全文获取类型
收费全文 | 46340篇 |
免费 | 2092篇 |
国内免费 | 319篇 |
专业分类
耳鼻咽喉 | 408篇 |
儿科学 | 805篇 |
妇产科学 | 560篇 |
基础医学 | 6163篇 |
口腔科学 | 1327篇 |
临床医学 | 2781篇 |
内科学 | 11162篇 |
皮肤病学 | 965篇 |
神经病学 | 3139篇 |
特种医学 | 2192篇 |
外科学 | 8065篇 |
综合类 | 205篇 |
一般理论 | 1篇 |
预防医学 | 1249篇 |
眼科学 | 754篇 |
药学 | 2950篇 |
中国医学 | 137篇 |
肿瘤学 | 5888篇 |
出版年
2023年 | 233篇 |
2022年 | 612篇 |
2021年 | 1001篇 |
2020年 | 514篇 |
2019年 | 747篇 |
2018年 | 997篇 |
2017年 | 759篇 |
2016年 | 909篇 |
2015年 | 949篇 |
2014年 | 1242篇 |
2013年 | 1597篇 |
2012年 | 2552篇 |
2011年 | 3021篇 |
2010年 | 1716篇 |
2009年 | 1447篇 |
2008年 | 2607篇 |
2007年 | 2860篇 |
2006年 | 2727篇 |
2005年 | 2929篇 |
2004年 | 2838篇 |
2003年 | 2833篇 |
2002年 | 2816篇 |
2001年 | 811篇 |
2000年 | 761篇 |
1999年 | 849篇 |
1998年 | 724篇 |
1997年 | 568篇 |
1996年 | 548篇 |
1995年 | 456篇 |
1994年 | 400篇 |
1993年 | 360篇 |
1992年 | 542篇 |
1991年 | 471篇 |
1990年 | 486篇 |
1989年 | 489篇 |
1988年 | 428篇 |
1987年 | 396篇 |
1986年 | 343篇 |
1985年 | 328篇 |
1984年 | 260篇 |
1983年 | 188篇 |
1982年 | 126篇 |
1981年 | 135篇 |
1980年 | 117篇 |
1979年 | 135篇 |
1978年 | 109篇 |
1977年 | 94篇 |
1976年 | 67篇 |
1974年 | 75篇 |
1972年 | 63篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Hiroko Utsunomiya Wanninayake M. Tilakaratne Kazufumi Oshiro Satoshi Maruyama Makoto Suzuki Hiroko Ida-Yonemochi Jun Cheng Takashi Saku 《Journal of oral pathology & medicine》2005,34(8):498-507
BACKGROUND: Oral submucous fibrosis (OSF) is a chewing habit-related pre-cancerous condition of the oral mucosa affecting predominantly south Asians. It is histopathologically characterized by epithelial atrophy and fibrosis of the subepithelial connective tissue. Fibrosis extends all the way into the muscle layer, leading to difficulty in mouth opening. However, the dynamics of extracellular matrix (ECM) remodeling with OSF progression is largely unknown. METHODS: Forty biopsy specimens of OSF and 10 of normal buccal mucosa were examined for expression/deposition modes of eight ECM molecules by histochemistry, immunohistochemistry, and in situ hybridization. RESULTS: In the early stage of OSF, tenascin, perlecan, fibronectin, collagen type III were characteristically enhanced in the lamina propria and the submucosal layer. In the intermediate stage, the ECM molecules mentioned above and elastin were extensively and irregularly deposited around muscle fibers. In the advanced stage, such ECM depositions decreased and were entirely replaced with collagen type I only. Their gene expression levels varied with progression of fibrosis, but the mRNA signals were confirmed in fibroblasts in the submucosal fibrotic areas. CONCLUSIONS: The results indicate that the ECM remodeling steps in OSF are similar to each phase of usual granulation tissue formation. Restricted mouth opening may be a result of loss of variety of ECM molecules including elastin into the homogeneity of collagen type I replacing muscle fibers. 相似文献
42.
