全文获取类型
收费全文 | 1339篇 |
免费 | 91篇 |
国内免费 | 22篇 |
专业分类
耳鼻咽喉 | 5篇 |
儿科学 | 84篇 |
妇产科学 | 23篇 |
基础医学 | 165篇 |
口腔科学 | 42篇 |
临床医学 | 73篇 |
内科学 | 154篇 |
皮肤病学 | 75篇 |
神经病学 | 165篇 |
特种医学 | 289篇 |
外科学 | 166篇 |
综合类 | 47篇 |
预防医学 | 55篇 |
眼科学 | 6篇 |
药学 | 41篇 |
肿瘤学 | 62篇 |
出版年
2021年 | 9篇 |
2018年 | 10篇 |
2017年 | 14篇 |
2016年 | 22篇 |
2015年 | 22篇 |
2014年 | 30篇 |
2013年 | 29篇 |
2012年 | 26篇 |
2011年 | 42篇 |
2010年 | 31篇 |
2009年 | 37篇 |
2008年 | 40篇 |
2007年 | 45篇 |
2006年 | 36篇 |
2005年 | 44篇 |
2004年 | 39篇 |
2003年 | 32篇 |
2002年 | 39篇 |
2001年 | 32篇 |
2000年 | 28篇 |
1999年 | 25篇 |
1998年 | 48篇 |
1997年 | 49篇 |
1996年 | 43篇 |
1995年 | 37篇 |
1994年 | 25篇 |
1993年 | 32篇 |
1992年 | 31篇 |
1991年 | 26篇 |
1990年 | 13篇 |
1989年 | 32篇 |
1988年 | 35篇 |
1987年 | 50篇 |
1986年 | 30篇 |
1985年 | 24篇 |
1984年 | 10篇 |
1983年 | 18篇 |
1982年 | 16篇 |
1981年 | 21篇 |
1980年 | 21篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 11篇 |
1976年 | 23篇 |
1975年 | 12篇 |
1936年 | 10篇 |
1934年 | 12篇 |
1932年 | 8篇 |
1930年 | 15篇 |
1929年 | 8篇 |
排序方式: 共有1452条查询结果,搜索用时 15 毫秒
11.
In 260 asbestos-exposed individuals evaluated by means of computed tomography (CT), 43 unsuspected pulmonary masses were found in 27 individuals. The masses included fissural pleural plaques (n = 10), dense fibrotic bands (n = 3), round atelectasis (n = 11), carcinomas (n = 3), and other presumed benign masses (n = 16). The most helpful features in the diagnosis of rounded atelectasis with CT were (a) contiguity to areas of diffuse pleural thickening, (b) a lentiform or wedge-shaped outline, (c) evidence of volume loss in the adjacent lung, and (d) a characteristic "comet tail" of vessels and bronchi sweeping into the margins of the mass. Less advanced areas of focal atelectasis had fewer classic features. Intrafissural pleural plaques were readily identified with high-resolution CT. In asbestos-related masses, the demonstration of stability over time is necessary. Careful interpretation of CT and high-resolution CT features and close surveillance can obviate the need for biopsy in the majority of instances. 相似文献
12.
13.
Ghosh D; Stewart DR; Nayak NR; Lasley BL; Overstreet JW; Hendrickx AG; Sengupta J 《Human reproduction (Oxford, England)》1997,12(5):914-920
The present study was undertaken to assess the temporal association between
the profiles of serum concentrations of oestradiol-17beta, progesterone,
chorionic gonadotrophin (CG) and relaxin in pregnancies established
naturally, and after embryo transfer, as well as in failed pregnancies in
rhesus monkeys. In naturally mated cycles (group 1) a conception rate of
75% was obtained. In group 1, the mean day of CG detection in serum was
11.5 +/- 1.9 day post-ovulation, and for relaxin, 9.0 +/- 2.5 day
post-ovulation. In group 2, embryo transfer to synchronous, non-mated
surrogate recipients was performed; seven embryo transfer cycles yielded
three pregnancies which were allowed to continue to term and normal infants
were delivered. In embryo transfer cycles the mean day of CG detection was
14.8 +/- 1.8 day post- ovulation, and for relaxin, 11.4 +/- 2.6 day
post-ovulation. A delay of about 3 days was observed in the appearance in
circulation of CG (P < 0.05) and also of relaxin (P < 0.05) between
natural mated and embryo transfer conception cycles. Significant
differences (P < 0.05 for progesterone and P < 0.03 for oestradiol)
were obtained for the areas under the curves for progesterone and
oestradiol between days 12 and 16 in conception cycles compared with failed
pregnancies. These data provide the first observation of the normal
hormonal signals associated with maternal recognition of transferred
embryos during the peri- implantation period, and suggest that the use of
such an experimental primate embryo transfer model may help to elucidate
components of maternal and embryonic signal-response mechanisms during
embryo implantation.
