全文获取类型
收费全文 | 556篇 |
免费 | 21篇 |
国内免费 | 96篇 |
学科分类
医药卫生 | 673篇 |
出版年
2023年 | 3篇 |
2021年 | 6篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 8篇 |
2013年 | 19篇 |
2012年 | 7篇 |
2011年 | 7篇 |
2010年 | 27篇 |
2009年 | 24篇 |
2008年 | 12篇 |
2007年 | 58篇 |
2006年 | 15篇 |
2005年 | 25篇 |
2004年 | 5篇 |
2003年 | 8篇 |
2002年 | 10篇 |
2001年 | 17篇 |
2000年 | 8篇 |
1999年 | 12篇 |
1998年 | 42篇 |
1997年 | 38篇 |
1996年 | 29篇 |
1995年 | 29篇 |
1994年 | 27篇 |
1993年 | 38篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 12篇 |
1989年 | 25篇 |
1988年 | 24篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 8篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有673条查询结果,搜索用时 15 毫秒
1.
Digital radiography of subtle pulmonary abnormalities: an ROC study of the effect of pixel size on observer performance 总被引:3,自引:0,他引:3
Forty conventional radiographs with examples of mild interstitial infiltrates and subtle pneumothoraces and 40 normal studies of the chest were selected and digitized, with pixel sizes of 1.0, 0.5, 0.2, and 0.1 mm. Observer performance tests were carried out using receiver operating characteristic analysis. Conventional radiographs and digitized images were compared. The results indicate that, in such cases, diagnostic accuracy increases significantly as the pixel size is reduced, at least to the 0.1-mm level. We conclude that, for digital systems using screen-film or similar image receptors, use of a pixel size substantially larger than 0.1 mm may result in some loss of diagnostic accuracy. 相似文献
2.
Stroke is the leading cause of long term disability and the third leading cause of death in the US. Nearly $US40.9 billion (1997 values) are spent each year on direct and indirect stroke-related costs in the US alone. Length of hospital stay, hospital overheads and nursing-related and rehabilitation costs account for the majority of stroke-related expenditures. Intravenous recombinant tissue plasminogen activator (rt-PA) therapy for patients presenting within 3 hours from onset of ischaemic stroke was shown to improve outcome at 3 months by the National Institute of Neurological Disease and Stroke (NINDS) investigators using a dosage of 0.9 mg/kg. When the NINDS rt-PA Stroke Study results were examined using a Markov model, savings of $US4 to $US5 million (1996 values) per 1000 patients treated with rt-PA were projected. These savings were predicted to result from decreases in length of hospital stay, inpatient rehabilitation and nursing home costs, increases in the number of patients discharged directly to home and improvements in quality-adjusted life-years. Furthermore, a recent meta-analysis has documented that the institution of stroke units, consisting of multidisciplinary specialised stroke teams, also decreased length of hospital stay, death and dependency. Because only a minority of patients who have a stroke are currently eligible for thrombolysis, implementation of specialised and standardised stroke care may further enhance cost benefits and improve patient outcomes. 相似文献
3.
Y chromosome microdeletions, in azoospermic or near-azoospermic subjects, are located in the AZFc (DAZ) subregion 总被引:9,自引:2,他引:9
Submicroscopic deletions of the Y chromosome and polymorphisms of the
androgen receptor (AR) gene in the X chromosome have been observed in men
with defective spermatogenesis. To further define the subregions/genes in
the Y chromosome causing male infertility and its relationship to
polymorphisms of the AR polyglutamine tract, we screened the genomic DNA of
202 subfertile males and 101 healthy fertile controls of predominantly
Chinese ethnic origin. Y microdeletions were examined with 16
sequence-tagged site (STS) probes, including the RBM and DAZ genes,
spanning the AZFb and AZFc subregions of Yq11, and related to the size of
trinucleotide repeat encoding the AR polyglutamine tract. Y microdeletions
were detected and confirmed in three out of 44 (6.8%) of azoospermic and
three out of 86 (3.5%) severely oligozoospermic patients. No deletions were
detected in any of the patients with sperm counts of >0.5 x 10(6)/ml,
nor in any of the 101 fertile controls. All six affected patients had
almost contiguous Y microdeletions spanning the entire AZFc region
including the DAZ gene. The AZFb region, containing the RBM1 gene, was
intact in five of the six subjects. Y deletions were not found in those
with long AR polyglutamine tracts. Our study, the first in a Chinese
population, suggest a cause and effect relationship between Y
microdeletions in the AZFc region (possibly DAZ), and azoospermia or
near-azoospermia. Y microdeletions and long AR polyglutamine tracts appear
to be independent contributors to male infertility.
