全文获取类型
收费全文 | 15116篇 |
免费 | 993篇 |
国内免费 | 186篇 |
专业分类
耳鼻咽喉 | 218篇 |
儿科学 | 331篇 |
妇产科学 | 733篇 |
基础医学 | 1931篇 |
口腔科学 | 261篇 |
临床医学 | 1583篇 |
内科学 | 3202篇 |
皮肤病学 | 372篇 |
神经病学 | 934篇 |
特种医学 | 472篇 |
外科学 | 2319篇 |
综合类 | 419篇 |
现状与发展 | 2篇 |
一般理论 | 3篇 |
预防医学 | 761篇 |
眼科学 | 286篇 |
药学 | 1083篇 |
中国医学 | 102篇 |
肿瘤学 | 1283篇 |
出版年
2023年 | 79篇 |
2022年 | 236篇 |
2021年 | 435篇 |
2020年 | 220篇 |
2019年 | 329篇 |
2018年 | 420篇 |
2017年 | 289篇 |
2016年 | 292篇 |
2015年 | 458篇 |
2014年 | 585篇 |
2013年 | 731篇 |
2012年 | 1106篇 |
2011年 | 1091篇 |
2010年 | 702篇 |
2009年 | 571篇 |
2008年 | 875篇 |
2007年 | 887篇 |
2006年 | 804篇 |
2005年 | 822篇 |
2004年 | 700篇 |
2003年 | 578篇 |
2002年 | 539篇 |
2001年 | 471篇 |
2000年 | 414篇 |
1999年 | 349篇 |
1998年 | 128篇 |
1997年 | 102篇 |
1996年 | 84篇 |
1995年 | 68篇 |
1994年 | 65篇 |
1993年 | 44篇 |
1992年 | 179篇 |
1991年 | 168篇 |
1990年 | 145篇 |
1989年 | 120篇 |
1988年 | 107篇 |
1987年 | 122篇 |
1986年 | 100篇 |
1985年 | 83篇 |
1984年 | 75篇 |
1983年 | 58篇 |
1980年 | 38篇 |
1979年 | 57篇 |
1978年 | 49篇 |
1977年 | 42篇 |
1976年 | 39篇 |
1975年 | 38篇 |
1974年 | 47篇 |
1972年 | 59篇 |
1971年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Status of hepatitis B virus DNA in hepatocellular carcinoma: a study based on paired tumor and nontumor liver tissues 总被引:1,自引:0,他引:1
M Y Lai D S Chen P J Chen S C Lee J C Sheu G T Huang T C Wei C S Lee S C Yu H C Hsu 《Journal of medical virology》1988,25(3):249-258
To investigate the hepatitis B virus (HBV) DNA status in the liver when hepatocellular carcinoma (HCC) has developed, 35 paired nontumorous and tumorous liver tissues from 27 hepatitis B surface antigen (HBsAg)-seropositive and 8 HBsAg-negative patients with HCC were studied by Southern blot analysis. The hybridization patterns of HBV DNA were different in the nontumor and tumor parts in 26 (96.3%) of the 27 HBsAg-positive patients. In the nontumor parts, integration of HBV DNA into the host genome was significantly less when compared to the tumor parts (15/27 vs. 25/27, P less than 0.05), whereas free replicative viral forms were significantly more frequent (17/27 vs. 7/27). The integrated HBV DNA in the nontumor parts showed discrete band patterns in the majority of cases (13/15). Hepatitis B e antigen (HBeAg) was significantly associated with the expression of free replicative forms of HBV DNA in the tumor tissues. An integrated HBV DNA sequence was detected in the tumor part of one HBsAg-negative patient, but not in her nontumor counterpart. Our observation that discrete integrated HBV DNAs are present in the nontumor part, representing subclinical clonal expansion that precedes the development of HCC, suggests the risk of future new tumor growth from these cell clones. 相似文献
82.
Cloning of the fusion gene of rinderpest virus: comparative sequence analysis with other morbilliviruses 总被引:3,自引:0,他引:3
We have cloned the cDNA of the fusion (F) gene of the virulent (Kabete O) strain of rinderpest virus and provided a comparative analysis of its sequence with that of the F genes of measles and distemper viruses. The gene has an open reading frame of 2241 nucleotides with two potential initiation codons in-frame. Use of the first ATG would produce a polypeptide 747 amino acids long with a calculated molecular weight of 81,068. However, we suggest that the second ATG is used to generate the Fo protein, which is 546 amino acids long with a calculated molecular weight of 58,754. During maturation, the cleavage of F0 gives rise to the functional F1 and F2 polypeptides. The F1 polypeptide is 438 amino acids long and has a calculated molecular weight of 46,791, with a single (potential) glycosylation site in its cytoplasmic domain. The F2 polypeptide, probably 89 amino acids long after the signal sequence is cleaved, is estimated to be 9,800 Da and has three potential glycosylation sites. There is a divergence of 18.7% in amino acid sequences between rinderpest and measles virus F0 polypeptides; between distemper and rinderpest viruses the divergence is 31.8%. No significant homology in nucleotide sequences of rinderpest DNA to measles or distemper DNA was found in the 5' and 3' untranslated regions. 相似文献
83.
