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   4493篇
  免费   250篇
  国内免费   11篇
耳鼻咽喉   24篇
儿科学   292篇
妇产科学   138篇
基础医学   463篇
口腔科学   103篇
临床医学   331篇
内科学   965篇
皮肤病学   93篇
神经病学   231篇
特种医学   120篇
外科学   707篇
综合类   92篇
一般理论   2篇
预防医学   199篇
眼科学   401篇
药学   391篇
中国医学   18篇
肿瘤学   184篇
  2023年   35篇
  2022年   77篇
  2021年   148篇
  2020年   76篇
  2019年   92篇
  2018年   156篇
  2017年   100篇
  2016年   103篇
  2015年   122篇
  2014年   181篇
  2013年   215篇
  2012年   359篇
  2011年   352篇
  2010年   189篇
  2009年   176篇
  2008年   269篇
  2007年   218篇
  2006年   203篇
  2005年   230篇
  2004年   207篇
  2003年   131篇
  2002年   117篇
  2001年   86篇
  2000年   72篇
  1999年   67篇
  1998年   29篇
  1997年   16篇
  1996年   24篇
  1994年   14篇
  1993年   20篇
  1992年   44篇
  1991年   50篇
  1990年   40篇
  1989年   41篇
  1988年   47篇
  1987年   36篇
  1986年   35篇
  1985年   17篇
  1984年   23篇
  1983年   16篇
  1982年   15篇
  1981年   19篇
  1979年   30篇
  1977年   15篇
  1975年   14篇
  1974年   17篇
  1973年   28篇
  1972年   35篇
  1971年   16篇
  1970年   27篇
排序方式: 共有4754条查询结果,搜索用时 31 毫秒
41.
Case records of the patients with major affective disorders (ICD-10 criteria), seen over a 5 year period in a busy clinic in North India were examined for Seasonal Affective Disorder (SAD) as per DSM-III-R criteria. In addition, seasonality of episodes of all affective disorders was also studied. Around 5.67% of the cases (n=44) retrospectively met the DSM-III-R criteria of SAD and predominant pattern was that of summer depression (n=18). There was also a consistent pattern of seasonal mania either in conjunction with seasonal depression (n=18) or in form of seasonal recurrent mania (n=11). None of the cases of depression showed any atypical vegetative features. In cases not meeting criteria for SAD (n=731), there was a trend for peaks for depressive episodes in winter followed by a smaller peak in summer months while manic episodes had peaks towards rainy and winter months. As compared to seasonal patterns of affective disorders in temperate zones, there was a general trend for opposite patterns of seasonality in SAD as well as in non-SAD. The findings are discussed in context of the climatic conditions of North India.  相似文献   
42.
Nonspecific cytotoxic cells (NCC) are the first identified and most extensively studied killer cell population in teleosts. NCC kill a wide variety of target cells including tumor cells, virally transformed cells and protozoan parasites. The present study identified a novel evolutionarily conserved oligodeoxynucleotide (ODN) binding membrane protein expressed by channel catfish (Ictalurus punctatus) NCC. Peptide fingerprinting analysis of the ODN binding protein (referred to as NCC cationic anti-microbial protein-1/ncamp-1) identified a peptide that was used to design degenerate primers. A catfish NCC cDNA library was used as template with these primers and the PCR-amplified product was sequenced. The translated sequence contained 203 amino acids (molecular mass of 22,064.63 Da) with characteristic lysine rich regions and a pI=pH 10.75. Sequence comparisons of this protein indicated similarity to zebrafish (51.2%) histone family member 1-X and (to a lesser extent) to trout H1. A search of EST databases confirmed that ncamp-1 is also expressed in various tissues of channel catfish as well as zebrafish. Inspection for signature repeats in ncamp-1 and comparisons with histone-like peptides from different species indicated the presence of multiple lysine based motifs composed of AKKA or PKK repeats. The novel protein was cloned, expressed in E. coli and the recombinant was used to generate rabbit anti-serum. The recombinant ncamp-1 bound GpC and CpG ODNs and was detected with homologous anti-ncamp-1 polyclonal antibodies. Western blots of NCC membranes using anti-ncamp-1 serum detected a 29 kDa protein. Binding competition experiments demonstrated that anti-ncamp-1 antibodies and GpC bound to the same protein on NCC. Two different truncated forms of ncamp-1 as well as the full-length recombinant protein exhibited anti-microbial activity. The present study demonstrated the expression by NCC of a new membrane protein that may participate in the recognition of bacterial DNA and as such participate in innate anti-microbial immune responses in teleosts.  相似文献   
43.
