全文获取类型
收费全文 | 32819篇 |
免费 | 308篇 |
国内免费 | 246篇 |
专业分类
安全科学 | 810篇 |
废物处理 | 1272篇 |
环保管理 | 4023篇 |
综合类 | 6825篇 |
基础理论 | 8186篇 |
环境理论 | 17篇 |
污染及防治 | 8302篇 |
评价与监测 | 1983篇 |
社会与环境 | 1810篇 |
灾害及防治 | 145篇 |
出版年
2022年 | 231篇 |
2021年 | 255篇 |
2019年 | 258篇 |
2018年 | 463篇 |
2017年 | 451篇 |
2016年 | 687篇 |
2015年 | 520篇 |
2014年 | 738篇 |
2013年 | 2324篇 |
2012年 | 875篇 |
2011年 | 1314篇 |
2010年 | 1024篇 |
2009年 | 1086篇 |
2008年 | 1355篇 |
2007年 | 1405篇 |
2006年 | 1263篇 |
2005年 | 1026篇 |
2004年 | 1084篇 |
2003年 | 1016篇 |
2002年 | 981篇 |
2001年 | 1243篇 |
2000年 | 817篇 |
1999年 | 554篇 |
1998年 | 415篇 |
1997年 | 420篇 |
1996年 | 453篇 |
1995年 | 481篇 |
1994年 | 488篇 |
1993年 | 424篇 |
1992年 | 430篇 |
1991年 | 418篇 |
1990年 | 434篇 |
1989年 | 397篇 |
1988年 | 342篇 |
1987年 | 319篇 |
1986年 | 302篇 |
1985年 | 315篇 |
1984年 | 342篇 |
1983年 | 344篇 |
1982年 | 351篇 |
1981年 | 314篇 |
1980年 | 257篇 |
1979年 | 268篇 |
1978年 | 257篇 |
1977年 | 230篇 |
1976年 | 197篇 |
1975年 | 213篇 |
1974年 | 226篇 |
1973年 | 208篇 |
1972年 | 219篇 |
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
301.
Overestimates of black carbon in soils and sediments 总被引:2,自引:0,他引:2
Several recent reports suggest that black carbon (BC), which broadly encompasses charcoal, soot, and other forms of pyrogenic carbon, may constitute a significant proportion of the refractory carbon in soil and sedimentary organic matter. BC is a sink for biospheric and atmospheric carbon dioxide, and is intimately tied to the biogeochemical cycling of both carbon and oxygen through its role in organic matter cycling. Additionally, BC may represent a large fraction of the missing carbon sink in global carbon accounting. Here, we demonstrate that documented measurements of BC may be the result of methodological artifacts, which inadvertently overestimate the amount of BC. We found that a widely used thermal oxidative method can create a residue that falls under the operational definition of BC in samples that are relatively BC-free. Moreover, during this procedure, labile organic matter constituents are condensed into pyrogenic carbon, implying that the labile components are present in lesser quantities. These methodological deficiencies are promoting overestimates in the amount of refractory carbon in soil and sedimentary organic matter and may endorse inaccuracies in the rates of carbon fluxes, the mean residence times of terrestrial carbon, and organic matter burial rates in oceanic environments. 相似文献
302.
Mary C. Phelan Ph.D. Robert A. Saul Thompson A. Gailey Jr Steven A. Skinner 《黑龙江环境通报》1995,15(3):274-277
Mosaicism for the Wolf-Hirschhorn syndrome, del(4)(p16), is extremely rare and has not been reported in association with a numerical chromosome abnormality. We report the prenatal diagnosis of mosaic del(4)(p16) and non-mosaic trisomy 21 in a 16-week female fetus. The pregnancy ended in spontaneous abortion at 34 weeks secondary to fetal demise. The fetus had features of both 4p – and trisomy 21. 相似文献
303.
Stickler syndrome is an autosomal dominant disorder of the connective tissue which includes ocular and systemic manifestations. We report on a large kindred in which we were able to demonstrate very tight linkage between the disease and the type II collagen gene (COL2A1) (LOD score 3·91 at θ=0). In a family in which the father and one of his daughters were severely affected, DNA analysis from a chorionic villus sample demonstrated that the fetus possessed the normal allele of COL2A1. Thereafter a normal child was born. 相似文献
304.
