全文获取类型
收费全文 | 3327篇 |
免费 | 182篇 |
国内免费 | 20篇 |
专业分类
耳鼻咽喉 | 15篇 |
儿科学 | 48篇 |
妇产科学 | 33篇 |
基础医学 | 455篇 |
口腔科学 | 73篇 |
临床医学 | 304篇 |
内科学 | 606篇 |
皮肤病学 | 41篇 |
神经病学 | 205篇 |
特种医学 | 505篇 |
外科学 | 717篇 |
综合类 | 11篇 |
预防医学 | 109篇 |
眼科学 | 43篇 |
药学 | 130篇 |
中国医学 | 3篇 |
肿瘤学 | 231篇 |
出版年
2024年 | 9篇 |
2023年 | 64篇 |
2022年 | 106篇 |
2021年 | 177篇 |
2020年 | 82篇 |
2019年 | 117篇 |
2018年 | 145篇 |
2017年 | 104篇 |
2016年 | 128篇 |
2015年 | 120篇 |
2014年 | 148篇 |
2013年 | 183篇 |
2012年 | 289篇 |
2011年 | 265篇 |
2010年 | 149篇 |
2009年 | 125篇 |
2008年 | 182篇 |
2007年 | 197篇 |
2006年 | 160篇 |
2005年 | 121篇 |
2004年 | 94篇 |
2003年 | 101篇 |
2002年 | 106篇 |
2001年 | 30篇 |
2000年 | 27篇 |
1999年 | 18篇 |
1998年 | 18篇 |
1997年 | 14篇 |
1996年 | 19篇 |
1995年 | 8篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 16篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1974年 | 4篇 |
1971年 | 4篇 |
1931年 | 5篇 |
1928年 | 6篇 |
1927年 | 4篇 |
1923年 | 4篇 |
1893年 | 5篇 |
排序方式: 共有3529条查询结果,搜索用时 375 毫秒
11.
12.
Fat mass is an important determinant of whole body bone density in premenopausal women but not in men. 总被引:18,自引:0,他引:18
I R Reid L D Plank M C Evans 《The Journal of clinical endocrinology and metabolism》1992,75(3):779-782
We recently reported that total body fat mass is the principal determinant of bone density in normal postmenopausal women. We have now reexamined the relationships among these variables and lean mass in 68 healthy premenopausal women and 51 men. Areal bone density (BMD), fat mass, and lean mass were measured in total body scans by dual-energy, x-ray absorptiometry. In women, BMD was correlated with weight (r = 0.69), fat mass (r = 0.60), and lean mass (r = 0.55). In men, the respective correlations were 0.56, 0.26 (NS), and 0.51. Multiple regression analysis confirmed a codependence of female BMD on fat and lean masses, whereas male BMD was related only to lean mass. Because BMD is an areal not volumetric density, it is dependent on body size. The analysis was therefore repeated using BMD/height as an index of "true" density. Correlations with fat mass were little changed but those with lean mass were reduced (women) or eliminated (men). By multiple regression, female BMD/height was related to fat mass alone, and in men there was a borderline effect of fat (P = 0.05) but none of lean mass. As a second method to exclude a scale artifact, fat mass was expressed as percent body weight. It was related to BMD (r = 0.48) only in women. It is concluded that bone density is closely related to fat mass in premenopausal women, but less so in men. In both sexes, apparent relationships between BMD and lean mass are artifacts attributable to the use of areal density (which is dependent on body size) as a surrogate for volumetric density. The mechanism of this fat-bone density relationship is an important question to be addressed in bone biology. 相似文献
13.
L. Maximilian Buja Victor J. Ferrans Barry J. Maron 《The American journal of pathology》1974,74(3):613-648
Junctional structures formed by two parts of the plasma membrane of the same cardiac muscle cell were observed in ventricular myocardium of: a) patients with neoplasms, aortic valvular disease or idiopathic hypertrophic subaortic stenosis and b) dogs subjected to prolonged normothermic anoxic cardiac arrest. Most of these structures had features of desmosomes; other, more complex structures had components with features of desmosomes, fasciae adherentes and nexuses, and, therefore, resembled intercalated discs. These intracytoplasmic junctions were localized to: a) the peripheral cytoplasm at the sides or ends of cells, b) narrow invaginations of plasma membranes, c) narrow zones of deep, broad plasmalemmal invaginations and d) narrow branches of T tubules. In patients with idiopathic hypertrophic subaortic stenosis or aortic valvular disease and in the dogs subjected to anoxic cardiac arrest, intracytoplasmic junctions were observed in hypertrophied or degenerated muscle cells which were located in areas of fibrosis and which showed loss of contact with adjacent cells. In patients with neoplasms, intracyto-plasmic junctions were found in degenerated cells which were located in areas of interstitial edema and which also showed loss of contact with adjacent cells. Our observations suggest that remodeling of cell surfaces following loss of intercellular contact is the most likely mechanism of formation of intracytoplasmic junctions. 相似文献
14.
