全文获取类型
收费全文 | 1458篇 |
免费 | 96篇 |
国内免费 | 219篇 |
专业分类
耳鼻咽喉 | 13篇 |
儿科学 | 56篇 |
妇产科学 | 42篇 |
基础医学 | 158篇 |
口腔科学 | 48篇 |
临床医学 | 125篇 |
内科学 | 244篇 |
皮肤病学 | 42篇 |
神经病学 | 122篇 |
特种医学 | 285篇 |
外科学 | 335篇 |
综合类 | 58篇 |
预防医学 | 58篇 |
眼科学 | 8篇 |
药学 | 141篇 |
肿瘤学 | 38篇 |
出版年
2022年 | 8篇 |
2021年 | 45篇 |
2020年 | 13篇 |
2019年 | 12篇 |
2018年 | 23篇 |
2017年 | 11篇 |
2016年 | 17篇 |
2015年 | 21篇 |
2014年 | 25篇 |
2013年 | 30篇 |
2012年 | 28篇 |
2011年 | 28篇 |
2010年 | 36篇 |
2009年 | 42篇 |
2008年 | 27篇 |
2007年 | 60篇 |
2006年 | 46篇 |
2005年 | 59篇 |
2004年 | 49篇 |
2003年 | 44篇 |
2002年 | 65篇 |
2001年 | 95篇 |
2000年 | 66篇 |
1999年 | 73篇 |
1998年 | 74篇 |
1997年 | 68篇 |
1996年 | 64篇 |
1995年 | 61篇 |
1994年 | 40篇 |
1993年 | 46篇 |
1992年 | 20篇 |
1991年 | 28篇 |
1990年 | 34篇 |
1989年 | 54篇 |
1988年 | 42篇 |
1987年 | 41篇 |
1986年 | 26篇 |
1985年 | 31篇 |
1984年 | 19篇 |
1983年 | 13篇 |
1982年 | 18篇 |
1981年 | 20篇 |
1980年 | 19篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1977年 | 19篇 |
1976年 | 13篇 |
1975年 | 13篇 |
1971年 | 6篇 |
1970年 | 11篇 |
排序方式: 共有1773条查询结果,搜索用时 31 毫秒
21.
Ralf Henkel Susan Cooper Khalied Kaskar Wolf-Bernhard Schill Ursula-F. Habenicht Daniel R. Franken 《Journal of assisted reproduction and genetics》1995,12(9):644-649
Purpose
A total of 86 fresh and salt-stored immature human oocytes derived from postmortem ovarian tissue were used for this study.Methods
Oocytes were randomly incubated either in synthetic human tubal fluid medium (untreated zonae) or in a chemically defined medium (treated zonae).Results
Sperm binding experiments using hemizona assay conditions exhibited a 10-fold increased binding of sperm to treated compared to untreated oocytes (272.7±43 versus 24.3±15 sperm bound, respectively; P<0.0001). pH recordings during incubation showed elevated pH levels of 8.1 compared to pH 7.2 among treated and untreated zonae, respectively. Ultrastructural examination showed a spongy appearance of the surface of treated zonae, whereas untreated zonae appeared compact with smooth surface.Conclusions
The marked increase in sperm binding among treated zonae, together with the ultrastructural findings, suggest that the altered zona surface enhances sperm binding. The physiological maturational process of the zona pellucida might be manipulated in vitro, thus increasing sperm binding to the zona.Presented at the IXth World Congress on In Vitro Fertilization and Alternate Assisted Reproduction, April 3–7, 1995. Vienna, Austria. 相似文献
22.