The kinetics and dynamics of glial fibrillary acidic protein (GFAP) assembly was explored by a fluorescence energy transfer assay method. Purified GFAP was stoichiometrically labeled at a single cysteine residue with fluorescein-maleimide. Soluble labeled GFAP in a low ionic strength buffer was assembled into 10 nm filaments by rapidly increasing the ionic strength, and the kinetics of GFAP assembly was monitored by the reduction in fluorescence due to self-quenching of fluorescein. The extent of fluorescence quench correlated with both the formation of 10 nm filament morphology and the amount of protein pelleted at 12,000g. The assembly of GFAP is critically dependent upon both protein and magnesium ion concentration, and at the critical concentration for GFAP assembly is approximately 40 micrograms/ml. Disassembly of GFAP filaments was also observed as a relief of fluorescence quenching after dilution of labeled GFAP filaments. When labeled GFAP filaments were mixed with an excess of unlabeled filaments, a rapid increase of fluorescence was observed, which is due to an exchange of subunits between labeled and unlabeled GFAP filaments. These results indicate that GFAP filaments are dynamic structures and that a small pool of kinetically active unassembled GFAP subunits are in a dynamic equilibrium with assembled GFAP filaments. The ability of GFAP to assemble, disassemble, and undergo subunit exchange has important implications for the organization and dynamics of astroglia cell cytoskeleton during development and in response to injury. 相似文献
43.
Soroku Doko M.D. F.I.C.A. Tatsuki Katsumura M.D. F.I.C.A. Takashi Fujiwara M.D. Hiroshi Inada M.D. Hisao Masaki M.D. 《The International journal of angiology》1995,4(1):55-60
One hundred and thirty-four patients with vasoocclusive diseases were retrospectively tested for three kinds of antiphospholipid antibody (aPL). The mean age at onset of the disease in 58 patients with aPL was 43 years old. Seventeen, 11, and 9 patients were positive for the aCL IgA, IgM, and IgG isotypes, respectively. The rates of anti-phospholipid syndrome (APS) in patients with arterial (n=94), venous (n= 31), or both arterial and venous (n=9) occlusion were 45%, 29%, and 78%, respectively.The rates of APS in patients with autoimmune disease (n=13), thromboangiitis obliterans (TAO) (n= 36), arteriosclerosis obliterans (ASO) with lower leg involvement (n=8) or aortic arch syndrome (n=5), Raynaud's syndrome (n=15), aortitis syndrome (n= 13), ischemic heart disease (IHD) with young onset (n =12), and bilateral leg deep venous thrombosis (DVT) (n=10) were 77%, 46%, 13%, 80%, 40%, 62%, 33%, and 70%, respectively. The cumulative patency rate for reconstructive surgery in patients (n=13) with aCL was found to be considerably lower than that in those without aCL (n=13). From these results it was concluded that IgA was the most valuable aCL isotype for the diagnosis of APS and that aPL should be examined in patients with double-vessel occlusion, autoimmune disease, bilateral leg DVT, aortic arch syndrome, TAO, Raynaud's syndrome, or IHD with young onset. Furthermore, prophylaxis for graft failure is more strongly recommended for patients with aCL than for those without it. 相似文献
44.
Takashi Ito Kazuo Shimamura Kiyoshi Shoji Akira Akatsuka Yasuyoshi Kiryu Norikazu Tamaoki Yoshiyuki Osamura 《Virchows Archiv : an international journal of pathology》1993,422(6):487-490
A rare case of urinary bladder carcinoma with granulocyte colony stimulating factor (G-CSF) production was reported. In an 83-year-old female, marked neutrophilia in the peripheral blood decreased from 132,500/mm3 to 3,300/mm3 after tumour resection. The tumour was a transitional cell carcinoma. The serum G-CSF level reduced from 238 pg/ml pre-operatively to normal (60 pg/ml) after the operation. Immunohistochemical investigation of the resected tumour with monoclonal antibody specific for G-CSF revealed positive staining in the carcinoma cells, confirming G-CSF secretion. 相似文献
45.
N. Inotsume M. Nishimura M. Nakano S. Fujiyama K. Sagara T. Sato K. Matsushita Y. Imai H. Matsui 《European journal of clinical pharmacology》1990,38(3):313-314
Summary The effect of haemodialysis on the pharmacokinetics of oral famotidine has been studied in five elderly anuric patients. Famotidine 20 mg was administered in a cross-over design to patients on and not on haemodialysis.The elimination rate constant of haemodialysis (k) was 4.6-fold larger than the systemic elimination rate constant (ke). Although the mean maximum serum concentration of famotidine during haemodialysis (141.5 ng·ml–1) was not significantly lower than that without haemodialysis (195.6 ng·ml–1), the AUC up to 5 h during haemodialysis was significantly decreased to 58.1% of the value without it.The data suggest that famotidine is dialysable by haemodialysis. 相似文献
46.
