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   30174篇
  免费   1631篇
  国内免费   68篇
耳鼻咽喉   438篇
儿科学   1210篇
妇产科学   975篇
基础医学   4822篇
口腔科学   675篇
临床医学   2485篇
内科学   5931篇
皮肤病学   583篇
神经病学   3035篇
特种医学   1285篇
外国民族医学   14篇
外科学   4382篇
综合类   141篇
一般理论   3篇
预防医学   1659篇
眼科学   609篇
药学   1563篇
中国医学   20篇
肿瘤学   2043篇
  2022年   262篇
  2021年   437篇
  2020年   309篇
  2019年   402篇
  2018年   501篇
  2017年   427篇
  2016年   588篇
  2015年   594篇
  2014年   776篇
  2013年   966篇
  2012年   1458篇
  2011年   1553篇
  2010年   799篇
  2009年   835篇
  2008年   1351篇
  2007年   1451篇
  2006年   1348篇
  2005年   1397篇
  2004年   1223篇
  2003年   1186篇
  2002年   1085篇
  2001年   960篇
  2000年   997篇
  1999年   860篇
  1998年   406篇
  1997年   295篇
  1996年   245篇
  1995年   217篇
  1994年   204篇
  1993年   198篇
  1992年   533篇
  1991年   547篇
  1990年   520篇
  1989年   454篇
  1988年   416篇
  1987年   434篇
  1986年   423篇
  1985年   407篇
  1984年   294篇
  1983年   226篇
  1982年   155篇
  1981年   155篇
  1979年   281篇
  1978年   191篇
  1977年   163篇
  1976年   157篇
  1975年   174篇
  1974年   204篇
  1973年   174篇
  1972年   165篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
101.
The aim of this study was to characterize the role of the efflux transporter Mrp2 (Abcc2) in the pharmacokinetics of orally and intravenously administered pravastatin in rats. Eight Mrp2-deficient TR- rats and eight wild-type rats were given an oral dose of 20 mg/kg pravastatin. Four TR- animals and four wild-type animals were studied after intravenous administration of pravastatin (5 mg/kg). The TR(-) rats showed a 6.1-fold higher mean area under the plasma concentration-time curve (AUC) of pravastatin (p < 0.001) after oral administration and a 4.7-fold higher AUC (p < 0.01) after intravenous administration of pravastatin as compared with the wild-type animals. The mean systemic (total) clearance of pravastatin was 4.6-fold higher (39.2 versus 8.50 l/h/kg, p < 0.001) and the mean V 4.3-fold higher (14.1 versus 3.29 l/kg, p < 0.01) in the wild-type rats. The mean renal clearance of pravastatin in the TR(-) rats was 16.5-fold increased as compared with the wild-type animals (0.695 versus 0.042 l/h/kg, p < 0.05). The increased systemic exposure to oral pravastatin in the TR- rats was associated with a greater inhibitory effect on 3-hydroxy-3-methylglutaryl CoA reductase, as shown by smaller lathosterol to cholesterol concentration ratios. These results suggest that the reduced biliary pravastatin excretion in the Mrp2-deficient TR- rats is partly compensated for by increased urinary excretion of pravastatin. Furthermore, intestinal Mrp2 does not appear to play a major role in the oral absorption of pravastatin in normal rats.  相似文献   
102.
The occurrence of behavioural problems in a population-based series of children with infantile hydrocephalus (non-spina bifida) was analysed, using parent questionnaires. Children with both infantile hydrocephalus and mental retardation had significantly more behavioural problems compared with those with no mental retardation and controls. Inattentiveness and hyperactivity were particularly typical. No differences were found between children with infantile hydrocephalus and no mental retardation and the control group.  相似文献   
103.
