全文获取类型
收费全文 | 1399篇 |
免费 | 114篇 |
专业分类
1513篇 |
出版年
2022年 | 15篇 |
2021年 | 17篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 15篇 |
2017年 | 10篇 |
2016年 | 15篇 |
2015年 | 45篇 |
2014年 | 66篇 |
2013年 | 93篇 |
2012年 | 90篇 |
2011年 | 82篇 |
2010年 | 41篇 |
2009年 | 37篇 |
2008年 | 74篇 |
2007年 | 86篇 |
2006年 | 80篇 |
2005年 | 74篇 |
2004年 | 85篇 |
2003年 | 93篇 |
2002年 | 87篇 |
2001年 | 19篇 |
2000年 | 28篇 |
1999年 | 22篇 |
1998年 | 18篇 |
1997年 | 15篇 |
1996年 | 23篇 |
1995年 | 23篇 |
1994年 | 20篇 |
1993年 | 18篇 |
1992年 | 20篇 |
1991年 | 19篇 |
1990年 | 13篇 |
1989年 | 25篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1980年 | 8篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 7篇 |
1972年 | 4篇 |
1970年 | 7篇 |
1969年 | 3篇 |
排序方式: 共有1513条查询结果,搜索用时 0 毫秒
31.
Ami E Nakahara K Sato A Nguyen JT Hidaka K Hamada Y Nakatani S Kimura T Hayashi Y Kiso Y 《Bioorganic & medicinal chemistry letters》2007,17(15):4213-4217
We designed several HIV protease inhibitors with various d-cysteine derivatives as P(2)/P(3) moieties based on the structure of clinical drug candidate, KNI-764. Herein, we report their synthesis, HIV protease inhibitory activity, HIV IIIB cell inhibitory activity, cellular toxicity, and inhibitory activity against drug-resistant HIV strains. KNI-1931 showed distinct selectivity against HIV proteases and high potency against drug-resistant strains, surpassing those of Ritonavir and Nelfinavir. 相似文献
32.
Tsukazaki H Yamashita K Yaguchi S Yamashita K Hagihara T Shigyo M Kojima A Wako T 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2011,122(3):501-510
To determine the chromosomal location of bunching onion (Allium fistulosum L.) simple sequence repeats (SSRs) and bulb onion (A. cepa L.) expressed sequence tags (ESTs), we used a complete set of bunching onion–shallot monosomic addition lines and allotriploid
bunching onion single alien deletion lines as testers. Of a total of 2,159 markers (1,198 bunching onion SSRs, 324 bulb onion
EST–SSRs and 637 bulb onion EST-derived non-SSRs), chromosomal locations were identified for 406 markers in A. fistulosum and/or A. cepa. Most of the bunching onion SSRs with identified chromosomal locations showed polymorphism in bunching onion (89.5%) as well
as bulb onion lines (66.1%). Using these markers, we constructed a bunching onion linkage map (1,261 cM), which consisted
of 16 linkage groups with 228 markers, 106 of which were newly located. All linkage groups of this map were assigned to the
eight basal Allium chromosomes. In this study, we assigned 513 markers to the eight chromosomes of A. fistulosum and A. cepa. Together with 254 markers previously located on a separate bunching onion map, we have identified chromosomal locations
for 766 markers in total. These chromosome-specific markers will be useful for the intensive mapping of desirable genes or
QTLs for agricultural traits, and to obtain DNA markers linked to these. 相似文献
33.
Knapp J Nakao M Yanagida T Okamoto M Saarma U Lavikainen A Ito A 《Molecular phylogenetics and evolution》2011,61(3):628-638
The family Taeniidae of tapeworms is composed of two genera, Echinococcus and Taenia, which obligately parasitize mammals including humans. Inferring phylogeny via molecular markers is the only way to trace back their evolutionary histories. However, molecular dating approaches are lacking so far. Here we established new markers from nuclear protein-coding genes for RNA polymerase II second largest subunit (rpb2), phosphoenolpyruvate carboxykinase (pepck) and DNA polymerase delta (pold). Bayesian inference and maximum likelihood analyses of the concatenated gene sequences allowed us to reconstruct phylogenetic trees for taeniid parasites. The tree topologies clearly demonstrated that Taenia is paraphyletic and that the clade of Echinococcus oligarthrus and Echinococcusvogeli is sister to all other members of Echinococcus. Both species are endemic in Central and South America, and their definitive hosts originated from carnivores that immigrated from North America after the formation of the Panamanian land bridge about 3 million years ago (Ma). A time-calibrated phylogeny was estimated by a Bayesian relaxed-clock method based on the assumption that the most recent common ancestor of E. oligarthrus and E. vogeli existed during the late Pliocene (3.0 Ma). The results suggest that a clade of Taenia including human-pathogenic species diversified primarily in the late Miocene (11.2 Ma), whereas Echinococcus started to diversify later, in the end of the Miocene (5.8 Ma). Close genetic relationships among the members of Echinococcus imply that the genus is a young group in which speciation and global radiation occurred rapidly. 相似文献
34.
