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   16414篇
  免费   761篇
  国内免费   129篇
耳鼻咽喉   516篇
儿科学   1261篇
妇产科学   523篇
基础医学   1165篇
口腔科学   968篇
临床医学   1253篇
内科学   2789篇
皮肤病学   392篇
神经病学   1059篇
特种医学   743篇
外国民族医学   2篇
外科学   3435篇
综合类   508篇
现状与发展   1篇
一般理论   7篇
预防医学   606篇
眼科学   480篇
药学   953篇
  4篇
中国医学   171篇
肿瘤学   468篇
  2024年   15篇
  2023年   187篇
  2022年   207篇
  2021年   365篇
  2020年   272篇
  2019年   318篇
  2018年   504篇
  2017年   466篇
  2016年   530篇
  2015年   455篇
  2014年   673篇
  2013年   895篇
  2012年   985篇
  2011年   1058篇
  2010年   582篇
  2009年   389篇
  2008年   883篇
  2007年   961篇
  2006年   976篇
  2005年   953篇
  2004年   1067篇
  2003年   1072篇
  2002年   987篇
  2001年   643篇
  2000年   633篇
  1999年   403篇
  1998年   156篇
  1997年   126篇
  1996年   105篇
  1995年   52篇
  1994年   45篇
  1993年   34篇
  1992年   37篇
  1991年   22篇
  1990年   17篇
  1989年   30篇
  1988年   24篇
  1987年   16篇
  1986年   22篇
  1985年   10篇
  1984年   15篇
  1983年   8篇
  1982年   9篇
  1980年   6篇
  1979年   7篇
  1978年   7篇
  1977年   7篇
  1974年   8篇
  1972年   8篇
  1967年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Morphology of the lumbar spinal canal in normal adult Turks   总被引:2,自引:0,他引:2  
Pathological changes can occur in the diameters of the lumbar spinal canal. Therefore, assessing the canal size an important diagnostic procedure. Two hundred plain anterioposterior radiographs of the lumbar spine were examined. The sample consisted of 100 males and 100 females. The transverse diameter of the bony spinal canal (interpedicular distance), which was measured as the minimum distance between the medial surfaces of the pedicles of a given vertebra, was measured. In addition, the transverse diameter of the vertebral body, which was measured as the minimum distance across the waist of the vertebra, was measured. The distances were measured to the nearest one tenth of a millimetere using a Vernier caliper. At all levels (L1 - L5) the transverse diameters of the lumbar spinal canal were approximately 1 - 1.5 mm higher in males than in females. The intersegmental differences increased proximodistally, in both sexes. The ratio of the transverse diameter canal to the width of the vertebra ranged from 0.55 to 0.60 mm in both sexes. The distribution of the different lumbar canal types were 47% A, 42% B, 11% C. Additionally, subtypes were determined and classified.  相似文献   
52.
OBJECTIVE: To assess magnetic resonance imaging (MRI) findings in carpal tunnel syndrome (CTS) and to compare them with electrophysiological findings. METHODS: Routine motor and sensory nerve conduction examinations and needle EMG were performed in 42 hands of 22 patients, who were clinically diagnosed as having CTS in at least one wrist. RESULTS: Of 29 wrists with clinically and electrophysiologically confirmed CTS, MRI could detect abnormality in 18 wrists (62%). Median nerve was found to be abnormal in MRI in 1 of 2 wrists with suspected clinical symptoms and proven CTS by electrophysiological examination. MRI was abnormal in 1 of 4 wrists with normal clinical and electrophysiological examination. MRI was abnormal in 46, 7% of wrists with mild CTS, in 61.6% of moderate CTS and in 100% of severe CTS. Volar bulging of the flexor retinaculum was detected in a single wrist with severe CTS. Enlargement of median nerve was observed in 3 of 5 severe CTS. CONCLUSION: MRI could be useful in the diagnosis of unproven cases in CTS. It also provides anatomical information that correlate well with electrophysiological findings in regard of the severity of median nerve compression.  相似文献   
53.
Summary Kinematic variables of the vertical jump (jumping height, jump phase durations and joint angles) were measured on 39 male physical education students. In addition, kinetic parameters of the hip and knee extensors, and of the plantar flexors (maxima voluntary force and its rate of development) were recorded on the same subjects, in isometric conditions. The results demonstrated significant positive correlations between kinetic parameters of the active muscle groups and jumping height (r=0.217−0.464). The dominant effect on these correlations was due to the knee extensors. Correlations between these parameters and the duration of the jump phases were much weaker. Correlation coefficients between kinetic parameters and limb angles in the lowest body position showed that fast force production in one muscle group was related to a significant decrease in the joint angles of distant body segments. Multiple correlation coefficients between leg extensor parameters and kinematic variables (ranging between 0.256 for the duration of the counter-movement phase and 0.616 for jump height) suggested that kinetic parameters could explain more than a quarter of the variability of this complex human movement. Therefore, the conclusion was drawn that an extended set of measurements of the relevant musculo-skeletal system parameters could predict a considerable amount of the variability of human movement. However, high correlation coefficients between the same kinetic parameters of different muscle groups suggest that not all active muscle groups have to be included in the measurements.  相似文献   
54.
