全文获取类型
收费全文 | 7740篇 |
免费 | 509篇 |
国内免费 | 2篇 |
专业分类
8251篇 |
出版年
2022年 | 39篇 |
2021年 | 61篇 |
2020年 | 38篇 |
2019年 | 79篇 |
2018年 | 111篇 |
2017年 | 64篇 |
2016年 | 120篇 |
2015年 | 218篇 |
2014年 | 247篇 |
2013年 | 480篇 |
2012年 | 402篇 |
2011年 | 405篇 |
2010年 | 268篇 |
2009年 | 256篇 |
2008年 | 418篇 |
2007年 | 414篇 |
2006年 | 426篇 |
2005年 | 420篇 |
2004年 | 413篇 |
2003年 | 413篇 |
2002年 | 378篇 |
2001年 | 190篇 |
2000年 | 240篇 |
1999年 | 187篇 |
1998年 | 115篇 |
1997年 | 107篇 |
1996年 | 104篇 |
1995年 | 86篇 |
1994年 | 95篇 |
1993年 | 69篇 |
1992年 | 130篇 |
1991年 | 106篇 |
1990年 | 118篇 |
1989年 | 102篇 |
1988年 | 88篇 |
1987年 | 72篇 |
1986年 | 80篇 |
1985年 | 53篇 |
1984年 | 70篇 |
1983年 | 49篇 |
1982年 | 47篇 |
1981年 | 42篇 |
1980年 | 50篇 |
1979年 | 40篇 |
1978年 | 40篇 |
1977年 | 32篇 |
1976年 | 31篇 |
1975年 | 28篇 |
1974年 | 31篇 |
1973年 | 33篇 |
排序方式: 共有8251条查询结果,搜索用时 15 毫秒
941.
Nagai Y Nochi T Watanabe K Watanabe K Aso H Kitazawa H Matsuzaki M Ohwada S Yamaguchi T 《Cell and tissue research》2005,322(3):455-462
A pro-inflammatory cytokine, interleukin 18 (IL-18), induces intracellular expression of IL-1 and the release of IL-6. IL-1
and IL-6 has been detected in anterior pituitary cells, suggesting that IL-18 is produced in anterior pituitary cells and
may serve to aid immuno-endocrine regulation. In the present study, we addressed this hypothesis by investigating the intracellular
localization of IL-18 and its receptor in bovine anterior pituitary gland. IL-18 mRNA and its protein were detected in the
anterior pituitary gland by RT-PCR and Western blotting. In situ hybridization showed that IL-18 mRNA was expressed in the
anterior pituitary cells. Immunohistochemistry of IL-18 and specific hormones revealed the presence of IL-18 in somatotrophs.
Furthermore, the expression of GH mRNA in IL-18 immunoreactive cells was confirmed by immuno-laser microdissection. These
results first demonstrated that somatotrophs produced IL-18. Subsequently, the distribution of the IL-18 receptor alpha (IL-18Rα)
was investigated in order to understand IL-18 signaling among the anterior pituitary cells. Bovine IL-18Rα cDNA was partially
sequenced and detected in the anterior pituitary gland by RT-PCR. Immunohistochemistry of IL-18Rα, IL-18 and GH showed that
IL-18Rα was co-localized in IL-18 immunoreactive cells or somatotrophs. These data suggest that IL-18 acts on somatotrophs
as an immuno-endocrine mediator through the autocrine pathway.
This work was supported by a Grant-in-Aid for Scientific Research (B) (No.13460122) from the Ministry of Education, Science
and Culture of Japan 相似文献
942.
BACKGROUND AND AIMS: Photorespiration occurs in C4 plants, although rates are small compared with C3 plants. The amount of glycine decarboxylase in the bundle sheath (BS) varies among C4 grasses and is positively correlated with the granal index (ratio of the length of appressed thylakoid membranes to the total length of all thylakoid membranes) of the BS chloroplasts: C4 grasses with high granal index contained more glycine decarboxylase per unit leaf area than those with low granal index, probably reflecting the differences in O2 production from photosystem II and the potential photorespiratory capacity. Thus, it is hypothesized that the activities of peroxisomal enzymes involved in photorespiration are also correlated with the granal development. METHODS: The granal development in BS chloroplasts was investigated and activities of the photorespiratory enzymes assayed in 28 C4 grasses and seven C3 grasses. KEY RESULTS: The NADP-malic enzyme grasses were divided into two groups: one with low granal index and the other with relatively high granal index in the BS chloroplasts. Both the NAD-malic enzyme and phosphoenolpyruvate carboxykinase grasses had high granal index in the BS chloroplasts. No statistically significant differences were found in activity of hydroxypyruvate reductase between the C3 and C4 grasses, or between the C4 subtypes. The activity of glycolate oxidase and catalase were smaller in the C4 grasses than in the C3 grasses. Among the C4 subtypes, glycolate oxidase activities were significantly smaller in the NADP-malic enzyme grasses with low granal index in the BS chloroplasts, compared with in the C4 grasses with substantial grana in the BS chloroplasts. CONCLUSIONS: There is interspecies variation in glycolate oxidase activity associated with the granal development in the BS chloroplasts and the O2 production from photosystem II, which suggests different potential photorespiration capacities among C4 grasses. 相似文献
943.
