全文获取类型
收费全文 | 4865篇 |
免费 | 268篇 |
国内免费 | 12篇 |
专业分类
耳鼻咽喉 | 42篇 |
儿科学 | 137篇 |
妇产科学 | 247篇 |
基础医学 | 711篇 |
口腔科学 | 108篇 |
临床医学 | 352篇 |
内科学 | 968篇 |
皮肤病学 | 70篇 |
神经病学 | 420篇 |
特种医学 | 136篇 |
外科学 | 678篇 |
综合类 | 83篇 |
一般理论 | 4篇 |
预防医学 | 425篇 |
眼科学 | 122篇 |
药学 | 298篇 |
中国医学 | 16篇 |
肿瘤学 | 328篇 |
出版年
2023年 | 41篇 |
2022年 | 74篇 |
2021年 | 198篇 |
2020年 | 92篇 |
2019年 | 129篇 |
2018年 | 158篇 |
2017年 | 104篇 |
2016年 | 118篇 |
2015年 | 139篇 |
2014年 | 176篇 |
2013年 | 235篇 |
2012年 | 367篇 |
2011年 | 354篇 |
2010年 | 184篇 |
2009年 | 146篇 |
2008年 | 287篇 |
2007年 | 275篇 |
2006年 | 265篇 |
2005年 | 256篇 |
2004年 | 236篇 |
2003年 | 200篇 |
2002年 | 203篇 |
2001年 | 41篇 |
2000年 | 43篇 |
1999年 | 33篇 |
1998年 | 44篇 |
1997年 | 45篇 |
1996年 | 25篇 |
1995年 | 28篇 |
1994年 | 41篇 |
1993年 | 31篇 |
1992年 | 32篇 |
1991年 | 28篇 |
1990年 | 32篇 |
1989年 | 23篇 |
1988年 | 31篇 |
1987年 | 22篇 |
1986年 | 25篇 |
1985年 | 17篇 |
1984年 | 20篇 |
1983年 | 17篇 |
1982年 | 24篇 |
1981年 | 20篇 |
1980年 | 21篇 |
1979年 | 24篇 |
1978年 | 17篇 |
1976年 | 14篇 |
1975年 | 14篇 |
1970年 | 10篇 |
1969年 | 10篇 |
排序方式: 共有5145条查询结果,搜索用时 203 毫秒
21.
22.
John R. Wanamaker Dennis H. Kraus Charles V. Biscotti Isaac Eliachar 《Head & neck》1994,16(6):589-593
Background. Nasopharyngeal carcinoma has a variety of presentations. However, in more than 50% of cases it may present with serous otitis or cervical metastases. Although the metastases usually occur in the neck, the lymphatic network of the parotid may also serve as a site for the metastatic deposits. We present a case in which the initial manifestation of nasopharyngeal carcinoma of the lymphoepithelioma type was a parotid mass. Methods. Case study. Results. A patient who was initially seen with an isolated parotid mass was found to have an undifferentiated carcinoma of the lymphoepithelial type. Further evaluation identified an occult nasopharyngeal carcinoma, and the patient underwent radiotherapy. Conclusions. A diagnosis of a malignant lymphoepithelial lesion of the parotid gland or undifferentiated carcinoma of the lymphoepithelial type mandates a search for an occult primary nasopharyngeal tumor. 相似文献
23.
24.
Santosh Isaac Poonnoose Raju P Manjooran John Mathew Pranatartiharan Ramachandran 《Journal of clinical neuroscience》2007,14(3):281-283
We report an unusual case of chronic subdural haematoma (CSH) associated with cerebrospinal fluid (CSF) rhinorrhoea emphasizing the importance of managing both conditions simultaneously. A 59- year-old man presented with watery discharge from the right nostril, of 2 months duration. MRI of the brain showed a CSH in the left fronto-parietal region with significant mass effect. There was an arachnoidocoele with a defect in the planum sphenoidale. He first underwent a burr hole evacuation of the CSH following which the CSF rhinorrhea did not subside, even with bed rest. Transnasal endoscopic closure of the CSF dural fistula was done. On the first post-operative day, he was disoriented and a CT scan showed a recollection of the subdural haematoma that required repeat evacuation. The patient was asymptomatic at discharge. To our knowledge this is the first reported case of CSF rhinorrhoea associated with CSH. Simultaneous closure of the CSF dural fistula at the time of evacuation of a coexisting CSH would be the optimal management. 相似文献
25.