Seasonal changes in blood plasma biochemistry of siraz Capoeta capoeta umbla were determined throughout 1 year. In the present study, while the highest values for glucose and globulin were found in winter, the values for increased activities of total protein, albumin, calcium, sodium levels, albumin/globulin ratio, lactate dehydrogenase, and alkaline phosphatase were determined in summer. We determined that blood biochemistry values of siraz, which were positively affected by water temperature and pH, except glucose and globulin. Glucose and globulin were negatively affected by water temperature and pH. Consequently, it was concluded that the seasons are key factors when blood parameters are used as biomarkers for environmental alterations. It is difficult to define the most important factors affecting seasonal changes of blood biochemistry in fish.  相似文献   
55.
MethodsData on patients aged ≤19 years with a positive SARS-CoV-2 PCR test recorded in the period March 12-May 12 (first wave) and June 19-July 19, 2020 (second wave) were retrospectively analyzed. The periods were separated by several weeks with no incident cases.ResultsWe analyzed data on 289 children and adolescents (6.5% of all cases; incidence rate [IR] = 3.54, 95% confidence interval [CI] 3.14-3.97/million person-days), 124 in the first wave (IR = 2.27) and 165 in the second wave (IR = 6.37): IRR second/first = 2.71 (2.13-3.44). During the first wave, the incidence was highest in infants (IR = 3.48), while during the second wave it progressively increased to IR = 7.37 in 15-19-year olds. Family members were the key epidemiological contacts (72.6% cases), particularly during the first wave (95.8% vs 56.3%). Overall, 41.3% patients were asymptomatic, 25.3% in the first and 52.6% in the second wave. Age 15-19 years (vs younger) was associated with a higher (RR = 1.26, 1.02-1.54) and infection in the second wave with a lower probability (RR = 0.66, 0.53-0.81) of being symptomatic. The most common symptoms were fever, cough, and rhinorrhea. In children aged ≥7 years, headache, anosmia/ageusia, and sore throat were also recorded. Only one child suffered a severe disease. All but 18 (7.8%) children were treated only symptomatically, and all fully recovered.ConclusionA large proportion of SARS-CoV-2 PCR-positive children/adolescents were asymptomatic. The associated disease was predominantly mild, comparably so in the first and second pandemic wave.

Since the late December 2019, coronavirus disease 2019 (COVID-19) caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread quickly worldwide and as of early December accounts for more than 65 million cases diagnosed in more than 200 countries (1). At this point, the most affected countries in Europe are Russia, Spain, France, United Kingdom (UK), and Italy with consequently the highest mortality rates. The first case in Croatia was reported in the late February 2020, and within the next two months the infection expanded nationwide. During this first epidemic wave, Croatia was under a one-month lockdown, which rapidly decreased the disease incidence, and only a few newly diagnosed cases were reported between May 25 and June18, 2020. Easing of restrictions increased the incidence in late June, causing a second wave of COVID-19 in Croatia, with >147 000 cases reported so far (1,2).Over the last two decades, there were two other coronavirus outbreaks. Severe acute respiratory syndrome coronavirus appeared in 2002, affecting around 8000 people, with 10% mortality. Children (4 months-17 years) accounted for <0.02% of total cases, and there was no reported death in this age group. During the outbreak of the Middle East respiratory syndrome coronavirus, around 2300 people were infected, and children (<19 years of age) were rarely affected as well (2% of total cases; 2 reported deaths) (3,4). COVID-19 has exhibited a similar epidemiological pattern. Although early reports from China, Italy, and the United States (US) suggested that children and adolescents accounted for only 1%-2% of the overall COVID-19 cases (5-7), later reports around the world indicated a higher proportions of pediatric cases, between 1%-8% (8-10). Children of all ages can be affected by SARS-CoV-2 infection, but in contrast to other respiratory viruses, they usually suffer a mild or asymptomatic infection. Compared with adults, severe infections and fatal outcomes in children are rare, and several immunopathological mechanisms could be responsible for such differences in disease severity (11). Although many studies have reviewed the features of adults with COVID-19, overall data regarding pediatric cases are scarce, and most of them are reports from China and the US, with only a few studies describing disease in children from European countries.We aimed to describe epidemiological and clinical features of children and adolescents with COVID-19 confirmed by the polymerase chain reaction (PCR) test for SARS-CoV-2 in Croatia and to assess potential differences between the first (March-May 2020) and second (on-going) pandemic wave (June-July 2020).  相似文献   
56.
