全文获取类型
收费全文 | 1091篇 |
免费 | 89篇 |
国内免费 | 7篇 |
专业分类
耳鼻咽喉 | 6篇 |
儿科学 | 43篇 |
妇产科学 | 19篇 |
基础医学 | 100篇 |
口腔科学 | 65篇 |
临床医学 | 110篇 |
内科学 | 156篇 |
皮肤病学 | 10篇 |
神经病学 | 177篇 |
特种医学 | 190篇 |
外科学 | 56篇 |
综合类 | 74篇 |
预防医学 | 59篇 |
眼科学 | 4篇 |
药学 | 56篇 |
中国医学 | 24篇 |
肿瘤学 | 38篇 |
出版年
2022年 | 10篇 |
2021年 | 4篇 |
2020年 | 9篇 |
2019年 | 14篇 |
2018年 | 25篇 |
2017年 | 19篇 |
2016年 | 17篇 |
2015年 | 18篇 |
2014年 | 27篇 |
2013年 | 56篇 |
2012年 | 51篇 |
2011年 | 39篇 |
2010年 | 46篇 |
2009年 | 52篇 |
2008年 | 51篇 |
2007年 | 59篇 |
2006年 | 31篇 |
2005年 | 20篇 |
2004年 | 27篇 |
2003年 | 20篇 |
2002年 | 17篇 |
2001年 | 28篇 |
2000年 | 19篇 |
1999年 | 25篇 |
1998年 | 61篇 |
1997年 | 55篇 |
1996年 | 40篇 |
1995年 | 30篇 |
1994年 | 27篇 |
1993年 | 27篇 |
1992年 | 9篇 |
1991年 | 15篇 |
1990年 | 12篇 |
1989年 | 20篇 |
1988年 | 29篇 |
1987年 | 21篇 |
1986年 | 16篇 |
1985年 | 28篇 |
1984年 | 9篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 3篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1976年 | 12篇 |
1975年 | 9篇 |
1974年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有1187条查询结果,搜索用时 46 毫秒
1.
Intracranial circulation: pulse-sequence considerations in three- dimensional (volume) MR angiography 总被引:2,自引:0,他引:2
The technique and feasibility of magnetic resonance (MR) angiography of intracranial vessels were studied in 35 healthy volunteers. Variations in image orientation, repetition time (TR), and flip angle were evaluated to determine their effects on flow-related enhancement. Gradient modifications--including echo time (TE), motion compensation, bandwidth, and field of view--were also studied in an effort to reduce motion-induced phase shifts. Results indicated that a FISP (fast imaging with steady precession) sequence with a TR of 50 msec, TE of 15 msec, velocity compensation in the read and section-select directions, acceleration compensation in the read direction, anisotropic volume, and a 1.25-mm partition thickness produced three-dimensional angiographic MR images that were accurate and reproducible in the depiction of the major intracranial vessels. Difficulties with field of view, persistent signal void secondary to higher-order motion, and spatial resolution remain major problems requiring additional study. 相似文献
2.
Maxillary sinusitis in adults: an evaluation of placebo-controlled double-blind trials 总被引:1,自引:0,他引:1
BACKGROUND: In general practice, acute sinusitis is frequently diagnosed
and treated with antibiotics. OBJECTIVE: This study aimed to determine the
evidence for the effectiveness of antibiotic treatment in acute maxillary
sinusitis in adults by assessing the methodological quality of
placebo-controlled double-blind randomized trials. METHOD: An evaluation by
four raters through a 35-item scoring-scale for internal and external
validity of all placebo-controlled double-blind randomized trials on acute
sinusitis found between January 1966 and July 1996. RESULTS: Eighty-five
trials were excluded because they were not placebo-controlled,
double-blind, randomized, or were carried out in patients with chronic
sinusitis or in children. The three remaining trials were performed in
different populations (one in general practice) between 1973 and 1978. Only
one study claimed superiority of antibiotic treatment. Different inclusion
criteria and major outcome measures were used by the authors. The
reliability of major outcome events was reported poorly or not at all and
in two studies outcome measures were clinically inappropriate. The studies
scored 30-62% of the maximum attainable score for internal validity and
10-20% for external validity. CONCLUSION: The effectiveness of antibiotic
treatment in acute maxillary sinusitis in a general practice population is
not based sufficiently on evidence.
相似文献
3.
4.
H Angus-Leppan GA Lambert J Michalicek 《Cephalalgia : an international journal of headache》1997,17(6):625-630
Co-existence of facial and occipital pain may occur in occipital neuralgia, migraine and cluster headache; suggesting convergence of trigeminal and cervical afferents. Such convergence has been shown in humans and other animals, but the site and extent of this are uncertain. In anaesthetized adult cats, the superior sagittal sinus and occipital nerve were stimulated electrically, and extracellular recordings made in the dorsolateral area of the upper cervical cord using glass-coated tungsten electrodes. Of 49 units in 10 cats, 33 (67%) had input from the superior sagittal sinus and the occipital nerve. Thirteen (27%) had superior sagittal sinus input and 3 (6%) had occipital nerve input. Convergent receptive fields were identified mechanically in 7 units. These experiments in cats show convergent input from occipital nerve and superior sagittal sinus on dorsolateral area units in two-thirds of cases studied. This experimental site of trigeminocervical convergence may relate to referral of pain in occipital neuralgia and other headaches. 相似文献
5.
In patients with PG-dependent renal function, NSAID administration
constantly reduces GFR and RBF in a dose-dependent fashion. In this
situation, the risk of overt acute renal failure is high and should be
taken into proper account. In contrast, the incidence of NSAID-related
renal structural alterations appears to be very low, yet the absolute
number of patients may be significant considering the wide use of such
drugs. Concerning the antiproteinuric effect of NSAIDs, the unfavourable
ratio risk/benefit does not seem to support their indication in proteinuric
nephropathies. The development of PGHS-2 selective inhibitors is promising,
and may open new therapeutical strategies in the treatment of the
progression of renal disease.
相似文献
6.
7.
8.
9.
10.
Aspergillus fumigatus is an important fungal pathogen that causes invasive pulmonary disease in immunocompromised hosts. Respiratory exposure to A. fumigatus spores also causes allergic bronchopulmonary aspergillosis, a Th2 CD4+-T-cell-mediated disease that accompanies asthma. The microbial factors that influence the differentiation of A. fumigatus-specific CD4+ T lymphocytes into Th1 versus Th2 cells remain incompletely defined. We therefore examined CD4+-T-cell responses of immunologically intact mice to intratracheal challenge with live or heat-inactivated A. fumigatus spores. Live but not heat-inactivated fungal spores resulted in recruitment of gamma interferon (IFN-gamma)-producing, fungus-specific CD4+ T cells to lung airways, achieving A. fumigatus-specific frequencies exceeding 5% of total CD4+ T cells. While heat-inactivated spores did not induce detectable levels of IFN-gamma-producing, A. fumigatus-specific CD4+ T cells in the airways, they did prime CD4+ T-cell responses in draining lymph nodes that produced greater amounts of interleukin 4 (IL-4) and IL-13 than T cells responding to live conidia. While immunization with live fungal spores induced antibody responses, we found a marked decrease in isotype-switched, A. fumigatus-specific antibodies in sera of mice following immunization with heat-inactivated spores. Our studies demonstrate that robust Th1 T-cell and humoral responses are restricted to challenge with fungal spores that have the potential to germinate and cause invasive infection. How the adaptive immune system distinguishes between metabolically active and inactive fungal spores remains an important question. 相似文献