全文获取类型
收费全文 | 2613篇 |
免费 | 134篇 |
国内免费 | 290篇 |
专业分类
3037篇 |
出版年
2024年 | 5篇 |
2023年 | 28篇 |
2022年 | 39篇 |
2021年 | 58篇 |
2020年 | 48篇 |
2019年 | 90篇 |
2018年 | 66篇 |
2017年 | 72篇 |
2016年 | 74篇 |
2015年 | 87篇 |
2014年 | 132篇 |
2013年 | 178篇 |
2012年 | 112篇 |
2011年 | 132篇 |
2010年 | 118篇 |
2009年 | 167篇 |
2008年 | 178篇 |
2007年 | 176篇 |
2006年 | 173篇 |
2005年 | 136篇 |
2004年 | 124篇 |
2003年 | 119篇 |
2002年 | 97篇 |
2001年 | 104篇 |
2000年 | 100篇 |
1999年 | 69篇 |
1998年 | 58篇 |
1997年 | 43篇 |
1996年 | 43篇 |
1995年 | 25篇 |
1994年 | 31篇 |
1993年 | 21篇 |
1992年 | 17篇 |
1991年 | 12篇 |
1990年 | 18篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有3037条查询结果,搜索用时 19 毫秒
121.
《Journal of Asia》2020,23(1):177-185
Acetaminophen (APAP) is an effective and widely used analgesic. However, APAP overdose is the principal cause of acute liver failure (ALF) in many countries. Here, we report the phenomenon of liver melanization which occurred before APAP-induced ALF in mice. A melanic surface induced by APAP which was time- and dose-dependent in the silkworm invertebrate model was observed. In addition, an APAP-induced acute tissue failure model (ATF) was established using a metabolic detoxification tissue fat body which simulated mouse liver. An investigation of the anabolic mechanism of melanin in experimental animals showed that dopaquinone and dopamine which were synthesized from tyrosine via dopa in silkworms were further metabolized to melanin, while in mice, epinephrine was synthesized via the dopamine branch and melanin was only synthesized via the dopaquinone branch. On this basis, it is proposed that melanin-metabolic levels in plasma could be used as an early diagnostic marker of APAP overdose and the black spots on insect epidermis could be used as a fast detection model of toxicity. 相似文献
122.
123.
Ilse P. Munyon John F. Hubstenberger Greory C. Phillips 《In vitro cellular & developmental biology. Plant》1989,25(3):293-296
Summary Androgenesis occurred from chile pepper (Capsicum annuum L.) anthers incubated in a continuous warm environment (29° C) with continuous light. Forty plantes and embryoids were retrieved
from anther cultures and anllyzed for isozyme markers. Of these, 35 exhibited a single allele for markers suggesting microspore
origin, while 5 were heterozygous indicating somatic tissue origin. Chromosome numbers were confirmed for 21 plantlets, of
which 16 were haploid and 5 were diploid. However, two plants exhibited a single allele for an isozyme marker but possessed
the diploid chromosome number, suggesting spontaneous doubling. Anther cultures also produced callus. Nearly 92% of the slow-growing
calli sampled were heterozygous for the isozyme marker, suggesting somatic tissue origin. More than 46% of the fast-growing
calli exhibited only one allele for the marker, indicating microspore origin. Callus did not regenerate plantlets. The occurrence
of both heterozygous and homozygous diploid plantlets from pepper anther cultures has important implications for applied breeding
programs. 相似文献
124.
Screening apples for OPD20/600 using sequence-specific primers 总被引:13,自引:0,他引:13
H. Yang S. S. Korban 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1996,92(2):263-266
Apple scab, caused by Venturia inaequalis (Cke.) Wint., is the most serious disease of apple trees in many areas of the world. Resistance to V. inaequalis, derived from the small-fruited species Malus floribunda 821, is determined by a major dominant gene, Vf. Using random decamer primers, we identified a RAPD marker, OPD20/600, which is linked to the Vf gene. OPD20/600 was then cloned and sequenced. Sequence-specific primers based on the marker were used to further screen M. floribunda 821, 7 scab-susceptible apple cultivars, 10 scab-resistant apple cultivars, and 28 scab-resistant Coop selections. The sequence-specific primers allowed identification of polymorphisms of OPD20/600 based on the presence or absence of a single band. The advantages of sequence-specific primers over decamer primers for developing genetic markers are discussed. 相似文献
125.