As screening for Down syndrome becomes increasingly sophisticated, it is important to evaluate the newer technologies in terms of their cost-effectiveness. One recent addition to Down syndrome screening programmes is maternal serum unconjugated oestriol (uE3), especially when used in conjunction with maternal serum α-fetoprotein and human chorionic gonadotropin. Using assumptions used in a California proposal to justify an expanded screening programme for Down syndrome, we calculated both the average and the incremental cost-effectiveness of adding uE3. Using the base case assumptions, including an $8 fee for the uE3, the incremental cost-effectiveness of adding uE3 to the proposed California programme is $119 100 per case detected, a value that compares favourably with other Down syndrome screening programmes. The sensitivity analysis supports this conclusion over a wide range of assumptions. However, because of the uncertainty with some key data, it is still too early to fully support the inclusion of uE3 in Down syndrome screening programmes. 相似文献
305.
Ariel Weissman Reuwen Achiron M.D. Jacob Kuint Shlomo Lipitz Shlomo Mashiach Itamar Avigad 《黑龙江环境通报》1994,14(9):888-891
A case of gastric outlet obstruction diagnosed prenatally at 22 weeks' gestation is described. The differential diagnosis and the clinical management of this rare condition are discussed, and an updated literature review is presented. 相似文献
306.
Catherine Donner M.D. Corinne Liesnard Françoise Brancart Frederic Rodesch 《黑龙江环境通报》1994,14(11):1055-1059
Cytomegalovirus (CMV) is the most common cause of intrauterine infection. Recent publications show amniocentesis to have an 81–100 per cent sensitivity in antenatal diagnosis after 21 weeks' gestation. Testing before 21 weeks' gestation is less well documented. We performed 36 amniocenteses between 14 and 20 weeks' gestation. The sensitivity was 45 per cent and the specificity 100 per cent. Implications and possible causes of this low sensitivity are discussed. 相似文献
307.
Ellen Sidransky Susan H. Black Dawn M. Soenksen Shirley L. Jones Andrew D. Dorfmann Joseph D. Schulman MD 《黑龙江环境通报》1990,10(9):583-586
Chorionic villus sampling (CVS) with either transcervical catheters or transabdominal needles is a widely-accepted method for prenatal diagnosis. However, there exists a small subset of patients in whom sampling is difficult or impossible with either route because of individual anatomic variations. A new method of chorionic villus biopsy has been developed to circumvent these problems, utilizing transvaginal chorionic needle aspiration guided by an intravaginal ultrasound probe. This technique was performed successfully in 15 patients in whom villi could not be obtained by either of the conventional methods. This method now makes CVS possible in essentially all women regardless of their uterine anatomy or placental placement; it may also prove useful for very early chorionic sampling. 相似文献
308.
This paper reports results of an exploratory study of prenatal diagnosis patients who experienced voluntary terminations of pregnancy following the detection of an abnormality or spontaneous miscarriages. The 121 participants were part of the national collaborative Chorionic Villus Sampling and Amniocentesis Study. They completed semi-structured telephone interviews and mailed questionnaires at 1 month and 6 months after the pregnancy losses. Scores on the Profile of Mood States showed that mood levels improved significantly over time. However, there were some declines in loss-related support from partners and others. The persisting distress and difficulties of a minority highlight the variability in women's responses to pregnancy losses. Women who lost pregnancies later in gestation, showed the greatest mood disturbances at initial assessments, used professional mental health assistance after the loss, or reported less satisfactory loss-related support from significant others showed the greatest levels of mood disturbance at the six-month assessment. Follow-up contacts with patients who lose pregnancies should be used to inform women about the variation in possible grief reactions, to assess the extent of support the women are receiving from their partners and significant others, and to provide additional follow-up or referral of those experiencing the greatest distress. 相似文献
309.
Counselling in connection with prenatal diagnosis (PND) is a common task for the obstetrician and the midwife. However, the decision making processes of pregnant women are not completely known, for instance, the questions of women's autonomy, the decision on how to act in the case of an abnormal test, and the partner's participation in the decision. A questionnaire and interview study was carried out among 211 women undergoing PND by amniocentesis or chorionic villus biopsy. Most women in the sample indicated that PND was completely voluntary. However, at the same time almost every woman reported that it was difficult to decline from PND when offered. Even before the visit to register at the antenatal clinic, most of the women (83 per cent) had made up their minds to have PND. At the time of the test, many of the participants (62 per cent) had decided in favour of a legal abortion if the test indicated an abnormality in the fetus. At the same time, however, the data indicate a need for reflection and ambivalence, which the medical staff have to accept. In the questionnaire most of the women stated that they and their partners had similar attitudes towards PND, but when interviewed 38 per cent of the women admitted some differences between their own attitudes and their partners'. Although some women reported considerable deliberation and ambivalence, most of them said that they would undergo PND in another pregnancy. 相似文献
310.