全文获取类型
收费全文 | 4885篇 |
免费 | 249篇 |
国内免费 | 523篇 |
出版年
2023年 | 56篇 |
2022年 | 78篇 |
2021年 | 106篇 |
2020年 | 99篇 |
2019年 | 151篇 |
2018年 | 168篇 |
2017年 | 112篇 |
2016年 | 130篇 |
2015年 | 114篇 |
2014年 | 263篇 |
2013年 | 282篇 |
2012年 | 199篇 |
2011年 | 277篇 |
2010年 | 212篇 |
2009年 | 208篇 |
2008年 | 240篇 |
2007年 | 225篇 |
2006年 | 211篇 |
2005年 | 209篇 |
2004年 | 156篇 |
2003年 | 158篇 |
2002年 | 129篇 |
2001年 | 119篇 |
2000年 | 92篇 |
1999年 | 77篇 |
1998年 | 79篇 |
1997年 | 78篇 |
1996年 | 79篇 |
1995年 | 62篇 |
1994年 | 65篇 |
1993年 | 76篇 |
1992年 | 72篇 |
1991年 | 67篇 |
1990年 | 72篇 |
1989年 | 59篇 |
1988年 | 53篇 |
1987年 | 57篇 |
1986年 | 33篇 |
1985年 | 59篇 |
1984年 | 103篇 |
1983年 | 76篇 |
1982年 | 90篇 |
1981年 | 76篇 |
1980年 | 64篇 |
1979年 | 65篇 |
1978年 | 35篇 |
1977年 | 45篇 |
1976年 | 32篇 |
1975年 | 28篇 |
1974年 | 25篇 |
排序方式: 共有5657条查询结果,搜索用时 15 毫秒
861.
Oxysterol‐binding protein recruitment and activity at the endoplasmic reticulum‐Golgi interface are independent of Sac1
下载免费PDF全文
![点击此处可从《Traffic (Copenhagen, Denmark)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Oxysterol‐binding protein (OSBP) localizes to endoplasmic reticulum (ER)‐Golgi contact sites where it transports cholesterol and phosphatidylinositol 4‐phosphate (PI‐4P), and activates lipid transport and biosynthetic activities. The PI‐4P phosphatase Sac1 cycles between the ER and Golgi apparatus where it potentially regulates OSBP activity. Here we examined whether the ER‐Golgi distribution of endogenous or ectopically expressed Sac1 influences OSBP activity. OSBP and Sac1 co‐localized at apparent ER‐Golgi contact sites in response to 25‐hydroxycholesterol (25OH), cholesterol depletion and p38 MAPK inhibitors. A Sac1 mutant that is unable to exit the ER did not localize with OSBP, suggesting that sterol perturbations cause Sac1 transport to the Golgi apparatus. Ectopic expression of Sac1 in the ER or Golgi apparatus, or Sac1 silencing, did not affect OSBP localization to ER‐Golgi contact sites, OSBP‐dependent activation of sphingomyelin synthesis, or cholesterol esterification in the ER. p38 MAPK inhibition and retention of Sac1 in the Golgi apparatus also caused OSBP phosphorylation and OSBP‐dependent activation of sphingomyelin synthesis at ER‐Golgi contacts. These results demonstrate that Sac1 expression in either the ER or Golgi apparatus has a minimal impact on the PI‐4P that regulates OSBP activity or recruitment to contact sites. 相似文献
862.
This work reports the photoluminescence properties of Ca3Mg3(PO4)4:Sm3+ phosphors that were synthesized by the combustion method. The phase formation and morphology of the prepared phosphors were analysed by X‐ray diffraction studies and scanning electron microscopy. Ca3Mg3(PO4)4:Sm3+ phosphors give orange light emission when excited by near‐ultraviolet (NUV) and blue light. The photoluminescence characteristics of the as‐prepared phosphors were investigated and their emission spectra showed three peaks due to 4G5/2 → 6H5/2, 4G5/2 → 6H7/2 and 4G5/2 → 6H9/2 transitions. The mechanism responsible for the concentration quenching of luminescence was found to be an electric dipole–dipole interaction. The CIE chromaticity coordinates suggested that the prepared phosphors are potential candidates for orange light‐emitting diodes (LEDs). 相似文献
863.
In this paper, the heavy metals (HMs) in the phosphate tailing-contaminated soil were detoxified using the microbial pretreatment in combination with electrokinetic remediation (EKR).. This study provides compelling evidence that the sequential usage of the bioleaching and electrokinetics is superior to the individual method for the detoxification of Pb, Cu, Zn, Cd, and As from the contaminated soil. In the sequential system, the detoxification efficiency of Zn was the highest and that of As was the lowest. Except the element As, the detoxification efficiencies of HMs in the sequential system were generally higher than that using the single biological treatment and EKR technique. Bioleaching, generation of the passivation, and migration direction of the ions are concluded as the factors attributable to the final results; and, the initial increase in the inoculation doping of Thiobacillus ferrooxidans considered has no obvious impact on improving the final detoxification efficiency rates. 相似文献
864.
