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   16045篇
  免费   1063篇
  国内免费   129篇
耳鼻咽喉   140篇
儿科学   470篇
妇产科学   454篇
基础医学   2482篇
口腔科学   278篇
临床医学   1325篇
内科学   3774篇
皮肤病学   380篇
神经病学   2243篇
特种医学   434篇
外科学   1454篇
综合类   31篇
一般理论   1篇
预防医学   920篇
眼科学   177篇
药学   1123篇
中国医学   32篇
肿瘤学   1519篇
  2024年   29篇
  2023年   204篇
  2022年   438篇
  2021年   735篇
  2020年   400篇
  2019年   494篇
  2018年   648篇
  2017年   470篇
  2016年   540篇
  2015年   604篇
  2014年   740篇
  2013年   974篇
  2012年   1391篇
  2011年   1394篇
  2010年   782篇
  2009年   709篇
  2008年   1170篇
  2007年   1060篇
  2006年   960篇
  2005年   855篇
  2004年   785篇
  2003年   691篇
  2002年   531篇
  2001年   58篇
  2000年   43篇
  1999年   61篇
  1998年   105篇
  1997年   66篇
  1996年   52篇
  1995年   42篇
  1994年   44篇
  1993年   21篇
  1992年   20篇
  1991年   17篇
  1990年   16篇
  1989年   14篇
  1988年   6篇
  1987年   10篇
  1986年   10篇
  1985年   8篇
  1984年   5篇
  1983年   6篇
  1982年   6篇
  1981年   5篇
  1980年   7篇
  1979年   4篇
  1978年   2篇
  1976年   1篇
  1975年   1篇
  1974年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
We evaluated the expression of T cell-restricted intracellular antigen (Tia-1), granzyme B, and perforin by lymphocytes and the degree of epithelial apoptosis in oral and cutaneous lichen planus (LP) in 51 untreated cases, including 27 oral LP (OLP) and 24 cutaneous LP (CLP) cases. The number of total dermal-positive lymphocytes in OLP and CLP was similar, indicating similar activity of the inflammatory process. Intraepithelial Tia-1-positive, perforin-positive, and granzyme B-positive lymphoid cells were more numerous in OLP than in CLP (P < .05). The epithelial cell apoptotic index (AI) was increased significantly in OLP (P < .05), particularly in erosive-atrophic variants. A linear correlation between AI and the mean +/- SEM number of intraepithelial and dermal perforin+ cells (6.85 +/- 2.44 and 27.48 +/- 10.19, respectively), per 10 high-power fields for OLP and for CLP (1.17 +/- 0.88 and 10.42 +/- 5.74, respectively), was found (intraepithelial, r = 0.50; dermal, r = 0.51; P < .01). These data suggest a pivotal role for perforin in triggering epithelial cell apoptosis. The differences of infiltrating cytotoxic cells and related AI observed in OLP and CLP are in keeping with the clinical behaviors that distinguish these LP variants.  相似文献   
13.
These studies investigated behavioral and hormonal responses to stress in developing mice. Experiment 1 examined the effects of 24-hr maternal deprivation on corticosterone (CORT) secretion and ultrasonic vocalization (UVZ) rate in 4-, 8-, and 12-day-old mice. At these ages, exposure to a novel environment resulted in minimal changes in CORT secretion. Maternal deprivation increased pups′ CORT secretion in an age-dependent fashion but did not affect their UVZ rate. The aim of experiment 2 was to test the effects of cholordiazepoxide (CDP), an anxyolytic compound, on CORT secretion and UVZ in both normally reared and in maternally deprived 8-day-old mice. CDP administration elevated CORT increases in deprived (DEP) animals. CDP affected UVZ only in nondcprived (NDEP) animals: UVZ ratewas decreased by high CDP doses Overall, these findings demonstrate that the infant mouse shows a period of stress hyp9oresponsiveness similar to the rat and that maternal presence contributes to inhibit adrenocorticalactivity. CDP administration, butnot novelty exposure, increased CORT secretion in 8-day- old normally reared mice suggesting that during the stress hyporesponsive period, the HPA axis is capable of responding only to specific stimuli. Changes in HPA axis activity and UVZ rateresulting from maternal deprivation and/or CDP challenge do not seem to be directly related. ©1994 John Wiley & Sons, Inc.  相似文献   
14.
A shift of physiological regulations from a homeostatic to a non-homeostatic modality characterizes the passage from non-NREM sleep (NREMS) to REM sleep (REMS). In the rat, an EEG index which allows the automatic scoring of transitions from NREMS to REMS has been proposed: the NREMS to REMS transition indicator value, NIV [J.H. Benington et al., Sleep 17 (1994) 28-36]. However, such transitions are not always followed by a REMS episode, but are often followed by an awakening. In the present study, the relationship between changes in EEG activity and hypothalamic temperature (Thy), taken as an index of autonomic activity, was studied within a window consisting of the 60s which precedes a state change from a consolidated NREMS episode. Furthermore, the probability that a transition would lead to REMS or wake was analysed. The results showed that, within this time window, both a modified NIV (NIV(60)) and the difference between Thy at the limits of the window (Thy(D)) were related to the probability of REMS onset. Both the relationship between the indices and the probability of REMS onset was sigmoid, the latter of which saturated at a probability level around 50-60%. The efficacy for the prediction of successful transitions from NREMS to REMS found using Thy(D) as an index supports the view that such a transition is a dynamic process where the physiological risk to enter REMS is weighted at a central level.  相似文献   
15.
16.