Effect of peroral immunization of humans with Streptococcus mutans on induction of salivary and serum antibodies and inhibition of experimental infection 下载免费PDF全文
Naturally occurring antibodies reactive with Streptococcus mutans whole cells were assayed in whole saliva, parotid saliva, and blood samples collected from eight human volunteers. The levels and serotypes of indigenous S. mutans in plaque and whole saliva samples were also determined. After baseline sampling the teeth were cleaned and the subjects were inoculated with streptomycin-resistant S. mutans strains Ingbritt (serotype c) and OMZ65 (serotype g). The level of implantation and duration of colonization were determined in plaque and saliva, and antibodies reactive with these strains were monitored in saliva and serum. After the implanted bacteria were shed, the subjects wee immunized by the daily ingestion of an enteric-coated capsule containing 25 mg of Formalin-killed, freeze-dried OMZ65 cells for 3 days and inoculation was repeated. The levels of antibodies and of implantation and the duration of colonization were monitored as before. One month after the bacteria could no longer be detected, the immunization and inoculation cycle was repeated except that the subjects were immunized for 7 days. Five of the eight subjects were successfully colonized by strains Ingbritt and OMZ65. The remaining three did not become colonized with either strain. Strain OMZ65 implanted at a higher level than did strain Ingbritt. Oral immunization did not result in a detectable antibody response in saliva or serum to whole bacterial cells. However, after both the first and second immunizations there were marked reductions in the peak levels of infection and the duration of colonization of both OMZ65 and Ingbritt. 相似文献
84.
85.
Harley BA Spilker MH Wu JW Asano K Hsu HP Spector M Yannas IV 《Cells, tissues, organs》2004,176(1-3):153-165
The experimental study of peripheral nerve regeneration has depended heavily on the use of a nerve chamber in which the stumps of the transected nerve are inserted. A large variety of chamber fillings and chamber types have been used in an effort to induce a higher quality of regeneration across the gap initially separating the two stumps. In this study we studied the morphology of nerves regenerated across a 15 mm gap following implantation of a series of five chambers. The chambers were fabricated from type I collagen and possessed identical pore volume fractions as well as average pore diameters, but differed in cross-link density continuously along the series. The residual mass of the implanted chambers at 9 weeks was observed to increase continuously with increasing cross-link density along the series, indicating a continuous decrease in degradation rate. The quality of regenerated nerves, determined by the number of large diameter fibers (A-fibers) per nerve, the average diameter of all axons and the ratio of area occupied by axons (N-Ratio), was superior at an intermediate level of chamber degradation rate. The maximal quality of peripheral nerve regeneration corresponded to an optimal degradation rate with an estimated chamber half-life of approximately 2-3 weeks following implantation. A speculative mechanistic explanation of the observed optimum focuses on the hypothetical role of cell and cytokine traffic that may take place through holes in the chamber generated by the degradation process. The data show the presence of a hitherto unreported optimal chamber degradation rate that leads to regenerated nerves of maximum quality. 相似文献
86.
Bone marrow examination in patients with AIDS and AIDS-related complex (ARC). Morphologic and in situ hybridization studies 总被引:1,自引:0,他引:1
N C Sun P Shapshak N A Lachant M Y Hsu L Sieger P Schmid G Beall D T Imagawa 《American journal of clinical pathology》1989,92(5):589-594
Bone marrow examinations were performed on 20 patients with acquired immune deficiency syndrome (AIDS) and 39 with AIDS-related complex (ARC). Fever of unknown origin and thrombocytopenia were common in ARC, but anemia and leukopenia were most frequent in AIDS. Changes in stromal cells and perivascular cuffing of plasma cells were found significantly more often in patients with AIDS than in those with ARC. Malignancies were common in both groups. Human immunodeficiency virus (HIV) nucleic acids were detected with the use of a 3H-labeled cDNA probe with an in situ hybridization method in 11 bone marrow samples (three ARC and eight AIDS). Most commonly positive cells were mononucleated, resembling lymphocytes and histiocytes. Endothelial cells, interdigitating reticulum cells, nucleated red blood cells, and immature myeloid cells also had positive results in some instances. The number of HIV-positive cells was not related to the size of the bone biopsies or the clinical diagnoses. The authors postulate that changes in the peripheral blood and bone marrow of these patients may be related to latent persistent infection with HIV. 相似文献
87.
