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   1487篇
  免费   58篇
  国内免费   71篇
耳鼻咽喉   23篇
儿科学   92篇
妇产科学   15篇
基础医学   278篇
口腔科学   28篇
临床医学   229篇
内科学   213篇
皮肤病学   49篇
神经病学   79篇
特种医学   193篇
外科学   126篇
综合类   32篇
预防医学   43篇
眼科学   4篇
药学   124篇
肿瘤学   88篇
  2022年   10篇
  2021年   22篇
  2020年   19篇
  2019年   26篇
  2018年   22篇
  2017年   19篇
  2016年   22篇
  2015年   43篇
  2014年   51篇
  2013年   68篇
  2012年   61篇
  2011年   60篇
  2010年   54篇
  2009年   50篇
  2008年   54篇
  2007年   88篇
  2006年   57篇
  2005年   30篇
  2004年   50篇
  2003年   36篇
  2002年   40篇
  2001年   34篇
  2000年   40篇
  1999年   42篇
  1998年   33篇
  1997年   37篇
  1996年   34篇
  1995年   27篇
  1994年   24篇
  1993年   22篇
  1992年   15篇
  1991年   18篇
  1990年   19篇
  1989年   31篇
  1988年   33篇
  1987年   21篇
  1986年   18篇
  1985年   23篇
  1984年   10篇
  1982年   17篇
  1981年   17篇
  1980年   14篇
  1979年   12篇
  1978年   16篇
  1977年   21篇
  1976年   19篇
  1975年   15篇
  1972年   15篇
  1968年   9篇
  1966年   9篇
排序方式: 共有1616条查询结果,搜索用时 15 毫秒
41.

Background  

There is currently an unprecedented expressed need and demand for estimates of maternal mortality in developing countries. This has been stimulated in part by the creation of a Millennium Development Goal that will be judged partly on the basis of reductions in maternal mortality by 2015.  相似文献   
42.
43.
Klebsiella pneumoniae is among the most common Gram‐negative bacteria that cause pneumonia. Gp96 is an endoplasmic reticulum chaperone that is essential for the trafficking and function of Toll‐like receptors (TLRs) and integrins. To determine the role of gp96 in myeloid cells in host defence during Klebsiella pneumonia, mice homozygous for the conditional Hsp90b1 allele encoding gp96 were crossed with mice expressing Cre‐recombinase under control of the LysM promoter to generate LysMcre‐Hsp90b1‐flox mice. LysMcre‐Hsp90b1‐flox mice showed absence of gp96 protein in macrophages and partial depletion in monocytes and granulocytes. This was accompanied by almost complete absence of TLR2 and TLR4 on macrophages. Likewise, integrin subunits CD11b and CD18 were not detectable on macrophages, while being only slightly reduced on monocytes and granulocytes. Gp96‐deficient macrophages did not release pro‐inflammatory cytokines in response to Klebsiella and displayed reduced phagocytic capacity independent of CD18. LysMcre‐Hsp90b1‐flox mice were highly vulnerable to lower airway infection induced by K. pneumoniae, as reflected by enhanced bacterial growth and a higher mortality rate. The early inflammatory response in Hsp90b1‐flox mice was characterized by strongly impaired recruitment of granulocytes into the lungs, accompanied by attenuated production of pro‐inflammatory cytokines, while the inflammatory response during late‐stage pneumonia was not dependent on the presence of gp96. Blocking CD18 did not reproduce the impaired host defence of LysMcre‐Hsp90b1‐flox mice during Klebsiella pneumonia. These data indicate that macrophage gp96 is essential for protective immunity during Gram‐negative pneumonia by regulating TLR expression. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.  相似文献   
44.
BACKGROUND: Fungal components can cause allergic symptoms either through inhalation, ingestion or contact. Whereas respiratory allergy is thought to be induced by spores, allergic reactions following ingestion are attributed to other parts of the mushroom. Reports of food-related allergic reactions due to the edible mushroom Boletus edulis have occasionally been reported. OBJECTIVE: The aim of the study was to investigate whether separate allergens may be detected in alimentary allergy to Boletus edulis. METHODS: Sera of two subjects, one with recurrent anaphylaxis and the other with a predominantly oral allergy syndrome following ingestion of Boletus edulis, have been analysed by a time-course digestion assay using simulated gastric fluid and by SDS-PAGE immunoblotting. Sera of four Boletus edulis skin prick test-negative subjects and all without clinical symptoms to ingested Boletus edulis served as controls. RESULTS: In lyophilized Boletus edulis extract, at least four water-soluble proteins were detected, the most reactive at 55 kDa and at 80 kDa. Following the time-course digestion assay, IgE binding was found to a 75-kDa protein, but only if the sera of the subject with recurrent anaphylaxis was used. CONCLUSION: The data indicate that Boletus edulis can cause an IgE-mediated food allergy due to a digestion-stabile protein at 75 kDa. No IgE immune response to this protein was detected in the serum of a subject with respiratory allergy and oral allergy syndrome to Boletus edulis nor in control sera.  相似文献   
45.