相似文献
4.
Catt SL; Sakkas D; Bizzaro D; Bianchi PG; Maxwell WM; Evans G 《Molecular human reproduction》1997,3(9):821-825
Controlling the sex of offspring by the separation of X and Y
chromosome-bearing spermatozoa using flow cytometry has been reported as a
clinical technique aiding prevention of X-linked diseases. Although this
technique has resulted in several hundred normal births in animals and at
least one human birth, there is still concern over its genetic safety due
to the involvement of two potentially mutagenic agents: UV light and the
fluorochrome dye, Hoechst 33342 (H33342). Human spermatozoa, particularly
those considered abnormal, may be more likely to suffer DNA damage
following exposure to mutagenic agents, compared with other mammalian
species. The stability of normal fresh and decondensed human spermatozoa
were examined after exposure to a range of levels of UV and H33342
staining, using an assay that detects endogenous nicks in the DNA of
spermatozoa. The stability of abnormal and normal, fresh and frozen-thawed
human spermatozoa was examined following UV laser, H33342 staining and flow
cytometry treatments utilizing the same assay. There was an increase in the
presence of endogenous nicks when spermatozoa were decondensed compared
with fresh spermatozoa. There was no increase in the incidence of nicks in
any group of spermatozoa after UV and fluorochrome exposure compared with
controls without exposure.
相似文献
5.
Winberg JO; Hammami-Hauasli N; Nilssen O; Anton-Lamprecht I; Naylor SL; Kerbacher K; Zimmermann M; Krajci P; Gedde-Dahl T Jr; Bruckner-Tuderman L 《Human molecular genetics》1997,6(7):1125-1135
Dystrophic epidermolysis bullosa (EBD) is a clinically heterogeneous skin
disorder, characterized by abnormal anchoring fibrils (AF) and loss of
dermal-epidermal adherence. EBD has been linked to the COL7A1 gene at
chromosome 3p21 which encodes collagen VII, the major component of the AF.
Here we investigated two unrelated EBD families with different clinical
phenotypes and novel combinations of recessive and dominant COL7A1
mutations. Both families shared the same recessive heterozygous 14 bp
deletion at the exon-intron 115 boundary of the COL7A1 gene. The deletion
caused in-frame skipping of exon 115 and the elimination of 29 amino acid
residues from the pro-alpha1(VII) polypeptide chain. As a result,
procollagen VII was not converted to collagen VII and the C-terminal NC-2
propeptide which is normally removed from the procollagen VII prior to
formation of the anchoring fibrils was retained in the skin. All affected
individuals also carried missense mutations in exon 73 of COL7A1 which lead
to different glycine- to-arginine substitutions in the triple-helical
domain of collagen VII. Combination of the deletion mutation with a G2009R
substitution resulted in a mild phenotype. In contrast, combination of the
deletion with a G2043R substitution led to a severe phenotype. The G2043R
substitution was a de novo mutation which alone caused a mild phenotype.
Thus, different combinations of dominant and recessive COL7A1 mutations can
modulate disease activity of EBD and alter the clinical presentation of the
patients.
相似文献
6.
7.
Wang WS; Hsieh RK; Chiou TJ; Liu JH; Fan FS; Yen CC; Tung SL; Chen PM 《Japanese journal of clinical oncology》1998,28(9):551-554
A 54-year-old man was treated with weekly 24-h infusion of high-dose
5-fluorouracil (2600 mg/m2) and leucovorin (100 mg/m2) for metastatic colon
cancer. At first, he tolerated the treatment well and no significant
toxicity was identified. After a total of eight courses of treatment, a
stable disease was observed, but mild shortness of breath was found on
occasion. The patient had no previous history of cardiac disease and the
heart performance assessed by left ventricular ejection fraction before
treatment was normal. Unfortunately, acute pulmonary edema with lethal
cardiogenic shock occurred during the ninth course of treatment, in spite
of intensive medical treatment. The chest X-ray showed extreme
cardiomegaly. Repeated assessment of his heart function by echocardiogram
and ventricular ejection fraction revealed a very poor cardiac performance.
Toxic cardiogenic shock during weekly 24-h infusion of high-dose
5-fluorouracil and leucovorin is extremely rare. To the best of our
knowledge, no case has been reported in the English literature. We report a
case and the relevant literature about the incidence, clinical picture and
possible pathophysiology on 5-fluorouracil-related cardioxicity is
reviewed.
相似文献
8.
9.
10.