全文获取类型
收费全文 | 31324篇 |
免费 | 2354篇 |
国内免费 | 2285篇 |
专业分类
35963篇 |
出版年
2024年 | 65篇 |
2023年 | 437篇 |
2022年 | 1075篇 |
2021年 | 1760篇 |
2020年 | 1161篇 |
2019年 | 1562篇 |
2018年 | 1420篇 |
2017年 | 993篇 |
2016年 | 1431篇 |
2015年 | 1987篇 |
2014年 | 2381篇 |
2013年 | 2595篇 |
2012年 | 2836篇 |
2011年 | 2549篇 |
2010年 | 1492篇 |
2009年 | 1379篇 |
2008年 | 1619篇 |
2007年 | 1426篇 |
2006年 | 1168篇 |
2005年 | 913篇 |
2004年 | 759篇 |
2003年 | 716篇 |
2002年 | 545篇 |
2001年 | 486篇 |
2000年 | 460篇 |
1999年 | 429篇 |
1998年 | 266篇 |
1997年 | 255篇 |
1996年 | 253篇 |
1995年 | 229篇 |
1994年 | 218篇 |
1993年 | 150篇 |
1992年 | 199篇 |
1991年 | 179篇 |
1990年 | 126篇 |
1989年 | 99篇 |
1988年 | 81篇 |
1987年 | 69篇 |
1986年 | 39篇 |
1985年 | 44篇 |
1984年 | 24篇 |
1983年 | 30篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1973年 | 2篇 |
1957年 | 1篇 |
1954年 | 3篇 |
1944年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Determination of genetic relationships among five indigenous Chinese goat breeds with six microsatellite markers 总被引:16,自引:0,他引:16
Microsatellite variation was analyzed in five Chinese indigenous goat breeds, which include four Cashmere breeds (Tibetan, Neimonggol, Liaoning, Taihang) and one Hubei local breed (Matou) used for meat production. Five ovine and one bovine microsatellites, selected from eight ovine microsatellites and five bovine microsatellites were suitable for use in this study. With these six microsatellites, allele frequencies, heterozygosity, polymorphism information content (PIC) and effective allele number were calculated. A neighbor-joining tree was constructed using Nei's standard genetic distance (1978). In the tree, Neimonggol and Liaoning were grouped together, then with Taihang; while Tibetan and Matou individually had their own branch. The genetic relationship of five breeds corresponds to their history and geographic origins. 相似文献
52.
Julien Cappelle Delong Zhao Marius Gilbert Martha I. Nelson Scott H. Newman John Y. Takekawa Nicolas Gaidet Diann J. Prosser Ying Liu Peng Li Yuelong Shu Xiangming Xiao 《EcoHealth》2014,11(1):109-119
For decades, southern China has been considered to be an important source for emerging influenza viruses since key hosts live together in high densities in areas with intensive agriculture. However, the underlying conditions of emergence and spread of avian influenza viruses (AIV) have not been studied in detail, particularly the complex spatiotemporal interplay of viral transmission between wild and domestic ducks, two major actors of AIV epidemiology. In this synthesis, we examine the risks of avian influenza spread in Poyang Lake, an area of intensive free-ranging duck production and large numbers of wild waterfowl. Our synthesis shows that farming of free-grazing domestic ducks is intensive in this area and synchronized with wild duck migration. The presence of juvenile domestic ducks in harvested paddy fields prior to the arrival and departure of migrant ducks in the same fields may amplify the risk of AIV circulation and facilitate the transmission between wild and domestic populations. We provide evidence associating wild ducks migration with the spread of H5N1 in the spring of 2008 from southern China to South Korea, Russia, and Japan, supported by documented wild duck movements and phylogenetic analyses of highly pathogenic avian influenza H5N1 sequences. We suggest that prevention measures based on a modification of agricultural practices may be implemented in these areas to reduce the intensity of AIV transmission between wild and domestic ducks. This would require involving all local stakeholders to discuss feasible and acceptable solutions. 相似文献
53.
Kim CH Pennisi P Zhao H Yakar S Kaufman JB Iganaki K Shiloach J Scherer PE Quon MJ LeRoith D 《American journal of physiology. Endocrinology and metabolism》2006,291(2):E298-E305
Most rodent models of insulin resistance are accompanied by decreased circulating adiponectin levels. Adiponectin treatment improves the metabolic phenotype by increasing fatty acid oxidation in skeletal muscle and suppressing hepatic glucose production. Muscle IGF-I receptor (IGF-IR)-lysine-arginine (MKR) mice expressing dominant-negative mutant IGF-IRs in skeletal muscle are diabetic with insulin resistance in muscle, liver, and adipose tissue. Adiponectin levels are elevated in MKR mice, suggesting an unusual discordance between insulin resistance and adiponectin responsiveness. Therefore, we investigated the metabolic actions of adiponectin in MKR mice. MKR and ob/ob mice were treated both acutely (28 microg/g) and chronically (for 2 wk) with full-length adiponectin. Acute hypoglycemic effects of adiponectin were evident only in ob/ob mice but not in MKR mice. Chronic adiponectin treatment significantly improved both insulin sensitivity and glucose tolerance in ob/ob but not in MKR mice. Adiponectin receptor mRNA levels and adiponectin-stimulated phosphorylation of AMPK in skeletal muscle and liver were similar among MKR, wild-type, and ob/ob mice. Thus MKR mice are adiponectin resistant despite normal expression of adiponectin receptors and normal AMPK phosphorylation in muscle and liver. MKR mice may be a useful model for dissecting relationships between insulin resistance and adiponectin action in regulation of glucose homeostasis. 相似文献
54.
