全文获取类型
收费全文 | 5916篇 |
免费 | 438篇 |
国内免费 | 384篇 |
出版年
2023年 | 59篇 |
2022年 | 69篇 |
2021年 | 124篇 |
2020年 | 147篇 |
2019年 | 176篇 |
2018年 | 162篇 |
2017年 | 129篇 |
2016年 | 168篇 |
2015年 | 182篇 |
2014年 | 260篇 |
2013年 | 355篇 |
2012年 | 215篇 |
2011年 | 283篇 |
2010年 | 242篇 |
2009年 | 322篇 |
2008年 | 292篇 |
2007年 | 329篇 |
2006年 | 302篇 |
2005年 | 294篇 |
2004年 | 281篇 |
2003年 | 232篇 |
2002年 | 196篇 |
2001年 | 186篇 |
2000年 | 144篇 |
1999年 | 162篇 |
1998年 | 140篇 |
1997年 | 124篇 |
1996年 | 118篇 |
1995年 | 123篇 |
1994年 | 107篇 |
1993年 | 90篇 |
1992年 | 95篇 |
1991年 | 93篇 |
1990年 | 68篇 |
1989年 | 69篇 |
1988年 | 52篇 |
1987年 | 48篇 |
1986年 | 39篇 |
1985年 | 58篇 |
1984年 | 38篇 |
1983年 | 25篇 |
1982年 | 31篇 |
1981年 | 19篇 |
1980年 | 24篇 |
1979年 | 13篇 |
1978年 | 14篇 |
1977年 | 11篇 |
1976年 | 12篇 |
1975年 | 4篇 |
1973年 | 6篇 |
排序方式: 共有6738条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Xiangjun Kong Aziz Khan Zhiling Li Jingyi You Fazal Munsif Haodong Kang Ruiyang Zhou 《Saudi Journal of Biological Sciences》2020,27(12):3691-3699
Chalcone synthase (CHS) is a key enzyme and producing flavonoid derivatives as well play a vital roles in sustaining plant growth and development. However, the systematic and comprehensive analysis of CHS genes in island cotton (G. barbadense) has not been reported yet especially response to cytoplasmic male sterility (CMS). To fill this knowledge gap, a genome-wide investigation of CHS genes were studied in island cotton. A total of 20 GbCHS genes were identified and grouped into five GbCHSs. The gene structure analysis revealed that most of GbCHS genes consisted of two exons and one intron, and 20 motifs were identified. Twenty five pairs duplicated events (12 GbCHS genes) were identified including 23 segmental duplication pairs and two tandem duplication events, representing that GbCHS gene family amplification mainly owned to segmental duplication events and evolving slowly. Gene expression analysis exhibited that the GbCHS family genes presented a diversity expression patterns in various organs of cotton. Coupled with functional predictions and gene expression, the abnormal expression of GbCHS06, 10, 16 and 19 might be associated with pollen abortion of CMS line in island cotton. Conclusively, GbCHS genes exhibited diversity and conservation in many aspects, which will help to better understand functional studies and a reference for CHS research in island cotton and other plants. 相似文献
5.
6.
S. M. Kaeppler 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(3):384-392
The power to detect QTL using near-isogenic line (NIL) comparisons versus recombinant inbred (RI) populations was assessed.
The power to detect QTL was found to be generally greater when using RI populations than when using NIL contrasts. Power to
detect QTL with NIL contrasts never exceeded that of RI populations when the number of RI lines is maximized relative to replication
of lines for a given number of experimental units. The relative power of NIL contrasts is highest for traits with high heritability
and when a gain in precision is realized due to increased replication of entries. Although NIL populations are generally less
powerful than RI populations of similar size, some practical considerations may enhance the value of these materials. Availability
of NILs allows the genetic effect of a specific chromosome region to be determined by comparing two lines; all RI lines in
a population need to be rescored for each new trait even if the effect of a specific chromosome region is suspected. NIL comparisons
may allow genetic differences to be detected by visual inspection; genetic effects can only be expressed as means and variances
with recombinant inbred populations. In summary, RI populations generally, and in some cases, substantially, provide better
power for QTL detection than NIL comparisons. Practical considerations, however, indicate that many factors need to be considered
when choosing a population structure to meet an experimental objective.
