全文获取类型
收费全文 | 84371篇 |
免费 | 8239篇 |
国内免费 | 1766篇 |
专业分类
耳鼻咽喉 | 652篇 |
儿科学 | 1271篇 |
妇产科学 | 656篇 |
基础医学 | 5168篇 |
口腔科学 | 1271篇 |
临床医学 | 16687篇 |
内科学 | 9609篇 |
皮肤病学 | 584篇 |
神经病学 | 9967篇 |
特种医学 | 23212篇 |
外国民族医学 | 19篇 |
外科学 | 6324篇 |
综合类 | 8536篇 |
现状与发展 | 1篇 |
预防医学 | 2140篇 |
眼科学 | 1399篇 |
药学 | 2421篇 |
78篇 | |
中国医学 | 551篇 |
肿瘤学 | 3830篇 |
出版年
2024年 | 327篇 |
2023年 | 1575篇 |
2022年 | 2996篇 |
2021年 | 3941篇 |
2020年 | 3698篇 |
2019年 | 3386篇 |
2018年 | 3269篇 |
2017年 | 3582篇 |
2016年 | 3789篇 |
2015年 | 3684篇 |
2014年 | 6140篇 |
2013年 | 5379篇 |
2012年 | 5026篇 |
2011年 | 5437篇 |
2010年 | 4474篇 |
2009年 | 4615篇 |
2008年 | 4534篇 |
2007年 | 4285篇 |
2006年 | 3771篇 |
2005年 | 3272篇 |
2004年 | 2770篇 |
2003年 | 2139篇 |
2002年 | 1726篇 |
2001年 | 1676篇 |
2000年 | 1376篇 |
1999年 | 1057篇 |
1998年 | 1071篇 |
1997年 | 995篇 |
1996年 | 817篇 |
1995年 | 732篇 |
1994年 | 576篇 |
1993年 | 484篇 |
1992年 | 387篇 |
1991年 | 282篇 |
1990年 | 231篇 |
1989年 | 166篇 |
1988年 | 159篇 |
1987年 | 136篇 |
1986年 | 96篇 |
1985年 | 73篇 |
1984年 | 52篇 |
1983年 | 36篇 |
1982年 | 30篇 |
1981年 | 25篇 |
1980年 | 30篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1977年 | 9篇 |
1976年 | 14篇 |
1974年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Juhani Trmnen Osmo Tervonen Antero Koivula Juhani Junila Ilkka Suramo 《Journal of magnetic resonance imaging : JMRI》1996,6(5):805-811
The purpose of this study was to explore systematically the effect of the imaging parameters changeable by the user in spin-echo (SE) imaging sequences to minimize image distortion when imaging joint prostheses. A titanium alloy hip joint prosthesis was studied at 1.0 T. The SE imaging parameters were bandwidth/pixel (BW/p), TE, strength of encoding gradients (matrix size), echo train length (ETL), and direction of phase and frequency encoding. The effect of ETL in rapid acquisition relaxation enhanced (RARE) sequences was also evaluated with a turbo-SE sequence using a different ETL with the same TR and an effective TE. It is concluded that an optimized image quality can be achieved in SE imaging by using a high bandwidth/pixel value (at least 130 Hz/pixel), a high resolution matrix (256–512), sequences with multiple refocusing, and a frequency-encoding axis parallel to the long axis of the prosthesis. The degree of distortion is reduced with this optimized technique. 相似文献
62.
A case of MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) which presented as migraine
complicated by stroke is reported. Strokes associated with migraine have often been reported, but the mechanism remains unclear
and may include a variety of pathologies. MELAS also presents with migrainous headache, vomiting, and stroke-like symptoms.
Magnetic resonance imaging demonstrates characteristic findings. MELAS should be considered in the differential diagnosis
of infarct-like lesions with migrainous headaches in young adults, especially if the symptoms fluctuate and are accompanied
by a homonymous hemianopia.
Received: 23 September 1996 Accepted: 19 February 1997 相似文献
63.
We correlated MRI features with histopathological findings in an HIV-positive patient with vacuolar myelopathy. On MRI symmetrical
nonenhancing high-signal areas in the posterior columns on T2-weighted images result from extensive vacuolation visible on
histological sections.
Received: 18 November 1997 Accepted: 23 March 1997 相似文献
64.
A. Rimmelin P. L. Clouet S. Salatino P. Kehrli D. Maitrot M. Stephan J. L. Dietemann 《Neuroradiology》1997,39(3):203-206
Extradural arachnoid cysts are uncommon expanding lesions in the spinal canal which may communicate with the subarachnoid
space. Usually in the lower thoracic spine, they may cause symptoms by compressing the spinal cord or nerve roots. We report
cases of thoracic and lumbar arachnoid cysts studied by cystography, myelography, CT and MRI. These techniques showed extradural
cystic lesions containing cerebrospinal fluid, with variable communication with the subarachnoid space, causing anterior displacement
and flattening of the spinal cord.
Received: 3 November 1995 Accepted: 16 April 1996 相似文献
65.
