全文获取类型
收费全文 | 6071篇 |
免费 | 374篇 |
国内免费 | 2篇 |
出版年
2023年 | 15篇 |
2022年 | 16篇 |
2021年 | 49篇 |
2020年 | 46篇 |
2019年 | 62篇 |
2018年 | 94篇 |
2017年 | 100篇 |
2016年 | 110篇 |
2015年 | 199篇 |
2014年 | 256篇 |
2013年 | 399篇 |
2012年 | 351篇 |
2011年 | 407篇 |
2010年 | 236篇 |
2009年 | 195篇 |
2008年 | 357篇 |
2007年 | 379篇 |
2006年 | 354篇 |
2005年 | 386篇 |
2004年 | 337篇 |
2003年 | 338篇 |
2002年 | 318篇 |
2001年 | 116篇 |
2000年 | 115篇 |
1999年 | 109篇 |
1998年 | 83篇 |
1997年 | 64篇 |
1996年 | 84篇 |
1995年 | 70篇 |
1994年 | 50篇 |
1993年 | 54篇 |
1992年 | 82篇 |
1991年 | 56篇 |
1990年 | 58篇 |
1989年 | 67篇 |
1988年 | 37篇 |
1987年 | 40篇 |
1986年 | 38篇 |
1985年 | 36篇 |
1984年 | 40篇 |
1983年 | 33篇 |
1982年 | 34篇 |
1981年 | 20篇 |
1980年 | 26篇 |
1979年 | 25篇 |
1978年 | 16篇 |
1976年 | 12篇 |
1975年 | 10篇 |
1974年 | 10篇 |
1973年 | 9篇 |
排序方式: 共有6447条查询结果,搜索用时 14 毫秒
1.
Abstract Clostridium perfringens alpha-toxin was produced in a protein-hyperproducing strain, Bacillus brevis 47, by cloning the gene into the constructed expression-secretion vector which has the multiple promoters and the signal peptide coding region of an outer cell wall protein gene. The amount of alpha-toxin produced by the B. brevis 47 transformant carrying the gene was approximately 10 times greater than that produced by a B. subtilis transformant carrying the toxin gene. Biological activities and the N-terminal amino acid sequence of the toxin secreted by the B. brevis 47 transformant were identical to those of wild-type alpha-toxin. 相似文献
2.
Kiyoto Takehara Shuya Yano Hiroshi Tazawa Hiroyuki Kishimoto Nobuhiro Narii Hiroyuki Mizuguchi 《Cell cycle (Georgetown, Tex.)》2017,16(16):1502-1508
Melanoma is a highly recalcitrant cancer and transformative therapy is necessary for the cure of this disease. We recently developed a telomerase-dependent adenovirus containing the fluorescent protein Killer-Red. In the present report, we first determined the efficacy of Killer-Red adenovirus combined with laser irradiation on human melanoma cell lines in vitro. Cell viability of human melanoma cells was reduced in a dose-dependent and irradiation-time-dependent manner. We used an intradermal xenografted melanoma model in nude mice to determine efficacy of the Killer-Red adenovirus. Intratumoral injection of Killer-Red adenovirus, combined with laser irradiation, eradicated the melanoma indicating the potential of a new paradigm of cancer therapy. 相似文献
3.
4.
Takahiro Watanabe Yohei Narita Masahiro Yoshida Yoshitaka Sato Fumi Goshima Hiroshi Kimura Takayuki Murata 《Journal of virology》2015,89(19):10120-10124
Epstein-Barr virus (EBV) is a gammaherpesvirus, associated with infectious mononucleosis and various types of malignancy. We focused here on the BDLF4 gene of EBV and identified it as a lytic gene, expressed with early kinetics. Viral late gene expression of the BDLF4 knockout strain was severely restricted; this could be restored by an exogenous supply of BDLF4. These results indicate that BDLF4 is important for the EBV lytic replication cycle, especially in late gene expression. 相似文献
5.
6.
