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   9050篇
  免费   450篇
  国内免费   36篇
耳鼻咽喉   58篇
儿科学   145篇
妇产科学   133篇
基础医学   1115篇
口腔科学   186篇
临床医学   644篇
内科学   2199篇
皮肤病学   156篇
神经病学   462篇
特种医学   397篇
外科学   1971篇
综合类   62篇
预防医学   346篇
眼科学   137篇
药学   501篇
中国医学   19篇
肿瘤学   1005篇
  2023年   54篇
  2022年   95篇
  2021年   145篇
  2020年   86篇
  2019年   109篇
  2018年   134篇
  2017年   139篇
  2016年   152篇
  2015年   183篇
  2014年   211篇
  2013年   217篇
  2012年   368篇
  2011年   430篇
  2010年   250篇
  2009年   187篇
  2008年   400篇
  2007年   453篇
  2006年   414篇
  2005年   448篇
  2004年   427篇
  2003年   410篇
  2002年   393篇
  2001年   351篇
  2000年   354篇
  1999年   326篇
  1998年   127篇
  1997年   97篇
  1996年   99篇
  1995年   74篇
  1994年   48篇
  1993年   74篇
  1992年   212篇
  1991年   174篇
  1990年   173篇
  1989年   168篇
  1988年   152篇
  1987年   159篇
  1986年   142篇
  1985年   150篇
  1984年   104篇
  1983年   91篇
  1982年   43篇
  1979年   76篇
  1978年   57篇
  1977年   45篇
  1974年   45篇
  1973年   48篇
  1971年   49篇
  1968年   44篇
  1967年   41篇
排序方式: 共有9536条查询结果,搜索用时 15 毫秒
101.
The pathomorphologic features of hypertrophic cardiomyopathy simulating dilated cardiomyopathy in the late stage (HCM-DCM) were compared with those of ordinary hypertrophic cardiomyopathy (HCM). Seven autopsied hearts with HCM-DCM and 11 with HCM were assessed quantitatively using an image analyzer. Unlike HCM, significant left ventricular enlargement and wall thinning were observed in HCM-DCM, and the percentage areas of massive fibrosis and disarray were significantly greater. In HCM-DCM, the disarray was distributed diffusely, whereas massive fibrosis was distributed more intensively in the ventricular septum and anterior wall than in the lateral and posterior wall. Narrowing of intramyocardial small arteries was observed more frequently in HCM-DCM, especially in the ventricular septum and anterior wall, than in HCM. These results suggest that the enlargement and wall thinning of the left ventricle in HCM-DCM are attributable to non-uniform progression of massive fibrosis, which is closely related to small-arterial lesions.  相似文献   
102.
Based on the results of cytological studies, it has been assumed that Cyanidioschyzon merolae does not contain actin genes. However, Southern hybridization of C. merolae cell-nuclear DNA with a yeast actin-gene probe has suggested the presence of an actin gene in the C. merolae genome. In the present study, an actin gene was isolated from a C. merolae genomic library using a yeast actin-gene probe. The C. merolae actin gene has no intron. The predicted actin is composed of 377 amino acids and has an estimated molecular mass of 42003 Da. Southern hybridization indicated that the C. merolae genome contains only one actin gene. This gene is transcribed at a size of 2.4 kb. When Southern hybridization was performed with C. merolae chromosomes separated by pulsed-field gel electrophoresis, a band appeared on unseparated chromosomes XI and XII. A phylogenetic tree based on known eucaryote actin-gene sequences revealed that C. merolae diverged after the division of Protozoa, but before the division of Fungi, Animalia and Chlorophyta.  相似文献   
103.
To isolate Babesia equi genes encoding immunodominant proteins, a cDNA expression library prepared from B. equi mRNA was immunoscreened with B. equi-infected horse serum. Eighteen positive cDNA clones were obtained, and the clone that showed the strongest immunoreactivity, designated Be82, was further characterized. The Be82 gene consisted of 1,953 bp and contained a partial open reading frame lacking the 5'-terminal sequence. As shown by Western blot analyses, immune sera from mice intraperitoneally injected with the Be82 gene product recognized the 82- and 52-kDa proteins of B. equi but not those of Babesia caballi. The glutathione S-transferase fusion protein expressed in Escherichia coli that was purified and used as the antigen in the enzyme-linked immunosorbent assay reacted specifically with B. equi-infected horse sera. These results suggest that the Be82 gene product is a potential diagnostic antigen candidate in the detection of B. equi infection in horses that will be useful both in the performance of epidemiological studies and in the granting of quarantine passes.  相似文献   
104.
Novel segmented multiblock copolymers ( 7 ) were synthesized by linking poly(ethylene oxide) (PEO) blocks with poly(β-benzyl L -aspartate)(PBLA) blocks via urethane and urea bonds, which were formed by the reaction of 4,4′-methylenediphenyl isocyanate ( 5 ) with the terminal hydroxyl groups of α-hydro-ω-hydroxypoly(oxyethylene) ( 4 ) and the terminal amino groups of poly(β-benzyl L -aspartate)-block-iminohexamethyleneimino-block-poly(β-benzyl L -aspartate) ( 3 ) [prepared from 1,6-hexanediamine ( 1 ) and β-benzyl L -aspartate N-carboxy anhydride ( 2 )], respectively. Membranes with various water contents were obtained from these copolymers by changing the lengths of the PEO and PBLA segments. The study of the permeation of 1-phenyl-1,2-ethanediol, vitamin B12 and myoglobin through the membranes showed a high dependency of the permeability on the molecular weight of the solutes.  相似文献   
105.