The purpose of our study was the application of non-isotopic in situ hybridization with chromosome-specific repetitive DNA probes for the determination of cytogenetically aberrant cells in routine cytological materials, such as cervical smears and breast tumour aspirates. Hyperdiploid cells in fine needle aspirates (FNA) of breast tumours could be visualized by in situ hybridization with a chromosome l-specific repetitive DNA probe. However, for the evaluation of a specific cell type in heterogeneous cell populations, i.e. cervical smears, a procedure combining immunocytochemistry and in situ hybridization can be required. Therefore, we developed a combination protocol using β-galactosidase/ ferri-ferrocyanide (blue-green) for immunocytochemistry and peroxidase/DAB (brown-black) for detection of the DNA probe. the described protocol enabled us to distinguish squamous epithelial cells within heterogeneous cell populations. By combining the chromosome 1 DNA probe with a specific cytokeratin marker it was possible to identify the chromosomal abnormal cells within cervical smears. 相似文献
126.
Edoardo Francini Fang-Shu Ou Stefano Lazzi Roberto Petrioli Andrea G. Multari Guido Pesola Luciana Messuti Elena Colombo Virginia Livellara Serena Bazzurri Sara Cherri Salvatora T. Miano Eric G. Wolfe Steven R. Alberts Joleen M. Hubbard Harry H. Yoon Guido Francini 《Translational oncology》2021,14(2)
BackgroundHigh tumor infiltrating lymphocytes (TILs) density was previously shown to be associated with favorable prognosis for patients with colon cancer (CC). However, the impact of TILs on overall survival (OS) of stage II CC patients who received adjuvant chemotherapy (ADJ) or not (no-ADJ) is unknown. We assessed the prognostic value of CD3+ TILs in stage II CC patients according to whether they had ADJ or not.MethodsPatients treated with curative surgery for stage II CC (2002–2013) were selected from the Santa Maria alle Scotte Hospital registry. TILs at the invasive front, center of tumor, and stroma were determined by immunohistochemistry and manually quantified as the rate of TILs/total tissue areas. High TILs (H-TILs) was defined as >20%. Patients were categorized as high or low TILs (L-TILs) and ADJ or no-ADJ.ResultsOf the 678 patients included, 137 (20%) received ADJ and 541 (80%) did not. The distribution of the 4 groups were: 16% (L-TIL/ADJ), 64% (L-TIL/no-ADJ), 5% (H-TIL/ADJ), 15% (H-TIL/no-ADJ). Compared to H-TILs/no-ADJ, ADJ patients showed a significantly increased OS (P<.01) regardless of the TILs rate whereas L-TILs/no-ADJ had significantly decreased OS and higher risk of death (HR=1.41; 95% CI, 1.06–1.88; P<.0001). On multivariable analysis, the unfavorable prognostic value of L-TILs (vs. H-TILs) for no-ADJ patients was confirmed (HR=1.36; 95% CI 1.02, 1.82; P=.0373).ConclusionLow CD3+ TILs rate was associated with shorter OS in those with stage II colon cancer who did not receive adjuvant therapy. Low CD3+ TILs could be considered an additional risk factor for still ADJ-untreated stage II CC patients, which could facilitate clinical decision making. 相似文献
127.
