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   1733篇
  免费   75篇
  国内免费   2篇
耳鼻咽喉   33篇
儿科学   26篇
妇产科学   14篇
基础医学   195篇
口腔科学   24篇
临床医学   195篇
内科学   346篇
皮肤病学   24篇
神经病学   120篇
特种医学   72篇
外科学   467篇
综合类   10篇
预防医学   138篇
眼科学   3篇
药学   49篇
肿瘤学   94篇
  2021年   11篇
  2020年   16篇
  2019年   17篇
  2018年   27篇
  2017年   14篇
  2016年   20篇
  2015年   21篇
  2014年   30篇
  2013年   64篇
  2012年   63篇
  2011年   67篇
  2010年   29篇
  2009年   45篇
  2008年   84篇
  2007年   88篇
  2006年   72篇
  2005年   73篇
  2004年   74篇
  2003年   83篇
  2002年   64篇
  2001年   44篇
  2000年   62篇
  1999年   49篇
  1998年   25篇
  1997年   15篇
  1996年   22篇
  1995年   19篇
  1994年   24篇
  1993年   25篇
  1992年   41篇
  1991年   43篇
  1990年   44篇
  1989年   26篇
  1988年   39篇
  1987年   26篇
  1986年   34篇
  1985年   28篇
  1984年   23篇
  1983年   22篇
  1982年   17篇
  1980年   11篇
  1979年   28篇
  1978年   17篇
  1977年   14篇
  1976年   17篇
  1974年   15篇
  1973年   15篇
  1972年   12篇
  1971年   10篇
  1967年   19篇
排序方式: 共有1810条查询结果,搜索用时 15 毫秒
31.
p53 overexpression was present in the normal or dysplastic epithelium, but absent in the adjacent invasive cancers of five patients with head and neck squamous cell carcinomas (HNSCC), when p53 immunostaining (IHC) was performed. In three of the five p53 immunoreactive dysplasias and adjacent p53 negative invasive cancers single stranded conformation polymorphism (SSCP) results from exon 7 and 8 were also obtained. Bandshifts in exon 7 were detected in two dysplasias, and bandshifts in exon 8 were found in a third. Sequencing of exon 7 in the first dysplasia with bandshift indicated a deletion of codon 241-242 (loss of CT) resulting in a frame shift. In the second dysplasia with bandshift a mutation was observed in codon 244 resulting in a Gly-->Arg substitution in the protein sequence. In the adjacent IHC p53 negative invasive cancer lesions, no bandshifts could be observed by SSCP, and sequencing did not reveal any mutated p53. WAF1/p21 (IHC) expression was assayed to study p53 function. Image cytometry (ICM) DNA analysis, estimating genetic instability, showed progress in DNA aberration for invasive cancer lesions as compared with the dysplasias. Human papillomavirus (HPV DNA) was not detected by a polymerase chain reaction (PCR) in any of the five cancers thus excluding possible p53 degradation caused by HPV protein. In conclusion, the finding of p53 mutations in mild, moderate, and severe dysplasia indicates that p53 mutation, not only p53 immunoreactivity, can be an early event in HNSCC carcinogenesis. The lack of p53 immunoreactivity in the invasive cancers adjacent to p53 positive dysplasias could possibly be attributed to loss of the mutant allele, or clonal heterogeneity.  相似文献   
32.
33.
In a retrospective analysis of 91 consecutive oral carcinomas we reviewed all patient records and weighed clinicopathological parameters against the results of image DNA cytometry and p53 immunhistochemical staining of the initial diagnostic biopsies. Eighty-seven percent of the biopsies were either aneuploid or nondiploid and there was a significant correlation between poorly differentiated tumours and aneuploidy. Sixty-nine percent of the tumours were p53 positive. DNA aberration or p53 positivity had no significant impact on prediction of survival or susceptibility to radiotherapy. In a multivariate analysis, T category had the greatest predictive value concerning survival. There was no correlation between p53 positivity and smoking.  相似文献   
34.
