全文获取类型
收费全文 | 3536篇 |
免费 | 249篇 |
国内免费 | 268篇 |
出版年
2024年 | 6篇 |
2023年 | 36篇 |
2022年 | 62篇 |
2021年 | 189篇 |
2020年 | 131篇 |
2019年 | 160篇 |
2018年 | 168篇 |
2017年 | 106篇 |
2016年 | 144篇 |
2015年 | 199篇 |
2014年 | 274篇 |
2013年 | 271篇 |
2012年 | 345篇 |
2011年 | 292篇 |
2010年 | 174篇 |
2009年 | 153篇 |
2008年 | 183篇 |
2007年 | 133篇 |
2006年 | 132篇 |
2005年 | 106篇 |
2004年 | 82篇 |
2003年 | 97篇 |
2002年 | 78篇 |
2001年 | 42篇 |
2000年 | 56篇 |
1999年 | 66篇 |
1998年 | 37篇 |
1997年 | 32篇 |
1996年 | 24篇 |
1995年 | 30篇 |
1994年 | 28篇 |
1993年 | 22篇 |
1992年 | 32篇 |
1991年 | 25篇 |
1990年 | 23篇 |
1989年 | 19篇 |
1988年 | 15篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1976年 | 3篇 |
1973年 | 2篇 |
1969年 | 3篇 |
1966年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有4053条查询结果,搜索用时 99 毫秒
991.
Jun-ling Shen Xiang-nan Jia Hui-qun Ni Pei-guang Sun Shi-hui Niu Xiao-yang Chen 《Trees - Structure and Function》2010,24(3):455-462
Amplified fragment length polymorphism (AFLP) was used to determine the genetic diversity among 38 populations of Jatropha curcas L. grown in a seed source trial in Hainan Province of China. The populations studied consisted of one source from Indonesia
and 37 sources from the main cultivating areas of jatropha in China, viz. Guangdong (1), Guangxi (10), Guizhou (4), Hainan
(6), Sichuan (8) and Yunnan (8). Nine AFLP primer combinations were used to generate a total of 246 fragments, of which 72
(26.99%) were polymorphic. Three-marker attributes: polymorphism information content (PIC), marker index (MI) and resolving
power (RP), were all found to be reliable to determine the discriminatory power of the nine primer combinations. The Jaccard’s
similarity coefficient showed a high similarity range from 0.866 to 0.977, suggesting a low genetic diversity among the 38
populations. The UPGMA-based dendrogram and biplot of a principal component analysis did not reveal a clear pattern of groupings
by geographic locations of the seed sources; populations from across different provinces were mixing in the same groups. The
low genetic diversity and a lack of variation pattern among the populations in China suggest that it is necessary to import
new germplasm preferably from the species’ natural distribution range to broaden the genetic base for improvement program. 相似文献
992.
The electrochemical behaviors of the interaction of chromotrope 2R (CH2R) with human serum albumin (HSA) are investigated
on the hanging mercury drop electrode with linear sweep voltammetry. In the acidic buffer solution (pH 2.5) CH2R has a well-defined
voltammetric reductive wave at −0.34 V (SCE). On the addition of HSA into the CH2R solution, the reductive peak current of
CH2R decreases with little movement of the peak potential. The voltammetric study shows that the electrochemical parameters
of interaction solution do not change and a new electrochemically non-active complex is formed via interaction of CH2R with
HSA, which cannot be reduced on the Hg electrode and results in the decrease of the free concentration of CH2R. The decrease
of reductive peak current is proportional to HSA concentration and further used for protein detection. The binding ratio and
the binding constant are further calculated with the experimental voltammetric data. 相似文献
993.
994.
