全文获取类型
收费全文 | 4831篇 |
免费 | 236篇 |
国内免费 | 27篇 |
专业分类
耳鼻咽喉 | 51篇 |
儿科学 | 472篇 |
妇产科学 | 98篇 |
基础医学 | 540篇 |
口腔科学 | 64篇 |
临床医学 | 326篇 |
内科学 | 990篇 |
皮肤病学 | 98篇 |
神经病学 | 238篇 |
特种医学 | 169篇 |
外科学 | 562篇 |
综合类 | 159篇 |
预防医学 | 324篇 |
眼科学 | 192篇 |
药学 | 548篇 |
中国医学 | 23篇 |
肿瘤学 | 240篇 |
出版年
2022年 | 43篇 |
2021年 | 78篇 |
2020年 | 41篇 |
2019年 | 53篇 |
2018年 | 81篇 |
2017年 | 54篇 |
2016年 | 85篇 |
2015年 | 98篇 |
2014年 | 129篇 |
2013年 | 210篇 |
2012年 | 190篇 |
2011年 | 223篇 |
2010年 | 175篇 |
2009年 | 143篇 |
2008年 | 207篇 |
2007年 | 221篇 |
2006年 | 221篇 |
2005年 | 198篇 |
2004年 | 204篇 |
2003年 | 182篇 |
2002年 | 141篇 |
2001年 | 126篇 |
2000年 | 143篇 |
1999年 | 120篇 |
1998年 | 80篇 |
1997年 | 70篇 |
1996年 | 54篇 |
1995年 | 44篇 |
1994年 | 49篇 |
1993年 | 67篇 |
1992年 | 77篇 |
1991年 | 74篇 |
1990年 | 84篇 |
1989年 | 98篇 |
1988年 | 89篇 |
1987年 | 82篇 |
1986年 | 74篇 |
1985年 | 70篇 |
1984年 | 59篇 |
1983年 | 48篇 |
1980年 | 46篇 |
1979年 | 40篇 |
1978年 | 33篇 |
1977年 | 35篇 |
1975年 | 43篇 |
1974年 | 40篇 |
1973年 | 27篇 |
1972年 | 29篇 |
1971年 | 28篇 |
1970年 | 34篇 |
排序方式: 共有5094条查询结果,搜索用时 15 毫秒
51.
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
52.
53.
The distribution of cardiac output (c.o.) was measured by the radioactive microsphere method in rats at different time intervals after the implantation of carrageenanimpregnated sponges. The amount of blood distributed to the developing granulomata increased from day 5 after sponge implantation to day 7, but showed no further increase at day 10. A similar pattern in blood flow was observed in the skin covering the granulomata. Injection of PGE1 (100 ng) into the sponges led to an increase in blood flow, the magnitude of which became gradually larger between days 5 and 10. A similar, though less marked increase in sensitivity to PGE1 was observed in the skin covering the granulomata, PGE1 causing a significant increase in blood flow to the skin on day 10. These changes in sensitivity to exogenous PGE1 may be due to decreasing levels of endogenous PGE and/or maturation of the newly formed blood vessels in the granulation tissue. 相似文献
54.
Anuraag Shrivastav Shailly Varma Anurag Saxena John DeCoteau Rajendra K Sharma 《Journal of translational medicine》2007,5(1):58-6
Background
Colon cancer is the second leading cause of cancer deaths in the western world. If detected early, colorectal cancer is one of the most treatable forms of cancer. Unfortunately, very few people are screened. N-myristoyltransferase (NMT) catalyzes myristoylation of various proteins including oncoproteins. We have demonstrated earlier the alteration of NMT activity during the progression of colorectal cancer and established NMT as a putative therapeutic target for cancer. 相似文献55.
Escherichia coli Isolated from Domestic Animals Pathogenic for Gnotobiotic Piglets 总被引:1,自引:0,他引:1 下载免费PDF全文
Three strains of Escherichia coli isolated from infectious processes in a calf, a dog, and a cat were examined for their capacity to produce disease or death, or both, in newborn gnotobiotic piglets. The O groups represented by these particular strains of E. coli were O4: (canine origin), O6: (feline origin), and O39: (bovine origin). All three isolates upon oral administration proved to be pathogenic. Infection with the E. coli O4: (canine) or O39: (bovine) consistently produced signs of enteric coli-bacillosis and death in all 1- and 3-day-old piglets within 24 to 48 hr. The O6: (feline) isolate, on the other hand, produced a marked polyserositis and generally required 6 to 7 days to kill a piglet. Only the respective type of E. coli used in the particular trial was recovered from the diseased piglets. These findings suggest the possible role of domestic animals and household pets in the spread of potentially pathogenic E. coli to other species. 相似文献
56.