Nitric oxide (NO) is a candidate retrograde messenger in long-term potentiation (LTP). The NO metabolic pathway is expressed in the cerebellar granule cell layer but its physiological role remained unknown. In this paper we have investigated the role of NO in cerebellar mossy fiber-granule cell LTP, which has postsynaptic N-methyl-d-aspartate (NMDA) receptor-dependent induction. Pre- and postsynaptic current changes were simultaneously measured by using extracellular focal recordings, and NO release was monitored with an electrochemical probe in P21 rat cerebellar slices. High-frequency mossy fiber stimulation induced LTP and caused a significant NO release (6.2 +/- 2.8 nM; n = 5) in the granular layer that was dependent on NMDA receptor as well as on nitric oxide synthase (NOS) activation. Preventing NO production by perfusing the NOS inhibitor 100 microM NG-nitro-l-arginine (L-NNA), blocking extracellular NO diffusion by 10 microM MbO2, or inhibiting the NO target guanylyl cyclase (sGC) with 10 microM 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-dione (ODQ) prevented LTP. Moreover, the NO donor 10 microM 2-(N,N-diethylamino)-diazenolate-2-oxide.Na (DEA-NO) induced LTP, which was mutually occlusive with LTP generated by high-frequency stimulation, prevented by ODQ, and insensitive to NMDA channel blockade (50 microM APV + 25 microM 7-Cl-kyn) or interruption of mossy fiber stimulation. Thus NO is critical for LTP induction at the cerebellar mossy fiber-granule cell relay. Interestingly, LTP manipulations were accompanied by consensual changes in the presynaptic current, suggesting that NO acts as a retrograde signal-enhancing presynaptic terminal excitability.  相似文献   
17.
Secretion in neutrophils is thought to be regulated in different ways for the different granule types. Specific granules are endowed with proteins which are related to docking and fusion events and are absent on azurophilic granules. Furthermore, even if secretion of content from all neutrophil granules is a Ca(2+)-dependent process, a higher concentration of cytosolic calcium is required for azurophilic than for specific granule secretion. In this paper we show that human neutrophils and promyelocitic cells express neuronal calcium sensor-1 (NCS-1), a calcium binding protein involved in exocytosis in various cell types. Both mRNA and protein were found in mature cells and precursors. NCS-1 is shown to be mainly associated with azurophilic granules and, therefore could play an instrumental role in the calcium-dependent secretion of azurophilic granules.  相似文献   
18.
Mucosal leishmaniasis of the upper respiratory tract is usually associated with the visceral form or is found in immunosuppressed individuals. This report presents a case of isolated mucosal leishmaniasis in an immunocompetent patient, whose diagnosis mainly rested on histology and positive polymerase chain reaction result for Leishmania donovani in the laryngeal tissue. A 59-year-old man, who never lived outside Italy, showed a subglottic mucosal polypoid-like lesion. The typical morphological picture and positive polymerase chain reaction result for L donovani by DNA extracted from laryngeal biopsy specimens allowed the diagnosis of mucosal leishmaniasis. Specific amphotericin B therapy was started, resulting in clinical and endoscopic improvement. Increased knowledge about the histological and molecular tissue analysis of Leishmania enhances the diagnostic testing for mucosal leishmaniasis, as primary mucosal leishmaniasis may occur in both immunosuppresed and immunocompetent patients who travel to or reside in areas endemic for Leishmania.  相似文献   
19.
There is a global need to elucidate protective antigens expressed by the SARS-coronavirus (SARS-CoV). Monoclonal antibody reagents that recognise specific antigens on SARS-CoV are needed urgently. In this report, the development and immunochemical characterisation of a panel of murine monoclonal antibodies (mAbs) against the SARS-CoV is presented, based upon their specificity, binding requirements, and biological activity. Initial screening by ELISA, using highly purified virus as the coating antigen, resulted in the selection of 103 mAbs to the SARS virus. Subsequent screening steps reduced this panel to seventeen IgG mAbs. A single mAb, F26G15, is specific for the nucleoprotein as seen in Western immunoblot while five other mAbs react with the Spike protein. Two of these Spike-specific mAbs demonstrate the ability to neutralise SARS-CoV in vitro while another four Western immunoblot-negative mAbs also neutralise the virus. The utility of these mAbs for diagnostic development is demonstrated. Antibody from convalescent SARS patients, but not normal human serum, is also shown to specifically compete off binding of mAbs to whole SARS-CoV. These studies highlight the importance of using standardised assays and reagents. These mAbs will be useful for the development of diagnostic tests, studies of SARS-CoV pathogenesis and vaccine development.  相似文献   
20.
The frequencies of anti-interferon-beta (IFN-beta) antibody development reported to date in patients treated with different IFN-beta preparations are not readily comparable mainly because of differences in underlying diseases and assay methods. Thus, the frequency of neutralizing antibody (NAb) and binding antibody (BAb) development was analyzed in a sample of sera derived from a homogeneous group of relapsing-remitting multiple sclerosis (RRMS) patients treated with different IFN-beta preparations. The frequency of developing NAb and BAb to IFN-beta varied according to the IFN-beta given. Specifically, the NAb seroconversion frequency was significantly higher in patients treated with Betaferon, Schering AG, Berlin, Germany (31.3%) than in patients treated with both preparations of recombinant IFN-beta 1a (Rebif, Serono, Geneva, Switzerland [7.4%] or Avonex, Biogen, Cambridge, MA [6.3%]). Analysis of BAb seroconversion frequency in the same patients revealed that different IFN-beta preparations may also have different capability to induce BAb development and that BAb are produced during IFN-beta therapy at a significantly higher rate than NAb. Our main conclusion is that different human IFN-beta preparations may possess different immunogenicities, leading to varying frequency of development of antibody to IFN-beta in RRMS.  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