Shun-rong Ji Chen Liu Bo Zhang Feng Yang Jin Xu Jiang Long Chen Jin De-liang Fu Quan-xing Ni Xian-jun Yu 《生物化学与生物物理学报:癌评论》2010
During the past years, great progress has been made in the field of nanomaterials given their great potential in biomedical applications. Carbon nanotubes (CNTs), due to their unique physicochemical properties, have become a popular tool in cancer diagnosis and therapy. They are considered one of the most promising nanomaterials with the capability of both detecting the cancerous cells and delivering drugs or small therapeutic molecules to these cells. Over the last several years, CNTs have been explored in almost every single cancer treatment modality, including drug delivery, lymphatic targeted chemotherapy, thermal therapy, photodynamic therapy, and gene therapy. In this review, we will show how they have been introduced into the diagnosis and treatment of cancer. Novel SWNT-based tumor-targeted drug delivery systems (DDS) will be highlighted. Furthermore, the in vitro and in vivo toxicity of CNTs reported in recent years will be summarized. 相似文献
995.
996.
997.
为探讨群居型西藏飞蝗Locusta migratoria tibetensis Chen地理种群数量性状关系,从青藏高原9个地区采集到不同地理种群,以数值分析对形态指标及其比值进行了分析。结果表明,前翅长度(E)、后足股节长度(F)、头宽(C)形态指标和E/F、F/C两个比值可以作为分析种群关系的参数。聚类分析和主成分分析结果相似,能够较好地说明青藏高原9个种群的地理变异和种群相互关系,9个地理种群可以分三个类群,即第Ⅰ类群包括百巴(BB)与八美(BM)种群;第Ⅱ类群包括普兰(PL)、扎囊(ZN)、洛须(LX)种群;第Ⅲ类群包括噶尔(GE)、香孜(XZ)、日土(RT)、那嘎(NG)种群。 相似文献
998.
SRC-3与乳腺癌的关系研究进展 总被引:1,自引:0,他引:1
类固醇受体辅助活化因子-3(SRC-3)是p160类固醇受体辅助活化因子SRC基因家族的成员,与体内多种肿瘤的形成密切相关。SRC-3不仅可以通过多种信号转导通路参与乳腺癌的发生,还与部分乳腺癌患者产生内分泌药物治疗抵抗的分子机制有关。临床治疗研究中发现,SRC-3和人表皮生长因子受体-2的共同过度表达常预示着乳腺癌患者较差的生存率。因此,SRC-3有望成为抗癌治疗的新靶点,解决目前内分泌治疗的药物抵抗问题,给更多乳腺癌患者带来福音。 相似文献
999.
David Chiu Lizhi Niu Feng Mu Xiang Peng Liang Zhou Haibo Li Rongrong Li Jiazhang Ni Ningzi Jiang Yize Hu Zuofang Hao Kecheng Xu 《Cryobiology》2010,60(3):281-286
Objective: This study was designed to basic information concerning the efficacy and safety of cryosurgery for pancreatic cancer. Fifteen healthy pigs were used to perform biochemical analysis and histological assessment. Methods: Following anesthesia and laparotomy, an argon–helium cryoprobe was inserted into the pancreas. The introduction of argon gas induced a rapid decrease in temperature to ?160 °C (Group I, 5 pigs) or ?110 °C (Group II, 5 pigs), respectively, resulting in ice-ball formation of 15–20 mm diameter after 5 min. Following freezing, helium gas was circulated in the probe tip to increase the temperature to 10–20 °C over 3 min to thaw. The freeze/thaw cycle was then repeated. Group III (3 pigs) had a cryoprobe inserted, but without freezing, and Group IV (2 pigs) included untreated or normal control animals. Levels of serum amylase (AMY), IL-6 and C-RP were measured prior to freezing and for 7 days following the procedure. All pigs were euthanized 7 days post-treatment and pancreases were examined histologically. Results: Neither hyperaemia, edema or hemorrhage were observed in the un-frozen parts of the pancreas. Histological assessment revealed a significant level of necrosis in the central and lateral regions of the tissue frozen within the ice-ball. All cellular ultrastructure was destroyed and only observable as a few of remaining nuclei with broken crests and degranulated mitochondria and rough endoplasmic reticulum. There was a significant increase of serum AMY levels for a brief period in both “deep frozen” and the “shallow frozen” groups. However, the AMY also increased in two pigs in the “normal control” group and one pig from the “inserted cryoprobe without freeze” control group. All experimental pigs appeared healthy until the sacrifice time. Conclusion: Cryosurgery is a safe and effective ablative procedure for pancreatic tissue resulting in minimal complications. 相似文献
1000.