全文获取类型
收费全文 | 49362篇 |
免费 | 4000篇 |
国内免费 | 26篇 |
出版年
2023年 | 233篇 |
2021年 | 365篇 |
2020年 | 314篇 |
2019年 | 306篇 |
2018年 | 942篇 |
2017年 | 976篇 |
2016年 | 1063篇 |
2015年 | 1000篇 |
2014年 | 1219篇 |
2013年 | 2014篇 |
2012年 | 3345篇 |
2011年 | 3704篇 |
2010年 | 1948篇 |
2009年 | 1265篇 |
2008年 | 3037篇 |
2007年 | 3092篇 |
2006年 | 2895篇 |
2005年 | 2581篇 |
2004年 | 2490篇 |
2003年 | 2332篇 |
2002年 | 2331篇 |
2001年 | 1661篇 |
2000年 | 1924篇 |
1999年 | 1035篇 |
1998年 | 488篇 |
1997年 | 379篇 |
1996年 | 454篇 |
1995年 | 386篇 |
1994年 | 421篇 |
1993年 | 369篇 |
1992年 | 454篇 |
1991年 | 410篇 |
1990年 | 375篇 |
1989年 | 317篇 |
1988年 | 334篇 |
1987年 | 313篇 |
1986年 | 271篇 |
1985年 | 374篇 |
1984年 | 429篇 |
1983年 | 373篇 |
1982年 | 344篇 |
1981年 | 330篇 |
1980年 | 282篇 |
1979年 | 313篇 |
1978年 | 293篇 |
1977年 | 285篇 |
1976年 | 265篇 |
1975年 | 322篇 |
1974年 | 241篇 |
1973年 | 237篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Fazile Nur Ekinci Akdemir Berna Karagöz Recep Soslu Saleh H. Alwasel 《Journal of enzyme inhibition and medicinal chemistry》2016,31(6):114-118
AbstractThe antioxidant effects of ellagic acid (EA) and hesperidin (HES) against skeletal muscle ischemia/reperfusion injury (I/R) were performed. Hindlimb ischemia has been induced by tourniquet occlusion for 2?h on left hindlimb. At the end of ischemia, the tourniquate has been removed and initiated reperfusion for 2?h. EA (100?mg/kg) has been applied orally before ischemia/reperfusion in the EA?+?I/R group. HES (100?mg/kg) has been given orally in the HES?+?I/R group. The left gastrocnemius muscle has been harvested and stored immediately at??80?°C until assessed for the levels of MDA and antioxidant enzymes activities. MDA level has statistically increased in I/R group (p?<?0.05) compared to other groups. The muscle tissue antioxidant enzymes activities were lower than the other groups in the I/R group (p?<?0.05). EA and HES treatments significantly reversed the damage level in I/R, also activity of tissue SOD increased in the EA?+?I/R and HES?+?I/R groups. 相似文献
33.
34.
35.
Ohne ZusammenfassungProceedings of the Meetings of Saturday September 26, 1908.Die vorliegende Übersetzung, zu der Herr Prof. Went mich gütigst autorisierte, rechtfertigt sich durch die in theoretischer, ganz besonders aber in methodologischer Hinsicht überaus wichtigen Ergebnisse Blaauws. Die Untersuchung bestätigt zunächst ein Gesetz, das der Übersetzer für die Abhängigkeit der Präsentationszeit von der Lichtintensität festgestellt hat (die diesbezügliche Abhandlung war Herrn Prof. Went zur Zeit, als er dieses Referat schrieb, noch nicht zu Gesicht gekommen), verfolgt aber diese Gesetzmäßigkeit innerhalb wesentlich weiterer Grenzen. Die Feststellung ganz besonders, daß bei entsprechend intensiver Beleuchtung die Präsentationszeit bis auf 1/1000 Sekunde sinkt, zusammengehalten mit den Tatsachen der feinen Unterschiedsempfind-lichkeit der Pflanzen (Wiesner) und der außerordentlich kurzen Perzeptions-zeit (Fitting), muß die reizphysiologische Methodik reformieren und sie zu ebenso exaktem Arbeiten anspornen, wie es bei psychophysischen Experimenten längst der Fall ist. 相似文献
36.
New class I and II HLA alleles strongly associated with opposite patterns of progression to AIDS. 总被引:10,自引:0,他引:10
H Hendel S Caillat-Zucman H Lebuanec M Carrington S O'Brien J M Andrieu F Sch?chter D Zagury J Rappaport C Winkler G W Nelson J F Zagury 《Journal of immunology (Baltimore, Md. : 1950)》1999,162(11):6942-6946
The genetics of resistance to infection by HIV-1 cohort consists of 200 slow and 75 rapid progressors to AIDS corresponding to the extremes of HIV disease outcome of 20,000 Caucasians of European descent. A comprehensive analysis of HLA class I and class II genes in this highly informative cohort has identified HLA alleles associated with fast or slow progression, including several not described previously. A quantitative analysis shows an overall HLA influence independent of and equal in magnitude (for the protective effect) to the effect of the CCR5-Delta32 mutation. Among HLA class I genes, A29 (p = 0.001) and B22 (p < 0.0001) are significantly associated with rapid progression, whereas B14 (p = 0.001) and C8 (p = 0.004) are significantly associated with nonprogression. The class I alleles B27, B57, C14 (protective), and C16, as well as B35 (susceptible), are also influential, but their effects are less robust. Influence of class II alleles was only observed for DR11. These results confirm the influence of the immune system on disease progression and may have implications on peptide-based vaccine development. 相似文献
37.
38.
The speed and accuracy of protein synthesis are fundamental parameters for understanding the fitness of living cells, the quality control of translation, and the evolution of ribosomes. In this study, we analyse the speed and accuracy of the decoding step under conditions reproducing the high speed of translation in vivo. We show that error frequency is close to 10−3, consistent with the values measured in vivo. Selectivity is predominantly due to the differences in kcat values for cognate and near-cognate reactions, whereas the intrinsic affinity differences are not used for tRNA discrimination. Thus, the ribosome seems to be optimized towards high speed of translation at the cost of fidelity. Competition with near- and non-cognate ternary complexes reduces the rate of GTP hydrolysis in the cognate ternary complex, but does not appreciably affect the rate-limiting tRNA accommodation step. The GTP hydrolysis step is crucial for the optimization of both the speed and accuracy, which explains the necessity for the trade-off between the two fundamental parameters of translation. 相似文献
39.
A bacterial clone carrying sequences coding for elongation factor EF-1 alpha from Artemia 总被引:2,自引:0,他引:2
A bacterial cDNA clone was identified carrying one third of the nucleotides coding for elongation factor EF-1 alpha from the brine shrimp Artemia. The sequence of codons corresponds with the known sequence of amino acids of EF-1 alpha in the region involved. 相似文献
40.