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   8158篇
  免费   364篇
  国内免费   53篇
耳鼻咽喉   44篇
儿科学   106篇
妇产科学   84篇
基础医学   1285篇
口腔科学   157篇
临床医学   504篇
内科学   2340篇
皮肤病学   38篇
神经病学   792篇
特种医学   257篇
外科学   1069篇
综合类   31篇
一般理论   1篇
预防医学   181篇
眼科学   136篇
药学   701篇
中国医学   29篇
肿瘤学   820篇
  2023年   43篇
  2022年   68篇
  2021年   162篇
  2020年   83篇
  2019年   113篇
  2018年   143篇
  2017年   108篇
  2016年   144篇
  2015年   161篇
  2014年   198篇
  2013年   284篇
  2012年   446篇
  2011年   513篇
  2010年   295篇
  2009年   253篇
  2008年   474篇
  2007年   517篇
  2006年   521篇
  2005年   465篇
  2004年   459篇
  2003年   471篇
  2002年   497篇
  2001年   151篇
  2000年   157篇
  1999年   171篇
  1998年   128篇
  1997年   112篇
  1996年   99篇
  1995年   74篇
  1994年   102篇
  1993年   79篇
  1992年   121篇
  1991年   112篇
  1990年   100篇
  1989年   74篇
  1988年   72篇
  1987年   72篇
  1986年   59篇
  1985年   72篇
  1984年   64篇
  1983年   33篇
  1982年   20篇
  1981年   28篇
  1980年   24篇
  1979年   33篇
  1978年   23篇
  1977年   20篇
  1976年   21篇
  1975年   28篇
  1974年   17篇
排序方式: 共有8575条查询结果,搜索用时 15 毫秒
51.
We found a HhaI/BstUI polymorphism in the 3′ untranslated region of a novel gene which was localized to 11p15.5. This region is one of prominent imprinting domains and contains multiple imprinted genes, such as H19, IGF2 , KVLQT1, and p57 KIP2 , which suggests that regional factors might contribute to the imprinting. This polymorphism will be useful in the allelic analysis of expression and methylation of the novel gene. Received: July 24, 1998 / Accepted: July 29, 1998  相似文献   
52.
A case of peritoneal maligant mesothelioma in a radiation technologist, who had worked in this field for 34 years, is reported. Histopathologically, a biopsy specimen from the retroperitoneal tumor revealed a biphasic type of malignant mesothelioma. Electron microscopy disclosed that the tumor cells contained prominent microvilli, basal laminae adjacent to the stroma, junctional complexes, desmosomes, tonofilaments, clusters of glycogen granules, welt developed rough endoplasmic reticulum (RER), confronting cisternae showing direct continuity with the RER and membrane-bound granules suggestive of secretory activity. No increased amount of asbestos was detected in autopsied lung material or the peritoneal mesothelioma. The estimated cumulative dose of occupational irradiation was calculated to be about 40 to 50 rad at most. Irradiation was discussed in relation to the etiology of the peritoneal mosothelioma. Acta Pathol Jpn 40: 57–62, 1990.  相似文献   
53.
Several lines of evidence indicate that glycogen synthase kinase-3beta (GSK3beta) is one of the candidates for schizophrenia-susceptibility factor. However, it has not been reported the association analysis between GSK3beta gene (GSK3B) and Japanese schizophrenia based on linkage disequilibrium (LD). We provide an association analysis using relatively large samples (381 schizophrenia, and 352 controls) after determination of "tag single nucleotide polymorphisms (SNPs)." In this LD mapping, we selected and genotyped for eight polymorphisms (seven SNPs and one diallelic (CAA)(n) repeat), which covered the entire region of GSK3B, and determined two "tag SNPs." In the following association analysis using these two "tag SNPs," we could not find association with Japanese schizophrenia. Furthermore, we also include subgroup analysis considering age-at-onset and subtypes, neither could we find associations. Because our samples provided quite high power, these results indicate that GSK3B may not play a major role in Japanese schizophrenia.  相似文献   
54.
This study was designed to evaluate the histological changes during ossification and cellular events including osteogenic differentiation responding to collagenous bioresorbable membranes utilized for GBR. Standardized artificial bony defects were prepared at rat maxillae, and covered with a collagenous bioresorbable membrane. These animals were sacrificed at 1, 2, 3 and 4 weeks after the GBR-operation. The paraffin sections were subject to tartrate resistant acid phosphatase (TRAP) enzyme histochemistry and immunohistochemistry for alkaline phosphatase (ALP), osteopontin (OP) and osteocalcin (OC). In the first week of the experimental group, woven bone with ALP-positive osteoblasts occupied the lower half of the cavity. The collagenous membrane included numerous ALP-negative cells and OP-immunoreactive extracellular matrices. At 2 weeks, the ALP-, OP- and OC-immunoreactivity came to be recognizable in the region of collagenous membrane. Since ALP-negative soft tissue separated the collagenous membrane and the new bone originating from the cavity bottom, the collagenous membrane appeared to induce osteogenesis in situ. At 3 weeks, numerous collagen fibers of the membrane were embedded in the adjacent bone matrix. At 4 weeks, the membrane-associated and the cavity-derived bones had completely integrated, showing the same height of the periosteal ridge as the surrounding alveolar bones. The collagen fibers of a GBR-membrane appear to participate in osteogenic differentiation.  相似文献   
55.