Fission yeast cut3 and cut14, members of a ubiquitous protein family, are required for chromosome condensation and segregation in mitosis. 总被引:21,自引:1,他引:21 下载免费PDF全文
Y Saka T Sutani Y Yamashita S Saitoh M Takeuchi Y Nakaseko M Yanagida 《The EMBO journal》1994,13(20):4938-4952
Fission yeast temperature-sensitive mutants cut3-477 and cut14-208 fail to condense chromosomes but small portions of the chromosomes can separate along the spindle during mitosis, producing phi-shaped chromosomes. Septation and cell division occur in the absence of normal nuclear division, causing the cut phenotype. Fluorescence in situ hybridization demonstrated that the contraction of the chromosome arm during mitosis was defective. Mutant chromosomes are apparently not rigid enough to be transported poleward by the spindle. Loss of the cut3 protein by gene disruption fails to maintain the nuclear chromatin architecture even in interphase. Both cut3 and cut14 proteins contain a putative nucleoside triphosphate (NTP)-binding domain and belong to the same ubiquitous protein family which includes the budding yeast Smc1 protein. The cut3 mutant was suppressed by an increase in the cut14+ gene dosage. The cut3 protein, having the highest similarity to the mouse protein, is localized in the nucleus throughout the cell cycle. Plasmids carrying the DNA topoisomerase I gene partly suppressed the temperature sensitive phenotype of cut3-477, suggesting that the cut3 protein might be involved in chromosome DNA topology. 相似文献
35.
Funabashi H Ishikawa M Mie M Takahashi F Yanagida Y Aizawa M Kobatake E 《Biotechnology and bioengineering》2005,90(4):509-515
We developed an electrochemical detection method for evaluating cellular physiological status based on the stringent response as a means to monitor cell viability. A reporter plasmid was constructed by inserting the beta-galactosidase gene (lacZ) under the control of the rpoS promoter, and then used to transform E. coli cells. Electrochemical responses from the products catalyzed by beta-galactosidase expressed by these E. coli cells were detected using the chronoamperometric technique in a nondestructive manner. Comparisons of response currents between the relA-positive strain and relA-negative strain revealed that increases in these currents were caused by the stringent response due to the stressful alcoholic environment, and thus as a model of stressful cultivating conditions. The current was proportional to the beta-galactosidase activity assayed by a conventional method that required the destruction of cells. The cellular physiological status, which depends on the stringent response as a viability marker, therefore, could then be evaluated online with a current using the rpoS-lacZ reporter gene in the relA-positive strain without pretreatment. 相似文献
36.
Shinsuke Mikami Ayumu Nakashima Keigo Nakagawa Tatsuya Maruhashi Yumiko Iwamoto Masato Kajikawa Takeshi Matsumoto Yasuki Kihara Kazuaki Chayama Kensuke Noma Mitsuo Ochi Masahiro Nishimura Koichiro Tsuji Yukio Kato Chikara Goto Yukihito Higashi 《PloS one》2013,8(7)
Background
The purpose of this study was to determine whether autologous mesenchymal stem cells (MSCs) implantation improves endothelial dysfunction in a rabbit ischemic limb model.Methods
We evaluated the effect of MSC implantation on limb blood flow (LBF) responses to acetylcholine (ACh), an endothelium-dependent vasodilator, and sodium nitroprusside (SNP), an endothelium-independent vasodilator, in rabbits with limb ischemia in which cultured MSCs were implanted (n = 20) or saline was injected as a control group (n = 20). LBF was measured using an electromagnetic flowmeter. A total of 106 MSCs were implanted into each ischemic limb.Results
Histological sections of ischemic muscle showed that capillary index (capillary/muscle fiber) was greater in the MSC implantation group than in the control group. Laser Doppler blood perfusion index was significantly increased in the MSC implantation group compared with that in the control group. LBF response to ACh was greater in the MSC group than in the control group. After administration of NG-nitro-L-arginine, a nitric oxide synthase inhibitor, LBF response to ACh was similar in the MSC implantation group and control group. Vasodilatory effects of SNP in the two groups were similar.Conclusions
These findings suggest that MSC implantation induces angiogenesis and augments endothelium-dependent vasodilation in a rabbit ischemic model through an increase in nitric oxide production. 相似文献37.