Low-artifact intravascular devices: MR imaging evaluation 总被引:2,自引:0,他引:2
Teitelbaum GP; Ortega HV; Vinitski S; Stern H; Tsuruda JS; Mitchell DG; Rifkin MD; Bradley WG Jr 《Radiology》1988,168(3):713-719
Flow-phantom magnetic resonance (MR) imaging, with use of both spin-echo (SE) and gradient-echo (GRE) techniques at 1.5 T, was performed on the percutaneous Greenfield (beta-III titanium alloy [TMA wire]), Amplatz (MP32-N alloy), and Simon nitinol filters and TMA wire facsimiles of the bird's nest, Gunther, new retrievable, and Amplatz vena caval filters. SE imaging allowed detection of thrombi as small as 5 X 5 mm trapped within the percutaneous Greenfield, Simon nitinol, and TMA-wire facsimile filters; with the MP32-N Amplatz filter, a larger volume of thrombus (10 X 20-mm clots) was necessary for clot detection. GRE imaging allowed detection of intraluminal tilting of the percutaneous Greenfield and facsimile Amplatz (TMA-wire) filters. GRE imaging was useful for demonstrating postfilter turbulence due to clots, which was greatest for the Amplatz filter. Imaging of facsimile vascular devices made of tantalum or TMA wire did not cause the severe "black-hole" MR artifacts typical of the stainless-steel devices. SE and GRE imaging were very useful for determining caval patency in two patients with previously placed Mobin-Uddin filters. Noninvasive MR evaluation of blood vessels in the presence of a variety of low-artifact intravascular devices appears feasible. 相似文献
23.
24.
Contribution of cloned virulence factors from uropathogenic Escherichia coli strains to nephropathogenicity in an experimental rat pyelonephritis model. 总被引:4,自引:12,他引:4
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Escherichia coli 536 (O6:K15:H31), which was isolated from a case of urinary tract infection, determines high nephropathogenicity in a rat pyelonephritis system as measured by renal bacterial counts 7 days after infection. The loss of S fimbrial adhesin formation (Sfa-) (mannose-resistant hemagglutination [Mrh-] and fimbria production [Fim-]), serum resistance (Sre-), and hemolysin production (Hly-) in the mutant 536-21 led to a dramatic reduction of bacterial counts from almost 10(5) to only 40 cells per g of kidney. The reintroduction of the cloned S fimbrial adhesin determinant (sfa) increases the virulence of the avirulent mutant strain by a factor of 20; almost the same effect was observed after restoration of serum resistance by integration of an sfa+ recombinant cosmid into the chromosome. Additional reintroduction of the Hly+ phenotype by transformation of two hly determinants increased the virulence of the strains. Hemolysin production determined increased renal elimination of leukocytes and erythrocytes. Thus all three determinants investigated, S fimbriae, serum resistance, and hemolysin, contribute to the multifactorial phenomenon of E. coli nephropathogenicity. 相似文献
25.
26.
27.
28.
Neurofibromatosis 2 (NF2) is an inherited cancer syndrome resulting from
mutations in the NF2 tumor suppressor gene. Analysis of NF2 mutations has
revealed some general genotype-phenotype correlations. Severe disease has
been associated with mutations that produce a premature termination while
more mild disease has been associated with missense mutations. Here, we
provide experimental proof for these genotype-phenotype correlations by
demonstrating that nonsense mutations fail to produce stable merlin protein
while missense mutations result in the generation of merlin proteins
defective in negative growth regulation. This inability to suppress cell
growth may result from defects in the function of merlin at several levels,
including failure to form an intramolecular complex. Based on these
findings, we propose a model for merlin growth suppression that provides a
framework for analyzing NF2 patient mutations and merlin function.
相似文献
29.
JS Pooni Dr DWL Hukins PF Harris RC Hilton KE Davies 《Surgical and radiologic anatomy : SRA》1986,8(3):175-182
Posterior and anterior heights, cross-sectional area and shape were measured for all the intervertebral discs in four spines from elderly human cadavers. Disc height was a minimum at the T4-5 level; thoracic discs were less wedge-shaped than those in the cervical and lumbar regions. Cross-sectional area increased from the cranial to caudal extremity; at the L5-S1 level the nucleus pulposus occupied a high proportion of this area. Cervical discs tended to have an elliptical cross-sectional shape, thoracic discs were more circular and lumbar discs tended to have an elliptical cross-section which was flattened or re-entrant posteriorly. This shape distribution was quantified by defining a shape index which had a maximum value of 1 for a circular cross-section. Orientations of the reinforcing fibres in the outer lamellae of the anterior annulus fibrosus were measured from 27 discs by X-ray diffraction. For these measurements, C3-4, T7-8 and L2-3 were chosen as representative of cervical, thoracic and lumbar discs. The fibre tilt, with respect to the axis of the spine, was significantly less in the cervical discs (at 65 degrees) than in the thoracic and lumbar discs (about 70 degrees). These findings are interpreted in relation to differing functional requirements and possible mechanisms of failure in the cervical, thoracic and lumbar regions of the spine in the light of current knowledge on the biomechanics of the intervertebral disc. 相似文献
30.