全文获取类型
收费全文 | 811363篇 |
免费 | 89281篇 |
国内免费 | 559篇 |
专业分类
901203篇 |
出版年
2018年 | 7678篇 |
2017年 | 7200篇 |
2016年 | 10429篇 |
2015年 | 14392篇 |
2014年 | 16793篇 |
2013年 | 23802篇 |
2012年 | 26674篇 |
2011年 | 27039篇 |
2010年 | 18358篇 |
2009年 | 16700篇 |
2008年 | 23899篇 |
2007年 | 24492篇 |
2006年 | 23105篇 |
2005年 | 22273篇 |
2004年 | 22158篇 |
2003年 | 21279篇 |
2002年 | 20492篇 |
2001年 | 38417篇 |
2000年 | 38642篇 |
1999年 | 30694篇 |
1998年 | 10738篇 |
1997年 | 11235篇 |
1996年 | 10555篇 |
1995年 | 9851篇 |
1994年 | 9591篇 |
1993年 | 9373篇 |
1992年 | 24834篇 |
1991年 | 24074篇 |
1990年 | 23476篇 |
1989年 | 22837篇 |
1988年 | 21192篇 |
1987年 | 19805篇 |
1986年 | 18354篇 |
1985年 | 18190篇 |
1984年 | 15076篇 |
1983年 | 12571篇 |
1982年 | 9540篇 |
1981年 | 8519篇 |
1980年 | 7969篇 |
1979年 | 13519篇 |
1978年 | 10522篇 |
1977年 | 9465篇 |
1976年 | 8559篇 |
1975年 | 9530篇 |
1974年 | 10176篇 |
1973年 | 10060篇 |
1972年 | 8988篇 |
1971年 | 8199篇 |
1970年 | 7007篇 |
1969年 | 6767篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
In the red howler monkey, Alouatta seniculus stramineus (2n = 47, 48, or 49), variations in diploid chromosome number are due to different numbers of microchromosomes. Males exhibit a Y;autosome translocation involving the short arm of an individual biarmed autosome. Consequently, the sex-chromosome constitution in the male is X1X2Y1Y2, with X1 representing the original X chromosome, X2 the biarmed autosome (No. 7), Y1 the Y;7p translocation product, and Y2 the acrocentric homolog of 7q. In the first meiotic division, a quadrivalent with a chain configuration can be observed in spermatocytes. Females have an X1X1X2X2 sex-chromosome constitution. Chromosome heteromorphisms were observed in pair 13, due to a pericentric inversion, and pair 19, due to the presence of constitutive heterochromatin. Microchromosomes, which varied in number between individuals, were also heterochromatic. NOR-staining was observed at two separate sites on a single chromosome pair (No. 10). A comparison of A.s. stramineus with A.s. macconnelli shows that these two subspecies have identical diploid chromosome numbers (47, 48, or 49), again due to a varying number of microchromosomes, and that they share a similar sex-chromosome constitution. Their karyotypes, however, are not identical, but can be derived from each other by a reciprocal translocation. Further comparisons with other A. seniculus subspecies reported in the literature indicate that this taxon is not karyologically uniform and that substantial chromosome shuffling has occurred between populations that have been considered to be subspecies by taxonomic criteria based on their morphometric attributes. 相似文献
992.
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
993.
994.
995.
996.
997.
998.
M. L. Rabinovich 《Applied Biochemistry and Microbiology》2006,42(1):1-26
Development of national research of cellulose-degrading microorganisms and enzymes is reviewed, with emphasis on the prospects of producing ethanol from cellulose materials using cellulolytic enzymes. Leading Russian research groups in this field are introduced. A section of the review analyzes problems and prospects of setting up environmentally friendly production of motor biofuels from renewable raw materials of plant origin (an approach developed in Russia). 相似文献
999.
Y Midorikawa H Hibasami P Gasaluck H Yoshimura A Masuji K Nakashima M Imai 《The Journal of applied bacteriology》1991,70(4):291-293
Metabolic and antiproliferative effects of methylglyoxal bis(butylamidinohydrazone) (MGBB) and methylglyoxal bis(cyclopentylamidinohydrazone) (MGBCP), inhibitors for polyamine biosynthetic pathway, on Escherichia coli, Shigella sonnei, Aeromonas sobria, Aeromonas hydrophila and Vibrio cholerae were investigated. MGBB at the concentration of 100 mumol/l depleted intracellular putrescine and spermidine concentrations of E. coli to 25 and 20% of the controls, respectively, while MGBCP depressed their concentrations to 38 and 24%, respectively. In these polyamine-depleted E. coli cells the syntheses of RNA, DNA and protein decreased to 13, 54 and 29% of the control, respectively, with MGBB and to 23, 71 and 55%, respectively, with MGBCP. The minimum inhibitory concentrations (MIC) of MGBB for the growth of A. sobria, E. coli, A. hydrophila, V. cholerae and Sh. sonnei were estimated to be 50, 160, 240, 285 and 320 mumol/l, respectively, whereas those of MGBCP were slightly higher for respective bacteria. 相似文献
1000.
Recent reports suggest that prostaglandins, rather than cAMP, play a major role in mediating cholera toxin-induced water and electrolyte secretion from rabbit intestinal loops. We examined the role of prostaglandins in mediating toxin-induced pancreatic and gastric exocrine secretion. In these tissues, indomethacin, a potent inhibitor of prostaglandin synthesis, did not alter the stimulatory effects of cholera toxin on increases in cellular cAMP or enzyme secretion. Moreover, the addition of cholera toxin did not alter prostaglandin E2 release from either tissue. In contrast to their effects in rabbit intestinal loops, prostaglandins do not regulate cholera toxin-induced enzyme secretion from the guinea pig pancreas or stomach. 相似文献