全文获取类型
收费全文 | 10309篇 |
免费 | 568篇 |
国内免费 | 6篇 |
专业分类
10883篇 |
出版年
2022年 | 50篇 |
2021年 | 94篇 |
2020年 | 53篇 |
2019年 | 65篇 |
2018年 | 105篇 |
2017年 | 95篇 |
2016年 | 171篇 |
2015年 | 253篇 |
2014年 | 307篇 |
2013年 | 930篇 |
2012年 | 513篇 |
2011年 | 572篇 |
2010年 | 350篇 |
2009年 | 332篇 |
2008年 | 566篇 |
2007年 | 578篇 |
2006年 | 576篇 |
2005年 | 598篇 |
2004年 | 560篇 |
2003年 | 556篇 |
2002年 | 621篇 |
2001年 | 174篇 |
2000年 | 176篇 |
1999年 | 169篇 |
1998年 | 160篇 |
1997年 | 126篇 |
1996年 | 117篇 |
1995年 | 107篇 |
1994年 | 97篇 |
1993年 | 146篇 |
1992年 | 165篇 |
1991年 | 119篇 |
1990年 | 93篇 |
1989年 | 104篇 |
1988年 | 92篇 |
1987年 | 86篇 |
1986年 | 76篇 |
1985年 | 81篇 |
1984年 | 90篇 |
1983年 | 62篇 |
1982年 | 87篇 |
1981年 | 74篇 |
1980年 | 66篇 |
1979年 | 49篇 |
1978年 | 61篇 |
1977年 | 33篇 |
1976年 | 47篇 |
1974年 | 31篇 |
1973年 | 35篇 |
1972年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
It has been mentioned in the field of aromatherapy that the fragrance of grapefruit has a refreshing and exciting effect, which suggests an activation of sympathetic nerve activity. It also can be assumed that the activation of sympathetic nerve innervating the white adipose tissue (WAT) facilitates lipolysis, then results in a suppression of body weight gain. This study addressed the effect of olfactory stimulation with the scent of grapefruit oil and lemon oil on the efferent nerve activity in the sympathetic branch of the WAT of the epididymis in the anesthetized rat. The results of the experiments demonstrated that the flavor of the citron group increased sympathetic nerve activity to WAT in anaesthetized rat, which suggests an increase in lipolysis and a suppression in body weight gain. 相似文献
112.
Matsumoto J Kako Y Morita Y Kabeya H Sakano C Nagai A Maruyama S Nogami S 《Parasitology international》2011,60(3):331-332
The ingestion of undercooked meat from wild animals can be a source of Toxoplasma gondii infection in humans and other animals. In this study, we determined the seroprevalence of T. gondii infection in 175 wild boars (Sus scrofa leucomystax) and 107 wild sika deer (Cervus nippon) hunted in 2004–2007 in Gunma Prefecture, Japan, by using a commercial latex agglutination test (LAT). Antibodies (LAT, 1:64 or higher) to T. gondii were found in 6.3% of wild boars and 1.9% of sika deer. This is the first record of T. gondii infection in wild deer in Japan, and deer and wild boar meat should be cooked well before human consumption. 相似文献
113.
Characterization of the cells in the repair tissue of full-thickness articular cartilage defects 总被引:1,自引:0,他引:1
H. Nakajima Tatsuhiko Goto Osamu Horikawa Toshiyuki Kikuchi Masayuki Shinmei 《Histochemistry and cell biology》1998,109(4):331-338
It is well established that a full-thickness articular cartilage defect is repaired with a fibrocartilaginous tissue, cells
of which are derived from undifferentiated mesenchymal stem cells in the bone marrow. To characterize the repair cells biochemically,
full-thickness defects were created in rabbit knee joints and the repair tissues taken at 3, 6, and 12 weeks after surgery.
The repair cells were cultured and examined biochemically to investigate the effects of four exogenous growth factors with
regard to the metabolism of type II collagen and proteoglycans. A significant increase of carboxy-terminal type II procollagen
peptide production was observed in the conditional medium of the repair cells, especially taken at 6 weeks after surgery,
in the presence of each growth factor. Glycosaminoglycan content was also increased and proteoglycan synthesis stimulated.
The repair cells taken at the early stage of the repair process could originally have more activity of type II collagen synthesis,
and the growth factors used could enhance the differentiation of the repair cells in vitro.
Accepted: 3 November 1997 相似文献
114.
115.
Summary A much higher incidence of alcohol flushing among Orientals in comparison to Caucasians, i.e., >50% vs 5%–10%, has been attributed to racial differences in alcohol-metabolizing enzymes. A large majority of Orientals are atypical in alcohol dehydrogenase-2 locus (ADH
2
), and their livers exhibit significantly higher ADH activity than the livers of most Caucasians. Approximately 50% of Orientals lack the mitochondrial aldehyde dehydrogenase (ALDH2) activity, and elimination of acetaldehyde might be disturbed. We determined by means of hybridization of genomic DNA samples with allele specific oligonucleotide probes, genotypes of the ADH
2
and ALDH
2
loci in Japanese alcohol flushers and nonflushers. We found that all individuals with homozygous atypical ALDH
2
2
/ALDH
2
2
and most of those with heterozygous atypical ALDH
1
2
/ALDH
2
2
were alcohol flushers, while all subjects with homozygous usual ALDH
1
2
/ALDH
1
2
were nonflushers. Frequency of the atypical ADH
2
2
was found to be higher in alcohol flushers than in nonflushers, but the statistical significance was not established in the sample size examined. 相似文献
116.
