全文获取类型
收费全文 | 9593篇 |
免费 | 1965篇 |
国内免费 | 2820篇 |
专业分类
测绘学 | 998篇 |
大气科学 | 1761篇 |
地球物理 | 2293篇 |
地质学 | 5150篇 |
海洋学 | 1550篇 |
天文学 | 274篇 |
综合类 | 1002篇 |
自然地理 | 1350篇 |
出版年
2024年 | 46篇 |
2023年 | 170篇 |
2022年 | 500篇 |
2021年 | 573篇 |
2020年 | 448篇 |
2019年 | 538篇 |
2018年 | 587篇 |
2017年 | 589篇 |
2016年 | 650篇 |
2015年 | 574篇 |
2014年 | 705篇 |
2013年 | 667篇 |
2012年 | 699篇 |
2011年 | 712篇 |
2010年 | 770篇 |
2009年 | 647篇 |
2008年 | 610篇 |
2007年 | 534篇 |
2006年 | 473篇 |
2005年 | 374篇 |
2004年 | 322篇 |
2003年 | 323篇 |
2002年 | 364篇 |
2001年 | 347篇 |
2000年 | 263篇 |
1999年 | 314篇 |
1998年 | 231篇 |
1997年 | 234篇 |
1996年 | 164篇 |
1995年 | 169篇 |
1994年 | 153篇 |
1993年 | 154篇 |
1992年 | 101篇 |
1991年 | 66篇 |
1990年 | 52篇 |
1989年 | 47篇 |
1988年 | 54篇 |
1987年 | 30篇 |
1986年 | 24篇 |
1985年 | 19篇 |
1984年 | 15篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1980年 | 15篇 |
1979年 | 4篇 |
1976年 | 2篇 |
1958年 | 6篇 |
1957年 | 1篇 |
1954年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
ͨ������������Ⱥ�㷨���ݻ�ϲ��˶� 总被引:1,自引:0,他引:1
???????????2002??2003???2004??2005??????????????????????????????????????????????????????????????????Ч?????????????????????????????????????????????????????????????????????????????????????????????????? 相似文献
992.
利用冀鲁豫测网的流动重力5期观测成果,探讨了重力场变化与封丘地震的关系。研究发现:冀鲁豫交界地区的重力点值在封丘地震前后出现了下降-上升-下降的变化过程,较好地对应了封丘ML4.8地震孕育 发震 震后调整的过程。该重力变化可能是封丘地震的异常反映。 相似文献
993.
�봨8.0������ǰ��ؿǴ�ֱ�α���� 总被引:5,自引:0,他引:5
??????8.0?????????????????????????????????????Ms8.0?????????????α????????:???????????α???????????????????????????????????仯???????????????????????????????????????????????????????????????????????????????α??????? 相似文献
994.
YAN Mingyan LI Bafang ZHAO Xue College of Food Science Engineering Ocean University of China Qingdao P. R. China 《中国海洋大学学报(英文版)》2009,(2)
Collagen of squid(Ommastrephes bartrami) skin was examined in the present study. Histology showed that collagen fiber in the skin was partially cross-linked with muscle fiber. Acid-solubilized collagen(ASC) and pepsin-solubilized collagen(PSC) were extracted from the skin and characterized. The results of amino acid composition and electrophoretic patterns revealed that ASC and PSC were both type Ⅰ collagen,containing α1 and α2 chains. FTIR(fourier transform infrared spectroscopy) investigations confirmed t... 相似文献
995.
温度对管角螺Hemifusus tuba(Gelin)耗氧率和排氨率的影响 总被引:1,自引:0,他引:1
设置5个温度梯度(14、19、24、29、34℃),海水盐度为32,研究温度和规格对管角螺Hemifusustuba(Gelin)耗氧率和排氨率的影响。结果表明:14~29℃范围内,管角螺耗氧率随温度的升高,29℃时达到最大值;14~34℃范围内,排氨率随温度的升高而增加。在相同温度下,耗氧率和排氨率随单位软体部干重的增加而下降,管角螺软体部干重(W)与单位体重耗氧率(OR)、排氨率(NR)之间的关系分别符合幂函数方程OR=aW-b、NR=cW-d,W与OR、NR呈负相关关系。 相似文献
996.
