全文获取类型
收费全文 | 6087篇 |
免费 | 582篇 |
国内免费 | 650篇 |
专业分类
7319篇 |
出版年
2024年 | 23篇 |
2023年 | 93篇 |
2022年 | 236篇 |
2021年 | 336篇 |
2020年 | 239篇 |
2019年 | 291篇 |
2018年 | 290篇 |
2017年 | 226篇 |
2016年 | 275篇 |
2015年 | 409篇 |
2014年 | 457篇 |
2013年 | 455篇 |
2012年 | 594篇 |
2011年 | 506篇 |
2010年 | 308篇 |
2009年 | 311篇 |
2008年 | 304篇 |
2007年 | 277篇 |
2006年 | 211篇 |
2005年 | 224篇 |
2004年 | 227篇 |
2003年 | 180篇 |
2002年 | 152篇 |
2001年 | 119篇 |
2000年 | 96篇 |
1999年 | 81篇 |
1998年 | 68篇 |
1997年 | 54篇 |
1996年 | 39篇 |
1995年 | 29篇 |
1994年 | 36篇 |
1993年 | 29篇 |
1992年 | 39篇 |
1991年 | 34篇 |
1990年 | 15篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 10篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 1篇 |
排序方式: 共有7319条查询结果,搜索用时 15 毫秒
971.
The purpose of this paper was to investigate the possibility of developing a polymeric nanoparticle delivery system for ORI to increase its solubility, blood circulation time and tissue targeting. Oridonin-loaded poly(D,L-lactic acid) nanoparticles (ORI-PLA-NP) were prepared by the further modified spontaneous emulsion solvent diffusion (MSESD) method. Studies were carried out to characterize and evaluate the produced ORI-PLA-NP both in vitro and in vivo. The experimental results showed that the mean size of the nanoparticles were 137.3 nm, with 87.2% of the nanoparticles distributed between the range of 107 and 195 nm. The entrapment efficiency and actual drug loading of the nanoparticles were 91.88+/-1.83 and 2.32+/-0.05%, respectively. It was demonstrated by differential scanning calorimetry (DSC) and X-ray diffractometry (XRD) that ORI existed in the form of amorphous in the nanoparticles. The in vitro release profile of ORI-PLA-NP could be expressed well by the Higuchi equation: Q=8.944t(1/2)+11.246. The results of pharmacokinetics demonstrated that being encapsulated in PLA nanoparticles was remarkably effective for ORI to prolong its blood circulation time. After the i.v. administration of ORI-PLA-NP, we could observe a stable and high concentration of ORI in liver, lung and spleen, while its distribution in heart and kidney decreased. 相似文献
972.
Studies on the hemolytic activity of tentacle extracts of jellyfish Rhopilema esculentum Kishinouye: application of orthogonal test 总被引:5,自引:0,他引:5
Yu H Xing R Liu S Li C Guo Z Li P 《International journal of biological macromolecules》2007,40(3):276-280
The present work is first reporting the hemolytic activity of venom from jellyfish Rhopilema esculentum Kishinouye extracted by different phosphate buffer solutions and incubated at different temperature according to the orthogonal test L6(1) x 3(6). Of the seven controllable independent variables, incubated temperature and phenylmethylsulfonyl fluoride (PMSF) had strongest effect on the hemolytic activity. 相似文献
973.
Shi Q Hubbard GB Kushwaha RS Rainwater D Thomas CA Leland MM Vandeberg JL Wang XL 《American journal of physiology. Heart and circulatory physiology》2007,292(6):H2913-H2920
Increasing evidence indicates that replicative senescence and premature endothelial senescence could contribute to endothelial dysfunction. This study aims at testing the hypothesis that a high-fat diet may lead to premature vascular endothelial senescence in a nonhuman primate model. We isolated endothelial cells from left and right femoral arteries in 10 baboons before and after a 7-wk high-fat dietary treatment. We compared the morphological alterations, replicative capacities, and senescence-associated beta-galactosidase activities (SA-beta-gal) at these two time points. We found that high-fat diet increased the prevalence of endothelial senescence. Endothelial replicative capacities declined dramatically, and SA-beta-gal activities increased significantly in postdietary challenge. There was no change in telomeric length using quantitative flow fluorescence in situ hybridization analysis, suggesting that some stressors lead to cell senescence independent of telomere dysfunction. Our findings that high-fat diet causes endothelial damage through the premature senescence suggest a novel mechanism for the diet-induced endothelial dysfunction. 相似文献
974.
