全文获取类型
收费全文 | 21659篇 |
免费 | 1420篇 |
国内免费 | 9篇 |
出版年
2023年 | 191篇 |
2022年 | 372篇 |
2021年 | 682篇 |
2020年 | 502篇 |
2019年 | 592篇 |
2018年 | 803篇 |
2017年 | 678篇 |
2016年 | 920篇 |
2015年 | 1186篇 |
2014年 | 1323篇 |
2013年 | 1583篇 |
2012年 | 1665篇 |
2011年 | 1633篇 |
2010年 | 1002篇 |
2009年 | 906篇 |
2008年 | 1094篇 |
2007年 | 1113篇 |
2006年 | 976篇 |
2005年 | 821篇 |
2004年 | 732篇 |
2003年 | 638篇 |
2002年 | 564篇 |
2001年 | 364篇 |
2000年 | 337篇 |
1999年 | 275篇 |
1998年 | 152篇 |
1997年 | 98篇 |
1996年 | 102篇 |
1995年 | 110篇 |
1994年 | 98篇 |
1993年 | 68篇 |
1992年 | 141篇 |
1991年 | 138篇 |
1990年 | 101篇 |
1989年 | 103篇 |
1988年 | 97篇 |
1987年 | 90篇 |
1986年 | 85篇 |
1985年 | 65篇 |
1984年 | 70篇 |
1983年 | 52篇 |
1982年 | 44篇 |
1981年 | 42篇 |
1980年 | 37篇 |
1979年 | 48篇 |
1978年 | 42篇 |
1976年 | 30篇 |
1975年 | 41篇 |
1973年 | 30篇 |
1972年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Blanco Pablo J. Müller Lucas O. Watanabe Sansuke M. Feijóo Raúl A. 《Biomechanics and modeling in mechanobiology》2020,19(5):1663-1678
Biomechanics and Modeling in Mechanobiology - The goal of this work is to assess the impact of vascular anatomy definition degree in the predictions of blood flow models of the arterial network. To... 相似文献
22.
23.
Chromosome characterization in Acestrorhynchinae and Cynopotaminae (Pisces, Characidae) 总被引:1,自引:0,他引:1
The karyotypes of six species of Acestrorhynchinae ( Acestrorhynchus alus, A. lacustris, Oligosarcus hepsetus, O. jenynsii, O. macrolepis and O. pinloi ) and of one species of Cynopotaminae ( Galeocharax knerii ) were studied. The six Acestrorhynchinae species have 2 n = 50, while Galeocharax knerii has 2 n = 52 chromosomes. Some chromosomal characteristics were detected which permit establishing some karyotypic relationships among the different species investigated. Thus, among the Acestrorhynchinae, the four Oligosarcus species are relatively more related to one another than the two Acestrorhynchus species, at least with respect to the cytogenetic data considered. On the basis of the methods used, no sex chromosome heteromorphism was detected in the species for which a comparative study between male and female specimens was possible. 相似文献
24.
25.
A Soler C García del Río L García-Torres F Vargas A Martín-Andrés C Osorio 《Revista Espanola de Fisiología》1985,41(1):107-116
The effects of changes in arterial pressure and in circulating volume on Plasma Renin Activity (PRA) in the intact rat were compared by two experimental procedures. Gradual volume depletion was induced by intraperitoneal injection of a hyperoncotic polyethyleneglycol solution (PEG) in absence of acute changes in Systolic Arterial Pressure (SAP). SAP was measured in the conscious state by the tail cuff technique. Plasma Protein Concentration (PPC) and Hematocrit (Hct) increases after PEG injection were compared as the index for measuring the Plasma Volume Reduction (PVR). PRA showed a significant (p less than 0.001) linear relationship with PPC, suggesting a direct dependence of renin secretion on volume depletion. Acute changes in the circulating volume were induced by controlled hemorrhages of 5.0, 10.0, 15.0 and 20.0 ml of blood/kg body weight. The increase in PRA showed a significant relationship with the changes in circulating volume, but it did not show any dependence on the changes in Mean Arterial Pressure (MAP). Our results suggest that, in the intact and conscious rat, renin secretion responds to the information from the cardiopulmonary volume receptors rather than to that from the high pressure receptors. 相似文献
26.
27.
28.
