全文获取类型
收费全文 | 3904篇 |
免费 | 49篇 |
国内免费 | 174篇 |
专业分类
安全科学 | 110篇 |
废物处理 | 228篇 |
环保管理 | 385篇 |
综合类 | 654篇 |
基础理论 | 959篇 |
环境理论 | 2篇 |
污染及防治 | 1285篇 |
评价与监测 | 283篇 |
社会与环境 | 204篇 |
灾害及防治 | 17篇 |
出版年
2023年 | 23篇 |
2022年 | 75篇 |
2021年 | 45篇 |
2020年 | 31篇 |
2019年 | 45篇 |
2018年 | 130篇 |
2017年 | 75篇 |
2016年 | 100篇 |
2015年 | 101篇 |
2014年 | 101篇 |
2013年 | 331篇 |
2012年 | 103篇 |
2011年 | 181篇 |
2010年 | 153篇 |
2009年 | 174篇 |
2008年 | 193篇 |
2007年 | 221篇 |
2006年 | 158篇 |
2005年 | 139篇 |
2004年 | 164篇 |
2003年 | 153篇 |
2002年 | 128篇 |
2001年 | 256篇 |
2000年 | 154篇 |
1999年 | 79篇 |
1998年 | 46篇 |
1997年 | 55篇 |
1996年 | 44篇 |
1995年 | 50篇 |
1994年 | 54篇 |
1993年 | 49篇 |
1992年 | 35篇 |
1991年 | 38篇 |
1990年 | 34篇 |
1989年 | 37篇 |
1988年 | 30篇 |
1987年 | 24篇 |
1986年 | 24篇 |
1985年 | 20篇 |
1984年 | 26篇 |
1983年 | 26篇 |
1982年 | 25篇 |
1981年 | 18篇 |
1980年 | 16篇 |
1979年 | 18篇 |
1978年 | 16篇 |
1975年 | 12篇 |
1973年 | 12篇 |
1972年 | 15篇 |
1969年 | 11篇 |
排序方式: 共有4127条查询结果,搜索用时 31 毫秒
51.
In Hydra vulgaris at the level of dissociated single cells endodermal cells adhere to each other more readily than to ectodermal cells at the
initial adhesion. The time required for adhesion to occur between two adjacent cells is shorter for both endodermal and ectodermal
homotypic cell adhesions once the initial adhesion of the first pair of cells has been established. It is confirmed that contact
of an aggregated pair with additional homotypic cells facilitates the occurrence of homotypic adhesions; heterotypic adhesions
are discouraged. This suggests that adhesion of homotypic cells contributes to an increased readiness for subsequent homotypic
cells to adhere.
Received: 25 August 1999 / Accepted in revised form: 11 January 2000 相似文献
52.
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
53.
54.
55.
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
56.
A pleural effusion associated with congenital pulmonary lymphangiectasia was detected in a fetus in utero but was absent at the time of delivery. The pleural effusion was unilateral although the disease involved both lungs. In this case there was an association between polyhydramnios and congenital pulmonary lymphangiectasia. 相似文献
57.
在印度洋中部查戈斯礁群的大多数珊瑚死亡之后3年,对30m水深以浅珊瑚的侵蚀和恢复情况进行了研究.北部环礁15m水深以浅、中部和南部环礁>35m处的珊瑚差不多全部死亡.由于密集珊瑚丛的损失,一些礁体"表面"下降了1 5m.珊瑚的生物侵蚀情况严重,减少了三维礁体"结构"并形成松散的碎石.幼年珊瑚数量众多,尽管大部分是在侵蚀的或不稳定的基底上,并且稳定种较少.在15m的深度,礁体间鱼类丰度和多样性仍旧较高;依赖于珊瑚生存的物种减少,而一些食草动物和食碎屑动物则增加.一个新的海面温度(SST)数据集表明,平均SST自1950年以来升高了0.65℃.造成查戈斯珊瑚礁死亡的临界SST是29.9℃. 相似文献
58.
59.
A population of 1639 patients were seen for chorionic villus sampling (CVS). Embryonic death was identified at ultrasound in 5.3 per cent of patients. The number of patients undergoing CVS was 1551, with 1416 transcervical procedures and 135 transabdominal procedures. The most common indication for CVS was advanced maternal age. Spontaneous pregnancy losses identified by increased risk of pregnancy loss with increasing aspiration attempts. The total fetal loss for this population was 5.4 per cent with the pregnancy loss estimated due to procedure being 1.2 per cent. Analysis of placentae from patients having CVS and amniocen-tesis showed no differences. Microbiological assessment prior to CVS was similar to previous publications. 相似文献
60.