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   2028篇
  免费   131篇
  国内免费   6篇
耳鼻咽喉   12篇
儿科学   115篇
妇产科学   24篇
基础医学   396篇
口腔科学   204篇
临床医学   189篇
内科学   444篇
皮肤病学   9篇
神经病学   176篇
特种医学   59篇
外科学   199篇
综合类   17篇
预防医学   165篇
眼科学   17篇
药学   61篇
肿瘤学   78篇
  2023年   7篇
  2022年   26篇
  2021年   46篇
  2020年   30篇
  2019年   32篇
  2018年   26篇
  2017年   41篇
  2016年   39篇
  2015年   53篇
  2014年   63篇
  2013年   95篇
  2012年   134篇
  2011年   144篇
  2010年   60篇
  2009年   77篇
  2008年   151篇
  2007年   141篇
  2006年   154篇
  2005年   114篇
  2004年   127篇
  2003年   142篇
  2002年   107篇
  2001年   40篇
  2000年   20篇
  1999年   26篇
  1998年   29篇
  1997年   14篇
  1996年   11篇
  1995年   15篇
  1994年   13篇
  1993年   8篇
  1992年   9篇
  1991年   12篇
  1990年   5篇
  1989年   11篇
  1988年   11篇
  1987年   7篇
  1986年   10篇
  1985年   16篇
  1984年   15篇
  1983年   12篇
  1982年   14篇
  1981年   11篇
  1980年   7篇
  1979年   12篇
  1977年   6篇
  1976年   3篇
  1974年   3篇
  1972年   5篇
  1967年   3篇
排序方式: 共有2165条查询结果,搜索用时 15 毫秒
1.
A wide variety of biological and alloplastic injectable biomaterials are available for soft tissue augmentation, but the ideal material has not yet been discovered. Biological materials such as collagen and hyaluronan yield temporary results, while injectable alloplasts are apt to cause varying degrees of foreign body reactions that may result in lumps and chronic inflammation.We present two cases (one is the first filed case in the world) of migratory subcutaneous inflammatory masses secondary to injection of acrylic hydrogel (DermaLive), which is an alloplastic biomaterial recently introduced into the market in Europe. Histology revealed foreign body reaction to acrylic hydrogel with granuloma formation containing multinucleated giant cells. Following this, further reports on complications have been reported elsewhere in Europe. The use and development of injectable materials, as well as alternative methods and future directions are reviewed.  相似文献   
2.
Epilepsy After Stroke   总被引:48,自引:4,他引:44  
A retrospective follow-up of 200 consecutive stroke patients [ischemic brain infarction (IBI) 157, intracerebral hemorrhage (ICH) 20, subarachnoid hemorrhage (SAH) 23] who were in need of ambulatory rehabilitation was conducted for a mean period of 40 months after stroke. Epilepsy developed in 33 (17%) patients. The occurrence of epilepsy was 14% in IBI, 15% in ICH, and 35% in SAH. Significantly more patients developed epilepsy in the SAH group than in the IBI group (8 of 23 vs. 22 of 157, p less than 0.05). Of the 33 patients, 15% had their first seizures within the first 2 weeks after stroke, and 55% developed epilepsy in 6 months. Forty-eight percent of the patients had generalized seizures. Antiepileptic drug (AED) treatment was started in 28 of 33 patients, of whom 17 still had seizures during follow-up. Epilepsy was an important consequence of stroke among patients who needed rehabilitation, especially in SAH patients. In most, this was due to arterial spasm leading to IBI.  相似文献   
3.
