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   6677篇
  免费   483篇
  国内免费   33篇
耳鼻咽喉   97篇
儿科学   111篇
妇产科学   101篇
基础医学   1175篇
口腔科学   65篇
临床医学   709篇
内科学   1376篇
皮肤病学   154篇
神经病学   620篇
特种医学   368篇
外科学   816篇
综合类   35篇
一般理论   2篇
预防医学   375篇
眼科学   119篇
药学   515篇
中国医学   16篇
肿瘤学   539篇
  2023年   26篇
  2022年   90篇
  2021年   160篇
  2020年   74篇
  2019年   126篇
  2018年   155篇
  2017年   127篇
  2016年   164篇
  2015年   212篇
  2014年   227篇
  2013年   302篇
  2012年   423篇
  2011年   475篇
  2010年   275篇
  2009年   325篇
  2008年   466篇
  2007年   429篇
  2006年   466篇
  2005年   434篇
  2004年   449篇
  2003年   408篇
  2002年   341篇
  2001年   110篇
  2000年   78篇
  1999年   66篇
  1998年   77篇
  1997年   67篇
  1996年   43篇
  1995年   42篇
  1994年   36篇
  1993年   26篇
  1992年   31篇
  1991年   31篇
  1990年   29篇
  1989年   30篇
  1988年   23篇
  1987年   25篇
  1986年   32篇
  1985年   22篇
  1984年   10篇
  1983年   14篇
  1982年   26篇
  1981年   13篇
  1979年   12篇
  1978年   17篇
  1975年   9篇
  1974年   13篇
  1973年   10篇
  1972年   10篇
  1903年   9篇
排序方式: 共有7193条查询结果,搜索用时 31 毫秒
91.
Tissue sections taken from 157 potentially curatively operated lung carcinoma patients (70 epidermoid carcinomas, 68 adenocarcinomas, 15 large cell anaplastic, and 4 small cell anaplastic carcinomas) were examined by a standardized histochemical protocol in a prospective study evaluating the extent of various types of probes to serve as prognostic indicators in lung cancer. Detailed clinical records and survival data (minimum 56 weeks, maximum 96 weeks) were correlated to the results of the histochemical reactions. The study centres on monitoring the expression of galactoside-containing epitopes in tumor cells by human, animal and plant lectins: and with a monoclonal antibody. In addition, affinity-purified subfractions of natural antibodies from human serum with preferential affinity to alpha- and beta-galactosides, respectively, were employed. Significant contributions to the estimation of the survival of patients are given by clinical parameters (pT, pN stage), number of resected and positive lymph nodes and presence of tumor metastases into specific lymph nodes (No. 5 and No. 6 right and left). With respect to the relevance of subsets of beta-galactosides, the galectin from chicken liver (CL-16) and the Le(y)-specific monoclonal antibody unveiled a negative correlation at a statistically significant level. The predictive value of binding of the animal lectin CL-16 was especially pronounced for patients with advanced tumor stages, pointing to a potential role of such lectin-reactive beta-galactosides in late tumor stages or progression.  相似文献   
92.
Whole-body fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging was performed during the follow-up of 33 patients suffering from differentiated thyroid cancer. Among them there were 26 patients with papillary and seven with follicular tumours. Primary tumour stage (pT) was pT1 in six cases, pT2 in eight cases, pT3 in three cases and pT4 in 14 cases. FDG PET was normal in 18 patients. In three patients a slightly increased metabolism was observed in the thyroid bed, assumed to be related to remnant tissue. In one case local recurrence, in ten cases lymph node metastases (one false-positive, caused by sarcoidosis) and in three cases distant metastases were found with FDG PET. In comparison with whole-body scintigraphy using iodine-131 (WBS) there were a lot of discrepancies in imaging results. Whereas three patients had distant metastases (proven with131I) and a negative FDG PET, in four cases131I-negative lymph node metastases were detectable with PET. Even in the patients with concordant staging, differences between131I and FDG were observed as to the exact lesion localization. Therefore, a coexistence of131I-positive/FDG-negative,131I-negative/FDG-positive and131I-positive/FDG-positive malignant tissue can be assumed in these patients. A higher correlation of FDG PET was observed with hexakis (2-methoxyisobutylisonitrile) technetium-99m (I) (MIBI) scintigraphy (performed in 20 cases) than with WBS. In highly differentiated tumours131I scintigraphy had a high sensitivity, whereas in poorly differentiated carcinomas FDG PET was superior. The clinical use of FDG PET can be recommended in all cases of suspected or proven recurrence and/or metastases of differentiated thyroid cancer and is particularly useful in cases with elevated serum thyroglobulin levels and negative WBS.  相似文献   
93.