Radiotherapy is one of the most effective treatments for cancers. However, external irradiation provides only small doses to deep-seated cancers, and often causes damage to healthy tissues. It has been reported that 20-30 microm diameter 17Y(2)O(3)-19Al(2)O(3)-64SiO(2) (mol%) glass microspheres are useful for the in situ irradiation of cancers. Yttrium-89 (89Y) in this glass can be neutron bombarded to form the beta-emitter 90Y (half-life=64.1h). When injected in the vicinity of the cancer, such activated glass microspheres can provide a large localized dose of beta-radiation. The Y(2)O(3) content of the glass in the microspheres is limited to only 17 mol%. Chemically durable microspheres with a higher Y(2)O(3) content need to be developed. Phosphorus-31 (31P) with 100% natural abundance can also be activated by neutron bombardment to form the beta-emitter 32P (half-life=14.3d). Chemically durable microspheres containing a high phosphorus content are expected to be more effective for cancer treatment. We prepared pure Y(2)O(3) and YPO(4) microspheres using a high-frequency induction thermal plasma melting technique, and investigated the resulting structure and chemical durability. We successfully prepared smooth, highly spherical polycrystalline Y(2)O(3) and YPO(4) microspheres with diameters in the range 20-30 microm. Both the Y(2)O(3) and YPO(4) microspheres showed high chemical durability in saline solutions buffered at pH=6 and 7. These microspheres are expected to be more effective than the conventional glass microspheres for the in situ radiotherapy of cancer.  相似文献   
56.
Intracellular staining with HRP of physiologically identified group Ia and Ib afferent fibers in the adult cat lumbosacral cord revealed that group Ia and Ib fibers take a similar course in the dorsal funiculus, but the collaterals emerging from them show a different topographical distribution and a different mode of branching in the gray matter. Ia collaterals terminate in laminae VI, VII, IX, and sometimes VIII, whereas Ib collaterals terminate only in lamina VI, or both VI and IX. In lamina IX, two large motor-type neurons received terminations of both Ia and Ib fibers at the same time.  相似文献   
57.
58.
Twelve autopsied cases with adult T-cell leukemia (ATL) were reviewed clinicopathologically. The prognosis of three cases who had suffered from severe cutaneous lesions was much better than that of the other nine cases with no or negligible cutaneous lesions. The surface marker of leukemic cells from six cases was ordinary inducer/helper phenotype (OKT4+ and 8-), but in one case leukemic cells showed OKT4+ and 8+. In another case, a significant amount of leukemic cell infiltration was found in the thymic cortex. Calcium content in the bone of ATL cases was lower than that of the patients without ATL (control group), and six cases with ATL (50%) were complicated by severe hypercalcemia. Neither adenoma nor hyperplasia of the parathyroid glands was found in any case. In most severely hypercalcemic patients, bone trabeculae were actively absorbed by numerous osteoclasts and partly replaced by fibrous tissues. In two normocalcemic patients, skeletal calcium content was also markedly reduced by osteoporosis, but the activation of osteoclasts was inconspicuous. It was speculated that the manner of bone resorption in ATL cases was diverse and there were some clinicopathological subtypes in ATL from the viewpoints of cutaneous lesions, hypercalcemia, and bone lesions.  相似文献   
59.
Kinetic studies on the acid-catalyzed reaction of formaldehyde with diphenyl sulfide (DPS) were carried out in acetic acid in the presence of sulfuric acid. The rate of the initial stage of the reaction was found to be in agreement with the following equation. The relative rates of diphenyl sulfide and its homologous compounds in the reaction with formaldehyde gave a good correlation with BROWN -OKAMOTO 's σ values and a large ρ value. The polar effects of substituents of the substituted diphenyl sulfides on the rates were found to be considerably large. From these results a plausible mechanism of the reaction has been deduced.  相似文献   
60.
Phosphorylcholine (PC) antibodies in serum from patients with pulmonary infection, and from normal individuals, were studied. Anti-PC antibodies were detectable in the serum from normal individuals at mean concentrations of 320 g/ ml for the IgG class and 110 g/ml for the IgM class. Concentrations of anti-PC antibodies which were higher than normal for both the IgG and IgM classes were observed in the serum in pulmonary infection (1,440 g/ml and 210 g/ml, respectively). Despite the significant difference in the concentration of anti-PC antibodies, the PC-specific B cell precursor frequency in the peripheral blood lymphocytes showed no difference between normal individuals and the patients with pulmonary infection, or between the acute phase and the chronic phase in a single patient with chronic pulmonary infection. Serologically, the purified IgG anti-PC antibody did not share the cross-reactive idiotype of TEPC 15, which is the most common idiotype of the murine anti-PC antibodies. However, the purified IgM anti-PC antibody expressed a very weak cross-reactive idiotype of TEPC 15. It appears from these studies that human anti-PC antibodies may play an important biological role in pulmonary infection by microorganisms which possess a PC determinant.  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