Mitochondrial rRNA and tRNA and hearing function 总被引:2,自引:0,他引:2
975.
The class A chitin synthase gene of Spodoptera exigua: molecular cloning and expression patterns 总被引:4,自引:0,他引:4
Chen X Yang X Senthil Kumar N Tang B Sun X Qiu X Hu J Zhang W 《Insect biochemistry and molecular biology》2007,37(5):409-417
Chitin synthase (CHS) is an important enzymatic component required for chitin formation in the cuticles and cuticular linings of other tissues. In the present study, a new CHS gene was characterized from the beet army worm Spodoptera exigua (Hübner) (Se). Homologous alignment and phylogenetic analysis of S. exigua CHS (SeCHS) with other related proteins suggest that SeCHS belongs to the class A CHS family (SeCHSA). Northern blot analysis revealed that SeCHSA is transcribed preferentially in the cuticle and tracheae. Further investigation indicated that SeCHSA mRNA is highly expressed in the early and late stages of each larval instar, and consistently expressed in high level during the pupal stage. Using antibody specific for CHS, SeCHS was further localized in the underlying epidermal cells of the integument and tracheal cells, but not in the fat body or Malpighian tubules. These data suggest that SeCHS plays an important role in cuticle formation and development of S. exigua. 相似文献
976.
977.
Xing J Koba S Kehoe V Gao Z Rice K King N Sinoway L Li J 《American journal of physiology. Heart and circulatory physiology》2007,293(2):H1190-H1195
During exercise, sympathetic nerve responses are accentuated in heart failure (HF), and this enhances norepinephrine (NE) release and evokes vasoconstriction. Two key pathophysiological responses could contribute to the greater NE release: 1) increased sympathetic nerve discharge and 2) increased NE in the neurovascular junction for a given level of sympathetic discharge. In this report, we focus on the second of these two general issues and test the following hypotheses: 1) in HF for a given level of sympathetic nerve stimulation, NE concentration in the interstitium (an index of neurovascular NE) would be greater, and 2) the greater interstitial NE concentration would be linked to reduced NE uptake. Studies were performed in rats 8-10 wk after induction of myocardial infarction (MI). Interstitial NE samples were collected from microdialysis probes inserted into the hindlimb muscle. Dialysate concentration of NE was determined by the HPLC method. First, interstitial NE concentration increased during electrical stimulation of the lumbar sympathetic nerves in eight control rats. An increase in interstitial NE concentration was significantly greater in 10 rats with severe MI. Additionally, an NE uptake-1 inhibitor (desipramine, 1 microM) was injected into the arterial blood supply of the muscle in six control and eight MI rats. Desipramine increased interstitial NE concentration by 24% in control and by only 3% (P < 0.05 vs. control) in MI rats. In conclusion, given levels of electrical stimulation of the lumbar sympathetic nerve lead to higher interstitial NE concentration in HF. This effect is due, in part, to reduced NE uptake-1 in HF. 相似文献
978.
Deng Biao Wang Xuan Long Xing Fang Ren Zhou Shuangyun Zhang Ji Peng Xiaolu An Zhenyu Huang Weixiong Tang Wenzhong Gao Yining Yao Jinyan 《Journal of Plant Growth Regulation》2022,41(6):2386-2405
Journal of Plant Growth Regulation - Gibberellin (GA), auxin (IAA) and brassinosteroid (BR) are indispensable in the process of plant growth and development. Currently, research on the regulatory... 相似文献
979.
Yan Gangli Tao Zhiwei Xing Xiaobing Zhou Ziying Wang Xinghua Li Xing Li Fengguang 《Neurochemical research》2022,47(5):1243-1254
Neurochemical Research - Hypoxic-ischemic brain damage (HIBD) is a familiar neurological disorder. Emerging reports manifest that microRNAs (miRs) are related to the progression of HIBD. The goal... 相似文献
980.
Tian Y.-S. Yao Q.-H. Xing X.-J. Peng R.-H. Xu J. Xiong A.-S. 《Applied Biochemistry and Microbiology》2015,51(5):566-571
Applied Biochemistry and Microbiology - To date, only aroA variants derived from Agrobacterium tumefaciens CP4 have been used to generate the commercial glyphosate-resistant crops currently... 相似文献