Effects of gastric bypass procedures on bone mineral density,calcium, parathyroid hormone,and vitamin d 总被引:2,自引:0,他引:2
Jason M. Johnson James W. Maher Isaac Samuel Deborah Heitshusen Cornelius Doherty Robert W. Downs 《Journal of gastrointestinal surgery》2005,9(8):1106-1111
Weight loss after gastric bypass procedures has been well studied, but the long-term metabolic sequelae are not known. Data
on bone mineral density (BMD), calcium, parathyroid hormone, and vitamin D were collected preoperatively and at yearly intervals
after gastric bypass procedures. A total of 230 patients underwent preoperative BMD scans. Fifteen patients were osteopenic
preoperatively, and three patients subsequently developed osteopenia postoperatively within the first year. No patient had
or developed osteoporosis. At 1 year, total forearm BMD decreased by 0.55% (n = 91; P = .03) and radius BMD had increased overall by 1.85% (n = 23; P = .008); both total hip and lumbar spine BMD decreased by
9.27% (n = 22; P < .001) and 4.53% (n = 31; P < .001), respectively. By the second postoperative year, BMD in the total forearm had decreased an additional 3.62% (n =
14; P<.001), whereas radius BMD remained unchanged. Although total hip and lumbar spine BMD significantly decreased at 1 year,
by year 2 both total hip and lumbar spine BMD only slightly decreased and were not significantly different from before the
operation. Serum calcium decreased from 9.8 mg/dL to 9.2 during the first year (not significant [NS]) and then to 8.8 (NS)
by the second year. Parathyroid hormone increased from 59.7 pg/mL (nl 10-65 pg/mL) preoperatively to 63.1 during year 1 (NS)
and continued to increase to 64.7 by year 2 (NS). No difference was noted among levels of 25-hydroxy vitamin D preoperatively
(25.2 ng/mL; nl 10-65 ng/mL), at 1 year (34.4), and at 2 years (35.4). Our data indicate that bone loss is highest in the
first year after gastric bypass with stabilization, and that, in some cases, there is an increase in bone density after the
first year.
Presented at the Forty-Sixth Annual Meeting of The Society for Surgery of the Alimentary Tract, Chicago, Illinois, May 14–18,
2005 (oral presentation). 相似文献
26.
During embryonic development, morphogenetic gradients can specify the formation of gene expression territories. Here, we explore possible commonalities between pattern formation in the Drosophila blastoderm and murine pituitary. Shared principles include the need for positive feedback involving fate-determining genes to maintain a differentiated state, and the existence of intra- or extracellular inhibitory signals that improve spatial resolution of neighboring territories. The precision of spatial segregation is, however, limited by stochastic gene expression. Variability in gene expression at territory boundaries might give rise to a poorly differentiated pool of cells, which could harbor stem-like properties. The ideas outlined here deserve further theoretical and experimental exploration. 相似文献
27.
Maria B Isaac Michael T Isaac 《Neuropsychopharmacology》2003,28(11):2049; author reply 2052-2049; author reply 2053
28.
Eliezer Masliah Margaret Mallory Nianfeng Ge Michael Alford Isaac Veinbergs Allen D. Roses 《Experimental neurology》1995,136(2)
Apolipoprotein E (apoE) is involved in the development and regeneration of the central nervous system (CNS). ApoE may also be necessary to maintain the integrity of the synapto-dendritic complexity. We analyzed the synaptic alterations in the CNS of apoE-deficient (knockout) mice during the aging process. In apoE-deficient homozygous mice, there was an age-dependent 15 to 40% loss of synaptophysin-immunoreactive nerve terminals and microtubule-associated protein 2-immunoreactive dendrites in the neocortex and hippocampus, when compared to controls. Dendritic alterations were observed as early as 4 months of age. Ultrastructural analysis revealed extensive dendritic vacuolization and disruption of the endomembrane system and cytoskeleton in apoE-deficient homozygous mice. Further immunocytochemical studies of the neuronal cytoskeleton showed that in apoE-deficient mice there was a decrease in the immunoreactivity of α and β tubulin (but not kinesin) in the cell bodies and processes. These results support the contention that apoE might play an important role in maintaining the stability of the synapto-dendritic apparatus and that altered or deficient functioning of this molecule could underlie the synaptic and cytoskeletal alterations in Alzheimer's disease. 相似文献
29.
