全文获取类型
收费全文 | 24624篇 |
免费 | 316篇 |
国内免费 | 184篇 |
专业分类
安全科学 | 698篇 |
废物处理 | 1094篇 |
环保管理 | 3859篇 |
综合类 | 3728篇 |
基础理论 | 6715篇 |
环境理论 | 13篇 |
污染及防治 | 6268篇 |
评价与监测 | 1558篇 |
社会与环境 | 1013篇 |
灾害及防治 | 178篇 |
出版年
2021年 | 176篇 |
2019年 | 180篇 |
2018年 | 296篇 |
2017年 | 328篇 |
2016年 | 496篇 |
2015年 | 399篇 |
2014年 | 558篇 |
2013年 | 2070篇 |
2012年 | 725篇 |
2011年 | 1032篇 |
2010年 | 819篇 |
2009年 | 824篇 |
2008年 | 1035篇 |
2007年 | 1072篇 |
2006年 | 959篇 |
2005年 | 795篇 |
2004年 | 805篇 |
2003年 | 798篇 |
2002年 | 761篇 |
2001年 | 828篇 |
2000年 | 663篇 |
1999年 | 414篇 |
1998年 | 324篇 |
1997年 | 335篇 |
1996年 | 342篇 |
1995年 | 391篇 |
1994年 | 356篇 |
1993年 | 339篇 |
1992年 | 338篇 |
1991年 | 317篇 |
1990年 | 338篇 |
1989年 | 316篇 |
1988年 | 276篇 |
1987年 | 270篇 |
1986年 | 257篇 |
1985年 | 234篇 |
1984年 | 295篇 |
1983年 | 252篇 |
1982年 | 305篇 |
1981年 | 267篇 |
1980年 | 224篇 |
1979年 | 219篇 |
1978年 | 204篇 |
1977年 | 167篇 |
1976年 | 148篇 |
1975年 | 156篇 |
1974年 | 164篇 |
1973年 | 167篇 |
1972年 | 154篇 |
1971年 | 158篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
291.
Siegfried Rotmensch Marco Liberati Jia-Sen Luo Giovanni Tallin Maurice J. Mahoney John C. Hobbins 《黑龙江环境通报》1991,11(11):867-873
Many authors have suggested that individuals affected by a terminal 1q deletion display a phenotypically definable and recognizable syndrome. In all of the 27 cases reported to date, the breakpoints were at band q42 or distally to it. To our knowledge, we report the first case of a terminal 1q41 deletion. Diagnosis was made prenatally by amniocentesis, following ultrasonographic diagnosis of omphalocele, cerebral ventriculomegaly, and increased nuchal fold thickness in a 19-week female fetus. Multiple facial and extremity features were consistent with the proposed distal 1q deletion syndrome; omphalocele, however, has not been reported previously. The absence of liver herniation into the omphalocele sac in this case supports the previously reported association of this finding with chromosomal anomalies. 相似文献
292.
Aris Antsaklis John Politis Costas Karagiannopoulos Dionysios Kaskarelis Photini Karababa John Panourgias Marina Boussiou Dimitris Loukopoulos 《黑龙江环境通报》1984,4(4):289-296
Selective feticide is the procedure of choice when, in twin binovular pregnancy, only one of the fetuses is shown to be affected. As the probabilities for this condition are almost 1:2 when the genetic disease is due to homozygosity for two autosomal recessive genes, the problem is expected to occur frequently among the ever increasing number of couples seeking prenatal diagnosis of thalassaemia and the haemoglobinopathies. The present report is the first case of this condition and the ninth in the overall medical literature. 相似文献
293.
A survey is given on fluid-dynamic effects caused by the structure and properties of biological surfaces. It is demonstrated
that the results of investigations aiming at technological applications can also provide insights into biophysical phenomena.
Techniques are described both for reducing wall shear stresses and for controlling boundary-layer separation. (a) Wall shear
stress reduction was investigated experimentally for various riblet surfaces including a shark skin replica. The latter consists
of 800 plastic model scales with compliant anchoring. Hairy surfaces are also considered, and surfaces in which the no-slip
condition is modified. Self-cleaning surfaces such as that of lotus leaves represent an interesting option to avoid fluid-dynamic
deterioration by the agglomeration of dirt. An example of technological implementation is discussed for riblets in long-range
commercial aircraft. (b) Separation control is also an important issue in biology. After a few brief comments on vortex generators,
the mechanism of separation control by bird feathers is described in detail. Self-activated movable flaps (=artificial bird
feathers) represent a high-lift system enhancing the maximum lift of airfoils by about 20%. This is achieved without perceivable
deleterious effects under cruise conditions. Finally, flight experiments on an aircraft with laminar wing and movable flaps
are presented. 相似文献
294.
