全文获取类型
收费全文 | 333210篇 |
免费 | 37226篇 |
国内免费 | 192篇 |
专业分类
370628篇 |
出版年
2018年 | 2844篇 |
2017年 | 2703篇 |
2016年 | 3880篇 |
2015年 | 5350篇 |
2014年 | 6245篇 |
2013年 | 8766篇 |
2012年 | 10008篇 |
2011年 | 9970篇 |
2010年 | 6808篇 |
2009年 | 6146篇 |
2008年 | 8876篇 |
2007年 | 9316篇 |
2006年 | 8609篇 |
2005年 | 8292篇 |
2004年 | 8030篇 |
2003年 | 7770篇 |
2002年 | 7786篇 |
2001年 | 18155篇 |
2000年 | 18390篇 |
1999年 | 14110篇 |
1998年 | 4228篇 |
1997年 | 4502篇 |
1996年 | 4305篇 |
1995年 | 4009篇 |
1994年 | 3945篇 |
1993年 | 3779篇 |
1992年 | 11484篇 |
1991年 | 11130篇 |
1990年 | 10680篇 |
1989年 | 10250篇 |
1988年 | 9488篇 |
1987年 | 8852篇 |
1986年 | 8089篇 |
1985年 | 7967篇 |
1984年 | 6391篇 |
1983年 | 5564篇 |
1982年 | 4109篇 |
1981年 | 3593篇 |
1980年 | 3358篇 |
1979年 | 6110篇 |
1978年 | 4577篇 |
1977年 | 4130篇 |
1976年 | 3764篇 |
1975年 | 4336篇 |
1974年 | 4504篇 |
1973年 | 4395篇 |
1972年 | 4094篇 |
1971年 | 3499篇 |
1970年 | 3172篇 |
1969年 | 2969篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
991.
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
992.
Administration of high-dose Antide to ovariectomized monkeys results in rapid, prolonged, and reversible inhibition of gonadotropin secretion. The present study examined whether similar long-term control would be manifested in the menstrual cycle of intact primates. Antide administration at a dose of either 3.0 or 18.0 mg/kg induced rapid suppression of bioassayable LH concentrations, precipitating a concurrent fall in serum progesterone concentrations from 7.9 +/- 3.6 and 5.8 +/- 1.0 ng/ml (mean +/- SEM) on the day of injection to 0.6 +/- 0.2 and 0.5 +/- 0.1 ng/ml by 2 days post-treatment, respectively. This Antide-induced luteolysis was accompanied by the premature onset of menses within 3 days. The next menses following Antide administration was delayed. Ultimately, folliculogenesis culminating in normal follicular-phase estradiol production, ovulation, and subsequent normal luteal-phase progesterone production did occur in all treated monkeys. Menses resumed 54 +/- 9 and 75 +/- 13 days after treatment with 3.0 and 18.0 mg/kg Antide, respectively. No allergic cutaneous or peripheral reactions were seen, even at the highest dose of Antide. Thus, the long duration of action of high-dose Antide reported earlier in ovariectomized monkeys is also demonstrated in intact primates. These findings, along with the apparent absence of histamine-release effects even at high doses, suggest that Antide is a GnRH antagonist deserving clinical evaluation. 相似文献
993.
994.
995.
996.
997.
L. Marklund M. Johansson U. Gustafsson L. Andersson A. K. Winterö M. Fredholm P. D. Thomsen 《Animal genetics》1993,24(5):333-338
Restriction fragment length polymorphisms (RFLPs) were described for the porcine loci for β-glucosidase (GBA) and the β-polypeptide 1 of the Na+, K+-transporting ATPase (ATP1B1). Linkage analyses using a three-generation pedigree provided evidence for the assignment of ATP1B1, GBA and two microsatellite loci (S0001 and S0067) to a previously described linkage group comprising the loci for blood group L (EAL) and an anonymous microsatellite (S0097). The linear order of the six markers was determined with confidence by multipoint analyses and the length of the linkage group was estimated at 88 CM. This linkage group was assigned to pig chromosome 4 on the basis of a previous physical localization of the ATP1B1 gene. In situ hybridization data for S0001 presented in this study were consistent with a localization on chromosome 4 and suggested a regional localization to 4pl2-pl3. The present study reveals conflicting data concerning the genetic localization of the K88 loci controlling the expression of the receptors for the E. coli pilus antigens. One group has reported data suggesting a loose linkage between K88 and EAL, now mapped to chromosome 4, whereas two other groups have found linkage between K88 and the transferrin locus (TF), mapped to chromosome 13 by in situ hybridization. 相似文献
998.
Abstract Monoclonal antibodies have been developed and used as specific probe to locate and identify a 29-kDa molecule of axenic Entamoeba histolytica trophozoites. Monoclonal antibody produced by clone C8 (MoAb C8) strongly agglutinated the amoebic trophozoites. THe immunofluorescence of live E. histolytica trophozoites and surface fluorescence of acetone-fixed trophozoites by MoAb C8 indicated existence of a 29-kDa molecule on surface-associated plasma membrane of E. histolytica . The monoclonal antibody belonged to IgG1 isotype. The prior treatment of E. histolytica trophozoites with MoAb C8 resulted in significant ( P < 0.01) reduction in adherence of amoebic trophozoites to cultured Chinese Hamster Ovary cells and significant ( P < 0.01) reduction in cytotoxicity to cultured Baby Hamster Kidney cells. Pretreatment of amoebic trophozoites with MoAb C8 prior to cultivation in TPS-1 medium resulted in significant ( P < 0.01) reduction in growth of the parasite. Thus, the data suggested that the surface-exposed 29-kDa molecule may be one of the receptors involved in E. histolytica host cell interactions and may possibly modulate amoebic disease processes. 相似文献
999.
Based on quantitative measurement of components of field resistance of potatoes to late blight, a multiple linear regression equation is derived for laboratory estimation of Area Under Disease Progress Curve. The equation accounts for 82% of variation in Area Under Disease Progress Curve. Transformation of data or inclusion of more terms do not improve the equation significantly. The method is suggested as a replacement or supplement to field testing. 相似文献
1000.
In vitro incubation of thymocytes with [2-14C]acetate results in a more intensive label incorporation into chromatin lipids as compared to nuclear lipids. The deleterious effect of gamma-irradiation leads to specific changes in [2-14C]acetate incorporation into the total fraction of phosphatidylcholine-phosphatidylserine and chromatin sphingomyelin. This is paralleled with an increase in the ratio of specific radioactivities of chromatin cardiolipin and nuclear cardiolipin. The changes in specific radioactivities of sphingomyelin, phosphatidylcholine-phosphatidylserine and cardiolipin suggest a role of phospholipids in the mechanisms of regulating the activity of intranuclear structures. 相似文献