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   8790篇
  免费   554篇
  国内免费   173篇
耳鼻咽喉   9篇
儿科学   124篇
妇产科学   1114篇
基础医学   1290篇
口腔科学   36篇
临床医学   579篇
内科学   1083篇
皮肤病学   58篇
神经病学   1280篇
特种医学   119篇
外科学   558篇
综合类   856篇
现状与发展   2篇
一般理论   27篇
预防医学   1166篇
眼科学   52篇
药学   711篇
  1篇
中国医学   211篇
肿瘤学   241篇
  2023年   139篇
  2022年   156篇
  2021年   297篇
  2020年   326篇
  2019年   330篇
  2018年   288篇
  2017年   292篇
  2016年   297篇
  2015年   275篇
  2014年   463篇
  2013年   659篇
  2012年   413篇
  2011年   417篇
  2010年   366篇
  2009年   400篇
  2008年   373篇
  2007年   362篇
  2006年   382篇
  2005年   303篇
  2004年   275篇
  2003年   291篇
  2002年   217篇
  2001年   200篇
  2000年   210篇
  1999年   159篇
  1998年   131篇
  1997年   131篇
  1996年   110篇
  1995年   123篇
  1994年   88篇
  1993年   76篇
  1992年   94篇
  1991年   84篇
  1990年   73篇
  1989年   62篇
  1988年   53篇
  1987年   56篇
  1986年   63篇
  1985年   66篇
  1984年   82篇
  1983年   34篇
  1982年   45篇
  1981年   49篇
  1980年   46篇
  1979年   37篇
  1978年   31篇
  1977年   19篇
  1976年   31篇
  1975年   12篇
  1973年   9篇
排序方式: 共有9517条查询结果,搜索用时 62 毫秒
81.
Myocardial infarction (MI) occurs more frequently in the morning as a result of the concomitant unfavorable timing of several physiological parameters and/or biochemical conditions. However, little is known about the possible influence of this circadian pattern on prognosis. To evaluate whether the time of symptom onset could potentially influence mortality from acute MI, this prospective study considered all consecutive MIs admitted to the ED of Ferrara, Italy, after a call to the Emergency Coordinating Unit from January 1, 1998, to December 31, 2001. The total sample consisted of 442 MIs (mean age, 68.7 years; males, 72%). Eighty patients (males, 82.5%) died in the ED; the remaining 362 were admitted to the hospital. Of these, 50 (males, 60%) died during their hospital stay. Based on the timing of their symptom onset, cases were categorized both into 24 1-hour intervals and four 6-hour intervals (midnight to 5:59 am, 6:00 am to 11:59 am, noon to 5:59 pm, and 6:00 pm to 11:59 pm), and the circadian distributions of fatal versus nonfatal MIs were compared. The circadian variation of MI peaked between 6:00 am and noon (P < .001), and in this period, there was a trend toward a higher frequency of fatal cases (41.5% vs. 35.2%; chi(2) = 1.911, P = .167). To verify whether this higher frequency of fatal events in the morning hours could be related to possible higher severity of cases observed in that hours, a further separate analysis considering age, infarct site, and peak levels of MB was made. Again, no significant temporal differences among the four 6-hour intervals were found between fatal and nonfatal Mis, although a trend toward older age was observed in morning MIs. Not only the frequency, but also the mortality, of acute MI could be increased in the morning hours. This could be of practical interest for emergency doctors and could have significant implications for acute treatment, because several studies have reported a lowered efficacy of thrombolytic drugs in the morning hours.  相似文献   
82.
目的:探讨书写表达对反复胚胎移植失败(RIF)女性患者生育压力与负性情绪的干预效果。方法:选取2021 年1月至2022 年4 月温州医科大学附属第一医院生殖医学中心RIF女性患者213 例为研究对象,按照患者病案号奇偶数分为观察组105例和对照组108例。对照组采取常规辅助生殖健康宣教,观察组在对照组的基础上进行书写表达干预;比较干预前后两组患者的焦虑、生育压力情况及患者满意度,分析各评分间的相关性,以及分析影响满意度的相关因素。结果:两组患者在年龄、不孕年限、文化程度、移植次数等方面差异无统计学意义(P >0.05);观察组患者在干预后的焦虑自评量表(SAS)和生育困难相关压力量表(FPI)评分均低于同期对照组,而满意度则高于对照组(均P <0.05);两组患者干预前后的焦虑变化程度与生育压力变化程度存在正相关(r =0.192,P =0.005),且干预前后的焦虑变化程度(OR =0.895, 95%CI =0.821~0.975,P =0.011)和书写表达干预(OR =0.201,95%CI =0.041~0.983,P =0.048)对患者满意度的影响具有统计学意义。结论:书写表达干预使RIF女性患者焦虑、抑郁等负性情绪得到宣泄与疏导,降低其生育压力并提高其满意度。  相似文献   
83.
