全文获取类型
收费全文 | 17390篇 |
免费 | 1239篇 |
国内免费 | 47篇 |
专业分类
18676篇 |
出版年
2024年 | 28篇 |
2023年 | 75篇 |
2022年 | 227篇 |
2021年 | 355篇 |
2020年 | 220篇 |
2019年 | 336篇 |
2018年 | 456篇 |
2017年 | 390篇 |
2016年 | 643篇 |
2015年 | 929篇 |
2014年 | 1072篇 |
2013年 | 1200篇 |
2012年 | 1520篇 |
2011年 | 1495篇 |
2010年 | 977篇 |
2009年 | 782篇 |
2008年 | 1132篇 |
2007年 | 1013篇 |
2006年 | 880篇 |
2005年 | 815篇 |
2004年 | 787篇 |
2003年 | 634篇 |
2002年 | 549篇 |
2001年 | 408篇 |
2000年 | 374篇 |
1999年 | 281篇 |
1998年 | 123篇 |
1997年 | 107篇 |
1996年 | 73篇 |
1995年 | 69篇 |
1994年 | 55篇 |
1993年 | 42篇 |
1992年 | 97篇 |
1991年 | 70篇 |
1990年 | 50篇 |
1989年 | 56篇 |
1988年 | 33篇 |
1987年 | 39篇 |
1986年 | 26篇 |
1985年 | 27篇 |
1984年 | 21篇 |
1983年 | 19篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 18篇 |
1975年 | 20篇 |
1974年 | 16篇 |
1968年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
Michael D. Jensen Ji?í Bajnárek Sang Yeoup Lee Soren Nielsen Christina Koutsari 《Journal of lipid research》2009,50(9):1863-1869
The relationship between overnight postabsorptive (fasting) respiratory exchange ratio (RER) and plasma FFA concentrations was addressed using data from three separate protocols, each of which involved careful control of the antecedent diet. Protocol 1 examined the relationship between fasting RER and the previous daytime RER. In Protocol 2 fasting, RER and plasma palmitate concentrations were measured in 29 women and 31 men (body mass index <30 kg·m−2). Protocol 3 analyzed data from Nielsen et al. (Nielsen, S., Z. K. Guo, J. B. Albu, S. Klein, P. C. O''Brien, M. D. Jensen. 2003. Energy expenditure, sex and endogenous fuel availability in humans. J. Clin. Invest. 111: 981-988.) to understand how fasting RER and palmitate concentrations relate within individuals during four consecutive measurements. The results were as follows: 1) Fasting RER was correlated (r = 0.74, P < 0.001) with the previous day''s average RER, and less so with RER variability. 2) Fasting RER was correlated (r = −0.39, P = 0.007) with fasting plasma palmitate concentrations. 3) The pattern of the RER/palmitate relationship was similar within individuals and between individuals; a negative slope was observed significantly more often than a positive slope (χ2 test; P < 0.001). Our findings suggest that, despite a fixed food quotient, the slight departures from energy equilibrium in a controlled General Clinical Research Center environment can effect plasma FFA concentrations. We suggest that including indirect calorimetry as part of FFA metabolism studies may aid in data interpretation. 相似文献
5.
6.
T Tobe S Minoshima S Yamase N H Choi M Tomita N Shimizu 《Cytogenetics and cell genetics》1991,57(4):193-195
SP-40,40 is a serum glycoprotein consisting of two different subunits (alpha and beta) assembled into a dimer by disulfide bonds. Northern blot hybridization, using total RNA from several cell lines, showed that SP-40,40 is expressed in glioblastoma and testicular tumor cells, as well as hepatoma cells. Spot blot hybridization of flow-sorted human chromosomes, using a SP-40,40 cDNA fragment as a probe, localized the gene for SP-40,40 to human chromosome 8. This gene has been given the designation CLI, for complement lysis inhibitor, by the Human Gene Nomenclature Committee. 相似文献
7.
8.
An NMR and nuclear Overhauser effect (NOE) analysis of Thermus thermophilus tRNAIle1a is presented. This species contains modifications including s2T54 and s4U8 [Horie, N., Hara-Yokoyama, M., Yokoyama, S., Watanabe, K., Kuchino, Y., Nishimura, S., & Miyazawa, T. (1985) Biochemistry 24, 5711-5715]. All the expected secondary and reverse Hoogsteen AU pairs were identified, with one possible exception. The general geometry of the T psi C loop is the same as the Escherichia coli species, and there is NOE evidence for an A9-UA12 triple. Preliminary measurements of solvent exchange rates of internally hydrogen-bonded bases suggest that this tRNA is more stable than previously studied E. coli and yeast tRNAs. 相似文献
9.
K. Choi M. D. Burow G. Church G. Burow A. H. Paterson C. E. Simpson J. L. Starr 《Journal of nematology》1999,31(3):283-290
Segregation of resistance to Meloidogyne arenaria in six BC₅F₂ peanut breeding populations was examined in greenhouse tests. Chi-square analysis indicated that segregation of resistance was consistent with resistance being conditioned by a single gene in three breeding populations (TP259-3, TP262-3, and TP271-2), whereas two resistance genes may be present in the breeding populations TP259-2, TP263-2, and TP268-3. Nematode development in clonally propagated lines of resistant individuals of TP262-3 and TP263-2 was compared to that of the susceptible cultivar Florunner. Juvenile nematodes readily penetrated roots of all peanut genotypes, but rate of development was slower (P = 0.05) in the resistant genotypes than in Florunner. Host cell necrosis indicative of a hypersensitive response was not consistently observed in resistant genotypes of either population. Three RFLP loci linked to resistance at distances of 4.2 to 11.0 centiMorgans were identified. Resistant and susceptible alleles for RFLP loci R2430E and R2545E were quite distinct and are useful for identifying individuals homozygous for resistance in segregating populations. 相似文献
10.
To investigate the mechanism of inclusion body formation and the effect of a hydrophobic sequence on the in vivo polypeptide folding, the aggregation caused by recombinant fusion beta-galactosidase in Escherichia coli was examined. Two plasmids were constructed: pTBG(H-) carried only the preS2 sequence of the hepatitis B virus surface antigen (HBsAg) in front of the beta-galactosidase gene (lacZ) while pTBG(H+) carried an additional sequence encoding the amino-terminal hydrophobic sequence of the S region of HBsAg between preS2 and lacZ. Unlike cells expressing the fusion protein not containing the hydrophobic sequence, E. coli JM109/pTBG(H+) exhibited temperature-sensitive production of beta-galactosidase. As the culture temperature increased the activity decreased dramatically. This decrease in activity was not due to a decrease in fusion polypeptide production, but rather the fusion polypeptides containing the hydrophobic sequence aggregated within the cells at high temperature. However once the fusion polypeptides folded into proper conformation at low temperature, they maintained the activity even at high temperature. The results indicate that aggregation is a consequence of incorrect folding and assembly of the polypeptides, and is not derived from the native structure. The aggregates of the pTBG(H+)-encoded fusion polypeptides did not revert to active form when the culture temperature was lowered. 相似文献