We examined the nutritional status of 224 patients from six centers in Europe and North America to assess the incidence of protein-energy malnutrition. A "subjective nutritional assessment" was made, using 21 variables derived from history and clinical examination, or anthropometry and biochemistry. Eighteen patients (8%) were severely malnourished, 73 (32.6%) were mildly to moderately malnourished, and 133 (59.4%) did not show evidence for malnutrition. There was a higher incidence of mild to moderate malnutrition in diabetics than in nondiabetics. A statistical analysis identified 12 variables, seven objective and five subjective, that correlated with subjective nutritional assessment. Actual intercenter differences for the incidence of malnutrition were related to patient age, nutritional status at the commencement of continuous ambulatory peritoneal dialysis (CAPD), the length of time on CAPD, and residual renal function. Variables that were most frequently correlated with subjective nutritional assessment and with one another included plasma albumin, mid-arm muscle circumference (MAMC), weight loss, and the clinical judgement of muscle wasting and loss of subcutaneous fat. Loss of residual renal function correlated with muscle wasting and months on CAPD. Our data identified differences between the two sexes. In women there was a trend for more anorexia, greater weight loss from muscle wasting, and a larger decrease in albumin, whereas in men there was a more gradual decrease in nutritional status. Loss of residual renal function contributed to anorexia and symptoms of severe malnutrition.  相似文献   
35.
PURPOSE: The purpose is to evaluate relationships between objectively assessed exercise capacity and subjectively assessed scoring of physical functioning and well-being after erythropoietin treatment in cancer patients on palliative care. EXPERIMENTAL DESIGN: Unselected cancer patients (n = 108) who experienced progressive cachexia were randomized to receive either anti-inflammatory treatment alone (indomethacin) or recombinant erythropoietin plus indomethacin to prevent the appearance of disease-induced anemia and thereby protect patients' exercise capacity. Follow-up investigations of nutritional status, exercise capacity, and health-related quality of life assessed by SF-36 and the European Organization for Research and Treatment of Cancer QLQ-C30 were compared. RESULTS: Effective treatment by erythropoietin on top of basal whole body anti-inflammatory treatment was confirmed and indicated by time course changes of biochemical, physiologic, and nutritional objectives, whereas individual self-reported scoring of physical functioning and general health did not indicate a clear-cut effectiveness, particularly at moderately subnormal hemoglobin levels. CONCLUSIONS: Discrepancies between objective and subjective self-reported measures may be either fundamental or indicate scoring limitations for evaluation of therapeutic results. Present results demonstrate a clinical benefit of erythropoietin treatment in cancer patients with subnormal to normal hemoglobin levels, whereas the patients' own subjective scoring was insufficient to sense such improvements. The discrepancy may be either fundamental or methodological but emphasizes the importance to document therapeutic outcome in both subjective and objective perspectives in palliative care of cancer patients.  相似文献   
36.
A systematic assessment of radiotherapy for cancer was conducted by The Swedish Council on Technology Assessment in Health Care (SBU) and published in 1996. The assessment reviewed the scientific literature up to 1993 on the use of radiotherapy in the treatment of solid tumours, and estimated the costs associated with radiotherapy. It also described the current practise of radiotherapy in Sweden 1992 and compared practise with scientific knowledge. The SBU has now conducted a follow-up study on radiotherapy for cancer, including a review of the scientific literature from 1994 and a prospective survey of radiotherapy practise in Sweden 2001. The following conclusions were drawn: The role of radiotherapy as an important form of treatment for cancer with both curative and palliative intent has been further confirmed.The use of radiotherapy in Sweden has increased and is now at the internationally recommended level.Radiotherapy in Sweden is mostly given in accordance with the scientific evidence but may still be underutilized in certain situations.The resources for radiotherapy are being utilized more efficiently.The costs of radiotherapy are still 5% of the total cost of cancer care, while the cost of an individual treatment (fraction) has decreased.The need for radiotherapy capacity will increase. In addition, half of the treatment equipment will have to be replaced in the next few years.  相似文献   
37.
Diabetes mellitus is commonly considered as a disease of a scant beta-cell mass that fails to respond adequately to the functional demand. Tyrosine kinases may play a role for beta-cell replication, differentiation (neoformation) and survival. Transfection of beta-cells with DNA constructs coding for tyrosine kinase receptors yields a ligand-dependent increase of DNA synthesis in beta-cells. A PCR-based technique was adopted to assess the repertoire of tyrosine kinases expressed in fetal islet-like structures, adult islets or RINm5F cells. Several tyrosine kinase receptors, such as the VEGFR-2 (vascular endothelial growth factor receptor 2) and c-Kit, were found to be present in pancreatic duct cells. Because ducts are thought to harbor beta-cell precursor cells, these receptors may play a role for the neoformation of beta-cells. The Src-like tyrosine kinase mouse Gtk (previously named Bsk/Iyk) is expressed in islet cells, and was found to inhibit cell proliferation. Furthermore, it conferred decreased viability in response to cytokine exposure. Shb is a Src homology 2 domain adaptor protein which participates in tyrosine kinase signaling. Transgenic mice overexpressing Shb in beta-cells exhibit an increase in the neonatal beta-cell mass, an improved glucose homeostasis, but also decreased survival in response to cytokines and streptozotocin. It is concluded that tyrosine kinase signaling may generate multiple responses in beta-cells, involving proliferation, survival and differentiation.  相似文献   
38.