PurposeDespite advances in medical care, infective endocarditis (IE) has high mortality. Surgery for IE though recommended for complications of the disease is still not commonly offered due to conflicting reports in the literature. We reviewed our results of surgery for IE from the last 5 years to assess their outcome.MethodsA retrospective review from a single center of consecutive patients who underwent surgery for infective endocarditis from September 2014 to December 2019 was done. Data was collected from hospital records and follow-up done up to May 2020. Outcomes evaluated were mortality, follow-up survival, and postoperative complications. Factors affecting mortality and survival were analyzed.ResultsNinety-seven patients underwent surgery for IE during this period. Seventy-nine had native valve endocarditis (NVE) and 18 had prosthetic valve endocarditis (PVE). The overall postoperative mortality was 13%, with mortality for native valve endocarditis being 11% and that for prosthetic valve endocarditis being 22%, which was not statistically significant. Three-year survival for the overall group was 88.7% with 88.1% for NVE and 91.7% for PVE. Multivariate predictors of operative mortality were a high EuroSCORE II, diabetes mellitus, and the presence of Staphylococcus organism.ConclusionSurgery for infective endocarditis has a very acceptable early outcome and intermediate-term survival.  相似文献   
44.
AimsTo evaluate vitamin D3 levels in patients who presented with increased musculo-skeletal pain after release of lockdown period when compared to pre-lockdown status.IntroductionDuring this COVID pandemic, many countries have implemented lockdown measures and people have to work from home and many students and workers have to restrict themselves to home. During this period, their outdoor activities were limited. After the partial release of this lockdown many of them started to have some kind of physical activity and started experiencing body pains. We evaluated such patients for vitamin D3 levels and symptoms of fibromyalgia.MethodsThis is a retrospective analysis of patients from age group 18–60 presented to outpatient department or on telephonic consultation after partial release of lockdown. All patients who had mild back ache before lockdown and had symptoms exaggerated during this lockdown release were included. All patients were investigated for vitamin D3, PTH, thyroid profile, liver functional and kidney functional tests.ResultsOut of 120 patients presented to us in a period of 3 months, 31 patients had increased symptoms when compared to pre-lockdown status. 20 out of 31 patients had low vitamin D3 levels. 14 patients also developed symptoms of fibromyalgia.ConclusionThere might be many reasons for increased pain during lockdown, but we focussed specially only on vitamin D3 because of its association with increased symptoms of COVID-19. This is a gentle reminder to test for vitamin D3 levels and supplement if found deficient.Supplementary InformationThe online version contains supplementary material available at 10.1007/s43465-021-00376-8.  相似文献   
45.
Previous studies from this laboratory demonstrated that 2,6-bis-([3,4-dihydroxyphenyl]methylene)cyclohexanone (BDHPC) and related compounds mimic methyl p-hydroxyphenyllactate (MeHPLA) as endogenous ligands for nuclear type II [H-3]estradiol binding sites. Occupancy of type II sites by these agents results in the inhibition of malignant cell proliferation in vitro and mammary tumor growth in vivo. The present studies were designed to assess the effects of BDHPC esterification on type II site binding interactions in uterine nuclei and in cultured MCF-7 human breast cancer cells in vitro. The results of these experiments demonstrate that in rat uterine nuclear fractions BDHPC acetate (Kd approximately 100 nM) interacts with type II sites with a 100-fold lower affinity than BDHPC (Kd approximately 0.9 nM) and BDHPC benzoate failed to inhibit [H-3]estradiol binding under these experimental conditions. Conversely, BDHPC and BDHPC acetate displayed very similar binding affinities for type II sites in cultured MCF-7 human breast cancer cells and there was a direct correlation between nuclear type II site occupancy and the inhibition of cellular proliferation by these two compounds. BDHPC benzoate failed to interact with type II sites or inhibit MCF-7 cell proliferation. Taken together, these results suggested that BDHPC acetate, but not BDHPC benzoate, was being hydrolyzed by esterases in MCF-7 cells, releasing the free parent compound. This conclusion was supported by the observations that incubation of BDHPC acetate in mammary tumor cytosol preparations resulted in essentially quantitative hydrolysis to BDHPC as determined by thin layer chromatography (TLC) and by high performance liquid chromatography (HPLC) analysis of tumor cytosol extracts. Conversely, BDHPC benzoate was not hydrolyzed by tumor esterases which is consistent with the inability of this compound to bind to type II sites or inhibit MCF-7 human breast cancer cell proliferation. These experiments confirm and extend the hypothesis that esterase hydrolysis of MeHPLA related compounds represents an important biological step involved in the control of the biological activity of type II site agonists which appear to regulate malignant cell proliferation through this binding interaction.  相似文献   
46.
