全文获取类型
收费全文 | 33726篇 |
免费 | 346篇 |
国内免费 | 253篇 |
专业分类
测绘学 | 1050篇 |
大气科学 | 2451篇 |
地球物理 | 6822篇 |
地质学 | 11045篇 |
海洋学 | 2897篇 |
天文学 | 8229篇 |
综合类 | 91篇 |
自然地理 | 1740篇 |
出版年
2021年 | 274篇 |
2020年 | 320篇 |
2019年 | 371篇 |
2018年 | 767篇 |
2017年 | 715篇 |
2016年 | 928篇 |
2015年 | 529篇 |
2014年 | 900篇 |
2013年 | 1629篇 |
2012年 | 1006篇 |
2011年 | 1288篇 |
2010年 | 1144篇 |
2009年 | 1639篇 |
2008年 | 1382篇 |
2007年 | 1443篇 |
2006年 | 1361篇 |
2005年 | 995篇 |
2004年 | 1035篇 |
2003年 | 956篇 |
2002年 | 978篇 |
2001年 | 902篇 |
2000年 | 827篇 |
1999年 | 735篇 |
1998年 | 684篇 |
1997年 | 698篇 |
1996年 | 552篇 |
1995年 | 534篇 |
1994年 | 504篇 |
1993年 | 430篇 |
1992年 | 375篇 |
1991年 | 396篇 |
1990年 | 382篇 |
1989年 | 376篇 |
1988年 | 347篇 |
1987年 | 395篇 |
1986年 | 362篇 |
1985年 | 423篇 |
1984年 | 549篇 |
1983年 | 455篇 |
1982年 | 461篇 |
1981年 | 399篇 |
1980年 | 349篇 |
1979年 | 350篇 |
1978年 | 356篇 |
1977年 | 312篇 |
1976年 | 279篇 |
1975年 | 298篇 |
1974年 | 255篇 |
1973年 | 284篇 |
1972年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
On the Polar-Wander Path for Australia during the Cenozoic 总被引:1,自引:0,他引:1
162.
P. Wagner 《International Journal of Earth Sciences》1933,24(3-4):240-240
Ohne Zusammenfassung 相似文献
163.
Study of the material composition of Fe-Mn crusts from submarine rises in the central part of the Sea of Japan, with modern
precision methods applied, has yielded a high (up to 854 g/t) concentration of gallium contained in sorbed form. The new data
obtained have allowed a new genetic type of gallium deposits—hydrothermal-sedimentary—to be distinguished. 相似文献
164.
Hashmi Fatima H. C. Upadhyaya S. N. Tripathi O. P. Sharma Fangqun Yu 《Meteorology and Atmospheric Physics》2011,112(3-4):101-115
A significant fraction of the total number of particles present in the atmosphere is formed by nucleation in the gas phase. Nucleation and the subsequent growth process influence both number concentration of particles and their size distribution besides chemical and optical properties of atmospheric aerosols. Sulphate aerosol nucleation mechanisms promoted by ions have been evaluated here in a tropospheric interactive chemistry-aerosol module for mass and number concentration in a global atmospheric model. The indirect radiative forcing of sulphate particles is assessed in this model; indirect radiative forcing is different for ion-induced (IIN) and ion-mediated (IMN) mechanisms. The indirect radiative forcing in 10-year simulation runs has been calculated as ?1.42?W/m2 (IIN) and ?1.54?W/m2 (IMN). The 5% emission of primary sulphate particles in simulations changes the indirect radiative forcing from ?1.42 to ?1.44?W/m2 for IIN case, and from ?1.54 to ?1.55 W/m2 for the IMN case. More precisely, owing to greater nucleation rates, IMN mechanisms produces greater cooling than the IIN mechanisms in the backdrop that both mechanisms produce almost identical distribution of CDNC in their pre-industrial runs. The inclusion of primary particles in simulations with IIN and IMN mechanisms increases both CDNC and the indirect radiative forcing. 相似文献
165.
E. G. Kalacheva S. N. Rychagov G. P. Koroleva A. A. Nuzhdaev 《Journal of Volcanology and Seismology》2016,10(3):188-202
New data are presented on the geochemistry of thermal waters in the Koshelev volcanic massif in southern Kamchatka. We discuss the conditions for the generation of thermal waters, possible variants of thermal and deep-seated material supply for the Koshelev hydrothermal system, and propose a conceptual model for the system. 相似文献
166.
167.