OBJECTIVES: Damage mechanics has been defined as the study of the initiation (initial failure) and accumulation of damage to and including rupture (final failure). This study was designed to evaluate the effect of increasing fiber-reinforced composite (FRC) substructure within a standardized fixed partial denture (FPD) model on the failure performance, in terms of damage mechanics. METHODS: The two FRC restorative systems, Targis/Vectris (TV) (Ivoclar Vivadent) and EverStick (ES) (Stick Tech with Gradia, GC Corp.), were used to restore the molar FPD model (1.5 mm axial and 2.0 mm occlusal reduction). Templates were used to standardize substructure designs with 0, 18, 43, and 66% cross-sectional FRC volume fraction (V(FRC)) of fiber substructure. Specimens (n = 5) were homogenized at 29 points and stored for 1 week at 37 degrees C in distilled water. Specimens were luted with calcium hydroxide, then statically loaded until failure. Initial failure (IF), final failure (FF) and the mode of failure were recorded. RESULTS: The lowest mean load to initial failure was 530 N (TV 18%) and the highest was 1208 N (ES 66%). Linear regression analysis calculated the Pearson's correlation coefficient (r) for the interactions between V(FRC) and IF (ES: r = 0.7879, TV: r = 0.6184), V(FRC) and FF (ES: r = 0.912, TV: r = 0.8152), and between IF and FF (ES: r = 0.892, TV: r = 0.7237). Unreinforced specimens universally fractured instantaneously. SIGNIFICANCE: The highest loads to initial and final failure were yielded by specimens with the highest cross-sectional V(FRC).  相似文献   
4.
During the initial stages of B lymphocyte differentiation heavy chain variable (VH), diversity (DH) and joining (JH) gene segments recombine to form a functional heavy chain variable region (VDJ) gene. Evidence for genetic polymorphism of the human JH gene segments has been obtained from mature rearranged VDJ sequences. We conducted an analysis of the published rearranged JH gene sequences and found that the JH alleles present in the two published germ-line JH region sequences were rare (approx. 2%) in the rearranged sequences. As an attempt to explain this discrepancy a 2.5-kb strech of DNA containing all the six heavy chain JH region genes and the most 3' DH gene segment, DHQ52, was amplified by the polymerase chain reaction from 39 individuals and analyzed for restriction fragment length polymorphism. Five new JH region haplotypes were found and sequenced. These new haplotypes contained the coding segment alleles that were frequent in antibody genes. Surprisingly, a high number of interallelic differencies in the non-coding sequence was found between the new and the two previously published haplotypes implying that the haplotypes had been separated early in evolution. In this respect the JH locus resembles HLA loci.  相似文献   
5.
6.
Seventeen monoclonal anti-2-phenyloxazolone antibodies from the early (day 7) primary response were partially sequenced with an mRNA method. Ten antibodies expressed the VH-Ox1 gene. The remaining seven express at least four but probably six different germ-line VH genes belonging to Dildrop's groups 1, 5, 6 and 7 (Immunol. Today 1984. 5: 85). Two of them have been met before in other antibodies, one (group 6) in J606 and the other (group 7) in antibodies to the influenza virus hemagglutinin. Eleven kappa chains were partially sequenced and five of them (all VH-Ox1 antibodies) express the V kappa-Ox1 gene. One expresses another germ-line gene of the V kappa-Ox1 family, one the V kappa 89.4 gene, three the V kappa 45.1 gene and one a new V kappa gene. The V kappa 45.1 gene was found to form anti-phOx antibodies with two new VH genes. The frequency of somatic mutations in day 7 antibodies was estimated by comparing germ-line sequences and antibody sequences. It is low (one mutation per 2500 nucleotides sequenced), twenty times lower than in antibodies obtained a week later. Two anti-idiotype antisera (495 and 260) are useful in the typing of monoclonal antibodies. 260 bound only to antibodies coded by both VH-Ox1 and V kappa-Ox1 genes. 495 bound strongly to antibodies coded by the VH-Ox1 gene and weakly to antibodies coded by the (related) VH101 gene regardless of the light chain partner.  相似文献   
7.
