全文获取类型
收费全文 | 11256篇 |
免费 | 1050篇 |
国内免费 | 1775篇 |
专业分类
测绘学 | 384篇 |
大气科学 | 795篇 |
地球物理 | 1297篇 |
地质学 | 4067篇 |
海洋学 | 1209篇 |
天文学 | 5221篇 |
综合类 | 407篇 |
自然地理 | 701篇 |
出版年
2024年 | 31篇 |
2023年 | 70篇 |
2022年 | 226篇 |
2021年 | 229篇 |
2020年 | 263篇 |
2019年 | 344篇 |
2018年 | 263篇 |
2017年 | 282篇 |
2016年 | 309篇 |
2015年 | 346篇 |
2014年 | 562篇 |
2013年 | 627篇 |
2012年 | 639篇 |
2011年 | 786篇 |
2010年 | 781篇 |
2009年 | 1109篇 |
2008年 | 1034篇 |
2007年 | 931篇 |
2006年 | 836篇 |
2005年 | 745篇 |
2004年 | 592篇 |
2003年 | 506篇 |
2002年 | 422篇 |
2001年 | 375篇 |
2000年 | 337篇 |
1999年 | 319篇 |
1998年 | 234篇 |
1997年 | 114篇 |
1996年 | 110篇 |
1995年 | 88篇 |
1994年 | 89篇 |
1993年 | 96篇 |
1992年 | 54篇 |
1991年 | 55篇 |
1990年 | 46篇 |
1989年 | 43篇 |
1988年 | 30篇 |
1987年 | 12篇 |
1986年 | 18篇 |
1985年 | 22篇 |
1984年 | 19篇 |
1983年 | 18篇 |
1982年 | 19篇 |
1981年 | 6篇 |
1980年 | 14篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 16篇 |
1877年 | 1篇 |
1875年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
H. Jonsson K. Viken Sandnes D. Schiedek R. Schneider B. E. Grsvik A. Goksyr 《Marine environmental research》2004,58(2-5):655
In an attempt to learn more about the cytochrome P450 (CYP) system of mussels, we used protein databases and alignment software to extract highly conserved CYP sequences. From these alignments synthetic peptides were produced and used for rabbit immunisation, which yielded polyclonal antibodies against the CYP families 2 and 4. The antibodies were evaluated with Western Blot and ELISA assays, using digestive gland microsomal samples from the mussel Mytilus edulis. Western Blots revealed immunoreactions for both antibodies. The anti-CYP2 sequence rendered one major immunopositive protein of ≈49 kDa size, and weak signals for proteins of ≈41 and 56 kDa size. The anti-CYP4 sequence rendered two major bands of ≈56 and 59 kDa size, and also a weak immunoreaction with a protein of ≈43 kDa size. ELISA rendered only weak signals even with a 1:50 dilution of IgG-purified serum. A 10-day exposure to Aroclor 1254 did not appear to affect any of the immunopositive proteins, while total PCBs in soft bodies increased from 14–40 ng/g DW in controls to 373–638 ng/g DW in exposed mussels. 相似文献
162.
In this paper, we analyse the ability of the nonlinear shallow-water (NSW) equations to predict wave distortion and energy dissipation of periodic broken waves in the inner surf zone. This analysis is based on the weak-solution theory for conservative equations. We derive a new one-way model, which applies to the transformation of non-reflective periodic broken waves on gently sloping beaches. This model can be useful to develop breaking-wave parameterizations (in particular broken-wave celerity expression) in both time-averaged wave models and time-dependent Boussinesq-type models. We also derive a new wave set-up equation which provides a simple and explicit relation between wave set-up and energy dissipation. Finally, we compare numerical simulations of both, the NSW model and the simplified one-way model, with spilling wave breaking experiments and we find a good agreement. 相似文献
164.
165.
166.
167.
168.
169.
The Eastern Flank Hydrocarbon Province borders the southeastern edge of the South Oman Salt Basin in the southern part of Oman. An intensive exploration programme by PDO over the past seven years has led to the discovery of almost 2 × 109 m3 of oil with current production of some 15000 m3/d from six fields.In stark contrast to other oil habitats of the Arabian Peninsula, the main play involves rock units and geological events ranging in age from Late Precambrian to Quaternary Times, while trap development and charging are closely related to syn-tectonic salt dissolution.The principal reservoirs and seals are poorly consolidated, Palaeozoic clastics which drape, due to salt dissolution, over residual ‘cores’ principally composed of either Lower Palaeozoic sandstones (Haima Group), or Late Proterozoic carbonates (Huqf Group), or some combination of these. Oils have been geochemically correlated with algal source rocks of the Huqf Eastern Flank. Structures are considered to have been ‘charged’ from Late Mesozoic times onwards in conjunction with progressive subsurface salt removal and the onset of maturation of local source rocks. The effectiveness of ‘charging’ along the retreating salt edge is indicated by the small percentage of dry wells.Major oil zones are found in both anticlinal and truncation traps which are commonly developed around sandstone (Haima Group) cores. Oils show a wide range of characteristics but are typically heavy, early expulsion crudes, high sulphur with little associated gas. Bacterial transformation is not uncommon.Producing reservoirs mainly occur at relatively shallow depths (600–1200 m). Primary recovery factors of around 7% reflect the high density and viscosity of the Eastern Flank crudes and have initiated interest in Enhanced Oil Recovery (EOR) techniques. Two such pilot projects, involving steam and polymer flooding, are due to commence in 1984 and, if successful, will substantially increase the reserve base of these fields. 相似文献
170.
对单芯电缆传输这种通讯技术的原理进行了阐述;分析提出了部分电路、部件的技术指标;作为一种数据传输的手段,对单芯电缆传输技术在海洋专用CTD中的应用进行了相关论述. 相似文献