全文获取类型
收费全文 | 25417篇 |
免费 | 234篇 |
国内免费 | 120篇 |
专业分类
安全科学 | 520篇 |
废物处理 | 1133篇 |
环保管理 | 3432篇 |
综合类 | 3827篇 |
基础理论 | 7512篇 |
环境理论 | 10篇 |
污染及防治 | 5855篇 |
评价与监测 | 1630篇 |
社会与环境 | 1720篇 |
灾害及防治 | 132篇 |
出版年
2021年 | 136篇 |
2019年 | 127篇 |
2018年 | 758篇 |
2017年 | 734篇 |
2016年 | 812篇 |
2015年 | 349篇 |
2014年 | 472篇 |
2013年 | 1598篇 |
2012年 | 758篇 |
2011年 | 1472篇 |
2010年 | 1059篇 |
2009年 | 1081篇 |
2008年 | 1390篇 |
2007年 | 1636篇 |
2006年 | 765篇 |
2005年 | 749篇 |
2004年 | 675篇 |
2003年 | 714篇 |
2002年 | 727篇 |
2001年 | 775篇 |
2000年 | 582篇 |
1999年 | 329篇 |
1998年 | 281篇 |
1997年 | 278篇 |
1996年 | 279篇 |
1995年 | 331篇 |
1994年 | 302篇 |
1993年 | 284篇 |
1992年 | 277篇 |
1991年 | 278篇 |
1990年 | 294篇 |
1989年 | 277篇 |
1988年 | 249篇 |
1987年 | 240篇 |
1986年 | 222篇 |
1985年 | 200篇 |
1984年 | 265篇 |
1983年 | 213篇 |
1982年 | 271篇 |
1981年 | 219篇 |
1980年 | 184篇 |
1979年 | 201篇 |
1978年 | 184篇 |
1977年 | 153篇 |
1976年 | 138篇 |
1975年 | 143篇 |
1974年 | 159篇 |
1973年 | 162篇 |
1972年 | 148篇 |
1971年 | 146篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
331.
Microorganisms (bacteria, fungi) are common residents of the roots, stems and leaves of higher plants. In order to explore the dependency of plant development on the presence of epiphytic microorganisms, the achenes (seeds) of sunflower (Helianthus annuus L.) were sterilized and germinated under aseptic conditions. The sterility of the seedlings was determined with the agar impression method. In seedlings from non-sterile seeds (control) that were likewise raised in a germ-free environment, all plant organs investigated (stem, cotyledons and primary leaves) were contaminated with bacteria. Hypocotyl elongation was not affected by epiphytic microorganisms. However, the growth rates of the cotyledons and primary leaves were higher in sterile seedlings compared with the control. The implications of this differential inhibition of organ development by epiphytic bacteria that are transmitted via the outer surface of the seed coat are discussed. We conclude that epiphytes in the above-ground phytosphere are not necessary for the development of the sunflower seedling. 相似文献
332.
333.
334.
A protocol for easy storage and later expansion of lymphocyte populations is given. Compared with methods using transformed cell lines, the method has a number of advantages for repeated production of cells for the isolation of DNA in amounts sufficient for use in diagnostic DNA technology. 相似文献
335.
336.
Self-diffusion coefficients were studied for the highly polar liquid N-methylformamide at pressures up to 200 MPa between the melting pressure curves and 420 K by the spin-echo method. N-Methylformamide exists as a mixture of two conformers in the neat liquid. These conformers have large differences at lower
temperatures in their dynamic and structural properties. The self-diffusion coefficient of the cis-conformer being 17% lower than that of the trans-conformer at the same T and p. This is the first observation of such an effect. The experimental study is supported by Monte Carlo (MC) calculations which
show that the first neighbors around a cis conformer are arranged differently than in an all trans liquid. The difference leads in the simulations to a much lower dielectric constant for the trans-cis mixture and might also explain the retardation of diffusion for the cis conformer.
Received: 15 November 1999 / Accepted in revised form: 28 February 2000 相似文献
337.
338.
339.
B. Sikkema-Raddatz R. H. Sijmons M. B. Tan-Sindhunata A. Y. Van Der Veen R. Brunsting B. De Vries J. R. Beekhuis D. J. Bekedam B. Van Aken B. De Jong 《黑龙江环境通报》1995,15(5):467-473
We report two cases of apparently balanced complex de novo chromosomal rearrangements (BCCR) detected prenatally at 17 weeks and 10 weeks of gestation, respectively. Chromosomes were studied using GTG-banding and fluorescent in situ hybridization (FISH). In one case four chromosomes and in the other case three chromosomes were involved in the rearrangements. One of the pregnancies was terminated and no external or internal abnormalities were detected at autopsy. The other pregnancy continued to term. Level III ultrasound examination showed no abnormalities. The child is now 3 years old and has neither congenital anomalies nor evidence of delayed psychomotor development. 相似文献
340.
Reverse phase HPLC of radioactive globin chains has been compared to classical carboxy methyl cellulose chromatography for the prenatal diagnosis of β thalassaemia. The two methods correlated highly (r = 0.97 p < 0.0005) and provided an identical diagnosis for 40 fetal blood samples of fetuses homozygous or heterozygous for β thalassaemia. The HPLC procedure was much faster and required fewer biochemical steps (no globin preparation). It was at least as accurate and more sensitive than the classical chromatography. A single column can be used for 150 analyses and is always ready to be used. Last but not least it is much less expensive than CMC chromatography. 相似文献