15.
The Spleen in Type I Hyperlipoproteinemia: Histochemical, Biochemical, Microfluorometric and Electron Microscopic Observations
下载免费PDF全文
![点击此处可从《The American journal of pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Victor J. Ferrans L. Maximilian Buja William C. Roberts Donald S. Fredrickson 《The American journal of pathology》1971,64(1):67-96
Histochemical, biochemical, microfluorometric and electron microscopic studies were made of the spleen of a patient with type I hyperlipoproteinemia. Foam cells were observed that contained a material identified as ceroid on the basis of its autofluorescence, acid-fastness, sudanophilia, PAS-positivity and insolubility in organic solvents. Electron microscopy showed that the ceroid was organized in the form of granules with concentric lamellae of irregular periodicity. The process of formation of these granules is described in detail. The ceroid was considered to represent nondigestible end products of the metabolism of chylomicrons taken up by macrophages in splenic sinusoids. 相似文献
16.
17.
Identification and characterization of a new variant of Shiga toxin 1 in Escherichia coli ONT:H19 of bovine origin
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bürk C Dietrich R Açar G Moravek M Bülte M Märtlbauer E 《Journal of clinical microbiology》2003,41(5):2106-2112
A new variant of Shiga toxin 1 (Stx1), designated Stx1d, which deviates considerably more than any other known variant from Stx1 encoded by phage 933J, was identified in an Escherichia coli strain, ONT:H19, isolated from bovine feces. The complete stx(1) gene of this strain was amplified and sequenced. Nucleotide sequence homology with stx(1) from phage 933J was only 91%, resulting in the substitution of 20 amino acids in the A subunit and 7 amino acids in the B subunit of the protein. Cell culture supernatant of this strain, which was negative for stx(2) by PCR testing, was cytotoxic to Vero cells and gave positive results in two commercial enzyme-linked immunosorbent assays for Stx. PCR primers were constructed for the specific detection of the new variant. The findings of this study suggest that Stx1 is not as conserved as thought before and that there might be more variants which cannot be detected by commonly used PCR methods. 相似文献
18.
Uirich J. Knappe Dieter K. Lüdecke Maximilian J. A. Puchner Wolfgang Saeger Hans-D. Herrmann 《Endocrine pathology》1991,2(4):200-209
Tissue from 23 pituitary adenomas causing Cushing’s disease was implanted subcutaneously into 159 NuNu/NMRi mice, resected
after 21 or 35 days, and evaluated histologically and immunohistochemically. After 21 days, 74.3% of the grafts survived,
59% having less than 30% necrotic adenoma cells. After 35 days, 45% of the adenoma fragments survived, 37% having less than
30% necrotic adenoma cells. The preservation of the grafts was essentially dependent on the grade of vascularization accomplished
by migration of the host’s capillaries. As assessed by adrenal weight and histologically, biological activity of the transplants
could not be detected. Histologically, the grafts maintained the features of their primary tumors, and adrenocorticotropic
hormone (ACTH) could be visualized immunohistologically.Seventeen mice with subsequently proved preserved adenoma tissue received
an intravenous injection of 12.5 μCi125l-corticotropin-releasing hormone (CRH) and light microscopy-autoradiography was performed. Specific labeling, as verified
by positive and negative controls, was exhibited by 1 1 of 15 transplants originating from 3 highly differentiated ACTH cell
adenomas. Four did not label clearly positive. Two grafts of an undifferentiated mucoid cell pituitary adenoma did not show
any labeling.The nude mouse model is a useful tool for the study of ACTH-producing pituitary adenomas in vivo. Highly differentiated
ACTH cell adenomas can be labeled with radioactive CRH in vivo. 相似文献
19.
20.
Salivary duct carcinoma (SDC) is highly malignant salivary gland tumour with aggressive clinical behaviour, characterised by its histological resemblance to invasive ductal carcinoma of the breast. Amplification of gene HER-2/neu and overexpression of its gene product have been shown to have both prognostic and treatment implications in breast cancer. The reports concerning the expression of c-erbB2/HER-2/neu in salivary gland tumours are few and controversial. Thus, eleven cases of SDC were evaluated for HER-2/neu status using immunohistochemistry (IHC) and fluorescent in situ hybridization (FISH). To the best of our knowledge, this is the first molecular genetic analysis of SDCs using FISH. HER-2/neu overexpression, identified as strong membrane staining, was observed in all but one case of SDC in majority of neoplastic cells while only four tumours, of nine cases analysed, revealed HER-2/neu gene amplification by means of FISH analysis. SDCs were associated with poor clinical outcome, 6 patients (55%) died of disseminated carcinoma within 4 to 44 months after therapy. There was no difference in outcome of patients with IHC positive-nonamplified and IHC positive-amplified tumours. 相似文献