S. Wang F. Ding R. Zhao R. Li L. Zhang Y. Liu F. Gao L. Wang Y. Dai N. Li 《Theriogenology》2009,72(4):535-541
Introduction of selectable marker genes to transgenic animals could create an inconvenience to further research and may exaggerate public concerns regarding biological safety. The objective of the current study was to excise loxP flanked neoR in transgenic cloned cattle by transient expression of Cre recombinase. Green fluorescent protein gene (GFP) was incorporated to monitor Cre expression; therefore, Cre-expressed cells could be selected indirectly by fluorescence-activated cell sorting (FACS). The neoR was removed and Cre expressed transiently in GFP-positive colonies; excision of neoR was confirmed by single-blastocyst PCR in recloned blastocysts, with neoR-free fibroblast cells as donors. There was no difference (P > 0.05) in rates of cleavage (76.0% vs. 68.8%) or blastocyst formation (56.6% vs. 52.9%) between recloned embryos with neoR-free or neoR-included donors. The differential staining of recloned blastocysts were similar (P >0.05) in terms of total cell number (124 vs. 122) and the ratio of ICM (Inner Cell Mass) to the total cell number (38.1% vs. 38.2%). Furthermore, pregnancy and calving rates were not different (P > 0.05) from those of the control. In conclusion, we successfully excised neoR from transgenic cloned cattle; the manipulation did not affect the developmental competence of recloned preimplantation embryos. This approach should benefit bioreactor and transgenic research in livestock. 相似文献
55.
Zhou L Liu Q Wang Q Ma Y Xu Y Yang Z Zhao Y Zhang Y 《Applied microbiology and biotechnology》2008,79(6):1027-1034
To synthesize and secrete heterologous proteins in an attenuated Vibrio anguillarum strain for potential multivalent live vaccine development, different antigen-delivery systems based on bacterial-originated secretion signal peptides (SPs) were designed and identified in this work. Four SPs were derived from hemolysin of Escherichia coli, RTX protein of V. cholerae, hemolysin of V. anguillarum, zinc-metalloprotease of V. anguillarum, respectively, and their abilities to support secretion of green fluorescent protein (GFP) in an attenuated V. anguillarum strain MVAV6203 were assayed. Immunodetection of GFP showed that the capability of the tested signal leaders to direct secretion of GFP varied greatly. Although all the four signal peptide-fused GFPs could be expressed correctly and trapped intracellularly in recombinant strains, only the EmpA signal peptide could confer efficient secretion to GFP. For the investigation of its potential application in live bacteria carrier vaccines, a heterologous protein EseB of Edwardsiella tarda was fused to the SP(empA) antigen-delivery system and introduced into the strain MVAV6203. Further analysis of EseB demonstrated that the constructed SP(empA) antigen-delivery system could be used to secrete foreign protein in attenuated V. anguillarum and be available for carrier vaccines development. 相似文献
56.
57.
Lubiao Liang Ran Sui Yongxiang Song Yajin Zhao 《Acta biochimica et biophysica Sinica》2021,(11):1558-1566
Tumor acidic microenvironment is the main feature of many solid tumors.As a part of the tumor microenvironment,it has a profound impact on the occurrence and de... 相似文献
58.
Yuanyong Feng Xuedi Cao Bin Zhao Chunyan Song Baoxing Pang Liang Hu Chunmei Zhang Jinsong wang Junqi He Songlin wang 《中国科学:生命科学英文版》2021,(11):1810-1828
Although cisplatin is one of the chemotherapeutics most frequently used in oral squamous cell carcinoma (OSCC) treatment,it exerts multiple side effects and poo... 相似文献
59.
采用全基因分段合成和补丁连接相结合的方法构建了人甲状旁腺素 (hPTH) (1~ 34)肽基因 ,并利用GST融合表达系统 ,在大肠杆菌中克隆和可溶性表达了hPTH(1~ 34)肽基因。融合蛋白表达量占菌体总蛋白质的 2 5 %以上 ,经高密度发酵、亲和纯化后 ,在每升发酵液中得到了 10 g融合蛋白。融合蛋白经肠激酶一步加工并亲合纯化和反相脱盐后 ,最终可以得到约 0 .6g /L人甲状旁腺素 (1~ 34)肽纯品 ,样品的理论回收值达到了4 8.75 %。产物的纯度和性质经HPLC、毛细管电泳、质谱分析、N端测序等得到证明 ,并与化学合成产物的结果相吻合。兔肾皮质细胞测活表明 ,重组产物与化学合成人甲状旁腺素 (1~ 34)肽具有相近的腺苷酸环化酶激活活性。 相似文献
60.
Zhong J Chuang SC Bianchi R Zhao W Paul G Thakkar P Liu D Fenton AA Wong RK Tiedge H 《PloS one》2010,5(11):e15509