Summary It has been hypothesized that chronic hypobaric hypoxia could lead to inhibition of the-motoneuron pool, thus limiting the maximal activation of working skeletal muscles. To test this hypothesis six subjects [32 (SEM 2) years] were evaluated in resting conditions, at sea level and after acclimatization at 5,050 m. The recruitment curves of the Hofmann-reflex (H-) and the direct muscle-response (M-) of the right soleus muscle were obtained by stimulating the posterior tibeal nerve with different intensities while recording the electromyogram of the soleus muscle. From the recorded data the net-motoneuron excitability (ratio of maximal H-reflex to M-response Hmax : Mmax ratio), the threshold and gain for both responses, obtained from linear regressions through the rising phase of the recruitment curves of both responses, as well as the latency times of both responses were determined. The latency times and the Hmax :Mmax ratio were unchanged at altitude. The thresholds of both responses and the gain of the M-response were unaltered. The gain of the H-response was significantly higher at altitude when compared to sea level. It is concluded that in the acclimatized subjects at rest the signal conduction velocity through the different parts of both pathways was unaltered and therefore nerve and muscle conduction velocity as well as synaptic and muscle end-plate transmission were unchanged, that the recruitment of the H-reflex was slightly facilitated after acclimatization to high altitude suggesting increased excitability of the-motoneurons, through either postsynaptic facilitatory changes in the soma or a different descending drive, and that the unchanged Hmax:Mmax ratio indicated no change in the net excitatory and inhibitory influences on the-motoneuron pool. The above hypothesis is thus not strengthened by the results that were, however, obtained in resting conditions.  相似文献   
94.
Histopathological images were transferred by use of normal telephone lines between three pathology institutes located in three different cities in the FRG. Images were digitized using a colour TV camera and stored in a special computerized image transmission system. The stored image was transferred and visualized on a (receiver) colour TV screen after dialing the telephone number connected to the receiver image transmission system. An additional telephone dialogue was activated by use of a normal acoustic telephone, and the diagnostic difficulties of the underlying image were discussed. Diagnostic assistance was possible in all transferred cases as well as histopathological diagnosis. Resolution of the images was set at 512 x 512 pixel x 8 bit. Image transfer time was 3.2 min on average. The differences between the original and transferred image were measured by "retransfer" of the original image and by subtracting the two images from each other. No major transfer errors could be measured.  相似文献   
95.
A technique is described which permits the detection of platelet-specific, noncomplement-fixing ("blocking') PlA1 antibodies in serologically negative sera of mothers from children suffering from neonatal alloimmune thrombocytopenia. The technique consists of (1) antibody enrichment in eluates prepared from maternal serum and PlA1-positive platelets, and (2) quantitation of antibodies in eluates by the platelet radioactive anti-IgG test. With this assay, PlA1 antibodies were demonstrated in 6 out of 7 maternal sera, and anti-A antibodies in one. It proved valuable also for longitudinal studies for periods up to 30 months after delivery.  相似文献   
96.
Zusammenfassung Bei Hunden mit experimentellem Verschluß der Arteria mesenterica superior kommt es zu einem deutlichen Anstieg der Serotonin-, Kinin-und Katecholaminkonzentrationen im Pfortaderblut, zu einem Anstieg der Prostaglandin F2-Konzentration, aber nur unmittelbar nach Anlegen oder Wiedereröffnung des Verschlusses.Unsere experimentellen Ergebnisse machen es unwahrscheinlich, daß diese genannten Substanzen für die Entwicklung von Erosionen oder Ulcera, wie sie nach Verschluß der Arteria mesenterica superior beobachtet werden, ursächlich verantwortlich sind, da diese pharmakologisch aktiven Substanzen letztlich zu geringe Konzentrationserhöhungen erfahren. Andererseits ist eine mögliche additive Wirkung dieser unterschwelligen Konzentration von Serotonin, Kinin und Katecholamin nicht mit Sicherheit auszuschließen.
The demonstration of pharmacological active substances in the portal vein blood of dogs after occlusion of the superior mesenteric artery
Summary The experimental occlusion of the superior mesenteric artery in dogs is followed by a significant rise of serotonin-, kinin- and katecholamin-concentrations in the portal vein blood. The rise of the prostaglandin-F2-concentration occurred only immediately after the occlusion or reopening of the occluded superior mesenteric artery.Under our experimental conditions the measured concentrations of these substances in the portal vein blood are too low and ineffective for the development of peptic erosions in the stomach as observed after occlusion of the superior mesenteric artery. On the other hand a possible additiv effect of the underswelling concentrations in these different substances cannot be excluded.
  相似文献   
97.
Polymorphisms of genes coding for DNA repair can affect lung cancer risk. A common single nucleotide (-4) G-to-A polymorphism was identified previously in the 5' untranslated region of the XPA gene. In a case-control study in European Caucasians, the influence of this polymorphism on primary lung cancer risk overall and according to histologic subtypes was investigated. Four hundred sixty-three lung cancer cases (including 204 adenocarcinoma and 212 squamous cell carcinoma) and 460 tumor-free hospital controls were investigated using PCR amplification and melting point analysis of sequence-specific hybridization probes. Odds ratios (OR) were calculated by multiple logistic regression analysis adjusting for age, gender, smoking habits, and occupational exposure and showed a slightly enhanced risk for all lung cancer cases as well as for squamous cell carcinoma and adenocarcinoma cases. Gene-environment interactions were analyzed with respect to smoking and occupational exposure. A nearly 3-fold increased risk for adenocarcinoma associated with the XPA AA genotype was observed for occupationally exposed individuals (OR, 2.95; 95% confidence interval, 1.42-6.14) and for heavy smokers (OR, 2.52; 95% confidence interval, 1.17-5.42). No genotype-dependent increase in OR was found for nonexposed individuals or those smoking <20 pack-years. The significant effect of the XPA polymorphism in heavy smokers and occupationally exposed individuals suggests an important gene-environment interaction for the XPA gene. The underlying mechanisms as to why AA homozygotes are predisposed to lung adenocarcinoma and which specific carcinogens are involved remains to be determined.  相似文献   
98.