A novel mutated acetolactate synthase gene conferring specific resistance to pyrimidinyl carboxy herbicides in rice 总被引:3,自引:0,他引:3
Acetolactate synthase (ALS) is the first common enzyme in the biosynthetic pathway of branched-chain amino acids. Mutations
of specific amino acids in ALS have been known to confer resistance to ALS-inhibiting herbicides such as sulfonylureas and
pyrimidinyl carboxy (PC) herbicides. However, mutations conferring exclusive resistance to PC have not yet been reported to
date. We selected PC resistant rice calli, which were derived from anther culture, using one of the PCs, bispyribac-sodium
(BS), as a selection agent. Two lines of BS-resistant plants carrying a novel mutation, the 95th Glycine to Alanine (G95A),
in ALS were obtained. In vitro ALS activity assay indicated that the recombinant protein of G95A-mutated ALS (ALS-G95A) conferred
highly specific resistance to PC herbicides. In order to determine if the ALS-G95A gene could be used as a selection marker
for rice transformation, the ALS-G95A gene was connected to ubiquitin promoter and introduced into rice. PC resistant plants
containing integrated ALS-G95A gene were obtained after selection with BS as a selection agent. In conclusion, novel G95A
mutated ALS gene confers highly specific resistant to PC-herbicides and can be used as a selection marker. 相似文献
128.
利用分子标记定位农垦58S的光敏核不育基因 总被引:17,自引:0,他引:17
对农垦58S(Oryzasativasp.japonica)/大黑矮生标记基因系FL2组合组建可育集团和不育集团,并以亲本为对照进行了RFLP、RAPD和双引物RAPD分析,结果第12染色体上的一个单拷贝标记G2140与光敏核不育基因连锁遗传,二者间的遗传图距为14.1cM(centimorgan)。在筛选过的1040个随机单引物和190个双引物中,仅引物OPAU10扩增出与光敏核不育基因连锁的1.5kbDNA片段,回收、克隆该DNA片段并制备探针,将其转换成共显性的RFLP标记并命名为OPAU101500。分离群体连锁分析表明该标记与标记G2140紧密连锁,将农垦58S的一对光敏核不育基因定位于第12染色体上。 相似文献
129.
This study introduces the construction of the first intraspacific genetic linkage map of the A-genome diploid cotton with newly developed simple sequence repeat (SSR) markers using 189 F2 plants derived from the cross of two Asiatic parents were detected using 6 092 pairs of SSR primers. Two-hundred and sixty-eight pairs of SSR pdmers with better polymorphisms were picked out to analyze the F2 population. In total, 320 polymorphic bands were generated and used to construct a linkage map with JoinMap3.0. Two-hundred and sixty-seven loci, Including three phenotypic traits were mapped at a logarithms of odds ratio (LOD) ≥ 3.0 on 13 linkage groups. The total length of the map was 2 508.71 cM, and the average distance between adjacent markers was 9.40 cM. Chromosome assignments were according to the association of linkages with our backbone tetraploid specific map using the 89 similar SSR loci. Comparisons among the 13 suites of orthologous linkage groups revealed that the A-genome chromosomes are largely collinear with the At and Dt sub-genome chromosomes. Chromosomes associated with inversions suggested that allopolyploidization was accompanied by homologous chromosomal rearrangement. The inter-chromosomal duplicated loci supply molecular evidence that the A-genome diploid Asiatic cotton is paleopolyploid. 相似文献
130.
Stem cells intrigue. They have the ability to divide exponentially, recreate the stem cell compartment, as well as create differentiated cells to generate tissues. Therefore, they should be natural candidates to provide a renewable source of cells for transplantation applied in regenerative medicine. Stem cells have the capacity to generate specific tissues or even whole organs like the blood, heart, or bones. A subgroup of stem cells, the neural stem cells (NSCs), is characterized as a self-renewing population that generates neurons and glia of the developing brain. They can be isolated, genetically manipulated and differentiated in vitro and reintroduced into a developing, adult or a pathologically altered central nervous system. NSCs have been considered for use in cell replacement therapies in various neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease. Characterization of genes with tightly controlled expression patterns during differentiation represents an approach to understanding the regulation of stem cell commitment. The regulation of stem cell biology by the ATP-binding cassette (ABC) transporters has emerged as an important new field of investigation. As a major focus of stem cell research is in the manipulation of cells to enable differentiation into a targeted cell population; in this review, we discuss recent literatures on ABC transporters and stem cells, and propose an integrated view on the role of the ABC transporters, especially ABCA2, ABCA3, ABCB 1 and ABCG2, in NSCs' proliferation, differentiation and regulation, along with comparisons to that in hematopoietic and other stem cells. 相似文献