Displacement of the surface of the cornea of bovine eyes after disruption of intact structures was investigated by means of holographic interferometry. Double-T-incisions of different depths were made with a diamond knife. Starting at about 80% of the incision depth there is a change in the central holographic interference fringe pattern. These effects can be clearly demonstrated by means of double-exposure holographic interferometry and real-time holographic interferometry. The stability of an existing corneal scar was analyzed by double-exposure holographic interferometry. The region of the scar showed a higher density of holographic interference fringes compared with the non-affected corneal areas, indicating a higher degree of elasticity. All eyes were investigated at an intraocular pressure of 1340 Pa (about 10 mmHg) and an intraocular pressure change of 10 Pa and 20 Pa. Further potential ophthalmic applications of holographic interferometry are discussed.  相似文献   
104.
Growth of Hodgkin cell lines in severely combined immunodeficient mice.   总被引:4,自引:0,他引:4  
No animal model exists for the in vivo growth of Hodgkin's-lymphoma-derived cells. Neither unmanipulated Hodgkin's-disease(HD)-derived cell lines nor primary biopsy tissue could be grown in nude mice. Since the severe combined immunodeficient (SCID) mouse has been reported to be a better recipient for transplanted human lymphatic tissue than the nude mouse, we tested whether SCID mice provide suitable conditions for the in vivo growth of HD cell lines. Tumorigenicity of HD cells was tested in untreated and pre-treated SCID mice and in another combined immunodeficient mouse strain, beige/nude/X-linked immunodeficient (BNX) mouse. SCID mice supported in vivo growth of the 6 HD cell lines tested (L428, L540, L591, DEV, HD-LM2, KM-H2). Only one of the 6 lines (DEV) was tumorigenic in BNX mice. No HD cell line proliferated in T-cell-deficient nude mice. Thus, in vivo growth of HD cell lines appeared to be related to the degree of host immunodeficiency. Additional growth supportive treatments such as fibrosarcoma co-transplantation, intraperitoneal mineral oil injection or immunosuppressive pre-treatment (anti-asialo-GMI-antibody injection) permitted growth of 3 additional HD cell lines in BNX mice. The immunophenotype and karyotype of explanted graft cells were identical to the original cell lines. Our experiments describe an effective and reproducible xenograft model for growth of Hodgkin's-disease-derived cell lines. This may be of value for elucidating the growth characteristics of Hodgkin's-lymphoma-derived cells as well as for testing new therapeutic regimens.  相似文献   
105.
Four patients with mycotic aneurysm of the extracranial carotid artery, the innominate artery, the ascending aorta, and the infrarenal aorta were treated with local implantation of antibiotic-releasing carriers after resection of the aneurysm, excision of all infected tissue, and in situ reconstruction by prosthetic graft replacement in two patients and patch plasty in two patients. The patient with a mycotic aneurysm of the ascending aorta was operated on again 1 month after the first operation because of a second mycotic aneurysm located on the aortic arch. No early or late signs of recurrent infection were seen on clinical and laboratory postoperative follow-up done between 9 and 16 months or on duplex scan or computed tomography done at these times. Implantation of antibiotic-releasing carriers after débridement of all infected tissue and in situ reconstruction for treatment of mycotic aneurysm was performed successfully in four patients with this life-threatening condition.  相似文献   
106.
107.
The beta-amyloid (Abeta) precursor protein (APP) is cleaved sequentially by beta-site of APP-cleaving enzyme (BACE) and gamma-secretase to release the Abeta peptides that accumulate in plaques in Alzheimer's disease (AD). GGA1, a member of the Golgi-localized gamma-ear-containing ARF-binding (GGA) protein family, interacts with BACE and influences its subcellular distribution. We now report that overexpression of GGA1 in cells increased the APP C-terminal fragment resulting from beta-cleavage but surprisingly reduced Abeta. GGA1 confined APP to the Golgi, in which fluorescence resonance energy transfer analyses suggest that the proteins come into close proximity. GGA1 blunted only APP but not notch intracellular domain release. These results suggest that GGA1 prevented APP beta-cleavage products from becoming substrates for gamma-secretase. Direct binding of GGA1 to BACE was not required for these effects, but the integrity of the GAT (GGA1 and TOM) domain of GGA1 was. GGA1 may act as a specific spatial switch influencing APP trafficking and processing, so that APP-GGA1 interactions may have pathophysiological relevance in AD.  相似文献   
108.