865.
866.
施氮水平和收获时期对夏玉米产量和籽粒品质的影响 总被引:11,自引:1,他引:10
为明确黄淮海夏玉米适宜的施肥量和最佳收获时期,设计了5个氮肥水平(不施肥、113、181、249和375 kg N·hm-2)和2个收获时期(S1:9月23日,农民习惯收获时间;S2:9月29日,推迟6 d收获),研究施氮量和收获时期对夏玉米产量和品质的影响.结果表明:随施肥量增加,夏玉米穗粒数、千粒重和产量均增加,但差异不显著,其中施肥量在113~181 kg N·hm-2的玉米产量、氮素利用效率均相对较高;随施肥量增加,夏玉米蛋白质和赖氨酸含量增加,淀粉含量降低.与9月23日蜡熟期收获相比,9月29日完熟期收获的夏玉米籽粒千粒重、产量、淀粉和赖氨酸含量均增加,籽粒蛋白质和脂肪含量降低.依据产量水平,黄淮海高产夏玉米区适宜的施肥量在113~180 kg N·hm-2,最佳收获时期应推迟至9月29日-10月5日. 相似文献
867.
868.
Moist Exposed Burn Ointment (MEBO®) is widely used topical agent applied on skin burn. This study investigated the effect of MEBO topical application on activation and proliferation of epidermal stem cells through the immunohistochemical localization of cytokeratin 19 (CK19) as a known marker expressed in epidermal stem cells. Biopsies from normal skin and burn wounds were taken from 21 patients with partial thickness burn 1, 4, 7, 14, 21, and 28 days after treatment with MEBO. Tissue sections were prepared for histological study and for CK19 immunohistochemical localization. In control skin, only few cells showed a positive CK19 immune-reaction. Burned skin showed necrosis of full thickness epidermis that extended to dermis. Gradual regeneration of skin accompanied with an enhancement in CK19 immune-reactivity was noted 4, 7, 14 and 21 days after treatment with MEBO. On day 28, a complete regeneration of skin was observed with a return of CK19 immune-reactivity to the basal pattern again. In conclusion, the enhancement of epidermal stem cell marker CK19 after treatment of partial thickness burn injuries with MEBO suggested the role of MEBO in promoting epidermal stem cell activation and proliferation during burn wound healing. 相似文献
869.
Shin-ichi Sakasegawa Junji Hayashi Yoshiaki Ikura Shigeru Ueda Shigeyuki Imamura Toshihiko Kumazawa Atsuhisa Nishimura Toshihisa Ohshima Haruhiko Sakuraba 《Analytical biochemistry》2011,(1):61
Pyruvate phosphate dikinase (PPDK, EC 2.7.9.1) from the hyperthermophile Thermotoga maritima was biochemically characterized with the aim of establishing a colorimetric assay for inorganic pyrophosphate (PPi). When heterologously expressed in Escherichia coli, T. maritima PPDK (TmPPDK) was far more stable any other PPDK reported so far: it retained >90% of its activity after incubation for 1 h at 80 °C, and >80% of its activity after incubation for 20 min at pHs ranging from 6.5 to 10.5 (50 °C). In contrast to PPDKs from protozoa and plants, this TmPPDK showed very long-term stability at low temperature: full activity was retained even after storage for at least 2 years at 4 °C. TmPPDK was successfully applied to a novel colorimetric PPi assay, which employed (i) a PPi cycling reaction using TmPPDK and nicotinamide mononucleotide adenylyltransferase (EC 2.7.7.1) from Saccharomyces cerevisiae and (ii) a NAD cycling reaction to accumulate reduced nitroblue tetrazolium (diformazan). This enabled detection of 0.2 μM PPi, making this method applicable for preliminary measurement of PPi levels in PCR products in an automatic clinical analyzer. 相似文献
870.
Semprun-Prieto LC Sukhanov S Yoshida T Rezk BM Gonzalez-Villalobos RA Vaughn C Michael Tabony A Delafontaine P 《Biochemical and biophysical research communications》2011,(2):85-221
Angiotensin II (Ang II) causes skeletal muscle wasting via an increase in muscle catabolism. To determine whether the wasting effects of Ang II were related to its ability to increase NADPH oxidase-derived reactive oxygen species (ROS) we infused wild-type C57BL/6J or p47phox−/− mice with vehicle or Ang II for 7 days. Superoxide production was increased 2.4-fold in the skeletal muscle of Ang II infused mice, and this increase was prevented in p47phox−/− mice. Apocynin treatment prevented Ang II-induced superoxide production in skeletal muscle, consistent with Ang II increasing NADPH oxidase derived ROS. Ang II induced loss of body and skeletal muscle weight in C57BL/6J mice, whereas the reduction was significantly attenuated in p47phox−/− animals. The reduction of skeletal muscle weight caused by Ang II was associated with an increase of proteasome activity, and this increase was completely prevented in the skeletal muscle of p47phox−/− mice. In conclusion, Ang II-induced skeletal muscle wasting is in part dependent on NADPH oxidase derived ROS. 相似文献