This study investigated the effects of rutin against reproductive damage caused by toxic mercury in male rats. Thirty-five Sprague Dawley rats were used. Control group was injected with saline for 7 days. The rutin-100 group received 100 mg/kg/b.w. rutin for 7 days. Mercuric chloride (HgCl2) group received 1.23 mg/kg/b.w. of HgCl2 for 7 days. Mercury chloride + rutin-50 group received 50 mg/kg/b.w. rutin and HgCl2 1.23 mg/kg/b.w. for 7 days. HgCl2 + rutin-100 group received 100 mg/kg/b.w. rutin and HgCl2 1.23 mg/kg/b.w. for 7 days. It was detected that HgCl2 treatment increased malondialdehyde (MDA) levels, tumour necrosis factor-α (TNF-α) and cyclooxygenase-2 (COX-2) expressions, necrosis and degeneration of spermatogonium, dead and abnormal sperm percentages; tubular walls thinning; and decreased antioxidant enzyme activities and sperm motility. It was determined that rutin application reduced testicular damage caused by HgCl2. In conclusion, rutin administration may treat HgCl2 toxicity in testes.  相似文献   
84.
An ideal animal model is a prerequisite for the basic research of uterus transplantation. This study aimed to develop a new cervical ectopic uterus transplantation mice model, which was established by vascular anastomosis of the right common iliac artery and vein of the donor with the right common carotid artery and external jugular vein of the recipient, respectively, using the cuff method. The survival status of the transplanted uterus was assessed by macroscopic observation and histological examination after surgery, and the function of the graft uterus was tested by verifying whether the pregnancy is possible. A total of 40 transplants were performed, of which only 1 failed due to donor hemorrhage. After 26 transplants, the total operation time reduced to 52.4 ± 3.8 minutes, of which the total ischemia time took 6.6 ± 1.1 minutes. Sixty days after transplantation, all the graft uteri had a good blood supply and spontaneous contraction. The histology showed no significant difference between the transplanted uterus and the native. Embryo transfer experiments have proven that the transplanted uterus has uterine function. In conclusion, this new model is an effective and simple mice model for the studies of the scientific issues related to uterus transplantation.  相似文献   
85.
Porcine reproductive and respiratory syndrome virus (PRRSV) is an RNA virus that causes reproductive failure in sows and respiratory problems in piglets. PRRSV infection leads to substantial pig mortality and causing huge economic losses so that disease outbreaks caused by the new PRRSV strain from other regions have caused great concern in China. In this study, we analysed the pathogenicity of the novel ORF5 RFLP 1‐7‐4‐like PRRSV strain, named PRRSV‐ZDXYL‐China‐2018‐1 in pigs. The viral challenge test showed that PRRSV‐ZDXYL‐China‐2018‐1 infection can cause persistent fever, moderate dyspnoea, serum viraemia and interstitial pneumonia in piglets. The levels of viral loads in serum and PRRSV‐specific antigen were also detected in lung tissues were used one‐step Taq‐Man RT‐qPCR and Immunohistochemistry, respectively. At 28dpi, the level of specific antibodies was increased among infected piglets. Importantly, the new virus appeared be a moderately virulent isolate with pathogenicity compared to HP‐PRRSV strain LQ (JXA1‐like strain). Histological examination revealed severe monocyte haemorrhage and interstitial pneumonia associated with monocyte infiltration in the lung tissue of pigs infected with PRRSV‐ZDXYL‐China‐2018‐1 and LQ‐JXA1 strains. Immunohistochemistry (IHC) results showed positive brown‐red epithelial cells and macrophages in pig lungs. Therefore, it is critical to establish an effective strategy to control the spread of PRRSV in China.  相似文献   
86.
Porcine reproductive and respiratory syndrome virus (PRRSV) is prevalent in Danish swine herds. In July 2019, PRRSV‐1 was detected in a PRRSV‐negative boar station and subsequently spread to more than 38 herds that had received semen from the boar station. Full genome sequencing revealed a sequence of 15.098 nucleotides. Phylogenetic analyses showed that the strain was a recombination between the Amervac strain (Unistrain PRRS vaccine; Hipra) and the 96V198 strain (Suvaxyn PRRS; Zoetis AH). The major parent was the 96V198 strain that spanned ORFs 1–2 and part of ORF 3 and the minor parent was the Amervac strain, which constituted the remaining part of the genome. The virus seems to be highly transmissible and has caused severe disease in infected herds despite a high level of genetic identity to the attenuated parent strains. The source of infection was presumable a neighbouring farm situated 5.8 km from the boar station.  相似文献   
87.
