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   2293188篇
  免费   178107篇
  国内免费   13104篇
耳鼻咽喉   29852篇
儿科学   74804篇
妇产科学   63991篇
基础医学   325892篇
口腔科学   61896篇
临床医学   212508篇
内科学   445566篇
皮肤病学   51643篇
神经病学   183360篇
特种医学   86914篇
外国民族医学   822篇
外科学   336089篇
综合类   70093篇
现状与发展   27篇
一般理论   824篇
预防医学   179724篇
眼科学   53353篇
药学   166972篇
  119篇
中国医学   10790篇
肿瘤学   129160篇
  2021年   21727篇
  2019年   20972篇
  2018年   28126篇
  2017年   22134篇
  2016年   24380篇
  2015年   28652篇
  2014年   39373篇
  2013年   55768篇
  2012年   75397篇
  2011年   80494篇
  2010年   47797篇
  2009年   44509篇
  2008年   72254篇
  2007年   76205篇
  2006年   77164篇
  2005年   74735篇
  2004年   70204篇
  2003年   67107篇
  2002年   64317篇
  2001年   107864篇
  2000年   110695篇
  1999年   92947篇
  1998年   27566篇
  1997年   25042篇
  1996年   24534篇
  1995年   23414篇
  1994年   21402篇
  1993年   19679篇
  1992年   70312篇
  1991年   67749篇
  1990年   65607篇
  1989年   62744篇
  1988年   57283篇
  1987年   56734篇
  1986年   52908篇
  1985年   50673篇
  1984年   38314篇
  1983年   32321篇
  1982年   19637篇
  1981年   17545篇
  1979年   34453篇
  1978年   24509篇
  1977年   20508篇
  1976年   19354篇
  1975年   20088篇
  1974年   24363篇
  1973年   23451篇
  1972年   21748篇
  1971年   20003篇
  1970年   18897篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Rapid voltammetric procedures for the determination of water-soluble vitamins C, B1, and B2, fat-soluble vitamin E (α-tocopherol acetate), and quercetin in bioactive food additives have been developed. The systematic error (i.e., correctness) of the proposed procedures was evaluated using certified reference materials and the additive recovery tests, which gave the following limiting metrological characteristics: relative error, 25 %; reproducibility, 28 %; convergence, 22 %. The full analysis time (with sample preparation) did not exceed 2 hours. Voltammetric determinations under optimum conditions can be performed in the automated regime controlled by a computer according to the specially developed software.__________Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 39, No. 3, pp. 54 – 56, March, 2005.  相似文献   
992.
The kinetics of alkaline hydrolysis of N-(5-nitro-2-thiazolyl)-2-thiophenylcarboxamide (tenonitrozole or atrican) has been studied by photometric and polarographic techniques, and the thermodynamic parameters in the intermediate state of this process were determined. A mechanism explaining the nitric oxide (NO) production during the hydrolytic decomposition of tenonitrozole is proposed. It is suggested that the antiprotozoal and antimicrobial activity of this drug under anaerobic conditions is related to the formation of nitro radical anions and NO. Under aerobic and microaerophilic conditions, the hydrolysis of tenonitrozole may lead to the formation of a peroxynitrite anion, which is a strong cytotoxic agent. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 39, No. 6, pp. 15 – 18, June, 2005.  相似文献   
993.
The antibiotics that are recommended for treatment of pelvic inflammatory disease (PID) in the outpatient setting are efficacious against Neisseria gonorrhoeae and Chlamydia trachomatis. The susceptibility of non-sexually transmitted pathogens to these agents has not been well studied. The mean inhibitory concentrations of ampicillin, cefpodoxime, metronidazole, and doxycycline were determined for 137 upper-genital tract isolates from 84 women with confirmed PID. Antibiotic resistance was noted in 16%, 9%, 93%, and 72% of the facultative and 0%, 11%, 10%, and 56% of the anaerobic bacteria when tested against ampicillin, cefpodoxime, metronidazole, and doxycycline, respectively. The authors conclude that doxycycline is limited to coverage of Chlamydia and that a single dose of another antibiotic may not be adequate to eradicate the non-sexually transmitted disease pathogens from the upper-genital tract. Additional clinical and microbiologic studies are needed to determine whether the current outpatient antibiotic regimens provide optimal coverage for the non-sexually transmitted pathogens that are associated with PID.  相似文献   
994.