BACKGROUND: The aim of this study was to evaluate the effects of metformin and acarbose on insulin resistance, hormone profiles and ovulation rates in patients with clomiphene citrate-resistant polycystic ovary syndrome (PCOS). METHODS: Thirty clomiphene citrate-resistant patients were selected randomly and divided into two groups. Group I was treated with 100 mg/day clomiphene citrate and 300 mg/day acarbose 100 mg/day orally, for 3 months. Group II was treated with clomiphene citrate 100 mg/day and metformin 1700 mg/day orally, for 3 months. Serum fasting insulin and glucose, FSH, LH, estradiol, progesterone, prolactin and total testosterone levels plus body mass index (BMI) were measured before and after treatment. Follicle growth was followed by transvaginal ultrasonography. RESULTS: LH:FSH ratio and total testosterone concentrations decreased (P<0.05) and ovulation rates increased in both groups. Reduction in weight and BMI was only significant in the acarbose group. CONCLUSIONS: Both treatment modalities were effective in the treatment of insulin resistance and improving ovulation rates. Increase in the number of eumenorrhoeic and normoinsulinaemic cases and decrease in the number of insulin-resistant cases were significant in both groups (P<0.05). Ovulation rate was greater in the metformin group in the second month of therapy (P<0.05). Acarbose was found to be a safe and effective agent that could be used in cases with clomiphene-resistant PCOS.  相似文献   
57.
Rett syndrome is a severe neurodevelopmental disorder that arises from mutations in the X-linked MECP2 gene. It is almost exclusively seen in girls due to the predominant occurrence of the mutations on the paternal X-chromosome, and also the early postnatal lethal effect of the disease causing mutations in hemizygous boys. We identified a boy with features of classic Rett syndrome who is mosaic for the truncating MECP2 mutation R270X. Chromosome analysis showed normal karyotype. These results indicate that a MECP2 mutation associated with Rett syndrome in females could lead to a similar phenotype in males as a result of somatic mosaicism.  相似文献   
58.
Cadavers remain a principal teaching tool for anatomists and medical educators teaching gross anatomy. Infectious pathogens in cadavers that present particular risks include Mycobacterium tuberculosis, hepatitis B and C, the AIDS virus HIV, and prions that cause transmissible spongiform encephalopathies such as Creutzfeldt-Jakob disease (CJD) and Gerstmann-Straussler-Scheinker syndrome (GSS). It is often claimed that fixatives are effective in inactivation of these agents. Unfortunately cadavers, even though they are fixed, may still pose infection hazards to those who handle them. Specific safety precautions are necessary to avoid accidental disease transmission from cadavers before and during dissection and to decontaminate the local environment afterward. In this brief review, we describe the infectious pathogens that can be detected in cadavers and suggest safety guidelines for the protection of all who handle cadavers against infectious hazards.  相似文献   
59.
Several age-related alterations occur at the cellular level in the immune system leading to a decrease in the immune response. The present study was designed to determine the effect of L-carnitine on impaired neutrophil functions of aged rats. For this reason, superoxide anion radical production, chemotaxis and phagocytic activity were studied in the neutrophils obtained from the peripheral blood of young and old rats. We orally gavaged L-carnitine (50 mg/kg b.w. per day) or control vehicle into young (2 months) and aged (24 months) rats for 30 consecutive days. The neutrophils of aged rats exhibited an increase in superoxide anion production and decline in phagocytosis and chemotaxis when compared with that in young rat neutrophils. Superoxide anion production in aged rats was significantly decreased by L-carnitine treatment which was accompanied with a significant enhancement of chemotactic and phagocytic activity being restored to control levels. These findings demonstrated that L-carnitine is capable of restoring the age-related changes of neutrophil functions.  相似文献   
60.
Jitter analysis in single fiber EMG (SFEMG) is usually done on-line during recording. However, this technique frequently prolongs the study and makes re-analysis impossible. We attempted to measure jitter with a high speed FM tape recorder and compare the results with the previously published values. SFEMG data, acquired with voluntary activation on extensor digitorum communis muscle of 25 healthy relatives of children with myasthenia gravis were retrospectively analyzed. Fiber density (FD) was estimated on-line. Five to 18 single fiber action potential (SFAP) pairs were studied in each subject. The wow of the tape recorder was 6 microseconds. Mean (SD) (upper 95th percentile) FD, individual jitter, highest jitter, mean jitter and interspike interval were 1.60 (0.18) (1.90), 25.30 (11.20) (57.00) microseconds, 31.24 (6.87) (47.00) microseconds, 25.08 (5.04) (43.00) microseconds, and 0.67 (0.11) (0.91) ms respectively. Mean jitter in the pooled SFAP pairs and mean MCD were found to be lower than the published values of the Ad Hoc Committee of the AAEM Special Interest Group on Single Fiber EMG. A high speed FM tape recorder can be reliably used for the off-line analysis of jitter.  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