PURPOSE: To study the kinetics of chromosomal break rejoining and exchange formation in human G0 and G2 lymphocytes after low-LET irradiation using the premature chromosome condensation (PCC) technique. METHODS: For the G0 experiments, isolated human lymphocytes were irradiated (1, 3 and 8 Gy) and immediate and delayed fusions (1, 3, 5, 8 and 24 h) were performed with CHO-cells, and 48-h cultures were set up simultaneously. Interphase and metaphase human chromosomes were hybridized with dual colour combination probes for chromosomes 2 and 4. For the G2 experiments, isolated lymphocytes from the same donor were cultured for 69 h, irradiated with 3 Gy 60Co gamma rays and fused with CHO cells immediately and after 1, 2 and 3 h. Chromatid breaks and exchanges were scored after Giemsa staining. RESULTS: In both G0 and G2 cells, exchanges were already observed at the first fusion and, at lower doses, their frequencies remained relatively stable over time. The exchange-type aberrations seen in G0 cells were mostly incomplete, especially in the first fusions, while the exchanges seen in metaphase were mostly complete. The frequency of complete exchanges increased by time during incubation, while the frequency of incomplete exchanges showed more variation and a general decline by time in the G0-PCC experiment. The number of breaks declined rapidly by time both in G0 and G2. The break rejoining rate was higher at 8 Gy than in the two lower doses in the G0-PCC. The overall aberration frequencies in G0 and G2 cells studied by PCC were higher than in the corresponding metaphase. The initial number of breaks in G2 was higher than in G0 and the break rejoining rate in the G2 was two-fold. CONCLUSIONS: The formation of complete exchanges in G0 is a delayed process. The incomplete exchanges appear unstable in G0. The decreasing proportion of incomplete exchanges and simultaneous increase in complete exchanges in G0-PCC indicates that formation of exchanges is not coordinated in time.  相似文献   
39.
The aim of this study was to investigate if sensory stimulation in the form of manual acupuncture could influence urge- or mixed-type incontinence among elderly women who were not satisfactorily relieved by standard pharmacological and non-pharmacological treatments given at a specialised incontinence unit. The study is an open clinical follow-up study. The study included 15 elderly women who were treated with manual acupuncture 12 times. Both subjective scorings and objective measurements in the form of leakage in grams (48 h Inco-test) were used. Evaluations were performed at discharge and 1 and 3 months thereafter. Almost all outcome measurements were significantly improved even at follow-up 3 months after the last treatment. Global scorings showed that 12 of the 15 women considered themselves improved even at the follow-up 3 month after treatments were completed. The possible mechanisms of action are discussed, as is the way to perform more studies in this field.  相似文献   
40.
The aims of this study were to assess the prevalence of temporomandibular joint related (TMJ) painless symptoms, orofacial pain, neck pain, and headache in a Finnish working population and to evaluate the association of the symptoms with psychosocial factors. A self-administered postal questionnaire concerning items on demographic background, employment details, perceived general state of health, medication, psychosocial status, and use of health-care services, was mailed to all employees with at least 5 years at their current job. The questionnaire was completed by 1339 subjects (75%). Frequent (often or continual) TMJ-related painless symptoms were found in 10%, orofacial pain in 7%, neck pain in 39%, and headache in 15% of subjects. Females reported all pain symptoms significantly more often than men (P < 0.001). Frequent pain and TMJ-related symptoms were significantly associated with self-reported stress, depression, and somatization (P < 0.001). Perceived poor general state of health (P < 0.001), health care visits (P < 0.001), overload at work (P < 0.001), life satisfaction (P < 0.05), and work satisfaction (P < 0.05) were also significantly associated with pain symptoms, but the work duty was not (P > 0.05). Our findings are in accordance with earlier studies and confirm the strong relationship between neck pain, headache, orofacial pain, TMJ-related painless symptoms, and psychosocial factors. Furthermore, TMJ-related symptoms and painful conditions seem to be more associated with work-related psychosocial factors than with type of work itself.  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