in the real-life setting.  相似文献   
39.
Seminal oxidative stress (OS) is a major contributing factor to male infertility. Semen analysis cannot identify reactive oxygen species (ROS), which can be measured using a chemiluminescence assay. Measurement of redox potential provides a more comprehensive assessment of OS, although the test has yet to be fully validated. This study aimed to validate the MiOXsys analyser for measuring static oxidation–reduction potential (sORP). Results demonstrated that duplicate measurements must be taken, sensors must be batch tested, and sockets should be regularly changed to avoid inconsistency in measurement. Measurement of sORP using MiOXsys exhibited good reproducibility across different operators (p = 0.469), analysers (p = 0.963) and days (p = 0.942). It is not affected by mechanical agitation (p = 0.522) or snap freezing and thawing (p = 0.823). The stability of sORP over time requires further verification, particularly in samples with high initial sORP. Measurement is temperature sensitive between 2 and 37°C, significantly increasing with increasing temperature (p = 0.0004). MiOXsys is a more stable assay for assessing OS than chemiluminescence methods and permits greater flexibility for sample handling. MiOXsys could be implemented to complement semen analysis as part of routine diagnostic testing for male infertility and may be useful in identifying contributing factors to idiopathic infertility.  相似文献   
40.
Infertility is a major health issue affecting over 48.5 million couples around the world, with the male factor accounting for about 50% of the cases. The conventional semen analysis recommended by the World Health Organization (WHO) is the cornerstone in the evaluation of male fertility status. It includes macroscopic and microscopic evaluation of the ejaculate, which reflects the production of spermatozoa in the testes, the patency of the duct system and the glandular secretory activity. Evaluation of seminal fructose, sperm vitality and leucocytes (Endtz test) are useful adjuncts to semen analysis that provide information on specific clinical conditions. Though several computer-assisted sperm analysis (CASA) systems have been developed, conventional methods for semen analysis are still widely accepted in clinical practice. This review summarises the conventional techniques used in routine semen analysis and their diagnostic value in clinical andrology.  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