全文获取类型
收费全文 | 2545篇 |
免费 | 233篇 |
国内免费 | 222篇 |
专业分类
3000篇 |
出版年
2024年 | 7篇 |
2023年 | 33篇 |
2022年 | 69篇 |
2021年 | 129篇 |
2020年 | 97篇 |
2019年 | 115篇 |
2018年 | 106篇 |
2017年 | 81篇 |
2016年 | 115篇 |
2015年 | 140篇 |
2014年 | 182篇 |
2013年 | 190篇 |
2012年 | 210篇 |
2011年 | 168篇 |
2010年 | 115篇 |
2009年 | 126篇 |
2008年 | 127篇 |
2007年 | 123篇 |
2006年 | 98篇 |
2005年 | 73篇 |
2004年 | 91篇 |
2003年 | 93篇 |
2002年 | 87篇 |
2001年 | 67篇 |
2000年 | 39篇 |
1999年 | 37篇 |
1998年 | 25篇 |
1997年 | 21篇 |
1996年 | 25篇 |
1995年 | 15篇 |
1994年 | 33篇 |
1993年 | 14篇 |
1992年 | 33篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 17篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1975年 | 3篇 |
1969年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有3000条查询结果,搜索用时 0 毫秒
161.
In the present work the extent and variation of Zn, Cd, Pb, Cu, and Hg loading in undisturbed surface soil (0–5 cm) and the vertical transport of the metals in soil profiles are studied in the vicinity of a zinc smelter in Norway. Three major controlling factors on the metal concentrations in soil have been assessed: 1) distance from the anthropogenic point source; 2) organic matter content (O.M.); and 3) the prevailing wind directions. Moreover metal distributions in proximal soil profiles in 1972 and 2003 are compared. Current concentrations of Zn, Cd, Pb, Cu, and Hg in surface soil reach 14000, 60, 980, 430, and 7.0 mg·kg ? 1 , respectively, near the smelter and decrease regularly with distance in the northerly direction according to the regression model (y = ax? b ). The Zn concentrations are significantly different from the background range up to 30 km from the smelter, whereas the other metals approach background at only 10 km distance. Subsurface concentration peaks of Pb, Cu, and Hg are found at greater depth in soil profiles than peaks of Zn and Cd. Levels of Zn, Cd, and Pb in surface soil seem to have decreased from 1972 to 2003, whereas for Cu the levels appear not to be significantly different. 相似文献
162.
鸭茅是一种著名的温带牧草,容易感染锈病。本研究从植株感病率、感病严重度、病情指数和反应指数4方面对国内37份鸭茅种质资源(野生资源35份)进行锈病的病情调查及抗病性研究。研究初步揭示了鸭茅锈病的发病规律,研究结果显示02-106、02-107、90-130、02-115等4份材料对鸭茅锈病具有较好抗性,可作为育种材料进一步深入研究。 相似文献
163.
A simple phosphorescence method is proposed for quercetin detection based on Al3+-amplified room-temperature phosphorescence (RTP) signals of 3-mercaptopropionic acid (MPA)-capped Mn-doped ZnS quantum dots (QDs). The sensor was established based on some properties as follows. Al3+ can interact with carboxyl groups on the surface of MPA-capped Mn-doped ZnS QDs via chelation, which will lead to the aggregation of QDs and amplification of RTP signals, After the addition of quercetin, it can form more stable complex with Al3+ in alkaline aqueous solution and dissociate Al3+ from the surface of Mn-doped ZnS QDs, which will result in significant recovery of RTP intensity of the MPA-capped Mn-doped ZnS–Al3+ system. Under the optimized conditions, the change of RTP intensity was proportional to the concentration of quercetin in the range from 0.1 to 6.0 mg L−1, with a high correlation coefficient of 0.996 and a detection limit of 0.047 mg L−1. The proposed method is potentially suitable for detection of quercetin in real samples without complicated pretreatment. 相似文献
164.
The Role of Aquaporin RWC3 in Drought Avoidance in Rice 总被引:3,自引:0,他引:3
Lian Hong-Li; Yu Xin; Ye Qin; Ding Xiaodong; Kitagawa Yoshichika; Kwak Sang-Soo; Su Wei-Ai; Tang Zhang-Cheng 《Plant & cell physiology》2004,45(6):810
The above article appeared 相似文献
165.
166.
Yue Liu Songhua Xu Xiuli Lian Yang Su Yuhuan Zhong Ruimin Lv 《Cell cycle (Georgetown, Tex.)》2019,18(4):437-451
Zygotic genome activation (ZGA) is one of the most critical events at the beginning of mammalian preimplantation embryo development (PED). The mechanisms underlying mouse ZGA remain unclear although it has been widely studied. In the present study, we identified that tricho-rhino-phalangeal syndrome 1 (TRPS1), an atypical GATA family member, is an important factor for ZGA in mouse PED. We found that the Trps1 mRNA level peaked at the one-cell stage while TRPS1 protein did so at the two/four-cell stage. Knockdown of Trps1 by the microinjection of Trps1 siRNA reduced the developmental rate of mouse preimplantation embryos by approximately 30%, and increased the expression of ZGA marker genes MuERV-L and Zscan4d via suppressing the expression of major histone markers H3K4me3 and H3K27me3. Furthermore, Trps1 knockdown decreased the expression of Sox2 but increased Oct4 expression. We conclude that TRPS1 may be indispensable for zygotic genome activation during mouse PED. 相似文献
167.
168.
Four endemic Batrachospermaceae species in China, Batrachospermum hongdongense Xie & Feng, Batrachospermum longipedicellatum Hua & Shi, Kumanoa curvata (Shi) Vis et al., and Kumanoa intorta (Jao) Entwisle et al., were analyzed with multilocus data in order to assess their phylogenetic placement. Multilocus molecular data from one nuclear gene (the ribosomal SSU), one chloroplast gene (rbcL), and two mitochondrial genes (COI and the cox2-3 spacer) as well as morphological studies were used to determine the phylogenetic relationships of these endemic species within the Batrachospermales. Batrachospermum hongdongense and B. longipedicellatum had previously been placed in Batrachospermum section Batrachospermum, but based on the data from this study they should be transferred into section Helminthoidea. Kumanoa curvata and K. intorta clearly belong to the newly established genus Kumanoa. 相似文献
169.
Lu Gao Kejian Peng Yan Xia Guiping Wang Liyuan Niu Chunlan Lian 《International journal of phytoremediation》2013,15(4):307-319
Phytolacca americana L. can accumulate large amounts of heavy metals in its aerial tissues, especially cadmium (Cd) and manganese (Mn). It has great potential for use in phytoextraction of metals from multi-metal-contaminated soils. This study was conducted to further investigate the Cd- and Mn-tolerance strategies of this plant. Concentrations of non-protein thiols (NPTs) and phytochelatins (PCs) in leaves and roots increased significantly as the concentration of Cd in solution increased. The molar ratios of PCs:soluble Cd ranged from 1.8 to 3.6 in roots and 8.1 to 31.6 in leaves, suggesting that the cellular response involving PC synthesis was sufficient to complex Cd ions in the cytosol, especially that of leaves. In contrast, excess Mn treatments did not result in a significant increase in NPT or PC concentrations in leaves or roots. Oxalic acid concentrations in leaves of plants exposed to 2 or 20 mM Mn reached 69.4 to 89.3 mg (0.771 to 0.992 mmol) g–1 dry weight, respectively, which was approximately 3.7- to 8.6-fold higher than the Mn level in the 0.6 M HCl extract. Thus, oxalic acid may play an important role in the detoxification of Mn. 相似文献
170.