全文获取类型
收费全文 | 2908篇 |
免费 | 194篇 |
国内免费 | 51篇 |
专业分类
耳鼻咽喉 | 16篇 |
儿科学 | 94篇 |
妇产科学 | 148篇 |
基础医学 | 355篇 |
口腔科学 | 78篇 |
临床医学 | 373篇 |
内科学 | 583篇 |
皮肤病学 | 47篇 |
神经病学 | 217篇 |
特种医学 | 220篇 |
外科学 | 246篇 |
综合类 | 46篇 |
预防医学 | 151篇 |
眼科学 | 111篇 |
药学 | 283篇 |
1篇 | |
中国医学 | 10篇 |
肿瘤学 | 174篇 |
出版年
2023年 | 10篇 |
2022年 | 19篇 |
2021年 | 44篇 |
2020年 | 23篇 |
2019年 | 36篇 |
2018年 | 63篇 |
2017年 | 41篇 |
2016年 | 49篇 |
2015年 | 64篇 |
2014年 | 86篇 |
2013年 | 111篇 |
2012年 | 160篇 |
2011年 | 156篇 |
2010年 | 113篇 |
2009年 | 124篇 |
2008年 | 134篇 |
2007年 | 129篇 |
2006年 | 110篇 |
2005年 | 121篇 |
2004年 | 101篇 |
2003年 | 101篇 |
2002年 | 74篇 |
2001年 | 76篇 |
2000年 | 77篇 |
1999年 | 71篇 |
1998年 | 101篇 |
1997年 | 99篇 |
1996年 | 67篇 |
1995年 | 61篇 |
1994年 | 45篇 |
1993年 | 50篇 |
1992年 | 59篇 |
1991年 | 37篇 |
1990年 | 38篇 |
1989年 | 53篇 |
1988年 | 52篇 |
1987年 | 54篇 |
1986年 | 46篇 |
1985年 | 31篇 |
1984年 | 31篇 |
1983年 | 28篇 |
1982年 | 22篇 |
1980年 | 17篇 |
1979年 | 13篇 |
1978年 | 17篇 |
1977年 | 19篇 |
1976年 | 17篇 |
1973年 | 15篇 |
1972年 | 14篇 |
1970年 | 10篇 |
排序方式: 共有3153条查询结果,搜索用时 31 毫秒
21.
Lesley Barclay RN CM BA MEd Louise Everitt RN CM Post Grad Dip-Comm Health Frances Rogan RN CM B App S M Com Nurs Virginia Schmied RN CM BA MA Hons Aileen Wyllie RN CM BA MHPEd 《Journal of advanced nursing》1997,25(4):719-728
This paper presents the results of a qualitative study conducted by midwife researchers into women's experience of new motherhood. Data were collected using focus groups involving 55 first-time mothers and analysed using grounded theory method. The analysis produced six categories: 'realizing', 'unready', 'drained', 'aloneness', 'loss' and 'working it out'. The core category, 'becoming a mother', integrates all other categories and encapsulates the process of change experienced by women. Also explained are factors mediating the often distressing experience of becoming a mother. The analysis provides a conceptualization of early motherhood enabling the development of strategies for midwives, nurses and others helping women negotiate this challenge. 相似文献
22.
Sialyltransferase activity (EC 2.4.99.6) was measured in the microsomal fraction of colorectal cancer cell lines using an assay based on the incorporation of [14C]CMP-sialic acid into asialofetuin. In the poorly differentiated lines MIP101 and Clone A, sialyltransferase activity had a Vmax of 0.36 and 0.31 nmol/mg protein/h, respectively, while the moderately differentiated to well-differentiated cell lines HT-29, CCL188, and CX-1 had Vmaxs of 2.46, 1.05, and 1.24 nmol/mg protein/h, respectively. All cell lines tested had a Km of 15.4 (+/- 0.7)(SD) mumol/liter. The better differentiated cells had higher levels of sialyltransferase activity, which correlated with their higher levels of sialic acid and their enhanced ability to form liver metastases in the nude mouse following intrasplenic injection compared to the poorly differentiated cell lines. Treatment of the cell lines with KI-8110, a CMP-sialic acid derivative which prevents incorporation of sialic acid into glycoconjugates, resulted in reduced formation of hepatic metastases by the colorectal carcinoma cell lines in the nude mouse model. It is suggested that reduced sialylation of adhesion molecules such as carcinoembryonic antigen may change the biology of the tumor cell, one consequence of which is the prevention of implantation of the cells into distant sites, resulting in a reduced incidence of metastases. 相似文献
23.
Structure-activity studies of 20-deoxo-20-amino derivatives of tylosin-related macrolides 总被引:1,自引:0,他引:1
H A Kirst K E Willard M Debono J E Toth B A Truedell J P Leeds J L Ott A M Felty-Duckworth F T Counter E E Ose 《The Journal of antibiotics》1989,42(11):1673-1683
Reductive amination of the C-20 aldehyde group of tylosin and related macrolides yielded a large series of derivatives with potentially useful antibiotic properties. Evaluation of these new compounds was conducted on the basis of: 1) Broad antimicrobial spectrum in vitro, with particular emphasis on inhibition of Pasteurella multocida and Pasteurella haemolytica; 2) in vivo efficacy, especially when given orally, against P. multocida in experimental infections in chicks; and 3) bioavailability after oral administration to laboratory animals. The most useful activity was found within a series of derivatives produced by reductive amination of desmycosin with secondary amines. 相似文献
24.