Chen-Tong Hsu Yu-Tsan Lin Yao-Hsu Yang Bor-Luen Chiang 《Journal of microbiology, immunology, and infection》2004,37(2):121-123
Hyperimmunoglobulin E syndrome is a primary immunodeficiency disease characterized by markedly high titers of serum immunoglobulin E (IgE), chronic eczema, recurrent staphylococcal infections, pneumatoceles, reduced neutrophil chemotaxis, and variable impaired T cell function. There are no clinical tools for diagnosis and definitive laboratory investigation. Variability of presentation makes it easy to confuse the diagnosis with that of severe atopy or other rare immunodeficiencies. We report a case of a 6-year-old boy with hyperimmunoglobulin E syndrome with recurrent methicillin-resistant Staphylococcus aureus furunculosis. Physical examination revealed a peculiar facial appearance, pruritic dermatitis, and furunculosis over the scalp, neck, and back. Laboratory investigation revealed mild leukocytosis with eosinophilia, a very high immunoglobulin E level, defective neutrophil chemotaxis, and impaired lymphocyte proliferation to anti-CD3/CD28 monoclonal antibodies. The boy was discharged without incident after 2 weeks of antibiotic therapy and debridement. 相似文献
88.
Antibody against Epstein-Barr virus DNA polymerase activity in sera of patients with nasopharyngeal carcinoma 总被引:1,自引:0,他引:1
A salt-dependent DNA polymerase activity was demonstrated in the culture of an EBV-producing, lymphoblastoid cell line (NPC-204 cells) treated with 5-iodo-2'-deoxyuridine (IUdR). There was a high frequency of levels of antibody to this enzyme in sera of patients with nasopharyngeal carcinoma (NPC). In contrast, sera from healthy subjects had little or no neutralizing activity. The high antibody level appeared as early as stage 1 of the disease in many NPC patients. The levels of the antibody increased with the progression of the disease and declined in treated patients. The results strongly suggest that tests measuring serum antibody against EBV DNA polymerase activity can be used for early diagnosis and prognosis of NPC. 相似文献
89.
Holtzman D. Herman M. M. Hsu J. Shen Mortell P. 《Virchows Archiv : an international journal of pathology》1980,387(2):147-164
Summary The toxic effects of inorganic lead feedings on the immature brain were studied in the rat pup. Beginning when litters were two weeks old, PbCO3 was fed to nursing mothers and then to pups directly after weaning. Results in lead-fed pups were compared to age-matched controls and to lead-fed young adult males (60 days old). Anaemia and growth failure developed in both pups and adults. In the second week, more than half the pups developed an encephalopathy, with haemorrhage and oedema predominately in the cerebellum and lead-containing densities in the cerebellar molecular layer. The latter were confirmed by X-ray microanalysis. No lead-fed adults showed signs of an encephalopathy.Cerebellar mitochondria from lead-fed pups, studied polarographically, showed a very early loss of respiratory control and a subsequent inhibition of phosphorylation-coupled respiration with NAD-linked substrates but not with succinate. Compared to the pup cerebellum, these changes were much less marked in immature cerebral mitochondria and were not found in adult cerebral or cerebellar mitochondria.Cerebral and cerebellar homogenates from immature and mature lead-fed animals showed large increases in lead content measured by atomic absorption spectrophotometry. Immature cerebellar mitochondrial lead contents were increased to the same extent as in the homogenates. Mitochondria from immature cerebrum and from both regions in the mature brain showed less immediate and smaller increases in lead content.In conclusion, altered mitochondrial respiration occurs early in regional and age-dependent association with lead encephalopathy in the rat pup. The development of lead encephalopathy also is associated with increased mitochondrial lead concentrations. 相似文献
90.
Lymphomas of true histiocytic origin. Expression of different phenotypes in so-called true histiocytic lymphoma and malignant histiocytosis. 下载免费PDF全文
The authors determined the phenotypes of neoplastic cells in true histiocytic lymphoma and malignant histiocytosis by using a large panel of monoclonal antibodies and enzyme histochemistry procedures. Although the phenotypes overlapped slightly, the authors noted a distinct pattern in these tumors. The tumor cells of malignant histiocytosis generally expressed the monocyte markers CD11b, CD11c, CD14, and CD45, especially after induction with phorbol ester. In contrast, the tumor cells of true histiocytic lymphoma exhibited a marker expression very similar to that of Reed-Sternberg cells in Hodgkin's disease. These cells expressed markers CD30, 2H9, and 1A2, but rarely expressed CD11b, CD11c, CD14, or CD45. Regardless of their cytologic features, the tumor cells from both types of histiocytic lymphoma exhibited diffuse nonspecific esterase and acid phosphatase activities, and they expressed histiocyte markers CD15, CD68, LN5, 1E9, and M387 to varying degrees. The tumor cells from both lymphomas did not exhibit T- or B-cell markers, T-cell receptor or immunoglobulin gene rearrangements, or gene translation products, even when they were induced with phorbol ester. The phenotypic expression in these two histiocytic malignancies suggests that they are derived from different types of histiocytes, or from histiocytes in different stages of maturation or differentiation, or from histiocytes that have distinct mechanisms of tumorigenic transformation. The expression of circulating monocyte markers in malignant histiocytosis suggests that this tumor originates in monocytes or free histiocytes, whereas the phenotype of true histiocytic lymphoma is compatible with an origin in fixed histiocytes, which generally are devoid of the monocyte markers CD11b and CD14. 相似文献