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   14650篇
  免费   609篇
  国内免费   71篇
耳鼻咽喉   144篇
儿科学   451篇
妇产科学   143篇
基础医学   1942篇
口腔科学   292篇
临床医学   983篇
内科学   3962篇
皮肤病学   322篇
神经病学   998篇
特种医学   520篇
外科学   2238篇
综合类   38篇
一般理论   1篇
预防医学   470篇
眼科学   217篇
药学   1041篇
中国医学   34篇
肿瘤学   1534篇
  2023年   72篇
  2022年   169篇
  2021年   261篇
  2020年   187篇
  2019年   191篇
  2018年   274篇
  2017年   240篇
  2016年   257篇
  2015年   259篇
  2014年   334篇
  2013年   415篇
  2012年   650篇
  2011年   795篇
  2010年   470篇
  2009年   420篇
  2008年   736篇
  2007年   762篇
  2006年   731篇
  2005年   811篇
  2004年   814篇
  2003年   743篇
  2002年   711篇
  2001年   334篇
  2000年   334篇
  1999年   303篇
  1998年   182篇
  1997年   148篇
  1996年   148篇
  1995年   139篇
  1994年   134篇
  1993年   144篇
  1992年   302篇
  1991年   256篇
  1990年   221篇
  1989年   286篇
  1988年   251篇
  1987年   234篇
  1986年   235篇
  1985年   206篇
  1984年   152篇
  1983年   112篇
  1982年   71篇
  1981年   57篇
  1980年   48篇
  1979年   92篇
  1978年   71篇
  1977年   57篇
  1971年   47篇
  1969年   48篇
  1968年   47篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
The detection of circulating immune complexes (CIC) in sera from patients with IgA nephropathy is described. A solid-phase anti-C3 Facb enzyme immunoassay (EIA) was employed for detection of IgA-, IgG- and IgM-CIC in sera. The C1q-binding enzyme assay was also used for the detection of CIC in sera from these patients and healthy adults. Twenty-two patients with IgA nephropathy, 14 patients with other glomerular diseases and 19 healthy adults were examined by anti-C3 Facb EIA. The levels of IgA-CIC in sera from patients with IgA nephropathy were significantly higher than those in sera from patients with other glomerular diseases and healthy adults. CIC measured by the C1q-binding enzyme assay was detected in some patients with IgA nephropathy. The levels of serum IgA in patients with IgA nephropathy were significantly higher than those in patients with other glomerular diseases and healthy adults. However, there was no significant correlation between the levels of IgA-CIC in sera and those of serum IgA in patients with IgA nephropathy. There was also no significant correlation between the levels of IgA-CIC in sera and the degree of histopathological injuries in the patients. It is concluded that the solid-phase anti-C3 Facb EIA is useful for the detection of IgA-CIC in sera from patients with IgA nephropathy.  相似文献   
102.
A case of recurrent soft part sarcoma with focal areas showing epithelial differentiation in the right thigh in a 78-year-old woman is reported. The primary tumor consisted of myxoid areas and solid areas, in which relatively uniform epithelioid tumor cells were arranged in sheets, whereas pleomor-phism and a storiform pattern appeared in the recurrent tumors. Thus this tumor was suspected to be a malignant fibrous histiocytoma. However, further studies showed unexpected ultrastructural and immunohistochemical features. Cytokeratin immu-noreactivity and tonofilamentlike structures probably indicated epithelial differentiation of some tumor cells. From the clinical and histological findings, this tumor should be identified as a malignant fibrous histiocytoma with phenotypic expressions of epithelial cell.  相似文献   
103.
The atypical cells of CD30(+) cutaneous lymphoproliferative disorders (CD30CLD) are commonly of T-cell origin and frequently have a similar morphology as Hodgkin or Reed-Sternberg cells of Hodgkin's lymphoma (HL). HL is one of the tumors associated with CD30CLD. Although most studies support a B-cell derivation of the tumor cells in HL, recently a few cases of classical HL with T-cell genotype have been reported. We report a patient who presented with CD30CLD whose lymph nodes showed classical HL of mixed cellularity subtype at presentation. By single-cell PCR, the same clonal gene rearrangements of the T cell receptor-beta gene locus could be assigned to the CD30(+) and CD15(+) cells of both skin and lymph node. In a lymph node biopsy specimen taken in relapse after several courses of chemotherapy, the CD30(+) tumor cells were abundant. The T cell-derived tumor cells displayed aberrant expression of the Pax-5 gene in all specimens. A common clonal origin of both CD30CLD and HL of the lymph node in the patient presented here suggests that HL with T-cell genotype exists in association with CD30CLD as well as in sporadic cases and may share clonal origin with the skin tumor.  相似文献   
104.
Acute graft-versus-host disease (GVHD) is characterized by the production of high levels of T helper 1 (Th1)-type cytokines. Bone marrow transplantation from allogeneic C57BL/6 cells to CBF(1) mice produced acute GVHD. Host resistance to Th1-driven Listeria monocytogenes was enhanced, whereas host resistance to Th2-driven Staphylococcus aureus was reduced during acute GVHD. These results suggest that opposite host responses are observed between Th1-driven and Th2-driven bacterial infections in acute GVHD.  相似文献   
105.