Neurosarcoma is a rare tumour originating from the sheath of peripheral nerves. Facial lesions have been reported in about
20 patients. We describe the MRI appearances of neurosarcoma with histological correlation in three patients. The lesions
lay in the submandibular region, the left parapharyngeal space and the right orbit. MRI showed a well-defined mass with mixed
components. The lesions were moderately heterogeneous on T1-weighted images in two cases and on T2-weighted images in all
cases. Gadolinium enhancement occurred in all cases to variable degrees. In two cases, small high signal foci were seen on
T2-weighted sequences. MRI appearances of neurosarcoma are not specific.
Received: 3 September 1996 Accepted: 26 November 1996 相似文献
66.
H. Bonél A. Frick H. Sittek A. Heuck M. Steinborn R. G. H. Baumeister M. Reiser 《Der Radiologe》1997,37(10):785-793
Summary
Purpose of this study was to evaluate the diagnostic value of a low field dedicated MRI system in hand and wrist imaging.
All 308 exams of the hand and wrist, that were performed on a low-field dedicated MRI system (Artoscan, Esaote Biomedica,
Italy) in our institution in 1996, and high-field MRI exams performed in addition as part of the diagnostic work-up, were
evaluated and correlated to final operative (n = 64) and histologic (n = 12) reports. 90 % of all low-field MRI scans stated a diagnosis according to clinical suspicion. In 62 % the clinical question
was answered, and in 26 % additional pathologies were identified. An MR-diagnosis completely different from the clinical suspicion
was stated in 2 %. High field exams contributed additional information in 6 of 36 patients. In 3 patients a tumor was not
shown completely in the limited field-of-view of the dedicated low-field MRI-system. Frequency-selective fat-suppression pulse
sequences and a better spatial resolution were the reasons for the additional information obtained in the other three patients.
Low-field dedicated MR-imaging is a valuable method in the extensive work-up of the hand and wrist. Osseous, ligamentous and
tendinous pathologies are well depicted. Large or infiltrative tumors should be referred to a high-field system.
相似文献
67.
Periannan Kuppusamy Penghai Wang Michael Chzhan Jay L. Zweier 《Magnetic resonance in medicine》1997,37(4):479-483
The application of electron paramagnetic resonance imaging (EPRI) to obtain information from biological samples has been limited by the lack of ideal single line radical labels. The commonly used nitroxides exhibit multiple lines causing either hyperfine-based limitations in the maximum obtainable image resolution or hyperfine-based artifacts in the reconstructed image. The use of a novel single-line triarylmethyl paramagnetic label that enables marked enhancement in image quality and resolution is reported. This label exhibits a single line EPR spectrum that is sharp (linewidth ~60 mG in the absence of oxygen) and relatively stable in tissues. The potential of this label in enabling high resolution EPR imaging of biological samples was demonstrated in a series of phantoms and isolated biological organs such as the rat kidney. The images demonstrate that resolutions better than 100 μm could be obtained at L-band on samples of up to 20 mm in size. 相似文献
68.
Diagnosis and treatment of thoracic outlet syndrome 总被引:2,自引:0,他引:2
Masataka Abe Tadashi Shimamura Jun Nishida Katsuaki Ichinohe 《Journal of orthopaedic science》1997,2(2):119-127
Patients who develop symptoms of thoracic outlet syndrome (TOS) have a predisposing anatomic abnormality. In most patients
with TOS, the symptoms are caused by entrapment of the brachial plexus and they do not arise from compression of the subclavian
artery, as was previously thought. The tests advocated for diagnosing this common syndrome (i.e., evaluating the positional
compression of the artery when the arms are raised, the neck is turned, or the shoulders are braced) cannot accurately diagnose
this syndrome. There are two reasons for this. The symptoms of TOS are not related to the compression of the artery in the
outlet in 98% of patients, and 75% of normal individuals without symptoms show diminished radial pulse on various provocation
tests. We employed four timed provocation tests (minute tests) to diagnose TOS: the timed Morley test, timed Wright test,
timed Eden test, and elevated arm stress exercise, all of which are very sensitive. In normal individuals without symptoms,
20% experience transitional symptoms such as slight pain and tiredness, on these tests indicating a subclinical state. TOS
is treated by keeping the thoracic outlet wide, this being done either conservatively or surgically. In 1993 and 1994, we
conservatively treated 418 of 422 patients with TOS by means of active exercise, a brace, and by block therapy. These measures
did not reduce the symptoms in 23 of these patients, so surgical treatment was indicated. In the remaining 4 of the 422 patients,
conservative treatment was not indicated and surgery was performed directly. All the patients showed significant clinical
improvement of varying degree.
Presented at the 69th Annual Meeting of the Japanese Orthopaedic Association, Tokyo, April 12, 1996 相似文献
69.
70.
M. Filippi A. Campi V. Martinelli C. Pereira G. Scotti G. Comi 《Acta neurologica Scandinavica》1995,92(2):178-182
Transitional progressive multiple sclerosis (MS) is quite an unusual form of presentation and course of the disease. A case with this progressive form is presented and brain MRI and MTI findings are discussed in relation to the possible insight they may provide for understanding the mechanisms that determine progressive disability in MS. 相似文献