相似文献
14.
Linkage of the MHC to familial multiple sclerosis suggests genetic heterogeneity. The Multiple Sclerosis Genetics Group 总被引:5,自引:0,他引:5
Haines JL; Terwedow HA; Burgess K; Pericak-Vance MA; Rimmler JB; Martin ER; Oksenberg JR; Lincoln R; Zhang DY; Banatao DR; Gatto N; Goodkin DE; Hauser SL 《Human molecular genetics》1998,7(8):1229-1234
Multiple sclerosis (MS) is a demyelinating autoimmune disease of the
central nervous system. While its etiology is not well understood, genetic
factors are clearly involved. Until recently, most genetic studies in MS
have been association studies using the case-control design testing
specific candidate genes and studying only sporadic cases. The only
consistently replicated finding has been an association with the HLA-DR2
allele within the major histocompatibility complex (MHC) on chromosome 6.
Using the genetic linkage design, however, evidence for and against linkage
of the MHC to MS has been found, fostering suggestions that sporadic and
familial MS have different etiologies. Most recently, two of four genomic
screens demonstrated linkage to the MHC, although specific allelic
associations were not tested. Here, a dataset of 98 multiplex families was
studied to test for an association to the HLA-DR2 allele in familial MS and
to determine if genetic linkage to the MHC was due solely to such an
association. Three highly polymorphic markers (HLA-DR, D6S273 and TNFbeta)
in the MHC demonstrated strong genetic linkage (parametric lod scores of
4.60, 2.20 and 1.24, respectively) and a specific association with the
HLA-DR2 allele was confirmed (TDT; P < 0.001). Stratifying the results
by HLA-DR2 status showed that the linkage results were limited to families
segregating HLA-DR2 alleles. These results demonstrate that genetic linkage
to the MHC can be explained by the HLA-DR2 allelic association. They also
indicate that sporadic and familial MS share a common genetic
susceptibility. In addition, preliminary calculations suggest that the MHC
explains between 17 and 62% of the genetic etiology of MS. This
heterogeneity is also supported by the minority of families showing no
linkage or association with loci within the MHC.
相似文献
15.
The intercellular adhesion molecule (ICAM) family of proteins 总被引:8,自引:0,他引:8
Macromolecular adhesive associations between cells are important for transmitting spatial and temporal information that is
critical for immune system function. One such group of proteins, the intercellular adhesion molecules (ICAMs), has grown as
newly identified members are revealed. In addition, the functions of the ICAMs, in general, have begun to be better understood,
including intracellular signaling events. This information has led to the design of novel therapeutic agents that may prove
effective in a variety of disease states. 相似文献
16.
17.
18.
19.
Human embryonic stem (ES) cells are pluripotent cells derived from blastocyst-stage embryos. It has been suggested that these cells should play a major role in transplantation medicine and be able to advance our knowledge in human embryology. We propose that these cells should also play a vital role in the creation of models of human disorders. This aspect would be most valuable where animal models failed to faithfully recapitulate the human phenotype. Lesch-Nyhan disease is caused by a mutation in the HPRT1 gene that triggers an overproduction of uric acid, causing gout-like symptoms and urinary stones, in addition to neurological disorders. Due to biochemical differences between humans and rodents, a mouse lacking the HPRT expression will fail to accumulate uric acid. In this research we demonstrate a model for Lesch-Nyhan disease by mutating the HPRT1 gene in human ES cells using homologous recombination. We have verified the mutation in the HPRT1 allele at the DNA and RNA levels. By using selection media, we show that HPRT1 activity is abolished in the mutant cells, and the HPRT1-cells show a higher rate of uric acid accumulation than the wild-type cells. Therefore, these cells recapitulate to some extent the characteristics of Lesch-Nyhan syndrome and can help researchers further investigate this genetic disease and analyze drugs that will prevent the onset of its symptoms. We therefore suggest that human diseases may be modeled using human ES cells. 相似文献
20.