全文获取类型
收费全文 | 7446篇 |
免费 | 728篇 |
国内免费 | 3篇 |
出版年
2022年 | 56篇 |
2021年 | 117篇 |
2020年 | 55篇 |
2019年 | 55篇 |
2018年 | 78篇 |
2017年 | 89篇 |
2016年 | 148篇 |
2015年 | 273篇 |
2014年 | 288篇 |
2013年 | 389篇 |
2012年 | 449篇 |
2011年 | 415篇 |
2010年 | 291篇 |
2009年 | 252篇 |
2008年 | 392篇 |
2007年 | 415篇 |
2006年 | 386篇 |
2005年 | 367篇 |
2004年 | 363篇 |
2003年 | 377篇 |
2002年 | 342篇 |
2001年 | 98篇 |
2000年 | 63篇 |
1999年 | 74篇 |
1998年 | 125篇 |
1997年 | 77篇 |
1996年 | 72篇 |
1995年 | 79篇 |
1994年 | 49篇 |
1993年 | 71篇 |
1992年 | 58篇 |
1991年 | 58篇 |
1990年 | 56篇 |
1989年 | 45篇 |
1988年 | 44篇 |
1987年 | 68篇 |
1986年 | 60篇 |
1985年 | 65篇 |
1984年 | 76篇 |
1983年 | 41篇 |
1982年 | 68篇 |
1981年 | 71篇 |
1980年 | 63篇 |
1978年 | 59篇 |
1977年 | 44篇 |
1976年 | 43篇 |
1974年 | 62篇 |
1973年 | 58篇 |
1972年 | 51篇 |
1970年 | 38篇 |
排序方式: 共有8177条查询结果,搜索用时 15 毫秒
1.
Margaret Garden 《BMJ (Clinical research ed.)》1983,287(6402):1381
2.
Thorsten Thye Genevieve Scarisbrick Edmund N. L. Browne Margaret Amanua Chinbuah John Gyapong Ivy Osei Ellis Owusu-Dabo Stefan Niemann Sabine Rüsch-Gerdes Christian G. Meyer Rolf D. Horstmann 《PloS one》2009,4(7)
The gene of Cytotoxic T Lymphocyte-associated Antigen 4 (CTLA4), a negative regulator of T lymphocytes, contains a single-nucleotide polymorphism (SNP) at position +6230A->G (ct60A->G), which has been found associated with several autoimmune diseases and appears to reduce T-cell inhibitory activity. In Ghana, West Africa, we compared the frequencies of CTLA4 +6230 A/G and 6 haplotype-tagging SNPs in 2010 smear-positive, HIV-negative patients with pulmonary tuberculosis (TB) and 2346 controls matched for age, gender and ethnicity. We found no difference in allele frequencies between cases and controls. However, +6230A and a distinct CTLA4 haplotype and a diplotype comprising the +6230A allele were significantly less frequent among cases with large opacities in chest radiographs compared to those with small ones (Pcorrected [cor] = 0.002, Pcor = 0.00045, P = 0.0005, respectively). This finding suggests that an increased T-cell activity associated with the CTLA4 +6230G allele contributes to pathology rather than to protection in pulmonary TB. 相似文献
3.
Effects on Plant Growth Produced by Azotobacter paspali Related to Synthesis of Plant Growth Regulating Substances 总被引:2,自引:2,他引:0
S ummary . Treating seedling roots of several plant species with cultures of Azotobacter paspali changed plant growth and development and significantly increased weight of leaves and roots; effects were probably caused by plant growth regulators. Culture supernatant fluids contained indolyl-3-acetic acid, at least 3 gibberellins and 2 cytokinins. The added inoculum of A. paspali survived in plant rhizospheres for only a few weeks and no nitrogen was fixed in the root zone of young Paspalum notatum , the grass with which A. paspali is associated. 相似文献
4.
5.
Margaret Jacobi 《BMJ (Clinical research ed.)》1981,283(6304):1444-1445
6.
7.
8.
9.
10.