Estimation of genetic risk for type 1 diabetes   总被引:8,自引:0,他引:8  
The most important gene loci defining risk of type 1 diabetes mellitus (T1DM) are located within the HLA gene region. HLA-DQ molecules are of primary importance but HLA-DR gene products modify the risk conferred by HLA-DQ. The risk associated with an HLA genotype is defined by the particular combination of susceptible and protective alleles. The highest risk is associated with a combination of two different risk haplotypes (7% risk to develop T1DM in Finland) whereas protective genotypes covering 69% of population have a risk of less than 0.2%). The complicated analysis of HLA genotypes is simplified by strong linkage disequilibrium between HLA-DRB1, -DQA1 and -DQB1 loci. In many cases one can deduce the alleles of other loci based on determination of the alleles in one locus. Differences between various populations in the frequency of marker alleles and in the linkages between them has to be taken into account. We have developed PCR based typing methods that utilize blood spot samples, microtiter plate format and lanthanide labeled oligonucleotide probes to define HLA-DQ and -DR alleles relevant for T1DM risk. Typing is run stepwise so that after initial HLA-DQB1 typing only those samples will be further analyzed in which -DQA1 or -DRB1 typing is informative and expected to contribute to the risk estimation. This method has been used to screen more than 50,000 newborn infants in Finland over a time period of 6 years, and it has been able to identify most children who have developed T1D during the follow-up period. The efficiency of the procedure has also been tested in Finnish and Greek populations.  相似文献   
8.
Summary The human fetal carotid body was studied using both histochemical and electron microscopic methods. The glomus cells of a mid term fetal carotid body evidently contain catecholamines. This was demonstrated both by formaldehyder-induced fluorescence of the cells and by the presence of typical dense-cored vesicles (diameter 1430–3200 Å) in the cytoplasm of the chief cells. The glomus cells were densely innervated and the synapses found on their surface were probably cholinergic in type, containing agranular synaptic vesicles measuring 400–700 Å in diameter with a few dense-cored vesicles measuring 900 to 1300 Å. Synapses were not found in any other cell type within the glomus caroticum. The prominent feature of the glomus cell cytoplasm was the presence of the dense-cored vesicles. The density of the vesicular core varied only slightly from cell to cell. There were no perceptible differences in vesicular size between the different cells. The glomus cells were mostly surrounded by the processes of the sustentacular cells, which usually also surrounded the capillary walls. No glomus cells were ever found in direct contact with the capillary wall. The capillaries were wide and very numerous over the restricted area of the organ. They formed sinusoidal loops, probably anastomosing with each other. Finally, the features of the fine structure are discussed, correlating the present findings with our knowledge about the adult functional carotic body.  相似文献   
9.
Some characteristics of hemagglutination (HA) by the BK virus, a new candidate for the papovavirus group, have been studied. Hemagglutinin prepared from cell cultures was found to be partially masked by inhibitors which could be dissociated from the virus by incubation at 37 C or by fluorocarbon extraction. Optimal conditions for HA are outlined. In routine tests, 0.5% human erythrocytes were used. The reaction was carried out at pH 7.0 on ice-water slurry. BK hemagglutinin receptors on human erythrocytes were found to be more resistant to neuraminidase than polyoma receptors. By gradient centrifugation analysis, two types of particles were found to be responsible for HA: (i) full, deoxyribonucleic acid-containing particles with a density of 1.325 g/cm(3) and (ii) empty capsids with a density 1.29 g/cm(3). Based on particle counting, one HA unit was calculated to correspond to 3 x 10(6) virus particles.  相似文献   
10.
Solid-phase immunoassay-derived antibody titers are often converted to weight unit concentrations with the aid of standard sera containing known antibody concentrations. Systematic studies justifying this procedure have not yet been published. We therefore investigated the magnitude of errors associated with this conversion. Antibody concentrations of thirteen sera or ascites fluids were determined by quantitative precipitation or equlibrium dialysis, and one was then used as a “standard antibody” for the others in solid-phase radioimmunoassay (SP-RIA) or enzyme-linked immunosorbent (ELISA) assays. Antibody concentrations determined by the conventional solid-phase assay (the “standard serum” has the same specificity as the “sample”) had up to fourfold errors. These errors could be reduced by basing the conversion on the combination of two standard sera instead of one. The possibility was studied of whether the conversion to weight units could be done with the aid of a standard serum directed to a different antigen than the sample antibody. Errors associated with the use of such a heterologous standard were not significantly greater than those found using the conventional conversion. A combination of two reference sera again reduced the errors. The use of such heterologous standard(s), however, requires checking the binding capacity of the antigen coats.  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