944.
Mochizuki S Sipkema P Goto M Hiramatsu O Nakamoto H Toyota E Kajita T Shigeto F Yada T Ogasawara Y Kajiya F 《American journal of physiology. Heart and circulatory physiology》2005,288(2):H553-H558
Exogenous nitric oxide (NO) suppresses endothelium-derived NO production. We were interested in determining whether this is also the case in flow-induced endothelium-derived NO production. If so, then is the mechanism because of intracellular depletion of tetrahydrobiopterin [BH4; a cofactor of NO synthase (NOS)], which results in superoxide production by uncoupled NOS? Isolated canine femoral arteries were perfused with 100 microM S-nitroso-N-acetylpenicillamine (SNAP; an NO donor) and/or 64 microM BH4. Perfusion of SNAP suppressed flow-induced NO production, which was evaluated as a change in the slope of the linear relationship between perfusion rate and NO production rate (P < 0.02 vs. control; n = 7). Subsequent BH4 perfusion returned the slope to the control level. Concomitant perfusion of SNAP and BH4 retained the control-level NO production (n = 7). Concomitant perfusion of SNAP and 4,5-dihydroxy-1,3-benzene disulfonic acid (Tiron; 1 mM; a membrane-permeable superoxide scavenger) also retained the control-level NO production (n = 7), whereas perfusion of Tiron after SNAP could not return the NO production to the control level (P < 0.02 vs. control; n = 7). We also found a significant decrease in BH4 concentration in the endothelial cells after SNAP perfusion. In conclusion, these results indicate that exogenous NO suppresses the flow-induced, endothelium-derived NO production by superoxide released from uncoupled NOS because of intracellular BH4 depletion. 相似文献
945.
We investigated whether angiotensin II (AII) peptide is induced in the rat kidney under endotoxemic conditions. Immunohistochemistry revealed strong AII-like immunoreactivity in the renal tubules of rats given high-dose lipopolysaccharide (LPS; 1000 microg/kg) intraperitoneally (i.p.). AII-like immunoreactivity in renal tubules was slight at 1h after the LPS injection, but marked at 3 h. There were few signals in the kidney in saline-injected control rats. When injected at 0.1, 10, or 1000 microg/kg i.p., LPS-induced a dose-related increase in AII-like immunoreactivity in renal tubules that was unaffected by treatment with the prostaglandin-synthesis blocker indomethacin. ELISA measurement of the AII concentration in the whole kidney supported the above findings. These results suggest that systemically administered LPS induces AII peptide expression in renal tubules by a prostaglandin-independent mechanism. 相似文献
946.
Recently we discovered a bacterial strain (MS-02-063) that produces large amounts of red pigment from coastal area of Nagasaki Prefecture, Japan. Comparative 16S rDNA gene sequencing analysis revealed that strain MS-02-063 was phylogenetically closely related to gamma-proteobacterium Hahella sp. MBIC 3957 that produces prodigiosin. However, some physiological and biochemical differences between strain MS-02-063 and Hahella sp. MBIC 3957 were observed. The red pigment (RP-063) produced by this isolate was highly purified from the culture supernatant. It was speculated that RP-063 might be prodigiosin-like pigment in physical properties and biological activities such as antibacterial and cytotoxic activity. Antibacterial activity of RP-063 was examined by an agar dilution method. The results indicated that RP-063 showed antibacterial activity for specific for pathogenic gram-positive bacteria such as Staphylococcus aureus. The potency of antibacterial activity against S. aureus was nearly equal to those of tetracycline. Moreover, RP-063 showed inhibition of the superoxide generation by 12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated mouse macrophage RAW 264.7 cell line. Prodigiosin members have a wide variety of biological properties, including anticancer and antimalarial, etc. Especially, potent immunosuppressive properties have been reported for prodigiosin members with the mechanism of action different from that of the other well known immunosuppressors in atopic dermatitis therapy such as cyclosporin A, FK506 and rapamycin. It is suggested that RP-063 may be able to arrest the inflammation caused by superantigens secreted from S. aureus, which colonized skin on atopic dermatitis as well as suppression of activated lymphocyte proliferation and superoxide generation from leucocytes. 相似文献
947.
Matsubara M Basabose AK Omari I Kaleme K Kizungu B Sikubwabo K Kahindo M Yamagiwa J Takenaka O 《Primates; journal of primatology》2005,46(3):199-202
Methods for the identification of the sex and species of individuals from samples non-invasively taken from humans and gorillas were established. Amplification of a segment of amelogenin (AMG), which is an X–Y homologous gene, using two pairs of primers from human AMG, revealed both X- and Y-specific bands. The possibility of sex identification was examined by typing the AMG gene using hair and fecal samples from captive western lowland gorillas (Gorilla gorilla gorilla) in Japan and hair samples from wild eastern lowland gorillas (Gorilla beringei graueri) in the Kahuzi-Biega National Park, Democratic Republic of Congo, which were sexed by direct observation. Species-specific bands of AMG in gorillas and humans were identified by restriction fragment length polymorphisms analysis. These tests could be used for sexing unidentified individuals of wild western and eastern lowland gorillas, and screening contamination of human DNA from non-invasively acquired samples. 相似文献
948.
949.
950.