Received: 12 December 1996 / Accepted: 21 March 1997 相似文献
7.
We have established a series of 20 colorectal cancer cell lines and performed cytogenetic and RFLP analyses to show that the
recurrent genetic abnormalities of chromosomes 1, 5, 17 and 18 associated with multistep tumorigenesis in colorectal cancer,
and frequently detected as recurrent abnormalities in primary tumours, are also retained in long-term established cell lines.
Earlier studies by us and other investigators showed that allelic losses of chromosomes 1 and 17 in primary colorectal cancers
predicted poorer survival for the patients (P = 0.03). We utilized the cell lines to identify specific chromosomal sites or gene(s) on chromosomes 1 and 17 which confer
more aggressive phenotype. Cytogenetic deletions of chromosome 1p were detected in 14 out of the 20 (70%) cell lines, whereas
allelic deletions for 1p using polymorphic markers were detected in 13 out of 18 (72%) informative cell lines for at least
one polymorphic marker. We have performed Northern blotting, immunohistochemical staining (p53 mRNA, protein) and RFLP analysis
using several probes including p53 and nm23. RFLP analysis using a total of seven polymorphic markers located on 17p and 17q
arms showed allelic losses aroundthe p53 locus in 16 out of the 20 cell lines (80%), four of which were losses of thep53 locus itself. In addition, seven cell lines (out of nine informative cases) also showed losses of thenm23 gene, four with concurrent losses of thep53 locus, while the remaining three were homozygous. In addition, five out of seven cell lines withnm23 deletions were derived from hepatic metastatic tumours, and one cell line was obtained from recurrent tumour. A comparison
between allelic deletions of 1p and functional loss ofnm23 gene revealed a close association between these two events in cell lines derived from hepatic metastasis. Following immunohistochemical
staining, nine out of the twenty cell lines showed high levels (25–80%) of mutant p53, four showed intermediate levels (>20%),
and seven had undetectable levels of the protein. Of these seven, four showed complete absence of mRNA. Of the remaining three
cell lines one showed aberrant mRNA due to germline rearrangement of thep53 gene, whereas in two cell lines normal levels of mRNA were present. Nineteen of the 20 cell lines had normal germline configurations
for thep53 gene, while one showed a rearrangement. These data suggest that functional loss ofp53 andnm23 genes accomplished by a variety of mechanisms may be associated with poor prognosis and survival. In addition, concurrent
deletions of chromosome regions 17p, 17q and 1p were closely associated with high-stage hepatic metastatic disease. These
cell lines with well-characterized genetic alterations and known clinical history provide an invaluable source of material
for various biological and clinical studies relating to multistep colorectal tumorigenesis. 相似文献
8.
9.
Recent evidence suggests that the nutritional state of male Mediterranean fruit flies, Ceratitis capitata (Wied.) (medfly), is an important influence on various components of their reproductive biology, including mating success. The objective of the present study was to examine experimentally the effect of temporary starvation on the mating success of wild male C. capitata. Males were maintained on protein–sugar or sugar-only diets, and for each diet we compared the mating success of continuously fed males versus males starved for 18 or 24 h immediately before testing. In trials conducted on field-caged, host trees, males starved for 24 h obtained only about half as many matings as fed males for both diets. However, when the starvation period was 18 h, starved males reared on the protein–sugar diet mated significantly less frequently than fed males, whereas starved males reared on sugar mated as often as fed males. Measurements of male pheromone calling and female attraction revealed that reduced mating success likely reflected the decreased signaling activity of starved males. 相似文献
10.