N-(2-hydroxy-1-naphthaldene)-4-aminoantipyrine has been synthesized. The structure is determined by X-ray diffraction method and elemental analysis. The crystal system belongs to orthorhombic space group P(2)2(1)2(1). The geometry has been ob-tained from the density functional theory (DFT) method and the B3LYP method employing the 6-31G* basis sets. The calculated results propose that the latter is close to the experimental data. The structural parameters from the theory are close to those of the crystal and the calculated total energy of coordination is -31677.172 eV. The energy of HOMO and LUMO and the energy gap are 5.179 eV, -1.603 eV and 3.577 eV, respectively. 相似文献
997.
YOU Feng WANG Wei XU Dongdong ZHU Xiangping NI Jing WU Zhihao XU Yongli WANG Xincheng ZHANG Peijun 《中国海洋湖沼学报》2009,27(2)
The hybrid between olive flounder Paralichthys olivaceus and stone flounder Kareius bicoloratus was produced by artificial insemination of olive flounder eggs with stone flounder Sperm. Sinistral and dextral are two types of hybrid progeny after metamorphosis. Karyotypes of both hybrid flounders are the same as those of the two parental species. Of the 22 loci examined from 12 allozymes,12 confirmed hybridization of the paternal and matemal loci in hybrids and no difference was found in allozyme patterns of sinistral and dextral hybrid fishes. RAPD patterns of these specimens were also studied with 38 primers selected from 104 tested. Among them, the PCR products of 30 primers showed hybridization of the paternal and maternal bands. Genetic variation between hybrids and their parental stocks was analyzed by RAPD using 10 of the above 38 primers. The average heterozygosity and genetic distance were calculated. The results suggested that the filial generation could inherit a little more genetic materials from paternal fish than that from maternal fish. 相似文献
998.
Guoyan Ren Bafang Li Xue Zhao Yongliang Zhuang Mingyan Yan Hu Hou Xiukun Zhang Li Chen 《中国海洋大学学报(英文版)》2009,8(1):83-88
In order to select an optimum extraction method for the target glycoprotein (TGP) from jellyfish (Rhopilema esculentum) oral-arms, a high performance liquid chromatography (HPLC)-assay for the determination of the TGP was developed. Purified
target glycoprotein was taken as a standard glycoprotein. The results showed that the calibration curves for peak area plotted
against concentration for TGP were linear (r = 0.9984, y = 4.5895x+47.601) over concentrations ranging from 50 to 400 mgL-1. The mean extraction recovery was 97.84% (CV2.60%). The fractions
containing TGP were isolated from jellyfish (R. esculentum) oral-arms by four extraction methods: 1) water extraction (WE), 2) phosphate buffer solution (PBS) extraction (PE), 3) ultrasound-assisted
water extraction (UA-WE), 4) ultrasound-assisted PBS extraction (UA-PE). The lyophilized extract was dissolved in Milli-Q
water and analyzed directly on a short TSK-GEL G4000PWXL (7.8 mm×300 mm) column. Our results indicated that the UA-PE method
was the optimum extraction method selected by HPLC. 相似文献
999.
Black carbon and polycyclic aromatic hydrocarbons (PAHs) in surface sediments of China’s marginal seas 总被引:8,自引:0,他引:8
This study investigates the distribution of black carbon (BC) and its correlation with total polycyclic aromatic hydrocarbons (ΣPAH) in the surface sediments of China’s marginal seas. BC content ranges from <0.10 to 2.45 mg/g dw (grams dry weight) in the sediments studied, and varied among the different coastal regions. The Bohai Bay sediments had the highest BC contents (average 2.18 mg/g dw), which comprises a significant fraction (27%–41%) of the total organic carbon (TOC) preserved in the sediments. In ... 相似文献
1000.
Fish skin collagen hydrolysates (FSCH) were prepared from walleye pollock (Theragra chalcogramma) using a mixture of enzymes, namely trypsin and flavourzyme. The degree of hydrolysis of the skin collagen was 27.3%. FSCH
was mainly composed of low-molecular-weight peptides and the relative proportion of <1000Da fraction was 70.6%. Free radical
and oxygen species scavenging activities of FSCH were investigated in four model systems, including diphenylpicrylhy-drazyl
radical (DPPH), superoxide anion radical, hydroxyl radical and hydrogen peroxide model, and compared with that of a native
antioxidant, reduced glutathione (GSH). FSCH was also evaluated by water-absorbing and water-holding capacity. The results
showed that FSCH was able to scavenge free radical and oxygen species significantly and to enhance water-absorbing and water-holding
capacity remarkably. Therefore, FSCH may have potential applications in the medicine and food industries. 相似文献