Summary: Energy‐filtering transmission electron microscopy (EFTEM) was employed for the analysis of polymer‐polymer interfaces. To attain imaging and spectral analyses with a spatial resolution of 10 nm, problems arising in the EFTEM analysis for polymer specimens were investigated. Interfaces in poly(methyl methacrylate)/polystyrene‐co‐polyacrylonitrile random copolymer (PMMA/SAN) bilayer films annealed at different temperatures were analyzed by means of elemental mapping and Image‐EELS on EFTEM and the effect of the annealing temperature on the interfacial structures was also investigated.

  相似文献   

106.
Pheochromocytoma usually shows prominent nuclear atypia, but the presence of such atypical cells is known to be an unreliable predictor of malignancy. DNA ploidy of pheochromocytomas has been analyzed by flow cytometry or photospectrometry on paraffinem-bedded tissue, but the results were controversial. We performed DNA analysis on cytology specimens of 11 pheochromocytomas using an image analysis system. All tumors had a mixed pattern of a large population of diploid cells and a small population of polyploid cells. DNA content correlated with nuclear size, and larger cells had more DNA content. Such larger tumor cells had polyploid nuclei, such as 4 C, 8 C, 16 C, and 32 C, in both malignant and benign pheochromocytomas. The larger polyploid nuclei may result from difficulty of duplication at the mitotic phase of the cell cycle.  相似文献   
107.
The hereditary conservation in the genetically encoded CD1D sequences of various primates was analyzed. Genomic CD1D sequences of 17 rhesus macaques with distinct origins, eight Indian and nine Chinese, were examined and differences of only one or two nucleotides were detected and the consensus sequence of rhesus CD1D was determined. CD1D consensus sequences of three African green monkeys (AGMs) and the rhesus monkeys were then compared to study the evolutionary differences among interspecies. The CD1D consensus sequence determined from AGMs apparently differed by seven nucleotides from the rhesus consensus sequence, and nucleotide difference induced only three amino acid changes within Exon3, corresponding to the alpha2 domain of CD1d having a hydrophobic ligand-binding pocket. Such changes in the alpha2 domain may alter the characteristics of the SIV-derived glycolipid/lipid antigens presented by each CD1d molecule to innate natural killer T cells. In addition, the CD1D genomic sequences of three chimpanzees (chimps) were determined. To our surprise, although Exon2 and Exon3 reflecting antigen-binding alpha1 and alpha2 domains in chimps' CD1D were identical to that in humans except one amino acid, three amino acids within Exon4, reflecting alpha3 domain, were distinct from humans, and one of them was identical to those in rhesus and AGM CD1D. On the basis of the findings, the evolutionary relationship of the CD1d molecules among the various primates and their HIV-1/SIV susceptibility will be discussed.  相似文献   
108.
Summary The pathogenesis of the nodular lesion in diabetic glomerulosclerosis is described in association with fibrils. Thirteen diabetic patients with glomerular nodular lesions and 9 diabetics without the nodules were examined by electron microscopy using periodic acid-thio-carbohydrazide-silver proteinate staining. In cases of nodular glomerulosclerosis, abundant fibrillar structures mixed with electron-dense material were detected within the nodule and the mesangial matrix. They were also occasionally observed along the subendothelial space of the glomerular capillary walls. On the cross-section, these fibrils, including the lucent periphery, were 34 nm wide. Immunohistologically, collagen V and collagen VI were detected in nodular lesions. In contrast, in cases of the diffuse type of glomerulosclerosis, the widened mesangium was composed of dense material, which resembled the original mesangial matrix. The above fibrils were not detected in the mesangium. These findings suggest that the accumulation of the peculiar fibrils in the glomerular mesangium is a major pathogenic factor in the formation of Kimmelstiel-Wilson nodules.  相似文献   
109.
ABSTRACT: Human leukocyte antigen (HLA) genes are candidates for susceptibility genes in insulin-dependent diabetes mellitus (IDDM). Recently, the association of DR and DQ with IDDM has been reported, but the role of HLA-DP genes remains uncertain. To address the question, we analyzed the DPB1 gene of 20 Japanese IDDM patients and 30 control subjects using a combination of polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis (PCR-RFLP method). DPB1*0501 was the most frequent allele both in Japanese patients and control subjects. There was no appreciable association between IDDM and the DPB1 allele in Japanese. The absence of association between IDDM and DP, in spite of the known association between this disease and both DR and DQ, suggests that the HLA locus (loci) telomeric to DP encodes susceptibility to IDDM.  相似文献   
110.
The reliability of the Japanese public telephone facilities to transmit electrocardiograms (e.c.g.) for computer interpretation was assessed. The International Business Machine's (IBM) e.c.g. computer program by Bonner was used. No appreciable distortion of e.c.g. was observed following repeated transmission from hospitals separated by 1000 km. Thirty-four normal and 66 abnormal e.c.g.s. were transmitted twice. Identical results were observed in 97% of normals and 92% of abnormals. Following these fundamental experiments, 1236 patients' e.c.g.s. were transmitted for computer intepretation. The study showed that 98·6% (1219 cases) were technically satisfactory and 1·4% (17 cases) were not. The 17 unsatisfactory cases were classified into ten unreceivable data formats, six inconsistent measurements and one unacceptable noise level. The authors concluded that the Japanese public telephone facilities were acceptable for the transmission of e.c.g.s. for computer interpretation.  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