An intensive scheelite exploration program was carried out in Precambrian crystalline and sedimentary rocks intruded by granites of Precambrian and Caledonian ages in East Greenland (70–74°30′N). Previous heavy-mineral panning (2100 samples within an area of 100,000 km2) formed the basis for selection of scheelite-anomalous subregions (1550 km2)In the subregions, pan-concentrate samples were taken from first- and second-order rivers and from mid and side moraines of active glaciers. All samples were studied in the field under UV light, and scheelite grains were counted. A consideration of the distribution of scheelite in the samples together with the river and glacial drainage systems, led to definition of the potential source areas of the scheelite within localities of 2–5 km2.Within the localities, panning of scree fines (samples every 100–200 m along talus slopes) and UV-light traverses at night led to the finding of outcropping or sub-outcropping scheelite mineralisation. Scheelite was observed associated with granite-carbonate contact zones, quartz vein stockworks, and fault zones in limestones, at nine localities within the 300-km-long zone of investigation.The heavy-mineral panning method with the counting of scheelite grains in the field and the subsequent definition of potential scheelite-bearing areas has the advantage that it is possible to execute a program from the subregional to the outcropping mineralisation stage in one field season. The investigation in this case was performed by five geologists during the 1979 2.5-month field season. 相似文献
168.
169.
Detailed palaeomagnetic and rock magnetic analyses provide improved palaeomagnetic results from 23 sites in the Borgmassivet intrusions in the Ahlmannryggen region of Dronning Maud Land, East Antarctica. These intrusions are of similar age to their host, the ca. 1130 Ma Ritscherflya Supergroup (RSG). A mean direction of D=235.4°, I=−7.6° with k=45.9 and α95=4.5° was obtained from this study. When combined with previously reported results from 11 sites in the same region, including sites from the Ritscherflya Supergroup, it gives an overall mean direction for 34 sites from the igneous suite with D=236.5°, I=−3.6°, k=27.9 and α95=4.8°. Isothermal remanent magnetization (IRM) experiments on several specimens suggest magnetite or titanomagnetite as the primary remanence carrier, while high temperature magnetic susceptibility experiments indicate the presence of single domain particles. These observations, together with field evidence and the high coercivities and unblocking temperatures, support a primary origin for the observed characteristic remanence. The Borgmassivet palaeomagnetic pole lies at 54.5°E, 8.3°N with A95=3.3°. If Antarctica is moved to its Gondwanan position adjacent to southeast Africa, the Borgmassivet pole (BM) coincides with that of the African well-established, well-dated (1100 Ma) Umkondo Large Igneous Province pole, supporting the hypothesis that the Grunehogna craton of Dronning Maud Land was part of the Kalahari craton of southern Africa at ca. 1100 Ma. 相似文献
170.
J. L. Rosenberg P. G. Spry C. E. Jacobson N. J. Cook F. M. Vokes 《Mineralium Deposita》1998,34(1):19-34
The Bleikvassli massive sulfide ore deposit is hosted by Proterozoic pelitic, quartzofeldspathic, and amphibolitic rocks
of the Uppermost Allochthon of the Scandinavian Caledonides. Staurolite-garnet-biotite and kyanite-staurolite-biotite assemblages
indicate that metamorphism reached the kyanite zone of the amphibolite facies. Geothermobarometry was conducted on rocks in
and around the deposit using a variety of silicate and sulfide calibrations. Temperature determinations are most reliant on
the garnet-biotite exchange reaction, with analyses obtained from 259 garnet rims and adjacent biotite. Results from nine
calibrations of the garnet-biotite geothermometer are considered, but compositional limitations of many calibrations involving
high Ca and Mn contents in garnet and AlVI and Ti in biotite make many of the coexisting mineral pairs unsuitable. Average temperatures calculated from the two calibrations
that most closely address the garnet-biotite compositions observed at Bleikvassli are 584 °C ± 49 °C and 570 °C ± 40 °C. The
application of two calibrations of the garnet-staurolite geothermometer on a limited number of samples yields 581 °C ± 2 °C
and 589 °C ± 12 °C, assuming a
H2O=0.84, based upon calculations of the modal proportions of gaseous species. Pressure determinations are less constrained.
Phengite and plagioclase-biotite-garnet-muscovite geobarometers give average pressures of approximately 5.0 kbar and 8.5 ± 1.2 kbar,
respectively. Pressures obtained from the sphalerite-hexagonal pyrrhotite-pyrite barometer average 7.7 ± 1.0 kbar. In consideration
of these results, the peak metamorphic conditions at the Bleikvassli deposit are estimated to be 580 °C and 8 kbar.
Received: 18 June 1997 / Accepted: 14 May 1998 相似文献