Liu T Yu H Zhang C Lu M Piao Y Ohba M Tang M Yuan X Wei S Wang K Ma A Feng X Qin S Mukai C Tsuji A Jin F 《Applied and environmental microbiology》2012,78(13):4752-4754
A novel rutin-α-L-rhamnosidase hydrolyzing α-L-rhamnoside of rutin, naringin, and hesperidin was purified and characterized from Aspergillus niger DLFCC-90, and the gene encoding this enzyme, which is highly homologous to the α-amylase gene, was cloned and expressed in Pichia pastoris GS115. The novel enzyme was classified in glycoside-hydrolase (GH) family 13. 相似文献
117.
118.
Akira Oda Kanato Yamagata Saya Nakagomi Hiroshi Uejima Pattama Wiriyasermkul Ryuichi Ohgaki Shushi Nagamori Yoshikatsu Kanai Hidekazu Tanaka 《Journal of neurochemistry》2014,128(2):246-255
Cholinergic neurons in the CNS are involved in synaptic plasticity and cognition. Both muscarinic and nicotinic acetylcholine receptors (nAChRs) influence plasticity and cognitive function. The mechanism underlying nAChR‐induced plasticity, however, has remained elusive. Here, we demonstrate morphological changes in dendritic spines following activation of α4β2* nAChRs, which are expressed on glutamatergic pre‐synaptic termini of cultured hippocampal neurons. Exposure of the neurons to nicotine resulted in a lateral enlargement of spine heads. This was abolished by dihydro‐β‐erythroidine, an antagonist of α4β2* nAChRs, but not by α‐bungarotoxin, an antagonist of α7 nAChRs. Tetanus toxin or a mixture of 2‐amino‐5‐phosphonovaleric acid and 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione, antagonists of NMDA‐ and AMPA‐type glutamate receptors, blocked the nicotine‐induced spine remodeling. In addition, nicotine exerted full spine‐enlarging response in the post‐synaptic neuron whose β2 nAChR expression was knocked down. Finally, pre‐treatment with nicotine enhanced the Ca2+‐response of the neurons to glutamate. These data suggest that nicotine influences the activity of glutamatergic neurotransmission through the activation of pre‐synaptic α4β2 nAChRs, resulting in the modulation of spinal architecture and responsiveness. The present findings may represent one of the cellular mechanisms underlying cholinergic tuning of brain function.
119.
Daichi Kita Satoshi Shibata Yuichiro Kikuchi Eitoyo Kokubu Koji Nakayama Atsushi Saito Kazuyuki Ishihara 《Applied and environmental microbiology》2016,82(6):1756-1766
Capnocytophaga ochracea is a Gram-negative, rod-shaped bacterium that demonstrates gliding motility when cultured on solid agar surfaces. C. ochracea possesses the ability to form biofilms; however, factors involved in biofilm formation by this bacterium are unclear. A type IX secretion system (T9SS) in Flavobacterium johnsoniae was shown to be involved in the transport of proteins (e.g., several adhesins) to the cell surface. Genes orthologous to those encoding T9SS proteins in F. johnsoniae have been identified in the genome of C. ochracea; therefore, the T9SS may be involved in biofilm formation by C. ochracea. Here we constructed three ortholog-deficient C. ochracea mutants lacking sprB (which encodes a gliding motility adhesin) or gldK or sprT (which encode T9SS proteins in F. johnsoniae). Gliding motility was lost in each mutant, suggesting that, in C. ochracea, the proteins encoded by sprB, gldK, and sprT are necessary for gliding motility, and SprB is transported to the cell surface by the T9SS. For the ΔgldK, ΔsprT, and ΔsprB strains, the amounts of crystal violet-associated biofilm, relative to wild-type values, were 49%, 34%, and 65%, respectively, at 48 h. Confocal laser scanning and scanning electron microscopy revealed that the biofilms formed by wild-type C. ochracea were denser and bacterial cells were closer together than in those formed by the mutant strains. Together, these results indicate that proteins exported by the T9SS are key elements of the gliding motility and biofilm formation of C. ochracea. 相似文献
120.
Tetsuya Oguma Asahi Matsuyama Mamoru Kikuchi Eiichi Nakano 《Applied microbiology and biotechnology》1993,39(2):197-203
The gene for cyclomaltodextrinase (CDase; EC 3.2.1.54) from Bacillus sphaericus E-244 was cloned in the recombinant plasmid pCD629. Sequencing a portion of pCD629 revealed a unique open reading frame of 1,773 nucleotides coding for a 591-amino-acid polypeptide. The deduced polypeptide sequence showed about 50% homology with that of a neopullulanase, and was slightly homologous to those of the cyclodextrin glucanotransferases and the -amylases. The optimum pH, specific activity and K
m value for -cyclodextrin of the CDase that has been produced in Escherichia coli cells were 8.0, 16.4 units/mg protein, and 0.41 mm, respectively. These values were almost identical to those from B. sphaericus E-244.
Correspondence to: T. Oguma 相似文献