Protective cytotoxic T lymphocyte responses against paramyxoviruses induced by epitope-based DNA vaccines: involvement of IFN-gamma 总被引:1,自引:0,他引:1
Hsu SC; Obeid OE; Collins M; Iqbal M; Chargelegue D; Steward MW 《International immunology》1998,10(10):1441-1447
Plasmid DNA vectors have been constructed with minigenes encoding a single
cytotoxic T lymphocyte (CTL) epitope from either the M2 protein of
respiratory syncytial virus (RSV) or from the nucleoprotein of measles
virus (MV) with or without a signal sequence (also called secretory or
leader sequence). Following intradermal immunization, plasmids in which the
CTL epitopes were expressed in-frame with the signal sequence were more
effective at inducing peptide- and virus- specific CTL responses than
plasmids expressing CTL epitopes without the signal sequence. This
immunization resulted in protection against MV-induced encephalitis and a
significant reduction in viral load following RSV challenge. The reduction
of viral load following RSV challenge was abrogated by prior injection with
anti-IFN-gamma antibodies. These results highlight the ability of
epitope-based DNA immunization to induce protective immune responses to
well-defined epitopes and indicate the potential of this approach for the
development of vaccines against infectious diseases.
相似文献
57.
BCA200 has been described as a 200,000 Mr monomeric cell surface glycoprotein associated with human breast cancer. Since the physical properties and cellular distribution of BCA200 resemble those of c-erbB-2, antibodies to BCA200 were tested for the ability to bind a recombinant protein containing the c-erbB-2 extracellular domain (erbB-2 ECD). Three antibodies to distinct epitopes of BCA200 reacted with erbB-2 ECD but not with a control protein expressed in a similar baculovirus lysate. Control myeloma proteins and antibodies to four other antigens did not react with erbB-2 ECD. A protein with the expected molecular weight for erbB-2 ECD was also immunoprecipitated by anti-BCA200 antibody 520C9. We conclude that BCA200 is another synonym for c-erbB-2. 相似文献
58.
Debelenko LV; Brambilla E; Agarwal SK; Swalwell JI; Kester MB; Lubensky IA; Zhuang Z; Guru SC; Manickam P; Olufemi SE; Chandrasekharappa SC; Crabtree JS; Kim YS; Heppner C; Burns AL; Spiegel AM; Marx SJ; Liotta LA; Collins FS; Travis WD; Emmert-Buck MR 《Human molecular genetics》1997,6(13):2285-2290
Lung carcinoids occur sporadically and rarely in association with multiple
endocrine neoplasia type 1 (MEN1). There are no well defined genetic
abnormalities known to occur in these tumors. We studied 11 sporadic lung
carcinoids for loss of heterozygosity (LOH) at the locus of the MEN1 gene
on chromosome 11q13, and for mutations of the MEN1 gene using dideoxy
fingerprinting. Additionally, a lung carcinoid from a MEN1 patient was
studied. In four of 11 (36%) sporadic tumors, both copies of the MEN1 gene
were inactivated. All four tumors showed the presence of a MEN1 gene
mutation and loss of the other allele. Observed mutations included a 1 bp
insertion, a 1 bp deletion, a 13 bp deletion and a single nucleotide
substitution affecting a donor splice site. Each mutation predicts
truncation or potentially complete loss of menin. The remaining seven
tumors showed neither the presence of a MEN1 gene mutation nor 11q13 LOH.
The tumor from the MEN1 patient showed LOH at chromosome 11q13 and a
complex germline MEN1 gene mutation. The data implicate the MEN1 gene in
the pathogenesis of sporadic lung carcinoids, representing the first
defined genetic alteration in these tumors.
相似文献
59.
Paramagnetic macrocyclic chelates show promise as magnetic resonance (MR) imaging contrast agents due to stability and relaxivity comparable to those of DTPA-type chelates. For the three copper and manganese macrocyclic complexes studied in aqueous solution, T1 and T2 relaxivities ranged from 0.14 to 5.88 mM-1sec-1 at 6.25 MHz. In rats, the intravenous administration of 16 mumol/kg of Mn(cyclam) caused the liver T1 relaxation rate to double at 15 minutes after injection. T1 measurements by pulsed MR imaging and manganese analyses on excised tissue showed that both relaxation rate (1/T1) and manganese content of liver and kidney increase linearly with the dosage of Mn(cyclam). The linear relationship between 1/T1 and manganese content can be considered an "in tissue" relaxivity plot for the agent. The resulting relaxivity is 54 mM-1sec-1 in liver, compared with 3.1 mM-1sec-1 in aqueous solution. Although this work is preliminary, the implication for medical MR imaging applications is that macrocyclic contrast agents can be effective at approximately one-tenth the current typical dose used for gadolinium DTPA. 相似文献
60.