Harris HS Facemire P Greig DJ Colegrove KM Ylitalo GM Yanagida GK Nutter FB Fleetwood M Gulland FM 《Journal of wildlife diseases》2011,47(1):246-254
A male neonatal Pacific harbor seal (Phoca vitulina richardsi) stranded off the coast of California, USA, was presented for rehabilitation with numerous partially haired, soft tissue masses around the mouth and in the oropharynx. Because of the extent of the lesions, the seal was humanely euthanized. Histologically, the masses consisted of subepithelial connective tissue and subcutis expanded by a proliferation of streams and bundles of spindle to stellate cells. Morphology of these cells suggested a neural origin, which was confirmed by positive immunohistochemistry for two neural markers, S-100 protein and glial fibrillary acidic protein, so the masses were diagnosed as neuroglial heterotopia. Heterotopic neuroglial tissue is a rare lesion comprised of benign mature neural tissue in an ectopic location with no connection to the central nervous system. Results of polycyclic aromatic hydrocarbon (PAH) metabolite analysis of bile indicated recent exposure to a petroleum source. Although fetal exposure to PAHs in utero can cause neurotoxicity and affect normal embryonic development, it is unknown whether gestational exposure occurred in this case. 相似文献
38.
Akiko Satake Takayuki Ohgushi Satoru Urano Koichiro Uchimura 《Ecological Research》2006,21(1):107-116
The tea leaf roller, Caloptilia theivora Walsingham (Lepidoptera: Gracillariinae), is one of the serious pests of tea plants in Japan. To understand the mechanism of seasonal occurrence of this insect pest, we developed a population dynamics model that explicitly incorporates the temperature-dependent development of the pest. The model predictions were compared with observed captures in pheromone traps at the experimental site of the Kagoshima Tea Experiment Research Station in Japan. The results showed that the emergence timing of the insect pest observed in the field was determined primarily by temperature. The relationship between the timing of adult emergence and the leaf damage level was also studied using a logistic regression model. The infestation level decreased as the interval between the adult peak emergence date and the date of tea plucking increased, implying that asynchrony between plant phenology and emergence of the insect pest is a critical factor reducing damage level. We examined how the damage level changes according to global warming. Increased temperature made the timing of insect appearance forward and enhance asynchrony of plant–pest phenology. Therefore, reduction of damage level by the insect pest is expected under global warming. 相似文献
39.
Koichiro Suzuki Kenji Kanazawa Kyoko Higuchi Naoko K. Nishizawa Satoshi Mori 《Biometals》1997,10(2):77-84
In a previous paper we reported that an acidic 36 kDa peptide is the most strongly induced peptide among several peptides induced by Fe deficiency in barley roots. In this paper, polyclonal antibodies were raised against the 36 kDa peptide. This peptide appeared in the roots of all the graminaceous species tested (barley, rye, wheat, oat, maize, sorghum and rice) in response to Fe deficiency. More of the peptide was found in the roots of graminaceous species which secrete higher amounts of mugineic acids (MAs) under Fe deficient nutrition status. Induction of the 36 kDa peptide was first observed on the third day of Fe deficiency, rising to a maximum value on the seventh day. The trend has a positive correlation with secretion of MAs during Fe deficiency. Further, resupply of Fe resulted in a decrease in peptide production on the second day, reaching a control level on the seventh day. The rate of decrease in peptide production was observed to be slower than that of MA secretion. Other nutrient stresses such as B excess, B deficiency, Cu excess, Cu deficiency, Mn excess, Mn deficiency, Zn excess and Zn deficiency induced far less of the peptide. The specific expression of the 36 kDa peptide in roots of graminaceous species under Fe deficiency suggested the positive association of the peptide with a specific Fe deficiency tolerance mechanism in graminaceous plants. 相似文献
40.