PURPOSE: Amplification of the MYCN oncogene at chromosome 2p24-25 identifies an aggressive subtype of human neuroblastoma with a poor clinical outcome. Differences in amplicon structure and coamplification of genes telomeric and centromeric to the MYCN oncogene have previously been described. A relevant role of gene coamplification for neuroblastoma pathogenesis remains elusive. PATIENTS AND METHODS: We analyzed 98 primary neuroblastoma tumors with MYCN amplification for coamplification of seven additional genes at chromosome 2p24-25 (DDX1, NAG, NSE1, LPIN1, EST-AA581763, SMC6, and SDC1). Two semiquantitative multiplex polymerase chain reactions were used to obtain the amplification status of the target genes in relation to a reference gene on chromosome 2q (Inhibin-beta-b). Furthermore, mRNA expression pattern of coamplified genes in a subset of tumors was analyzed. RESULTS: Our results show that the frequency of gene coamplification on 2p24-25 in neuroblastoma is correlated directly to the physical distance to MYCN. Coamplification is correlated to an upregulated gene expression for DDX1 and NAG. Coamplification of the DDX1 gene within 400kb telomeric to MYCN identifies a subgroup of advanced stage neuroblastoma tumors with a more favorable outcome (P =.027, log-rank test). A high expression level of DDX1 is associated with a trend towards a better survival probability (P =.058, log-rank test). CONCLUSION: Our results indicate that DDX1 coamplification correlates with a better prognosis and improved patient survival in MYCN-amplified neurobastoma.  相似文献   
99.
PURPOSE: The objective of the study was to evaluate microsatellite alterations [microsatellite instability (MSI) and loss of heterozygosity (LOH)] and mutation in the p53 gene in relation to response and patient survival to a cisplatin-based neoadjuvant chemotherapy in gastric cancer. EXPERIMENTAL DESIGN: Fifty-three pretherapeutic gastric carcinoma biopsies were analyzed with 11 microsatellite markers. The entire coding region of the p53 gene (exons 2-11) was analyzed for mutations by denaturing high-pressure liquid chromatography and sequencing. p53 protein expression was evaluated by immunohistochemistry. Patients were treated with a cisplatin-based, neoadjuvant chemotherapy regimen. Therapy response was evaluated by computed tomography scan, endoscopy, and endoluminal ultrasound. The median follow-up of the patients was 45.6 months. RESULTS: p53 mutations were identified in 19 of the 53 (36%) analyzed tumors. No significant association with response or survival was found for p53 mutation or for p53 protein expression. MSI (either high-grade MSI or low-grade MSI) did not show a correlation with response. With respect to LOH, LOH at chromosome 17p13 showed a significant association with therapy response (P = 0.022) but did not reach statistical significance in terms of patient survival. The global LOH rate, expressed as fractional allelic loss (FAL), was assessed, and tumors were classified into tumors with a high (>0.5), medium (>0.25-0.5), and low (0-0.25) FAL value. A statistically significant association of FAL with therapy response was found (P = 0.003), with a high FAL being related to therapy response. The sensitivity, specificity, positive predictive value, and negative predictive value for FAL > 0.5 were 45%, 93%, 82%, and 72%, respectively. CONCLUSIONS: A high level of chromosomal instability (high FAL value) defines a subset of patients who are more likely to benefit from cisplatin-based neoadjuvant chemotherapy. p53 mutation status is not significantly associated with therapy response and is not a useful marker for response prediction.  相似文献   
100.
Her-2/neu is a tumor-associated antigen that is expressed on several adenocarcinomas and correlates with poor prognosis. In a previous study (H. J. Bühring et al., Blood, 86: 1916-1923, 1995), it has been demonstrated that Her-2/neu expression can be detected on blast cells from patients with hematological malignancies including acute lymphoblastic leukemia (ALL). Here, we show that Her-2/neu-specific CTLs induced in vitro using peptide-pulsed dendritic cells efficiently lyse primary ALL blasts constitutively expressing both Her-2/neu and human leukocyte antigen A2 in an antigen-specific and MHC-restricted manner. Furthermore, we analyzed the feasibility of this approach in an autologous setting and induced Her-2/neu-specific CTLs using dendritic cells generated from peripheral blood mononuclear cells from an ALL patient that were pulsed with peptides or transfected with in vitro-transcribed Her-2/neu mRNA. Our data demonstrate that Her-2/neu could be used as a potential target for the application of Her-2/neu-directed treatment strategies in ALL including vaccination approaches.  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