Proteoglycans have been isolated and analysed from extracts of normal and chronically inflamed human gingiva in order to determine the effects of chronic inflammation on these important soft connective tissue extracellular macromolecules. The uronic acid content of glycosaminoglycans isolated by papain digestion of normal and inflamed gingiva did not differ significantly. Likewise, electrophoretic analysis revealed that the content of hyaluronic acid, heparan sulfate, dermatan sulfate and chondroitin sulfute was similar. The sulfated glycosaminoglycans from both sources eluted from a Sepharose C1-6B column with a Kav of 0.45 (approximate Mr 25,000). However, hyaluronic acid from normal gingiva was predominantly of a large size eluting in the void volume of a Sepharose. CL-6B column, while that isolated from inflamed tissue was mostly a small molecular weight species which elutccl in the included volume of a Sepharose CL-6B column. Using dissociative conditions, intact proteoglycans could be more readily extracted from inflamed tissues (90% of the total tissue uronic acid) than from normal tissues where only 80% of the total tissue uronic acid was extractable. Even though DEAE-Sephacel ion-exchange chromatography revealed no differences in charge between normal and inflamed gingival proteoglycans, Sepharose CL-4B chromatography revealed more molecular size polydispersity in samples from inflamed tissue than from normal tissue. Taken together, these results indicate that while hyaluronic acid is depolymerized in inflamed tissue, no evidence of sulfated glycosaminoglycan degradation was found. Therefore, the most likely cause for disruption to the molecular integrity of the proteoglycans is via proteolytic alteration to the proteoglycan core protein.  相似文献   
995.
996.
The Monk Duopleet femoral interlocking uncemented two-component endoprosthesis consists of a polyethylene cup covered by a metal cap and an Austin-Moore type stem. Seventy-two patients (average age, 71 years) were treated by this arthroplasty: 27 for subcapital femoral neck fracture, 36 for osteoarthritis, and nine as an exchange operation. Three patients died following operation. After a mean follow-up time of 50 months, 47 patients were reexamined clinically and radiographically. Because of loosening, four patients had the prosthesis removed. Twenty-six patients were classified as excellent, 12 as good, six as fair, and three as poor. There were no cases of acetabular intrusion. The Monk Duopleet prosthesis may solve the problem of the loosening that had been associated with femoral component alone. The long-term results are promising and appear to be better than the results of the standard Moore prosthesis. The Monk Duopleet prosthesis is an alternative to other two-component endoprostheses for the treatment of subcapital hip fractures and in the group of patients suffering from osteoarthritis, where an arthroplasty with a cemented prosthesis may be considered hazardous because of age or general disease.  相似文献   
997.
998.
Eleven patients with refractory rheumatoid arthritis were submitted to a total lymphoid irradiation up to a dose of 20 Gy. A constant improvement of clinical symptoms was observed in four out of the eleven patients already during the treatment and in the other patients not later than two months after. The frequency of attacks decreased and the number of joints involved in the attack was reduced. Morning rigidity and joint swellings decreased. One patient developed joint empyemas 4 and 26 months after the treatment. Four patients died in the meantime. In two patients the cause of death were renal insufficiency and a postoperative cardiogenic shock associated with generalized amyloidosis. The third patient died because of a toxically induced left cardiac decompensation with sepsis that could not be controlled by antibiotic drugs and multiple joint empyemas. The fourth patient developed an abscess after surgical treatment of a Kaposi syndrome. She died three months later from acute left cardiac decompensation. The therapy induced a lymphocytopenia with decrease of T helper lymphocytes and unchanged number of T suppressor lymphocytes. The constant therapy results of total lymphoid irradiation in primary chronic polyarthritis is probably due to this modification in the immune regulation.  相似文献   
999.
Basal isolated canine paw blood flow was equally distributed between arteriovenous anastomosis (AVA) and capillary circulations. Norepinephrine decreased AVA flow by 92% and capillary flow by 41%. Dopamine significantly reduced AVA flow by 94% compared to baseline with a 37% reduction in capillary flow. However, with alpha-adrenergic blockade dopamine decreased AVA flow 66% while capillary flow increased 42%. Isoproterenol increased capillary flow almost twofold and appeared to decrease AVA flow, although the latter was statistically insignificant. Differential effects of adrenergic and dopaminergic agonists on canine paw AVA and capillary blood flow suggest the existence of independent regulation of these components of the microcirculation.  相似文献   
1000.
Mitogen responsiveness of lymphocytes from the BB/W rat   总被引:3,自引:0,他引:3  
B A Woda  C Padden 《Diabetes》1986,35(5):513-516
The response of BB diabetes-prone (DP) and W-line non-diabetes-prone rats to the T-cell mitogen concanavalin A (ConA) was measured. The W line was a good responder to ConA, whereas the DP was relatively unresponsive. This unresponsiveness could not be reversed with exogenous interleukin 2 (IL-2). The response of DP rats was enhanced by removing adherent cells. To directly test the response of BB T-cells, they were isolated by flow sorting. These experiments demonstrated that BB T-cells could mount a normal ConA response. The normal function of isolated BB T-cells suggested that they were under suppression. Suppressor activity could not be found in the OX8+ population but was found in the DP-adherent cell population. Adherent cells from the W line were not suppressive at the concentrations used. These results showed that the decreased mitogen responsiveness of BB T-cells was not due to an intrinsic T-cell abnormality but was due, in part, to suppression by adherent cells.  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