BACKGROUND & AIMS: Refractory celiac disease (RCD) may be subdivided into RCD types I and II with phenotypically normal and aberrant intraepithelial T-cell populations, respectively. In RCD II, transition into enteropathy-associated T-cell lymphoma (EATL) is seen frequently. We have evaluated the effect of cladribine (2-CDA), a purine analogue inducing T-cell depletion, on clinical, histopathologic, and immunologic parameters, as well as the toxicity and side effects in a group of RCD II patients. METHODS: Between 2000 and 2005, 17 patients were included (8 men, 9 women). All patients had a clonal rearrangement of the T-cell receptor gamma gene and immunophenotyping showed an aberrant T-cell population lacking surface expression of CD3, CD8, and T-cell receptor alphabeta, in the presence of expression of surface CD103 and intracytoplasmic CD3. Treatment consisted of 2-CDA (0.1 mg/kg/day) intravenously for 5 days, given in 1-3 courses every 6 months depending on the response. RESULTS: All patients tolerated 2-CDA without serious side effects. Six patients (35.8%) showed a clinical improvement (weight gain, improvement of diarrhea, and hypoalbuminemia). In 10 patients (58.8%) a significant histologic improvement and in 6 patients (35.2%) a significant decrease in aberrant T cells was seen. Seven patients (41.1%) developed EATL and died subsequently. One patient died of progressive refractory state with emaciation. CONCLUSIONS: Treatment with 2-CDA in RCD II is feasible, well tolerated, and can induce clinical and histologic improvement as well as a significant decrease of aberrant T cells in a subgroup of patients, albeit it does not prevent EATL development. However, the earlier reported potential risk of precipitating an overt lymphoma should be taken into consideration.  相似文献   
109.
Abstract Background: In recent years, biomaterials are being found and frequently utilized in bone defects. They have also gained significant precedence in hand surgery. Objectives: The respective requirements for such replacement material will be cited and acknowledged in this article. The individual material groups will also be referred to in this review. An introduction to some of the customary bone replacement materials will be cited and concluded with a corresponding recommendation. Conclusion: The implantation of autologous cancellous bone is still regarded today as the “gold standard”. Nevertheless, the usage of bone replacement material can be an enormous advantage in certain indications. The original article can be found online at There was an error in the author’s affiliation and the address for correspondence was incomplete. Please note the correct institution and complete address: Department of Orthopedics and Traumatology, Hand-, Foot- and Reconstructive Surgery, Kreiskrankenhaus Gummersbach GmbH, Germany. Alexander von Friesen, MD Department of Orthopedics and Traumatology, Hand-, Foot- and Reconstructive Surgery Kreiskrankenhaus Gummersbach GmbH Wilhelm-Breckow-Allee 20 51643 Gummersbach Germany Phone (+49/2261) 171-575, Fax -449 e-mail: Friesen@kkh-gummersbach.de  相似文献   
110.
Treatment with combined IL-2 and alpha-IFN has resulted in synergistic antitumour efficacy in animal studies. The mechanisms responsible for this synergy remain unclear. In this study, several immune parameters which might be involved in mediating antitumour activity have been monitored serially in 15 patients with advanced malignant melanoma or renal cell cancer during treatment with concurrent IL-2 and alpha-IFN. Both drugs were given subcutaneously in low to moderate (outpatient) dosages but for a prolonged duration. This treatment resulted in remarkable immunomodulation. In vivo induction of cytotoxicity against K562 and Daudi target cells was consistently seen, and percentages of peripheral blood cells expressing CD 25 (IL-2 receptor) and CD 56 (Leu-19) increased. In vitro proliferation of lymphocytes in response to IL-2 was enhanced during the treatment periods, whereas spontaneous proliferation was inhibited. Moreover, correlations between immune parameters and subsequent clinical responses were present in the early phase of the study. Cytotoxicity levels generated in vivo as well as the percentage of CD 56+ lymphocytes were higher in patients who responded to treatment than in non-responders. In contrast, responders had lower levels of CD 25+ cells. These findings indicate that it might be possible to select patients who are likely to benefit from prolonged immunotherapy.  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