A range of studies have shown that the complex process of implantation and an establishment of a pregnancy also involves immune factors. Disturbances in these underlying immune mechanisms might lead to implantation and pregnancy failure and may be involved in the pathogenesis of unexplained infertility. Several studies have reported that imbalances in uterine NK (uNK) cell abundance are associated with infertility; however, controversies exist. An increased amount of CD56+ uNK cells along with a decrease in CD16+ uNK cells have been associated with normal fertility in some studies. Very few studies of FoxP3+ regulatory T cells (Tregs) in the pre-implantation endometrium have been performed. Results are sparse and controversial, studies reporting both increased and decreased numbers of Tregs, respectively, in women suffering from infertility. In conclusion, studies imply that uNK cells, Tregs and HLA-G carry pivotal roles regarding the establishment of a healthy pregnancy, and that abnormal immune mechanisms involving these parameters may be associated with infertility. However, more research in early phases of the reproductive cycle, such as investigating the conditions in the endometrium before implantation, is needed to further clarify the underlying mechanisms.  相似文献   
88.
The presence of estrogen in the genital ducts of different mammalian species has been extensively studied and the estrogen influence on the functional activity of the male genital tract has been hypothesized. Conversely, very few data have been reported on pig excurrent ducts: the localization of classical estrogen receptors (ERα and ERβ) is scarcely known, while the expression of the G protein‐coupled receptor (GPER1), a membrane estrogen receptor, is still unknown in pig. The aim of the present study was to evaluate GPER1 expression in the different regions of the mature pig epididymis, using immunohistochemistry, western blot and RT‐PCR analyses. The results showed that GPER1 is mainly expressed in the epithelial cells of the corpus epididymis compared to the caput and the cauda, while muscle cells are moderately immunostained and stromal cells are unstained. The presence of GPER1 was confirmed by Western blot and RT‐PCR analyses. In our study, we have demonstrated for the first time the GPER1 expression in male porcine epididymis, revealing a new mediator of estrogen signaling at this site. In conclusion, these new data suggest that estrogen action via GPER1 may contribute to sperm maturation in the corpus and sperm protection/storage in the cauda. Interestingly, the presence of GPER1 in the muscle layer may be indicative of a possible GPER1 involvement in the estrogen regulation of duct contractility. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc.  相似文献   
89.
In‐home salivary collection quality and adherence to a prescribed collection methodology for evaluation of dim light melatonin onset (DLMO) is unknown in children. Primary aims of this study were to 1) describe a novel family centered methodology for in‐home salivary collection; 2) determine the acceptance and feasibility of this methodology; 3) measure adherence to collection instructions; and 4) identify patterns between participants’ age and quality of samples collected. After receiving instructional handouts from the study team, families utilized in‐home salivary melatonin collection. Participants (N = 64) included 39 children (21 female, mean age 9.5 ± 1.61 years) and 25 adolescents (11 female, mean age 15.9 ± 2.12 years) with craniopharyngioma. Participants were 90% adherent to collection schedule, and 89% of the samples collected were of sufficient quantity and quality, with no differences found between age (child vs. adolescent) and melatonin sample quantity and quality. In‐home saliva collection provides an acceptable and feasible method to collect salivary melatonin and biomarkers in children and adolescents.  相似文献   
90.
While the influence of the mother's voice on neonatal heart‐rate response and its relevant activity on cerebral cortex and the autonomic nervous system (ANS) are well known, few studies have assessed its influence on respiratory activity. We investigated the relationship among the respiration rate, the delta wave amplitudes through electroencephalography, and the basal state of ANS through the respiratory variability index while 22 full‐term neonates hear their mother's voice and an unknown voice. It was found that when respiratory variability was large, a transient (<5 s) change in respiration rates was observed in response to an unknown voice, while a greater increase in the delta wave amplitude was observed in the frontal lobe than the parietal one in response to the mother's voice. Conversely, when respiratory variability was small, a sustained increase (>10 s) in respiration rates was observed in response to the mother's voice, while a greater increase in the delta wave amplitude was found in both the frontal and parietal lobes. These results suggest that the basal state of ANS influences the latency of increases in respiration rates. Furthermore, induced by the mother's voice, transient increases in respiration rates are reduced in association with frontal lobe activity, and sustained increases in respiration rates are promoted in association with frontal and parietal lobe activities.  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