全文获取类型
收费全文 | 33733篇 |
免费 | 3046篇 |
国内免费 | 6篇 |
出版年
2023年 | 118篇 |
2021年 | 317篇 |
2020年 | 235篇 |
2019年 | 264篇 |
2018年 | 531篇 |
2017年 | 548篇 |
2016年 | 746篇 |
2015年 | 881篇 |
2014年 | 1061篇 |
2013年 | 1445篇 |
2012年 | 2376篇 |
2011年 | 2583篇 |
2010年 | 1494篇 |
2009年 | 1170篇 |
2008年 | 2123篇 |
2007年 | 2222篇 |
2006年 | 2006篇 |
2005年 | 1886篇 |
2004年 | 1867篇 |
2003年 | 1767篇 |
2002年 | 1703篇 |
2001年 | 921篇 |
2000年 | 997篇 |
1999年 | 608篇 |
1998年 | 432篇 |
1997年 | 301篇 |
1996年 | 319篇 |
1995年 | 317篇 |
1994年 | 296篇 |
1993年 | 287篇 |
1992年 | 267篇 |
1991年 | 220篇 |
1990年 | 240篇 |
1989年 | 216篇 |
1988年 | 225篇 |
1987年 | 204篇 |
1986年 | 197篇 |
1985年 | 237篇 |
1984年 | 270篇 |
1983年 | 213篇 |
1982年 | 279篇 |
1981年 | 257篇 |
1980年 | 204篇 |
1979年 | 181篇 |
1978年 | 158篇 |
1977年 | 152篇 |
1976年 | 144篇 |
1975年 | 127篇 |
1974年 | 138篇 |
1973年 | 111篇 |
排序方式: 共有10000条查询结果,搜索用时 213 毫秒
31.
32.
Background
While traditional models of Alzheimer's disease focused on large fibrillar deposits of the Aβ42 amyloid peptide in the brain, recent work suggests that the major pathogenic effects may be attributed to SDS-stable oligomers of Aβ42. These Aβ42 oligomers represent a rational target for therapeutic intervention, yet factors governing their assembly are poorly understood. 相似文献33.
We have earlier demonstrated that a mixed population of immunologically specific killer cells, including cytotoxic T lymphocytes, non-T (“B”) lymphocytes and monocytes, infiltrate “sponge matrix” allografts at the peak of rejection on Day 8 after transplantation. We have now performed a sequential study covering both early and late stages of the rejection response. We demonstrate that the early infiltrating killer cells are sensitive to anti-Ø and anti-T cell serum plus complement treatment but the late killer cells are not. This finding indicates that the first cytotoxic host cells infiltrating the allograft are predominantly T lymphocytes, whereas as the rejection process proceeds also cytotoxic non-T (“B”) lymphocytes and monocytes are recruited to the site of inflammation. 相似文献
34.
Ralf J. Jäger Vincent R. Harley Rudolf A. Pfeiffer Peter N. Goodfellow Gerd Scherer 《Human genetics》1992,90(4):350-355
A familial mutation in SRY, the gene coding for the testis-determining factor TDF, was identified in an XY female with gonadal dysgenesis, her father, her two brothers and her uncle. The mutation consists of a T to C transition in the region of the SRY gene coding for a protein motif known as the high mobility group (HMG) box, a protein domain known to confer DNA-binding specificity on the SRY protein. This point mutation results in the substitution, at amino acid position 109, of a serine residue for phenylalanine, a conserved aromatic residue in almost all HMG box motifs known. This F109S mutation was not found in 176 male controls. When recombinant wildtype SRY and SRYF109S mutant protein were tested in vitro for binding to the target site AAC AAAG, no differences in DNA-binding activity were observed. These results imply that the F109S mutation either is a rare neutral sequence variant, or produces an SRY protein with slightly altered in vivo activity, the resulting sex phenotype depending on the genetic back-ground or environmental factors.This paper is dedicated by G. S. to Professor Ulrich Wolf on the occasion of his 60th birthday 相似文献
35.
36.
37.
38.
39.
R. Brändén T. Nilsson S. Styring 《Biochemical and biophysical research communications》1980,92(4):1297-1305
A sensitive and reliable method to determine the stereochemical composition of 3-phosphoglyceric acid is presented. Results obtained with this method show that 3-phosphoglyceric acid formed in the ribulose-1,5-bisphosphate carboxylase reaction is a mixture of 10% L-3-PGA and 90% D-3-PGA. 相似文献
40.
Caroline van Haaften-Day Peter Russell Susan Carr Lesley Wright 《In vitro cellular & developmental biology. Plant》1988,24(10):965-971
Summary A cell line derived from a human ovarian carcinosarcoma was established in tissue culture and in nude mice. Two sublines,
LDF and HDF, separated by discontinuous density centrifugation were also established from the parent line JoN. The cloning
efficiency of the JoN line was 21%. Morphologic features of adenocarcinoma cells characteristic of the parent JoN cells were
retained in the sublines and clones; all lines showed the same karyotype and DNA content (pseudodiploid and pseudotetraploid).
Keratin, as demonstrated immunohistochemically, was strongly expressed in the parent line JoN and the xenograft tumor, but
not at all in the LDF sublines and only moderately in the HDF sublines. Vimentin, however, was expressed in neither the parent
line JoN nor the xenograft tumor, but was present in both sublines. Transglutaminase and plasminogen activator activity was
high in the parent line JoN. Neither, sublines nor clones showed the same high enzyme activity as the parent line. It is concluded
that this human tumor line JoN is comprised of epithelial cells, capable of multidirectional differentiation. 相似文献