M Ohsugi Y Imanishi T Teraoka K Nishimura S Nakao 《Journal of nutritional science and vitaminology》1990,36(5):447-456
The biosynthesis of biotin-vitamers from various carbon sources by the members of the Enterobacteriaceae as one of the groups of intestinal bacteria was investigated. The biotin-vitamers synthesized in each case included one or more of dethiobiotin (main product), 7-keto-8-aminopelargonic acid, and biotin. True biotin was shown to be synthesized under aerobic conditions but not under anaerobic conditions by each of several strains belonging to one of the genera, Erwinia, Escherichia, Proteus, and Serratia, and using culture media containing one of galactose, peptone, Polypepton, or casamino acid. In addition, a biotin precursor, pimelic acid, was also synthesized by several bacteria utilizing carbon sources such as maltose, mannose, galactose, peptone, or casamino acid. 相似文献
47.
Masatoshi Chiba Takashi Shigihara Seishi Echigo Teiichi Teshima 《Journal of bone and mineral metabolism》1990,8(3):24-29
Summary In this study, we examined histologically the effect of a bone morphogenetic protein (BMP) derived from bovine tooth on the
periosteum. Supraperiosteal injection of crude BMP into femurs of Wistar rats (28 day old) resulted in periosteal cell proliferation
with subsequent bone and cartilage formation. Moreover, proliferating periosteal cells migrated into injected BMP, and formed
both cartilage and bone. These observations show that exogenous BMP stimulates mesenchymal cells of the periosteum to proliferate
and differentiate into osteoblasts, and therefore BMP may be one of factors which are involved in differentiation of osteoblasts
in the periosteum. 相似文献
48.
Takashi Shuto Yutaka Ohtsubo Ken'ichi Sekido Hiroko Iwamoto Isao Yamamoto 《Child's nervous system》1996,12(2):107-109
We report the case of an infant with a cerebellar astrocytoma that showed marked calcification within only 6 months. In general, only slow-growing tumors tend to calcify. To our knowledge, no other case of such rapid calcification in cerebellar astrocytoma has been reported. 相似文献
49.
Sumie Yamanaka Masanori Hashimoto Masuo Tobe Kazuo Kobayashi Jun Sekizawa Masao Nishimura 《Archives of toxicology》1990,64(4):262-268
We proposed a simple method for screening assessment of acute oral and dermal toxicity using only three rats and mice of each sex at each dose level. Animals were first treated with chemicals at a dose of 2000 mg/kg and were carefully observed for compound-related morbidity and mortality. If none of the animals died, the following toxicity tests were suspended. If some of the animals died, toxicity tests at doses of 200 and 20 mg/kg were performed. The approximate LD50 values calculated by this method showed little difference between two separate laboratories and were in good agreement with LD50 values reported in the literature. Our toxicological data also showed that LD50 values were about 2–2.5 times the MNLD (maximum non lethal dose) in acute oral and dermal toxicity. This meant that a chemical could be regarded as having an LD50 of about 4000 mg/kg or higher when there was no mortality at the dose of 2000 mg/kg. A chemical with such low toxicity would not require further testing for lethal effects. Therefore, this simple method combining the fixed-dose procedure with the limit test is suitable for determination of approximate LD50 values of chemicals and for screening for necessity for classical full LD50 test using many animals.This work was supported by a grant from Ministry of Health and Welfare in Japan (No. 467 and 511) 相似文献
50.
Hisashi Tanii Norio Taniguchi Hisayoshi Niigawa Takayoshi Hosono Yasumitsu Ikura Sakae Sakamoto Takashi Kudo Tsuyoshi Nishimura Masatoshi Takeda 《Brain research》1996,743(1-2)
The neuroleptic malignant syndrome (NMS) is a life-threatening complication of neuroleptic treatment. To elucidate the pathogenesis of NMS, an animal model has been developed. Experimental rabbits treated with haloperidol (1 mg/kg) by intramuscular injection, were studied for the diagnostic symptoms of increased muscle rigidity, elevated body temperature, and high serum creatine phosphokinase (CPK) level. Administration of haloperidol (1 mg/kg) and atropine (0.4 mg/kg), and exposure to high ambient temperature (35°C) induced a significant increase in electromyographic activity with muscle rigidity similar to that observed in patients with NMS. Such rabbits also showed elevated body temperature and serum CPK value. In addition to the similarity of the signs and symptoms, all parameters measured (muscle rigidity, body temperature, and serum CPK level) were normalized by dantrolene treatment. The effectiveness of dantrolene in the experimental animal partially confirms the validity of this animal model for NMS. This experimental animal model for NMS may be useful to elucidate the pathogenesis of NMS. 相似文献