Detectors used for positron emission tomography (PET) provide fast, randomly distributed signals that need to be digitized for further processing. One possibility is to sample the signals at the peak initiated by a trigger from a constant fraction discriminator (CFD). For PET detectors, simultaneous acquisition of many channels is often important. To develop and evaluate novel PET detectors, a flexible, relatively low cost and high performance laboratory data acquisition (DAQ) system is therefore required. The use of dedicated DAQ systems, such as a multi-channel analysers (MCAs) or continuous sampling boards at high rates, is expensive. This work evaluates the suitability of well-priced peripheral component interconnect (PCI)-based 8-channel DAQ boards (PD2-MFS-8 2M/14 and PD2-MFS-8-500k/14, United Electronic Industries Inc., Canton, MA, USA) for signal acquisition from novel PET detectors. A software package was developed to access the board, measure basic board parameters, and to acquire, visualize, and analyse energy spectra and position profiles from block detectors. The performance tests showed that the boards input linearity is >99.2% and the standard deviation is <9 mV at 10 V for constant signals. Synchronous sampling of multiple channels and external synchronization of more boards are possible at rates up to 240 kHz per channel. Signals with rise times as fast as 130 ns (<2 V amplitude) can be acquired without slew rate effects. However, for signals with amplitudes of up to 5 V, a rise time slower than 250 ns is required. The measured energy resolution of a lutetium oxyorthosilicate (LSO)-photomultiplier tube (PMT) detector with a 22Na source was 14.9% (FWHM) at 511 keV and is slightly better than the result obtained with a high-end single channel MCA (8000A, Amptek, USA) using the same detector (16.8%). The crystals (1.2 x 1.2 x 12 mm3) within a 9 x 9 LSO block detector could be clearly separated in an acquired position profile. Thus, these boards are well suited for data acquisition with novel detectors developed for nuclear imaging.  相似文献   
46.
47.
48.
49.
We report a rare case of early-stage endometrial adenocarcinoma in a 22 year old nullipara with polycystic ovaries undergoing conservative treatment. Pretreatment evaluation including tumour grade, depth of myometrial invasion, tumour size, hormone receptor status and flow cytometric analysis indicated a favourable prognosis. The patient underwent repeat endometrial curettage and a 6 month period of therapy with megestrol acetate and tamoxifen. A combination contraceptive pill was then prescribed to ensure withdrawal of the menstrual cycle thereafter. Now, 1 year after the last curettage, there is no evidence of disease. During the treatment period, hysteroscopy allowed for a more precise approach in panoramically examining the tumour nest in the endometrial cavity, and the subsequent endometrial response to hormone therapy. Laparoscopy using bulldog clamps applied to the isthmic portion of the Fallopian tubes prevented i.p. spread of endometrial tissue from retrograde regurgitation during hysteroscopy. Laparoscopic ovarian electrocautery resulted in the reduction of abnormal hypervascularization on the surface of polycystic ovaries postoperatively but caused a peri-ovarian adhesion complication. It is interesting that this case posed a unique opportunity to demonstrate the tumour regression under the assistance of laparoscopy and hysteroscopy.   相似文献   
50.
Pichler WJ  Tilch J 《Allergy》2004,59(8):809-820
Diagnosis of drug hypersensitivity is difficult, as an enormous amount of different drugs can elicit various immune-mediated diseases with distinct pathomechanism. The lymphocyte transformation test (LTT) measures the proliferation of T cells to a drug in vitro--from which one concludes to a previous in vivo reaction due to a sensitization. This concept of the LTT has been confirmed by the generation of drug-specific T-cell clones and the finding that drugs can directly interact with the T-cell receptor, without previous metabolism or need to bind to proteins. In this review, technical aspects and usefulness of this test for the diagnosis of drug hypersensitivity are discussed. The main advantage of this test is its applicability with many different drugs in different immune reactions, as drug-specific T cell are almost always involved in drug hypersensitivity reactions. Its main disadvantages are that an in vitro proliferation of T cells to a drug is difficult to transfer to the clinical situation and that the test per se is rather cumbersome and technically demanding. In addition, its sensitivity is limited (for beta-lactam allergy it is in the range of 60-70%), - although at least in our hands - it is higher than of other tests for drug hypersensitivity diagnosis. Consequently, drug hypersensitivity diagnosis needs to rely on a combination of history and different tests, as none of the single tests available has per se a sufficiently good sensitivity. Within this setting, the LTT has proven to be a useful test for the diagnosis of drug hypersensitivity reactions and helped to better understand these reactions. Further work on the simplification of this test and systematic evaluation of its sensitivity and specificity in some main groups of drugs are necessary to make this test more widely available.  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