全文获取类型
收费全文 | 139236篇 |
免费 | 3950篇 |
国内免费 | 4199篇 |
出版年
2024年 | 120篇 |
2023年 | 577篇 |
2022年 | 1375篇 |
2021年 | 2226篇 |
2020年 | 1519篇 |
2019年 | 1924篇 |
2018年 | 13529篇 |
2017年 | 12026篇 |
2016年 | 9407篇 |
2015年 | 3073篇 |
2014年 | 3487篇 |
2013年 | 3757篇 |
2012年 | 8049篇 |
2011年 | 16212篇 |
2010年 | 14377篇 |
2009年 | 10356篇 |
2008年 | 12263篇 |
2007年 | 13547篇 |
2006年 | 2310篇 |
2005年 | 2189篇 |
2004年 | 2537篇 |
2003年 | 2504篇 |
2002年 | 1992篇 |
2001年 | 1252篇 |
2000年 | 997篇 |
1999年 | 637篇 |
1998年 | 389篇 |
1997年 | 339篇 |
1996年 | 315篇 |
1995年 | 318篇 |
1994年 | 296篇 |
1993年 | 254篇 |
1992年 | 310篇 |
1991年 | 296篇 |
1990年 | 215篇 |
1989年 | 199篇 |
1988年 | 146篇 |
1987年 | 188篇 |
1986年 | 145篇 |
1985年 | 128篇 |
1984年 | 108篇 |
1983年 | 112篇 |
1982年 | 84篇 |
1981年 | 78篇 |
1980年 | 53篇 |
1979年 | 62篇 |
1978年 | 66篇 |
1973年 | 63篇 |
1972年 | 298篇 |
1971年 | 307篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
671.
Production of congenic mouse strains carrying genomic intervals containing SLE-susceptibility genes derived from the SLE-prone NZM2410 strain 总被引:12,自引:0,他引:12
Systemic lupus erythematosus is inherited as a complex polygenic trait. Four genomic intervals containing major SLE-susceptibility
loci were previously identified by interval mapping in the NZM2410 mouse model. In this paper, we utilized a marker-assisted
selection protocol to produce four congenic mouse strains, each carrying an NZM2410-derived SLE-susceptibility interval on
a C57BL/6-resistant background. Each strain carries only one susceptibility allele derived from this polygenic model and consequently
can be used to characterize the specific component phenotypes contributed by individual SLE-susceptibility genes. We illustrate
the efficacy of this approach with phenotypic data for one of our congenic strains, B6.NZMH2
z
. Our results indicate that this single genomic interval from Chromosome (Chr) 17 of NZM2410 can mediate increased levels of
IgG autoantibodies specific for chromatin and that, similar to results obtained in our original genetic cross, B6.NZMH2
z/b
heterozygotes are more prone than B6.NZMH2
z
homozygotes to the development of humoral autoimmunity to nuclear antigens. These results illustrate the feasibility of using
congenic strains to dissect the complex pathogenic mechanisms that mediate polygenic SLE. These congenic strains will be valuable
tools in the genetic analysis of SLE susceptibility. In future studies, these congenic strains will be interbred to produce
bi- and tri-congenic strains in order to assess the role of genetic interactions in the expression of specific components
of SLE pathogenesis. They will also be instrumental to the positional cloning and identification of the genes responsible
for SLE susceptibility, via the production of congenic recombinants.
Received: 1 September 1995 / Accepted: 20 December 1995 相似文献
672.