Y. Saijo S. Takeda A. Scherer T. Kobayashi Y. Mada H. Taniguchi M. Yao S. Wakatsuki 《Protein science : a publication of the Protein Society》1997,6(4):916-918
Troponin is a ternary protein complex consisting of subunits TnC. TnI, and TnT, and plays a key role in calcium regulation of the skeletal and cardiac muscle contraction. In the present study, a partial complex (CI47) was prepared from Escherichia coli-expressed rabbit skeletal muscle TnC and fragment 1-47 of TnI, which is obtained by chemical cleavage of an E. coli-expressed mutant of rabbit skeletal muscle TnI. Within the ternary troponin complex, CI47 is thought to form a core that is resistant to proteolytic digestion, and the interaction within CI47 likely maintains the integrity of the troponin complex. Complex CI47 was crystallized in the presence of sodium citrate. The addition of trehalose improved the diffraction pattern of the crystals substantially. The crystal lattice belongs to the space group P3(1)(2)21, with unit cell dimensions a = b = 48.2 A, c = 162 A. The asymmetric unit presumably contains one CI47 complex. Soaking with p-chloromercuribenzenesulfonate (PCMBS) resulted in loss of isomorphism, but enhanced the quality of the crystals. The crystals diffracted up to 2.3 A resolution, with completeness of 91% and R(merge) = 6.4%. The crystals of PCMBS-derivative should be suitable for X-ray studies using the multiple-wavelength anomalous diffraction technique. This is the first step for elucidating the structure of the full troponin complex. 相似文献
29.
Jesus Torres-Bacete Prem Kumar Sinha Motoaki Sato Gaurav Patki Mou-Chieh Kao Akemi Matsuno-Yagi Takao Yagi 《The Journal of biological chemistry》2012,287(51):42763-42772
The bacterial H+-translocating NADH:quinone oxidoreductase (NDH-1) catalyzes electron transfer from NADH to quinone coupled with proton pumping across the cytoplasmic membrane. The NuoK subunit (counterpart of the mitochondrial ND4L subunit) is one of the seven hydrophobic subunits in the membrane domain and bears three transmembrane segments (TM1–3). Two glutamic residues located in the adjacent transmembrane helices of NuoK are important for the energy coupled activity of NDH-1. In particular, mutation of the highly conserved carboxyl residue (KGlu-36 in TM2) to Ala led to a complete loss of the NDH-1 activities. Mutation of the second conserved carboxyl residue (KGlu-72 in TM3) moderately reduced the activities. To clarify the contribution of NuoK to the mechanism of proton translocation, we relocated these two conserved residues. When we shifted KGlu-36 along TM2 to positions 32, 38, 39, and 40, the mutants largely retained energy transducing NDH-1 activities. According to the recent structural information, these positions are located in the vicinity of KGlu-36, present in the same helix phase, in an immediately before and after helix turn. In an earlier study, a double mutation of two arginine residues located in a short cytoplasmic loop between TM1 and TM2 (loop-1) showed a drastic effect on energy transducing activities. Therefore, the importance of this cytosolic loop of NuoK (KArg-25, KArg-26, and KAsn-27) for the energy transducing activities was extensively studied. The probable roles of subunit NuoK in the energy transducing mechanism of NDH-1 are discussed. 相似文献
30.
Rocío García-Pérez Beatriz Revilla-Nuin Carlos M. Martínez Angel Bernabé-García Alberto Baroja Mazo Pascual Parrilla Paricio 《PloS one》2015,10(12)
Associated liver partition and portal vein ligation for staged hepatectomy (ALPPS) is a two-stage hepatectomy technique which can be associated with a hypertrophic stimulus on the future liver remnant (FLR) stronger than other techniques–such as portal vein ligation (PVL). However, the reason of such hypertrophy is still unclear, but it is suggested that liver transection combined with portal vein ligation (ALPPS) during the first stage of this technique may play a key role. The aim of this study is to compare the hypertrophic stimulus on the FLR and the clinical changes associated with both ALPPS and PVL in a rat surgical model. For this purpose, three groups of SD rats were used, namely ALPPS (n = 30), PVL (n = 30) and sham-treated (n = 30). The second stage of ALPPS (hepatectomy of the atrophic lobes), was performed at day 8. Blood and FLR samples were collected at 1, 24, 48 hours, 8 days and 12 weeks after the surgeries. ALPPS provoked a greater degree of hypertrophy of the FLR than the PVL at 48 hours and 8 days (p<0.05). The molecular pattern was also different, with the highest expression of IL-1β at 24h, IL-6 at 8 days, and HGF and TNF-α at 48 hours and 8 days (p<0.05). ALPPS also brought about a mild proliferative stimulus at 12 weeks, with a higher expression of HGF and TGF-β (p<0.05) than PVL. Clinically, ALPPS caused a significant liver damage during the first 48 hours, with a recovery of liver function at day 8. In conclusion, ALPPS seems to induce higher functional hypertrophy on the FLR than PVL at day 8. Such regenerative response seems to be leaded by a complex interaction between pro-mitogenic (IL-6, HGF, TNF-α) and antiproliferative (IL1-β and TGF-β) cytokines. 相似文献