Summary— Experiments were designed to determine whether or not indapamide, an antihypertensive agent with vasodilator properties, inhibits endothelium-dependent contractions. Rings of aortae with and without endothelium from spontaneously hypertensive rats (SHR) were suspended in conventional organ chambers for the measurement of isometric force. Acetylcholine and adenosine diphosphate-β-S in the presence of a nitric oxide synthase inhibitor, caused endothelium-dependent contractions, which were inhibited by indapamide. The compound (10−4 M) also slightly reduced the contractions of rings without endothelium evoked by U-46,619, which activates thromboxane-endoperoxide receptors. These results demonstrate that indapamide inhibits endothelium-dependent contractions in the SHR aorta, and suggest that the inhibition is due, at least in part, to the action of the drug on the hypertensive vascular smooth muscle. 相似文献
25.
Rhesus monkeys have a genetic locus which has a major influence on reactivity in mixed lymphocyte cultures (MLR). This MLR locus is closely linked to the RhL–A system2 , which controls the serologically defined histocompatibility antigens of this species. Three cases of recombination between RhL–A and the MLR region are described. Consequently, the MLR locus is located outside the RhL–A region proper, possibly adjacent to the locus defining the antigens of the 1st series. The recombination frequency between the MLR and RhL–A regions of rhesus monkeys is similar to that found for the analogous systems of man.
Inhibition of MLR can be achieved by pre-incubation of responder or stimulator cells with cytotoxic anti-RhL–A sera. Such inhibition is highly specific and probably caused by an interaction of the sera with RhL–A surface antigens, not with MLR determinants. Yet, there is circumstantial evidence that non-cytotoxic sera can be produced which inhibit MLR, presumably by affecting MLR determinants on the cell surface.
The relevance of MLR to histocompatibility and the genetic control of the immune response of rhesus monkeys to synthetic antigens, are the subjects of current studies which are briefly discussed. 相似文献
Inhibition of MLR can be achieved by pre-incubation of responder or stimulator cells with cytotoxic anti-RhL–A sera. Such inhibition is highly specific and probably caused by an interaction of the sera with RhL–A surface antigens, not with MLR determinants. Yet, there is circumstantial evidence that non-cytotoxic sera can be produced which inhibit MLR, presumably by affecting MLR determinants on the cell surface.
The relevance of MLR to histocompatibility and the genetic control of the immune response of rhesus monkeys to synthetic antigens, are the subjects of current studies which are briefly discussed. 相似文献
26.
27.
Targeted gene disruption of murine CD7 总被引:2,自引:0,他引:2
CD7 is a 40 kDa type I transmembrane glycoprotein member of the Ig
superfamily. CD7 is a marker of mature human T cells and NK cells, and is
expressed early in their development. Cross-linking CD7 positively
modulates T cell and NK cell activity as measured by calcium fluxes,
expression of adhesion molecules, cytokine secretion and proliferation. CD7
associates directly with phosphoinositol 3'-kinase, and CD7 ligation
induces production of D-3 phosphoinositides and tyrosine phosphorylation.
Severe combined immunodeficiency has been associated with a lack of
lymphocyte surface CD7. The CD7 ligand is unknown. The murine CD7 homolog
is encoded by a single gene on chromosome 11. In order to characterize the
role of CD7 in lymphocyte development and function we have eliminated the
CD7 gene by targeted disruption. CD7- deficient mice display normal
histology of thymus and spleen, normal lymphocyte populations in primary
and secondary lymphoid tissues, and normal serum Ig levels. Specific
antibody responses after immunization with T-dependent and T-independent
antigens are equivalent in wild-type and CD7 knockout mice. CD7-deficient
lymphocytes respond normally to T cell mitogenic and allogeneic stimuli,
and display normal NK cell cytotoxicity.
相似文献
28.
29.
The recirculation of lymphocytes and cell-mediated immunity show profound alterations in alcoholic liver disease. The use of cianidanol corrects a lot of these disturbances, in that: a) it can modify the receptor avidity of hepatocytes, b) it reduces the cell-mediated immune reactivity against liver specific protein antigen, diminishing the auto-immune reactions in alcoholic liver disease, c) it has no effect upon the conjugation process between the hepatocytes as target cells and cytotoxic effector cells, d) it decreases, however, the number of hepatocytes damaged after the conjugation process, and e) as a potent free-radical scavenger, it inhibits the cytotoxic effect of natural killer cells and monocytes, and in the same manner prevents the alteration of the hepatocyte membrane. 相似文献
30.
A new method of detecting eye movements (EMs) during sleep is described. The method consists of an electromechanical measurement using micro-miniaturized silver cup electrodes. These electrodes, when placed on the eyelid, produce electro-oculographic (EOG) recordings similar to the usual electrical method. The eyelid method offers the advantage of a relatively “clean” recording showing only EMs and movement artifact, with no intermingling of EEG and EOG. Furthermore, the method is at least one and one half times as sensitive as the usual EOG technique. In addition to these two special advantages, it also offers the features of conventional methods, convenience of DC coupling, independence from signal converters, ease of analyzing EM directionality, and durability despite the small size of the electrodes. Fabrication of the electrodes, recording configurations, and simultaneous comparisons to both the usual EOG technique and to a strain gauge method are described. 相似文献