The main objective of this project was to evaluate the possibility of reducing the quantity of fibre wasted at one of many hydrocyclone (centrifugal) cleaning processes in a paper mill. It was found that the application of elutriation water to both the tertiary and quaternary cleaners was essential to minimise the fibre discharged to the sewer, and the pressure of this elutriation water had a dramatic effect of reducing the fibre wastage. Accordingly, it has been shown that 150–160 kPa as the optimum pressure range to apply elutriation water to minimise the product grade fibre wasted whilst sending undesired shive fibre to the sewer. Also, monitoring of the press uhle box wastewater revealed that the paper mill has the potential to make substantial cost savings by reducing the waste stream. Further investigation is necessary to determine the types of fibre that are being wasted, and the viability of a screen to recycle the wasted fibre to the process. However, these fibres may be unsuitable to reuse in the process and alternative uses must be found. 相似文献
295.
Three cases of unusual chromosomal mosaicism are reported for which the cytogenetic data show inconsistent findings between CVS and AC or fetal tissue, and which cannot be explained simply by non-disjunction. For case 1, in CVS the karyotype was 46,XY, whereas lymphocytes and fibroblasts revealed 69,XXY. DNA fingerprinting indicated one paternal and two maternal chromosome sets, the latter most probably due to omission of maternal meiosis II. For case 2, in CVS mos 46,XX/47,XX,+mar de novo was observed. Amniotic fluid cells had the karyotype 46,XX. The origin of the marker chromosome might be explained by at least two events of unknown order (a somatic chromosome/chromatid deletion and non-disjunction of the homologous chromosome). In case 3 (CVS: mos 46,XY/46,XY,19q+ de novo; amniotic fluid cells, lymphocytes, and fibroblasts: 46,XY), the surplus of chromosome material in 19q+ might be explained on the basis of a somatic translocation. The idea of a chimera is less convincing, as the mosaic finding is restricted to one tissue. Furthermore, there was no hint of a vanishing twin. Hitherto, no case of structural chromosome mosaicism in CVS has been reconfirmed in fetal tissues. 相似文献
296.
We describe a new method for the post-mortem examination of the fetal central nervous system. The brain is immobilized in gelatin prior to ultrasonic examination. Correlation with prenatal ultrasound is excellent and subsequent pathological examination is enhanced and facilitated. 相似文献
297.
298.
Diana W. Bianchi MD Gretchen K. Zickwolf Melissa C. Yih Alan F. Flint Ossie H. Geifman Marlena S. Erikson John M. Williams 《黑龙江环境通报》1993,13(4):293-300
Fetal nucleated erythrocytes (NRBC) in maternal blood are a non-invasive source of fetal DNA for prenatal genetic screening. We compared the effectiveness of three monoclonal antibodies for the separation of fetal cells from maternal blood by flow sorting. Mononuclear blood cells from 49 healthy pregnant women were incubated with antibody to CD 71, CD 36, and/or glycophorin A (GPA), employed singly or in combination with each other. These monoclonal antibodies recognize surface antigens on haematopoietic precursor cells. Successful isolation of fetal cells was defined as detection of Y chromosomal sequences in maternal blood from women carrying male fetuses, with absence of Y sequences when female fetuses were carried. Thus, gender prediction accuracy was used as a measure of fetal cell separation. Using anti-CD 71 to isolate fetal cells, gender prediction was 57 per cent correct; with anti-CD 36, it was 88 per cent correct. Anti-GPA, an erythrocyte-specific antigen, used alone or in combination with anti-CD 71 or 36, improved gender prediction to 100 per cent. We conclude that antibody to GPA improves the retrieval of fetal NRBC from maternal blood, permitting genetic analysis by the polymerase chain reaction. 相似文献
299.
Lee P. Shulman MD Patricia L. Gordon Donald S. Emerson R. Sidney Wilroy Sherman Elias 《黑龙江环境通报》1993,13(5):403-409
We describe the prenatal diagnosis of isolated bilateral fetal microphthalmia in a woman at increased risk of having a fetus with microphthalmia. Ultrasound examinations at 161 and 19-5 weeks' gestation demonstrated bilateral fetal microphthalmia with no other associated structural defects. The patient elected to terminate her pregnancy at 19.5 weeks. Pathological evaluation of the products of conception obtained by dilation and evacuation confirmed the prenatal diagnosis of isolated bilateral fetal microphthalmia. 相似文献
300.
Data from 2907 transcervical CVS cases performed on singleton pregnancies were reviewed retrospectively and villus sample size was correlated with cytogenetic results, placental location, maternal age at the expected date of confinement (EDC), gestational age at the time of sampling, birth weight, gestational age at the time of delivery, and pregnancy outcome. No correlation was noted between villus sample size and maternal age, gestational age at sampling, gestational age at delivery, birth weight, or pregnancy outcome. An inverse correlation between villus sample size and percentage of abnormal cytogenetic findings was statistically significant (X2 = 8·53, p <0·01). The percentage of small samples was greater when the placenta was anterior, lateral, or fundal than when the placenta was posterior. 相似文献