In this study, we investigated the localization and functional significance of p53 tumor suppressor-like molecules, p63 and p73, in human thymic epithelial cells (TECs). Immunohistochemical studies showed particular distribution profiles of p63 and p73 in thymic epithelium, in which cortical TECs preferentially expressed p63 in their nuclei whereas subcapsular and medullary TECs expressed both p63 and p73 in their nuclei. The wide distribution of p63 in TECs was further suggested by studies using TECs of primary culture. In vitro studies using two human TEC lines demonstrated that p63 was capable of up-regulating intercellular adhesion molecule-1 (ICAM-1) and enhancing the production of IL-6 and IL-8. Moreover, in vitro studies also indicated that p73, but not p63, had the capacity to induce granulocyte macrophage colony stimulating factor (GM-CSF) and granulocyte colony stimulating factor (G-CSF) in the TEC lines. These findings suggest that p63 would regulate the cell adhesive property through ICAM-1/LFA-1 interaction and the production of IL-6 and IL-8, probably in all TEC subtypes. p73 in subcapslar and medullary TECs was suggested to play a role in the regulation of the production of GM-CSF and G-CSF, which might stimulate other stromal cells such as dendritic cells, macrophages and endothelial cells around these regions.  相似文献   
106.
An improved method for constructing canine herpesvirus (CHV) recombinants expressing foreign genes by using the lacZ-TK gene cassette as a double selectional marker was developed. A recombinant CHV carrying the lacZ-TK gene at a targeted gene locus was constructed and used as a parental virus for generating new recombinants. The parental virus formed blue plaques and was sensitive to TK-specific drugs, while newly generated recombinants, in which the lacZ-TK gene was replaced with the desired foreign gene, become both resistant to the TK-specific drugs and formed white plaques. Recombinants were isolated by using the combination of drug selection and color selection. This improved method allows construction of recombinant CHV with great ease, because the drug selection can enrich the frequency of recombinant CHV from 0.01–0.1% to 10–80%. This method was employed to construct a recombinant CHV that expressed rabies virus (RV) glycoprotein (G protein). This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
107.
Drug adherence is one of the important aspects in caring for patients with allergic rhinitis. To improve clinical efficacy of early treatment for Japanese cedar pollinosis (JCP), we evaluated the effect of drug adherence on patients' outcomes. Patients were randomly selected from 16 ENT clinical sites in Osaka and Wakayama between February 24 and March 8, 2003 (peak pollen season). Efficacy was assessed using patients' ratings of nasal and ocular symptoms and overall assessment in their condition compared with previous season ones. Costs include direct costs of the drugs used for treatment to JCP from January to February. Five hundred one patients taking early treatment were enrolled. Compared to low adherence patients, those who reported higher level of adherence significantly improved overall health condition, and achieved better symptom relief of rhinorrhea and nasal congestion. In multiple logistic regression analysis, the following factors were independent risk factors for low adherence: student (p=0.002), using OTC medications (p=0.006), and short-duration of medication (p=0.001). Low costs were also risk factor for low adherence. We conclude that taking medications for JCP for 22-28 days is the best way to enhance patients' outcomes.  相似文献   
108.
Fine-needle aspiration (FNA) cytology was performed on 15 patients with peripheral lymphadenopathy and/or skin lesions referred to the Department of Pathology of the Hospital Central of Maputo, Maputo, Mozambique. Epitrochlear lymph nodes were the most frequently aspirated site. All aspirates allowed diagnoses of Kaposi's sarcoma (KS). Smears contained loosely cohesive clusters of bland spindle cells, with a radial arrangement and nuclear crush artifacts. These diagnostic clues have not been described in other spindle-cell intranodal lesions that should be considered in differential diagnoses. Taking into consideration the high prevalence of AIDS and limited resources for diagnosis in Africa, FNA cytology appears to be a useful method for the diagnosis of KS in developing countries, reducing the necessity for surgical lymph node excision.  相似文献   
109.
110.
Microtia was found in a transgenic mouse 643 and all offspring with microtia had the transgene. No anomalies, other than occasional low set ear and abnormal biting, were identified in other tissues and organs. In the developmental analysis, on the 9th and 10th days of gestation, hypoplasia of the second branchial arch was observed, while various kinds of malformed hillocks were noted on the 12th day. All of these anomalous embryos were transgenic. Histologically, hemorrhage and subsequent phagocytosis were noted at the second branchial arch. Left sided anomalies were predominant and in bilaterally defective ones asymmetry existed. These findings closely resembled to those in experimental animals with a phenocopy of the first and second branchial arch syndrome in humans. Since all other transgenic mouse lines with the same transgene as 643 appeared normal, this dysmorphic phenotype may be caused by an insertional mutation of a host gene, although inappropriate expression of the transgene should be examined further as a possible cause. These results suggest that this transgenic mouse line 643 may be useful as an animal model of branchial arch anomalies in humans.  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