Ecdysteroid levels detected by RIA in extracts of mature ovaries from Periplaneta americana increased approximately fourfold (53 +/- 10 to 184 +/- 38 ng/g; +/- SEM, n = 3) on treatment with Helix pomatia "sulphatase" enzymes. HPLC analysis showed that this increase in immunoreactivity resulted from the hydrolysis of six apolar compounds that cochromatographed with the ecdysteroid esters previously shown to be present in newly laid oothecae (A1, A2, A3, A4, A5, and A6; A. J. Slinger, L. N. Dinan, and R. E. Isaac (1986). Insect Biochem. 16 (i), 115-119). Intact ovaries cultured in saline were able to take up [3H]ecdysone from the medium and synthesize ecdysone esters, most of which cochromatographed with immunoreactive peaks from ovaries and oothecae. Crude homogenates and membranes prepared from mature ovaries were also able to esterify ecdysone in vitro. The enzyme activity associated with a high-speed pellet was greatly enhanced by the addition of coenzyme A fatty acyl esters, each reaction resulting in the synthesis of a single major metabolite. The three esters formed on incubating ecdysone with coenzyme A-palmitate, -lineate, and -oleate could be characterized by their retention times on HPLC which were identical to compounds A2, A5, and A6, respectively. These compounds were the three quantitatively important immunoreactive esters found in ovaries and newly laid oothecae. The data presented indicates that ovaries can esterify ecdysone with palmitic, linoleic, and oleic acids and that these apolar derivatives are transferred to the egg. The esters appear to be different from the ecdysone 22-fatty acyl esters that have been isolated from ticks and other insects. 相似文献
30.
Nadir Askenasy Jeremiah Stein Isaac Yaniv Daniel L Farkas 《Biology of blood and marrow transplantation》2003,9(8):496-504
The early stages of homing, seeding, and engraftment of hematopoietic stem and progenitor cells are poorly characterized. We have developed an optical technique that allows in vivo tracking of transplanted, fluorescent-tagged cells in the host femurs. In this study we used fluorescence microscopy to monitor the topologic and chronologic patterns of hematopoietic cell seeding in the femoral bone marrow (BM) of mice. PKH-labeled cells homed to the femur within minutes after injection into a peripheral vein. Most cells drifted within the marrow space and gradually seeded in clusters close to the endosteal surface of the epiphyseal cortex. Three days after transplantation 85% to 94% (14%) of PKH-labeled cells in the femoral marrow were located within 100 microm of the epiphyseal bone surface (P <.001 versus the more central cells), whereas labeled cells were absent in the femoral diaphysis. Primary seeding of juxtaendosteal, epiphyseal marrow occurred independently of recipient conditioning (myeloablated and nonconditioned hosts), donor-recipient antigen disparity, or the phenotype of the injected cells (whole BM and lineage-negative cells) and was consistently observed in secondary recipients of BM-homed cells. Seeding in regions close to the epiphyseal bone was also observed in freshly excised femurs perfused ex vivo and in femurs assessed without prior placement of optical windows, indicating that the site of primary seeding was not affected by surgical placement of optical windows. Four to 5 days after transplantation, cellular clusters appeared in the more central regions of the epiphyses and in the diaphyses. Centrally located cells showed decreased PKH fluorescence, suggesting that they were progeny of the seeding cells, and brightly fluorescent cells (quiescent first-generation seeding cells) were observed close to the bone surface for as long as 24 days after transplantation. These data indicate that the periphery of the femoral marrow hosts primary seeding and that quiescent cells continue to reside in the periphery for weeks and do not divide. The site of proliferation of transplanted cells is the center of the marrow space. 相似文献