The present paper describes a laboratory experiment in which raters evaluated the videotaped performance of ratees who did or did not have a disability. This disability was stereotypically either a poor fit with the job in question or not. The results indicated that actual appraisals were not influenced by stereotypes about fit or by disabilities, but that expectations concerning future performance and a number of other decisions and recommendations were influenced by this perceived fit. These results suggest that people do hold clear stereotypes about what types of disabilities lead to poor performance on a given job, and that these stereotypes are relied upon for certain personnel decisions, even in light of performance evidence that suggests that these stereotypes are invalid. Employees' disabilities may not influence supervisors' evaluations of their past performance when supervisors have clear objective performance information available. However, bias still exists in expectations for future performance and training recommendations. This bias can have severe long-term consequences on one's career within an organization. The scenario is worse when one's disability is stereotypically believed to be unsuitable to the job in question.  相似文献   
47.
48.
OBJECTIVES: The diagnosis of Alzheimer's disease (AD) is now reliant on the use of NINCDS-ADRDA criteria. Other diseases causing dementia are being increasingly recognised--for example, frontotemporal dementia (FTD). Historically, these disorders have not been clearly demarcated from AD. This study assesses the capability of the NINCDS-ADRDA criteria to accurately distinguish AD from FTD in a series of pathologically proved cases. METHODS: The case records of 56 patients (30 with AD, 26 with FTD) who had undergone neuropsychological evaluation, brain imaging, and ultimately postmortem, were assessed in terms of whether at initial diagnosis the NINCDS-ADRDA criteria were successful in diagnosing those patients who had AD and excluding those who did not. RESULTS: (1) The overall sensitivity of the NINCDS-ADRDA criteria in diagnosing "probable" AD from 56 patients with cortical dementia (AD and FTD) was 0.93. However, the specificity was only 0.23; most patients with FTD also fulfilled NINCDS-ADRDA criteria for AD. (2) Cognitive deficits in the realms of orientation and praxis significantly increased the odds of a patient having AD compared with FTD, whereas deficits in problem solving significantly decreased the odds. Neuropsychological impairments in the domains of attention, language, perception, and memory as defined in the NINCDS-ADRDA statement did not contribute to the clinical differentiation of AD and FTD. CONCLUSION: NINCDS-ADRDA criteria fail accurately to differentiate AD from FTD. Suggestions to improve the diagnostic specificity of the current criteria are made.  相似文献   
49.
OBJECTIVE: To report the longer term results of a randomized, clinical trial comparing the 350-mm2 and the 500-mm2 Baerveldt glaucoma implants. DESIGN: Extended follow-up on a randomized, controlled trial. PARTICIPANTS: Between March 1991 and April 1993, 107 patients with uncontrolled intraocular pressure (IOP) due to non-neovascular glaucoma associated with aphakia, pseudophakia, or failed filters were randomly assigned for surgical placement of either the 350-mm or the 500-mm2 Baerveldt implant at the Doheny Eye Institute. METHODS: A random-numbers table was used to assign each patient to one of the two groups. Preoperative IOPs and visual acuities were recorded. Clinical records were reviewed to ascertain postoperative IOPs, visual acuities, number of medications used, and implant-related complications that occurred throughout the follow-up period. MAIN OUTCOME MEASURES: Success was defined as IOP of 6 mmHg or greater and of 21 mmHg or less in two or more consecutive follow-up visits without further glaucoma surgery or loss of light perception attributable to glaucoma. RESULTS: The overall success rates were 87% for the 350-mm2 group and 70% for the 500-mm2 group (P = 0.05). Average follow-up was 37 months (range, 1-76 months) for the 350-mm2 group and 34 months (range, 5-77 months) for the 500-mm2 group. The life-table success rates declined over time for both implant groups, from a high of 98% for the 350-mm2 group and 92% for the 500-mm2 group at 1 year to a cumulative success rate of 79% for the 350-mm2 group and 66% for the 500-mm2 group at 5 years. Visual acuities were better or remained the same in 50% of the patients in the 350-mm2 group and 46% of those in the 500-mm2 group. Complications during the 5-year follow-up were also statistically similar. CONCLUSIONS: The longer term results show that the 350-mm2 Baerveldt implant is more successful than the 500-mm2 implant for overall IOP control. Interval comparisons indicate a higher rate of success for the 350-mm2 implant in the first, second, third, fourth, and fifth years of implantation. Visual acuities, implant-related complications, and average IOPs were statistically indistinguishable between the two groups.  相似文献   
50.
We reviewed the pattern of involvement of the calvarium by tuberculosis (TB) in five patients and the role of imaging in its management. Four patients presented with localised scalp swelling and one with generalized seizures. Radiographs revealed lucent lesions with minimal surrounding sclerosis in the frontal (2), parietal (2) and occipital (1) bones. CT showed lesions involving the entire thickness of the calvarium and accompanying contrast-enhancing soft tissue. The patient presenting with seizures had a ring-enhancing lesion in the parietal lobe in addition to the extra-axial lesions. Although radiographs in all cases demonstrated calvarial TB, CT showed the extent of the defect, involvement of adjacent soft tissues, and in one case an intra-axial lesion. Radiographs suffice for follow-up of these patients. Received: 23 July 1999 Accepted: 20 September 1999  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