全文获取类型
收费全文 | 46464篇 |
免费 | 3871篇 |
国内免费 | 206篇 |
出版年
2018年 | 575篇 |
2017年 | 555篇 |
2016年 | 715篇 |
2015年 | 772篇 |
2014年 | 1005篇 |
2013年 | 1270篇 |
2012年 | 1632篇 |
2011年 | 1873篇 |
2010年 | 1121篇 |
2009年 | 936篇 |
2008年 | 1577篇 |
2007年 | 1546篇 |
2006年 | 1497篇 |
2005年 | 1299篇 |
2004年 | 1194篇 |
2003年 | 1135篇 |
2002年 | 1031篇 |
2001年 | 2831篇 |
2000年 | 2567篇 |
1999年 | 1855篇 |
1998年 | 651篇 |
1997年 | 537篇 |
1996年 | 481篇 |
1995年 | 416篇 |
1994年 | 393篇 |
1992年 | 1296篇 |
1991年 | 1172篇 |
1990年 | 1105篇 |
1989年 | 1055篇 |
1988年 | 938篇 |
1987年 | 939篇 |
1986年 | 810篇 |
1985年 | 811篇 |
1984年 | 585篇 |
1983年 | 519篇 |
1982年 | 380篇 |
1979年 | 645篇 |
1978年 | 464篇 |
1977年 | 423篇 |
1976年 | 386篇 |
1975年 | 506篇 |
1974年 | 592篇 |
1973年 | 562篇 |
1972年 | 578篇 |
1971年 | 560篇 |
1970年 | 529篇 |
1969年 | 529篇 |
1968年 | 432篇 |
1967年 | 382篇 |
1966年 | 411篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
The level of urine selenium in healthy adult population, 230 persons, was examined. Persons were selected regarding sex, ages, and smoking habits. No differences versus these observations have been found. For a total, group values are 16.96 Se nmol/creatinine mmol, SD=5.44. It is possible from a single-void specimen to express daily excretion of selenium. 相似文献
142.
S A Bitko L O Dynga A R Shikhman Z F Shmakova N I Briko 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1990,(4):3-7
The amino acid composition of cell walls and surface proteins, isolated from virulent (M+) and avirulent (M-) streptococcal strains (group A, type 29) has been determined by the method of E. H. Beachey et al. The kinetics of the lysis and proteolysis of streptococcal cell walls with muramidase and protease obtained from Actinomyces levoris and streptolysin has been studied. The constants describing the progress rates of these processes has been determined; their values in case of both lysis and proteolysis are higher in virulent strains than in avirulent ones. 相似文献
143.
Limitations associated with immunoglobulins have motivated the search for novel binding scaffolds. Repeat proteins have emerged as one promising class of scaffolds, but often are limited to binding protein and peptide targets. An exception is the repeat proteins of the immune system, which have in recent years served as an inspiration for binding scaffolds which can bind glycans and other classes of biomolecule. Like other repeat proteins, these proteins can be very stable and have a monomeric mode of binding, with elongated and highly variable binding surfaces. The ability to target glycans and glycoproteins fill an important gap in current tools for research and biomedical applications. 相似文献
144.
Z Naor 《Biochemical and biophysical research communications》1990,167(3):982-992
Addition of the stable and permeable analog 8-bromo cyclic GMP (8-BR-cGMP) to myo-[2-3H]inositol prelabeled cultured rat pituitary cells results in enhanced formation of [3H]-myo-inositol monophosphate (IP1). The stimulatory effect of the cyclic nucleotide analog is additive to the effect of Li+, which accumulates IP1 via inhibition of inositol 1-monophosphatase, and also to the effect of gonadotropin releasing hormone (GnRH) which stimulates the formation of IP1, as well as that of inositol 1,4-bisphosphate (IP2) and inositol 1,4,5-trisphosphate (IP3) via enhanced hydrolysis of polyphosphoinositides. Many Ca2(+)-mobilizing hormones acting via phosphoinosite turnover also stimulate cGMP formation. The cyclic nucleotide might then serve as a modulator by further hydrolysis of phosphoinositides needed for protein kinase C activation. 相似文献
145.
Neomorph and leaf differentiation as alternative morphogenetic pathways in soybean tissue culture. 总被引:1,自引:0,他引:1
Somatic embryogenesis and organogenesis were induced on immature cotyledons of different soybean cultivars. The anatomical investigation of morphogenesis proved neomorph differentiation instead of somatic embryos, and leaf formation instead of shoot development. While normal embryos were induced in 0-3.1% of the explants, neomorphs developed at a much higher rate i.e. in 10.5-78.9% depending on the genotype. Likewise organogenesis preferably followed the pathway of leaflet development (3.1-26.3%) than that of shoot tip formation (0-2.6%). Low plant regeneration frequency of soybean can partly be explained with these two alternative abortive pathways of morphogenesis probably induced with higher frequency than the normal pathways by the generally used in vitro methods. 相似文献
146.
Studies concerning metabolism of catecholamines in mice differing with respect to the degree of pigmentation were based on determination of daily excretion of vanillylmandelic and homovanillic acid and tissue content of epinephrine, norepinephrine, dopamine and their methoxy derivatives. It was found that pigmented mice excrete more homovanillic acid, the metabolite of dopamine, than do albinotic mice. Tissue studies have shown that the brain of albinotic mice contains more dopamine and kidneys more epinephrine, norepinephrine and their methoxy derivatives than the respective organs of the pigmented mice. The probable reasons of differences in the rate of inactivation of catecholamines in albinotic and pigmented mice have been discussed. 相似文献
147.
Restriction fragment length polymorphism (RFLP) was used as a molecular genotyping approach to characterize differences in major histocompatibility complex class IV genes in meat-type chickens. A high level of polymorphism was observed following digestion with each of the two restriction endonucleases PvuII and BglII. Examination of DNA from 54 chickens revealed 23 polymorphic fragments. Application of RFLP techniques in the analysis of family groups should make possible the determination of B-G genotypes in the meat type chickens. 相似文献
148.
An analysis is made of the general expression for the density of a nonlinear charge induced in a magnetized plasma in the interaction between two arbitrary waves. Asymptotic expressions for the nonlinear induced charge density are derived for the first time in the case where both of the interacting waves are short-scale. 相似文献
149.
150.