T. Hishinuma Grace S. P. Yu M. Takabatake Y. Nakagawa K. Ito M. Nishikawa M. Ishibashi K. Suzuki M. Matsumoto T. Toyoda M. Mizugaki 《Prostaglandins, leukotrienes, and essential fatty acids》1996,54(6):445-449
We microanalyzed 2,3-dinor-6-keto-prostaglandin F1α (2,3-dinor-6-keto-PGF1α 1) and 11-dehydrothromboxane B2 (11-dehydro-TXB2, 2) in human urine. Samples containing a [2H4]-analogue as an internal standard were extracted by chromatography using Sep Pak tC18 and silica gel. The compounds were then analysed by means of the lactone ring opening reaction and dimethylisopropylsilylation. The conversion of 1 to 1-methyl ester (ME)-propylamide (PA)-9,12,15-dimethylisopropylsilyl (DMIPS) ether derivative and of 2 to 1-ME-6-methoxime (MO)-9,12,15-tris-DMIPS ether derivative was followed by gas chromatography/selected ion monitoring (GC/SIM). Interfering substances from the urine matrix were eliminated during GC/SIM analysis using a DB-5 column. We were able to detect 1 (222–1031 pg/mg creatinine) and 2 (18–155 pg/mg creatinine) in human urine. Furthermore, the thromboxane/prostacyclin (IX/PGI) ratio in the urine of diabetics was higher than that of healthy volunteers. This method can be used to determine the TX/PGI balance in human urine. 相似文献
673.
A pentachlorophenol (PCP) degrading mixed culture contained three predominant strains identified as Flavobacterium gleum, Agrobacterium radiobacter and Pseudomonas sp. The relative abilities of the three strains to degrade PCP were tested individually and in combination. Rates of PCP degradation by individual isolates were lower than that observed for the three isolates combined. Of the individual strains, Flavobacterium gleum manifested highest PCP degradation ability. A biodegradation medium inoculated with a combination of the three isolates exhibited PCP degradation patterns similar to the original mixed culture. Varying low amounts of tetrachlorophenol were found in degradation medium inoculated with individual isolates, but this intermediate was absent from media inoculated with the mixed culture. 相似文献
674.
675.
本文对高原冻伤中血液循环障碍作形态计量,旨在探讨血循环障碍在冻伤过程中的变化及高原冻伤发病机理中所起的作用。实验选用Wistar雄性大鼠40只,随机分为平原冻伤组、急性低氧冻伤组和低氧习服冻伤组。习服组动物于低压舱内模拟海拔6000m缺氧每日4h,连续两周。其余动物常规饲养。习服期满次日习服组与低氧组一同进入舱内模拟海拔6000m低氧4h,再行冷冻。冻后继续低氧4h。冻后48h取材。对各组动物冻后48h冻肢皮下血管的病变作图象分析。结果发现,平原组血管淤滞、血栓绝对数及其百分比均为最低,习服组最高,低氧组居中。但低氧组与平原组的血栓/淤滞百分比无明显差别。骨骼肌坏死的面积百分比习服组显著高于低氧组与平原组,而后两组间无差别。血栓/淤滞百分比与骨骼肌坏死面积百分比之间的有高度相关关系。冻融是直接引起血管内皮损伤的原发因素,局部血液循环障碍是造成严重的继发损伤的主要原因。 相似文献
676.
贺兰山不同生境旱生灌木的解剖学研究 总被引:9,自引:1,他引:8
贺兰山荒漠地带三种不同基质生境的20种旱生灌木的营养器官的比较解剖学研究表明:其共同特点是叶片的表面积/体积的比值小,叶表具厚的角质层、表皮毛,气孔下陷、并具孔下室,叶向中栅栏组织发达;轴器官中木栓层细胞层数多,皮层较厚,机械组织发达,木薄壁组织及髓部细胞的细胞壁术化加厚,根内都具周皮、木质部的导管分子大小不一、频率较高。此外,根、茎、叶中普遍存在粘液细胞和草酸钙结晶,部分植物的根和茎内有异常维管组织。这些结构特征都与早生环境相关,而不同基质生境中生长的植物尚存在一定差异。 相似文献
677.
678.
679.
680.
湘鄂与闽粤猕猴颅骨的多变量分析 总被引:9,自引:1,他引:8
本文是中国猕猴湖南-湖北和广东-福建种群颅骨的多变量分析,结果表明,二者的面宽和颅肌的形态结构除有明显的性二型外,还存在较大的差异。湖南-湖北种群的颅骨结构相对大于福建广东种群。它们与云南南部和海南岛猕猴颅骨的判别分别结果表明,由于地理和生态隔离,四者雌雄两性颅骨的形态结构均有较大的差异,达到种群间的显著差异水平,分别应属不同的亚种。 相似文献