The oxygen cost of transport per unit distance (CoT; mL·kg-1·km-1) shows a U-shaped curve as a function of walking speed (v), which includes a particular walking speed minimizing the CoT, so called economical speed (ES). The CoT-v relationship in running is approximately linear. These distinctive walking and running CoT-v relationships give an intersection between U-shaped and linear CoT relationships, termed the energetically optimal transition speed (EOTS). This study investigated the effects of subtracting the standing oxygen cost for calculating the CoT and its relevant effects on the ES and EOTS at the level and gradient slopes (±5%) in eleven male trained athletes. The percent effects of subtracting the standing oxygen cost (4.8 ± 0.4 mL·kg-1·min-1) on the CoT were significantly greater as the walking speed was slower, but it was not significant at faster running speeds over 9.4 km·h-1. The percent effect was significantly dependent on the gradient (downhill > level > uphill, P < 0.001). The net ES (level 4.09 ± 0.31, uphill 4.22 ± 0.37, and downhill 4.16 ± 0.44 km·h-1) was approximately 20% slower than the gross ES (level 5.15 ± 0.18, uphill 5.27 ± 0.20, and downhill 5.37 ± 0.22 km·h-1, P < 0.001). Both net and gross ES were not significantly dependent on the gradient. In contrast, the gross EOTS was slower than the net EOTS at the level (7.49 ± 0.32 vs. 7.63 ± 0.36 km·h-1, P = 0.003) and downhill gradients (7.78 ± 0.33 vs. 8.01 ± 0.41 km·h-1, P < 0.001), but not at the uphill gradient (7.55 ± 0.37 vs. 7.63 ± 0.51 km·h-1, P = 0.080). Note that those percent differences were less than 2.9%. Given these results, a subtraction of the standing oxygen cost should be carefully considered depending on the purpose of each study. 相似文献
7.
Temperature-gradient DNA probe chromatography of nucleic acids on a nonporous support with a homogeneous particle size of 2.5 microns showed a higher base sequence discriminating power and a larger linear capacity than that on a porous support with a larger and less homogeneous particle size. The resolution on the nonporous support was high enough to separate samples with a single-base mismatch of the less destabilizing groups, including G-G and G-T base mismatches, even when it locates very near the end of the probe. 相似文献
8.
Changes in Targeting Efficiencies of Proteins to Plant Microbodies Caused by Amino Acid Substitutions in the Carboxy-terminal Tripeptide 总被引:7,自引:0,他引:7
Hayashi Makoto; Aoki Masahiro; Kondo Maki; Nishimura Mikio 《Plant & cell physiology》1997,38(6):759-768
It has been demonstrated that the carboxyl terminus of microbodyenzymes functions as a targeting signal to microbodies in higherplants. We have examined an ability of 24 carboxy-terminal aminoacid sequences to facilitate the transport of a cytosolic passengerprotein, ß-glucuroni-dase, into microbodies in greencotyledonary cells of trans-genic Arabidopsis. Immunoelectronmicroscopic analysis revealed that carboxy-terminal tripeptidesequences of the form [C/A/S/P]-[K/R]-[I/L/M] function as amicrobody-targeting signal, although tripeptides with prolineat the first amino acid position and isoleucine at the carboxylterminus show weak targeting efficiencies. All known micro-bodyenzymes that are synthesized in a form similar in size to themature molecule, except catalase, contain one of these tripeptidesequences at their carboxyl terminus. (Received April 14, 1997; Accepted April 8, 1997) 相似文献
9.
Nobukazu Suganuma Satoru Ito Hiromichi Aso Masashi Kondo Mitsuo Sato Masahiro Sokabe Yoshinori Hasegawa 《PloS one》2012,7(9)
It is suggested that migration of airway smooth muscle (ASM) cells plays an important role in the pathogenesis of airway remodeling in asthma. Increases in intracellular Ca2+ concentrations ([Ca2+]i) regulate most ASM cell functions related to asthma, such as contraction and proliferation. Recently, STIM1 was identified as a sarcoplasmic reticulum (SR) Ca2+ sensor that activates Orai1, the Ca2+ channel responsible for store-operated Ca2+ entry (SOCE). We investigated the role of STIM1 in [Ca2+]i and cell migration induced by platelet-derived growth factor (PDGF)-BB in human ASM cells. Cell migration was assessed by a chemotaxis chamber assay. Human ASM cells express STIM1, STIM2, and Orai1 mRNAs. SOCE activated by thapsigargin, an inhibitor of SR Ca2+-ATPase, was significantly blocked by STIM1 siRNA and Orai1 siRNA but not by STIM2 siRNA. PDGF-BB induced a transient increase in [Ca2+]i followed by sustained [Ca2+]i elevation. Sustained increases in [Ca2+]i due to PDGF-BB were significantly inhibited by a Ca2+ chelating agent EGTA or by siRNA for STIM1 or Orai1. The numbers of migrating cells were significantly increased by PDGF-BB treatment for 6 h. Knockdown of STIM1 and Orai1 by siRNA transfection inhibited PDGF-induced cell migration. Similarly, EGTA significantly inhibited PDGF-induced cell migration. In contrast, transfection with siRNA for STIM2 did not inhibit the sustained elevation of [Ca2+]i or cell migration induced by PDGF-BB. These results demonstrate that STIM1 and Orai1 are essential for PDGF-induced cell migration and Ca2+ influx in human ASM cells. STIM1 could be an important molecule responsible for airway remodeling. 相似文献
10.